A novel effect of DMOG on cell metabolism: direct inhibition of mitochondrial function precedes HIF target gene expression

Abstract

Abnormal accumulation of oncometabolite fumarate and succinate is associated with inhibition of mitochondrial function and carcinogenesis. By competing with α-ketoglutarate, oncometabolites also activate hypoxia inducible factors (HIFs), which makes oncometabolite mimetics broadly utilised in hypoxia research. We found that dimethyloxalylglycine (DMOG), a synthetic analogue of α-ketoglutarate, commonly used to induce HIF signalling, inhibits O2 consumption in cancer cell lines HCT116 and PC12, well before activation of HIF pathways. A rapid suppression of cellular respiration was accompanied by a decrease in histone H4 lysine 16 acetylation and not abolished by double knockdown of HIF-1α and HIF-2α. In agreement with this, production of NADH and state 3 respiration in isolated mitochondria were down-regulated by the de-esterified DMOG derivative, N-oxalylglycine. Exploring the roles of DMOG as a putative inhibitor of glutamine/α-ketoglutarate metabolic axis, we found that the observed suppression of OxPhos and compensatory activation of glycolytic ATP flux make cancer cells vulnerable to combined treatment with DMOG and inhibitors of glycolysis. On the other hand, DMOG treatment impairs deep cell deoxygenation in 3D tissue culture models, demonstrating a potential to relieve functional stress imposed by deep hypoxia on tumour, ischemic or inflamed tissues. Indeed, using a murine model of colitis, we found that O2 availability in the inflamed colon tissue rapidly increased after application of DMOG, which could contribute to the known therapeutic effect of this compound. Overall, our results provide new insights into the relationship between mitochondrial function, O2 availability, metabolic reprogramming and associated diseases.

Metabolic reprogramming of the premalignant colonic mucosa is an early event in carcinogenesis

“…HIF1α is an important transcription factor that is overexpressed in CRC tissues and is known to increase the expression of many factors known to occur in CRC carcinogenesis that contribute to increased aerobic glycolysis as well as angiogenesis [22–25]. HIF1α expression induces the expression of multiple genes that increase glucose uptake, increase glycolysis, increase pyruvate fermentation into lactate and decrease pyruvate metabolism by the mitochondria [25].…”

“…HIF1α expression induces the expression of multiple genes that increase glucose uptake, increase glycolysis, increase pyruvate fermentation into lactate and decrease pyruvate metabolism by the mitochondria [25]. To investigate whether this increase in HIF1α is an early event in CRC field carcinogenesis, we measured the expression of HIF1α in patient rectal biopsies.…”

“…PKM2 is an isoform of this enzyme that is predominantly expressed in cancer cells, and its expression is induced by HIF1α [25]. This isoform is less effective at promoting glycolysis than PKM1 , and it is thought to promote tumorigenesis by shunting glycolytic precursors into anabolic pathways [11].…”

“…Increased glycolysis and decreased oxidative phosphorylation in CRC results in increased lactate production. Studies have demonstrated an increased expression of LDHA in CRC tissues [29], and LDHA expression can be induced by HIF1α [25, 29]. In order to determine if LDHA increases early in CRC field carcinogenesis, we measured the expression of LDHA in patient rectal biopsies.…”

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“…2 Besides energy generation, several other characteristics of mitochondria make these essential for cells. Mitochondria are also involved in signalling, 3,4 cellular differentiation 5 and cell death. …”