Glucose transporter-1 (GLUT-1): a potential marker of prognosis in rectal carcinoma?

Glucose transporter Glut-1 is detectable in peri-necrotic regions in many human tumor types but not normal tissues: Study using tissue microarrays

The hypoxic tumor microenvironment is associated with malignant progression and poor treatment response. The glucose transporter Glut-1 is a prognostic factor and putative hypoxia marker. So far, studies of Glut-1 in cancer have utilized conventional immunohistochemical analysis in a series of individual biopsy or surgical specimens. Tissue microarrays, however, provide a rapid, inexpensive means of profiling biomarker expression. To evaluate hypoxia markers, tissue cores must show the architectural features of hypoxia; i.e. viable tissue surrounding necrotic regions. Glut-1 may be a useful biomarker to validate tissue microarrays for use in studies of hypoxia-regulated genes in cancer. In this study, we carried out immunohistochemical detection of Glut-1 protein in many tumor and normal tissue types in a range of tissue microarrays. Glut-1 was frequently found in peri-necrotic regions, occurring in 9/34 lymphomas, 6/12 melanomas, and 5/16 glioblastomas; and in 43/54 lung, 22/84 colon, and 23/60 ovarian tumors. Expression was rare in breast (6/40) and prostate (1/57) tumors, and in normal tissue, was restricted to spleen, tongue, and CNS endothelium. In conclusion, tissue microarrays enable the observation of Glut-1 expression in peri-necrotic regions, which may be linked to hypoxia, and reflect previous studies showing differential Glut-1 expression across tumor types and non-malignant tissue.

Expression of cyclooxygenase-2, glucose transporter-1 and angiogenesis in gallbladder carcinomas and their impact on prognosis

OBJECTIVE

To investigate the angiogenic and prognostic role of cyclooxygenase-2 (COX-2) in gallbladder carcinomas. We assume COX-2 overexpression, neoangiogenesis and glucose transporter-1 (GLUT-1) to be involved in disease progression.

MATERIAL AND METHODS

The carcinoma tissues of 56 patients with gallbladder carcinomas were studied immunohistochemically for the expression of COX-2, GLUT-1 and micro-vessel density. The results were correlated with clinico-pathological features and survival/prognosis.

RESULTS

The overexpression of COX-2 in gallbladder carcinomas was significantly associated with increased angiogenesis and GLUT-1 expression. Neither angiogenesis nor the grade of the tumour correlate significantly with poor survival. Age, gender and a strong GLUT-1 expression were significant factors of adverse prognosis.

CONCLUSIONS

Next to age and gender of patients, hypoxia of gallbladder tumours is a factor influencing survival. Among hypoxic factors, GLUT-1 expression is an important (significant) denominator of poor prognosis in gallbladder carcinomas, but not COX-2 nor angiogenesis.

Inhibition of cell proliferation and glucose uptake in human laryngeal carcinoma cells by antisense oligonucleotides against glucose transporter-1

BACKGROUND

Malignant cells show increased glucose uptake in vitro and in vivo, which is thought to be mediated by glucose transporters. In this study, we investigated the effect of plasmid-derived antisense RNA against the Glut-l gene on proliferation and glucose uptake in laryngeal carcinoma Hep-2 cells.

METHODS

The expression plasmids pcDNA3.1(+)-Glut-1 and pcDNA3.1(+)-anti Glut-1 were constructed. The MTT method was used to assess cell growth inhibition. The expression of Glut-1 mRNA and protein was detected by reverse transcriptase-polymerase chain reaction and Western blotting, respectively.

RESULTS

After transfection, Glut-1 AS clearly inhibited glucose uptake and cell growth in Hep-2 cells, and we observed a decrease in the expression of Glut-1 mRNA and protein in Hep-2 cells.

CONCLUSIONS

Glut-1 AS decreases glucose uptake and inhibits the proliferation of Hep-2 cells.

Potential role of sugar transporters in cancer and their relationship with anticancer therapy

Sugars, primarily glucose and fructose, are the main energy source of cells. Because of their hydrophilic nature, cells use a number of transporter proteins to introduce sugars through their plasma membrane. Cancer cells are well known to display an enhanced sugar uptake and consumption. In fact, sugar transporters are deregulated in cancer cells so they incorporate higher amounts of sugar than normal cells. In this paper, we compile the most significant data available about biochemical and biological properties of sugar transporters in normal tissues and we review the available information about sugar carrier expression in different types of cancer. Moreover, we describe the possible pharmacological interactions between drugs currently used in anticancer therapy and the expression or function of facilitative sugar transporters. Finally, we also go into the insights about the future design of drugs targeted against sugar utilization in cancer cells.

