BACKGROUND: Higher intratumoral cholesterol synthesis is associated with a worse prognosis in prostate cancer. The vitamin D-regulated enzyme sterol-27-hydroxylase (CYP27A1) converts cholesterol to 27-hydroxycholesterol, potentially lowering intracellular cholesterol levels. We hypothesized that low CYP27A1 expression is associated with high cholesterol synthesis, low vitamin D signaling, and higher risk of lethal prostate cancer.
METHODS: In 404 patients from the prospective prostate cancer cohorts within the Health Professionals Follow-up Study (HPFS) and the Physicians' Health Study (PHS), we assessed intratumoral CYP27A1 expression and proxies of cholesterol synthesis using transcriptome profiling, prediagnostic plasma 25-hydroxyvitamin D (25(OH)D, n = 132) and intratumoral vitamin D receptor protein expression (VDR, n = 300). Patients were followed for metastases and prostate cancer mortality (lethal cancer; median follow-up, 15.3 years).
RESULTS: CYP27A1 expression was lower in tumors with higher Gleason grade and higher expression of cholesterol synthesis enzymes including the second rate-limiting enzyme, SQLE. We did not detect consistent associations between CYP27A1 and 25(OH)D, VDR, or CYP24A1 mRNA expression. Lower CYP27A1 was associated with higher risk of lethal cancer in both cohorts, independent of SQLE (adjusted odds ratio for lowest vs. highest quartile of CYP27A1, 2.64; 95% CI, 1.24-5.62). This association was attenuated when additionally adjusting for Gleason grade (odds ratio, 1.76; 95% CI, 0.75-4.17).
CONCLUSIONS: Low CYP27A1 expression was associated with higher cholesterol synthesis and a higher risk of lethal disease.
IMPACT: These observations further support the hypothesis that intratumoral cholesterol accumulation through higher synthesis and decreased catabolism is a feature of lethal prostate cancer.