Activity and Cell Cycle Regulation in Response to DNA Damage in Breast Cancer Cell Lines

Common genetic variants mapping to two distinct regions of RADS1B , a paralog of RADS1 , have been associated with breast cancer risk in genome-wide association studies (GWAS). RADS1B is a plausible candidate gene because of its established role in the homologous recombination (HR) process. How germline genetic variation in RADS1B confers susceptibility to breast cancer is not well understood. Here, we investigate the molecular function of RADS1B in breast cancer cell lines by knocking down RADS1B expression by small interfering RNA and treating cells with DNA-damaging agents, namely cisplatin, hydroxyurea, or methyl-methanesulfonate. Our results show that RAD51B -depleted breast cancer cells have increased sensitivity to DNA damage, reduced efficiency of HR, and altered cell cycle checkpoint responses. The influence of RAD51B on the cell cycle checkpoint is independent of its role in HR and further studies are required to determine whether these functions can explain the RADS1B breast cancer susceptibility alleles.