MUC16 mucin (CA125) attenuates TRAIL-induced apoptosis by decreasing TRAIL receptor R2 expression and increasing c-FLIP expression

作者：Matte Isabelle; Lane Denis; Boivin Marianne; Rancourt Claudine; Piche Alain^*

来源：BMC Cancer, 2014, 14(1): 234.

DOI：10.1186/1471-2407-14-234

• MUC16/CA125
• Mucins
• Death receptors
• TRAIL
• Ovarian cancer
• Apoptosis

Background: MUC16 (CA125) is a large transmembrane mucin protein (%26gt; 200 kDa) aberrantly expressed in approximately 80% of human epithelial ovarian cancers (EOC). MUC16 expression in EOC cells is associated with increased tumorigenesis and inhibiton of genotoxic drug-induced apoptosis. However, the mechanism by which MUC16 mediates these effects is unknown. In the present study, we investigated the mechanisms by which MUC16 attenuates TRAIL-induced apoptosis. %26lt;br%26gt;Methods: MUC16 expression was down-regulated by stably expressing an anti-MUC16 single-chain antibody (scFv) targeted to the endoplasmic reticulum (ER), which prevents cell surface localization of MUC16 in OVCAR3 cells. We also generated a MUC16 C-terminal domain (MUC16CTD) construct that was stably expressed in MUC16 negative SKOV3 cells. %26lt;br%26gt;Results: We show that MUC16 attenuates apoptosis, activation of caspase-8 and mitochondria activation in EOC cells in response to TRAIL. MUC16 decreases TRAIL receptor R2 (DR5) expression and inhibits pro-caspase-8 activation at the death-inducing signaling complex (DISC). MUC16CTD expression is sufficient to attenuate the TRAIL signaling cascade. MUC16 knockdown decreases caspase-8 inhibitor cFLIP mRNA levels, increases cFLIP degradation, and consequently increases TRAIL-induced apoptosis. Down-regulation of cFLIP following treatment of MUC16-expressing OVCAR3 cells with cFLIP siRNA also increases TRAIL-induced apoptosis. %26lt;br%26gt;Conclusions: These findings indicate that MUC16 protects EOC cells against TRAIL-induced apoptosis through multiple mechanisms including the blockade of TRAIL R2 expression and the regulation of cFLIP expression at both the transcriptional and the protein level.