Synergistic effect of Erythrina variegata L. and tamoxifen against the growth of breast cancer cells

Breast cancer is the most common malignancy and the second leading cause of death in women. While tamoxifen (TAM) remains to be a first-line agent for prevention and treatment of estrogen-receptor (ER) positive breast tumors, TAM resistance represents one of the biggest clinical challenges in breast cancer therapy. Therefore, there has been growing interest in the identification of novel agents including those of plant origin that enhance the TAM sensitivity of breast cancer cells. In the present study, we aimed to evaluate the synergistic effect of Erythrina variegata extract (EVE) and TAM on the suppression of breast cancer cell growth using MCF-7 cell model and conventional bioassays such as MTT and colony formation assay, cell cycle analysis, and immunocytochemistry. Interestingly, MTT assay in combination with Chou-Talalay analysis demonstrated the potent synergism between EVE and tamoxifen against MCF-7 cell survival. Additionally, co-treatment of MCF-7 cells with EVE and TAM more significantly suppressed colony formation, cell cycle progression, and the nuclear expression of proliferative marker Ki67 compared to TAM alone. These findings imply that EVE potentiates the anti-proliferative effect of TAM in MCF-7 breast cancer cells and may become a promising agent in the treatment of ER positive breast cancer.