Comparison of hypoxia transcriptome in vitro with in vivo gene expression in human bladder cancer

Understanding metabolic alterations and heterogeneity in cancer progression through validated immunodetection of key molecular components: a case of carbonic anhydrase IX

Cancer metabolic heterogeneity develops in response to both intrinsic factors (mutations leading to activation of oncogenic pathways) and extrinsic factors (physiological and molecular signals from the extracellular milieu). Here we review causes and consequences of metabolic alterations in cancer cells with focus on hypoxia and acidosis, and with particular attention to carbonic anhydrase IX (CA IX). CA IX is a cancer-associated enzyme induced and activated by hypoxia in a broad range of tumor types, where it participates in pH regulation as well as in molecular mechanisms supporting cancer cells’ invasion and metastasis. CA IX catalyzes reversible conversion of carbon dioxide to bicarbonate ion plus proton and cooperates with a spectrum of molecules transporting ions or metabolites across the plasma membrane. Thereby CA IX contributes to extracellular acidosis as well as to buffering intracellular pH, which is essential for cell survival, metabolic performance, and proliferation of cancer cells. Since CA IX expression pattern reflects gradients of oxygen, pH, and other intratumoral factors, we use it as a paradigm to discuss an impact of antibody quality and research material on investigating metabolic reprogramming of tumor tissue. Based on the validation, we propose the most reliable CA IX-specific antibodies and suggest conditions for faithful immunohistochemical analysis of molecules contributing to heterogeneity in cancer progression.

Level of Murine DDX3 RNA Helicase Determines Phenotype Changes of Hepatocytes In Vitro and In Vivo

DDX3 RNA helicase is intensively studied as a therapeutic target due to participation in the replication of some viruses and involvement in cancer progression. Here we used transcriptome analysis to estimate the primary response of hepatocytes to different levels of RNAi-mediated knockdown of DDX3 RNA helicase both in vitro and in vivo. We found that a strong reduction of DDX3 protein (>85%) led to similar changes in vitro and in vivo—deregulation of the cell cycle and Wnt and cadherin pathways. Also, we observed the appearance of dead hepatocytes in the healthy liver and a decrease of cell viability in vitro after prolonged treatment. However, more modest downregulation of the DDX3 protein (60–65%) showed discordant results in vitro and in vivo—similar changes in vitro as in the case of strong knockdown and a different phenotype in vivo. These results demonstrate that the level of DDX3 protein can dramatically influence the cell phenotype in vivo and the decrease of DDX3, for more than 85% leads to cell death in normal tissues, which should be taken into account during the drug development of DDX3 inhibitors.

Development of Novel 18F-PET Agents for Tumor Hypoxia Imaging

Tumor hypoxia is a major factor responsible for tumor progression, metastasis, invasion, and treatment resistance, leading to low local tumor control and recurrence after radiotherapy in cancers. Here,¹⁸F-positron emission tomography (PET) probes are developed for visualizing viable hypoxic cells in biopsies. Pimonidazole derivatives and nitroimidazole-based agents bearing sulfonyl linkers were evaluated. A small-animal PET study showed that the tumor uptake of [¹⁸F]-23 [poly(ethylene glycols) (PEG)-sulfonyl linker] of 3.36 ± 0.29%ID/g was significantly higher (P < 0.01) than that of [¹⁸F]-20 (piperazine-linker tracer, 2.55 ± 0.49%ID/g) at 2 h postinjection in UPPL tumors. The tumor-to-muscle uptake ratio of [¹⁸F]-23 (2.46 ± 0.48 at 2 h pi) was well improved compared with that of [¹⁸F]-FMISO (1.25 ± 0.14 at 2 h pi). A comparable distribution pattern was observed between ex vivo autoradiography of [¹⁸F]-23 and pimonidazole staining of the neighboring slice, indicating that [¹⁸F]-23 is a promising PET agent for hypoxia imaging.

Impairment of carbonic anhydrase IX ectodomain cleavage reinforces tumorigenic and metastatic phenotype of cancer cells

BACKGROUND

Carbonic anhydrase IX (CA IX) is a hypoxia-induced enzyme regulating tumour pH and facilitating cell migration/invasion. It is primarily expressed as a transmembrane cell-surface protein, but its ectodomain can be shed by ADAM17 to extracellular space. This study aims to elucidate the impact of CA IX shedding on cancer cells.

METHODS

We generated a non-shed CA IX mutant by deletion of amino acids 393-402 from the stalk region and studied its phenotypic effects compared to full-length, shedding-competent CA IX using a range of assays based on immunodetection, confocal microscopy, in vitro real-time cell monitoring and in vivo tumour cell inoculation using xenografted NMRI and C57BL/6J female mice.

RESULTS

We demonstrated that the impairment of shedding does not alter the ability of CA IX to bind ADAM17, internalise, form oligomers and regulate pH, but induces cancer-promoting changes in extracellular proteome. Moreover, it affects intrinsic properties of cells expressing the non-shed variant, in terms of their increased ability to migrate, generate primary tumours and form metastatic lesions in lungs.

CONCLUSIONS

Our results show that the ectodomain shedding controls pro-tumorigenic and pro-metastatic roles of the cell-associated CA IX and suggest that this phenomenon should be considered when developing CA IX-targeted therapeutic strategies.

Technical Feasibility and Physiological Relevance of Hypoxic Cell Culture Models

Hypoxia is characterized as insufficient oxygen delivery to tissues and cells in the body and is prevalent in many human physiology processes and diseases. Thus, it is an attractive state to experimentally study to understand its inner mechanisms as well as to develop and test therapies against pathological conditions related to hypoxia. Animal models in vivo fail to recapitulate some of the key hallmarks of human physiology, which leads to human cell cultures; however, they are prone to bias, namely when pericellular oxygen concentration (partial pressure) does not respect oxygen dynamics in vivo. A search of the current literature on the topic revealed this was the case for many original studies pertaining to experimental models of hypoxia in vitro. Therefore, in this review, we present evidence mandating for the close control of oxygen levels in cell culture models of hypoxia. First, we discuss the basic physical laws required for understanding the oxygen dynamics in vitro, most notably the limited diffusion through a liquid medium that hampers the oxygenation of cells in conventional cultures. We then summarize up-to-date knowledge of techniques that help standardize the culture environment in a replicable fashion by increasing oxygen delivery to the cells and measuring pericellular levels. We also discuss how these tools may be applied to model both constant and intermittent hypoxia in a physiologically relevant manner, considering known values of partial pressure of tissue normoxia and hypoxia in vivo, compared to conventional cultures incubated at rigid oxygen pressure. Attention is given to the potential influence of three-dimensional tissue cultures and hypercapnia management on these models. Finally, we discuss the implications of these concepts for cell cultures, which try to emulate tissue normoxia, and conclude that the maintenance of precise oxygen levels is important in any cell culture setting.

