Involvement of de novo ceramide synthesis in gamma‐tocopherol and gamma‐tocotrienol‐induced apoptosis in human breast cancer cells

Scope This study further examines mechanisms involved in the pro‐apoptotic action of gamma‐tocopherol (γ T ) and gamma‐tocotrienol (γ T 3) in human breast cancer cell lines. Methods and results γ T upregulates phospho‐ JNK (p JNK ), CCAAT /enhancer‐binding protein homologous protein ( CHOP ), and death receptor‐5 ( DR 5) protein expression as detected by W estern blot assays. si RNA knockdown of JNK , CHOP , or DR 5 shows that γ T ‐induced apoptosis is JNK / CHOP / DR 5 signaling dependent, which is similar to γ T 3‐mediated apoptotic signaling. Furthermore, both γ T and γ T 3 induce increased levels of cellular ceramides and dihydroceramides as determined by LC ‐ MS / MS analyses. Inhibition of de novo ceramide synthesis using chemical inhibitors blocked the ability of γ T and γ T 3 to induce apoptosis as detected by Annexin V ‐ FITC / PI assay and to activate JNK / CHOP / DR 5 pro‐apoptotic signaling thereby demonstrating the involvement of de novo ceramide synthesis in γ T ‐ and γ T 3‐induced apoptosis. Conclusion Taken together, data show that both γ T and γ T 3 induce apoptosis via de novo ceramide synthesis dependent activation of JNK / CHOP / DR 5 pro‐apoptotic signaling.