High-throughput pharmaceutical screen involving BRCA2-deficent vs. BRCA2-proficient mouse mammary tumor cell lines identified alkylating agents (chlorambucil, melphalane, nimustine) as the most potent and specific inhibitors of cell growth; differential inhibition was also registered for carboplatin, camptothecin and ellipticine. BRCA2-deficient mammary tumors, either transplanted or growing in genetically engineered mice, demonstrated high sensitivity to alkylating compounds. Synergistic interaction between alkylators and olaparib was observed both in vitro and in vivo. Here, BRCA2 is linked to breast cancer.