Hypoxia-induced RelA/p65 derepresses SLC16A3 (MCT4) by downregulating ZBTB7A

Overexpressed Solute Carrier Family 16 Member 3 (SLC16A3, also called MCT4) plays a critical role in hypoxic cancer cell growth and proliferation, by expelling glycolysis-derived lactate across the plasma membrane. However, how SLC16A3 expression is regulated, under hypoxic conditions, is poorly understood. FBI-1, encoded by ZBTB7A, is a proto-oncoprotein. Interestingly, under hypoxic conditions, expression of SLC16A3, and hypoxia-inducible factor-1 (HIF-1), increased gradually, while FBI-1 expression decreased, suggesting a negative correlation between SLC16A3/HIF-1 and FBI-1 expression. Consequently, we hypothesized that FBI-1 might regulate SLC16A3 and/or HIF-1 expression. Transient transfection and transcription assays of SLC16A3 promoter reporter fusion constructs, oligonucleotide-pulldowns, and ChIP assays, showed that HIF-1α activates SLC16A3 by binding to a hypoxia-response element (HRE), while ectopic FBI-1 potently repressed SLC16A3, by binding to both FBI-1-response elements (FREs) and HREs, during hypoxia. Further evidence for this model was downregulation of ZBTB7A, correlated with SLC16A3 upregulation, in hypoxic colon cancer cells. We also investigated how FBI-1 expression is downregulated during hypoxia. The 5'-upstream regulatory region of ZBTB7A contains two NF-κB-binding sites and two HREs. Interestingly, hypoxia activated NF-κB (RelA/p65) and also increased its nuclear translocation. NF-κB repressed ZBTB7A by binding NF-κB-binding elements, and downregulated the repressor FBI-1, thereby increasing SLC16A3 transcription. While transcriptional repression of SLC16A3 by FBI-1 inhibited lactate efflux, repression of ZBTB7A and activation of lactate efflux by NF-κB, increased colon cancer cell growth and proliferation.

Ultrasound beam steering of oxygen nanobubbles for enhanced bladder cancer therapy

New intravesical treatment approaches for bladder cancer are needed as currently approved treatments show several side effects and high tumor recurrence rate. Our study used MB49 murine urothelial carcinoma model to evaluate oxygen encapsulated cellulosic nanobubbles as a novel agent for imaging and ultrasound guided drug delivery. In this study, we show that oxygen nanobubbles (ONB) can be propelled (up to 40 mm/s) and precisely guided in vivo to the tumor by an ultrasound beam. Nanobubble velocity can be controlled by altering the power of the ultrasound Doppler beam, while nanobubble direction can be adjusted to different desired angles by altering the angle of the beam. Precise ultrasound beam steering of oxygen nanobubbles was shown to enhance the efficacy of mitomycin-C, resulting in significantly lower tumor progression rates while using a 50% lower concentration of chemotherapeutic drug. Further, dark field imaging was utilized to visualize and quantify the ONB ex vivo. ONBs were found to localize up to 500 µm inside the tumor using beam steering. These results demonstrate the potential of an oxygen nanobubble drug encapsulated system to become a promising strategy for targeted drug delivery because of its multimodal (imaging and oxygen delivery) and multifunctional (targeting and hypoxia programming) properties.

Hypoxia-mediated upregulation of MCT1 expression supports the glycolytic phenotype of glioblastomas

Background

Glioblastomas (GBM) present a high cellular heterogeneity with conspicuous necrotic regions associated with hypoxia, which is related to tumor aggressiveness. GBM tumors exhibit high glycolytic metabolism with increased lactate production that is extruded to the tumor microenvironment through monocarboxylate transporters (MCTs). While hypoxia-mediated regulation of MCT4 has been characterized, the role of MCT1 is still controversial. Thus, we aimed to understand the role of hypoxia in the regulation of MCT expression and function in GBM, MCT1 in particular.

Methods

Expression of hypoxia- and glycolytic-related markers, as well as MCT1 and MCT4 isoforms was assessed in in vitro and in vivo orthotopic glioma models, and also in human GBM tissues by immunofluorescence/immunohistochemistry and Western blot. Following MCT1 inhibition, either pharmacologically with CHC (α-cyano-4-hydroxynnamic acid) or genetically with siRNAs, we assessed GBM cell viability, proliferation, metabolism, migration and invasion, under normoxia and hypoxia conditions.

Results

Hypoxia induced an increase in MCT1 plasma membrane expression in glioma cells, both in in vitro and in vivo models. Additionally, treatment with CHC and downregulation of MCT1 in glioma cells decreased lactate production, cell proliferation and invasion under hypoxia. Moreover, in the in vivo orthotopic model and in human GBM tissues, there was extensive co-expression of MCT1, but not MCT4, with the GBM hypoxia marker CAIX.

Conclusion

Hypoxia-induced MCT1 supports GBM glycolytic phenotype, being responsible for lactate efflux and an important mediator of cell survival and aggressiveness. Therefore, MCT1 constitutes a promising therapeutic target in GBM.

MCT4 as a potential therapeutic target for metastatic gastric cancer with peritoneal carcinomatosis

Monocarboxylate transporters (MCTs) play a major role in up-regulation of glycolysis and adaptation to acidosis. However, the role of MCTs in gastric cancer (GC) is not fully understood. We investigated the potential utilization of a new cancer therapy for GC. We characterized the expression patterns of the MCT isoforms 1, 2, and 4 and investigated the role of MCT in GC through in vitro and in vivo tests using siRNA targeting MCTs. In GC cell lines, MCT1, 2, and 4 were up-regulated with different expression levels; MCT1 and MCT4 were more widely expressed in GC cell lines compared with MCT2. Inhibition of MCTs by siRNA or AR-C155858 reduced cell viability and lactate uptake in GC cell lines. The effect of inhibition of MCTs on tumor growth was also confirmed in xenograft models. Furthermore, MCT inhibition in GC cells increased the sensitivity of cells to radiotherapy or chemotherapy. Compared with normal gastric tissue, no significant alterations of expression levels in tumors were identified for MCT1 and MCT2, whereas a significant increase in MCT4 expression was observed. Most importantly, MCT4 was highly overexpressed in malignant cells of acsites and its silencing resulted in reduced tumor cell proliferation and lactate uptake in malignant ascites. Our study suggests that MCT4 is a clinically relevant target in GC with peritoneal carcinomatosis.

Enhanced glycolysis, regulated by HIF-1α via MCT-4, promotes inflammation in arsenite-induced carcinogenesis

Arsenite is well established as a human carcinogen, but the molecular mechanisms leading to arsenite-induced carcinogenesis are complex and elusive. Accelerated glycolysis, a common process in tumor cells called the Warburg effect, is associated with various biological phenomena. However, the role of glycolysis induced by arsenite is unknown. We have found that, with chronic exposure to arsenite, L-02 cells undergo a metabolic shift to glycolysis. In liver cells exposed to arsenite, hypoxia inducible factor-1α (HIF-1α) and monocarboxylate transporter-4 (MCT-4) are over-expressed. MCT-4, directly mediated by HIF-1α, maintains a high level of glycolysis, and the enhanced glycolysis promotes pro-inflammatory properties, which are involved in arsenite carcinogenesis. In addition, serum lactate and cytokines are higher in arsenite-exposed human populations, and there is a positive correlation between them. Moreover, there is a positive relationship between lactate and cytokines with arsenic in hair. In sum, these findings indicate that MCT-4, mediated by HIF-1α, enhances the glycolysis induced by arsenite. Lactate, the end product of glycolysis, is released into the extracellular environment. The acidic microenvironment promotes production of pro-inflammatory cytokines, which contribute to arsenite-induced liver carcinogenesis. These results provide a link between the induction of glycolysis and inflammation in liver cells exposed to arsenite, and thus establish a previously unknown mechanism for arsenite-induced hepatotoxicity.

