Apoptosis induced by caffeic acid phenethyl ester in human oral cancer cell lines: Involvement of Puma and Bax activation

•CAPE suppresses neoplastic cell transformation induced by EGF and TPA.•CAPE has apoptotic effect via Puma and Bax activation in oral cancer.•Possibility of CAPE as potent apoptosis-inducing agent in oral cancer is proposed. Caffeic acid phenethyl ester (CAPE), a natural honeybee product exhibits a spectrum of biological activities including antimicrobial, anti-inflammatory, antioxidant and antitumor actions. The purpose of this research was to investigate the anticancer potential of CAPE and its molecular mechanism in human oral cancer cell lines (YD15, HSC-4 and HN22 cells). To determine the apoptotic activity of CAPE and identify its molecular targets, trypan blue exclusion assay, soft agar assay, Western blot analysis, DAPI staining, and live/dead assay were performed. CAPE significantly suppressed transformation of neoplastic cells induced by epidermal growth factor (EGF) and 12-O-tetradecanoylphorbol 13-acetate (TPA) without inhibiting growth. CAPE treatment inhibited cell growth, increased the cleavages of caspase-3 and poly (ADP-ribose) polymerase (PARP), and augmented the number of fragmented nuclei in human oral cancer cell lines. CAPE activated Bax protein causing it to undergo a conformational change, translocate to the mitochondrial outer membrane, and oligomere. CAPE also significantly increased Puma expression and interestingly Puma and Bax were co-localized. Overall, these results suggest that CAPE is a potent apoptosis-inducing agent in human oral cancer cell lines. Its action is accompanied by up-regulation of Bax and Puma proteins.