Professor Mark Smales

Professor of Industrial Biotechnology
Director: Industrial Biotechnology Centre

About

Professor Mark Smales is Professor of Industrial Biotechnology in the School of Biosciences at the University of Kent. The group headed by Mark has a number of on-going projects whose objectives are to further advance our understanding of biotechnological products and processes at the fundamental biological or chemical level to enable their manipulation and control for improved (a) biotherapeutic recombinant protein yields and quality, (b) manufacture of gene therapies, (c) re-tuning of cell metabolism via synthetic biology approaches. His group in particular focusses upon the investigation of cultured mammalian cells for the purposes of producing biotherapeutic proteins for the treatment of disease, for the generation of diagnostics and for manufacturing of gene therapies. This includes upstream and downstream bioprocessing and embracing and utilising novel technologies such as genome editing to engineering cell systems and tune them for the desired use. A further aspect of his work is around mRNA translation and its control. He has a particular interest in how both initiation and elongation message specific control is achieved by the cell when under specific stresses, particularly in response to cold-shock.
Mark is Director of the Industrial Biotechnology Centre and a member of the Industrial Biotechnology and Synthetic Biology Research Group.
  
ORCID ID: 0000-0002-2762-4724

Research interests

Cell and metabolic engineering, therapeutic recombinant protein biotechnology, gene therapy, vaccine technology, control of mRNA translation 

The focus of the research in the laboratory is to work on aspects relating to improving our understanding of the biology that underpins bioprocessing and recombinant protein production from cell expression systems, particularly in vitro cultured mammalian expression systems. The laboratory is recognised internationally for its work using cultured mammalian cells for in vitro research purposes, particularly in relation to investigating the cellular constraints on recombinant protein productivity, control of mRNA translation, and ore recently its application to manufacturing of gene therapies and vaccines. The laboratory has extensive experience in gene expression analysis in mammalian cell systems, specifically recombinant gene expression, and is ideally placed with strong biotechnological and industrial links to exploit this technology. Currently the laboratory is funded via a number of BBSRC, EPSRC and industrial research grants and studentships. We are always interested in discussing potential projects and collaborations with academic and industrial colleagues. If you are interested, or wish to discuss graduate opportunities (Masters and PhD) or vacancies within the laboratory, please contact us.

Publications

Showing 50 of 88 total publications in the Kent Academic Repository. View all publications.

