The hallmarks of cancer

Differential gene expression in mesothelioma

To investigate the molecular events controlling malignant transformation of human pleural cells, we compared constitutive gene expression of mesothelioma cells to that of pleural cells. Using cDNA microarray and high-density filter array, we assessed expression levels of > 6500 genes. Most of the highly expressed transcripts were common to both cell lines and included genes associated with stress response and DNA repair, outcomes consistent with the radio- and chemo-resistance of mesothelioma. Interestingly, of the fewer than 300 genes that differed between cell lines, most functioned in (i) macromolecule stability, (ii) cell adhesion and recognition, (iii) cell migration (invasiveness), and (iv) extended cell division. Expression levels of several of these genes were confirmed by RT-PCR and could be useful as diagnostic markers of human mesothelioma.

Mutations and copy number increase of HRAS in Spitz nevi with distinctive histopathological features

Spitz nevus is a benign melanocytic neoplasm that can be difficult or impossible to histologically distinguish from melanoma. We have recently described copy number increases of chromosome 11p in a subset of Spitz nevi. To study the molecular and histological features of this group, we studied 102 Spitz nevi for 11p copy number increases using fluorescence in situ hybridization (FISH) on tissue arrays. Copy number increases of at least threefold were found in 12 cases (11.8%) and involved the HRAS gene on chromosome 11p. Sequence analysis of HRAS showed frequent oncogenic mutations in cases with copy number increase (8/12 or 67%), contrasting with rare HRAS mutations in cases with normal HRAS copy numbers (1/21 or 5%, P: < 0.0001). Tumors with 11p copy number increases were larger, predominantly intradermal, had marked desmoplasia, characteristic cytological features, and had an infiltrating growth pattern. Proliferation rates in the majority of these cases were low to absent. HRAS activation by either mutation or copy number increase alone could explain several of the histological features that overlap with those of melanoma. We speculate that HRAS activation in the absence of co-operating additional genetic alterations drives the partially transformed melanocytes of these Spitz nevi into senescence or a stable growth arrest. Although there is no data suggesting that Spitz nevi with HRAS activation are at risk for progression to melanoma, future studies are warranted to assess their biological behavior more accurately.

An alternate splicing variant of the human telomerase catalytic subunit inhibits telomerase activity

Telomerase, a cellular reverse transcriptase, adds telomeric repeats to chromosome ends. In normal human somatic cells, telomerase is repressed and telomeres progressively shorten, leading to proliferative senescence. Introduction of the telomerase (hTERT) cDNA is sufficient to produce telomerase activity and immortalize normal human cells, suggesting that the repression of telomerase activity is transcriptional. The telomerase transcript has been shown to have at least six alternate splicing sites (four insertion sites and two deletion sites), and variants containing both or either of the deletion sites are present during development and in a panel of cancer cell lines we surveyed. One deletion (beta site) and all four insertions cause premature translation terminations, whereas the other deletion (alpha site) is 36 bp and lies within reverse transcriptase (RT) motif A, suggesting that this deletion variant may be a candidate as a dominant-negative inhibitor of telomerase. We have cloned three alternately spliced hTERT variants that contain the alpha, beta or both alpha and beta deletion sites. These alternate splicing variants along with empty vector and wild-type hTERT were introduced into normal human fibroblasts and several telomerase-positive immortal and tumor cell lines. Expression of the alpha site deletion variant (hTERT alpha-) construct was confirmed by Western blotting. We found that none of the three alternate splicing variants reconstitutes telomerase activity in fibroblasts. However, hTERT alpha- inhibits telomerase activities in telomerase-positive cells, causes telomere shortening and eventually cell death. This alternately spliced dominant-negative variant may be important in understanding telomerase regulation during development, differentiation and in cancer progression.

Macromolecular intelligence in microorganisms

Biochemistry and molecular biology have been focusing on the structural, catalytic, and regulatory properties of individual macromolecules from the perspective of clarifying the mechanisms of metabolism and gene expression. Complete genomes of 'primitive' living organisms seem to be substantially larger than necessary for metabolism and gene expression alone. This is in line with the findings of silent phenotypes for supposedly important genes, apparent redundancy of functions, and variegated networks of signal transduction and transcription factors. Here we propose that evolutionary optimization has been much more intensive than to lead to the bare minima necessary for autonomous life. Much more complex organisms prevail. Much of this complexity arises in the nonlinear interactions between cellular macromolecules and in subtle differences between paralogs (isoenzymes). The complexity can only be understood when analyzed quantitatively, for which quantitative experimentation is needed in living systems that are as simple and manipulatable as possible, yet complex in the above sense. We illustrate this for the glutamine synthetase cascade in Escherichia coli. By reviewing recent molecular findings, we show that this cascade is much more complex than necessary for simple regulation of ammonia assimilation. Simulations suggest that the function of this complexity may lie in quasi-intelligent behavior, including conditioning and learning.

