CYCS and cancer: Further multimeric apoptosome is recruited when cytochrome c binds to APAF1, and activates pro-caspase 9.144,155 Subsequently, executioner caspase 3 and 7 are activated, initiating a caspase cascade for cancer cells apoptosis.159 Of note, MOMP and cytochrome c release are feature points of intrinsic apoptosis.