Introduction: Breast cancer is the most common tumor type among women and has a high mortality rate, which is associated with late detection of the disease and treatment failure due to the acquisition of resistance to protocol treatments. It is known that a variety of antitumor drugs are capable of inducing chemoresistance by activating DNA repair pathways. Among these, the PARPs are involved in the recognition and repair of simple-strand breaks. As a consequence, new drugs such as PARP inhibitors (olaparib), are being investigated as potential therapeutic targets in cancer, as an alternative to evade the resistance of tumor cells to chemotherapeutic agents, such as those in the class of platinum salts. In this context, the aim of this study was to evaluate the PARP expression after olaparib tratament with in mammary tumor cell lines. Materials and Methods: Mammary tumor cell lines MDA-MB-468 and CF41 was cultured in DMEM high glucose culture medium, at 37°C in 5% CO2. Cell viability was measured by MTT assay after treatment with different concentrations of carboplatin. Once stablished the concentration of 10µM for carboplatin and 10µM of olaparib, the protein and gene expression of PARP-1 were detected by immunofluorescence and real time PCR, respectively. Results: There was a significantly decrease of cell viability after treatment with different concentrations of carboplatin in 24 hours. Both PARP-1 protein and gene expression significantly decreased after treatment with carboplatin and olaparib. In some cases, the treatment action was potentiated when performed in combination. Conclusion: Our results suggest the efficacy of olaparib in controlling the mechanism of DNA repair activated by PARPs in human and canine breast cancer cells.

Citation Format: Marina Gobbe Moschetta-Pinheiro, Jucimara Colombo, Murilo de Souza Tuckumantel, Gabriela Karam Rebolho, Debora Aparecida Zuccari. Regulation of PARP-1 expression in mammary tumor cell lines after treatment with olaparib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB113.