A redox-dependent mechanism for AMPK dysregulation interrupts metabolic adaptation of cancer under glucose deprivation

Abstract

Accelerated aerobic glycolysis is a distinctive metabolic property of cancer cells that confers dependency on glucose for survival. However, the selective therapeutic targeting of this vulnerability has yielded mixed results owing to the different sensitivities of each cancer type to glucose removal and lack of insight into the underlying mechanisms of glucose deprivation-induced cell death. Here, we screened multiple cell lines to determine their sensitivities to glucose deprivation and found that the cell lines most sensitive to glucose deprivation failed to activate AMPK, a major regulator of metabolic adaptation, resulting in metabolic catastrophe. Notably, glucose deprivation-induced AMPK dysregulation and rapid cell death were observed only in cancer cell lines with high expression of cystine/glutamate antiporter xCT. While this phenomenon was prevented by pharmacological or genetic inhibition of xCT, overexpression of xCT sensitized resistant cancer cells to glucose deprivation. We found that cystine uptake and glutamate export through xCT under glucose deprivation contributes to rapid NADPH depletion, leading to the collapse of the redox system, which subsequently inactivates AMPK by inhibitory oxidation and phosphorylation. This AMPK dysregulation caused a failure of metabolic switch to fatty acid oxidation upon glucose deprivation, resulting in mitochondrial dysfunction and cell death. Taken together, these findings suggest a novel cross-talk between the metabolic and signal transduction and reveal a metabolic vulnerability in xCT-high expressing cancer cells to glucose deprivation and provide a rationale for targeting glucose metabolism in these cancer cells.