Article

  • Vito, D. and Smales, C. (2018). The Long Non-Coding RNA Transcriptome Landscape in CHO Cells Under Batch and Fed-Batch Conditions. Biotechnology Journal [Online] 13:1800122. Available at: https://doi.org/10.1002/biot.201800122.
    The role of non‐coding RNAs in determining growth, productivity and recombinant product quality attributes in Chinese hamster ovary (CHO) cells has received much attention in recent years, exemplified by studies into microRNAs in particular. However, other classes of non‐coding RNAs have received less attention. One such class are the non‐coding RNAs known collectively as long non‐coding RNAs (lncRNAs). We have undertaken the first landscape analysis of the lncRNA transcriptome in CHO using a mouse based microarray that also provided for the surveillance of the coding transcriptome. We report on those lncRNAs present in a model host CHO cell line under batch and fed‐batch conditions on two different days and relate the expression of different lncRNAs to each other. We demonstrate that the mouse microarray was suitable for the detection and analysis of thousands of CHO lncRNAs and validated a number of these by qRT‐PCR. We then further analysed the data to identify those lncRNAs whose expression changed the most between growth and stationary phases of culture or between batch and fed‐batch culture to identify potential lncRNA targets for further functional studies with regard to their role in controlling growth of CHO cells. We discuss the implications for the publication of this rich dataset and how this may be used by the community.
  • Jossé, L., Zhang, L. and Smales, C. (2018). Application of microRNA Targeted 3′UTRs to Repress DHFR Selection Marker Expression for Development of Recombinant Antibody Expressing CHO Cell Pools. Biotechnology Journal [Online] 13:1800129. Available at: https://doi.org/10.1002/biot.201800129.
    The dihydrofolate reductase (DHFR) system is used for the selection of recombinant Chinese hamster ovary (CHO) cell lines using the inhibitor methotrexate (MTX). During clonal selection, endogenous DHFR expression, and resistance to MTX allows the selection of cells expressing sufficient DHFR to survive. Here, the authors describe a novel vector platform for the DHFR system, whereby addition of a synthetic 3′UTR destabilizes DHFR expression. miRs ability to negatively regulate gene expression by their near‐complementary binding to the 3′UTR region of transcripts are harnessed. From the literature, the authors identified let‐7f as a highly abundant, invariant miR in CHO cells. Three 3′UTR targets of the let‐7f miR are then cloned in the DHFR host 3′UTR to determine the impact on gene expression (HMGA2 3′UTR sequence 1, 2, and 3). Using luciferase as a reporter, the authors show down‐regulation of luciferase activity is mediated by the nature of the 3′UTR and its ability to bind let‐7f. The same 3′UTRs downstream of the DHFR gene to show this also results in reduced transcript amounts are then applied. Finally, the authors applied this methodology to generate stable DG44‐derived cell pools expressing a model monoclonal antibody (mAb), demonstrating this approach can be used for the selection of antibody‐producing cells with low MTX concentrations.
  • Gourbatsi, E., Povey, J. and Smales, C. (2018). The effect of formulation variables on protein stability and integrity of a model IgG4 monoclonal antibody and translation to formulation of a model ScFv. Biotechnology Letters [Online] 40:33-46. Available at: http://dx.doi.org/10.1007/s10529-017-2443-x.
    Objectives: There are a number of blockbuster monoclonal antibodies on the market used for the treatment of a variety of diseases. Although the formulation of many antibodies is achieved in ‘platform’ formulations, some are so difficult to formulate that it can result in an inability to develop a finished drug product. Further, a large number of antibody-inspired or-based molecules are now being developed and assessed for biotherapeutic purposes and less is understood around the required active protein drug concentrations, excipients and additives required in final product formulations.
    Results: We investigated the effect of formulation variables (pH, buffer composition, glycine and NaCl concentration, time and temperature of accelerated stability studies) on antibody solubility/aggregation and activity using a Plackett–Burman Experimental Design approach. We then used the findings from this study and applied these to the formulation of a single chain variable fragment (ScFv) molecule. Our data shows that prediction of ScFc stability from a model monoclonal antibody could be achieved although further formulation optimization was required. Mass spectrometry analysis confirmed changes to the mass and hence authenticity of both the model antibody and ScFv under formulation conditions that did not provide appropriate conditions for protection of the molecules.
    Conclusions: The role of the different formulation conditions on maintaining protein integrity is described and using mass spectrometry shows that protein integrity is compromised under particular conditions. The implications for predicting successful formulations for protein molecules is discussed and how antibody formulations could be used to predict formulation components for novel antibody based molecules.
  • Tamošaitis, L. and Smales, M. (2018). Meta-analysis of publicly available Chinese hamster ovary (CHO) cell transcriptomic datasets for identifying engineering targets to enhance recombinant protein yields. Biotechnology Journal [Online] 13:1800066. Available at: https://doi.org/10.1002/biot.201800066.
    Transcriptomics has been extensively applied to the investigation of the CHO cell platform for
    the production of recombinant biotherapeutic proteins to identify transcripts whose expression
    is regulated and correlated to (non)desirable CHO cell attributes. However, there have been
    few attempts to analyse the findings across these studies to identify conserved changes and
    generic targets for CHO cell platform engineering. Here we have undertaken a meta-analysis
    of CHO cell transcriptomic data and report on those genes most frequently identified as
    differentially expressed with regard to cell growth (μ) and productivity (Qp). By aggregating
    differentially expressed genes from publicly available transcriptomic datasets associated with
    μ and Qp, using a pathway enrichment analysis and combining it with the concordance of
    gene expression values, we have identified a refined target gene and pathway list whilst
    determining the overlap across CHO transcriptomic studies. We find that only the cell cycle
    and lysosome pathways show good concordance. By mapping out the contributing genes we
    have constructed a transcriptomic ‘fingerprint’ of a high-performing cell line. This study
    provides a starting resource for researchers who want to navigate the complex landscape of
    CHO transcriptomics and identify targets to undertake cell engineering for improved
    recombinant protein output.
  • Saintas, E. et al. (2017). Acquired resistance to oxaliplatin is not directly associated with increased resistance to DNA damage in SK-N-ASrOXALI4000, a newly established oxaliplatin-resistant sub-line of the neuroblastoma cell line SK-N-AS. PLoS ONE [Online] 12:e0172140. Available at: http://dx.doi.org/10.1371/journal.pone.0172140.
    The formation of acquired drug resistance is a major reason for the failure of anti-cancer therapies after initial response. Here, we introduce a novel model of acquired oxaliplatin resistance, a sub-line of the non-MYCN-amplified neuroblastoma cell line SK-N-AS that was adapted to growth in the presence of 4000 ng/mL oxaliplatin (SK-N-ASrOXALI4000). SK-N-ASrOXALI4000 cells displayed enhanced chromosomal aberrations compared to SK-N-AS, as indicated by 24-chromosome fluorescence in situ hybridisation. Moreover, SK-N-ASrOXALI4000 cells were resistant not only to oxaliplatin but also to the two other commonly used anti-cancer platinum agents cisplatin and carboplatin. SK-N-ASrOXALI4000 cells exhibited a stable resistance phenotype that was not affected by culturing the cells for 10 weeks in the absence of oxaliplatin. Interestingly, SK-N-ASrOXALI4000 cells showed no cross resistance to gemcitabine and increased sensitivity to doxorubicin and UVC radiation, alternative treatments that like platinum drugs target DNA integrity. Notably, UVC-induced DNA damage is thought to be predominantly repaired by nucleotide excision repair and nucleotide excision repair has been described as the main oxaliplatin-induced DNA damage repair system. SK-N-ASrOXALI4000 cells were also more sensitive to lysis by influenza A virus, a candidate for oncolytic therapy, than SK-N-AS cells. In conclusion, we introduce a novel oxaliplatin resistance model. The oxaliplatin resistance mechanisms in SK-N-ASrOXALI4000 cells appear to be complex and not to directly depend on enhanced DNA repair capacity. Models of oxaliplatin resistance are of particular relevance since research on platinum drugs has so far predominantly focused on cisplatin and carboplatin.
  • Godfrey, C. et al. (2017). Polysome Profiling of mAb Producing CHO Cell Lines Links Translational Control of Cell Proliferation and Recombinant mRNA Loading onto Ribosomes with Global and Recombinant Protein Synthesis. Biotechnology Journal [Online] 12:1700177. Available at: http://dx.doi.org/10.1002/biot.201700177.
    mRNA translation is a key process determining growth, proliferation and duration of a Chinese hamster ovary (CHO) cell culture and influences recombinant protein synthesis rate. During bioprocessing, CHO cells can experience stresses leading to reprogramming of translation and decreased global protein synthesis. Here we apply polysome profiling to determine reprogramming and translational capabilities in host and recombinant monoclonal antibody-producing (mAb) CHO cell lines during batch culture. Recombinant cell lines with the fastest cell specific growth rates were those with the highest global translational efficiency. However, total ribosomal capacity, determined from polysome profiles, did not relate to the fastest growing or highest producing mAb cell line, suggesting it is the ability to utilise available machinery that determines protein synthetic capacity. Cell lines with higher cell specific productivities tended to have elevated recombinant heavy chain transcript copy numbers, localised to the translationally active heavy polysomes. The highest titre cell line was that which sustained recombinant protein synthesis and maintained high recombinant transcript copy numbers in polysomes. Investigation of specific endogenous transcripts revealed a number that maintained or reprogrammed into heavy polysomes, identifying targets for potential cell engineering or those with 5′ untranslated regions that might be utilised to enhance recombinant transcript translation.
  • Migani, D., Smales, C. and Bracewell, D. (2017). Effects of lysosomal biotherapeutic recombinant protein expression on cell stress and protease and general host cell protein (HCP) release in Chinese hamster ovary cells. Biotechnology Progress [Online] 33:666-676. Available at: http://dx.doi.org/10.1002/btpr.2455.