GLUT-1 expression and response to chemoradiotherapy in rectal cancer

Preoperative chemoradiotherapy is used in locally advanced rectal cancer to reduce local recurrence and improve operability, however a proportion of tumors do not undergo significant regression. Identification of predictive markers of response to chemoradiotherapy would improve patient selection and may allow response modification by targeting of specific pathways. The aim of this study was to determine whether expression of glucose transporter-1 (GLUT-1) and p53 in pretreatment rectal cancer biopsies was predictive of tumor response to chemoradiotherapy. Immunohistochemical staining for GLUT-1 and p53 was performed on 69 pretreatment biopsies and compared to tumor response in the resected specimen as determined by the tumor regression grade (TRG) scoring system. GLUT-1 expression was significantly associated with reduced response to chemoradiotherapy and increasing GLUT expression correlated with poorer response (p=0.02). GLUT-1 negative tumors had a 70% probability of good response (TRG3/4) compared to a 31% probability of good response in GLUT-1 positive tumors. GLUT-1 may be a useful predictive marker of response to chemoradiotherapy in rectal cancer.

Relations of TGF-beta1 with HIF-1 alpha, GLUT-1 and longer survival of colorectal cancer patients

AIMS AND METHODS

During colorectal carcinogenesis, transforming growth factor beta 1 (TGF-beta1) undergoes a functional change from suppression of cancer cell proliferation to inhibition of T cell mediated anti-cancer immunity. We aimed to evaluate relations among TGF-beta1 and cancer cell survival factors hypoxia inducible factor-1 alpha (HIF-1 alpha) and glucose transporter 1 (GLUT-1) by immunohistochemistry in 108 colorectal cancers.

RESULTS

TGF-beta1 was detected in 87% (94/108), HIF-1 alpha in 85% (92/108), and GLUT-1 in 65% (70/108) of colorectal cancers. Not only did TGF-beta1 accumulate in cytoplasm of cancer cells but also there was strong immunoreactivity to TGF-beta1 in adjacent inflammatory cells. GLUT-1 was visualised in a membranous fashion while HIF-1 was expressed in a paranuclear pattern and occasionally in nuclei of malignant cells. Cancer immunoreactivities to TGF-beta1 correlated with HIF-1 alpha (p < 0.001, r = 0.516) and GLUT-1 (p < [corrected] 0.001, r = 0.355) in general and subgroups of different clinicopathological traits. TGF-beta1 expressions of inflammatory infiltrates correlated with longer patient survival (p = 0.05, r = 0.449) and immunoreactivities to HIF-1 alpha of cancer cells (p = 0.008, r = 0.254) particularly in node positive and deeply invading cancers but failed to associate significantly with GLUT-1.

CONCLUSIONS

HIF-1 alpha and GLUT-1 could cooperate with TGF-beta1, and TGF-beta1 might mediate cross-talk between the inflammatory environment and tumour with a favourable impact on patient survival.

Brain tumor hypoxia: tumorigenesis, angiogenesis, imaging, pseudoprogression, and as a therapeutic target

Hypoxia is implicated in many aspects of tumor development, angiogenesis, and growth in many different tumors. Brain tumors, particularly the highly aggressive glioblastoma multiforme (GBM) with its necrotic tissues, are likely affected similarly by hypoxia, although this involvement has not been closely studied. Invasion, apoptosis, chemoresistance, resistance to antiangiogenic therapy, and radiation resistance may all have hypoxic mechanisms. The extent of the influence of hypoxia in these processes makes it an attractive therapeutic target for GBM. Because of their relationship to glioma and meningioma growth and angiogenesis, hypoxia-regulated molecules, including hypoxia inducible factor-1, carbonic anhydrase IX, glucose transporter 1, and vascular endothelial growth factor, may be suitable subjects for therapies. Furthermore, other novel hypoxia-regulated molecules that may play a role in GBM may provide further options. Emerging imaging techniques may allow for improved determination of hypoxia in human brain tumors to better focus therapeutic treatments; however, tumor pseudoprogression, which may be prompted by hypoxia, poses further challenges. An understanding of the role of hypoxia in tumor development and growth is important for physicians involved in the care of patients with brain tumors.

