Identification of genes differentially induced by hypoxia in pancreatic cancer cells

The effect of HIF on metabolism and immunity

Cellular hypoxia occurs when the demand for sufficient molecular oxygen needed to produce the levels of ATP required to perform physiological functions exceeds the vascular supply, thereby leading to a state of oxygen depletion with the associated risk of bioenergetic crisis. To protect against the threat of hypoxia, eukaryotic cells have evolved the capacity to elicit oxygen-sensitive adaptive transcriptional responses driven primarily (although not exclusively) by the hypoxia-inducible factor (HIF) pathway. In addition to the canonical regulation of HIF by oxygen-dependent hydroxylases, multiple other input signals, including gasotransmitters, non-coding RNAs, histone modifiers and post-translational modifications, modulate the nature of the HIF response in discreet cell types and contexts. Activation of HIF induces various effector pathways that mitigate the effects of hypoxia, including metabolic reprogramming and the production of erythropoietin. Drugs that target the HIF pathway to induce erythropoietin production are now approved for the treatment of chronic kidney disease-related anaemia. However, HIF-dependent changes in cell metabolism also have profound implications for functional responses in innate and adaptive immune cells, and thereby heavily influence immunity and the inflammatory response. Preclinical studies indicate a potential use of HIF therapeutics to treat inflammatory diseases, such as inflammatory bowel disease. Understanding the links between HIF, cellular metabolism and immunity is key to unlocking the full therapeutic potential of drugs that target the HIF pathway.

Hypoxia-dependent changes in cellular metabolism have important implications for the effective functioning of multiple immune cell subtypes. This Review describes the inputs that shape the hypoxic response in individual cell types and contexts, and the implications of this response for cellular metabolism and associated alterations in immune cell function.

Hypoxia is a common feature of particular microenvironments and at sites of immunity and inflammation, resulting in increased activity of the hypoxia-inducible factor (HIF).

In addition to hypoxia, multiple inputs modulate the activity of the HIF pathway, allowing nuanced downstream responses in discreet cell types and contexts.

HIF-dependent changes in cellular metabolism mitigate the effects of hypoxia and ensure that energy needs are met under conditions in which oxidative phosphorylation is reduced.

HIF-dependent changes in metabolism also profoundly affect the phenotype and function of immune cells.

The immunometabolic effects of HIF have important implications for targeting the HIF pathway in inflammatory disease.

Histone chaperone FACT complex coordinates with HIF to mediate an expeditious transcription program to adapt to poorly oxygenated cancers

Cancer cells adapt to hypoxia through HIFs (hypoxia-inducible factors), which initiate the transcription of numerous genes for cancer cell survival in the hypoxia microenvironment. In this study, we find that the FACT (facilitates chromatin transcription) complex works cooperatively with HIFs to facilitate the expeditious expression of HIF targets for hypoxia adaptation. Knockout (KO) of the FACT complex abolishes HIF-mediated transcription by impeding transcription elongation in hypoxic cancer cells. Interestingly, the FACT complex is post-translationally regulated by PHD/VHL-mediated hydroxylation and proteasomal degradation, in similar fashion to HIF-1/2α. Metabolic tracing confirms that FACT KO suppresses glycolytic flux and impairs lactate extrusion, leading to intracellular acidification and apoptosis in cancer cells. Therapeutically, hepatic artery ligation and anti-angiogenic inhibitors adversely induce intratumoral hypoxia, while co-treatment with FACT inhibitor curaxin remarkably hinders the growth of hypoxic tumors. In summary, our findings suggest that the FACT complex is a critical component of hypoxia adaptation and a therapeutic target for hypoxic tumors.

