Cell-permeating α-ketoglutarate derivatives alleviate pseudohypoxia in succinate dehydrogenase-deficient cells

Succinate dehydrogenase (SDH) and fumarate hydratase (FH) are components of the tricarboxylic acid (TCA) cycle and tumor suppressors. Loss of SDH or FH induces pseudohypoxia, a major tumor-supporting event, which is the activation of hypoxia-inducible factor (HIF) under normoxia. In SDH- or FH-deficient cells, HIF activation is due to HIF1α stabilization by succinate or fumarate, respectively, either of which, when in excess, inhibits HIFα prolyl hydroxylase (PHD). To reactivate PHD, we focused on its substrate, α-ketoglutarate. We designed and synthesized cell-permeating α-ketoglutarate derivatives, which build up rapidly and preferentially in cells with a dysfunctional TCA cycle. This study shows that succinate- or fumarate-mediated inhibition of PHD is competitive and is reversed by pharmacologically elevating intracellular α-ketoglutarate. Introduction of α-ketoglutarate derivatives restores normal PHD activity and HIF1α levels to SDH-suppressed cells, indicating new therapy possibilities for the cancers associated with TCA cycle dysfunction.