High expression of insulin receptor on tumour-associated blood vessels in invasive bladder cancer predicts poor overall and progression-free survival

Bladder cancer is a frequently recurring disease with a very poor prognosis once progressed to invasive stages, and tumour-associated blood vessels play a crucial role in this process. In order to identify novel biomarkers associated with progression, we isolated blood vascular endothelial cells (BECs) from human invasive bladder cancers and matched normal bladder tissue, and found that tumour-associated BECs greatly up-regulated the expression of insulin receptor (INSR). High expression of INSR on BECs of invasive bladder cancers was significantly associated with shorter progression-free and overall survival. Furthermore, increased expression of the INSR ligand IGF-2 in invasive bladder cancers was associated with reduced overall survival. INSR may therefore represent a novel biomarker to predict cancer progression. Mechanistically, we observed pronounced hypoxia in human bladder cancer tissue, and found a positive correlation between the expression of the hypoxia marker gene GLUT1 and vascular INSR expression, indicating that hypoxia drives INSR expression in tumour-associated blood vessels. In line with this, exposure of cultured BECs and human bladder cancer cell lines to hypoxia led to increased expression of INSR and IGF-2, respectively, and IGF-2 increased BEC migration through the activation of INSR in vitro. Taken together, we identified vascular INSR expression as a potential biomarker for progression in bladder cancer. Furthermore, our data suggest that IGF-2/INSR mediated paracrine crosstalk between bladder cancer cells and endothelial cells is functionally involved in tumour angiogenesis and may thus represent a new therapeutic target. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Prolonged hypoxia induces monocarboxylate transporter-4 expression in mesenchymal stem cells resulting in a secretome that is deleterious to cardiovascular repair

MSCs encounter extended hypoxia in the wound microenvironment yet little is known about their adaptability to this prolonged hypoxic milieu. In this study, we evaluated the cellular and molecular response of MSCs in extended hypoxia (1% O2 ) versus normoxia (20% O2 ) culture. Prolonged hypoxia induced a switch toward anaerobic glycolysis transcriptome and a dramatic increase in the transcript and protein levels of monocarboxylate transporter-4 (MCT4) in MSCs. To clarify the impact of MCT4 upregulation on MSC biology, we generated MSCs which stably overexpressed MCT4 (MCT4-MSCs) at levels similar to wild-type MSCs following prolonged hypoxic culture. Consistent with its role to efflux lactate to maintain intracellular pH, MCT4-MSCs demonstrated reduced intracellular lactate. To explore the in vivo significance of MCT4 upregulation in MSC therapy, mice were injected intramuscularly following MI with control (GFP)-MSCs, MCT4-MSCs, or MSCs in which MCT4 expression was stably silenced (KDMCT4-MSCs). Overexpression of MCT4 worsened cardiac remodeling and cardiac function whereas silencing of MCT4 significantly improved cardiac function. MCT4-overexpressing MSC secretome induced reactive oxygen species-mediated cardiomyocyte but not fibroblast apoptosis in vitro and in vivo; lactate alone recapitulated the effects of the MCT4-MSC secretome. Our findings suggest that lactate extruded by MCT4-overexpressing MSCs preferentially induced cell death in cardiomyocytes but not in fibroblasts, leading ultimately to a decline in cardiac function and increased scar size. A better understanding of stem cells response to prolonged hypoxic stress and the resultant stem cell-myocyte/fibroblast cross-talk is necessary to optimize MSC-based therapy for cardiac regeneration.

Increased S100A4 expression in the vasculature of human COPD lungs and murine model of smoke-induced emphysema

Background

Chronic obstructive lung disease (COPD) is a common cause of death in industrialized countries often induced by exposure to tobacco smoke. A substantial number of patients with COPD also suffer from pulmonary hypertension that may be caused by hypoxia or other hypoxia-independent stimuli - inducing pulmonary vascular remodeling. The Ca²⁺ binding protein, S100A4 is known to play a role in non-COPD-driven vascular remodeling of intrapulmonary arteries. Therefore, we have investigated the potential involvement of S100A4 in COPD induced vascular remodeling.

Methods

Lung tissue was obtained from explanted lungs of five COPD patients and five non-transplanted donor lungs. Additionally, mice lungs of a tobacco-smoke-induced lung emphysema model (exposure for 3 and 8 month) and controls were investigated. Real-time RT-PCR analysis of S100A4 and RAGE mRNA was performed from laser-microdissected intrapulmonary arteries. S100A4 immunohistochemistry was semi-quantitatively evaluated. Mobility shift assay and siRNA knock-down were used to prove hypoxia responsive elements (HRE) and HIF binding within the S100A4 promoter.

Results

Laser-microdissection in combination with real-time PCR analysis revealed higher expression of S100A4 mRNA in intrapulmonary arteries of COPD patients compared to donors. These findings were mirrored by semi-quantitative analysis of S100A4 immunostaining. Analogous to human lungs, in mice with tobacco-smoke-induced emphysema an up-regulation of S100A4 mRNA and protein was observed in intrapulmonary arteries. Putative HREs could be identified in the promoter region of the human S100A4 gene and their functionality was confirmed by mobility shift assay. Knock-down of HIF1/2 by siRNA attenuated hypoxia-dependent increase in S100A4 mRNA levels in human primary pulmonary artery smooth muscle cells. Interestingly, RAGE mRNA expression was enhanced in pulmonary arteries of tobacco-smoke exposed mice but not in pulmonary arteries of COPD patients.

Conclusions

As enhanced S100A4 expression was observed in remodeled intrapulmonary arteries of COPD patients, targeting S100A4 could serve as potential therapeutic option for prevention of vascular remodeling in COPD patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-015-0284-5) contains supplementary material, which is available to authorized users.

Organized metabolic crime in prostate cancer: The coexpression of MCT1 in tumor and MCT4 in stroma is an independent prognosticator for biochemical failure

BACKGROUND

Lactate import or export over cell membranes is facilitated by monocarboxylate transporters (MCTs) 1 and 4. Expression profiles can be markers of an oxidative or glycolytic phenotype. Descriptive studies and functional studies in neoplastic cells and fibroblasts in prostate cancer (PC) have suggested a distinct phenotype. We aimed to explore expression of MCT1 and MCT4 in PC cells and surrounding stroma in a large cohort. Additionally, we wanted to find out if distinct expression profiles were associated with biochemical failure-free survival (BFFS).

METHODS

Tissue microarrays were constructed from 535 patients with radical prostatectomies between January 1, 1995, and December 31, 2005. Immunohistochemistry was used to detect expression, and degrees of expression were evaluated semiquantitatively by 2 pathologists using light microscopy.

RESULTS

For MCT1, there was only epithelial expression, whereas there was a low level of expression of MCT4 in tumor and stroma. A total of 172 patients had a low expression of MCT1 in tumor and MCT4 in stroma. There were 232 patients who had a high expression of MCT1 and a low expression of MCT4 in stroma. Only 11 patients had a low tumoral MCT1 expression and a high stromal MCT4 expression, and 26 patients (5%) had a high expression of both. Patients with a high-high combination had a significantly reduced BFFS (P = 0.011), and when adjusting for other factors, its effect was significant and independent (HR = 1.99, CI 95%: 1.09-3.62; P = 0.024).

CONCLUSIONS

This study adds to the current understanding of the reversed Warburg effect to be a significant phenotype in PC. High coexpression of MCT1 in tumor and MCT4 in stroma is independently associated to a worse BFFS, and the strength of this association is as strong as having a Gleason score of ≥9.

