Downregulation of PIF1 induce DNA damage and inhibit ovarian cancer cell proliferation via RAD51

Abstract

Background PIF1 helicase (5ʹ→3ʹ DNA helicase) is a member of helicase superfamily 1. It has unwinding activity and plays a crucial role in maintaining genome stability and coordinating DNA damage repair processes. Overexpression of PIF1 is common in several cancers; however, its role in ovarian cancer remains unclear. This study aimed to elucidate the regulatory role of PIF1 in ovarian cancer and explore its mechanism. Results Analysis of patient samples and public database datasets revealed a negative correlation between PIF1 overexpression and the overall survival rate of the patients. We found through molecular biology experiments and xenograft tumor models in nude mice that CRISPR/Cas9-mediated PIF1 partial knockdown in ovarian cancer cell lines significantly inhibited proliferation and clonogenicity, promoted senescence, and induced G2 cell cycle arrest. Moreover, PIF1 partial deficiency enhanced DNA damage in ovarian cancer cells, particularly sensitive to cisplatin. RAD51 serves as a central scaffold protein for homologous recombination repair and is crucial for timely and accurate DNA repair. We observed that PIF1 partial knockdown resulted in significant reduction of RAD51 in ovarian cancer cells. Notably, RAD51 overexpression in PIF1 partially deficient ovarian cancer cells rescued cell proliferation and DNA damage by increasing PIF1 expression. Immunofluorescence revealed the co-localization of EGFP-PIF1 and RAD51 in the cell nucleus, suggesting that the interaction between PIF1 and RAD51 may regulate the DNA damage response and cell survival in ovarian cancer cells. Conclusions Our study revealed that PIF1 is a druggable target for inducing DNA damage in ovarian cancer cells and provides insights into the potential synergistic mechanisms of action between PIF1 and RAD51 in ovarian cancer therapy.