Portrait of Professor Dan Lloyd

Professor Dan Lloyd

Division of Natural Sciences Director of Education
National Teaching Fellow
Senior Fellow HEA

About

Dan Lloyd joined the University of Kent in 2001 after completing undergraduate studies at the University of York and a PhD at the Institute of Cancer Research. Awarded a Postdoctoral Fellowship from the International Agency for Research on Cancer (IARC), he was a postdoctoral scholar at Stanford University before taking his position at Kent, where he is now Professor. He is a National Teaching Fellow, Senior Fellow of the Higher Education Academy and Fellow of the Royal Society of Biology. Currently he is Director of Graduate Studies (Taught) and Deputy Head of School.
His background in cancer research has underpinned the development of an MSc in Cancer Biology and other Master’s level programmes. Beyond the laboratory, interests relate to the development of creative opportunities for public engagement. A pioneer of science communication training in undergraduate degrees through final year research projects, interests focus particularly on the intersection of science and the arts. Recent public engagement developments have included Chain Reaction (a gallery exhibition marking 30 years of PCR), and the Cocktail Laboratory (a science-themed interactive cocktail party). Cellular Dynamics, which combines cutting-edge biological research with live musical performance, has been featured in the Cheltenham Festival, Canterbury Festival, Norwich Science Festival and as far afield as Hong Kong.
Dan is Director of the Science Strand and a Board Member of the Canterbury Festival. He is a Governor of the University of Kent Academies Trust (UKAT) comprising two Kent schools.  

Teaching

Undergraduate 

  • Pharmacology - BI514  
  • Cancer Biology - BI642  

Postgraduate 

  • Science at Work - BI830  
  • Genomic Stability and Cancer - BI838  
  • Cancer Research in Focus - BI857 

Publications

Article

  • Saintas, E., Abrahams, L., Ahmed, G., Ajakaiye, A., AlHumaidi, A., Ashmore-Harris, C., Clark, I., Dura, U., Fixmer, C., Ike-Morris, C., Mato Prado, M., Mccullough, D., Mishra, S., Schoeler, K., Timur, H., Williamson, M., Alatsatianos, M., Bahsoun, B., Blackburn, E., Hogwood, C., Lithgow, P., Rowe, M., Yiangou, L., Rothweiler, F., Cinatl jr, J., Zehner, R., Baines, A., Garrett, M., Gourlay, C., Griffin, D., Gullick, W., Hargreaves, E., Howard, M., Lloyd, D., Rossman, J., Smales, C., Tsaousis, A., von der Haar, T., Wass, M. and Michaelis, M. (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.
  • Popay, A., Lloyd, D., Wass, M. and Michaelis, M. (2017). Dexamethasone for the Prevention of Cisplatin-induced Ototoxicity. Clinical Cancer Drugs [Online] 4:59-64. Available at: https://doi.org/10.2174/2212697X04666170331171359.
    Background: Cisplatin is a commonly used anti-cancer drug. However, its use is associated with severe side effects including ototoxicity that affects a large fraction of cisplatin-treated patients. Approved therapies that reduce cisplatin-induced ototoxicity are lacking. Among the candidate therapeutics, dexamethasone stands out. There is extensive experience of its use in combination with cisplatin for the prevention of chemotherapy-induced nausea and vomiting indicating that dexamethasone does not affect the anti-cancer effects of cisplatin.

    Objective: The objective of this study is to assess the potential of dexamethasone for the prevention of cisplatin-induced ototoxicity by a systematic analysis of the available evidence.
    Method: The databases PubMed and Web of Science were used to identify relevant articles by using the search terms 'cisplatin', 'ototoxicity', and 'dexamethasone'.
    Results: We identified 16 relevant original research articles. The analyzed studies reported conflicting results on the effects of dexamethasone on cisplatin-induced ototoxicity. However, studies in which dexamethasone was used prior to cisplatin treatment and directly administered into the tympanic cavity of the middle ear consistently reported beneficial effects. The use of sustained release formulations that prolong the availability of dexamethasone within the ear further improved the efficacy of dexamethasone.
    Conclusion: Dexamethasone is a promising candidate drug for the prevention of cisplatin-induced ototoxicity when applied intratympanically. Optimized formulations and administration schedules with regard to dose and time of application need to be developed.
  • Weeks, A., Blower, P. and Lloyd, D. (2013). p53-dependent radiobiological responses to internalised indium-111 in human cells. Nuclear Medicine and Biology [Online] 40:73-79. Available at: http://dx.doi.org/10.1016/j.nucmedbio.2012.08.009.
    INTRODUCTION:

    The p53 tumour suppressor protein plays a pivotal role in the response of mammalian cells to DNA damage. It regulates cell cycle progression, apoptosis and DNA repair mechanisms and is therefore likely to influence response to targeted radionuclide therapy. This study investigated the role of p53 in the cellular response to the Auger-emitting radionuclide indium-111.