Exploring the miRNA-mRNA regulatory network in clear cell renal cell carcinomas by next-generation sequencing expression profiles

Altered microRNA (miRNA) expression is a hallmark of many cancer types. The combined analysis of miRNA and messenger RNA (mRNA) expression profiles is crucial to identifying links between deregulated miRNAs and oncogenic pathways. Therefore, we investigated the small non-coding (snc) transcriptomes of nine clear cell renal cell carcinomas (ccRCCs) and adjacent normal tissues for alterations in miRNA expression using a publicly available small RNA-Sequencing (sRNA-Seq) raw-dataset. We constructed a network of deregulated miRNAs and a set of differentially expressed genes publicly available from an independent study to in silico determine miRNAs that contribute to clear cell renal cell carcinogenesis. From a total of 1,672 sncRNAs, 61 were differentially expressed across all ccRCC tissue samples. Several with known implications in ccRCC development, like the upregulated miR-21-5p, miR-142-5p, as well as the downregulated miR-106a-5p, miR-135a-5p, or miR-206. Additionally, novel promising candidates like miR-3065, which i.a. targets NRP2 and FLT1, were detected in this study. Interaction network analysis revealed pivotal roles for miR-106a-5p, whose loss might contribute to the upregulation of 49 target mRNAs, miR-135a-5p (32 targets), miR-206 (28 targets), miR-363-3p (22 targets), and miR-216b (13 targets). Among these targets are the angiogenesis, metastasis, and motility promoting oncogenes c-MET, VEGFA, NRP2, and FLT1, the latter two coding for VEGFA receptors.

Both butyrate incubation and hypoxia upregulate genes involved in the ruminal transport of SCFA and their metabolites

Butyrate modulates the differentiation, proliferation and gene expression profiles of various cell types. Ruminal epithelium is exposed to a high intraluminal concentration and inflow of n-butyrate. We aimed to investigate the influence of n-butyrate on the mRNA expression of proteins involved in the transmembranal transfer of n-butyrate metabolites and short-chain fatty acids in ruminal epithelium. N-butyrate-induced changes were compared with the effects of hypoxia because metabolite accumulation after O2 depletion is at least partly comparable to the accumulation of metabolites after n-butyrate exposure. Furthermore, in various tissues, O2 depletion modulates the expression of transport proteins that are also involved in the extrusion of metabolites derived from n-butyrate breakdown in ruminal epithelium. Sheep ruminal epithelia mounted in Ussing chambers were exposed to 50 mM n-butyrate or incubated under hypoxic conditions for 6 h. Electrophysiological measurements showed hypoxia-induced damage in the epithelia. The mRNA expression levels of monocarboxylate transporters (MCT) 1 and 4, anion exchanger (AE) 2, downregulated in adenoma (DRA), putative anion transporter (PAT) 1 and glucose transporter (GLUT) 1 were assessed by RT-qPCR. We also examined the mRNA expression of nuclear factor (NF) κB, cyclooxygenase (COX) 2, hypoxia-inducible factor (HIF) 1α and acyl-CoA oxidase (ACO) to elucidate the possible signalling pathways involved in the modulation of gene expression. The mRNA expression levels of MCT 1, MCT 4, GLUT 1, HIF 1α and COX 2 were upregulated after both n-butyrate exposure and hypoxia. ACO and PAT 1 were upregulated only after n-butyrate incubation. Upregulation of both MCT isoforms and NFκB after n-butyrate incubation could be detected on protein level as well. Our study suggests key roles for MCT 1 and 4 in the adaptation to an increased intracellular load of metabolites, whereas an involvement of PAT 1 in the transport of n-butyrate also seems possible.

Tumor-stroma metabolic relationship based on lactate shuttle can sustain prostate cancer progression

Background

Cancer cell adopts peculiar metabolic strategies aimed to sustain the continuous proliferation in an environment characterized by relevant fluctuations in oxygen and nutrient levels. Monocarboxylate transporters MCT1 and MCT4 can drive such adaptation permitting the transport across plasma membrane of different monocarboxylic acids involved in energy metabolism.

Methods

Role of MCTs in tumor-stroma metabolic relationship was investigated in vitro and in vivo using transformed prostate epithelial cells, carcinoma cell lines and normal fibroblasts. Moreover prostate tissues from carcinoma and benign hypertrophy cases were analyzed for individuating clinical-pathological implications of MCT1 and MCT4 expression.

Results

Transformed prostate epithelial (TPE) and prostate cancer (PCa) cells express both MCT1 and MCT4 and demonstrated variable dependence on aerobic glycolysis for maintaining their proliferative rate. In glucose-restriction the presence of L-lactate determined, after 24 h of treatment, in PCa cells the up-regulation of MCT1 and of cytochrome c oxidase subunit I (COX1), and reduced the activation of AMP-activated protein kinase respect to untreated cells. The blockade of MCT1 function, performed by si RNA silencing, determined an appreciable antiproliferative effect when L-lactate was utilized as energetic fuel. Accordingly L-lactate released by high glycolytic human diploid fibroblasts WI-38 sustained survival and growth of TPE and PCa cells in low glucose culture medium. In parallel, the treatment with conditioned medium from PCa cells was sufficient to induce glycolytic metabolism in WI-38 cells, with upregulation of HIF-1a and MCT4. Co-injection of PCa cells with high glycolytic WI-38 fibroblasts determined an impressive increase in tumor growth rate in a xenograft model that was abrogated by MCT1 silencing in PCa cells. The possible interplay based on L-lactate shuttle between tumor and stroma was confirmed also in human PCa tissue where we observed a positive correlation between stromal MCT4 and tumor MCT1 expression.

Conclusions

Our data demonstrated that PCa progression may benefit of MCT1 expression in tumor cells and of MCT4 in tumor-associated stromal cells. Therefore, MCTs may result promising therapeutic targets in different phases of neoplastic transformation according to a strategy aimed to contrast the energy metabolic adaptation of PCa cells to stressful environments.

Antenatal maternal long-term hypoxia: acclimatization responses with altered gene expression in ovine fetal carotid arteries

In humans and other species, long-term hypoxia (LTH) during pregnancy can lead to intrauterine growth restriction with reduced body/brain weight, dysregulation of cerebral blood flow (CBF), and other problems. To identify the signal transduction pathways and critical molecules, which may be involved in acclimatization to high altitude LTH, we conducted microarray with advanced bioinformatic analysis on carotid arteries (CA) from the normoxic near-term ovine fetus at sea-level and those acclimatized to high altitude for 110+ days during gestation. In response to LTH acclimatization, in fetal CA we identified mRNA from 38 genes upregulated >2 fold (P<0.05) and 9 genes downregulated >2-fold (P<0.05). The major genes with upregulated mRNA were SLC1A3, Insulin-like growth factor (IGF) binding protein 3, IGF type 2 receptor, transforming growth factor (TGF) Beta-3, and genes involved in the AKT and BCL2 signal transduction networks. Most genes with upregulated mRNA have a common motif for Pbx/Knotted homeobox in the promoter region, and Sox family binding sites in the 3′ un translated region (UTR). Genes with downregulated mRNA included those involved in the P53 pathway and 5-lipoxygenase activating proteins. The promoter region of all genes with downregulated mRNA, had a common 49 bp region with a binding site for DOT6 and TOD6, components of the RPD3 histone deacetylase complex RPD3C(L). We also identified miRNA complementary to a number of the altered genes. Thus, the present study identified molecules in the ovine fetus, which may play a role in the acclimatization response to high-altitude associated LTH.

