An ODEs-based model of the intrinsic apoptotic pathway, mediating the apoptotic effects of some chemotherapeutic agents, was shown to accurately predict the induction of apoptotic cell death based on the concentrations of the five key proteins pro-caspases 3 and 9, second mitochondria-derived activator of caspases (SMAC), apoptotic protease-activating factor 1 (APAF-1), and X-linked-inhibitor-of-apoptosis protein (XIAP) in HeLa tumor cells [180]. The gene discussed is XIAP; the disease is neoplasm.