A potential signaling axis between RON kinase receptor and hypoxia-inducible factor-1 alpha in pancreatic cancer

The Cancer Genome Atlas (TCGA) of a pancreatic cancer cohort identified high MST1R (RON tyrosine kinase receptor) expression correlated with poor prognosis in human pancreatic cancer. RON expression is null/minimal in normal pancreas but elevates from pan-in lesions through invasive carcinomas. We report using multiple approaches RON directly regulates HIF-1α, a critical driver of genes involved in cancer cell invasion and metastasis. RON and HIF-1α are highly co-expressed in the 101 human PDAC tumors analyzed and RON expression correlated with HIF-1α expression in a subset of PDAC cell lines. knockdown of RON expression in RON positive cells blocked HIF-1α expression, whereas ectopic RON expression in RON null cells induced HIF-1α expression suggesting the direct regulation of HIF-1α by RON kinase receptor. RON regulates HIF-1α through an unreported transcriptional mechanism involving PI3 kinase-mediated AKT phosphorylation and Sp1-dependent HIF-1α promoter activity leading to increased HIF-1α mRNA expression. RON/HIF-1α modulation altered the invasive behavior of PDAC cells. A small-molecule RON kinase inhibitor decreased RON ligand, MSP-induced HIF-1α expression, and invasion of PDAC cells. Immunohistochemical analysis on RON knockdown orthotopic PDAC tumor xenograft confirmed that RON inhibition significantly blocked HIF-1α expression. RON/HIF-1α co-expression also exists in triple-negative breast cancer cells, a tumor type that also lacks molecular therapeutic targets. This is the first report describing RON/HIF-1α axis in any tumor type and is a potential novel therapeutic target.

Role of different immune cells and metabolic pathways in modulating the immune response in pancreatic cancer (Review)

Pancreatic cancer is an aggressive cancer, making it a leading cause of cancer‑related deaths. It is characteristically resistant to treatment, which results in low survival rates. In pancreatic cancer, immune cells undergo transitions that can inhibit or promote their functions, enabling treatment resistance and tumor progression. These transitions can be fostered by metabolic pathways that are dysregulated during tumorigenesis. The present review aimed to summarize the different immune cells and their roles in pancreatic cancer. The review also highlighted the individual metabolic pathways in pancreatic cancer and how they enable transitions in immune cells. Finally, the potential of targeting metabolic pathways for effective therapeutic strategies was considered.

The enhancement of glycolysis regulates pancreatic cancer metastasis

Pancreatic ductal adenocarcinoma is prone to distant metastasis and is expected to become the second leading cause of cancer-related death. In an extremely nutrient-deficient and hypoxic environment resulting from uncontrolled growth, vascular disturbances and desmoplastic reactions, pancreatic cancer cells utilize "metabolic reprogramming" to satisfy their energy demand and support malignant behaviors such as metastasis. Notably, pancreatic cancer cells show extensive enhancement of glycolysis, including glycolytic enzyme overexpression and increased lactate production, and this is caused by mitochondrial dysfunction, cancer driver genes, specific transcription factors, a hypoxic tumor microenvironment and stromal cells, such as cancer-associated fibroblasts and tumor-associated macrophages. The metabolic switch from oxidative phosphorylation to glycolysis in pancreatic cancer cells regulates the invasion-metastasis cascade by promoting epithelial-mesenchymal transition, tumor angiogenesis and the metastatic colonization of distant organs. In addition to aerobic glycolysis, oxidative phosphorylation also plays a critical role in pancreatic cancer metastasis in ways that remain unclear. In this review, we expound on the intracellular and extracellular causes of the enhancement of glycolysis in pancreatic cancer and the strong association between glycolysis and cancer metastasis, which we expect will yield new therapeutic approaches targeting cancer metabolism.