HERV-K and LINE-1 DNA Methylation and Reexpression in Urothelial Carcinoma

Changes in DNA methylation frequently accompany cancer development. One prominent change is an apparently genome-wide decrease in methylcytosine that is often ascribed to DNA hypomethylation at retroelements comprising nearly half the genome. DNA hypomethylation may allow reactivation of retroelements, enabling retrotransposition, and causing gene expression disturbances favoring tumor development. However, neither the extent of hypomethylation nor of retroelement reactivation are precisely known. We therefore assessed DNA methylation and expression of three major classes of retroelements (LINE-1, HERV-K, and AluY) in human urinary bladder cancer tissues and cell lines by pyrosequencing and quantitative reverse transcription–polymerase chain reaction, respectively. We found substantial global LINE-1 DNA hypomethylation in bladder cancer going along with a shift toward full-length LINE-1 expression. Thus, pronounced differences in LINE-1 expression were observed, which may be promoted, among others, by LINE-1 hypomethylation. Significant DNA hypomethylation was found at the HERV-K_22q11.23 proviral long terminal repeat (LTR) in bladder cancer tissues but without reactivation of its expression. DNA methylation of HERVK17, essentially absent from normal urothelial cells, was elevated in cell lines from invasive bladder cancers. Accordingly, the faint expression of HERVK17 in normal urothelial cells disappeared in such cancer cell lines. Of 16 additional HERV-Ks, expression of 7 could be detected in the bladder, albeit generally at low levels. Unlike in prostate cancers, none of these showed significant expression changes in bladder cancer. In contrast, expression of the AluYb8 but not of the AluYa5 family was significantly increased in bladder cancer tissues. Collectively, our findings demonstrate a remarkable specificity of changes in expression and DNA methylation of retroelements in bladder cancer with a significantly different pattern from that in prostate cancer.

RNA interference targeting adrenomedullin induces apoptosis and reduces the growth of human bladder urothelial cell carcinoma

Adrenomedullin (ADM) is a potent, long-lasting angiogenic peptide that was originally isolated from human pheochromocytoma. ADM signaling is of particular significance in endothelial cell biology because the peptide protects cells from apoptosis, and ADM has been shown to be pro-tumorigenic in that it stimulates tumor cell growth and angiogenesis. ADM may be involved in micro-vessel proliferation and partially in the release of hypoxia in solid tumors, contributing to the proliferation of tumor cells as well as local tumor invasion and metastasis. However, the effect of hypoxia-induced ADM expression in bladder cancer remains unclear. Here, we found that the levels of ADM protein in tumor tissue from patients with bladder urothelial cell carcinoma were significantly increased compared to the adjacent non-tumor bladder tissues (p < 0.01). Under hypoxic conditions, the expression of ADM was significantly elevated in a time-dependent manner in human bladder cancer cell lines. Furthermore, the knockdown of ADM by shRNA in T24 cells showed obvious apoptosis compared to untransfected controls (p < 0.0001). In addition, the combination of cisplatin and ADM-shRNA significantly reduces the tumor growth in vivo compared to treatment with cisplatin (p = 0.0046) or ADM-shRNA alone (p < 0.0001). These data suggest that ADM plays an important role in promoting bladder cancer cell growth under hypoxia and that the inhibition of ADM may provide a target for bladder cancer therapy.

Hypoxia-induced endothelial CX3CL1 triggers lung smooth muscle cell phenotypic switching and proliferative expansion

Distal arterioles with limited smooth muscles help maintain the high blood flow and low pressure in the lung circulation. Chronic hypoxia induces lung distal vessel muscularization. However, the molecular events that trigger alveolar hypoxia-induced peripheral endothelium modulation of vessel wall smooth muscle cell (SMC) proliferation and filling of nonmuscular areas are unclear. Here, we investigated the role of CX3CL1/CX3CR1 system in endothelial-SMC cross talk in response to hypoxia. Human lung microvascular endothelial cells responded to alveolar oxygen deficiency by overproduction of the chemokine CX3CL1. The CX3CL1 receptor CX3CR1 is expressed by SMCs that are adjacent to the distal endothelium. Hypoxic release of endothelial CX3CL1 induced SMC phenotypic switching from the contractile to the proliferative state. Inhibition of CX3CR1 prevented CX3CL1 stimulation of SMC proliferation and monolayer expansion. Furthermore, CX3CR1 deficiency attenuated spiral muscle expansion, distal vessel muscularization, and pressure elevation in response to hypoxia. Our findings indicate that the capillary endothelium relies on the CX3CL1-CX3CR1 axis to sense alveolar hypoxia and promote peripheral vessel muscularization. These results have clinical significance in the development of novel therapeutics that target mechanisms of distal arterial remodeling associated with pulmonary hypertension induced by oxygen deficiency that is present in people living at high altitudes and patients with obstructive lung diseases.

New perspectives for in vitro risk assessment of multiwalled carbon nanotubes: application of coculture and bioinformatics

Nanotechnology is a rapidly expanding field with wide application for industrial and medical use; therefore, understanding the toxicity of engineered nanomaterials is critical for their commercialization. While short-term in vivo studies have been performed to understand the toxicity profile of various nanomaterials, there is a current effort to shift toxicological testing from in vivo observational models to predictive and high-throughput in vitro models. However, conventional monoculture results of nanoparticle exposure are often disparate and not predictive of in vivo toxic effects. A coculture system of multiple cell types allows for cross-talk between cells and better mimics the in vivo environment. This review proposes that advanced coculture models, combined with integrated analysis of genome-wide in vivo and in vitro toxicogenomic data, may lead to development of predictive multigene expression-based models to better determine toxicity profiles of nanomaterials and consequent potential human health risk due to exposure to these compounds.

Prognostic significance of monocarboxylate transporter 4 expression in patients with colorectal cancer

Cancer cells generally have a high rate of glycolysis and produce larger quantities of lactate as compared to the surrounding normal cells. Monocarboxylate transporter 4 (MCT4) is one of the proton pumps exchanging the lactate through the plasma membrane. The prognostic significance of MCT4 expression has not been evaluated in patients with colorectal cancer (CRC). Surgical specimens from 105 CRC patients were immunohistochemically stained using a polyclonal anti-MCT4 antibody. The relationships among the MCT4 expression, clinicopathological factors and prognosis were evaluated. A total of 53 (50.5%) of the 105 patients with CRC were determined to have tumors positive for MCT4 expression. The expression of MCT4 significantly correlated with the tumor size, depth of invasion, lymph node metastasis, distant metastasis and TNM staging. The survival rate of the patients who were positive for MCT4 expression was significantly lower than that of patients with negative MCT4 expression. Positive MCT4 expression was a significantly poor prognostic factor, as determined by both univariate and multivariate analyses. Therefore, positive MCT4 expression appears to be a useful marker for tumor progression and prognosis in patients with CRC.

The spatial organization of proton and lactate transport in a rat brain tumor

Tumors create a heterogeneous acidic microenvironment which assists their growth and which must be taken into account in the design of drugs and their delivery. In addition, the acidic extracellular pH (pHe) is itself exploited in several experimental techniques for drug delivery. The way the acidity is created is not clear. We report here the spatial organization of key proton-handling proteins in C6 gliomas in rat brain. The mean profiles across the tumor rim of the Na⁺/H⁺ exchanger NHE1, and the lactate-H⁺ cotransporter MCT1, both showed peaks. NHE1, which is important for extension and migration of cells in vitro, showed a peak 1.55 times higher than in extratumoural tissue at 0.33 mm from the edge. MCT1 had a broader peak, further into the tumor (maximum 1.76 fold at 1.0 mm from the edge). In contrast, MCT4 and the carbonic anhydrase CAIX, which are associated with hypoxia, were not significantly upregulated in the rim. The spatial distribution of MCT4 was highly correlated with that of CAIX, suggesting that their expression is regulated by the same factors. Since protons extruded by NHE1 diffuse away through extracellular clefts, NHE1 requires a continuous source of intracellular protons. From the stoichiometries of metabolic pathways that produce or consume H⁺, and the greater availability of glucose compared to oxygen in most parts of a tumor, we support the classic view that most of the net proton efflux from C6 gliomas originates in glycolytic formation of lactate and H⁺ inside the tumor, but add that some lactate is taken up into cells in the rim on MCT1, and some lactate diffuses away, leaving its associated protons available to re-enter cells for extrusion on NHE1. Therapeutic inhibition of NHE1, MCT1 or CAIX is predicted to affect different parts of a tumor.