    Recombinant human Acid Alpha Glucosidase (GAA) is the therapeutic enzyme used for the treatment of Pompe disease, a rare genetic disorder characterized by GAA deficiency in the cell lysosomes (Raben et al., Curr Mol Med. 2002; 2:145–166). The manufacturing process for GAA can be challenging, in part due to protease degradation. The overall goal of this study was to understand the effects of GAA overexpression on cell lysosomal phenotype and host cell protein (HCP) release, and any resultant consequences for protease levels and ease of manufacture. To do this we first generated a human recombinant GAA producing stable CHO cell line and designed the capture chromatographic step anion exchange (IEX). We then collected images of cell lysosomes via transmission electron microscopy (TEM) and compared the resulting data with that from a null CHO cell line. TEM imaging revealed 72% of all lysosomes in the GAA cell line were engorged indicating extensive cell stress; by comparison only 8% of lysosomes in the null CHO had a similar phenotype. Furthermore, comparison of the HCP profile among cell lines (GAA, mAb, and Null) capture eluates, showed that while most HCPs released were common across them, some were unique to the GAA producer, implying that cell stress caused by overexpression of GAA has a molecule specific effect on HCP release. Protease analysis via zymograms showed an overall reduction in proteolytic activity after the capture step but also revealed the presence of co-eluting proteases at approximately 80 KDa, which MS analysis putatively identified as dipeptidyl peptidase 3 and prolyl endopeptidase.
  • Almeida, A. et al. (2017). Investigations into, and development of, a lyophilized and formulated recombinant human factor IX produced from CHO cells. Biotechnology Letters [Online] 39:1109-1120. Available at: http://dx.doi.org/10.1007/s10529-017-2353-y.
    Objectives: To develop a recombinant human factor IX (rFIX) formulation equivalent to commercially available products in terms of cake appearance, residual moisture, proportion of soluble aggregates and activity maintenance for 3 months at 4–8 °C.
    Results: NaCl and low bulking agent/cryoprotectant mass ratio had a negative impact on cake quality upon lyophilisation for a wide range of formulations tested. Particular devised formulations maintained rFIX activity after lyophilization with a similar performance when compared with the rFIX formulated using the excipients reported for a commercially available FIX formulation (Benefix). rFIX remained active after 3 months when stored at 4 °C, though this was not the case with samples stored at 40 °C. Interestingly, particular formulations had an increase in residual moisture after 3 months storage, but not above a 3% threshold. All four formulations tested were equivalent to the Benefix formulation in terms of particle size distribution and cake appearance.
    Conclusions: Three specific formulations, consisting of surfactant polysorbate-80, sucrose or trehalose as cryoprotectant, mannitol or glycine as bulking agent, l-histidine as buffering agent, and NaCl added in the reconstitution liquid at 0.234% (w/v) were suitable for use with a CHO cell-derived recombinant FIX.
  • Bastide, A. et al. (2017). RTN3 Is a Novel Cold-Induced Protein and Mediates Neuroprotective Effects of RBM3. Current Biology [Online] 27:638-650. Available at: https://doi.org/10.1016/j.cub.2017.01.047.
    Cooling and hypothermia are profoundly neuroprotective, mediated, at least in part, by the cold shock protein, RBM3. However, the neuroprotective effector proteins induced by RBM3 and the mechanisms by which mRNAs encoding cold shock proteins escape cooling-induced translational repression are unknown. Here, we show that cooling induces reprogramming of the translatome, including the upregulation of a new cold shock protein, RTN3, a reticulon protein implicated in synapse formation. We report that this has two mechanistic components. Thus, RTN3 both evades cooling-induced translational elongation repression and is also bound by RBM3, which drives the increased expression of RTN3. In mice, knockdown of RTN3 expression eliminated cooling-induced neuroprotection. However, lentivirally mediated RTN3 overexpression prevented synaptic loss and cognitive deficits in a mouse model of neurodegeneration, downstream and independently of RBM3. We conclude that RTN3 expression is a mediator of RBM3-induced neuroprotection, controlled by novel mechanisms of escape from translational inhibition on cooling.
  • Vasilev, N. et al. (2016). Developments in the production of mucosal antibodies in plants. Biotechnology Advances [Online] 34:77-87. Available at: http://doi.org/10.1016/j.biotechadv.2015.11.002.
    Recombinant mucosal antibodies represent attractive target molecules for the development of next generation biopharmaceuticals for passive immunization against various infectious diseases and treatment of patients suffering from mucosal antibody deficiencies. As these polymeric antibodies require complex post-translational modifications and correct subunit assembly, they are considered as difficult-to-produce recombinant proteins. Beside the traditional, mammalian-based production platforms, plants are emerging as alternative expression hosts for this type of complex macromolecule. Plant cells are able to produce high-quality mucosal antibodies as shownby the successful expression of the secretory immunoglobulins A (IgA) andM(IgM) in various antibody formats in different plant species including tobacco and its close relative Nicotiana benthamiana, maize, tomato
    and Arabidopsis thaliana. Importantly for biotherapeutic application, transgenic plants are capable of synthesizing functional IgA and IgM molecules with biological activity and safety profiles comparable with their native mammalian counterparts. This article reviews the structure and function of mucosal IgA and IgM antibodies and summarizes
    the current knowledge of their production and processing in plant host systems. Specific emphasis is given to consideration of intracellular transport processes as these affect assembly of the mature immunoglobulins, their secretion rates, proteolysis/degradation and glycosylation patterns. Furthermore, this review provides an outline of glycoengineering efforts that have been undertaken so far to produce antibodies with homogenous human-like glycan decoration.Webelieve that the continued development of our understanding of the plant cellular machinery related to the heterologous expression of immunoglobulins will further improve the production levels, quality and control of post-translational modifications that are ‘human-like’ from plant systems and enhance the prospects for the regulatory approval of such molecules leading to the commercial exploitation of plant-derived mucosal antibodies.
  • Josse, L. et al. (2016). mTORC1 signalling and eIF4E/4E-BP1 translation initiation factor stoichiometry influence recombinant protein productivity from GS-CHOK1 cells. Biochemical Journal [Online] 473:4651-4664. Available at: http://doi.org/10.1042/BCJ20160845.
    Many protein-based biotherapeutics are produced in cultured Chinese hamster ovary (CHO) cell lines. Recent reports have demonstrated that translation of recombinant mRNAs and global control of the translation machinery via mammalian target of rapamycin (mTOR) signalling are important determinants of the amount and quality of recombinant protein such cells can produce. mTOR complex 1 (mTORC1) is a master regulator of cell growth/division, ribosome biogenesis and protein synthesis, but the relationship between mTORC1 signalling, cell growth and proliferation and recombinant protein yields from mammalian cells, and whether this master regulating signalling pathway can be manipulated to enhance cell biomass and recombinant protein production (rPP) are not well explored. We have investigated mTORC1 signalling and activity throughout batch culture of a panel of sister recombinant glutamine synthetase-CHO cell lines expressing different amounts of a model monoclonal IgG4, to evaluate the links between mTORC1 signalling and cell proliferation, autophagy, recombinant protein expression, global protein synthesis and mRNA translation initiation. We find that the expression of the mTORC1 substrate 4E-binding protein 1 (4E-BP1) fluctuates throughout the course of cell culture and, as expected, that the 4E-BP1 phosphorylation profiles change across the culture. Importantly, we find that the eIF4E/4E-BP1 stoichiometry positively correlates with cell productivity. Furthermore, eIF4E amounts appear to be co-regulated with 4E-BP1 amounts. This may reflect a sensing of either change at the mRNA level as opposed to the protein level or the fact that the phosphorylation status, as well as the amount of 4E-BP1 present, is important in the co-regulation of eIF4E and 4E-BP1.
  • Knight, J. et al. (2016). Cooling-induced SUMOylation of EXOSC10 down-regulates ribosome biogenesis. RNA [Online] 22:623-635. Available at: http://doi.org/10.1261/rna.054411.115.
    The RNA exosome is essential for 3′ processing of functional RNA species and degradation of aberrant RNAs in eukaryotic cells. Recent reports have defined the substrates of the exosome catalytic domains and solved the multimeric structure of the exosome complex. However, regulation of exosome activity remains poorly characterized, especially in response to physiological stress. Following the observation that cooling of mammalian cells results in a reduction in 40S:60S ribosomal subunit ratio, we uncover regulation of the nuclear exosome as a result of reduced temperature. Using human cells and an in vivo model system allowing whole-body cooling, we observe reduced EXOSC10 (hRrp6, Pm/Scl-100) expression in the cold. In parallel, both models of cooling increase global SUMOylation, leading to the identification of specific conjugation of SUMO1 to EXOSC10, a process that is increased by cooling. Furthermore, we define the major SUMOylation sites in EXOSC10 by mutagenesis and show that overexpression of SUMO1 alone is sufficient to suppress EXOSC10 abundance. Reducing EXOSC10 expression by RNAi in human cells correlates with the 3′ preribosomal RNA processing defects seen in the cold as well as reducing the 40S:60S ratio, a previously uncharacterized consequence of EXOSC10 suppression. Together, this work illustrates that EXOSC10 can be modified by SUMOylation and identifies a physiological stress where this regulation is prevalent both in vitro and in vivo.
  • Williams, M. et al. (2016). Microwave-assisted synthesis of highly crystalline, multifunctional iron oxide nanocomposites for imaging applications. RSC Advances [Online] 6:83520-83528. Available at: http://doi.org/10.1039/c6ra11819d.
    We report a reproducible single-step, microwave-assisted approach for the preparation of multifunctional magnetic nanocomposites comprising superparamagnetic iron oxide (Fe3O4) cores, a polyelectrolyte stabilizer and an organic dye with no requirement for post-processing. The stabilisers poly(sodium 4-styrenesulfonate) (PSSS) and sodium polyphosphate (SPP) have been thoroughly investigated and from analysis using electron microscopy, dynamic light scattering measurements, magnetic hysteresis and magnetic resonance (MR) imaging, we show that the higher degree of Fe3O4 nanoparticle crystallinity achieved with the PSSS stabiliser leads to enhanced magnetic behaviour and thus better contrast agent relaxivity compared to the less crystalline, poorly defined particles obtained when SPP is employed as a stabiliser. We also demonstrate the potential for obtaining a multifunctional magnetic-fluorescent nanocomposite using our microwave-assisted synthesis. In this manner, we demonstrate the intimate link between synthetic methodology (microwave heating with a polyelectrolyte stabilizer) and the resulting properties (particle size, shape, and magnetism) and how this underpins the functionality of the resulting nanocomposites as agents for biomedical imaging.
  • Gourbatsi, E. et al. (2016). Biotherapeutic protein formulation variables influence protein integrity and can promote post-translational modifications as shown using chicken egg white lysozyme as a model system. Biotechnology Letters [Online] 38:589-596. Available at: http://doi.org/10.1007/s10529-015-2014-y.
