VD and LXR agonist (T0901317) combination demonstrated greater potency in inhibiting cholesterol accumulation and inducing apoptosis via ABCA1-CHOP-BCL-2 cascade in MCF-7 breast cancer cells.

Obesity is associated with hypercholesterolemia and is a global epidemic. Epidemiological and animal studies revealed cholesterol is an essential regulator of estrogen receptor positive (ER+) breast cancer progression while inhibition of cholesterol accumulation was found to prevent breast tumor growth. Individually, vitamin D and LXR agonist T0901317 showed anticancer properties. The present study investigated the effects of vitamin D (VD, calcitriol), LXR agonist (T0901317) and a combination of VD + T0901317 on cholesterol metabolism and cancer progression in ER+ breast cancer (MCF-7) cells. VD or T0901317 alone reduced cholesterol accumulation significantly in MCF-7 cells concomitant with an induction of ABCA1 protein and gene expression compared to the control treatment. Most importantly, VD + T0901317 combination showed higher effects in reducing cholesterol levels and increasing ABCA1 protein and gene expression compared to individual treatments. Importantly, VD + T0901317 combination showed higher effects in increasing apoptosis as measured by annexin apoptosis assay, cell viability and was associated with induction of CHOP protein and gene expression. Additionally, the VD + T0901317 exerted higher effects in reducing antiapoptotic BCL-2 while increased pro-apoptotic BAX gene expression compared to the individual treatments. The present results suggest that VD and T0901317 combination may have an important therapeutic application to prevent obesity and hyperlipidemia mediated ER+ breast cancer progression.