The thin red line: angiogenesis in normal and malignant hematopoiesis

This review describes the current knowledge about cell subsets involved in vasculogenesis (i.e., differentiation of endothelial cells from mesodermal precursors) and angiogenesis (i.e., blood vessel generation from pre-existing vessels), together with recent findings about angiogenesis and antiangiogenic therapies in hematopoietic malignancies such as leukemia, lymphoma, myeloma, and myelodysplastic syndromes.

Gene expression profiling: monitoring transcription and translation products using DNA microarrays and proteomics

Novel and powerful technologies such as DNA microarrays and proteomics have made possible the analysis of the expression levels of multiple genes simultaneously both in health and disease. In combination, these technologies promise to revolutionize biology, in particular in the area of molecular medicine as they are expected to reveal gene regulation events involved in disease progression as well as to pinpoint potential targets for drug discovery and diagnostics. Here, we review the current status of these technologies and highlight some studies in which they have been applied in concert to the analysis of biopsy specimens.

Smad4/DPC4-mediated tumor suppression through suppression of angiogenesis

Smad4/DPC4 (deleted in pancreatic carcinoma, locus 4) is a tumor suppressor gene lost at high frequency in cancers of the pancreas and other gastrointestinal organs. Smad4 encodes a key intracellular messenger in the transforming growth factor beta (TGF-beta) signaling cascade. TGF-beta is a potent inhibitor of the growth of epithelial cells; thus, it has been assumed that loss of Smad4 during tumor progression relieves this inhibition. Herein, we show that restoration of Smad4 to human pancreatic carcinoma cells suppressed tumor formation in vivo, yet it did not restore sensitivity to TGF-beta. Rather, Smad4 restoration influenced angiogenesis, decreasing expression of vascular endothelial growth factor and increasing expression of thrombospondin-1. In contrast to the parental cell line and to control transfectants that produced rapidly growing tumors in vivo, Smad4 revertants induced small nonprogressive tumors with reduced vascular density. These data define the control of an angiogenic switch as an alternative, previously unknown mechanism of tumor suppression for Smad4 and identify the angiogenic mediators vascular endothelial growth factor and thrombospondin-1 as key target genes.

The most unkindest cut of all: on the multiple roles of mammalian caspases

The caspases, first discovered almost a decade ago, are intracellular cysteine proteases which have been shown to play an essential role in the initiation and execution phases of apoptotic cell death. Numerous strategies for the activation and inhibition of these 'killer' proteases have evolved, including the regulation of caspase expression and function at the transcriptional and post-translational level, as well as the expression of viral and cellular inhibitors of caspases. Emerging evidence in recent years has also implicated the caspases in various, nonapoptotic aspects of cellular physiology, such as cytokine processing during inflammation, differentiation of progenitor cells during erythropoiesis and lens fiber development, and proliferation of T lymphocytes, thus attesting to the pleiotropic functions of these proteases. The present review aims to discuss the multiple roles of the mammalian caspases with particular emphasis on their activation and regulation in cells of leukemic origin and the attendant possibilities of therapeutic intervention.

The influence of the microenvironment on the malignant phenotype

Normal tissue homeostasis is maintained by dynamic interactions between epithelial cells and their microenvironment. As tissue becomes cancerous, there are reciprocal interactions between neoplastic cells, adjacent normal cells such as stroma and endothelium, and their microenvironments. The current dominant paradigm wherein multiple genetic lesions provide both the impetus for, and the Achilles heel of, cancer might be inadequate to understand cancer as a disease process. In the following brief review, we will use selected examples to illustrate the influence of the microenvironment in the evolution of the malignant phenotype. We will also discuss recent studies that suggest novel therapeutic interventions might be derived from focusing on microenvironment and tumor cells interactions.

