These proteins regulate the mitochondrial membrane to secrete cytochrome C (Cyt-C), and the interaction between Cyt-C, apoptotic protease activating factor 1 (Apaf-1), and caspase-9 forms a multimeric complex called the apoptosome, which in turn induces the activation of caspase-9 and caspase-3, thereby eliciting apoptosis of cancer cells [52]. Here, CASP9 is linked to cancer.