Dr. Michael Weinfeld is currently appointed as Professor in the Division of Experimental Oncology in the Faculty of Medicine and Dentistry.
The focus of the research in my laboratory is the cellular response to chemical and radiation-induced stress. We are particularly interested in DNA damage and repair, and cell death and survival. Characterization of polynucleotide kinase and other DNA repair enzymes that act at strand break termini
Several years ago we cloned human polynucleotide kinase/phosphatase (PNKP), an enzyme that has the ability to phosphorylate 5'-hydroxyl termini and dephosphorylate 3'-phosphate termini, thus rendering the DNA termini suitable for the subsequent action of DNA polymerases and/or DNA ligases. With colleagues in the UK, US, France and Canada, we have shown that the protein is involved in several DNA repair pathways including base-excision repair, single-strand break repair and the nonhomologous end joining double-strand break repair pathway. Stable RNAi-mediated down-regulation of PNKP in human cells increases their sensitivity to ionizing radiation and camptothecin, a topoisomerase I inhibitor, and leads to a significant elevation in their spontaneous mutation frequency. In collaboration with Dr.
Dallan Young (University of Calgary), we similarly observed that a PNK knockout mutant of S. pombe is hypersensitive to both agents.
Together with Drs. Mark Glover (University of Alberta) and Susan Lees-Miller (University of Calgary), we have initiated a detailed biophysical examination of the protein and its interaction with DNA and other DNA repair enzymes, such as XRCC1 and XRCC4. We are also collaborating with Dr.
Frank Jirik (University of Calgary) to generate transgenic mice to define the physiological function(s) of PNK,
and to dissect the importance of kinase and phosphatase activities. Recently, in collaboration with Dr.
Dennis Hall (University of Alberta), we have identified a small molecule inhibitor of the phosphatase activity of PNKP and shown that it sensitizes cells to ionizing radiation and camptothecin. In collaboration with Dr.
Edan Foley (university
we have identified synthetic lethal partners of PNKP including SHP-1 and PTEN. Investigation of the carcinogenic properties of arsenic
Arsenic is a major environmental carcinogen, but it has been shown to be very difficult to induce tumours in laboratory animals with arsenic. This has led to the hypothesis that arsenic is a co-carcinogen that enhances the carcinogenicity of other agents. In collaboration with Dr.
X. Chris Le (University of Alberta), we are examining the influence of arsenic on the formation and repair of DNA adducts generated by the carcinogenic polycyclic aromatic hydrocarbon benzo[a]pyrene and its metabolites. DNA repair in tumour initiating cells
Recent evidence has led to the proposal that normal stem cells may be the key cells in a tissue or organ that undergo mutation and transformation giving rise to “cancer stem cells”. Because normal adult stem cells are slowly dividing, long-lived cells and the precursors to differentiated cells, DNA repair and mutation avoidance in these cells should be critical. The cancer stem cells, however, having
undergone mutation, may have dysregulated DNA repair activity in one or more repair pathways, and/or reduced potential to undergo apoptosis or senescence. How normal and cancer stem cells deal with DNA damage and its consequences is therefore
a fundamental question related to cancer etiology
and therapy. We are currently examining the DNA repair profile of breast cancer stem cells. Analysis of low-dose radiation hypersensitivity
Exposure to environmental radiation and the application of new clinical modalities, such as radioimmunotherapy, have heightened the need to understand cellular responses to low dose and low-dose rate ionizing radiation. Many human cell lines exhibit a hyper-radiosensitivity (HRS) to radiation doses < 20 cGy, which manifests as a significant deviation from the clonogenic survival response predicted by a linear-quadratic fit to higher doses. This is followed by increased radioresistance (IRR) at slightly higher doses. Using a variety of cellular and molecular approaches, we have established that the phenomenon of low-dose radiation hypersensitivity is due to p53 and caspase-3 dependent apoptosis. We are further investigating the molecular mechanisms underlying both HRS and IRR.
Cancer, DNA damage, DNA repair, Drug development
Team MembersMembers of the lab
Ismail Abdou (Graduate Student)Dr.
Mohamed El-Gendy (Post-doctoral
Mesfin Fanta (Research Technologist)Dr.
Rajam Mani (Consultant)Dr.
Aghdass Rasouli-Nia (Research Associate)
Zahra Shire (Graduate Student)
Sudip Subedi (Graduate Student)
Felicia Tam (Student) Recent members of the lab
Ashley Ahrens (Student)Dr.
Sharon Barker (Post-doctoral
Louise Enns (Research Technologist)Dr.
Feridoun Karimi-Busheri (Senior Research Associate)
Gary Freschauf (Graduate Student)
Vikie Lamontagne (Research Technologist)
Jane Lee (Research Technologist)Dr.
Meiling Lu (Post-doctoral
Todd Mereniuk (Post-doctoral
Christopher Pisesky (Student)Dr.
Elizabeth Silver (Post-doctoral
Michaela Schubert (Student)Dr.
Nasser Tahbaz (Post-doctoral
César Virgen (Student)
Jodi Wilkinson (Research Technologist)