In vivo profiling of hypoxic gene expression in gliomas using the hypoxia marker EF5 and laser-capture microdissection

Hypoxia is a key determinant of tumor aggressiveness, yet little is known regarding hypoxic global gene regulation in vivo. We used the hypoxia marker EF5 coupled with laser-capture microdissection to isolate RNA from viable hypoxic and normoxic regions of 9L experimental gliomas. Through microarray analysis, we identified several mRNAs (including the HIF targets Vegf, Glut-1, and Hsp27) with increased levels under hypoxia compared with normoxia both in vitro and in vivo. However, we also found striking differences between the global in vitro and in vivo hypoxic mRNA profiles. Intriguingly, the mRNA levels of a substantial number of immunomodulatory and DNA repair proteins including CXCL9, CD3D, and RAD51 were found to be downregulated in hypoxic areas in vivo, consistent with a protumorigenic role of hypoxia in solid tumors. Immunohistochemical staining verified increased HSP27 and decreased RAD51 protein levels in hypoxic versus normoxic tumor regions. Moreover, CD8(+) T cells, which are recruited to tumors upon stimulation by CXCL9 and CXCL10, were largely excluded from viable hypoxic areas in vivo. This is the first study to analyze the influence of hypoxia on mRNA levels in vivo and can be readily adapted to obtain a comprehensive picture of hypoxic regulation of gene expression and its influence on biological functions in solid tumors.

Genomic alterations of primary tumor and blood in invasive ductal carcinoma of breast

BACKGROUND

Genomic alterations are important events in the origin and progression of various cancers, with DNA copy number changes associated with progression and treatment response in cancer. Array CGH is potentially useful in the identification of genomic alterations from primary tumor and blood in breast cancer patients. The aim of our study was to compare differences of DNA copy number changes in blood and tumor tissue in breast cancer.

METHODS

DNA copy number changes in blood were compared to those in tumor tissue using array-comparative genomic hybridization in samples obtained from 30 breast cancer patients. The relative degree of chromosomal changes was analyzed using log2 ratios and data was validated by real-time polymerase chain reaction.

RESULTS

Forty-six regions of gains present in more than 30% of the tissues and 70 regions of gains present in more than 30% of blood were identified. The most frequently gained region was chromosome 8q24. In total, agreement of DNA copy numbers between primary tumor and blood was minimal (Kappa = 0.138, p < 0.001).

CONCLUSION

Although there was only a slight agreement of DNA copy number alterations between the primary tumor and the blood samples, the blood cell copy number variation may have some clinical significance as compared to the primary tumor in IDC breast cancer patients.

Identification of novel keloid biomarkers through profiling of tissue biopsies versus cell cultures in keloid margin specimens compared to adjacent normal skin

OBJECTIVE

Keloid disease (KD) is a benign fibroproliferative skin tumor that results from abnormal wound healing and has no single definitive treatment. This study aims to identify KD biomarkers, which are cellular mediators that can serve as indicators of normal, pathological, and therapeutic processes.

METHODS

Bioinformatics analytic approaches, including comprehensive literature searches and DAVID Bioinformatics Resources 2008, were performed on the established KD linkage and previously reported microarray data to identify potential candidate genes for the study. Keloid margins and unaffected skin were obtained from KD patients (n = 4). RNA was extracted from the biopsies and second-passage culture equivalents. Reverse-transcriptase quantitative polymerase chain reactions were used to determine the gene expression levels. Student t tests were used to analyze the statistical significance in differential gene expressions.

RESULTS

Nineteen candidate genes were initially selected by bioinformatics analysis. Of the 19 genes, 10 were significantly (P < .05) upregulated in keloid margin biopsy specimens. The top-5 fold changes range from 10-fold to 175-fold, including aggrecan; asporin; inhibin, beta A; tumor necrosis factor-alpha inducible protein 6; and chromosome 5 open reading frame 13. There was no significant differential gene expression between the fibroblasts established using keloid margin or internal control sites.

CONCLUSIONS

The transcriptomic data generated from cultures did not consistently correlate to the biopsy equivalents. This study has demonstrated 10 genes that are significantly upregulated in biopsy samples of keloid margin, 5 of which have a fold change higher than 10-fold. Importantly these genes may serve as a potential biomarker for KD.

Carbonic anhydrase IX expression in prostate cancer

Tumour hypoxia is associated with over 70% of solid tumours including prostate and colorectal cancer. Hypoxia promotes tumour progression and resistance to treatment. Carbonic anhydrase IX (CA IX) is an endogenous marker of hypoxia. It is expressed in lung and renal cell carcinomas and is associated with a poor prognosis. CA IX has an important role in maintaining pH levels in the highly metabolically active cancer cell. The expression of CA IX in prostate cancer has not previously been investigated. Immunohistochemistry was used to examine CA IX expression in 59 patients, using tissue microarrays (TMAs) and full sections of BPH, surrounding stroma and prostate adenocarcinoma. Cores reviewed included 189 BPH, 130 Gleason grade 3, 93 Gleason grade 4, 40 Gleason grade 5. CA IX expression in colorectal cancer and HIF 1alpha in prostate cancer acted as positive controls. There was only occasional cell staining for CA IX expression. Although prostate cancer is a hypoxic tumour it does not express CA IX. This implies it relies on alternative pathways for maintaining pH balance in cancer. These studies would indicate that CA IX is not a suitable marker of hypoxia in prostate cancer.

Hypoxia stimulates lactate release and modulates monocarboxylate transporter (MCT1, MCT2, and MCT4) expression in human adipocytes

Hypoxia modulates white adipose tissue function, and this includes stimulating glucose uptake and the expression of facilitative glucose transporters (particularly GLUT1) in adipocytes. This study has examined the effect of hypoxia on lactate release from adipocytes and whether the monocarboxylate transporters that mediate lactate transport (MCTs1-4) are expressed in human adipocytes and are induced by low O(2) tension. Exposure of human Simpson-Golabi-Behmel syndrome adipocytes to 1% O(2) for 24 h resulted in increased lactate release (2.3-fold) compared with cells in normoxia (21% O(2)). Screening by reverse transcription polymerase chain reaction indicated that the genes encoding MCT1, MCT2, and MCT4 are expressed in human adipose tissue, and in adipocytes and preadipocytes in culture. Hypoxia (48 h) increased MCT1 (8.5-fold) and MCT4 (14.3-fold) messenger RNA (mRNA) levels in human adipocytes, but decreased MCT2 mRNA (fourfold). MCT1 protein level was also increased (2.7-fold at 48 h) by hypoxia, but there was no change in MCT4 protein. The changes in MCT gene expression induced by hypoxia were reversed on return to normoxia. Treatment with the hypoxia mimetic CoCl(2) resulted in up-regulation of MCT1 (up to twofold) and MCT4 (fivefold) mRNA level, but there was no significant effect on MCT2 expression. It is concluded that hypoxia increases lactate release from adipocytes and modulates MCT expression in a type-specific manner, with MCT1 and MCT4 expression being hypoxia-inducible transcription factor-1 (HIF-1) dependent. Increased lactate production and monocarboxylate transporter expression are likely to be key components of the adaptive response of adipocytes to low O(2) tension as adipose tissue mass expands in obesity.

