The respiratory quotients of normal and tumour tissue

Cancer Metabolism Historical Perspectives: A Chronicle of Controversies and Consensus

A century ago, Otto Warburg's work sparked the field of cancer metabolism, which has since taken a tortuous path. As evidence accumulated over the decades, consensus views of causes of cancer emerged, whereby genetic and epigenetic oncogenic drivers promoted immune evasion and induced new blood vessels and neoplastic metabolism to support tumor growth. Neoplastic cells abandon social cues of intercellular cooperation, escape tissue confinement, metastasize, and ultimately kill the host. Herein, key milestones in the study of cancer metabolism are chronicled with an emphasis on carbohydrate metabolism. The field began with a cancer cell-autonomous view that has been refined by a richer understanding of solid cancers as growing, immune-suppressive, complex organs comprising different cell types that are nourished by a variety of nutrients and variable amounts of oxygen through abnormal neovasculatures. Based on foundational historical studies, our current understanding of cancer metabolism offers a hopeful outlook for targeting metabolism to enhance cancer therapy.

Release from the Crabtree effect by hypoxic cell radiosensitizers

The Crabtree effect can be observed when the O2 consumption of tumour cells or of mammalian cells grown in culture is measured in physiological medium containing glucose. The effect of 2 hypoxic cell radiosensitizers, misonidazole and NDPP, on the O2 consumption of Ehrlich ascites tumour cells was compared in media with and without glucose. A stimulatory effect on O2 consumption was found for 5--20mM misonidazole as well as for 0.5mM NDPP, both in media containing 10(-2)M glucose. Thus glucose induced a Crabtree effect in Ehrlich tumour cells, expressed as 38--45% inhibition of O2 consumption relative to that in the same medium without glucose. The stimulatory effect of misonidazole and NDPP on O2 utilization in medium with glucose undoubtedly appeared as a release from the Crabtree effect.

The stimulation of glycolysis by previous aerobiosis in rat-liver slices

1. An investigation has been made on the stimulation of the anaerobic glycolysis by rat-liver slices caused by previous incubation in oxygen. 2. The stimulation is sustained partly by endogenous carbohydrates and partly by added glucose. The effect of glucose reaches a maximum at a concentration of 20mm; it is more pronounced when glucose is present in the actual glycolytic phase and not during the aerobic preincubation. The conversion of fructose and pyruvate into lactic acid is not affected by the preincubation in oxygen. 3. The stimulation occurs also when preincubation is carried out in a medium that blocks the action of phosphorylase. 4. Preincubation for 2-3min. at 37 degrees is enough to ensure maximum stimulation. The main effect of the aerobic incubation is on the initial velocity of the anaerobic glycolysis. 5. The stimulation depends on the nutritional state of the animal: it is decreased practically to nil in rats starved overnight. In starved animals glycogen content and basal and stimulated glycolysis decline progressively with the same trend. If starved animals are injected with glucose, liver glycogen concentration increases but basal glycolysis remains at a low level; however, the rate of stimulated glycolysis becomes progressively higher and correlates with the amount of liver glycogen. 6. It is suggested that the aerobic preincubation modifies the factors that regulate glycolysis in liver slices at steps above the level of triose phosphates.