Resistance to hypoxia-induced necroptosis is conferred by glycolytic pyruvate scavenging of mitochondrial superoxide in colorectal cancer cells

Abstract

Cancer cells may survive under oxygen and nutrient deprivation by metabolic reprogramming for high levels of anaerobic glycolysis, which contributes to tumor growth and drug resistance. Abnormally expressed glucose transporters (GLUTs) are colocalized with hypoxia (Hx) inducible factor (HIF)1α in peri-necrotic regions in human colorectal carcinoma. However, the underlying mechanisms of anti-necrotic resistance conferred by glucose metabolism in hypoxic cancer cells remain poorly understood. Our aim was to investigate signaling pathways of Hx-induced necroptosis and explore the role of glucose pyruvate metabolite in mechanisms of death resistance. Human colorectal carcinoma cells were Hx exposed with or without glucose, and cell necroptosis was examined by receptor-interacting protein (RIP)1/3 kinase immunoprecipitation and 32P kinase assays. Our results showed increased RIP1/3 complex formation and phosphorylation in hypoxic, but not normoxic cells in glucose-free media. Blocking RIP1 signaling, by necrostatin-1 or gene silencing, decreased lactodehydrogenase (LDH) leakage and plasma membrane disintegration. Generation of mitochondrial superoxide was noted after hypoxic challenge; its reduction by antioxidants inhibited RIP signaling and cell necrosis. Supplementation of glucose diminished the RIP-dependent LDH leakage and morphological damage in hypoxic cells, whereas non-metabolizable sugar analogs did not. Hypoxic cells given glucose showed nuclear translocation of HIF1α associated with upregulation of GLUT-1 and GLUT-4 expression, as well as increase of intracellular ATP, pyruvate and lactate levels. The glucose-mediated death resistance was ablated by iodoacetate (an inhibitor to glyceraldehyde-3-phosphate dehydrogenase), but not by UK5099 (an inhibitor to mitochondrial pyruvate carrier), suggesting that glycolytic pathway was involved in anti-necrotic mechanism. Lastly, replacing glucose with cell-permeable pyruvate derivative also led to decrease of Hx-induced necroptosis by suppression of mitochondrial superoxide in an energy-independent manner. In conclusion, glycolytic metabolism confers resistance to RIP-dependent necroptosis in hypoxic cancer cells partly through pyruvate scavenging of mitochondrial free radicals.

The recent progress of the mechanism and regulation of tumor necrosis in colorectal cancer

“…The main cause of apoptosis deficiency is the decreased ATP level that a determinate factor for the conversion from apoptosis to necrosis. When the ATP loss to certain degree, apoptotic program was inhibited and stably followed by necrosis also proposed that glycolytic pyruvate was able to resistant hypoxia-induced necrosis by scavenging of mitochondrial superoxide (Huang et al 2013).…”

Eritoran Suppresses Colon Cancer by Altering a Functional Balance in Toll-like Receptors That Bind Lipopolysaccharide

“…Human colon adenocarcinoma HT29 and Caco-2 cells were exposed to LPS or eritoran for 48 or 24 hours, and the effects of this exposure on cell proliferation and cell death, respectively, were measured (20,35). In some experiments, cells were pretreated with inhibitors 30 minutes prior to challenge.…”

BIRC5/Survivin as a target for glycolysis inhibition in high-stage neuroblastoma

“…However, Q-VD completely failed to increase viability of SH-EP/Surv or SH-EP/Ctr cells, which excludes apoptosis as the main cell death form in response to 2DG treatment (Figure 2a and Supplementary Figure S4). As high glycolytic activity affects necroptosis, 29 we next tested whether necroptosis is involved in 2DG-induced cell death. Therefore, the cells were incubated with Necrostatin-1, a potent inhibitor of RIP-1, the critical regulator of necroptosis.…”