Caffeic acid phenethyl ester-induced PC-3 cell apoptosis is caspase-dependent and mediated through the loss of inhibitors of apoptosis proteins

To investigate the effects of a novel agent, caffeic acid phethyl ester (CAPE) on nuclear factor (NF)-kappaB activation and apoptosis in the androgen-independent PC3 prostate cancer cell line. PC-3 cells were assessed for NF-kappaB activation induced by paclitaxel and tumour necrosis factor-alpha (TNF-alpha), using a p65 enzyme-linked immunosorbent assay, with or without CAPE treatment. The corresponding apoptosis was assessed with propidium iodide DNA staining using flow cytometry. The pan-caspase inhibitor Z-VAD-FMK was used to investigate the mechanism of apoptosis. Alterations in the expression of inhibitor of apoptosis proteins (IAP), cIAP-1, cIAP-2 and XIAP, were detected using western blot analysis. CAPE prevented paclitaxel and TNFalpha-mediated NF-kappaB activation. Its ability to induce apoptosis in a dose-dependent manner was associated with the loss of cIAP-1, cIAP-2 and XIAP expression. Pretreatment with Z-VAD-FMK prevented CAPE-induced apoptosis and the loss of the IAPs. CAPE is an effective inhibitor of NF-kappaB activation in PC-3 cells, but the mechanism of apoptosis, and the corresponding loss of IAP expression, is caspase-dependent.