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Links between DNA polymerase beta expression and sensitivity to bleomycin
Shukun Liu1, Yanhao Lai, Wei Zhao
1Department of Environmental Health, Sichuan University, West China School of Public Health, Chengdu, PR China.
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.
Insights
DNA polymerase beta (pol β) deficiency enhances bleomycin (BLM) anti-tumor drug sensitivity by impairing DNA repair. Lack of pol β increases oxidative DNA damage and mutations, making cancer cells more vulnerable to BLM treatment.
Area of Science:
- Molecular Biology
- Cancer Research
- Genetics
Background:
- Bleomycin (BLM) is an anti-tumor antibiotic causing cell death via oxidative DNA damage.
- Cellular resistance to BLM limits its clinical efficacy.
- Base excision repair (BER) pathway, involving DNA polymerase beta (pol β), repairs oxidative DNA damage and influences resistance to anticancer drugs.
Purpose of the Study:
- To investigate the role of DNA polymerase beta (pol β) in bleomycin (BLM)-induced DNA damage and cellular sensitivity.
- To determine if inhibiting pol β can enhance BLM's anti-tumor effects.
Main Methods:
- Comparison of BLM sensitivity in mouse embryo fibroblasts (MEFs) with wild-type and pol β-deficient genotypes.
- Assessment of reactive oxygen species (ROS) levels, DNA single-strand breaks, and chromosomal aberrations.
- Measurement of hprt gene mutation frequency.
Main Results:
- Pol β-deficient MEFs exhibited significantly lower cell viability upon BLM treatment compared to wild-type cells.
- Pol β deficiency led to increased ROS levels, DNA single-strand breaks, and chromosomal damage.
- Absence of pol β resulted in a higher frequency of hprt gene mutations.
Conclusions:
- The BER pathway, particularly pol β, plays a critical role in repairing BLM-induced oxidative DNA damage.
- Pol β deficiency impairs DNA repair, leading to enhanced oxidative DNA damage, chromosomal instability, and gene mutations.
- The absence of pol β contributes to hypersensitivity to bleomycin, suggesting pol β as a potential therapeutic target to overcome BLM resistance.
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