Inhibition of AMPK by Adenylate Kinase 4 Promotes EMT in Lung Cancer through ROS‐dependent Stabilization of HIF1‐α

Abstract

The field of cancer metabolism has largely focused on the metabolic reprogramming in supporting cancer proliferation. However, the metabolic alterations that are critical for cancer progression remain largely unknown. In this study, we analyzed lung cancer microarray datasets and found a set of metabolic genes that is positively correlated with mesenchymal signature in lung cancer patients. Upstream kinase analysis of EMT‐associated metabolic gene signature predicted AMP‐activated protein kinase (AMPK) inactivation by adenylate kinase may up‐regulate NADPH oxidase which leads to the production of intracellular reactive oxygen species (ROS). We next show TGF‐β‐induced EMT is accompanied by reduced AMPK activity and concurrent up‐regulation of adenylate kinase 4 (AK4) and NADPH oxidase. Knockdown of AK4 was sufficient to suppress TGF‐β‐induced EMT through AMPK activation. On the other hand, overexpression of AK4 inhibits AMPK activation, leading to NADPH oxidase‐mediated production of ROS, which in turn exaggerates HIF1‐α protein expression and induces EMT. IHC analysis showed an inverse correlation between AK4 and phosphorylated AMPK and a positive correlation between AK4 and nuclear HIF1‐α in lung cancer patients. Moreover, patients with high AK4 and low phosphorylated AMPK showed worse outcome compared to patients with low AK4 and high phosphorylated AMPK. Taken together, we identified overexpression of AK4 is critical for lung cancer cells to avoid AMPK‐mediated metabolic checkpoint and undergo EMT.