The transcription factor Egr1 regulates the HIF-1alpha gene during hypoxia

Using oligonucleotide expression microarrays we have examined the modulation of gene expression in the DU145 prostate cancer cell line. Our findings confirm that the Egr1 transcription factor is rapidly and transiently upregulated by hypoxia. Furthermore, we have demonstrated that HIF-1alpha mRNA is also transiently upregulated, as is its target gene VEGF. To elucidate the mechanism of the transcriptional upregulation of the HIF-1alpha gene, we have shown that Egr1 is able to directly bind to the HIF-1alpha promoter using chromatin immunoprecipitation. We also provide evidence that the binding of Egr1 is necessary for the trans-activation of the HIF-1alpha promoter. These studies highlight the importance for the Egr1 transcription factor in the hypoxic response in cultured prostate cancer cell lines, and indicate that the response of Egr1 is upstream of HIF-1 in these cells. These studies are the first demonstration that the HIF-1alpha transcription factor is targeted directly by Egr1 in hypoxia.

Generation of an epigenetic signature by chronic hypoxia in prostate cells

Increasing levels of tissue hypoxia have been reported as a natural feature of the aging prostate gland and may be a risk factor for the development of prostate cancer. In this study, we have used PwR-1E benign prostate epithelial cells and an equivalently aged hypoxia-adapted PwR-1E sub-line to identify phenotypic and epigenetic consequences of chronic hypoxia in prostate cells. We have identified a significantly altered cellular phenotype in response to chronic hypoxia as characterized by increased receptor-mediated apoptotic resistance, the induction of cellular senescence, increased invasion and the increased secretion of IL-1 beta, IL6, IL8 and TNFalpha cytokines. In association with these phenotypic changes and the absence of HIF-1 alpha protein expression, we have demonstrated significant increases in global levels of DNA methylation and H3K9 histone acetylation in these cells, concomitant with the increased expression of DNA methyltransferase DMNT3b and gene-specific changes in DNA methylation at key imprinting loci. In conclusion, we have demonstrated a genome-wide adjustment of DNA methylation and histone acetylation under chronic hypoxic conditions in the prostate. These epigenetic signatures may represent an additional mechanism to promote and maintain a hypoxic-adapted cellular phenotype with a potential role in tumour development.

Identification of biomarkers in Dupuytren's disease by comparative analysis of fibroblasts versus tissue biopsies in disease-specific phenotypes

PURPOSE

Biomarkers are molecular mediators that can serve as indicators of normal biological processes, pathologic processes, and therapeutic interventions. This study aims to identify potential biomarkers in Dupuytren's disease (DD), a fibroproliferative benign tumor with an unknown etiology and high recurrence after surgery.

METHODS

Bioinformatic analytical techniques were employed to identify candidate genes that may be differentially expressed in DD, which included gene expression analysis of microarray data and thorough literature searches in genetic linkage and other related biomolecular studies. All DD cases were males with advanced DD (n = 5, 66 years +/- 14). RNA was extracted from biopsies and corresponding cultures of normal fascia (unaffected transverse palmar fascia), palmar nodule and cord from each patient. Real-time reverse transcription-polymerase chain reactions were performed to determine the gene expression levels for disease-related transcripts.

RESULTS

The bioinformatic analysis revealed 25 candidate genes, which were further short-listed to 6 genes via functional annotation. The 6 selected candidate genes included: A disintegrin and metalloproteinase domain (ADAM12), aldehyde dehydrogenase 1 family member (ALDH1) A1, Iroquois homeobox protein 6 (IRX6), proteoglycan 4 (PRG4), tenascin C (TNC), and periostin (POSTN). The culturing treatments were shown to have significant impact on the gene expression for ALDH1A1, PRG4, and TNC. In tissue biopsies, significant fold changes were observed for ADAM12, POSTN, and TNC in the cord and/or nodule when compared with that of normal fascia. ADAM12 and POSTN are associated with accelerated or abnormal cell growth, whereas TNC has been associated with fibrotic diseases and cell migration.

CONCLUSIONS

This study demonstrated differential gene expression results in DD tissue biopsies compared with that of their corresponding cultures. ADAM12, POSTN, and TNC were identified from the cord and nodule biopsy samples as potential biomarkers in relation to DD development.

The SLC16 monocaboxylate transporter family

1. The monocarboxylate transporter (MCT, SLC16) family comprises 14 members, of which to date only MCT1-4 have been shown to carry monocarboxylates, transporting important metabolic compounds such as lactate, pyruvate and ketone bodies in a proton-coupled manner. The transport of such compounds is fundamental for metabolism, and the tissue locations, properties and regulation of these isoforms is discussed. 2. Of the other members of the MCT family, MCT8 (a thyroid hormone transporter) and TAT1 (an aromatic amino acid transporter) have been characterized more recently, and their physiological roles are reviewed herein. The endogenous substrates and functions of the remaining members of the MCT family await elucidation. 3. The MCT proteins have the typical twelve transmembrane-spanning domain (TMD) topology of membrane transporter proteins, and their structure-function relationship is discussed, especially in relation to the future impact of the single nucleotide polymorphism (SNP) databases and, given their ability to transport pharmacologically relevant compounds, the potential impact for pharmacogenomics.

Construction of a chromosome 17 transcriptome in serous ovarian cancer identifies differentially expressed genes

Cytogenetic, molecular genetic, and functional analyses have implicated chromosome 17 genes in epithelial ovarian cancer (EOC). To further characterize the contribution of chromosome 17 genes in EOC, the Affymetrix U133A GeneChip was used to perform transcriptome analyses of 15 primary cultures of normal ovarian surface epithelial (NOSE) cells and 17 malignant ovarian tumor (TOV) samples of the serous histopathologic subtype. A two-way comparative analysis of 776 known genes and expressed sequences identified 253 genes that exhibited at least a threefold difference in expression in at least one TOV sample compared to the mean of NOSE samples. Within this data set, 99 of the 253 (39.1%) genes exhibited similar patterns of expression across all tested samples, suggesting a high degree of concordance in the chromosome 17 transcriptome. This observation was supported by hierarchical clustering analysis that segregated the TOV and NOSE samples into two separate groups. There were 77 genes that were differentially expressed in at least 50% of the TOV samples. Five genes (AdoRA(2B)at 17p12, CCL2 at 17q12, ACLY at 17q21.2, WIPI1 at 17q24.2, and SLC16A3 at 17q25.3) were significantly (P < 5.13E-11) differentially expressed at least threefold in all serous TOV samples, and all five genes were underexpressed in these TOV samples as compared to the NOSE samples. Interestingly, several of these differentially expressed genes have been previously associated with response to hypoxia.

Regulation of tumor pH and the role of carbonic anhydrase 9

The high metabolic rate required for tumor growth often leads to hypoxia in poorly-perfused regions. Hypoxia activates a complex gene expression program, mediated by hypoxia inducible factor 1 (HIF1alpha). One of the consequences of HIF1alpha activation is up-regulation of glycolysis and hence the production of lactic acid. In addition to the lactic acid-output, intracellular titration of acid with bicarbonate and the engagement of the pentose phosphate shunt release CO(2) from cells. Expression of the enzyme carbonic anhydrase 9 on the tumor cell surface catalyses the extracellular trapping of acid by hydrating cell-generated CO(2) into [see text] and H(+). These mechanisms contribute towards an acidic extracellular milieu favoring tumor growth, invasion and development. The lactic acid released by tumor cells is further metabolized by the tumor stroma. Low extracellular pH may adversely affect the intracellular milieu, possibly triggering apoptosis. Therefore, primary and secondary active transporters operate in the tumor cell membrane to protect the cytosol from acidosis. We review mechanisms regulating tumor intracellular and extracellular pH, with a focus on carbonic anhydrase 9. We also review recent evidence that may suggest a role for CA9 in coordinating pH(i) among cells of large, unvascularized cell-clusters.