    Objectives
    The effect of different formulations variables on protein integrity were investigated using lysozyme as a model protein for the development of biotherapeutic protein formulations for use in the clinic.
    Results
    Buffer composition/concentration was the key variable of formulation reagents investigated in determining lysozyme stability and authenticity independent of protein concentration whilst the storage temperature and time, not surprisingly, were also key variables. Tryptic peptide mapping of the protein showed that the modifications occurred when formulated under specific conditions but not others. A model peptide system was developed that reflected the same behavior under formulation conditions as intact lysozyme.
    Conclusions
    Peptide models may mirror the stability of proteins, or regions of proteins, in the same formulations and be used to help develop a rapid screen of formulations for stabilisation of biotherapeutic proteins.
  • Lintern, K. et al. (2016). Residual on column host cell protein analysis during lifetime studies of protein A chromatography. Journal of Chromatography A [Online] 1461:70-77. Available at: http://doi.org/10.1016/j.chroma.2016.07.055.
    Capacity reduction in protein A affinity chromatography with extended cycling during therapeutic antibody manufacture is well documented. Identification of which residual proteins remain from previous cycles during the lifetime of these adsorbent materials is required to understand their role in this ageing process, but represents a significant metrological challenge. Scanning electron microscopy (SEM) and liquid chromatography mass spectrometry (LC–MS/MS) are combined to detect and map this phenomenon of protein carry-over. We show that there is a morphological change at the surface of the agarose resin, revealing deposits on the polymer fibres increasing with cycle number. The amount of residual host cell proteins (HCPs) by LC–MS/MS present on the resin is shown to increase 10-fold between 50 and 100 cycles. During this same period the functional class of the predominant HCPs associated with the resin increased in diversity, with number of proteins identified increasing 5-fold. This ageing is observed in the context of the product quality of the eluate HCP and protein A leachate concentration remaining constant with cycle number.
  • Feary, M. et al. (2016). Methionine sulfoximine supplementation enhances productivity in GS-CHOK1SV cell lines through glutathione biosynthesis. Biotechnology Progress [Online] 33:17-25. Available at: http://dx.doi.org/10.1002/btpr.2372.
    In Lonza Biologics' GS Gene Expression System™, recombinant protein-producing GS-CHOK1SV cell lines are generated by transfection with an expression vector encoding both GS and the protein product genes followed by selection in MSX and glutamine-free medium. MSX is required to inhibit endogenous CHOK1SV GS, and in effect create a glutamine auxotrophy in the host that can be complemented by the expression vector encoded GS in selected cell lines. However, MSX is not a specific inhibitor of GS as it also inhibits the activity of GCL (a key enzyme in the glutathione biosynthesis pathway) to a similar extent. Glutathione species (GSH and GSSG) have been shown to provide both oxidizing and reducing equivalents to ER-resident oxidoreductases, raising the possibility that selection for transfectants with increased GCL expression could result in the isolation of GS-CHOKISV cell lines with improved capacity for recombinant protein production. In this study we have begun to address the relationship between MSX supplementation, the amount of intracellular GCL subunit and mAb production from a panel of GS-CHOK1SV cell lines. We then evaluated the influence of reduced GCL activity on batch culture of an industrially relevant mAb-producing GS-CHOK1SV cell line. To the best of our knowledge, this paper describes for the first time the change in expression of GCL subunits and recombinant mAb production in these cell lines with the degree of MSX supplementation in routine subculture. Our data also shows that partial inhibition of GCL activity in medium containing 75 µM MSX increases mAb productivity, and its more specific inhibitor BSO used at a concentration of 80 µM in medium increases the specific rate of mAb production eight-fold and the concentration in harvest medium by two-fold. These findings support a link between the inhibition of glutathione biosynthesis and recombinant protein production in industrially relevant systems and provide a process-driven method for increasing mAb productivity from GS-CHOK1SV cell lines.
  • Chiverton, L. et al. (2016). Quantitative definition and monitoring of the host cell protein proteome using iTRAQ: a study of an industrial mAb producing CHO-S cell line. Biotechnology Journal [Online] 11:1014-1024. Available at: http://doi.org/10.1002/biot.201500550.
    There are few studies defining CHO host cell proteins (HCPs) and the flux of these throughout a downstream purification process. Here we have applied quantitative iTRAQ proteomics to follow the HCP profile of an antibody (mAb) producing CHO-S cell line throughout a standard downstream purification procedure consisting of a Protein A, cation and anion exchange process. We used both 6 sample iTRAQ experiment to analyze technical replicates of three samples, which were culture harvest (HCCF), Protein A flow through and Protein A eluate and an 8 sample format to analyze technical replicates of four sample types; HCCF compared to Protein A eluate and subsequent cation and anion exchange purification. In the 6 sample iTRAQ experiment, 8781 spectra were confidently matched to peptides from 819 proteins (including the mAb chains). Across both the 6 and 8 sample experiments 936 proteins were identified. In the 8 sample comparison, 4187 spectra were confidently matched to peptides from 219 proteins. We then used the iTRAQ data to enable estimation of the relative change of individual proteins across the purification steps. These data provide the basis for application of iTRAQ for process development based upon knowledge of critical HCPs.
  • Roobol, A. et al. (2015). p58(IPK) is an Inhibitor of the eIF2α Kinase GCN2 and its Localisation and Expression Underpin Protein Synthesis and ER Processing Capacity. Biochemical Journal [Online] 465:213-225. Available at: http://dx.doi.org/10.1042/BJ20140852.
  • Jardim, A. et al. (2015). Expression of Trypanosoma brucei gambiense Antigens in Leishmania tarentolae. Potential for Use in Rapid Serodiagnostic Tests (RDTs). PLOS Neglected Tropical Diseases [Online] 9. Available at: http://doi.org/10.1371/journal.pntd.0004271.
    The development of rapid serodiagnostic tests for sleeping sickness and other diseases caused by kinetoplastids relies on the affordable production of parasite-specific recombinant antigens. Here, we describe the production of recombinant antigens from Trypanosoma brucei gambiense (T.b. gambiense) in the related species Leishmania tarentolae (L. tarentolae), and compare their diagnostic sensitivity and specificity to native antigens currently used in diagnostic kits against a panel of human sera. A number of T.b. gambiense protein antigen candidates were chosen for recombinant expression in L. tarentolae based on current diagnostics in field use and recent findings on immunodiagnostic antigens found by proteomic profiling. In particular, the extracellular domains of invariant surface glycoprotein 65 (ISG65), variant surface glycoproteins VSG LiTat 1.3 and VSG LiTat 1.5 were fused with C-terminal histidine tags and expressed as soluble proteins in the medium of cultured, recombinant L. tarentolae. Using affinity chromatography, on average 10 mg/L of recombinant protein was purified from cultures and subsequently tested against a panel of sera from sleeping sickness patients from controls, i.e. persons without sleeping sickness living in HAT endemic countries. The evaluation on sera from 172 T.b. gambiense human African trypanosomiasis (HAT) patients and from 119 controls showed very high diagnostic potential of the two recombinant VSG and the rISG65 fragments with areas under the curve between 0.97 and 0.98 compared to 0.98 and 0.99 with native VSG LiTat 1.3 and VSG LiTat 1.5 (statistically not different). Evaluation on sera from 78 T.b. rhodesiense HAT patients and from 100 controls showed an acceptable diagnostic potential of rISG65 with an area under the curve of 0.83. These results indicate that a combination of these recombinant antigens has the potential to be used in next generation rapid serodiagnostic tests. In addition, the L. tarentolae expression system enables simple, cheap and efficient production of recombinant kinetoplatid proteins for use in diagnostic, vaccine and drug discovery research that does not rely on animal use to generate materials.
  • Mead, E. et al. (2015). Biological Insights into the Expression of Translation Initiation Factors from Recombinant CHOK1SV Cell Lines and their Relationship to Enhanced Productivity. Biochemical Journal [Online] 472:261-273. Available at: http://dx.doi.org/10.1042/BJ20150928.
    Translation initiation is on the critical pathway for the production of monoclonal antibodies (mAb) by mammalian cells. Formation of a closed loop structure comprised of mRNA, a number of eukaryotic initiation factors and ribosomal proteins has been proposed to aid re-initiation of translation and therefore increase global translational efficiency. We have determined mRNA and protein levels of the key components of the closed loop; eukaryotic initiation factors (eIF3a, eIF3b, eIF3c, eIF3h, eIF3i and eIF4G1), poly(A) binding protein (PABP) 1 and PABP interacting protein 1 (PAIP1) across a panel of 30 recombinant mAb-producing GS-CHOK1SV cell lines with a broad range of growth characteristics and production levels of a model recombinant mAb. We have used a multi-level statistical approach to investigate the relationship between key performance indicators (cell growth and recombinant antibody productivity) and the intracellular amounts of target translation initiation factor proteins and the mRNAs encoding them. We show that high-producing cell lines maintain amounts of the translation initiation factors involved in the formation of the closed loop mRNA, maintaining these proteins at appropriate levels to deliver enhanced recombinant protein production. We then utilise knowledge of the amounts of these factors to build predictive models for, and use cluster analysis to identify, high-producing cell lines. This study therefore defines the translation initiation factor amounts that are associated with highly productive recombinant GS-CHOK1SV cell lines that may be targets for screening highly productive cell lines or to engineer new host cell lines with the potential for enhanced recombinant antibody productivity.
  • Knight, J. et al. (2015). Eukaryotic elongation factor 2 kinase regulates the cold stress response by slowing translation elongation. Biochemical Journal [Online] 465:227-238. Available at: http://dx.doi.org/10.1042/BJ20141014.
  • Hogwood, C. et al. (2015). An ultra scale-down approach identifies host cell protein differences across a panel of mAb producing CHO cell line variants. Biotechnology Journal [Online] 11:415-424. Available at: http://doi.org/10.1002/biot.201500010.
