Metabolic features of CSCs. In non-stem/highly proliferative cancer cells, glycolysis is a predominant metabolic phenotype contributing to tumor growth. CSCs rely on OXPHOS metabolism or combined metabolism with high glycolysis, depending on the oncogenic background and surrounding microenvironment conditions such as hypoxia or nutrient supplementation. CSCs also show metabolic plasticity between two metabolic phenotypes. However, in either case, mitochondrial function is critical for CSC functions such as stemness, migration, and drug resistance.