Ceramide analogue 5cc overcomes TRAIL-resistance by enhancing JNK activation and repressing XIAP expression in metastatic colon cancer cells

Introduction:Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is considered to be an effective apoptosis inducer due to its selectivity for tumor cells. However, many cancer cells, especially metastatic cancer cells, often exhibit resistance to TRAIL because their apoptotic pathway is impaired or their pro-survival pathway is overactivated. TRAIL-resistance is the main obstacle to current TRAIL therapy. Nowadays, ceramide analogues represent a new class of potential anticancer agents. Therefore, we hypothesized that disrupting pro-survival signaling with ceramide analogues would increase TRAIL-mediated apoptosis. Methods: MTT assay and Flow cytometry were conducted to evaluate the synergistic effect of ceramide analogue 5cc to TRAIL in metastatic colon cancer cells. Western blot was used to detect signaling proteins affected by 5cc. RNA interference was performed to analyzed the effects of specific gene on 5cc-enhanced apoptosis. Results:Ceramide analogue 5cc markedly enhanced TRAIL-induced apoptosis evidenced by increased PI/Annexin V double-positive cells and PARP cleavage in SW620 and LS411N cells. At the molecular level, 5cc significantly reduced the expression of anti-apoptotic protein X-linked inhibitor of apoptosis protein (XIAP) through the activation of C-Jun n-terminal kinase (JNK) pathway which is critically involved in sensitizing tumor cells to TRAIL/5cc combination. JNK-silenced cells exhibited a significant reversal of TRAIL/5cc-mediated apoptosis. Conclusion:Our data demonstrated that ceramide analogue 5cc overcomes TRAIL-resistance by enhancing JNK activation and repressing XIAP expression in metastatic colon cancer cells.