Decreased miR-206 expression in BRCA1 wild-type triple-negative breast cancer cells after concomitant treatment with gemcitabine and a Poly(ADP-ribose) polymerase-1 inhibitor.

No targeted-therapy has been established for triple-negative breast cancer accompanied by mutations in breast cancer susceptibility gene1 (BRCA1) mutation. In the present study, using BRCA1 wild-type cells (MDA-MB-231) and BRCA1-mutated cells (MDA-MB-436), we investigated miRNA expression and apoptosis on day 1 after addition of gemcitabine-alone and in combination with poly ADP-ribose polymerase-1 (PARP1) inhibitor. After drug treatment, there were significantly fewer apoptotic BRCA1 wild-type cells than BRCA1-mutated cells. Expression of miRNA-26a, -29b, -100, and -148a increased in BRCA1 wild-type cells exposed to gemcitabine-alone and in combination with the PARP1 inhibitor. The addition of PARP1 inhibitor reduced miR-206 expression in BRCA1 wild-type cells but increased it in BRCA1-mutated cells. It was suggested that miR-206 serves as a target molecule of PARP1 inhibitor combination therapy for BRCA1 wild-type triple-negative breast cancer cells.