Autocrine Growth Hormone Mediated Curcumin Resistance Overcame by Autophagy Inhibition via Bafilomycin in MDA-MB-231 and T47D Breast Cancer Cells

Curcumin, a plant derived natural compound, has anti-oxidant, anti-proliferative and apoptotic effect on various cancer cells such as prostate, colon and breast cancer. Autocrine growth hormone (GH) expression induced breast cancer invasion-metastasis has been reported in vivo and in vitro cancer models. Autophagy is a vesicule-mediated clearance mechanism and one of the handicap against drug-induced apoptotic cell death. In this study, our aim was to investigate the molecular machinery of curcumin induced apoptotic cell death under autophagy inhibition conditions in autocrine GH expressing MDA-MB-231 and T47D breast cancer cells. Although autocrine GH induced curcumin resistance, this effect was slightly prevented by time-dependent curcumin treatment in MDA-MB-231 and T47D breast cancer cells. In addition, curcumin induced autophagy vacuole formation was determined by acridine orange staining in MDA-MB-231 and T47D wt/GH+ breast cancer cells. Moreover, curcumin triggered autophagy through upregulating Beclin-1, Atg3, Atg12 expressions and LC3 cleavage in each cell line. Concomitantly, BiP, IRE1α and Calreticulin expressions were upregulated following 3 h curcumin exposure in MDA-MB-231 wt and GH+ cells. According to MTT cell viability assay, autocrine GH-mediated curcumin resistance was overcome by bafilomycin and curcumin co-treatment in MDA-MB-231 and T47D GH+ cells. Moreover, curcumin and bafilomycin co-treatment induced cell cycle arrest at G1 phase in MDA-MB-231 GH+ cells, G2/M arrest in T47D GH+ breast cancer cells. In conclusion, autocrine GH-triggered curcumin resistance was overcome by autophagy inhibition condition by bafilomycin treatment in a dose-dependent manner in MDA-MB-231 and T47D GH+ breast cancer cells.