GLUT1 expression is increased in hepatocellular carcinoma and promotes tumorigenesis

Accelerated glycolysis is one of the biochemical characteristics of cancer cells. The glucose transporter isoform 1 (GLUT1) gene encodes a key rate-limiting factor in glucose transport into cancer cells. However, its expression level and functional significance in hepatocellular cancer (HCC) are still disputed. Therefore, we aimed to analyze the expression and function of the GLUT1 gene in cases of HCC. We found significantly higher GLUT1 mRNA expression levels in HCC tissues and cell lines compared with primary human hepatocytes and matched nontumor tissue. Immunohistochemical analysis of a tissue microarray of 152 HCC cases revealed a significant correlation between Glut1 protein expression levels and a higher Ki-67 labeling index, advanced tumor stages, and poor differentiation. Accordingly, suppression of GLUT1 expression by siRNA significantly impaired both the growth and migratory potential of HCC cells. Furthermore, inhibition of GLUT1 expression reduced both glucose uptake and lactate secretion. Hypoxic conditions further increased GLUT1 expression levels in HCC cells, and this induction was dependent on the activation of the transcription factor hypoxia-inducible factor-1alpha. In summary, our findings suggest that increased GLUT1 expression levels in HCC cells functionally affect tumorigenicity, and thus, we propose GLUT1 as an innovative therapeutic target for this highly aggressive tumor.

Colorectal tumor vascularity: quantitative assessment with multidetector CT--do tumor perfusion measurements reflect angiogenesis?

PURPOSE

To establish the relationships between quantitative perfusion computed tomography (CT) parameters-specifically, primary tumor blood flow, blood volume, transit time, and permeability surface-area product-and immunohistologic markers of angiogenesis in colorectal cancer.

MATERIALS AND METHODS

After institutional review board approval and informed patient consent were obtained for this prospective study, 23 patients (11 men, 12 women; mean age, 68.4 years; age range, 34.8-87.1 years) with colorectal adenocarcinoma underwent a 65-second perfusion CT examination, and tumor blood flow, blood volume, mean transit time, and permeability surface-area product were determined. After surgery, resected specimens were sectioned and stained immunohistochemically to identify CD34 for quantification of microvessel density (MVD), to identify smooth muscle actin for assessment of pericyte coverage index, to identify vascular endothelial growth factor (VEGF), and to identify glucose transporter protein (GLUT-1). Perfusion CT measurements were correlated with MVD, pericyte coverage index, VEGF expression, and GLUT-1 expression by using Pearson or Spearman rank correlation analysis, with significance assigned at the 5% level.

RESULTS

Mean blood flow, blood volume, transit time, and permeability surface-area product values were 72.1 mL/min/100 g of tissue +/- 28.4 (standard deviation), 6.2 mL/100 g of tissue +/- 1.4, 9.3 seconds +/- 3.9, and 13.9 mL/min/100 g of tissue +/- 3.2, respectively. Blood volume (r = 0.59, P = .002) and permeability surface-area product (r = 0.46, P = .03) correlated positively with MVD, but blood flow (r = 0.27, P = .22) and transit time (r = -0.18, P = .44) did not. There were no significant associations between any perfusion CT parameter and pericyte coverage index (r <or= 0.36, P > .05), VEGF score (rho <or= 0.30, P >or= .15), or GLUT-1 score (rho < 0.21, P >or= .33).

CONCLUSION

Tumor permeability surface-area product and blood volume correlate positively with MVD and may reflect the microvascularity of colorectal tumors.

Molecular imaging: reporter gene imaging

Non-invasive in-vivo molecular genetic imaging developed over the past decade and predominantly utilises radiotracer (PET, gamma camera, autoradiography), magnetic resonance and optical imaging technology. Molecular genetic imaging has its roots in both molecular biology and cell biology. The convergence of these disciplines and imaging modalities has provided the opportunity to address new research questions, including oncogenesis, tumour maintenance and progression, as well as responses to molecular-targeted therapy. Three different imaging strategies are described: (1) "bio-marker" or "surrogate" imaging; (2) "direct" imaging of specific molecules and pathway activity; (3) "indirect" reporter gene imaging. Examples of each imaging strategy are presented and discussed. Several applications of PET- and optical-based reporter imaging are demonstrated, including signal transduction pathway monitoring, oncogenesis in genetic mouse models, endogenous molecular genetic/biological processes and the response to therapy in animal models of human disease. Molecular imaging studies will compliment established ex-vivo molecular-biological assays that require tissue sampling by providing a spatial and a temporal dimension to our understanding of disease development and progression, as well as response to treatment. Although molecular imaging studies are currently being performed primarily in experimental animals, we optimistically expect they will be translated to human subjects with cancer and other diseases in the near future.

