Sirtuin 6 and metabolic genes interplay in Warburg effect in cancers

Abstract

Under oxygen availability, normal cells undergo mitochondrial oxidative phosphorylation to metabolize glucose and yield up to 36 ATPs per glucose molecule for cellular functions, and undergo non-oxidative metabolism (glycolysis) under hypoxic and proliferating conditions to yield 2 ATP per glucose. These cells metabolize glucose to pyruvate via glycolysis followed by conversion of pyruvate to lactate via lactate dehydrogenase. However, cancer cells have the ability to undergo glycolysis and ferment glucose to lactate regardless of oxygen availability; a phenomenon first addressed by Otto Warburg and called, "Warburg effect". Numerous glycolytic genes/proteins have been identified in tumors; that include glucose transporter 1 (GLUT1), hexokinase 2 (HK2), pyruvate kinase-M2 splice isoform (PKM2), and lactate dehydrogenase (LDHA). Histone deacetylase sirtuin 6 (SIRT6), an epigenetic regulator, is highly expressed in various cancers. SIRT6 plays an important role in Warburg effect by regulating many glycolytic genes. Loss of SIRT6 enhances tumor growth via enhancing glycolysis. This review is mainly concerned with exploring the most recent advances in understanding the roles of the metabolic genes (GLUT1, HK2, PKM2, and LDH-A) and the epigenetic regulator SIRT6 in cancer metabolism and how SIRT6 can modulate these metabolic genes expression and its possible use as a therapeutic target for cancer treatment.