    METHODS:

    Two stable clones of a HT1080 fibrosarcoma cell line, differing only in p53 status due to RNAi-mediated knockdown of p53 expression, were incubated for 1 h with [¹¹¹In]-oxinate (0-10 MBq/ml). Radiopharmaceutical uptake into HT1080 cells was measured in situ using a non-contact phosphorimager method. Cellular sensitivity and DNA damage were measured by, respectively, clonogenic survival analysis and the single cell gel electrophoresis (Comet) assay.

    RESULTS:

    Mean uptake of [¹¹¹In]-oxinate in HT1080 cells was unaffected by p53 status, reaching a maximum of 9Bq/cell. [¹¹¹In]-oxinate-induced cytotoxicity was also identical in both clones, as measured by IC50 (0.68 MBq/ml). However the formation of DNA damage, measured immediately after treatment with [¹¹¹In]-oxinate, was found to be up to 2.5-fold higher in the p53-deficient HT1080 clone.

    CONCLUSIONS:

    The increased DNA damage induced in p53-deficient HT1080 cells suggests an early deficiency in the repair of DNA damage during the treatment period. However, the similarity in cellular sensitivity, irrespective of p53 status, suggests that reduced p53 leads to a concomitant reduction in p53-dependent cytotoxicity despite the persistence of DNA damage. The results may provide insight into how tumours that differ in p53 status respond to therapeutic radionuclides.
  • Weeks, A., Paul, R., Marsden, P., Blower, P. and Lloyd, D. (2010). Radiobiological effects of hypoxia-dependent uptake of (64)Cu-ATSM: enhanced DNA damage and cytotoxicity in hypoxic cells. European Journal of Nuclear Medicine and Molecular Imaging [Online] 37:330-338. Available at: http://dx.doi.org/10.1007/s00259-009-1305-8.
    PURPOSE: Hypoxia occurs frequently in cancers and can lead to therapeutic resistance due to poor perfusion and loss of the oxygen enhancement effect. (64)Cu-ATSM has shown promise as a hypoxia diagnostic agent due to its selective uptake and retention in hypoxic cells and its emission of positrons for PET imaging. (64)Cu also emits radiotoxic Auger electrons and beta(-) particles and may therefore exhibit therapeutic potential when concentrated in hypoxic tissue. METHODS: MCF-7 cells were treated with 0-10 MBq/ml (64)Cu-ATSM under differing oxygen conditions ranging from normoxia to severe hypoxia. Intracellular response to hypoxia was measured using Western blotting for expression of HIF-1alpha, while cellular accumulation of (64)Cu was measured by gamma counting. DNA damage and cytotoxicity were measured with, respectively, the Comet assay and clonogenic survival. RESULTS: (64)Cu-ATSM uptake in MCF-7 cells increased as atmospheric oxygen decreased (up to 5.6 Bq/cell at 20.9% oxygen, 10.4 Bq/cell at 0.1% oxygen and 26.0 Bq/cell at anoxia). Toxicity of (64)Cu-ATSM in MCF-7 cells also increased as atmospheric oxygen decreased, with survival of 9.8, 1.5 and 0% in cells exposed to 10 MBq/ml at 20.9, 0.1 and 0% oxygen. The Comet assay revealed a statistically significant increase in (64)Cu-ATSM-induced DNA damage under hypoxic conditions. CONCLUSION: The results support a model in which hypoxia-enhanced uptake of radiotoxic (64)Cu induces sufficient DNA damage and toxicity to overcome the documented radioresistance in hypoxic MCF-7 cells. This suggests that (64)Cu-ATSM and related complexes have potential for targeted radionuclide therapy of hypoxic tumours.
  • Bhana, S., Hewer, A., Phillips, D. and Lloyd, D. (2008). p53-dependent global nucleotide excision repair of cisplatin-induced intrastrand cross links in human cells. Mutagenesis [Online] 23:131-136. Available at: http://dx.doi.org/10.1093/mutage/gen001.
    Cisplatin is an extremely effective chemotherapeutic agent used for the treatment of testicular and other solid tumours. It induces a variety of structural modifications in DNA, the most abundant being the GpG- and ApG-1,2-intrastrand cross links formed between adjacent purine bases. These cross links account for approximately 90% of cisplatin-induced DNA damage and are thought to be responsible for the cytotoxic activity of the drug. In human cells, the nucleotide excision repair (NER) process removes the intrastrand cross links from the genome, the efficiency of which is likely to be an important determinant of cisplatin cytotoxicity. We have investigated whether the p53 tumour suppressor status affects global NER of cisplatin-induced intrastrand cross links in human cells. We have used a (32)P-postlabelling method to monitor the removal of GpG- and ApG-intrastrand cross links from two human cell models (the 041TR system, in which p53 is regulated by a tetracycline-inducible promoter, together with WI38 fibroblasts and the SV40-transformed derivative VA13) that each differ in p53 status. We demonstrate that the absence of functional p53 leads to persistence of both cisplatin-induced intrastrand cross links in the genome, suggesting that p53 regulates NER of these DNA lesions. This observation extends the role of p53 in NER beyond enhancing the removal of environmentally induced DNA lesions to include those of clinical origin. Given the frequency of p53 mutations in human tumours, these results may have implications for the use of cisplatin in cancer chemotherapy.