    During the manufacture of biopharmaceutical products, the final product must lie within strict pre-set specifications, for example the host cell protein (HCP) content. A number of specific HCPs have been identified in particular products and the interactions between product/HCPs have also been recently investigated; however, a comparison of the HCP dynamics between related cell lines and their response to early downstream processing to aid process development and cell line selection has not been published. We have utilised a proteomic approach coupled with an ultra scale-down study to determine the HCP profile dynamics, at harvest and during early downstream processing, across a panel of recombinant GS-CHOK1SV antibody producing cell lines. The results reveal that cell culture viability upon harvest has the greatest impact upon shear sensitivity and HCP concentration. Whilst the general HCP population/profile was broadly similar across the cell lines, the actual amounts of some specific HCPs in the supernatant differed and a number of cell line specific differences in the response to early downstream processing were observed. We anticipate that such knowledge can now be applied to cell line selection and downstream processing development to target reduction/removal of general and specific problematic HCPs before and during downstream processing.
  • Bracewell, D., Francis, R. and Smales, C. (2015). The future of host cell protein (HCP) identification during process development and manufacturing linked to a risk-based management for their control. Biotechnology and Bioengineering [Online] 112:1727-1737. Available at: http://doi.org/10.1002/bit.25628.
    The use of biological systems to synthesize complex therapeutic products has been a remarkable success. However, during product development, great attention must be devoted to defining acceptable levels of impurities that derive from that biological system, heading this list are host cell proteins (HCPs). Recent advances in proteomic analytics have shown how diverse this class of impurities is; as such knowledge and capability grows inevitable questions have arisen about how thorough current approaches to measuring HCPs are. The fundamental issue is how to adequately measure (and in turn monitor and control) such a large number of protein species (potentially thousands of components) to ensure safe and efficacious products. A rather elegant solution is to use an immunoassay (enzyme-linked immunosorbent assay [ELISA]) based on polyclonal antibodies raised to the host cell (biological system) used to synthesize a particular therapeutic product. However, the measurement is entirely dependent on the antibody serum used, which dictates the sensitivity of the assay and the degree of coverage of the HCP spectrum. It provides one summed analog value for HCP amount; a positive if all HCP components can be considered equal, a negative in the more likely event one associates greater risk with certain components of the HCP proteome. In a thorough risk-based approach, one would wish to be able to account for this. These issues have led to the investigation of orthogonal analytical methods; most prominently mass spectrometry. These techniques can potentially both identify and quantify HCPs. The ability to measure and monitor thousands of proteins proportionally increases the amount of data acquired. Significant benefits exist if the information can be used to determine critical HCPs and thereby create an improved basis for risk management. We describe a nascent approach to risk assessment of HCPs based upon such data, drawing attention to timeliness in relation to biosimilar initiatives. The development of such an approach requires databases based on cumulative knowledge of multiple risk factors that would require national and international regulators, standards authorities (e.g., NIST and NIBSC), industry and academia to all be involved in shaping what is the best approach to the adoption of the latest bioanalytical technology to this area, which is vital to delivering safe efficacious biological medicines of all types.
  • Tunjung, W. et al. (2015). Anti-Cancer Effect of Kaffir Lime (Citrus Hystrix DC) Leaf Extract in Cervical Cancer and Neuroblastoma Cell Lines. Procedia Chemistry [Online] 14:465-468. Available at: http://doi.org/10.1016/j.proche.2015.03.062.
    Previous study showed that kaffir lime leaf contains alkaloid, flavonoid, terpenoid, tannin and saponin. The objective of this study was to examine the cytotoxic effect of kaffir lime leaf extract on cervical cancer and neuroblastoma cell lines. The method used for this research to determine cell viability was an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Results showed that an ethyl acetate extract had an IC50 for HeLa cells, UKF-NB3, IMR-5 and SK-N-AS parental cells of 40.7 μg · mL–1, 28.4 μg · mL–1, 14.1 μg · mL–1, and 25.2 μg · mL–1 respectively. Furthermore, the IC50 of chloroform extracts for HeLa cells, UKF-NB3, IMR-5 and SK-N-AS parental were 17.6 μg · mL–1, 18.9 μg · mL–1, 6.4 μg · mL–1, and 9.4 μg · mL–1 respectively. These data showed that kaffir lime extract reduces the viability of cervical and neuroblastoma cell lines and may have potential as anti-cancer compounds.
  • Mead, E. et al. (2014). Control and regulation of mRNA translation. Biochemical Society transactions [Online] 42:151-154. Available at: http://dx.doi.org/10.1042/BST20130259.
    Translational control is central to the gene expression pathway and was the focus of the 2013 annual Translation UK meeting held at the University of Kent. The meeting brought together scientists at all career stages to present and discuss research in the mRNA translation field, with an emphasis on the presentations on the research of early career scientists. The diverse nature of this field was represented by the broad range of papers presented at the meeting. The complexity of mRNA translation and its control is emphasized by the interdisciplinary research approaches required to address this area with speakers highlighting emerging systems biology techniques and their application to understanding mRNA translation and the network of pathways controlling it.
  • Hogwood, C., Bracewell, D. and Smales, C. (2014). Measurement and control of host cell proteins (HCPs) in CHO cell bioprocesses. Current Opinion in Biotechnology [Online] 30:153-160. Available at: http://dx.doi.org/10.1016/j.copbio.2014.06.017.
    Chinese hamster ovary (CHO) cells are widely used for the production of biotherapeutic recombinant proteins for a range of molecules including monoclonal antibodies and Fc-fusion proteins. Regulatory requirements for the final product include the removal of host cell proteins (HCPs) to acceptable amounts (<100 ppm). Recent research has begun to unravel the extent to which upstream process conditions and subsequent product recovery and purification processes impact upon the HCP profile. A number of upstream parameters, including the selection of the cell line, the culturing process (e.g. feeding regime, culture temperature), cell viability at time of harvest/culture duration and cell shear sensitivity can all influence the resulting HCP profile. Further, the molecule itself plays an important role in determining those HCPs that are retained throughout a bioprocess and HCPs can co-elute with the target product during purification. Measurement and monitoring of HCPs is usually undertaken using ELISA technology, however alternative approaches are also now emerging that complement ELISA and allow the detection, identification and monitoring of specific HCPs. Here we discuss our understanding of how the process itself influences those HCPs present throughout the production process and the challenges in their monitoring, measurement and removal.
  • Roobol, A. et al. (2014). The chaperonin CCT interacts with and mediates the correct folding and activity of three subunits of translation initiation factor eIF3: b, i and h. Biochemical Journal [Online] 458:213-224. Available at: http://dx.doi.org/10.1042/BJ20130979.
    eIF3 (eukaryotic initiation factor 3) is the largest and most complex eukaryotic mRNA translation factor in terms of the number of protein components or subunits. In mammals, eIF3 is composed of 13 different polypeptide subunits, of which five, i.e. a, b, c, g and i, are conserved and essential in vivo from yeasts to mammals. In the present study, we show that the eukaryotic cytosolic chaperonin CCT [chaperonin containing TCP-1 (tailless complex polypeptide 1)] binds to newly synthesized eIF3b and promotes the correct folding of eIF3h and eIF3i. Interestingly, overexpression of these last two subunits is associated with enhanced translation of specific mRNAs over and above the general enhancement of global translation. In agreement with this, our data show that, as CCT is required for the correct folding of eIF3h and eIF3i subunits, it indirectly influences gene expression with eIF3i overexpression enhancing both cap- and IRES (internal ribosome entry segment)-dependent translation initiation, whereas eIF3h overexpression selectively increases IRES-dependent translation initiation. Importantly, these studies demonstrate the requirement of the chaperonin machinery for the correct folding of essential components of the translational machinery and provide further evidence of the close interplay between the cell environment, cell signalling, cell proliferation, the chaperone machinery and translational apparatus.
  • Ashton, L. et al. (2014). UV resonance Raman spectroscopy: a process analytical tool for host cell DNA and RNA dynamics in mammalian cell lines. Journal of Chemical Technology and Biotechnology [Online] 90:237-243. Available at: http://dx.doi.org/10.1002/jctb.4420.
  • Masterton, R. and Smales, C. (2014). The impact of process temperature on mammalian cell lines and the implications for the production of recombinant proteins in CHO cells. Pharmaceutical Bioprocessing [Online] 2:49-61. Available at: http://dx.doi.org/10.4155/pbp.14.3.
  • Povey, J. et al. (2014). Rapid high-throughput characterisation, classification and selection of recombinant mammalian cell line phenotypes using intact cell MALDI-ToF mass spectrometry fingerprinting and PLS-DA modelling. Journal of Biotechnology [Online] 184:84-93. Available at: http://dx.doi.org/10.1016/j.jbiotec.2014.04.028.
    Despite many advances in the generation of high producing recombinant mammalian cell lines over the last few decades, cell line selection and development is often slowed by the inability to predict a cell line's phenotypic characteristics (e.g. growth or recombinant protein productivity) at larger scale (large volume bioreactors) using data from early cell line construction at small culture scale. Here we describe the development of an intact cell MALDI-ToF mass spectrometry fingerprinting method for mammalian cells early in the cell line construction process whereby the resulting mass spectrometry data are used to predict the phenotype of mammalian cell lines at larger culture scale using a Partial Least Squares Discriminant Analysis (PLS-DA) model. Using MALDI-ToF mass spectrometry, a library of mass spectrometry fingerprints was generated for individual cell lines at the 96 deep well plate stage of cell line development. The growth and productivity of these cell lines were evaluated in a 10 L bioreactor model of Lonza's large-scale (up to 20,000 L) fed-batch cell culture processes. Using the mass spectrometry information at the 96 deep well plate stage and phenotype information at the 10 L bioreactor scale a PLS-DA model was developed to predict the productivity of unknown cell lines at the 10 L scale based upon their MALDI-ToF fingerprint at the 96 deep well plate scale. This approach provides the basis for the very early prediction of cell lines’ performance in cGMP manufacturing-scale bioreactors and the foundation for methods and models for predicting other mammalian cell phenotypes from rapid, intact-cell mass spectrometry based measurements.
  • Hogwood, C. et al. (2013). The dynamics of the CHO host cell protein profile during clarification and protein A capture in a platform antibody purification process. Biotechnology and Bioengineering [Online] 110:240-251. Available at: http://dx.doi.org/10.1002/bit.24607.
