Cholesterol and phytosterols differentially regulate the expression of caveolin 1 and a downstream prostate cell growth-suppressor gene.
BACKGROUND
The purpose of our study was to show the distinction between the apoptotic and anti-proliferative signaling of phytosterols and cholesterol-enrichment in prostate cancer cell lines, mediated by the differential transcription of caveolin-1, and N-myc downstream-regulated gene 1 (NDRG1), a pro-apoptotic androgen-regulated tumor suppressor.


METHODS
PC-3 and DU145 cells were treated with sterols (cholesterol and phytosterols) for 72h, followed by trypan blue dye-exclusion measurement of necrosis and cell growth measured with a Coulter counter. Sterol induction of cell growth-suppressor gene expression was evaluated by mRNA transcription using RT-PCR, while cell cycle analysis was performed by FACS analysis. Altered expression of Ndrg1 protein was confirmed by Western blot analysis. Apoptosis was evaluated by real time RT-PCR amplification of P53, Bcl-2 gene and its related pro- and anti-apoptotic family members.


RESULTS
Physiological doses (16microM) of cholesterol and phytosterols were not cytotoxic in these cells. Cholesterol-enrichment promoted cell growth (P<0.05), while phytosterols significantly induced growth-suppression (P<0.05) and apoptosis. Cell cycle analysis showed that contrary to cholesterol, phytosterols decreased mitotic subpopulations. We demonstrated for the first time that cholesterols concertedly attenuated the expression of caveolin-1 (cav-1) and NDRG1 genes in both prostate cancer cell lines. Phytosterols had the opposite effect by inducing overexpression of cav-1, a known mediator of androgen-dependent signals that presumably control cell growth or apoptosis.


CONCLUSIONS
Cholesterol and phytosterol treatment differentially regulated the growth of prostate cancer cells and the expression of p53 and cav-1, a gene that regulates androgen-regulated signals. These sterols also differentially regulated cell cycle arrest, downstream pro-apoptotic androgen-regulated tumor suppressor, NDRG1 suggesting that cav-1 may mediate pro-apoptotic NDRG1 signals. Elucidation of the mechanism for sterol modulation of growth and apoptosis signaling may reveal potential targets for cancer prevention and/or chemotherapeutic intervention. Sterol regulation of NDRG1 transcription 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, Clark Atlanta University, Atlanta, GA 30314, USA. gifere@cau.edu
Equan
Anita
A
Gordon
Kereen
K
Nagappan
Peri
P
Igietseme
Joseph U
JU
Ananaba
Godwin A
GA
D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D051242:Caveolin 1 / Q000235:genetics* / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002784:Cholesterol / Q000494:pharmacology*; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism; D008297:Male; D010840:Phytosterols / Q000494:pharmacology*; D011471:Prostatic Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D000099259:N-myc Downstream-Regulated Gene 1 Protein
D051242:Caveolin 1; D018797:Cell Cycle Proteins; D002784:Cholesterol; D047908:Intracellular Signaling Peptides and Proteins; D010840:Phytosterols; D012333:RNA, Messenger; D000099259:N-myc Downstream-Regulated Gene 1 Protein; C495540:CAV1 protein, human
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