Mechanisms
Knocking down CETP shrinks triple-negative breast cancer xenografts by 86% and restores tamoxifen sensitivity in resistant cells (IUBMB Life 2024)
Original title: Cholesteryl ester transfer protein knock-down in conjunction with a cholesterol-depleting agent decreases tamoxifen resistance in breast cancer cells
Cancer cells rely on a cholesterogenic phenotype, accumulating and synthesising cholesterol to support proliferation and survival, and CETP had previously been implicated in breast cancer aggressiveness without a clear mechanism. Genetic knock-down of CETP cut proliferation by more than 50% in both oestrogen-receptor-positive (MCF7) and triple-negative (MDA-MB-231) breast cancer cell lines. Combining CETP knock-down with tamoxifen (5 uM) and the cholesterol-depleting agent acetyl plumbagin (5 uM) increased apoptosis two to threefold in both lines, alongside reduced intracellular cholesteryl ester, lipid rafts and lipid droplets. Gene expression analysis showed CETP knock-down downregulated cholesterol biosynthesis and drug-resistance genes in MCF7 cells, while in MDA-MB-231 cells it reduced resistance through increased cholesterol efflux gene expression. In a pilot xenograft study, CETP knock-down shrank triple-negative tumour growth by 86%. Genetic knock-down, not a pharmacological CETP inhibitor, but a mechanistic case for CETP as a breast cancer drug target.
Original abstract
The cholesterogenic phenotype, encompassing de novo biosynthesis and accumulation of cholesterol, aids cancer cell proliferation and survival. Previously, the role of cholesteryl ester (CE) transfer protein (CETP) has been implicated in breast cancer aggressiveness, but the molecular basis of this observation is not clearly understood, which this study aims to elucidate. CETP knock-down resulted in a >50% decrease in cell proliferation in both 'estrogen receptor-positive' (ER+; Michigan Cancer Foundation-7 (MCF7) breast cancer cells) and 'triple-negative' breast cancer (TNBC; MDA-MB-231) cell lines. Intriguingly, the abrogation of CETP together with the combination treatment of tamoxifen (5 μM) and acetyl plumbagin (a cholesterol-depleting agent) (5 μM) resulted in twofold to threefold increase in apoptosis in both cell lines. CETP knockdown also showed decreased intracellular CE levels, lipid raft and lipid droplets in both cell lines. In addition, RT2 Profiler PCR array (Qiagen, Germany)-based gene expression analysis revealed an overall downregulation of genes associated in cholesterol biosynthesis, lipid signalling and drug resistance in MCF7 cells post-CETP knock-down. On the contrary, resistance in MDA-MB-231 cells was reduced through increased expression in cholesterol efflux genes and the expression of targetable surface receptors by endocrine therapy. The pilot xenograft mice study substantiated CETP's role as a cancer survival gene as knock-down of CETP stunted the growth of TNBC tumour by 86%. The principal findings of this study potentiate CETP as a driver in breast cancer growth and aggressiveness and thus targeting CETP could limit drug resistance via the reduction in cholesterol accumulation in breast cancer cells, thereby reducing cancer aggressiveness.
Summary written by cetpinhibition.org from the published abstract; figures as published. Page updated 18 August 2026. Methods.