Robert Bristow

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MD, PhD, University of Toronto
Email Dr. Rob Bristow


DNA Repair and Genetic Instability in Solid Tumours :

Cells have developed a sophisticated approach to the initial sensing and subsequent repair of DNA damage to preserve genetic stability. The objective of our clinico-translational laboratory is to understand the effect of the tumour microenvironment on the ATM-p53-53BP1 DNA damage signaling pathway and DNA double-strand break (DNA-dsb) repair. Our studies suggest that hypoxic tumour cells can have decreased DNA-dsb repair (e.g. decreased homologous recombination) and an aggressive “mutator” phenotype. We are therefore tracking DNA damage
responses and repair within normal and tumour tissues to develop novel diagnostics and molecular-targeted therapies.

We interrogate protein-protein interactions during DNA-dsb repair and cell-cycle checkpoints using: siRNA knockdowns, DNA-rejoining assays (comet and CFGE assays), chromatin immunoprecipitation (ChIP), biochemical fractionation, fluorescently-tagged proteins and quantitative confocal microscopy with UV-microbeams ( ).

(i) p53 and DNA repair: Mutations in the p53 tumour suppressor protein are common in many human cancers. We are interested in certain MTp53 proteins that have acquired novel properties or "gain of function" in their ability to detect DNAdsbs, but over-ride DNA damage cell cycle checkpoints. This can lead to therapy resistance. We are tracking the sub-cellular location and function of ATM-dependent p53 phosphoforms and 53BP1 (a p53-binding protein) in response to DNA breaks and evaluating new therapies that target MTp53.

(ii) Hypoxia, DNA repair and prostate cancer: Many prostate cancer patients die each year solely from the failure of radical radiotherapy to control the primary tumour.We are interested in developing genomic (SNP, CGH) and proteomic (serum, plasma or urine) biomarkers to predict cancer therapy cure and toxicity. This includes the assessment of tissue microarrays (TMAs) for novel protein expression in patients who fail therapy. For example, we are investigating the role of hypoxia as a negative prognostic factor in prostate and other cancers. We believe that novel cancer therapies can target these resistant hypoxic cells by taking advantage of DNA repair defects. We therefore hope to select the most effective treatment for individual patients based on individual biology.

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List of Key Publications:

Link to Pubmed Publications
  • Al Rashid ST, Dellaire G, Cuddihy A, et al. Evidence for the Direct Binding of Phosphorylated p53 to Sites of DNA Break In Vivo. Cancer Research, 65(23):10810-21, 2005.

  • Choudhury A, Cuddihy A, Bristow RG. Radiation and Other New Molecular-Targeted Agents, Part I: Targeting ATM-ATR Checkpoints, DNA Repair and the Proteasome. Seminars in Radiation Oncology: 16(1): 51-58, 2006.

  • Chan N, Meng A, Bindra R, et al. Chronic hypoxia decreases synthesis of homologous recombination proteins and therapeutic
    resistance. Cancer Research: 68(2), 2008.

  • Bristow RG and Hill RP: Hypoxia, DNA Repair and Genetic Instability: A Driving Force in Cancer Progression and A Basis for Novel Therapies. Nature Cancer Reviews, In Press, 2008