Treatment of Triple Negative Cell Lines with Olaparib to Block DNA Repair.

BACKGROUND The most aggressive breast cancer is the triple negative histological type and the gold standard for its treatment is platinum salts, such as carboplatin. Due to high recurrence, there is a need to test new drugs, such as PARP inhibitors (PARPi) that induce lethality in cells with DNA damage. Olaparib is a PARPi, already used in some tumors, but not tested in canine species. Thus, the aim of this study was demonstrating the efficacy of olaparib in inhibiting DNA repair and controlling disease progression by decreasing the migration capacity of mammary tumor cells. METHODS The cell lines, CF41.Mg and MDA-MB-468, were cultured and was performed the MTT to define the best dose of carboplatin. Next, the cells were treated with 10 µM carboplatin, olaparib and with combination of both for 24 hours. PARP-1 protein and gene expression was evaluated by immunofluorescence, western blotting and qRT-PCR, respectively. The analysis of cell migration was performed in transwell chambers. RESULTS For CF41.Mg and MDA-MB-468 cell lines, there was decrease in PARP-1 protein and gene expression after treatment with carboplatin, olaparib and both in combination compared to the group without treatment (control) (p<0.05). Moreover, in both lines, reduction in invasion rate was observed after treatment with carboplatin, olaparib and when combined, compared to the control group (p<0.05). CONCLUSION Our data suggests that carboplatin and olaparib were able to block DNA repair and control the cancer invasion, especially when used in combination. The results with olaparib in the canine line are unpublished. The olaparib should be a possible agent against human breast cancer and canine mammary tumors.