The potential role of intrinsic hypoxia markers as prognostic variables in cancer

Tumor hypoxia is related to tumor progression and therapy resistance, which leads to poor patient outcome. It has been suggested that measuring the hypoxic status of a tumor helps to predict patient outcome and to select more targeted treatment. However, current methods using needle electrodes or exogenous markers have limitations due to their invasiveness or necessity for preinjection. Recent studies showed that hypoxia-regulated genes could be alternatively used as endogenous hypoxia markers. This is a review of 15 hypoxia-regulated genes, including hypoxia-inducible factor-1 and its targets, and their correlation with tumor hypoxia and patient outcome from 213 studies. Though most of the studies showed significance of these genes in predicting prognosis, there was no definitive prognostic and hypoxia marker. In conclusion, this review suggests the need for further studies with standardized methods to examine gene expression, as well as the use of multiple gene expressions.

Hypoxic regulation of glucose transport, anaerobic metabolism and angiogenesis in cancer: novel pathways and targets for anticancer therapeutics

Cancer cells require a steady source of metabolic energy in order to continue their uncontrolled growth and proliferation. Accelerated glycolysis is one of the biochemical characteristics of cancer cells. Recent work indicates that glucose transport and metabolism are essential for the posttreatment survival of tumor cells, leading to poor prognosis. Glycolytic breakdown of glucose is preceded by the transport of glucose across the cell membrane, a rate-limiting process mediated by facilitative glucose transporter proteins belonging to the facilitative glucose transporter/solute carrier GLUT/SLC2A family. Tumors frequently show overexpression of GLUTs, especially the hypoxia-responsive GLUT1 and GLUT3 proteins. There are also studies that have reported associations between GLUT expression and proliferative indices, whilst others suggest that GLUT expression may be of prognostic significance. In this article we revisit Warburg's original hypothesis and review the recent clinical and basic research on the expression of GLUT family members in human cancers and in cell lines derived from human tumors. We also explore the links between hypoxia-induced genes, glucose transporters and angiogenic factors. Hypoxic tumors are significantly more malignant, metastatic, radio- and chemoresistant and have a poor prognosis. With the discovery the oxygen-sensitive transcription factor hypoxia-inducible factor (HIF-1) has come a new understanding of the molecular link between hypoxia and deregulated glucose metabolism. HIF-1 induces a number of genes integral to angiogenesis, e.g. vascular endothelial growth factor (VEGF), a process intimately involved with metastatic spread. This knowledge may enhance existing chemotherapeutic strategies so that treatment can be more rationally applied and personalized for cancer patients.

Glut-1 as a therapeutic target: increased chemoresistance and HIF-1-independent link with cell turnover is revealed through COMPARE analysis and metabolomic studies

The facilitative glucose transporter Glut-1 is overexpressed and confers poor prognosis in a wide range of solid tumours. The peri-necrotic pattern of expression often seen in human tumour samples is linked with its transcriptional control in hypoxic conditions by hypoxia-inducible factor HIF-1 or through a reduced rate of oxidative phosphorylation. Hypoxia-regulated genes offer promise as novel therapeutic targets as a means of preventing the proliferation and eventual metastatic spread of tissue originating from residual chemically and radio resistant hypoxic cells that have survived treatment. Inhibiting the expression or functionality of Glut-1 may be a way of specifically targeting hypoxic cells within the tumour that depend upon a high rate of glucose uptake for anaerobic glycolysis. We used an array of formalin-fixed, paraffin-embedded samples of the NCI-60 panel of cell lines to carry out immunohistochemical detection of Glut-1 and to select possible candidate lead compounds by COMPARE analysis with agents from the NCI diversity screen, which may work via inhibition of Glut-1 or Glut-1-dependent processes. "Positive" COMPARE hits were mostly conjugated Pseudomonas toxins binding the epidermal growth factor receptor (EGFR). However, correlations with standard anticancer agents were virtually all negative, indicating a link between Glut-1 and chemoresistance. MTT proliferation assays carried out using stable, Glut-1 overexpressing cell lines generated from the bladder EJ138, human fibrosarcoma HT 1080 and the hepatoma wild type Hepa and HIF-1B-deficient c4 tumour cell lines revealed a cell line-dependent increase in chemoresistance to dacarbazine, vincristine and the bioreductive agent EO9 in Glut-1 overexpressing EJ138 relative to WT and empty vector controls. Metabolomic analysis ((31)P-MRS and (1)H MRS) carried out using cell lysates and xenografts generated from Glut-1 overexpressing Hepa and c4 cell lines showed higher glucose levels in Glut-1 overxpressing c4 relative to parental tumour extracts occurred in the absence of an increase in lactate levels, which were in turn significantly higher in the Glut-1 overexpressing Hepa xenografts. This implies that Glut-1 over-expression without a co-ordinate increase in HIF-1-regulated glycolytic enzymes increases glucose uptake but not the rate of glycolysis. Glut-1 overexpressing xenografts also showed higher levels of phosphodiester (PDE), which relates to the metabolite turnover of phospholipids and is involved in membrane lipid degradation, indicating a mechanism by which Glut-1 may increase cell turnover.

