In alignment with our previous report that cholesterol promotes cellular growth in MDA-MB-231, triple-negative, and MCF-7, ER+ breast cancer cells [31], here, we show that cholesterol enhances the proliferation of TNBC-PDX cells, and demonstrate that the growth stimulatory effect of cholesterol is ERRα-dependent in TNBC-PDX cells as in the other two breast cancer cell lines studied. This evidence concerns the gene ESR1 and breast cancer.