Sub-Sets of Cancer Stem Cells Differ Intrinsically in Their Patterns of Oxygen Metabolism

PMCID: PMC3640080This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Coupling of Glucose Deprivation with Impaired Histone H2B Monoubiquitination in Tumors

Metabolic reprogramming is associated with tumorigenesis. However, glucose metabolism in tumors is poorly understood. Here, we report that glucose levels are significantly lower in bulk tumor specimens than those in normal tissues of the same tissue origins. We show that mono-ubiquitinated histone H2B (uH2B) is a semi-quantitative histone marker for glucose. We further show that loss of uH2B occurs specifically in cancer cells from a wide array of tumor specimens of breast, colon, lung and additional 23 anatomic sites. In contrast, uH2B levels remain high in stromal tissues or non-cancerous cells in the tumor specimens. Taken together, our data suggest that glucose deficiency and loss of uH2B are novel properties of cancer cells in vivo, which may represent important regulatory mechanisms of tumorigenesis

Dynamic interplay between tumour, stroma and immune system can drive or prevent tumour progression

In the tumour microenvironment, cancer cells directly interact with both the immune system and the stroma. It is firmly established that the immune system, historically believed to be a major part of the body's defence against tumour progression, can be reprogrammed by tumour cells to be ineffective, inactivated, or even acquire tumour promoting phenotypes. Likewise, stromal cells and extracellular matrix can also have pro-and anti-tumour properties. However, there is strong evidence that the stroma and immune system also directly interact, therefore creating a tripartite interaction that exists between cancer cells, immune cells and tumour stroma. This interaction contributes to the maintenance of a chronically inflamed tumour microenvironment with pro-tumorigenic immune phenotypes and facilitated metastatic dissemination. A comprehensive understanding of cancer in the context of dynamical interactions of the immune system and the tumour stroma is therefore required to truly understand the progression toward and past malignancy.Comment: 36 pages, 4 figures, 1 tabl

Precursors of Cytochrome Oxidase in Cytochrome-Oxidase-Deficient Cells of Neurospora crassa

Three different cell types of Neurospora crassa deficient in cytochrome oxidase were studied: the nuclear mutant cni-1, the cytoplasmic mutant mi-1 and copper-depleted wild-type cells. * 1. The enzyme-deficient cells have retained a functioning mitochondrial protein synthesis. It accounted for 12–16% of the total protein synthesis of the cell. However, the analysis of mitochondrial translation products by gel electrophoresis revealed that different amounts of individual membrane proteins were synthesized. Especially mutant cni-1 produced large amounts of a small molecular weight translation product, which is barely detectable in wild-type. * 2. Mitochondrial preparations of cytochrome-oxidase-deficient cells were examined for precursors of cytochrome oxidase. The presence of polypeptide components of cytochrome oxidase in the mitochondria was established with specific antibodies. On the other hand, no significant amounts of heme a could be extracted. * 3. Radioactively labelled components of cytochrome oxidase were isolated by immunoprecipitation and analysed by gel electrophoresis. All three cell types contained the enzyme components 4–7, which are translated on cytoplasmic ribosomes. The mitochondrially synthesized components 1–3 were present in mi-1 mutant and in copper-depleted wild-type cells. In contrast, components 2 and 3 were not detectable in the nuclear mutant cni-1. Both relative and absolute amounts of these polypeptides in the enzyme-deficient cells were quite different from those in wild-type cells. * 4. The components of cytochrome oxidase found in the enzyme-deficient cells were tightly associated with the mitochondrial membranes. * 5. Processes, which affect and may control the production of enzyme precursors or their assembly to a functional cytochrome oxidase are discussed

Rottlerin stimulates apoptosis in pancreatic cancer cells through interactions with proteins of the Bcl-2 family