Clinicopathological significance and linkage of the distribution of HIF-1alpha and GLUT-1 in human primary colorectal cancer

HIF-1alpha induces GLUT-1 expression, and their presence has been evaluated in colorectal cancer. However, the expressions of GLUT-1 and HIF-1alpha have not been investigated together with reference to clinicopathological characteristics in human colorectal cancer. The aim of our study was to compare the expression of HIF-1alpha and GLUT-1 with various clinicopathological features of colorectal cancer. The presence of HIF-1alpha and GLUT-1 was visualized immunohistochemically in 123 primary tumors. Membranous localization of GLUT-1 was found in multifocally necrotizing cancer samples, while pure cytoplasmic perinuclear, mostly supranuclear GLUT-1 accumulation was characteristic of cancer fields with lack of necrosis. HIF-1alpha was located in the cytoplasm and occasionally in the nuclei of cancer cells. Immunoreactivity to GLUT-1 was significantly higher in node-positive cancers compared with nodenegative ones (p=0.04), confirming our earlier results obtained on a larger number of patients. Non-mucinous adenocarcinomas expressed GLUT-1 and HIF-1alpha with significantly greater frequency than mucinous adenocarcinomas (p=0.002, p=0.0002, respectively). GLUT-1 and HIF-1alpha expression did not differ in relation to tumor stage, location, or patients' age or gender. In contrast to that of GLUT-1, expression of HIF-1alpha correlated with grade (p=0.00003) without difference with regard to pN status. HIF-1alpha expression correlated with GLUT-1 expression in the whole patient population, as well as in all clinicopathological groups except for the pT1+pT2 group. Although the coexpression of cytoplasmic HIF-1alpha and GLUT-1 does not directly prove the dependence between HIF-1 as a nuclear transcriptional factor and GLUT-1 as its downstream protein, it is evidence of their simultaneous upregulation. The extranuclear accumulation of HIF-1alpha and GLUT-1 requires further studies to explain its significance in colorectal cancer.

Significant Coexpression of GLUT-1, Bcl-xL, and Bax in Colorectal Cancer

Hypoxic cancer cells overexpress Glucose transporter 1 (GLUT-1) to accelerate glucose intake mainly for low effective, anaerobic respiration, so that they would not die of oxygen deficiency. Ischemic cell injury triggers apoptosis. Regulators of cell suicide like Bax and Bcl-xL combine their functions to cause apoptosis or to rescue cells from death. GLUT-1, Bax, and Bcl-xL are of prognostic significance in colorectal cancer but they have not been compared, yet. Thus, we aimed to determine eventual correlations between GLUT-1, Bax, and Bcl-xL in association with different clinicopathological features of colorectal cancer patients. Expressions of the proteins were evaluated in specimens of 150 colorectal patients by immunohistochemistry. The levels of tissue expressions were statistically analyzed with Spearman's correlation test. As in group of all the patients, GLUT-1 matched Bcl-xL and Bax in statistically significant manner regardless of different node status, grade of histological differentiation, histopathological type, tumor site, gender and age of patients. GLUT-1 correlated highly with Bcl-xL in both groups of various tumor growth extent: pT1 + pT2 and pT3 + pT4 tumors (P < 0.016, r = 0.6340, P < 0.0001, r = 0.5204, respectively). Bax correlated with GLUT-1 (P < 0.0001, r = 0.4284) and Bcl-xL (P < 0.0001, r = 0.5233) in pT3 and pT4 tumors without any statistical significance in a homologous comparison at pT1 and pT2 stage (P > 0.173, r = 0.1078, P > 0.744, r = 0.1, respectively). Significant coexpression of GLUT-1, Bcl-xL, and Bax could point to cooperation of these regulatory proteins in elimination due to irreversible injury, adaptation to hypoxia, reduction of further damage, and survival of colorectal cancer cells.

Mitochondrial DNA mutations in human cancer

Somatic mitochondrial DNA (mtDNA) mutations have been increasingly observed in primary human cancers. As each cell contains many mitochondria with multiple copies of mtDNA, it is possible that wild-type and mutant mtDNA can co-exist in a state called heteroplasmy. During cell division, mitochondria are randomly distributed to daughter cells. Over time, the proportion of the mutant mtDNA within the cell can vary and may drift toward predominantly mutant or wild type to achieve homoplasmy. Thus, the biological impact of a given mutation may vary, depending on the proportion of mutant mtDNAs carried by the cell. This effect contributes to the various phenotypes observed among family members carrying the same pathogenic mtDNA mutation. Most mutations occur in the coding sequences but few result in substantial amino acid changes raising questions as to their biological consequence. Studies reveal that mtDNA play a crucial role in the development of cancer but further work is required to establish the functional significance of specific mitochondrial mutations in cancer and disease progression. The origin of somatic mtDNA mutations in human cancer and their potential diagnostic and therapeutic implications in cancer are discussed. This review article provides a detailed summary of mtDNA mutations that have been reported in various types of cancer. Furthermore, this review offers some perspective as to the origin of these of mutations, their functional consequences in cancer development, and possible therapeutic implications.