  • Bhana, S. and Lloyd, D. (2008). The role of p53 in DNA damage-mediated cytotoxicity overrides its ability to regulate nucleotide excision repair in human fibroblasts. Mutagenesis [Online] 23:43-50. Available at: http://dx.doi.org/10.1093/mutage/gem041.
    The p53 tumour suppressor protein plays a pivotal role in the response of mammalian cells to DNA damage. In addition to its regulatory role in cell cycle progression, p53 regulates apoptosis and can therefore influence cellular survival in response to DNA damage. More recent work has revealed that p53 is also involved in the nucleotide excision repair (NER) of structurally diverse types of DNA damage. The relative influence of p53 on NER and cellular sensitivity to DNA damage was investigated in this study using cells that differ in p53 status. Two cell models were selected: 041 TR fibroblasts in which the expression of p53 is regulated by a tetracycline-inducible promoter, and WI38 primary lung fibroblasts together with their isogenic derivative VA13, in which p53 is abrogated post-translationally by SV40 transformation. Cells were exposed to the clinically and environmentally relevant DNA-damaging agents cisplatin (0-5 microM, 2 h), (+/-)-anti-benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide (0-0.5 microM, 30 min) and UV-C (0-5 J/m2), each of which induce structurally distinct types of DNA damage known to be subject to p53-dependent NER. Sensitivity of the p53-proficient and p53-deficient cells to this DNA damage was then compared at each dose of DNA-damaging agent using the clonogenic survival assay and the colorimetric MTT assay. p53-proficient cells were more sensitive than p53-deficient cells to cisplatin, (+/-)-anti-benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide and UV-C; these differences in cellular sensitivity were more apparent in the 041 TR cells (up to 3.6-, 5.8- and 1.9-fold, respectively) than the WI38/VA13 cells (up to 2.3-, 1.4- and 1.4-fold, respectively). Thus, despite the well-documented persistence of DNA damage in p53-deficient fibroblasts due to impaired NER, loss of p53 results in reduced DNA damage-mediated cytotoxicity.
  • Weeks, A., Paul, R., Blower, P. and Lloyd, D. (2007). Cellular toxicity and DNA damage induced by the hypoxia-selective imaging agent (64)CuATSM. European Journal of Nuclear Medicine and Medical Imaging 34:S231-S231.
  • Hanawalt, P., Ford, J. and Lloyd, D. (2003). Functional characterization of global genomic DNA repair and its implications for cancer. Mutation Research/Reviews in Mutation Research [Online] 544:107-114. Available at: http://dx.doi.org/10.1016/j.mrrev.2003.06.002.
    The most versatile cellular pathway for dealing with a large variety of structurally-unrelated DNA alterations is nucleotide excision repair (NER). Most genomic damage, if not repaired, may contribute to mutagenesis and carcinogenesis, as well as to cellular lethality. There are two subpathways of NER, termed global genomic repair (GGR) and transcription-coupled repair (TCR); While GGR deals with all repairable lesions throughout the genome, TCR is selective for the transcribed DNA strand in expressed genes. Proteins involved in the initial recognition of lesions for GGR as well as for TCR (i.e. RNA polymerase) may sometimes initiate gratuitous repair events in undamaged DNA. However, the damage recognition enzymes for GGR are normally maintained at very low levels unless the cells are genomically stressed. Following UV irradiation in human fibroblasts the efficiency of GGR is upregulated through activation of the p53 tumor suppressor gene. The transactivation role of p53 includes control of expression of the genes, XPC and XPE, which are implicated in GGR but not TCR. These inducible responses are essential for the efficient repair of the most prominent lesion produced by UV, the cyclobutane pyrimidine dimer (CPD). They are also clinically relevant, as we have shown them to operate upon chemical carcinogen DNA damage at levels to which humans are environmentally exposed (e.g. through smoking). Thus, for benzo(a)pyrene (at 10-50 adducts per 10(8) nucleotides) repair was essentially complete within 1 day in p53(+/+) human fibroblasts while no repair was detected within 3 days in p53(-/-) cells. The levels of all four DNA adducts formed by benzo(g)chrysene, also exhibited p53-dependent control in human fibroblasts. However, unlike humans most rodent tissues are deficient in the p53-dependent GGR pathway. Since rodents are used as surrogates for humans in environmental cancer risk assessment it is very important that we determine how they differ from humans with respect to DNA repair and oncogenic responses to environmental genotoxins.
