Abstract
BackgroundThe alteration of lipid metabolism in cancer cells is recognized as one of the most important metabolic hallmarks of cancer. Membrane rafts defined as plasma membrane microdomains enriched in cholesterol and sphingolipids serve as platforms for signaling regulation in cancer. The main purpose of this study was to evaluate the effect of the cholesterol metabolite, 4-cholesten-3-one, on lipid metabolism and membrane raft integrity in two breast cancer cell lines, MCF-7 and MDA-MB-231. Its ability to reduce cell viability and migration has also been investigated.MethodsRT-qPCR was performed to evaluate the expression of enzymes involved in lipogenesis and cholesterol synthesis, and ABCG1 and ABCA1 transporters involved in cholesterol efflux. Its effect on cell viability and migration was studied using the MTT assay, the wound healing assay and the Transwell migration assay, respectively. The effect of 4-cholesten-3-one on membrane rafts integrity was investigated by studying the protein expression of flotillin-2, a membrane raft marker, and raft-enriched EGFR by western blot.ResultsInterestingly, we found that 4-cholesten-3-one treatment decreased mRNA expression of different enzymes including ACC1, FASN, SCD1 and HMGCR. We further demonstrated that 4-cholesten-3-one increased the expression of ABCG1 and ABCA1. We also found that 4-cholesten-3-one decreased the viability of MCF-7 and MDA-MB-231 cells. This effect was neutralized after treatment with LXR inverse agonist or after LXRβ knockdown by siRNA. As a result, we also demonstrated that 4-cholesten-3-one disrupts membrane rafts and cell migration capacity.ConclusionOur results show that 4-cholesten-3-one exerts promising antitumor activity by altering LXR-dependent lipid metabolism in breast cancer cells without increasing lipogenesis.
Highlights
The alteration of lipid metabolism in cancer cells is recognized as one of the most important metabolic hallmarks of cancer
We investigated whether 4-cholesten-3one influences lipogenesis and cholesterol biosynthesis in two breast cancer cell lines, MCF-7 and MDA-MB231
Materials Two human breast cancer cell lines, MCF-7 and MDAMB-231, and human monocyte THP-1 cells were obtained from the European Collection of Animal Cell Cultures (Salisbury, United Kingdom). 4-cholesten-3one, Dulbecco’s Modified Eagle’s Medium (DMEM), Roswell Park Memorial Institute medium (RPMI 1640), Phorbol 12-myristate 13-acetate (PMA), 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT), fetal bovine serum, penicillin-streptomycin, trypsin, glutamine, dimethyl sulfoxide (DMSO), ethanol (EtOH), bovine serum albumin (BSA), primers for qPCR, triton X-100, OptiPrepTM Density Gradient Medium, SR9238, antibodies against beta-actin and Epidermal growth factor receptor (EGFR), and 0.1% crystal violet solution were purchased from Sigma Aldrich (Saint-Quentin Fallavier, France)
Summary
The alteration of lipid metabolism in cancer cells is recognized as one of the most important metabolic hallmarks of cancer. It is known that rapidly proliferating cancer cells require a large amount of lipids for cell membrane synthesis and an increased need for energy [4]. The desaturation of newly synthesized fatty acids is catalyzed by SCD1 (stearoyl-CoA desaturase 1) which inserts a double bond in the Δ9 position of palmitic acid to produce monounsaturated fatty acids, palmitoleic acid. Another metabolic pathway of lipid metabolism is the mevalonate pathway, which synthesizes cholesterol [7]. It has been shown that the enzymes involved in lipogenesis and cholesterol biosynthesis are highly expressed in various cancer cells, such as breast and prostate cancer cells, and have recently been reported as a target for cancer treatment [6, 8]
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