Autophagy based examination of the synergistic effect of quercetin and epigallocatechin gallate on efficacy of doxorubicin in triple negative breast cancer cell line

Triple-negative breast cancer (TNBC) is an extremely heterogeneous subtype with high recurrence and mortality rates, which is especially observed in young women under the age of 45 with an increasing incidence. Due to the lack of expression of ER, PR, and HER2 receptors, there is no effective targeted treatment approach available against TNBC. Therefore, conventional chemotherapeutic agents, which have severe adverse effects, are commonly used in TNBC treatment. Autophagy, also known as self-eating, is a protective mechanism that plays a crucial role in maintaining cellular homeostasis by degrading and recycling damaged or dysfunctional organelles and protein aggregates through the action of lysosomal enzymes. This process exerts a dual role in cancer, as it can suppress tumor development while also increasing treatment resistance by supporting the survival of cancer cells under certain conditions. Therefore, there is an urgent need for therapeutic strategies in highly aggressive cancer types such as TNBC that can selectively target tumor cells and exert broad effects on multiple cellular pathways. Polyphenols are pleiotropic natural compounds with diverse biological activities such as anticancer, antioxidant and cardioprotective. In this study, the polyphenolic compounds quercetin and epigallocatechin gallate (EGCG) were combined with doxorubicin to enhance its efficacy and enable its administration at safer concentrations in the TNBC model cell line MDA-MB-231.The compounds were applied to the MDA-MB-231 cell line at different time intervals and concentrations. Their cytotoxic effects on cell viability were determined using the MTT assay and a triple combination was formed. RT-PCR was used to evaluate the expression levels of the autophagy-related genes ATG12, Ambra1, and Beclin-1 (BECN1), as well as the anti-apoptotic gene Bcl-2, following treatment with 25% and 40% doses of the triple combination. Gene expression changes were normalized to the ACTB housekeeping gene, and expression patterns at 48 and 72 hours were compared. Alterations were observed in the expression levels of key genes involved in the autophagy and apoptosis pathways. The results suggest that the synergistic effect of EGCG and quercetin may enhance the efficacy of doxorubicin in MDA-MB-231 cells, representing a potential complementary therapeutic approach for treating TNBC.