Interlink between cholesterol & cell cycle in prostate carcinoma

BACKGROUND & OBJECTIVES: Earlier reports have shown hypocholesterolaemia in cancer patients and high number of lipid rafts in cancer cells. The primary objective of this study was to compare the intracellular cholesterol turnover in non-cancerous (benign) prostatic hyperplasia (BPH) and carcinoma prostate (CAP) with normal prostate cells obtained from patients undergoing radical cystectomy for carcinoma bladder (sham control). METHODS: ELISA-based estimation of prostate-specific antigen (PSA), evaluation of expression of low-density lipoprotein receptor (LDLR), peripheral-type benzodiazepine receptor (PBR) and cyclin E, immunohistochemistry and confocal microscopy, measurement of integrated optical density of the diaminobenzidine (DAB)-stained immunohistograms, isolation of nucleus and cell cytoplasm from prostate tissue by ultracentrifugation followed by estimation of cholesterol spectrophotometrically in isolated nuclear and cytoplasmic fractions were performed. RESULTS: Seventy five individuals, 25 for each group (BPH n=25; CAP n=25 and sham control n=25), were included in the study. Cholesterol was increased in the cytoplasm and nucleus of the prostate cancer cells along with elevated expression of LDLR. Increased cholesterol concentration in the cell nucleus was found comparable with the increased expression of cholesterol transporter viz. PBR in the prostate tumour tissues as compared to its expression in normal prostate cells obtained from individuals undergoing radical cystectomy for carcinoma bladder. Cell cycle protein cyclin E was also highly expressed in cancer tissues. INTERPRETATION & CONCLUSIONS: The present findings along with increased expression of cell cycle protein cyclin E in the cell nucleus of the tumour tissue suggested the possibility of an intriguing role of cholesterol in the mechanism of cell cycle process of prostate cell proliferation.