Reprimo, a new candidate mediator of the p53-mediated cell cycle arrest at the G2 phase

A novel gene, Reprimo, in which induction in cells exposed to X-irradiation is dependent on p53 expression, has been isolated. Ectopic p53 expression results in the induction of its mRNA. Reprimo is a highly glycosylated protein and, when ectopically expressed, it is localized in the cytoplasm and induces G(2) arrest of the cell cycle. In the arrested cells, both Cdc2 activity and nuclear translocation of cyclin B1 are inhibited, suggesting the involvement of Reprimo in the Cdc2.cyclin B1 regulation pathway. Thus, Reprimo may be a new member involved in the regulation of p53-dependent G(2) arrest of the cell cycle.

Epidermal growth factor-induced nuclear factor kappa B activation: A major pathway of cell-cycle progression in estrogen-receptor negative breast cancer cells

The epidermal growth factor (EGF) family of receptors (EGFR) is overproduced in estrogen receptor (ER) negative (-) breast cancer cells. An inverse correlation of the level of EGFR and ER is observed between ER- and ER positive (+) breast cancer cells. A comparative study with EGFR-overproducing ER- and low-level producing ER+ breast cancer cells suggests that EGF is a major growth-stimulating factor for ER- cells. An outline of the pathway for the EGF-induced enhanced proliferation of ER- human breast cancer cells is proposed. The transmission of mitogenic signal induced by EGF-EGFR interaction is mediated via activation of nuclear factor kappaB (NF-kappaB). The basal level of active NF-kappaB in ER- cells is elevated by EGF and inhibited by anti-EGFR antibody (EGFR-Ab), thus qualifying EGF as a NF-kappaB activation factor. NF-kappaB transactivates the cell-cycle regulatory protein, cyclin D1, which causes increased phosphorylation of retinoblastoma protein, more strongly in ER- cells. An inhibitor of phosphatidylinositol 3 kinase, Ly294-002, blocked this event, suggesting a role of the former in the activation of NF-kappaB by EGF. Go6976, a well-characterized NF-kappaB inhibitor, blocked EGF-induced NF-kappaB activation and up-regulation of cell-cycle regulatory proteins. This low molecular weight compound also caused apoptotic death, predominantly more in ER- cells. Thus Go6976 and similar NF-kappaB inhibitors are potentially novel low molecular weight therapeutic agents for treatment of ER- breast cancer patients.

Distinct initiation and maintenance mechanisms cooperate to induce G1 cell cycle arrest in response to DNA damage

DNA damage causes stabilization of p53, leading to G1 arrest through induction of p21cip1. As this process requires transcription, several hours are needed to exert this response. We show that DNA damage causes an immediate and p53-independent G1 arrest, caused by rapid proteolysis of cyclin D1. Degradation is mediated through a previously unrecognized destruction box in cyclin D1 and leads to a release of p21cip1 from CDK4 to inhibit CDK2. Interference with cyclin D1 degradation prevents initiation of G1 arrest and renders cells more susceptible to DNA damage, indicating that cyclin D1 degradation is an essential component of the cellular response to genotoxic stress. Thus, induction of G1 arrest in response to DNA damage is minimally a two step process: a fast p53-independent initiation of G1 arrest mediated by cyclin D1 proteolysis and a slower maintenance of arrest resulting from increased p53 stability.

Metastases: the glycan connection

An association between protein glycosylation and tumorigenesis has been recognized for over 10 years. Associations linking the importance of glycosylation events to tumor biology, especially the progression to metastatic disease, have been noted over many years, Recently, a mouse model in which beta1,6-N-acetylglucosaminyltransferase V (a rate-limiting enzyme in the N-glycan pathway) has been knocked out, was used to demonstrate the importance of glycosylation in tumor progression. By crossing mice lacking this enzyme with a transgenic mouse model of metastatic breast cancer, metastatic progression of the disease was dramatically reduced. These experiments provide in vivo evidence for the role of N-linked glycosylation in metastatic breast cancer and have significant implications for the development of new treatment strategies.

