Links between DNA polymerase beta expression and sensitivity to bleomycin

• Published in: Toxicology (Amsterdam) Vol. 281; no. 1; pp. 63 - 69
• Main Authors: Liu, Shukun, Lai, Yanhao, Zhao, Wei, Wu, Mei, Zhang, Zunzhen
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ireland Ltd 15-03-2011; Elsevier
• Subjects: Animals; Antibiotics, Antineoplastic - biosynthesis; Base excision repair; Biological and medical sciences; Bleomycin; Bleomycin - pharmacology; Bleomycin - toxicity; Cell Line; Cell Survival - drug effects; Comet Assay; DNA Damage - drug effects; DNA polymerase beta; DNA Polymerase beta - biosynthesis; Dose-Response Relationship, Drug; Drug resistance; Drug Resistance, Neoplasm; Emergency; Fibroblasts - chemistry; Fibroblasts - drug effects; Fibroblasts - enzymology; Medical sciences; Mice; Micronucleus Tests; Mutagenicity Tests; Oxidative DNA damage; Reactive Oxygen Species - analysis; Toxicology; bleomycin; BLM; fMN; 2′,7′-dichlorofluorescin diacetate; Hprt; OTM; Drug resistance; DNA SSBs; mouse embryo fibroblasts; frequency of micronucleus formation; cloning efficiency; reactive oxygen species; MF; mutation frequency; frequency of micronucleated cells; MEFs; CE; Pol β; olive tail moment; base excision repair; BER; Oxidative DNA damage; DCFH-DA; fMNC; hypoxanthine–guanine phosphoribosyltransferase; ROS; DNA polymerase beta; DNA single strand breaks; DNApolymerase beta; Base excision repair; Bleomycin; Antineoplastic agent; Oxidative stress; Treatment resistance; Peptides; Enzyme; Transferases; Nucleotide excision repair; Chenopodiaceae; Beta; Nucleotidyltransferases; Antibiotic; Sensitivity; Glycopeptide; Dicotyledones; DNA; Angiospermae; Spermatophyta; Lesion; DNA-directed DNA polymerase
• ISSN: 0300-483X; 1879-3185
• DOI: 10.1016/j.tox.2011.01.008

Abstract Bleomycin (BLM), an important anti-tumor antibiotic, enables cell death through oxidative DNA damage mediated by reactive oxygen species (ROS). However, increasing cellular resistance has become a serious limitation to its clinical application. Base excision repair (BER), the major pathway for repairing oxidative bases, is involved in resistance of DNA-damaging anticancer drugs. DNA polymerase beta (pol β), a critical BER enzyme, has been reported to play a crucial role in combating BLM-induced oxidative DNA damage, as a result, pol β inhibition may increase the sensitivity to BLM. To test this hypothesis, we evaluated the sensitivity to BLM using mouse embryo fibroblasts (MEFs) with distinct pol β expression levels (wild-type, pol β deficiency) and explored the underlying mechanisms. The results showed that cell viability of pol β-deficient MEFs was significantly lower than that of isogenic wild type when treated with the same BLM dosage. In addition, increased ROS level, DNA single strand breaks, and chromosomal breakage were observed in pol β deficient cells, indicating impaired DNA repair and enhanced oxidative DNA damage under pol β deficiency. In agreement with the findings, an enhanced hprt gene mutation frequency was also detected in pol β null cells. In summary, this study demonstrated that BLM-induced DNA damage could be repaired through BER pathway and absence of pol β allows oxidative DNA/chromosome damage and gene mutation, which contributes to BLM hypersensitivity.