PFKFB2 and melanoma: Ribosomal S6 kinase 1 (RSK), the substrate of extracellular signal-regulated kinase 1/2 (ERK1/2) in the MAPK pathway, directly phosphorylates and activates fructose-6-phosphate 2-kinase/fructose-2,6-bisphosphatase 2 (PFKFB2), an enzyme catalyzing the synthesis of fructose-2,6-bisphosphatase, to promote melanoma glycolysis (48).