HepG2 cells with knockouts of CYP51A1, DHCR24 or SC5D from cholesterol synthesis accumulate sterols influencing distinct regulatory pathways

Abstract

Sterol intermediates of cholesterol synthesis are largely dedicated to cholesterol. Here we assess how they influence downstream gene regulatory pathways by developing knockouts (KOs) for consecutive enzymes of cholesterol synthesis in human hepatoma HepG2 cells. The KO of CYP51, DHCR24, and SC5D led to the build-up of specific sterols. The shared differentially expressed genes accounted for only 9% with regards to steroid metabolism and proliferation control, with majority of pathways changed in just one KO. The CYP51 KO cells with highly elevated 24,25-dihydrolanosterol exhibited a significant increase in G2+M phase along with enhanced cancer and cell cycle pathways, likely driven by elevated LEF1 through modulation of WNT/NFKB signalling. In contrast, SC5D and DHCR24 KO cells with elevated lathosterol or desmosterol, slowed cell proliferation and promoted apoptosis with downregulated E2F, mitosis, cell cycle transition, and enriched HNF1A tumor suppressor. These findings demonstrate that sterols from cholesterol synthesis control distinct gene regulatory pathways, while only early sterols can promote cell proliferation.