  • Lloyd, D. and Hanawalt, P. (2002). p53 Controls Global Nucleotide Excision Repair of Low Levels of Structurally Diverse Benzo(g)chrysene-DNA Adducts in Human Fibroblasts. Cancer Research 62:5288-5294.
    Benzo(g)chrysene is a widespread environmental contaminant and potent carcinogen. We have measured the formation and nucleotide excision repair of covalent DNA adducts formed by the DNA-reactive metabolite of this compound in human fibroblasts, in which expression of the p53 tumor suppressor gene could be controlled by a tetracycline-inducible promoter. Cells were exposed for 1 h to 0.01, 0.1, or 1.2 microM (+/-)-anti-benzo(g)chrysene diol-epoxide, and DNA adducts were assessed at various post-treatment times by subjecting isolated DNA to (32)P-postlabeling analysis. Four major DNA adducts were detected, corresponding to the reaction of either the (+)- or (-)-anti-benzo(g)chrysene diol-epoxide stereoisomer with adenine or guanine. Treatment with 1.2 microM resulted in a level of 1100 total adducts/10(8) nucleotides for both p53-proficient and -deficient cells; removal of adducts was not observed in either case. In cells treated with 0.1 microM, the maximum level of total adducts at 24 h was 150/10(8) nucleotides in p53-proficient cells and 210 adducts/10(8) nucleotides in p53-deficient cells. A concentration of 0.01 microM resulted in a maximum of 20 adducts/10(8) nucleotides in p53-proficient cells at 4 h, but 40 adducts/10(8) nucleotides persisted in p53-deficient cells at 24 h. Whereas there were clear differences in the time course of adduct levels in p53-proficient compared with p53-deficient cells treated with 0.1 microM or 0.01 microM, these levels did not decrease extensively over 3 days. This is likely because of the stabilization of the diol-epoxide in cells, and consequent exposure and formation of adducts for many hours after the initial treatment. Furthermore, despite minor quantitative differences, all 4 of the adducts behaved similarly with respect to the effect of p53 expression on their removal. p53 appears to minimize the appearance of benzo(g)chrysene adducts in human cells by up-regulating global nucleotide excision repair and reducing the maximum adduct levels achieved. The fact that this p53-dependent effect is noted at levels of DNA adducts that are commonly found in human tissues (i.e., <100 adducts/10(8) nucleotides) because of environmental factors such as smoking is particularly significant with respect to human carcinogenesis related to environmental exposure.
  • Tornaletti, S., Maeda, L., Lloyd, D., Reines, D. and Hanawalt, P. (2001). Effect of thymine glycol on transcription elongation by T7 RNA polymerase and mammalian RNA polymerase II. Journal of Biological Chemistry [Online] 276:45367-45371. Available at: http://dx.doi.org/10.1074/jbc.M105282200.
    Thymine glycols are formed in DNA by exposure to ionizing radiation or oxidative stress. Although these lesions are repaired by the base excision repair pathway, they have been shown also to be subject to transcription-coupled repair. A current model for transcription-coupled repair proposes that RNA polymerase II arrested at a DNA lesion provides a signal for recruitment of the repair enzymes to the lesion site. Here we report the effect of thymine glycol on transcription elongation by T7 RNA polymerase and RNA polymerase II from rat liver. DNA substrates containing a single thymine glycol located either in the transcribed or nontranscribed strand were used to carry out in vitro transcription. We found that thymine glycol in the transcribed strand blocked transcription elongation by T7 RNA polymerase approximately 50% of the time but did not block RNA polymerase II. Thymine glycol in the nontranscribed strand did not affect transcription by either polymerase. These results suggest that arrest of RNA polymerase elongation by thymine glycol is not necessary for transcription-coupled repair of this lesion. Additional factors that recognize and bind thymine glycol in DNA may be required to ensure RNA polymerase arrest and the initiation of transcription-coupled repair in vivo.