    Recombinant protein products such as monoclonal antibodies (mAbs) for use in the clinic must be clear of host cell impurities such as host cell protein (HCP), DNA/RNA, and high molecular weight immunogenic aggregates. Despite the need to remove and monitor HCPs, the nature, and fate of these during downstream processing (DSP) remains poorly characterized. We have applied a proteomic approach to investigate the dynamics and fate of HCPs in the supernatant of a mAb producing cell line during early DSP including centrifugation, depth filtration, and protein A capture chromatography. The primary clarification technique selected was shown to influence the HCP profile that entered subsequent downstream steps. MabSelect protein A chromatography removed the majority of contaminating proteins, however using 2D-PAGE we could visualize not only the antibody species in the eluate (heavy and light chain) but also contaminant HCPs. These data showed that the choice of secondary clarification impacts upon the HCP profile post-protein A chromatography as differences arose in both the presence and abundance of specific HCPs when depth filters were compared. A number of intracellularly located HCPs were identified in protein A elution fractions from a Null cell line culture supernatant including the chaperone Bip/GRP78, heat shock proteins, and the enzyme enolase. We demonstrate that the selection of early DSP steps influences the resulting HCP profile and that 2D-PAGE can be used for monitoring and identification of HCPs post-protein A chromatography. This approach could be used to screen cell lines or hosts to select those with reduced HCP profiles, or to identify HCPs that are problematic and difficult to remove so that cell-engineering approaches can be applied to reduced, or eliminate, such HCPs. Biotechnol. Bioeng. 2013; 110: 240–251.
  • Hogwood, C., Bracewell, D. and Smales, C. (2013). Host cell protein dynamics in recombinant CHO cells. Bioengineered [Online] 4:288-291. Available at: https://doi.org/10.4161/bioe.23382.
    During the production of recombinant protein products, such as monoclonal antibodies, manufacturers must demonstrate clearance of host cell impurities and contaminants to appropriate levels prior to use in the clinic. These include host cell DNA and RNA, product related contaminants such as aggregates, and importantly host cell proteins (HCPs). Despite the importance of HCP removal, the identity and dynamics of these proteins during cell culture and downstream processing (DSP) are largely unknown. Improvements in technologies such as SELDI-TOF mass spectrometry alongside the gold standard technique of ELISA has allowed semi-quantification of the total HCPs present. However, only recently have techniques been utilized in order to identify those HCPs present and align this with the development of approaches to monitor the dynamics of HCPs during both fermentation and downstream processing. In order to enable knowledge based decisions with regards to improving HCP clearance it is vital to identify potential problematic HCPs on a cell line and product specific basis. Understanding the HCP dynamics will in the future help provide a platform to rationally manipulate and engineer and/or select suitable recombinant CHO cell lines and downstream processing steps to limit problematic HCPs.
  • Wagstaff, J. et al. (2013). 1H NMR Spectroscopy Profiling of Metabolic Reprogramming of Chinese Hamster Ovary Cells upon a Temperature Shift during Culture. PLoS ONE 8:e77195-e77195.
    We report an NMR based approach to determine the metabolic reprogramming of Chinese hamster ovary cells upon
    a temperature shift during culture by investigating the extracellular cell culture media and intracellular metabolome of
    CHOK1 and CHO-S cells during culture and in response to cold-shock and subsequent recovery from hypothermic
    culturing. A total of 24 components were identified for CHOK1 and 29 components identified for CHO-S cell systems
    including the observation that CHO-S media contains 5.6 times the level of glucose of CHOK1 media at time zero.
    We confirm that an NMR metabolic approach provides quantitative analysis of components such as glucose and
    alanine with both cell lines responding in a similar manner and comparable to previously reported data. However,
    analysis of lactate confirms a differentiation between CHOK1 and CHO-S and that reprogramming of metabolism in
    response to temperature was cell line specific. The significance of our results is presented using principal component
    analysis (PCA) that confirms changes in metabolite profile in response to temperature and recovery. Ultimately, our
    approach demonstrates the capability of NMR providing real-time analysis to detect reprogramming of metabolism
    upon cellular perception of cold-shock/sub-physiological temperatures. This has the potential to allow manipulation of
    metabolites in culture supernatant to improve growth or productivity.
  • Al-Fageeh, M. and Smales, C. (2013). Alternative Promoters Regulate Cold Inducible RNA-Binding (CIRP) Gene Expression and Enhance Transgene Expression in Mammalian Cells. Molecular Biotechnology [Online] 54:238-249. Available at: http://dx.doi.org/10.1007/s12033-013-9649-5.
    The use of a temperature shift cultivation to enhance recombinant protein yield is widely utilised in the bioprocessing industry. The responses of mammalian cells to heat stress are well characterized; however, the equivalent cold stress responses are not. In particular, the transcriptional mechanisms that lead to enhanced gene-specific expression upon cold stress have yet to be elucidated. We report here in silico and experimental identification and characterization of transcriptional control elements that regulate cold inducible RNA-binding (CIRP) gene expression and demonstrate these can be used for enhanced transgene expression. In silico analysis identified the core CIRP promoter and a number of conserved transcription factor-binding sites across mammalian species. The core promoter was confirmed by experimental studies that located the basal transcriptional regulatory elements of CIRP within 264 nucleotides upstream of the transcription start site. Deletion analysis of a fragment from -264 to -64 that contained two putative CAAT-binding sites abolished promoter activity. A second promoter was identified in the region -452 to -264 of the transcription start site which was able to drive transcription independent of the core promoter. As the two CIRP promoters were transcriptionally active and possibly cold responsive, we used electrophoretic mobility shift assays to show that both promoter regions are able to bind factors within a nuclear extract in a dose-dependent manner and that the formation of these complexes was specific to the promoter regions. Finally, we successfully demonstrate using a reporter gene approach that enhanced transgene expression can be achieved using the identified CIRP promoter.
  • Bracewell, D. and Smales, C. (2013). The challenges of product- and process-related impurities to an evolving biopharmaceutical industry. Bioanalysis [Online] 5:123-126. Available at: http://dx.doi.org/10.4155/bio.12.314.
  • Peters, S. et al. (2012). Engineering an Improved IgG4 Molecule with Reduced Disulfide Bond Heterogeneity and Increased Fab Domain Thermal Stability. Journal of Biological Chemistry [Online] 287:24525-24533. Available at: http://dx.doi.org/10.1074/jbc.M112.369744.
    The integrity of antibody structure, stability, and biophysical characterization are becoming increasingly important as antibodies receive increasing scrutiny from regulatory authorities. We altered the disulfide bond arrangement of an IgG4 molecule by mutation of the Cys at the N terminus of the heavy chain constant domain 1 (CH1) (Kabat position 127) to a Ser and introduction of a Cys at a variety of positions (positions 227–230) at the C terminus of CH1. An inter-LC-CH1 disulfide bond is thus formed, which mimics the disulfide bond arrangement found in an IgG1 molecule. The antibody species present in the supernatant following transient expression in Chinese hamster ovary cells were analyzed by immunoblot to investigate product homogeneity, and purified product was analyzed by a thermofluor assay to determine thermal stability. We show that the light chain can form an inter-LC-CH1 disulfide bond with a Cys when present at several positions on the upper hinge (positions 227–230) and that such engineered disulfide bonds can consequently increase the Fab domain thermal stability between 3 and 6.8 °C. The IgG4 disulfide mutants displaying the greatest increase in Fab thermal stability were also the most homogeneous in terms of disulfide bond arrangement and antibody species present. Importantly, mutations did not affect the affinity for antigen of the resultant molecules. In combination with the previously described S241P mutation, we present an IgG4 molecule with increased Fab thermal stability and reduced product heterogeneity that potentially offers advantages for the production of IgG4 molecules.
  • Mead, E. et al. (2012). Experimental and In Silico Modelling Analyses of the Gene Expression Pathway for Recombinant Antibody and By-Product Production in NS0 Cell Lines. PLoS ONE [Online] 7:e47422. Available at: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0047422.
    Monoclonal antibodies are commercially important, high value biotherapeutic drugs used in the treatment of a variety of diseases. These complex molecules consist of two heavy chain and two light chain polypeptides covalently linked by disulphide bonds. They are usually expressed as recombinant proteins from cultured mammalian cells, which are capable of correctly modifying, folding and assembling the polypeptide chains into the native quaternary structure. Such recombinant cell lines often vary in the amounts of product produced and in the heterogeneity of the secreted products. The biological mechanisms of this variation are not fully defined. Here we have utilised experimental and modelling strategies to characterise and define the biology underpinning product heterogeneity in cell lines exhibiting varying antibody expression levels, and then experimentally validated these models. In undertaking these studies we applied and validated biochemical (rate-constant based) and engineering (nonlinear) models of antibody expression to experimental data from four NS0 cell lines with different IgG4 secretion rates. The models predict that export of the full antibody and its fragments are intrinsically linked, and cannot therefore be manipulated individually at the level of the secretory machinery. Instead, the models highlight strategies for the manipulation at the precursor species level to increase recombinant protein yields in both high and low producing cell lines. The models also highlight cell line specific limitations in the antibody expression pathway.
  • Hayes, N. et al. (2011). Modulation of Phosducin-Like Protein 3 (PhLP3) Levels Promotes Cytoskeletal Remodelling in a MAPK and RhoA-Dependent Manner. PLoS ONE [Online] 6:e28271. Available at: http://dx.doi.org/10.1371/journal.pone.0028271.
    Background
    Phosducin-like protein 3 (PhLP3) forms a ternary complex with the ATP-dependent molecular chaperone CCT and its folding client tubulin. In vitro studies suggest PhLP3 plays an inhibitory role in β-tubulin folding while conversely in vivo genetic studies suggest PhLP3 is required for the correct folding of β-tubulin. We have a particular interest in the cytoskeleton, its chaperones and their role in determining cellular phenotypes associated with high level recombinant protein expression from mammalian cell expression systems.

