ATP5IF1 and cancer: The decreased activity of ATP synthase in cancer cells arises from a combination of up-regulated expression of IF1 and down-regulation of β-F1-ATPase, resulting in enhanced aerobic glycolysis (Scheme 1).5 ATP synthase activity and protein expression in colon cancer cells were reported to be down regulated under 5-fluorouracil (5-FU) resistance.4 The suppression of ATP synthase subunits is dependent on cancer cell lines.