INTERMEDIARY METABOLISM ININTERMEDIARY METABOLISM IN CANCER

MOLECULAR ONCOLOGY20122012

Michael Lea

Intermediary Metabolism - Lecture Outline

• Glycolysis and respiration in cancer cells• Convergence and deletions • Correlation of biochemical parameters with tumor

growth• Polyamines• Polyamines

GLYCOLYSIS AND RESPIRATION IN CANCER CELLS

The first metabolic pathways to be studied in cancer cells were those of glycolysis and cell respiration. Otto Warburg studied these parameters using tissue slices incubated in a bicarbonate bufferthese parameters using tissue slices incubated in a bicarbonate buffer in flasks attached to a manometer. By incubating in media gassed with either 95% oxygen/5% CO2 or 95% nitrogen/5% CO2 it was possible to measure glycolysis under aerobic or anaerobic conditions.possible to measure glycolysis under aerobic or anaerobic conditions. The production of lactic or pyruvic acids causes the release of CO2from the bicarbonate buffer. Quotients were measured for aerobic glycolysis (QL O2), anaerobic glycolysis (QL N2) and respiratory g y y ( 2) g y y ( 2) p yactivity (QO2).

The data indicated that, in general, glycolysis was greater in malignant than in non-malignant tissues. This was more marked g gunder aerobic than anaerobic conditions. This difference suggested that the Pasteur effect was greater in normal tissues. It should be noted that there is an overlap of values in Warburg’s data.

For debate see Science 124: 267 272 1956For debate see Science, 124: 267-272, 1956

Table 15.2 Condensed Tumor Metabolism Data of Warburg, Burk, and OthersSee H.C. Pitot, Fundamentals of Oncology, 4th edition, page 645

Tissue Respiration Anerobic AerobicGlycolysis Glycolysisy y y y

Normal animal tissues 9.3 7.2 2.1(3-21) (2-19) (0-10)( ) ( ) ( )

Animal neoplasms 11.8 25.6 14.0p(5.3-19.8 (14.0-34.8) (4.7-24.6)

Human neoplasms 5.3 20.5 13.3(2-6) (13-29) (5-19)( ) ( ) ( )

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CONVERGENCE AND DELETIONS

• Warburg concluded that cancer originated from an irreversible injury of respiration

• Greenstein noted that many tumors showed a convergence in their metabolic patterns

• In 1947 the Millers suggested that carcinogenesis• In 1947 the Millers suggested that carcinogenesis results from “a permanent alteration or loss of proteins essential for the control of growth.”

• Studies by Weber on the Morris series of chemically induced hepatomas in rats led to the Molecular Correlation Concept in which some biochemicalCorrelation Concept in which some biochemical parameters are viewed as correlating with tumor growth. (Reference; G. Weber, New England J. Med. 296: 486 and 541 1977)541, 1977)

UPREGULATION OF GLYCOLYSIS LEADS TO MICROENVIRONMENTAL ACIDOSIS

Clinical use of 18fluorodeoxyglucose positron-emission t h (FdG PET) h d t t d th t i d ltomography (FdG PET) has demonstrated that increased glucose uptake is observed in most human cancer.

Increased FdG uptake occurs because of upregulation of glucose transporters, notably GLUT1 and GLUT3, and results in increased glycolysis.

Increased glycolysis results in microenvironmental acidosis and requires further adaptation through somatic evolution to phenotypes resistant to acid-induced toxicity.

Reference: R.A. Gatenby and R.J. Gillies. Why do cancers have high aerobic glycolysis? Nature Reviews Cancer 4: 891-899, 2004.

INHIBITING GLYCOLYSISA l k f t ifi i hibit f l l i h• A lack of tumor-specific inhibitors of glycolysis has historically prevented glycolysis being used as a chemotherapeutic target.

• Glycolysis can be activated by an increase in the concentration of fructose 2,6-bisphosphate which activates the rate-limiting enzyme phosphofructokinase 1.

• Fructose 2,6-bisphosphate is produced by the bifunctional enzyme phosphofructokinase 2/ fructosebifunctional enzyme phosphofructokinase 2/ fructose 2,6-bisphosphatase (PFKFB).

• The inducible PFKFB3 isozyme is constitutively expressed by many tumor cellsexpressed by many tumor cells.

• A small molecule inhibitor of PFKFB3 has been reported to inhibit the growth of tumors in mice.

• Reference: Clem et al., Mol. Cancer Ther. 7: 110120, 2008)

Levine and Puzio-KuterScience 330:1340-1344.2010

TIGAR: TP53 induced glycolysis and apoptosis regulator

IDH mutations and cancer

Mutations in isocitrate dehydrogenase 1 and 2 result in the formation of 2-hydroxyglutarate (2HG) instead of alpha ketoglutarate 2HG is a competitive inhibitor ofalpha-ketoglutarate. 2HG is a competitive inhibitor of alpha-ketoglutarate-dependent dioxygenases. Dioxygenases have an important role in demethylation reactions for histones and DNA causing hypermethylation in glioma and AML.

•• Reference: Yen KE and Schenkein DP: Cancer-associated isocitrate

dehydrogenase mutations. The Oncologist 17: 5-5, 2012

POLYAMINES

Polyamines are organic cations formed by the enzymatic decarboxylation of ornithine to yield putrescine and by further additions from decarboxylated S adenosyl methionine to formadditions from decarboxylated S-adenosyl methionine to form spermidine and spermine. Ornithine decarboxylase and polyamine content are increased in many carcinomas including skin and colon cancermany carcinomas including skin and colon cancer.

DFMO (difluoromethylornithine) is an inhibitor of ornithine d b l d h tit tidecarboxylase and has some antitumor action.

Polyamines work at least in part by regulating specific gene expression

Reference: E.W. Gerner and F.L. Meyskens. Polyamines and cancer: old l l d t di N t i C 4 781 792 2004molecules, new understanding. Nature reviews Cancer 4: 781-792, 2004.

INTERMEDIARY METABOLISMINTERMEDIARY METABOLISM -SUGGESTED READING

• R.W. Ruddon and R.W. Kufe, In Holland-Frei Cancer Medicine - 8th Ed, Part II, Section 1, 9 Biochemistry of Cancer (2010)9. Biochemistry of Cancer (2010)

• A J Levine and A M Puzio Kuter The control• A.J. Levine and A.M. Puzio-Kuter. The control of the metabolic switch in cancers by oncogenes and tumor suppressor genes. Science 330: 1340-1344, 2010.