The mitochondrial chaperone TRAP1 promotes neoplastic growth by inhibiting succinate dehydrogenase

Cancer is a highly heterogeneous and complex disease, whose development requires a reorganization of cell metabolism. Most tumor cells downregulate mitochondrial oxidative phosphorylation and increase the rate of glucose consumption and lactate release, independently of oxygen availability (the Warburg effect). This metabolic rewiring is believed to favour tumor growth and survival. However the molecular mechanisms that inhibit oxidative phosphorylation (OXPHOS) during neoplastic progression are only partially understood. Within this context, we studied TRAP1, a conserved chaperone of the Heat Shock Protein 90 (HSP90) family, localized mainly in the mitochondrial matrix and whose expression is induced in the majority of tumor types. We found that TRAP1 is associated to succinate dehydrogenase (SDH), the Complex II of the respiratory chain. We observed in different tumor cell models that TRAP1 diminished in vivo tumor cell respiration by inhibiting the succinate:coenzyme Q reductase (SQR) activity of Complex II. This Complex II inhibition was further enhanced in TRAP1-expressing cells that progressed through a focus forming assay (in vitro tumorigenesis assay), causing an accumulation of succinate that led to the stabilization of the pro-neoplastic transcription factor HIF1alpha thus favouring the metabolic switch necessary for tumor growth and progression. In fact, we observe in vitro e in vivo tumorigenesis only in TRAP1 expressing cells ; Il cancro è una malattia altamente complessa ed eterogenea, il cui sviluppo richiede una riorganizzazione del metabolismo cellulare. La maggior parte delle cellule tumorali diminuisce la fosforilazione ossidativa mitocondriale e aumenta invece la quantità di glucosio consumato e di produzione di lattato, in maniera completamente indipendente dalla disponibilità di ossigeno. Questo fenomeno è noto come Effetto Warburg. Si pensa che questa riprogrammazione metabolica favorisca la crescita e la sopravvivenza del tumore. Comunque sono solo parzialmente noti i meccanismi ...