Investigation of cytotoxic and apoptotic effects of carnosic acid and oleuropein-rich plant extracts and salicylic acid in breast cancer cells

Breast cancer is the most common type of cancer in women. Standard treatment options for the most aggressive breast cancer, triple negative, do not give very effective results due to loss of receptors and tumor homogeneity, or resistance occurs shortly. In some studies with secondary metabolites of plants and plant extracts, a decrease in cell proliferation and an increase in cell death have been observed in aggressive cancer cells. In our study, Carnosic acid and Oleuropein rich plant extracts and Salicylic acid were applied individually and in combination to MDA-MB-231 cell line representing triple negative breast cancer and fibroblast-like MCF10-A cell line as control to evaluate their cytotoxic effects. WST-1 analysis showed that the individual applications of these substances resulted in cytotoxicity (p<0.0001). In the analysis based on the IC50 value of the triple mixture formed according to the single IC50 values (50%), the application of the combined substance also resulted in cytotoxicity in MDA-MB-231 cells. Annexin V analysis confirmed that the cytotoxic effect was due to apoptosis (p<0.005). The expression changes of APAF-1, BCL-2, BAX and CDK2, which are involved in the cell apoptosis and cell cycle pathway, induced by the applied triple mixture were determined by RT-PCR method. In MDA MB 231 cells, increase in the expression of APAF-1 was observed as 17.5 fold, BCL-2 as 12.2 fold, BAX 2.7 and CDK2 as 2.1 fold. Our findings showing the effective cytotoxic potential of individual and combined applications of carnosic acid, Oleuropein-rich plant extracts and Salicylic acid in aggressive breast cancer cell line also indicate that these natural bioactive substances can be used as an adjunct and preventive to chemotherapy. Key Words: Aggressive Breast Cancer, Carnosic acid, Oleuropein, Salicylic acid, MDA-MB-231 The present work was supported by the Research Fund of Istanbul University. Project No. 32461