Differential effects of cholesterol and phytosterols on cell proliferation, apoptosis and expression of a prostate specific gene in prostate cancer cell lines.
BACKGROUND
The purpose of our study was to show the apoptotic and anti-proliferative effects of phytosterols as distinct from cholesterol effects on prostate cancer cell lines, and also their differential expression of caveolin-1, and a prostate specific gene, PCGEM1.


METHODS
PC-3 and DU145 cells were treated with sterols (cholesterol and phytosterols) for 48h, followed by trypan blue dye exclusion measurement of cytotoxicity and MTT cell proliferation assays, respectively. Cell cycle analysis was carried out microscopically, and by propidium iodide uptake using flow cytometry. Sterol induction of oncogenic gene expression was evaluated by RT-PCR. Apoptotic cells were identified by immunocytochemistry using DNA fragmentation method, and by annexin V adhesion using flow cytometry.


RESULTS
Physiological doses (16microM) of these sterols were not cytotoxic in these cells. Cholesterol-enrichment promoted mitosis (54 and 61% by microscopy; 40.8 and 34.08% by FACS analysis in PC-3 and DU145, respectively) and cell growth (P<0.05), while phytosterols suppressed mitosis (29 and 35% by microscopy; 27.71 and 17.37% by FACS analysis in PC-3 and DU145, respectively), and significantly induced tumor-suppression (P<0.05) and apoptosis. We demonstrated for the first time that cholesterols upregulated the expression of PCGEM1 even in androgen-insensitive prostate cancer cell lines. Phytosterols reversed this effect, while upregulating the expression of caveolin-1, a known mediator of androgen-dependent proto-oncogene signals that presumably control growth and anti-apoptosis.


CONCLUSIONS
Phytosterol inhibition of PCGEM1 and cell growth and the overexpression of caveolin-1, suggests that poor disease prognosis anchors on the ability of caveolin-1 to regulate downstream oncogene(s) and apoptosis genes. Sterol intake may contribute to the disparity in incidence of prostate cancer, and elucidation of the mechanism for modulation of growth and apoptosis signaling may reveal potential targets for cancer prevention and/or chemotherapeutic intervention. Sterol regulation of PCGEM1 expression suggests its potential as biomarker for prediction of neoplasms that would be responsive to chemoprevention by phytosterols.
Ifere
Godwin O
GO
Department of Biological Sciences, and Center for Cancer Research and Therapeutic Development, Clark Atlanta University, Atlanta, GA 30314, USA. gifere@cau.edu
Barr
Erika
E
Equan
Anita
A
Gordon
Kereen
K
Singh
Udai P
UP
Chaudhary
Jaideep
J
Igietseme
Joseph U
JU
Ananaba
Godwin A
GA
D017209:Apoptosis / Q000187:drug effects; D051242:Caveolin 1 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism / Q000494:pharmacology*; D005434:Flow Cytometry; D015870:Gene Expression / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008297:Male; D010840:Phytosterols / Q000378:metabolism / Q000494:pharmacology*; D011471:Prostatic Neoplasms / Q000235:genetics* / Q000378:metabolism*; D000090063:Proto-Oncogene Mas; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism
D051242:Caveolin 1; C000715470:MAS1 protein, human; C416084:PCGEM1 non-coding RNA, human; D010840:Phytosterols; D000090063:Proto-Oncogene Mas; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; D002784:Cholesterol