Book section

  • Lloyd, D. (2010). Evaluation of radiopharmaceuticals using cell culture models. In: Theobald, T. ed. Sampson’s Textbook of Radiopharmacy. Pharmaceutical Press, pp. 605-615.
  • Lloyd, D. (2008). Final year research projects in communicating science. In: Luck, M. and Wilson, J. eds. Student Research Projects: Guidance on Practice in the Biosciences. Higher Education Academy, pp. 54-56. Available at: http://www.bioscience.heacademy.ac.uk/resources/guides/.
  • Lloyd, D. (2007). Involving undergraduates in outreach and public engagement through final year projects in science communication. In: Proceedings of the Science Learning and Teaching Conference 2007. Higher Education Academy, pp. 134-137.

Book

  • Hanawalt, P., Crowley, D., Ford, J., Ganesan, A., Lloyd, D., Nouspikel, T., Smith, C., Spivak, G. and Tornaletti, S. (2000). Regulation of Nucleotide Excision Repair in Bacteria and Mammalian Cells. Vol. 65. Cold Spring Harbor Press.

Thesis

  • Rathje, C. (2014). Novel Approaches to Target Infectious Diseases: The Utility of Auger Electrons and ScFvs for Imaging and Control.
    With an increasing number of infectious agents resistant to one or more existing antibiotics, there is a global requirement for new therapeutics. One possible method for treatment of infectious diseases proposed in this study is the adaptation of a technique developed for cancer treatment, targeted radionuclide therapy, with particular interest in Auger electron radiation. Auger electrons are short range and low energy particles emitted from a range of radioactive isotopes.
    As a targeting agent, the antimicrobial peptide fragment UBI 29-41 was used. Antimicrobial peptides have a broad range of target microorganisms, ideal for toxicological studies of Auger electrons. Here, the baseline toxicity of UBI 29-41 was established in a range of model organisms. This enabled the analysis of the toxic effect of Auger electron emitting radio-nuclides using the isotope125I. Although no direct toxic effect was observed with this particular isotope, the labelling allows easy replacement with more potent isotopes.
    To further develop the targeting agent a lipoarabinomannan (LAM) specific single-chain variable fragment (scFv) was developed. LAM is a glycolipid and virulence factor associated with M. tuberculosis, the primary cause of tuberculosis in humans. By isolating the variable domains of a LAM specific monoclonal antibody, linked via a poly-glycine linker, the scFv was assembled in silico. The nucleotide sequence was optimised for and transfected into a Pichia pink expression system. Expression was successful with a ~27kDa product being secreted.
    The novel anti-LAM scFv generated in this study combined with the potential toxic effects of Auger electrons could provide a new avenue for the treatment and diagnosis of tuberculosis.

Show / exhibition

  • Sleigh, C. and Lloyd, D. (2013). Chain Reaction!. [mixed artistic media].
    This show of art and science communication celebrated 30 years of the PCR machine.

Internet publication

  • Lloyd, D. (2015). When Art and Science collide. [Blog]. Available at: http://ntf-association.com/national-teaching-fellows/when-art-and-science-collide/.
  • Lloyd, D. (2006). Final-Year Projects in Science Communication [Bulletin]. Available at: http://www.bioscience.heacademy.ac.uk/resources/bulletin.aspx.
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