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End-joining deficiency and radiosensitization induced by gemcitabine
van Putten JWG1, Groen HJM, K Smid
1Department of Pulmonary Diseases, University Hospital, Groningen, The Netherlands. j.w.g.van.putten@int.azg.nl
Cancer Research
|March 14, 2001
Summary
Gemcitabine (dFdC) enhances radiosensitivity, but its mechanism remains unclear. This study found that a functional nonhomologous end-joining pathway is not required for gemcitabine-mediated radiosensitization.
Area of Science:
- Molecular Biology
- Cancer Research
- Radiochemistry
Background:
- The precise mechanism of radiosensitization by gemcitabine (2',2'-difluoro-2'-deoxycytidine, dFdC) is not fully understood.
- Gemcitabine is a nucleoside analog used in cancer therapy, often in combination with radiation.
Purpose of the Study:
- To investigate the role of nonhomologous end-joining (NHEJ) pathway components in gemcitabine-induced radiosensitization.
- To determine if gemcitabine inhibits the repair of DNA double-strand breaks.
Main Methods:
- Radiosensitization was assessed in various cell lines with differing proficiency in NHEJ components (DNA-PKcs, Ku80).
- Cells were treated with gemcitabine (0.5 and 5 microM) for 4 hours.
- Deoxynucleotide triphosphate levels and cell cycle distribution were analyzed.
Main Results:
- Cells deficient in DNA-dependent protein-kinase catalytic subunit (DNA-PKcs) showed similar radiosensitization to wild-type cells.
- Ku80-deficient cells exhibited enhanced radiosensitization by gemcitabine compared to wild-type cells.
- Complementation of Ku80 deficiency abolished the enhanced radiosensitization.
Conclusions:
- A functional nonhomologous end-joining pathway is not essential for gemcitabine-mediated radiosensitization.
- The results suggest that gemcitabine's radiosensitizing effect is independent of the primary DNA double-strand break repair pathway mediated by NHEJ.