Analysis of the effectiveness of co-treatment of PARP1 inhibitors with S6Ks inhibitors as a therapeutic strategy against breast Cancer cells

Abstract

According to the National Cancer Institute (INCA) breast cancer is the most common cancer among women in the world; in 2020, 2.3 million new cases were estimated. Regarding treatment, it is known that the use of PARP1 inhibitors (Poly (ADP-ribose) Polymerase 1) for individuals with a BRCA1/2 mutation is a relevant therapeutic strategy based on synthetic lethality. S6K1/2 proteins mediate the mTOR pathway response and are related to cell growth, proliferation, protein synthesis, and other nutrient-mediated cellular responses. In breast cancer, increased activity of S6Ks is related to the development of resistance to chemotherapeutics, including PARP1 inhibitors. However, they are poorly studied as a target for cancer treatment. Thus, inhibitors of S6Ks combined with PARP1 may be a promising strategy for the treatment of breast cancer. This study aims to test the co-treatment of PARP1 and S6Ks inhibitors in different breast cancer cell lines, analyzing the response of the mTOR/S6Ks pathway and the efficacy of the treatment. The cell lines MCF7, SKBR3, MDA-MB-231, and HCC1937 will be used, which consist of breast cancer cells with different characteristics related to tumor classification and the presence of mutations, such as in the BRCA1 gene. The cells will be treated with PARP1 inhibitors (Olaparib and AG14361) and S6K1/2 inhibitor (PF-4708671) alone and in co-treatment with the two inhibitors. Efficacy will be evaluated through cell growth and viability assays, such as MTT and clonogenic assay, in addition to the analysis of the mTOR/S6Ks pathway and related cellular pathways, through Western-blotting, RT-PCR, and immunofluorescence. (AU)