Cellular communication network 1 promotes CASP2 mRNA expression but suppresses its protein translation in esophageal adenocarcinoma

Induction of apoptosis in tumor cells is one of the best ways to cure cancer. While most apoptosis requires a chain of caspase activation, CASP2 can do this all by itself. The matricellular protein cellular communication network 1 (CCN1) is known for supporting some cancer growth but suppressing others. Esophageal adenocarcinoma (EAC) belongs to the latter. CCN1 is capable of inducing TRAIL-mediated apoptosis in EAC cells. This study found that CCN1 upregulated CASP2 transcription but not its translation in EAC cells because, on one hand, CCN1 downregulated p16 and p21, which increased RB1 phosphorylation allowing E2F1 to transcribe more CASP2 mRNA, on the other hand, CCN1 also upregulated HuR, which is bound to CASP2 mRNA species and blocked its protein translation. As a result, CASP2 contributed nothing to CCN1-induced EAC cell apoptosis. On the contrary, CCN1 promoted CASP3, not only in its transcription but also in its translation and activation, which established the basis for CCN1-induced EAC cell apoptosis.