TRAP1 (HSP75 or HSC5 [41])—a 75 kDa member of the HSP90 subfamily—is an ATP-utilizing molecular chaperone localized to mitochondria and participating in the regulation of proliferation, apoptosis, differentiation, and energetic metabolism in both normal and cancer cells and non-stem ones [42,61,258]. The gene discussed is HSP90AB1; the disease is cancer.