Mechanism of Brefeldin A-Induced Growth Inhibition and Cell Death in Human Prostatic Carcinoma Cells

The mechanism of growth inhibition and triggering of cell death by the antibiotic brefeldin A (BFA) was investigated in human prostatic cancer DU-145 cells. After cells were cultured with various concentrations of BFA, cell number and viability were determined at specified times. Compared with untreated cells, a drastic growth reduction (>80%) with approximately 50% cell death was observed in the cells cultured with BFA (30 ng/mL) for 72 h. Cell-cycle analysis using flow cytometry revealed that such growth inhibition was associated with approximately 85% reduction in the S-phase population, indicating the inhibition of the G(1)-S phase progression. Western blots further showed that cell-cycle-dependent kinases (cdk2 and cdk4), cyclin D(1), and p53 were all downregulated, whereas WAF1 (p21) was upregulated with BFA treatment. Possible induction of apoptosis by BFA was also assessed by TUNEL assay and by DNA analysis using agarose gel electrophoresis. The TUNEL assay demonstrated the positive staining of BFA-treated cells, and gel electrophoresis confirmed nucleosomal DNA ladder formation. Thus, these results suggest that growth inhibition of DU-145 cells by BFA is attributable mainly to a G1 cell-cycle arrest through the modulation of specific cell-cycle regulators. The accompanying cell death may follow a p53-independent apoptotic pathway.