Comparison of anti-cancer effects of atorvastatin on hormone receptor- positive and triple negative breast cancers: an in-vitro Study

Abstract

Elevated serum cholesterol levels have been identified to implicate oncogenesis in breast tissues. Studying the impact of altering the cholesterol synthesis in breast tissue microenvironment in vitro as a potential anticancer treatment option holds significance. Research problem: Can widely prescribed statins exert anticancer effects and if so, differently on different breast cancer (BC) cells in vitro? A concentration series of active ingredient atorvastatin calcium (10-160 μmoldm-3) was prepared in complete cell culture media. Prepared concentrations were treated on seeded triple-negative MDA-MB-231 and hormone-receptors positive MCF7 BC cells, and nontumorigenic mammary epithelial cell line MCF10A (n=6) in 96 well plates separately. The treated cells were incubated at 37° for 24, 48 and 72 hours. The cell viability was assessed with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Dose effect curves were derived and half maximal inhibitory concentrations (IC₅₀) of atorvastatin were calculated at 24, 48 and 72 hours, compared to negative controls. Induced apoptosis was assessed with acridine orange ethidium bromide (AO/EB) staining. The IC₅₀ derived from the dose effective curves at 24, 48, and 72 hours were as follows; for MDA-MB-231; 125.8, 33.9 and 9.5 μmoldm⁻³, for MCF7; 117.0, 98.5, and 78.3 μmoldm⁻³ and for MCF10A; 177.9, 90.6 and 13.9 μmoldm⁻³,respectively. At 24 hours atorvastatin exerts more cytotoxicity on MCF7 cells than on MDA- MB-231 cells. The IC₅₀ decreased with prolonged incubation in all the cell lines. However, the decrease in IC₅₀ was more prominent in MDA-MB-231 cells than in MCF7 indicating more cytotoxicity to triple-negative BC cells in a time-dependent manner. In the AO/EB staining cytoplasmic blebbing, nuclear fragmentation, and loss of membrane integrity were noted at the IC₅₀ concentrations at 24-hour incubation confirming that the loss of cell viability is due to induced apoptosis. The anticancer effect exerted by atorvastatin on hormone receptor-positive BC cells is higher than the hormone receptor-negative BC cells, at 24 hours.