The two main sources from which normal cells require energy forproliferation and survival are glycolysis producing a net of 2 ATP from eachglucose and the second one being Krebs cycle, which uses pyruvate fromglycolysis and synthesising a net of 36 ATP per glucose molecule (Kim and Dang, 2006). Whenoxygen levels are low e.g. with muscles cells during exercise, metabolism shiftto anaerobic glycolysis producing 2 ATP per glucose. Cancer cells use anaerobicglycolysis despite the presence of normal amounts of environmental oxygen andare therefore termed “aerobic glycolysis”. It has been shown that cellsdedicate about 10% of the entire proteome and about half the total amount ofmetabolic proteins toward the production of enzymes for glycolysis making thecosts enormous as compared to costs of biosynthesis (Madhukar et al., 2015).
The firstobservation Otto Warburg and colleagues made in the 1920s was that tumor cellswere using up massive amounts of glucose compared to what was seen in thesurrounding tissue.