An increase in pHi driven by MCT4 promotes proliferation. A gauge for pHi is shown in which a normal cell is at the green zone. MCT4 increases pHi to the alkaline orange and red zones. Shifts in pHi by MCT4 overexpression in normal hematopoietic progenitors or an epigenetic-mediated upregulation of MCT4 in AML increases the activity of metabolic enzymes to reprogram carbon metabolism. Professional illustration by Somersault 18:24.