Brefeldin A-induced apoptosis in prostatic cancer DU-145 cells: a possible p53-independent death pathway.

OBJECTIVE: To investigate the growth inhibitory mechanism of brefeldin A (BFA), an antiviral antibiotic, in androgen-independent prostatic cancer DU-145 cells.

MATERIALS AND METHODS: The inhibitory effects of BFA (30 ng/mL) on cell growth were monitored by cell counting and viability tests after specified exposures. Flow cytometry and western immunoblot analysis were performed to examine the effects of BFA on the cell cycle and on specific growth regulators. The possible induction of apoptosis by BFA was further assessed by in situ hybridization (ISH) assay and by qualitative DNA analysis using agarose-gel electrophoresis.

RESULTS: Cell growth was completely inhibited with BFA (30 ng/mL), accompanied by 40-50% cell death. Cell cycle analysis revealed that this growth inhibition coincided with an 85% reduction in the S-phase cell population. Western blots showed that the expression of cell cycle-dependent kinases (cdk2 and cdk4), cyclin D1 and p53 was significantly reduced, while WAF1 was increased, after BFA treatment. Apoptosis was confirmed by both the ISH assay, which showed the characteristic brownish staining of BFA-treated cells, and by DNA analysis, which revealed the internucleosomal DNA ladder.

CONCLUSION: BFA-induced growth inhibition in DU-145 cells is primarily due to the modulation of specific G1 cell-cycle regulators, blocking the G1-S phase progression. Such a growth arrest ultimately results in apoptosis, presumably through a p53-independent pathway.