The VHL tumor suppressor inhibits expression of the IGF1R and its loss induces IGF1R upregulation in human clear cell renal carcinoma

Clear cell renal cell cancer (CC-RCC) is a highly chemoresistant tumor characterized by frequent inactivation of the von Hippel-Lindau (VHL) gene. The prognosis is reportedly worse in patients whose tumors express immunoreactive type I insulin-like growth factor receptor (IGF1R), a key mediator of tumor cell survival. We aimed to investigate how IGF1R expression is regulated, and found that IGF1R protein levels were unaffected by hypoxia, but were higher in CC-RCC cells harboring mutant inactive VHL than in isogenic cells expressing wild-type (WT) VHL. IGF1R mRNA and promoter activities were significantly lower in CC-RCC cells expressing WT VHL, consistent with a transcriptional effect. In Sp1-null Drosophila Schneider cells, IGF1R promoter activity was dependent on exogenous Sp1, and was suppressed by full-length VHL protein (pVHL) but only partially by truncated VHL lacking the Sp1-binding motif. pVHL also reduced the stability of IGF1R mRNA via sequestration of HuR protein. Finally, IGF1R mRNA levels were significantly higher in CC-RCC biopsies than benign kidney, confirming the clinical relevance of these findings. Thus, we have identified a new hypoxia-independent role for VHL in suppressing IGF1R transcription and mRNA stability. VHL inactivation leads to IGF1R upregulation, contributing to renal tumorigenesis and potentially also to chemoresistance.

Tumor-associated carbonic anhydrases and their clinical significance

Carbonic anhydrases (CAs) are physiologically important enzymes that catalyze a reversible conversion of carbon dioxide to bicarbonate and participate in ion transport and pH control. Two human isoenzymes, CA IX and CA XII, are overexpressed in cancer and contribute to tumor physiology. Particularly CA IX is confined to only few normal tissues but is ectopically induced in many tumor types mainly due to its strong transcriptional activation by hypoxia accomplished via HIF-1 transcription factor. Therefore, CA IX can serve as a surrogate marker of hypoxia and a prognostic indicator. CA IX appears implicated in cell adhesion and in balance of pH disturbances caused by tumor metabolism. Both tumor-related expression pattern and functional involvement in tumor progression make it a suitable target for anticancer treatment. Here we summarize a current knowledge on CA IX and CA XII, and discuss possibilities of their exploitation for cancer detection, diagnostics, and therapy.

Vascular endothelial growth factor stimulates embryonic urinary bladder development in organ culture

OBJECTIVES

To determine whether vascular endothelial growth factor A (VEGF) and its receptors are expressed during bladder development in mice when capillaries are forming, and whether exogenous VEGF might enhance the growth of endothelia and other types of bladder cells, using an embryonic organ-culture model.

MATERIALS AND METHODS

Whole bladders from wild-type mice, at embryonic day (E) 14, were grown in serum-free organ culture in an air/5% CO2 atmosphere; some cultures were supplemented with VEGF and/or with VEGF receptor 1/Fc chimera (VEGFR1/Fc), which blocks VEGF bioactivity. Organs were harvested after 6 days and the expression of VEGF and related molecules assessed using immunohistochemistry.

RESULTS

VEGF, VEGFR1 and VEGFR2 positive cells were immunodetected in E14 and E18 bladders. Exogenous VEGF increased whole-organ growth, as assessed by explant areas, total cell numbers, DNA and protein content; proliferation was enhanced, and apoptosis decreased, in urothelium and surrounding tissues. VEGF also increased the proportions of cells expressing endothelial (CD31) and smooth muscle (alpha smooth muscle actin) markers. VEGFR1/Fc blocked the growth-enhancing effects of exogenous VEGF.

CONCLUSIONS

In organ culture, exogenous VEGF not only stimulated embryonic bladder endothelial cells but also strikingly enhanced the growth of the whole organ. Whether the effects of VEGF on diverse bladder cell populations are direct or indirect requires further investigation. The finding that VEGF protein is present in embryonic bladders in vivo raises the possibility that it has similar actions during normal development. The results also illuminate the pathobiology of certain bladder diseases in which VEGF levels have been shown to be increased.

The plasma membrane lactate transporter MCT4, but not MCT1, is up-regulated by hypoxia through a HIF-1alpha-dependent mechanism

The monocarboxylate transporter MCT4 mediates lactic acid efflux from most tissues that are dependent on glycolysis for their ATP production. Here we demonstrate that expression of MCT4 mRNA and protein was increased >3-fold by a 48-h exposure to 1% O(2), whereas MCT1 expression was not increased. The effect was mimicked by CoCl(2) (50 microm), suggesting transcriptional regulation by hypoxia-inducible factor 1alpha (HIF-1alpha). The predicted promoters for human MCT1, MCT2, and MCT4 were cloned into the pGL3 vector and shown to be active (luciferase luminescence) under basal conditions. Only the MCT4 promoter was activated (>2-fold) by hypoxia. No response was found in cells lacking HIF-1alpha. Four potential hypoxia-response elements were identified, but deletion analysis implicated only two in the hypoxia response. These were just upstream from the transcription start site and also found in the mouse MCT4 promoter. Mutation of site 2 totally abolished the hypoxic response, whereas mutation of site 1 only reduced the response. Gel-shift analysis demonstrated that nuclear extracts of hypoxic but not normoxic HeLa cells contained two transcription factors that bound to DNA probes containing these hypoxia-response elements. The major shifted band was abolished by mutation of site 2, and supershift analysis confirmed that HIF-1alpha bound to this site. Binding of the second factor was abolished by mutation of site 1. We conclude that MCT4, like other glycolytic enzymes, is up-regulated by hypoxia through a HIF-1alpha-mediated mechanism. This adaptive response allows the increased lactic acid produced during hypoxia to be rapidly lost from the cell.

Gene expression profile of B 16(F10) murine melanoma cells exposed to hypoxic conditions in vitro

Hypoxia is an important feature of tumor microenvironment, exerting far-reaching effects on cells and contributing to cancer progression. Previous studies have established substantial differences in hypoxia response between various cell lines. Investigating this phenomenon in melanoma cells contributes to a better understanding of cell lineage-specific hypoxia response and could point out novel hypoxia-regulated genes. We investigated transcriptional activity of B 16(F10) murine melanoma cells cultured for 24 h under hypoxic (nominal 1% O2, 15 samples including controls) and hypoxia-mimicking conditions (cobalt chloride, 100 or 200 microM, 6 samples including controls). Gene expression profiles were analyzed using MG-U74Av2 oligonucleotide microarrays. Data analysis revealed 2541 probesets (FDR <5%) for 1% oxygen experiment and 364 probesets (FDR <5%) for cobalt chloride, which showed differences in expression levels. Analysis of hypoxia-regulated genes (true hypoxia, 1% O2) by stringent Family-Wise Error Rate estimation indicated 454 significantly changed transcripts (p < 0.05). The most upregulated genes were Lgals3, Selenbpl, Nppb (more than ten-fold increase). We observed significant differences in expression levels of genes regulating glycolysis (Pfkp, Hk2, Aldo3, Eno2), apoptosis (Bnip3, Bnip31, Cdknla), transcription (Bhlhb2, Sap30, Atf3, Mxil), angiogenesis (Vegfa, Adm, Anxa2, Ctgf), adhesion (Pkp2, Itga4, Mcam), migration (Cnn2, Tmsb4x), and other processes. Both true hypoxia and hypoxia mimicry induced HIF-1-regulated genes. However, unsupervised analysis (Singular Value Decomposition) revealed distinct differences in gene expression between these two experimental conditions. Contrary to hypoxia, cobalt chloride caused suppression of gene expression rather than stimulation, especially concerning transcripts related to proliferation, immune response, DNA repair, and melanin biosynthesis.