Glucose Metabolic Phenotypes in Cancer

1. Glucose Metabolic Phenotypes in Cancer W. Paul Lee, MD (10/2005) David Geffen School of Medicine at UCLA - Los Angeles Biomedical Research Institute at Harbor-UCLA.

2. Introduction

3. Objectives

4. Definition of Phenotype

5. Defining Phenotype by Composition: Metabolite Profiling Substrate or metabolite profiling (metabolomics) generates a data set of steady state concentrations of metabolites in plasma (or other bodily fluids) or in cell extracts.

10. Defining Phenotype by Fluxes: Metabolic profiling Metabolic profiling assesses steady state substrate flux of pathways of a metabolic network. It provides a set of dynamic parameters representing the metabolic phenotype. However, such measurements together with metabolites concentration still are inadequate to provide a functional description of the phenotype.

16. Tracer-based Metabolomics When a 13C labeled substrate is introduced into a biological system, 13C is incorporated into a wide range of metabolites collectively known as the metabolome either through exchange or by direct synthesis. The incorporation of a labeled carbon molecule into a metabolic product generates a �mass� signature (a difference in molecular weight from the naturally existing compound) which permits detection by mass spectrometry or by NMR.

17. Tracer-based metabolomics The distribution and destinations of a labeled carbon are determined by the intracellular metabolic pathways that it traverses. The metabolic phenotype determines tracer distribution within individual compounds and distribution among compounds. Such a distribution represents the metabolic functions of the cell and defines its metabolic phenotype.

21. Constraint-based modeling and Tracer-based Metabolomics Constraint-based modeling and Tracer-based Metabolomics provide a network - system biology - context to metabolite and flux measurements.

22. Phenotypic Phase Plane Analysis

27. Nutrient Environment Gene Interaction on Phenotype (1) Genetic factors confer to cells a specific set of metabolic functions which corresponds to a metabolic phenotype under a given nutrient environment. How can the information from tracer-based metabolomics be used to understand gene nutrient interaction in the determination of phenotype? Genetic factors confer a broad phenotypic space. For a given nutrient environment, the space is limited to the expressed phenotype .How can the information from tracer-based metabolomics be used to understand gene nutrient interaction in the determination of phenotype? Genetic factors confer a broad phenotypic space. For a given nutrient environment, the space is limited to the expressed phenotype .

28. Here we have three cell lines carrying different genomic endowment. The phenotypes of these cells in the same culture medium are characterized by the pentose synthesis and transketolase activity. Mia cell is a cancer cell, normal fibroblast and fibroblast from patient with high affinity thiamine transport defect. These cell have different rate of proliferation under same culture medium condition and have different rate of pentose synthesis and transketolase activities.Here we have three cell lines carrying different genomic endowment. The phenotypes of these cells in the same culture medium are characterized by the pentose synthesis and transketolase activity. Mia cell is a cancer cell, normal fibroblast and fibroblast from patient with high affinity thiamine transport defect. These cell have different rate of proliferation under same culture medium condition and have different rate of pentose synthesis and transketolase activities.

29. Nutrient Environment Gene Interaction on Phenotype (2) Changes in nutrient environment select cells with the actual observed metabolic phenotypes, which function best under such environments. Since the genotype confers a wide range of possible phenotypes, changes in nutrient environment selects the phenotype that functions best under the altered environment.Since the genotype confers a wide range of possible phenotypes, changes in nutrient environment selects the phenotype that functions best under the altered environment.

30. This slide shows that the poorly proliferative phenotype of TRMA cells being changes to a more proliferative phenotype when large amount of thiamine is supplemented in the medium. The converse example is shown by MIA cells under the treatment with oxythiaimine, a transketolase inhibitor. These cells have the same genotypes but different phenotypes under different nutrient environment.This slide shows that the poorly proliferative phenotype of TRMA cells being changes to a more proliferative phenotype when large amount of thiamine is supplemented in the medium. The converse example is shown by MIA cells under the treatment with oxythiaimine, a transketolase inhibitor. These cells have the same genotypes but different phenotypes under different nutrient environment.

31. Nutrient-Gene Interaction in Cancer Promotion The evolution of cancer cells can be understood in terms of metabolic selection. Genetic mechanism is the source of phenotypic variation, while the final observed species is the result of metabolic selection. How can we extend this idea of phenotype selection to understand the effect of nutrient on cancer promotion. The evolution of cancer cells can be understood in terms of metabolic selection. Genetic mechanism is the source of phenotypic variation, while the final observed species is the result of metabolic selection. How can we extend this idea of phenotype selection to understand the effect of nutrient on cancer promotion. The evolution of cancer cells can be understood in terms of metabolic selection. Genetic mechanism is the source of phenotypic variation, while the final observed species is the result of metabolic selection.

32. We choose here an example from our work with colon cancer cells HT29. One can imagine the precursor of HT29 cells as one utilizing butyrate. When butyrate is limited because of reduced intake of vegetable, the grow of the precursor is limited. Over many cell division, the phenotype that utilizes glucose is selected and compete effectively with neighboring cells. When butyrate is supplied in the medium, the phenotype of these cells reverted to the less proliferative form because of preexisting metabolic network favoring butyrate utilization. Such changes were not observed for MIA cells.We choose here an example from our work with colon cancer cells HT29. One can imagine the precursor of HT29 cells as one utilizing butyrate. When butyrate is limited because of reduced intake of vegetable, the grow of the precursor is limited. Over many cell division, the phenotype that utilizes glucose is selected and compete effectively with neighboring cells. When butyrate is supplied in the medium, the phenotype of these cells reverted to the less proliferative form because of preexisting metabolic network favoring butyrate utilization. Such changes were not observed for MIA cells.

34. Conclusion (1) Genetic inheritance (genomic constraints) confers a set of possible phenotypes. Selection by metabolic (structural and pathway relationship) and environmental (physical environment and substrate availability) constraints determines the final observed phenotype.

35. Conclusion (2) The metabolic phenotype of a cell can be characterized by a set of flux solution space bounded by genomic/ proteomic/metabolomic constraints. Tracer-based metabolomics is a powerful tool for the characterization of metabolic phenotype.

38. Conclusion (3) It is clear from the metabolic selection hypothesis, nutrient changes are important environmental factors in determining cancer risks. Thus, cancer prevention strategies can be formulated based on our understanding of nutrient gene interaction using constraint-based modeling and metabolic network flux analysis.

39. Other Applications of Tracer-based Metabolomics In the past ten years, we have worked on a number of projects using tracer-based metabolomics.In the past ten years, we have worked on a number of projects using tracer-based metabolomics.