Rottlerin is a polyphenolic compound derived from Mallotus philipinensis. In the present study, we show that rottlerin decreased tumor size and stimulated apoptosis in an orthotopic model of pancreatic cancer with no effect on normal tissues in vivo. Rottlerin also induced apoptosis in pancreatic cancer (PaCa) cell lines by interacting with mitochondria and stimulating cytochrome c release. Immunoprecipitation results indicated that rottlerin disrupts complexes of prosurvival Bcl-xL with Bim and Puma. Furthermore, siRNA knockdown showed that Bim and Puma are necessary for rottlerin to stimulate apoptosis. We also showed that rottlerin and Bcl-2 and Bcl-xL inhibitor BH3I-2' stimulate apoptosis through a common mechanism. They both directly interact with mitochondria, causing increased cytochrome c release and mitochondrial depolarization, and both decrease sequestration of BH3-only proteins by Bcl-xL. However, the effects of rottlerin and BH3I-2' on the complex formation between Bcl-xL and BH3-only proteins are different. BH3I-2' disrupts complexes of Bcl-xL with Bad but not with Bim or Puma, whereas rottlerin had no effect on the Bcl-xL interaction with Bad. Also BH3I-2', but not rottlerin, required Bad to stimulate apoptosis. In conclusion, our results demonstrate that rottlerin has a potent proapoptotic and antitumor activity in pancreatic cancer, which is mediated by disrupting the interaction between prosurvival Bcl-2 proteins and proapoptotic BH3-only proteins. Thus rottlerin represents a promising novel agent for pancreatic cancer treatment

Quiescience as a mechanism for cyclical hypoxia and acidosis

Tumour tissue characteristically experiences fluctuations in substrate supply. This unstable microenvironment drives constitutive metabolic changes within cellular populations and, ultimately, leads to a more aggressive phenotype. Previously, variations in substrate levels were assumed to occur through oscillations in the hæmodynamics of nearby and distant blood vessels. In this paper we examine an alternative hypothesis, that cycles of metabolite concentrations are also driven by cycles of cellular quiescence and proliferation. Using a mathematical modelling approach, we show that the interdependence between cell cycle and the microenvironment will induce typical cycles with the period of order hours in tumour acidity and oxygenation. As a corollary, this means that the standard assumption of metabolites entering diffusive equilibrium around the tumour is not valid; instead temporal dynamics must be considered

Expression of GLUT1 and GLUT3 Glucose Transporters in Endometrial and Breast Cancers

Cancer cells have accelerated metabolism and high glucose requirements. The up-regulation of specific glucose transporters may represent a key mechanism by which malignant cells may achieve increased glucose uptake to support the high rate of glycolysis. In present study we analyzed the mRNA and protein expression of GLUT1 and GLUT3 glucose transporters by quantitative real-time polymerase chain reaction (Q-PCR) and Western blotting technique in 76 cases of endometrial carcinoma and 70 cases of breast carcinoma. SLC2A1 and SLCA2A3 mRNAs expression was found, respectively in 100% and 97.4% samples of endometrial cancers and only in 50% and 40% samples of breast cancers. In endometrial cancers GLUT1 and GLUT3 protein expression was identified in 67.1% and 30.3% of cases. Analogously, in breast cancers in 48.7% and 21% of samples, respectively. The results showed that both endometrial and breast poorly differentiated tumors (grade 2 and 3) had significantly higher GLUT1 and GLUT3 expression than well-differentiated tumors (grade 1). Statistically significant association was found between SLCA2A3 mRNA expression and estrogen and progesterone receptors status in breast cancers. GLUT1 has been reported to be involved in the uptake of glucose by endometrial and breast carcinoma cells earlier and the present study determined that GLUT3 expression is also involved. GLUT1 and GLUT3 seem to be important markers in endometrial and breast tumors differentiation

Molecular crowding defines a common origin for the Warburg effect in proliferating cells and the lactate threshold in muscle physiology

Aerobic glycolysis is a seemingly wasteful mode of ATP production that is seen both in rapidly proliferating mammalian cells and highly active contracting muscles, but whether there is a common origin for its presence in these widely different systems is unknown. To study this issue, here we develop a model of human central metabolism that incorporates a solvent capacity constraint of metabolic enzymes and mitochondria, accounting for their occupied volume densities, while assuming glucose and/or fatty acid utilization. The model demonstrates that activation of aerobic glycolysis is favored above a threshold metabolic rate in both rapidly proliferating cells and heavily contracting muscles, because it provides higher ATP yield per volume density than mitochondrial oxidative phosphorylation. In the case of muscle physiology, the model also predicts that before the lactate switch, fatty acid oxidation increases, reaches a maximum, and then decreases to zero with concomitant increase in glucose utilization, in agreement with the empirical evidence. These results are further corroborated by a larger scale model, including biosynthesis of major cell biomass components. The larger scale model also predicts that in proliferating cells the lactate switch is accompanied by activation of glutaminolysis, another distinctive feature of the Warburg effect. In conclusion, intracellular molecular crowding is a fundamental constraint for cell metabolism in both rapidly proliferating- and non-proliferating cells with high metabolic demand. Addition of this constraint to metabolic flux balance models can explain several observations of mammalian cell metabolism under steady state conditions