27-Hydroxycholesterol Impairs Plasma Membrane Lipid Raft Signaling as Evidenced by Inhibition of IL6–JAK–STAT3 Signaling in Prostate Cancer Cells

Abstract

We recently reported that restoring the CYP27A1–27hydroxycholesterol axis had antitumor properties. Thus, we sought to determine the mechanism by which 27HC exerts its anti–prostate cancer effects. As cholesterol is a major component of membrane microdomains known as lipid rafts, which localize receptors and facilitate cellular signaling, we hypothesized 27HC would impair lipid rafts, using the IL6–JAK–STAT3 axis as a model given its prominent role in prostate cancer. As revealed by single molecule imaging of DU145 prostate cancer cells, 27HC treatment significantly reduced detected cholesterol density on the plasma membranes. Further, 27HC treatment of constitutively active STAT3 DU145 prostate cancer cells reduced STAT3 activation and slowed tumor growth in vitro and in vivo. 27HC also blocked IL6-mediated STAT3 phosphorylation in nonconstitutively active STAT3 cells. Mechanistically, 27HC reduced STAT3 homodimerization, nuclear translocation, and decreased STAT3 DNA occupancy at target gene promoters. Combined treatment with 27HC and STAT3 targeting molecules had additive and synergistic effects on proliferation and migration, respectively. Hallmark IL6–JAK–STAT gene signatures positively correlated with CYP27A1 gene expression in a large set of human metastatic castrate-resistant prostate cancers and in an aggressive prostate cancer subtype. This suggests STAT3 activation may be a resistance mechanism for aggressive prostate cancers that retain CYP27A1 expression. In summary, our study establishes a key mechanism by which 27HC inhibits prostate cancer by disrupting lipid rafts and blocking STAT3 activation. Implications: Collectively, these data show that modulation of intracellular cholesterol by 27HC can inhibit IL6–JAK–STAT signaling and may synergize with STAT3-targeted compounds.

Role of Cholesterol and Lipid Rafts in Cancer Signaling: A Promising Therapeutic Opportunity?

“…The IL6-JAK-STAT3 pathway, known to be an important signaling pathway in prostate cancer, requires intact lipid rafts for sustaining pro-oncogenic signaling. Also in this case, disruption of lipid rafts by MβCD inhibited this pathway thus controlling prostate cancer growth (Dambal et al, 2020). In addition, it has also been reported that hypoxia, a prognostic predictor of poor clinical outcome (Vaupel et al, 2001), was able to increase cholesterol level and recruitment of Notch3 into lipid rafts.…”

The influence of low‐carbohydrate diets on the metabolic response to androgen‐deprivation therapy in prostate cancer

“…We found that LCD reversed the ADT-reduced acyl-carnitines and the increased acyl-carnitines were strongly clustered with increased ketone-related metabolites. 49,50 Together, these findings suggest a metabolic connection between ketogenesis and altered acyl-carnitines, indicating the ability of LCD to reverse these ADTinduced metabolic changes.…”

The cholesterol metabolite 27-hydroxycholesterol inhibits SARS-CoV-2 and is markedly decreased in COVID-19 patients

“…However, another oxysterol of enzymatic origin, namely 27-hydroxycholesterol (27OHC), is gaining increasing consideration as a protective molecule not only against the respiratory virus Rhinovirus, but also against a wide range of other viral infections [ [8] , [9] , [10] , [11] ]. There is clear evidence that exogenously added 27OHC accumulates in plasma membrane lipid rafts, likely affecting viral entry but also modulating cell signaling stemming from such microdomains [ 12 , 13 ].…”