Selective depletion of heat shock protein 70 (Hsp70) activates a tumor-specific death program that is independent of caspases and bypasses Bcl-2

Heat shock protein 70 is an antiapoptotic chaperone protein highly expressed in human breast tumors and tumor cell lines. Here, we demonstrate that the mere inhibition of its synthesis by adenoviral transfer or classical transfection of antisense Hsp70 cDNA (asHsp70) results in massive death of human breast cancer cells (MDA-MB-468, MCF-7, BT-549, and SK-BR-3), whereas the survival of nontumorigenic breast epithelial cells (HBL-100) or fibroblasts (WI-38) is not affected. Despite the apoptotic morphology as judged by electron microscopy, the asHsp70-induced death was independent of known caspases and the p53 tumor suppressor protein. Furthermore, Bcl-2 and Bcl-X(L), which protect tumor cells from most forms of apoptosis, failed to rescue breast cancer cells from asHsp70-induced death. These results show that tumorigenic breast cancer cells depend on the constitutive high expression of Hsp70 to suppress a transformation-associated death program. Neutralization of Hsp70 may open new possibilities for treatment of cancers that have acquired resistance to therapies activating the classical apoptosis pathway.

Fibrosis and angiogenesis

Research during the past few years has contributed vastly to a better understanding of fibrosis and angiogenesis. Although studies to understand the molecular processes associated with fibrosis and angiogenesis were performed independently of each other, some common parallels have emerged. Translation of these observations into potential therapeutic possibilities needs further exploration.

Genetics of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the human cancers clearly linked to viral infections. Although the major viral and environmental risk factors for HCC development have been unravelled, the oncogenic pathways leading to malignant transformation of liver cells have long remained obscure. Recent outcomes have been provided by extensive allelotype studies which resulted in a comprehensive overview of the main genetic abnormalities in HCC, including DNA copy gains and losses. The differential involvement of the p53 tumor-suppressor gene in tumors associated with various risk factors has been largely clarified. Evidence for a crucial role of the reactivation of the Wnt/beta-catenin pathway, through mutations in the beta-catenin and axin genes in 30-40% of liver tumors, represents a major breakthrough. It has also been shown that the Rb pathway is frequently disrupted by methylation-dependent silencing of the p16INK4A gene and stimulation of Rb degradation by a proteosomal subunit. Presently, the identification of candidate oncogenes and tumor suppressors in the most frequently altered chromosomal regions is a major challenge. Great insights will come from integrating the signals from different pathways operating at preneoplastic and neoplastic stages. This search might, in time, permit an accurate evaluation of the major targets for therapeutic treatments.

Interactions between tumour cells and stromal cells and proteolytic modification of the extracellular matrix by metalloproteinases in cancer

Over the last few years a growing number of matrix degrading metalloproteinases have been implicated in cancer. These include in particular the matrix metalloproteinases (MMPs) which have been shown to be associated with a large variety of human malignancies, and the metalloproteinases with a disintegrin domain (ADAMs) whose potential role in cancer has begun to be examined. The expression of MMPs in human cancer is the result of a complex interaction between tumour cells and non-malignant stromal cells including fibroblasts, endothelial cells and inflammatory cells which all actively participate in the production of MMPs in tumour tissue. The proteolytic modification of the extracellular matrix by these proteases does more than allow malignant cells to locally invade and form distant metastasis. It significantly alters the tumour micro-environment and modifies the contacts between tumour cells and extracellular matrix proteins. These changes can affect essential cellular functions such as growth, survival, migration and even drug resistance. As our understanding of the nature of the contacts between tumour cells and a proteolytically modified extracellular matrix continues to progress, it is likely that novel therapeutic approaches to modify tumour cell behaviour will be identified.

Regulation of [Ca(2+)](i) homeostasis in MRP1 overexpressing cells

Regulation of capacitative Ca(2+) entry was studied in two different multidrug resistance (MDR) protein (MRP1) overexpressing cell lines, HT29(col) and GLC4/ADR. MRP1 overexpression was accompanied by a decreased response to thapsigargin. Moreover, inhibition of capacitative Ca(2+) entry by D, L-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) was abolished in MRP1 overexpressing cells. Both PDMP and the MRP1 inhibitor MK571 greatly reduced InsP(3)-mediated (45)Ca(2+) release from intracellular stores in HT29 cells. Again, these effects were virtually abolished in HT29(col) cells. Our results point to a modulatory role of MRP1 on intracellular calcium concentration ([Ca(2+)](i)) homeostasis which may contribute to the MDR phenotype.