Effect of drug-induced cytotoxicity on glucose uptake in Hodgkin's lymphoma cells

BACKGROUND

In Hodgkin's lymphoma, F-18-fluoro-deoxy-d-glucose positron emission tomography (FDG-PET) is used for staging and response evaluation after chemotherapy. However, drug-mediated downregulation of glucose uptake in viable Hodgkin's lymphoma cells might limit the use of FDG-PET.

METHODS

We analyzed the effect of etoposide on cell viability and uptake of F-18-fluoro-deoxy-D-glucose or the glucose analog 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxyglucose (2-NBDG) in vitro.

RESULTS

Etoposide induced a dose-dependent cytotoxicity in HDLM-2 cells which was significantly correlated with reduced FDG uptake. However, it also significantly increased the portion of viable cells which did not take up 2-NBDG. Interestingly, etoposide-induced cytotoxicity was mainly mediated via caspase-dependent mechanisms, whereas the cell death induced by deprivation of glucose was mediated via caspase-independent mechanisms.

CONCLUSION

Etoposide-mediated reduction of glucose uptake by Hodgkin's lymphoma cells is mainly caused by cell death. In a small fraction of viable cells, etoposide might downregulate glucose transporters and/or hexokinase activity and by that inhibit glucose uptake. This, however, might not lead to false-negative results of response evaluation in Hodgkin's lymphoma patients after chemotherapy, because inhibition of glucose uptake itself seems to be a strong inducer of cell death. Altogether, this study provides important in vitro evidence to clarify the mechanisms by which FDG-PET monitors the effect of anti-cancer treatment in Hodgkin's lymphoma patients.

Hypoxia in the tumorigenesis of gliomas and as a potential target for therapeutic measures

✓ In this article, the author provides a brief description of the role of hypoxia in the tumorigenesis of gliomas and suggests potential ways of exploiting this role to design treatment modalities. Tumor hypoxia predicts the likelihood of metastases, tumor recurrence, resistance to chemotherapy and radiation therapy, invasive potential, and decreased patient survival for many human malignancies. Various methods of measurement of tumor hypoxia are discussed, including direct measurement and imaging methods.

The role of hypoxia-responsive molecules, especially hypoxia-inducible factor-1 (HIF-1), in glioma tumorigenesis is explored. Treatment modalities regulated by hypoxia are proposed and some potential strategies reviewed. The progression of a low-grade astrocytoma to a glioblastoma multiforme may be mediated by hypoxia-induced phenotypic changes and subsequent clonal selection of cells that overexpress hypoxia-responsive molecules, such as HIF-1. In this model, intratumoral hypoxia causes genetic changes that produce a microenvironment that selects for cells of a more aggressive phenotype.