Microenvironmental control of glucose metabolism in tumors by regulation of pyruvate dehydrogenase

During malignant progression cancer cells undergo a series of changes, which promote their survival, invasiveness and metastatic process. One of them is a change in glucose metabolism. Unlike normal cells, which mostly rely on the tricarboxylic acid cycle (TCA), many cancer types rely on glycolysis. Pyruvate dehydrogenase complex (PDC) is the gatekeeper enzyme between these two pathways and is responsible for converting pyruvate to acetyl-CoA, which can then be processed further in the TCA cycle. Its activity is regulated by PDP (pyruvate dehydrogenase phosphatases) and PDHK (pyruvate dehydrogenase kinases). Pyruvate dehydrogenase kinase exists in 4 tissue specific isoforms (PDHK1-4), the activities of which are regulated by different factors, including hormones, hypoxia and nutrients. PDHK1 and PDHK3 are active in the hypoxic tumor microenvironment and inhibit PDC, resulting in a decrease of mitochondrial function and activation of the glycolytic pathway. High PDHK1/3 expression is associated with worse prognosis in patients, which makes them a promising target for cancer therapy. However, a better understanding of PDC's enzymatic regulation in vivo and of the mechanisms of PDHK-mediated malignant progression is necessary for the design of better PDHK inhibitors and the selection of patients most likely to benefit from such inhibitors.

Proteomics Unravels the Regulatory Mechanisms in Human Tears Following Acute Renouncement of Contact Lens Use: A Comparison between Hard and Soft Lenses

Contact lenses (CLs) provide a superior alternative to spectacles. Although beneficial, the global burden of ocular dysfunctions attributed to regular use of CLs remains a topic of much challenge in ophthalmic research owing to debilitating clinical repercussions on the ocular surface, which are often manifested as breach in tear film integrity. This study elucidated the intricate tear proteome changes attributed to the use of different CLs (hard and soft) and unravelled, for the first time, the restorative mechanisms of several protein clusters following acute renouncement of CL use employing the label-free mass spectrometry-based quantitative proteomics approach. The expression patterns of certain proteins clusters were specific to the use of a particular lens type and a large majority of these actively regulates cell death and survival and, modulates cellular movement on the ocular surface. Noteworthy, CL use also evoked a significant upregulation of glycolytic enzymes associated with hypoxia and corresponding cognate metabolic pathways, particularly glucose metabolism and FXR/RXR pathways. Importantly, the assessment of CL renouncement unravelled the restorative properties of several clusters of proteins involved mainly in organismal injury and abnormalities and, cellular function and maintenance. These proteins play key roles in restoring tear homeostasis and wound-healing mechanisms post-CL use-elicited injury.

Glucose metabolic phenotype of pancreatic cancer

AIM: To construct a global “metabolic phenotype” of pancreatic ductal adenocarcinoma (PDAC) reflecting tumour-related metabolic enzyme expression.

METHODS: A systematic review of the literature was performed using OvidSP and PubMed databases using keywords “pancreatic cancer” and individual glycolytic and mitochondrial oxidative phosphorylation (MOP) enzymes. Both human and animal studies investigating the oncological effect of enzyme expression changes and inhibitors in both an in vitro and in vivo setting were included in the review. Data reporting changes in enzyme expression and the effects on PDAC cells, such as survival and metastatic potential, were extracted to construct a metabolic phenotype.

RESULTS: Seven hundred and ten papers were initially retrieved, and were screened to meet the review inclusion criteria. 107 unique articles were identified as reporting data involving glycolytic enzymes, and 28 articles involving MOP enzymes in PDAC. Data extraction followed a pre-defined protocol. There is consistent over-expression of glycolytic enzymes and lactate dehydrogenase in keeping with the Warburg effect to facilitate rapid adenosine-triphosphate production from glycolysis. Certain isoforms of these enzymes were over-expressed specifically in PDAC. Altering expression levels of HK, PGI, FBA, enolase, PK-M2 and LDA-A with metabolic inhibitors have shown a favourable effect on PDAC, thus identifying these as potential therapeutic targets. However, the Warburg effect on MOP enzymes is less clear, with different expression levels at different points in the Krebs cycle resulting in a fundamental change of metabolite levels, suggesting that other essential anabolic pathways are being stimulated.

CONCLUSION: Further characterisation of the PDAC metabolic phenotype is necessary as currently there are few clinical studies and no successful clinical trials targeting metabolic enzymes.

