[Effects of Olaparib, a PARP-1 Inhibitor, on Triple Negative Breast Cancer Cells with a BRCA1 Mutation].

In 2018, olaparib, a PARP inhibitor, was approved for the treatment of BRCA1/2 gene-mutation positive and HER2-negative inoperable and recurrent breast cancer; BRCA1/2 gene testing was also listed as a companion diagnostics. Here, we identified microRNAs(miRNAs) expressed after treatment with olaparib, which differed in the presence or absence of BRCA1 mutations in triple negative breast cancer(TNBC), and examined the changes in miRNAs after exposure to the combination of the PARP-1 inhibitor and a chemotherapeutic agent. After exposure to the PARP-1 inhibitor, the expression of miR-141, miR-155, miR-205, and miR-223 decreased in MDA-MB-231, HCC1143, and BT549 cells and increased more than 10 times in MDA-MB-436 cells. Moreover, the expression of miR-141 in MDA-MB-436 cells treated with the PARP-1 inhibitor together with gemcitabine increased more than 10 times; additionally, the expression of miR-205 increased more in the context of combination therapy versus single exposure to olaparib. The miR-200 family(including miR-141)and miR- 205 are known to function as ZEB1/2 targets and to act as epithelial-to-mesenchymal transition(EMT)-suppressors. Overall, these results suggest that it may be possible to recover the sensitivity of TNBC cells to chemotherapy via the suppressing EMT through the use of a PARP-1 inhibitor in the context of BRCA1 mutation.