Phenylbutyrate-induced apoptosis and differential expression of Bcl-2, Bax, p53 and Fas in human prostate cancer cell lines.
OBJECTIVE
To assess the mechanisms of action of phenylbutyrate (PB), an investigational chemotherapeutic agent for prostate cancer (PCa), in apoptosis induction in PCa cell lines in vitro.


METHODS
We analyzed the differential expression of different apoptosis modulators, Bcl-2, Bax, p53 and Fas, for their potential role in PB-induced apoptosis using relative quantitative flow cytometry (FCM). Both androgen-dependent (LNCaP) and androgen-independent (C-4-2, PC-3-PF and DU145) human PCa cell lines were examined.


RESULTS
PB induced apoptosis in PCa cell lines in a dose-dependent manner. Fifty percent apoptosis could be induced by 5-10 mM PB. Bcl-2 was down-regulated 30-75% and the Bax:Bcl-2 ratio elevated in apoptotic PCa cell lines regardless of their androgen dependency or p53 status. FCM revealed a heterogeneous stimulatory effect on the expression of Bax and Bcl-2 in PC3-PF cells at 0.5-2.5 mM PB. In a p53-positive cell line (DU145), p53 was repressed by 70% and Fas elevated sixfold with 10 mM PB.


CONCLUSIONS
Our data show that PB-induced PCa apoptosis is associated with the relative repression of Bcl-2 and with up-regulation of Bax and Fas proteins and that this PB-induced apoptosis is independent of p53 and androgen-dependency status of PCa cell lines.
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UroCor, Inc., Oklahoma City, Oklahoma 73104, USA. ang@uroor.com
Bales
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Veltri
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D000728:Androgens / Q000494:pharmacology; D017304:Annexin A5 / Q000276:immunology; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D015415:Biomarkers / Q000032:analysis; D004305:Dose-Response Relationship, Drug; D005455:Fluorescent Antibody Technique; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D020287:In Situ Nick-End Labeling; D008297:Male; D010654:Phenylbutyrates / Q000494:pharmacology*; D011471:Prostatic Neoplasms / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000187:drug effects* / Q000502:physiology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000187:drug effects* / Q000502:physiology; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis / Q000187:drug effects* / Q000502:physiology; D051028:bcl-2-Associated X Protein; D019014:fas Receptor / Q000096:biosynthesis / Q000187:drug effects* / Q000502:physiology
D000728:Androgens; D017304:Annexin A5; D000970:Antineoplastic Agents; C494826:BAX protein, human; D015415:Biomarkers; D010654:Phenylbutyrates; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D019014:fas Receptor