Metabolism and transport of oxazaphosphorines and the clinical implications

The oxazaphosphorines including cyclophosphamide (CPA), ifosfamide (IFO), and trofosfamide represent an important group of therapeutic agents due to their substantial antitumor and immuno-modulating activity. CPA is widely used as an anticancer drug, an immunosuppressant, and for the mobilization of hematopoetic progenitor cells from the bone marrow into peripheral blood prior to bone marrow transplantation for aplastic anemia, leukemia, and other malignancies. New oxazaphosphorines derivatives have been developed in an attempt to improve selectivity and response with reduced toxicity. These derivatives include mafosfamide (NSC 345842), glufosfamide (D19575, beta-D-glucosylisophosphoramide mustard), NSC 612567 (aldophosphamide perhydrothiazine), and NSC 613060 (aldophosphamide thiazolidine). This review highlights the metabolism and transport of these oxazaphosphorines (mainly CPA and IFO, as these two oxazaphosphorine drugs are the most widely used alkylating agents) and the clinical implications. Both CPA and IFO are prodrugs that require activation by hepatic cytochrome P450 (CYP)-catalyzed 4-hydroxylation, yielding cytotoxic nitrogen mustards capable of reacting with DNA molecules to form crosslinks and lead to cell apoptosis and/or necrosis. Such prodrug activation can be enhanced within tumor cells by the CYP-based gene directed-enzyme prodrug therapy (GDEPT) approach. However, those newly synthesized oxazaphosphorine derivatives such as glufosfamide, NSC 612567 and NSC 613060, do not need hepatic activation. They are activated through other enzymatic and/or non-enzymatic pathways. For example, both NSC 612567 and NSC 613060 can be activated by plain phosphodiesterase (PDEs) in plasma and other tissues or by the high-affinity nuclear 3'-5' exonucleases associated with DNA polymerases, such as DNA polymerases and epsilon. The alternative CYP-catalyzed inactivation pathway by N-dechloroethylation generates the neurotoxic and nephrotoxic byproduct chloroacetaldehyde (CAA). Various aldehyde dehydrogenases (ALDHs) and glutathione S-transferases (GSTs) are involved in the detoxification of oxazaphosphorine metabolites. The metabolism of oxazaphosphorines is auto-inducible, with the activation of the orphan nuclear receptor pregnane X receptor (PXR) being the major mechanism. Oxazaphosphorine metabolism is affected by a number of factors associated with the drugs (e.g., dosage, route of administration, chirality, and drug combination) and patients (e.g., age, gender, renal and hepatic function). Several drug transporters, such as breast cancer resistance protein (BCRP), multidrug resistance associated proteins (MRP1, MRP2, and MRP4) are involved in the active uptake and efflux of parental oxazaphosphorines, their cytotoxic mustards and conjugates in hepatocytes and tumor cells. Oxazaphosphorine metabolism and transport have a major impact on pharmacokinetic variability, pharmacokinetic-pharmacodynamic relationship, toxicity, resistance, and drug interactions since the drug-metabolizing enzymes and drug transporters involved are key determinants of the pharmacokinetics and pharmacodynamics of oxazaphosphorines. A better understanding of the factors that affect the metabolism and transport of oxazaphosphorines is important for their optional use in cancer chemotherapy.

Hypoxia in relation to vasculature and proliferation in liver metastases in patients with colorectal cancer

PURPOSE

To investigate hypoxia measured by pimonidazole binding, glucose transporter 1 (GLUT1) and carbonic anhydrase IX (CA-IX) expression, proliferation, and vascularity in liver metastases of colorectal cancer and to compare GLUT1 and CA-IX expression in corresponding primary tumors.

METHODS AND MATERIALS

Twenty-five patients with liver metastases of colorectal cancer, planned for metastasectomy, were included. The hypoxia marker pimonidazole and proliferation marker iododeoxyuridine were administered before surgery. After immunofluorescent staining of the frozen metastases, pimonidazole binding, vascularity, and proliferation were analyzed quantitatively. Thirteen paraffin-embedded primary tumors were stained immunohistochemically for GLUT1 and CA-IX expression, which was analyzed semiquantitatively in primary tumors and corresponding liver metastases.

RESULTS

In liver metastases, pimonidazole binding showed a pattern consistent with diffusion-limited hypoxia. The mean pimonidazole-positive fraction was 0.146; the mean distance from vessels to pimonidazole-positive areas was 80 microm. When expressed, often co-localization was observed between pimonidazole binding and GLUT1 or CA-IX expression, but microregional areas of mismatch were also observed. No correlation between the level of pimonidazole binding and GLUT1 or CA-IX expression was observed. In some patients, a large fraction (up to 30%) of proliferating cells was present in pimonidazole-stained areas. Expression of CA-IX in primary tumors and metastases showed a significant correlation, which was absent for GLUT1 expression.

CONCLUSIONS

Compared with other tumor types, liver metastases of colorectal cancer contain large amounts of hypoxic cells. The lack of correlation with pimonidazole binding brings into question the value of GLUT1 and CA-IX as endogenous markers of hypoxia.

Staging of colorectal cancer: past, present, and future

Since the inception of staging for colorectal cancer (CRC), anatomic extent of disease has provided a solid foundation for predicting prognosis and guiding treatment in patients with CRC. However, the rapid advances in biologic and genetic technology have provided many new possibilities for enhancing the predictive power of the staging system. In this article, we will briefly discuss the history of CRC staging, identify the current parameters for American Joint Committee on Cancer staging including recent changes, and offer guidelines for future staging modifications. Although anatomic parameters have served us well for many years, their continued use as sole contributors to CRC staging is questionable. Staging in the future is likely to be a complicated combination of anatomic and biologic markers used together in mathematic modeling to group patients into prognostic risk groups, which can be used to guide tailored therapy.