Systems medicine: evolution of systems biology from bench to bedside

High-throughput experimental techniques for generating genomes, transcriptomes, proteomes, metabolomes, and interactomes have provided unprecedented opportunities to interrogate biological systems and human diseases on a global level. Systems biology integrates the mass of heterogeneous high-throughput data and predictive computational modeling to understand biological functions as system-level properties. Most human diseases are biological states caused by multiple components of perturbed pathways and regulatory networks rather than individual failing components. Systems biology not only facilitates basic biological research but also provides new avenues through which to understand human diseases, identify diagnostic biomarkers, and develop disease treatments. At the same time, systems biology seeks to assist in drug discovery, drug optimization, drug combinations, and drug repositioning by investigating the molecular mechanisms of action of drugs at a system's level. Indeed, systems biology is evolving to systems medicine as a new discipline that aims to offer new approaches for addressing the diagnosis and treatment of major human diseases uniquely, effectively, and with personalized precision.

The correlation between the expression of differentiated embryo-chondrocyte expressed gene l and oral squamous cell carcinoma

Background

This study aims to explore the correlation between expression of differentiated embryo-chondrocyte expressed gene l (DEC1) and oral squamous cell carcinoma (OSCC), which could provide the reference for treatment and prognosis assessment of OSCC.

Methods

The expression of DEC1 in tissues from 56 primary OSCC patients and 20 normal oral mucosa samples were detected using real-time polymerase chain reaction and immunohistochemical methods, respectively.

Results

The results showed that the positive expression rate of DEC1 in the OSCC group was significantly higher than that in the normal group (P <0.05); further, the expression of DEC1 in different OSCC groups was statistically significant (P <0.05). The expression of DEC1 in the 1-year recurrence OSCC group was significantly higher than other groups. The expression of DEC1 in the 3-years no recurrence OSCC group was the lowest.

Conclusions

The expression of DEC1 was associated with the incidence of OSCC and there was a negative correlation between the expression of DEC1 and the prognosis of OSCC.

Hypoxia inducible factor pathway inhibitors as anticancer therapeutics

Hypoxia is a significant feature of solid tumor cancers. Hypoxia leads to a more malignant phenotype that is resistant to chemotherapy and radiation, is more invasive and has greater metastatic potential. Hypoxia activates the hypoxia inducible factor (HIF) pathway, which mediates the biological effects of hypoxia in tissues. The HIF complex acts as a transcription factor for many genes that increase tumor survival and proliferation. To date, many HIF pathway inhibitors indirectly affect HIF but there have been no clinically approved direct HIF inhibitors. This can be attributed to the complexity of the HIF pathway, as well as to the challenges of inhibiting protein-protein interactions.

Differentiated embryonic chondrocyte-expressed gene 1 is associated with hypoxia-inducible factor 1α and Ki67 in human gastric cancer

Background

Gastric cancer is a leading causes of cancer-related deaths ,but the underlying molecular mechanisms of its progression are largely unknown. Differentiated embryonic chondrocyte-expressed gene 1 (DEC1), is an important transcription factor involved in the progression of tumors and has recently been identified to be strongly inducible by hypoxia. Little is known about the contribution of DEC1 to the intracellular hypoxia and proliferation signaling events in gastric cancer.

Methods

Immunohistochemistry was used to detect the expression of DEC1, hypoxia-inducible factor 1(HIF-1α) and Ki67 in 173 human gastric cancer samples and adjacent non-tumor tissues samples. The relationship between DEC1, HIF-1α and Ki67 was evaluated.

Results

DEC1 protein was persistently expressed in the nucleus and cytoplasm of gastric cancer tissue. The protein expression of DEC1 and HIF-1α in tumour tissues was 83.8% and 54.3%, respectively, and was significantly higher than that in adjacent normal tissues (83.8% vs 23.7%, P <0.001; 54.3% vs 12.7%, P< 0.001). The expression of DEC1 and HIF-1α was associated with poor histological differentiation. (P < 0. 01). Furthermore, DEC1 level was positively correlated with HIF-1α (P < 0. 01, r=0.290) and Ki67 expression (P < 0. 01, r=0.249).