    Methodology/Principal Findings
    As studies into PhLP3 function have been largely carried out in non mammalian systems, we examined the effect of human PhLP3 over-expression and siRNA silencing using a single murine siRNA on both tubulin and actin systems in mammalian Chinese hamster ovary (CHO) cell lines. We show that over-expression of PhLP3 promotes an imbalance of α and β tubulin subunits, microtubule disassembly and cell death. In contrast, β-actin levels are not obviously perturbed. On-the-other-hand, RNA silencing of PhLP3 increases RhoA-dependent actin filament formation and focal adhesion formation and promotes a dramatic elongated fibroblast-like change in morphology. This was accompanied by an increase in phosphorylated MAPK which has been associated with promoting focal adhesion assembly and maturation. Transient overexpression of PhLP3 in knockdown experiments rescues cells from the morphological change observed during PhLP3 silencing but mitosis is perturbed, probably reflecting a tipping back of the balance of PhLP3 levels towards the overexpression state.

    Conclusions
    Our results support the hypothesis that PhLP3 is important for the maintenance of β-tubulin levels in mammalian cells but also that its modulation can promote actin-based cytoskeletal remodelling by a mechanism linked with MAPK phosphorylation and RhoA-dependent changes. PhLP3 levels in mammalian cells are thus finely poised and represents a novel target for engineering industrially relevant cell lines to evolve lines more suited to suspension or adherent cell growth.
  • Tait, A. et al. (2011). Host cell protein dynamics in the supernatant of a mAb producing CHO cell line. Biotechnology and Bioengineering [Online] 109:971-982. Available at: http://dx.doi.org/10.1002/bit.24383.
    The characterization of host cell protein (HCP) content during the production of therapeutic recombinant proteins is an important aspect in the drug development process. Despite this, key components of the HCP profile and how this changes with processing has not been fully investigated. Here we have investigated the supernatant HCP profile at different times throughout culture of a null and model GS-CHO monoclonal antibody producing mammalian cell line grown in fed-batch mode. Using 2D-PAGE and LC-MS/MS we identify a number of intracellular proteins (e.g., protein disulfide isomerise; elongation factor 2; calreticulin) that show a significant change in abundance relative to the general increase in HCP concentration observed with progression of culture. Those HCPs that showed a significant change in abundance across the culture above the general increase were dependent on the cell line examined. Further, our data suggests that the majority of HCPs in the supernatant of the cell lines investigated here arise through lysis or breakage of cells, associated with loss in viability, and are not present due to the secretion of protein material from within the cell. SELDI-TOF and principal components analysis were also investigated to enable rapid monitoring of changes in the HCP profile. SELDI-TOF analysis showed the same trends in the HCP profile as observed by 2D-PAGE analysis and highlighted biomarkers that could be used for process monitoring. These data further our understanding of the relationship between the HCP profile and cell viability and may ultimately enable a more directed development of purification strategies and the development of cell lines based upon their HCP profile.
  • Roobol, A. et al. (2011). ATR (ataxia telangiectasia mutated- and Rad3-related kinase) is activated by mild hypothermia in mammalian cells and subsequently activates p53. Biochemical Journal [Online] 435:499-508. Available at: http://dx.doi.org/10.1042/BJ20101303.
    In vitro cultured mammalian cells respond to mild hypothermia (27–33 °C) by attenuating cellular processes and slowing and arresting the cell cycle. The slowing of the cell cycle at the upper range (31–33 °C) and its complete arrest at the lower range (27–28 °C) of mild hypothermia is effected by the activation of p53 and subsequent expression of p21. However, the mechanism by which cold is perceived in mammalian cells with the subsequent activation of p53 has remained undetermined. In the present paper, we report that the exposure of Chinese-hamster ovary-K1 cells to mildly hypothermic conditions activates the ATR (ataxia telangiectasia mutated- and Rad3-related kinase)–p53–p21 signalling pathway and is thus a key pathway involved in p53 activation upon mild hypothermia. In addition, we show that although p38MAPK (p38 mitogen-activated protein kinase) is also involved in activation of p53 upon mild hypothermia, this is probably the result of activation of p38MAPK by ATR. Furthermore, we show that cold-induced changes in cell membrane lipid composition are correlated with the activation of the ATR–p53–p21 pathway. Therefore we provide the first mechanistic detail of cell sensing and signalling upon mild hypothermia in mammalian cells leading to p53 and p21 activation, which is known to lead to cell cycle arrest.
  • Kotov, N. et al. (2011). Computational modelling elucidates the mechanism of ciliary regulation in health and disease. BMC Systems Biology [Online] 5:143. Available at: http://dx.doi.org/10.1186/1752-0509-5-143.
    Background
    Ciliary dysfunction leads to a number of human pathologies, including primary ciliary dyskinesia, nephronophthisis, situs inversus pathology or infertility. The mechanism of cilia beating regulation is complex and despite extensive experimental characterization remains poorly understood. We develop a detailed systems model for calcium, membrane potential and cyclic nucleotide-dependent ciliary motility regulation.