Hepatocellular carcinoma in WHV/N-myc2 transgenic mice: oncogenic mutations of beta-catenin and synergistic effect of p53 null alleles

The intronless N-myc2 gene was originally identified as the major target of hepatitis virus insertion in woodchuck liver tumors. Here we report that transgenic mice carrying the N-myc2 gene controlled by woodchuck hepatitis virus (WHV) regulatory sequences are highly predisposed to liver cancer. In a WHV/N-myc2 transgenic line, hepatocellular carcinomas or adenomas arose in over 70% of mice, despite barely detectable expression of the methylated transgene in liver cells. Furthermore, a transgenic founder carrying unmethylated transgene sequences succumbed to a large liver tumor by the age of two months, demonstrating the high oncogenicity of the woodchuck N-myc2 retroposon. Stabilizing mutations or deletions of beta-catenin were found in 25% of liver tumors and correlated with reduced tumor latency (P<0.05), confirming the important role of beta-catenin activation in Myc-induced tumorigenesis. The ability of the tumor suppressor gene p53 to cooperate with N-myc2 in liver cell transformation was tested by introducing a p53-null allele into WHV/N-myc2 transgenic mice. The loss of one p53 allele in transgenic animals markedly accelerated the onset of liver cancer (P=0.0001), and most tumors of WHV/N-myc2 p53+/Delta mice harbored either a deletion of the wt p53 allele or a beta-catenin mutation. These findings provide direct evidence that activation of N-myc2 and reduction of p53 levels act synergistically during multistage carcinogenesis in vivo and suggest that different genetic pathways may underlie liver carcinogenesis initiated by a myc transgene. Oncogene (2000).

The interferon regulatory factors and oncogenesis

We study a family of transcription factors, the interferon regulatory factors (IRFs), as originally identified in the context of the regulation of type-I interferon (IFN-alpha/beta) system. Most notably, studies on IRF-1 have revealed its remarkable functional diversity in the regulation of cellular responses of host defense, including oncogenesis. The IRF family has now expanded to nine members, and gene disruption studies have revealed critical involvement of some of the members in the regulation of cell growth and oncogenesis. In this review, we summarize our current knowledge on the involvement of members of the IRF family members, in particular, IRF-1, in oncogenesis.

Mechanism-based target identification and drug discovery in cancer research

Cancer as a disease in the human population is becoming a larger health problem, and the medicines used as treatments have clear limitations. In the past 20 years, there has been a tremendous increase in our knowledge of the molecular mechanisms and pathophysiology of human cancer. Many of these mechanisms have been exploited as new targets for drug development in the hope that they will have greater antitumor activity with less toxicity to the patient than is seen with currently used medicines. The fruition of these efforts in the clinic is just now being realized with a few encouraging results.

Exploring the relationship between neutral and selective mutations in cancer

The transformation of normal cells into cancerous cells is an evolutionary process. Populations of precancerous cells reproduce, mutate, and compete for resources. Some of these mutations eventually lead to cancer. We calculate the probability of developing cancer under a set of simplifying assumptions and then elaborate these calculations, culminating in a simple simulation of the cell dynamics. The agent-based model allows us to examine the interactions of mutations critical for the development of cancer that are either evolutionarily neutral or selective. We can also examine the interaction of these mutations with a "mutator phenotype" derived from mutations that raise the mutation rate for the entire cell. The simulations suggest that there must be at least two selectively neutral mutations necessary for the development of cancer and that preventive treatments will be most effective when they increase this number. The model also suggests that selective mutations facilitate the development of cancer, so that the more selective mutations necessary for the development of cancer, the greater the chance of developing it.

Keratin subunit expression in human cultured melanocytes and mouse neural crest cells without formation of filamentous structures

The synthesis of keratin is considered to occur in epithelial and epidermal cells. Previous studies have not reported on keratin synthesis within melanocytes that derive from neural crest cells. Epithelial and neural crest cells originally develop from ectodermal tissue. We previously reported that the expression of keratin is a universal phenomenon seen in cultured melanoma cell lines, as demonstrated by two-dimensional polyacrylamide gel electrophoresis, western blot, and electron microscopy analyses. To further investigate the specificity of keratin function in melanocytic cells, we first examined the presence of keratin proteins in cultured human melanocytes, and unexpectedly found keratin subunits in melanocytes by the above-mentioned procedures. The keratin (K) subunits were composed of K1, K5, K8, K10, K14, K16, and K18, together with vimentin. Neural crest cells, which contain immature embryonic melanocytes developing from ectoderm, already expressed keratins; however, under electron microscopy, the expressed keratin did not form filamentous structures. Although the ATP synthase alpha-chain, which is expressed universally in cultured epidermal tumor cell lines, was also expressed in cultured melanocytes and neural crest cells, a novel malignant melanoma-related protein (MMRP) was absent in melanocytes and neural crest cells. We concluded that keratin subunits are present in both cells, but do not construct keratin filaments.

