Identification of a tumor-promoter cholesterol metabolite in human breast cancers acting through the glucocorticoid receptor

Significance

Cholesterol and its transformation into cholesterol-5,6-epoxides (5,6-EC) was long suspected as contributing to breast cancer (BC) pathogenesis, before it was found that 5,6-EC metabolism controls BC development and is deregulated in breast cancers. Herein, we studied in tumor cells and human samples how 5,6-EC metabolism deregulation promotes tumor progression. We have discovered a pathway in BCs producing an oncometabolite derived from 5,6-EC, through the action of the cortisol-inactivating enzyme, and identified the glucocorticoid receptor (GR) as the target mediating its proliferative effects. Inhibition of its production or GR significantly blocked its action on BC progression. Thus, targeting this oncometabolism and GR represents a new opportunity for therapeutic intervention in BCs and potentially other cancers presenting such deregulations.

Abstract

Breast cancer (BC) remains the primary cause of death from cancer among women worldwide. Cholesterol-5,6-epoxide (5,6-EC) metabolism is deregulated in BC but the molecular origin of this is unknown. Here, we have identified an oncometabolism downstream of 5,6-EC that promotes BC progression independently of estrogen receptor α expression. We show that cholesterol epoxide hydrolase (ChEH) metabolizes 5,6-EC into cholestane-3β,5α,6β-triol, which is transformed into the oncometabolite 6-oxo-cholestan-3β,5α-diol (OCDO) by 11β-hydroxysteroid-dehydrogenase-type-2 (11βHSD2). 11βHSD2 is known to regulate glucocorticoid metabolism by converting active cortisol into inactive cortisone. ChEH inhibition and 11βHSD2 silencing inhibited OCDO production and tumor growth. Patient BC samples showed significant increased OCDO levels and greater ChEH and 11βHSD2 protein expression compared with normal tissues. The analysis of several human BC mRNA databases indicated that 11βHSD2 and ChEH overexpression correlated with a higher risk of patient death, highlighting that the biosynthetic pathway producing OCDO is of major importance to BC pathology. OCDO stimulates BC cell growth by binding to the glucocorticoid receptor (GR), the nuclear receptor of endogenous cortisol. Interestingly, high GR expression or activation correlates with poor therapeutic response or prognosis in many solid tumors, including BC. Targeting the enzymes involved in cholesterol epoxide and glucocorticoid metabolism or GR may be novel strategies to prevent and treat BC.