Exogenous pyruvate facilitates cancer cell adaptation to hypoxia by serving as an oxygen surrogate

Abstract

Molecular oxygen is the final electron acceptor in cellular metabolism but cancer cells often become adaptive to hypoxia, which promotes resistance to chemotherapy and radiation. The reduction of endogenous glycolytic pyruvate to lactate is known as an adaptive strategy for hypoxic cells. Whether exogenous pyruvate is required for hypoxic cell proliferation by either serving as an electron acceptor or a biosynthetic substrate remains unclear. By using both hypoxic and ρ0 cells defective in electron transfer chain, we show that exogenous pyruvate is required to sustain proliferation of both cancer and non-cancer cells that cannot utilize oxygen. Particularly, we show that absence of pyruvate led to glycolysis inhibition and AMPK activation along with decreased NAD+ levels in ρ0 cells; and exogenous pyruvate increases lactate yield, elevates NAD+/NADH ratio and suppresses AMPK activation. Knockdown of lactate dehydrogenase significantly inhibits the rescuing effects of exogenous pyruvate. In contrast, none of pyruvate-derived metabolites tested (including acetyl-CoA, α-ketoglutarate, succinate and alanine) can replace pyruvate in supporting ρ0 cell proliferation. Knockdown of pyruvate carboxylase, pyruvate dehydrogenase and citrate synthase do not impair exogenous pyruvate to rescue ρ0 cells. Importantly, we show that exogenous pyruvate relieves ATP insufficiency and mTOR inhibition and promotes proliferation of hypoxic cells, and that well-oxygenated cells release pyruvate, providing a potential in vivo source of pyruvate. Taken together, our data support a novel pyruvate cycle model in which oxygenated cells release pyruvate for hypoxic cells as an oxygen surrogate. The pyruvate cycle may be targeted as a new therapy of hypoxic cancers.

Exogenous pyruvate represses histone gene expression and inhibits cancer cell proliferation via the NAMPT–NAD+–SIRT1 pathway

“…As a glycolytic intermediate metabolite, pyruvate is formed from phosphoenolpyruvate (PEP) by pyruvate kinase (PKM1/2) and then converted to lactate and acetyl-CoA by the lactate dehydrogenase (LDH) complex and the pyruvate dehydrogenase complex (PDC), respectively (Figure 2A) (30). Pyruvate treatment had no significant effect on the expression of LDH subunit, LDHA and PDC critical subunit, PDHA-1 (Supplementary Figure S3A).…”

Extrinsic acidosis suppresses glycolysis and migration while increasing network formation in pulmonary microvascular endothelial cells

“…One day after treatments with different conditions, cells were collected and subjected to immunoblot analysis as previously described (31). Primary antibodies for CA IX (M75, 1:700 dilution) (27) and GAPDH (1:1,000 dilution) were obtained from BioScience Slovakia (Bratislava, Slovakia) and Cell Signaling (Danvers, MA), respectively, and antibodies for Na ϩ /H ϩ exchanger-1 (NHE-1, 1:200 dilution) (3), hexokinase-1 (HXK I, 1:200 dilution) (42), pyruvate kinase M-type (PKM, 1:500 dilution) (44), pyruvate dehydrogenase E1␣ subunit (PDH-E1␣, 1:300 dilution) (45), and N-cadherin (1:200 dilution) (34) were obtained from Santa Cruz Biotechnology (Dallas, TX).…”

Unique Metabolic Adaptations Dictate Distal Organ-Specific Metastatic Colonization

“…At first sight, this finding might seem contradictory, considering that glutamine is a very abundant carbon source in the lungs (van den Heuvel et al, 2012). However, it is now known that defects in the mitochondrial electron transport chain can be alleviated via exogenous addition of pyruvate, which serves as an electron acceptor to replenish NAD + pools for TCA anaplerosis (Yin et al, 2016). Taking into consideration the added strain of high oxygen and limited glucose on the mitochondrial electron transport chain that upregulation of PGC-1α may not always fully ameliorate, the ability of lung metastases to increase pyruvate uptake might provide them with the ability to cope with an imbalance of reducing equivalents caused by a dysfunctional electron transport chain (Figure 2).…”