Microregional Expression of Glucose Transporter-1 and Oxygenation Status: Lack of Correlation in Locally Advanced Cervical Cancers

PURPOSE

Glucose transporter-1 (GLUT-1), a target gene of hypoxia-inducible factor-1, has been considered a candidate endogenous marker of tumor hypoxia. Expression of GLUT-1 may also serve as an indicator for the induction of the transcriptional response to hypoxia, which has been linked to enhanced proliferation, resistance to therapy, and metastatic propagation of cancer cells. Overexpression of GLUT-1 has been shown to correlate with poor prognosis in several tumor entities, among them cancers of the uterine cervix. The validity of these hypotheses is investigated.

EXPERIMENTAL DESIGN

The expression of GLUT-1 was assessed in 80 biopsies of Eppendorf oxygenation measurement tracks from locally advanced cervical cancers in 47 patients using immunohistochemistry.

RESULTS

No correlation was found between the expression of GLUT-1 and oxygenation variables (median pO2, HF 2.5 and HF 5). Expression of GLUT-1 was found greater in larger tumors (P = 0.0001) and to exhibit a linear increase with Federation Internationale de Gynecologie et d' Obstetrique stage (P = 0.002). Overall survival (P = 0.004) and recurrence-free survival (P = 0.007) were significantly shorter for patients with expression of GLUT-1. In the subgroup of patients treated with surgery, this effect on prognosis was not independent when pT stage or pN stage were included in a multivariate Cox proportional hazards model.

CONCLUSIONS

The suitability of GLUT-1 as an endogenous marker of tumor hypoxia seems questionable. The association with prognosis may partially depend on confounding factors.

Tumor oxygenation status as a prognostic marker

Tumor oxygenation status is an independent prognostic indicator in cancer because it influences tumor progression and treatment outcome. Its quantitative value is determined by a number of tumor vascular parameters such as microvascular density, blood flow, blood volume, blood oxygen saturation, tumor tissue pO2, and resistance to oxygen diffusion within the tumor. Over the past several years, considerable time and effort have been invested into developing techniques to effectively and reliably measure the oxygenation status of a tumor. The measurement and interpretation of data obtained with currently available methods is complicated by the heterogeneity in tumor oxygenation. Currently available techniques can be broadly classified into direct invasive methods, direct non-invasive methods, and measurement of surrogate endogenous markers of tumor oxygenation. Of these methods, the Eppendorf pO2 histograph is considered the 'gold standard' and even so has several limitations. Given the importance of tumor oxygenation status in therapy and in predicting disease progression, it is imperative that reliable, globally usable, and technically simplistic methods be developed to yield a consistent, comprehensive, and reliable profile of tumor oxygenation. Until newer more reliable techniques are developed, existing independent techniques or appropriate combinations of techniques should be optimized and validated using known endpoints in tumor oxygenation status and/or treatment outcomes.

Desmoplasia measured by computer assisted image analysis: an independent prognostic marker in colorectal carcinoma

AIMS

The assessment of desmoplasia by traditional semiquantitative methods does not provide reliable prognostic data. The aim of this study was to quantify desmoplasia by computerised image analysis in primary colorectal carcinomas and to investigate its ability to predict overall survival.

METHODS

In total, 112 colorectal adenocarcinomas, with a median follow up of 66 months, were studied. The representative tumour sections were stained by the van Gieson method, which stains collagen rich stroma red. For quantitative histochemical measurement, digital images were analysed by a computerised image analysis program to calculate the percentage of red stained tissue area. The percentage of desmoplasia (PD) was related to conventional clinicopathological prognostic factors and overall survival.

RESULTS

The mean (SD) PD was 4.85 (3.37). PD was found to be significantly associated with lymph vessel and venous invasion. By Kaplan-Meier analysis, PD was associated with survival-patients with PD > 4 had a shorter survival than those with PD

CONCLUSION

Desmoplasia measured by image analysis seems to be a significant prognostic indicator in patients with colorectal carcinoma and the improved method described in this study would be useful for routine prognostication.

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Key Words

• desmoplasia
• colorectal carcinoma
• prognosis
• quantitative histochemistry
• image analysis

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MESH Headings

• Adenocarcinoma/pathology
• Adenocarcinoma/secondary
• Adult
• Aged
• Aged, 80 and over
• Blood Vessels/pathology
• Colorectal Neoplasms/pathology
• Fibrosis
• Follow-Up Studies
• Humans
• Image Processing, Computer-Assisted/methods
• Lymphatic Vessels/pathology
• Middle Aged
• Neoplasm Invasiveness
• Neoplasm Staging
• Prognosis
• Reproducibility of Results
• Survival Analysis

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Affiliation(s)

B Sis Department of Pathology, Dokuz Eylül University School of Medicine, Inciralti, Izmir 35340, Turkey
S Sarioglu
S Sokmen
M Sakar
A Kupelioglu
M Fuzun

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