(509g) The Role of Reductive Carboxylation in Warburg-Like Renal Cancer Cells

Mammalian cells must consume glucose and glutamine to fuel  biosynthetic processes necessary for growth. Acetyl coenzyme A (AcCoA) is a major precursor for lipid synthesis

being primarily generated from glucose-derived pyruvate through the citrate shyttle and ATP citrate lyase (ACLY) in the cytosol. We have shown that hypoxic

and "pseudo-hypoxic" renal cancer cells switch to reductive carboxylation (RC) of a-ketoglutarate as the primary route of AcCoA and de novo fatty acids synthesis. To study the 

mechanism(s) of RC induction in hypoxia, we investigated the role of hypoxia-inducible factors (HIF) in renal cell carcinoma (RCC) cells deficient in the 

von Hippel-Lindau (VHL) tumor suppressor, which express HIF consititutively even under normoxia conditions (Warburg-like cells).  To this end, we took advantage of a panel

of disease associated VHL mutants that differ in their ability to bind and degrade HIF. Using 13C glucose and glutamine tracers, we show that HIF expression is necessary and

sufficient to promote RC in RCC cells under normoxia. Using [1–13C] glutamine, we monitored for the first time the in vivo RC activity in VHL-deficient tumors

growing as xenografts in mice. Furthermore, HIF expression renders VHL-deficient cells sensitive to glutamine deprivation in vitro, and systemic administration of glutaminase inhibitors

suppresses the growth of RCC cells as mice xenografts. These observations may lead to viable therapeutic strategies targeting the hypoxic compartment of RCC tumors.