EPO and neoplasm: Whereas HIF-1α is mostly responsible for activation of glycolytic pathway genes (e.g. HK1 (hexokinase 1) and HK2 (hexokinase 2)), HIF-2α is involved in regulation of genes responsible for cell cycle progression (e.g. cyclin D1), tumor growth, erythropoiesis (EPO (erythropoietin)), and maintaining stem cell pluripotency among other functions (14, 15).