Intriguingly, cancer cells specifically express pyruvate kinase M (PKM)-2 that oxidizes and generates reduced nicotinamide adenine dinucleotide phosphate (NADPH) to maintain redox buffering; besides, this PKM-2 gene trans-activates HIF-1α target genes, leading to a significant shift in metabolic activity and cancer cell signaling [26, 27]. Here, HIF1A is linked to cancer.