Photosensitivity diseases: cutaneous lupus erythematosus

Ultraviolet radiation plays an important role in the induction of lesions in many patients with cutaneous lupus. In the photosensitive subset of lupus, subacute cutaneous lupus, the effects of ultraviolet radiation likely act in concert with specific autoantibodies, particularly anti-Ro-related autoantibodies, to produce lesions. Potential effects of ultraviolet radiation on the induction of cutaneous lupus, and the potential interplay of specific autoantibodies with ultraviolet radiation are discussed. The steps involved in the induction of cutaneous lupus lesions by ultraviolet radiation have not been fully elucidated. Recent advances in phototesting and analysis of the genetics of lupus should clarify the events leading to photosensitive cutaneous lupus lesions.

Histochemical and biochemical observations on the cytotoxicity of paracetamol and its effects on glycogen metabolism in rat liver

The effects of paracetamol overdose on glycogen metabolism in rat liver have been investigated and related to its cytotoxicity. Paracetamol was administered to male rats by gavaging after a 24-h fast and refeeding was not permitted. An early (9-12-h) increase in histochemically demonstrable glycogen phosphorylase alpha activity in perivenous hepatocytes preceded major loss of membrane integrity as assessed by serum glutamate-pyruvate transaminase (SGPT) activity and uptake of trypan blue during perfusion. These changes occurred only after a decrease in the concentration of reduced glutathione, which is generally observed about 4 h after paracetamol treatment. The activation of glycogen phosphorylase in perivenous hepatocytes occurred concurrently with an increase in glycogen content of periportal hepatocytes, indicating a clear heterogeneity in the response of the two-cell populations to the hepatotoxin. The use of trypan blue perfusion together with histochemical techniques allowed changes in glycogen content and phosphorylase alpha activity of individual hepatocytes to be assessed with reference to the extent of membrane damage evident. The relevance of the results to possible mechanisms of hepatotoxicity is discussed.

Conformational effects of volatile anesthetics on the membrane-bound acetylcholine receptor protein: facilitation of the agonist-induced affinity conversion

The rate of the carbamylcholine-induced affinity conversion of the membrane-bound acetylcholine receptor protein from Torpedo californica is enhanced by pretreatment of the membranes under an atmosphere of 3% halothane or 1% chloroform. The enhancement is much more pronounced in the presence of low rather than high concentrations of carbamylcholine since the volatile anesthetics alter the apparent dissociation constant for carbamylcholine from 17 to 3 microM without affecting the first-order rate constant for the ligand-induced conversion (0.07 s-1). These results indicate that the acetylcholine receptor is assuming a conformational form with intermediate affinity for carbamylcholine in addition to the previously described low- and high-affinity forms. The dissociation constants for carbamylcholine obtained from kinetic studies of the carbamylcholine-induced transition are 3-15-fold lower than those obtained as inhibition constants from the rate of 125I-labeled alpha-bungarotoxin binding to the low-affinity conformer of the acetylcholine receptor protein. This pattern, observed in both the presence and absence of anesthetic, provides further evidence that the acetylcholine receptor has nonequivalent ligand binding sites for carbamylcholine.

Iron granules in plasma cells

Resistance of cancer cells to chemotherapy is the first cause of cancer-associated death. Thus, new strategies to deal with the evasion of drug response and to improve clinical outcomes are needed. Genetic and epigenetic mechanisms associated with uncontrolled cell growth result in metabolism reprogramming. Cancer cells enhance anabolic pathways and acquire the ability to use different carbon sources besides glucose. An oxygen and nutrient-poor tumor microenvironment determines metabolic interactions among normal cells, cancer cells and the immune system giving rise to metabolically heterogeneous tumors which will partially respond to metabolic therapy. Here we go into the best-known cancer metabolic profiles and discuss several studies that reported tumors sensitization to chemotherapy by modulating metabolic pathways. Uncovering metabolic dependencies across different chemotherapy treatments could help to rationalize the use of metabolic modulators to overcome therapy resistance.