    Results
    The model describes the intimate relationship between calcium and potassium ionic concentrations inside and outside of cilia with membrane voltage and, for the first time, describes a novel type of ciliary excitability which plays the major role in ciliary movement regulation. Our model describes a mechanism that allows ciliary excitation to be robust over a wide physiological range of extracellular ionic concentrations. The model predicts the existence of several dynamic modes of ciliary regulation, such as the generation of intraciliary Ca2+ spike with amplitude proportional to the degree of membrane depolarization, the ability to maintain stable oscillations, monostable multivibrator regimes, all of which are initiated by variability in ionic concentrations that translate into altered membrane voltage.

    Conclusions
    Computational investigation of the model offers several new insights into the underlying molecular mechanisms of ciliary pathologies. According to our analysis, the reported dynamic regulatory modes can be a physiological reaction to alterations in the extracellular environment. However, modification of the dynamic modes, as a result of genetic mutations or environmental conditions, can cause a life threatening pathology.
  • Masterton, R. et al. (2010). Post-translational events of a model reporter protein proceed with higher fidelity and accuracy upon mild hypothermic culturing of Chinese hamster ovary cells. Biotechnology and Bioengineering [Online] 105:215-220. Available at: http://dx.doi.org/10.1002/bit.22533.
    Chinese hamster ovary cells (CHO) are routinely used in industry to produce recombinant therapeutic proteins and a number of studies have reported increased recombinant mRNA levels at temperatures <37°C. Surprisingly, the effect of reduced temperature on mRNA translation in CHO cells has not been investigated despite this process being highly responsive to environmental stresses. The relationship between low temperature culturing of CHO cells and mRNA translation was therefore investigated using labeling studies and dual luciferase reporter gene technology. Global protein synthetic capacity was not greatly affected at 32°C but was diminished at lower temperatures. The expression of both cap-dependent and cap-independent (IRES driven) mRNA translated luciferase reporter gene activity was highest at 32°C on a per cell basis and this was partially accounted for by increased mRNA levels. Importantly, post-translational events appear to proceed with higher fidelity and accuracy at 32°C than 37oC resulting in increased yield of active protein as opposed to an increase in total polypeptide synthesis. Therefore at 32°C recombinant cap-dependent mRNA translation appears sufficient to maintain recombinant protein yields on a per cell basis and this is associated with improved post-translational processing.
  • Jossé, L., Smales, C. and Tuite, M. (2010). Transient expression of human TorsinA enhances secretion of two functionally distinct proteins in cultured Chinese hamster ovary (CHO) cells. Biotechnology and Bioengineering [Online] 105:556-566. Available at: http://dx.doi.org/10.1002/bit.22572.
    Cultured mammalian cells, particularly Chinese hamster ovary (CHO) cells, are widely exploited as hosts for the production of recombinant proteins, but often yields are limiting. Such limitations may be due in part to the misfolding and subsequent degradation of the heterologous proteins. Consequently we have determined whether transiently co-expressing yeast and/or mammalian chaperones that act to disaggregate proteins, in CHO cell lines, improve the levels of either a cytoplasmic (Fluc) or secreted (Gluc) form of luciferase or an immunoglobulin IgG4 molecule. Over-expression of the yeast ‘protein disaggregase’ Hsp104 in a CHO cell line increased the levels of Fluc more significantly than for Gluc although levels were not further elevated by over-expression of the yeast or mammalian Hsp70/40 chaperones. Over-expression of TorsinA, a mammalian protein related in sequence to yeast Hsp104, but located in the ER, significantly increased the level of secreted Gluc from CHO cells by 2.5-fold and to a lesser extent the secreted levels of a recombinant IgG4 molecule. These observations indicate that the over-expression of yeast Hsp104 in mammalian cells can improve recombinant protein yield and that over-expression of TorsinA in the ER can promote secretion of heterologous proteins from mammalian cells.
  • Reid, C. et al. (2010). Rapid whole monoclonal antibody analysis by mass spectrometry: An Ultra scale-down study of the effect of harvesting by centrifugation on the post-translational modification profile. Biotechnology and Bioengineering [Online] 107:85-95. Available at: http://dx.doi.org/10.1002/bit.22790.
    With the trend towards the generation and production of increasing numbers of complex biopharmaceutical (protein based) products, there is an increased need and requirement to characterize both the product and production process in terms of robustness and reproducibility. This is of particular importance for products from mammalian cell culture which have large molecular structures and more often than not complex post-translational modifications (PTMs) that can impact the efficacy, stability and ultimately the safety of the final product. It is therefore vital to understand how the operating conditions of a bioprocess affect the distribution and make up of these PTMs to ensure a consistent quality and activity in the final product. Here we have characterized a typical bioprocess and determined (a) how the time of harvest from a mammalian cell culture and, (b) through the use of an ultra scale-down mimic how the nature of the primary recovery stages, affect the distribution and make up of the PTMs observed on a recombinant IgG4 monoclonal antibody. In particular we describe the use of rapid whole antibody analysis by mass spectrometry to analyze simultaneously the changes that occur to the cleavage of heavy chain C-terminal lysine residues and the glycosylation pattern, as well as the presence of HL dimers. The time of harvest was found to have a large impact upon the range of glycosylation patterns observed, but not upon C-terminal lysine cleavage. The culture age had a profound impact on the ratio of different glycan moieties found on antibody molecules. The proportion of short glycans increased (e.g., (G0F)2 20–35%), with an associated decrease in the proportion of long glycans with culture age (e.g., (G2F)2 7–4%, and G1F/G2F from 15.2% to 7.8%). Ultra scale-down mimics showed that subsequent processing of these cultures did not change the post-translational modifications investigated, but did increase the proportion of half antibodies present in the process stream. The combination of ultra scale-down methodology and whole antibody analysis by mass spectrometry has demonstrated that the effects of processing on the detailed molecular structure of a monoclonal antibody can be rapidly determined early in the development process. In this study we have demonstrated this analysis to be applicable to critical process design decisions (e.g., time of harvest) in terms of achieving a desired molecular structure, but this approach could also be applied as a selection criterion as to the suitability of a platform process for the preparation of a new drug candidate. Also the methodology provides means for bioprocess engineers to predict at the discovery phase how a bioprocess will impact upon the quality of the final product.
  • Mead, E. et al. (2009). Identification of the limitations on recombinant gene expression in CHO cell lines with varying luciferase production rates. Biotechnology and Bioengineering [Online] 102:1593-1602. Available at: http://dx.doi.org/10.1002/bit.22201.
    Mammalian cell lines are currently employed as one of the main cellular factories for the expression of recombinant protein-based drugs. The establishment of high-producing cell lines typically begins with a heterogeneous starter population of cells, from which the highest producing cells are selected via empirical approaches. This approach is time consuming, and is likely to encounter natural upper limits imposed by the inherent biology of the cell lines in question. In an attempt to understand both the nature of the variability in populations of cells transfected with recombinant protein encoding DNA and the natural mechanisms of productivity limitation, we developed protocols for the detailed investigation of gene expression pathways in such cell lines. This novel approach was then applied to a set of clonal CHOK1 cell lines producing recombinant luciferase with varying productivities. Our results show that the initial limitation in these cell lines is at the transcriptional level, however in the highest producing cell line post-translational mechanisms affecting both protein turnover and protein folding become severely limiting. The implications for the development of strategies to engineer cells for enhanced recombinant protein production levels are discussed.
  • Al-Fageeh, M. and Smales, C. (2009). Cold-inducible RNA binding protein (CIRP) expression is modulated by alternative mRNAs. RNA [Online] 15:1164-1176. Available at: http://dx.doi.org/10.1261/rna.1179109.
    Cold-inducible RNA binding protein (CIRP) is a mammalian protein whose expression is up-regulated in response to mild hypothermia. Although the exact function of this protein is currently unknown, it is thought to function as an RNA chaperone, facilitating mRNA translation upon the perception of cold stress. In this study we have identified and characterized the major CIRP 5′-untranslated region (5′-UTR) transcripts in mouse embryonic fibroblast NIH-3T3 cells. We show that the 5′-UTR of CIRP, a protein highly homologous to the cold-shock protein Rbm3, is much shorter than the previously published 5′ leader sequence of Rbm3. In addition, three major CIRP transcripts with different transcription start sites are generated, with the levels of each of these transcripts being regulated in response to time and temperature. The major transcript generated at 37°C does not encode for the full-length CIRP open reading frame, while the two major transcripts at 32°C do. Further, the longest transcript detected at 32°C shows a discrete expression and stability profile under mild hypothermic conditions and exhibits internal ribosome entry segment (IRES)-like activity. The IRES-like activity is not responsive to conditions of mild hypothermia or hypoxia, but the levels and stability of the transcript harboring the putative IRES are increased at 32°C. We discuss the emerging transcriptional and translational mechanisms by which CIRP expression appears to be controlled and the role that the 5′-UTR plays in the modulation of CIRP expression.
  • Hayes, N., Smales, C. and Klappa, P. (2009). Protein disulfide isomerase does not control recombinant IgG4 productivity in mammalian cell lines. Biotechnology and Bioengineering [Online] 105:770-779. Available at: http://dx.doi.org/10.1002/bit.22587.
    Post-translational limitations in the endoplasmic reticulum during recombinant monoclonal antibody production are an important factor in lowering the capacity for synthesis and secretion of correctly folded proteins. Mammalian protein disulfide isomerase (PDI) has previously been shown to have a role in the formation of disulfide bonds in immunoglobulins. Several attempts have been made to improve the rate of recombinant protein production by overexpressing PDI but the results from these studies have been inconclusive. Here we examine the effect of (a) transiently silencing PDI mRNA and (b) increasing the intracellular levels of members of the PDI family (PDI, ERp72, and PDIp) on the mRNA levels, assembly and secretion of an IgG4 isotype. Although transiently silencing PDI in NS0/2N2 cells suggests that PDI is involved in disulfide bond formation of this subclass of antibody, our results show that PDI does not control the overall IgG4 productivity. Furthermore, overexpression of members of the PDI family in a Chinese hamster ovary (CHO) cell line does not improve productivity and hence we conclude that the catalysis of disulfide bond formation is not rate limiting for IgG4 production.
  • Roobol, A. et al. (2009). Biochemical insights into the mechanisms central to the response of mammalian cells to cold stress and subsequent rewarming. FEBS Journal [Online] 276:286-302. Available at: http://dx.doi.org/10.1111/j.1742-4658.2008.06781.x.
    Mammalian cells cultured in vitro are able to recover from cold stress. However, the mechanisms activated during cold stress and recovery are still being determined. We here report the effects of hypothermia on cellular architecture, cell cycle progression, mRNA stability, protein synthesis and degradation in three mammalian cell lines. The cellular structures examined were, in general, well maintained during mild hypothermia (27-32 degrees C) but became increasingly disrupted at low temperatures (4-10 degrees C). The degradation rates of all mRNAs and proteins examined were much reduced at 27 degrees C, and overall protein synthesis rates were gradually reduced with temperature down to 20 degrees C. Proteins involved in a range of cellular activities were either upregulated or downregulated at 32 and 27 degrees C during cold stress and recovery. Many of these proteins were molecular chaperones, but they did not include the inducible heat shock protein Hsp72. Further detailed investigation of specific proteins revealed that the responses to cold stress and recovery are at least partially controlled by modulation of p53, Grp75 and eIF3i levels. Furthermore, under conditions of severe cold stress (4 degrees C), lipid-containing structures were observed that appeared to be in the process of being secreted from the cell that were not observed at less severe cold stress temperatures. Our findings shed light on the mechanisms involved and activated in mammalian cells upon cold stress and recovery.

Book section

  • Jossé, L., Smales, C. and Tuite, M. (2012). Engineering the Chaperone Network of CHO Cells for Optimal Recombinant Protein Production and Authenticity. in: Recombinant Gene Expression. Springer New York, pp. 595-608. Available at: http://dx.doi.org/10.1007/978-1-61779-433-9_32.
    All proteins fold into a defined three-dimensional shape that is compatible with the cellular role and/or biological activity of those proteins. Molecular chaperones are a family of proteins whose role is to assist the folding and targeting of proteins in both normal and stressed cells. The rational manipulation of chaperone levels in a cell line engineered to produce a defined recombinant protein (rP) can significantly improve both the achievable steady-state levels and authenticity of a wide range of recombinant proteins. Here, we describe the methodology associated with expressing a variety of molecular chaperones in Chinese hamster ovary (CHO) lines in order to improve their recombinant protein production capacity. These chaperones include both those that facilitate the folding of the polypeptide chain (i.e. Hsp70, Hsp40) and those that can re-fold proteins that have misfolded in the cell (i.e. ClpB/Hsp104). This latter property is particularly important given the propensity for highly expressed recombinant proteins to misfold in the “foreign” cellular environment.
  • Mead, E. and Smales, C. (2011). mRNA Translation and Recombinant Gene Expression from Mammalian Cell Expression Systems. in: Comprehensive Biotechnology. Elsevier, pp. 403-409. Available at: http://dx.doi.org/10.1016/B978-0-08-088504-9.00043-X.