The importance of regulation of respiratory chain complexes in cancer cells is becoming increasingly clear, as exemplified by the recent observations that activity of Complex I is inhibited in models of K-Ras-driven tumorigenesis [47], and that down-regulation of Complex II by the mitochondrial chaperone TRAP1 creates a pseudohypoxic phenotype that promotes tumorigenesis [48]. The gene discussed is KRAS; the disease is cancer.