Conclusion

The upregulation of DEC1 may play an important role in hypoxia regulation and cell proliferation in gastric cancer. The relevant molecular mechanism requires further investigation.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1794565980889391med.motic.com/MoticGallery/Slide?id=08d180cd-5fdb-4cee-830a-0b1fef3311f2&user=2C69F0D6-A478-4A2B-ABF0-BB36763E8025med.motic.com/MoticGallery/Slide?id=4762991d-3f2f-43aa-b4bf-ecdd2c2ae3ec&user=2C69F0D6-A478-4A2B-ABF0-BB36763E8025med.motic.com/MoticGallery/Slide?id=2717f209-b3fd-4e71-b621-0d60ea507a82&user=2C69F0D6-A478-4A2B-ABF0-BB36763E8025

Hypoxia-induced transcriptional repression of the melanoma-associated oncogene MITF

Microphthalmia-associated transcription factor (MITF) regulates normal melanocyte development and is also a lineage-selective oncogene implicated in melanoma and clear-cell sarcoma (i.e., melanoma of soft parts). We have observed that MITF expression is potently reduced under hypoxic conditions in primary melanocytes and melanoma and clear cell sarcoma cells through hypoxia inducible factor 1 (HIF1)-mediated induction of the transcriptional repressor differentially expressed in chondrocytes protein 1 (DEC1) (BHLHE40), which subsequently binds and suppresses the promoter of M-MITF (melanocyte-restricted MITF isoform). Correspondingly, hypoxic conditions or HIF1α stabilization achieved by using small-molecule prolyl-hydroxylase inhibitors reduced M-MITF expression, leading to melanoma cell growth arrest that was rescued by ectopic expression of M-MITF in vitro. Prolyl hydroxylase inhibition also potently suppressed melanoma growth in a mouse xenograft model. These studies illuminate a physiologic hypoxia response in pigment cells leading to M-MITF suppression, one that suggests a potential survival advantage mechanism for MITF amplification in metastatic melanoma and offers a small-molecule strategy for suppression of the MITF oncogene in vivo.

The increased expression of DEC1 gene is related to HIF-1α protein in gastric cancer cell lines

Overexpression of differentiated embryo chondrocyte 1 (DEC1) has been reported to contribute to the cellular differentiation, proliferation, and apoptosis of various cancers. Our previous studies have shown that DEC1 was highly expressed in gastric cancer (GCa) tissues. However, there is no report about the expression of DEC1 in GCa cell lines until now. In this study, We evaluated the mRNA and protein expression of DEC1 and hypoxia-inducible factor 1α (HIF-1α) under normoxic and hypoxic conditions in six GCa cell lines: BGC-823, MGC80-3, MKN1, AGS, FU97 and SGC-7901. An HIF-1α protein inhibitor was used to analyze the association of DEC1 and HIF-1α expression. Under normoxia, the mRNA expression of both HIF-1α and DEC1 was moderate, whereas the protein expression of DEC1 was higher than that of HIF-1α. Hypoxia induced the mRNA expression of DEC1 and the protein expression of HIF-1α and DEC1 in a time-dependent manner but had no effect on the mRNA expression of HIF-1α. Furthermore, inhibition of HIF-1α protein expression resulted in a significant decrease in both the mRNA and protein expression of DEC1. Taken together, DEC1 expression is correlated with HIF-1α protein in GCa cell line, blockage of HIF-1α protein led to reduced DEC1 expression. The efficacy of inhibiting HIF-1α and DEC1 expression should be tested in clinical trials as possible treatment for GCa.

Enhancing T3 and cAMP responsive gene participation in the thermogenic regulation of fuel oxidation pathways

OBJECTIVE

We sought to identify glycolysis, glycogenolysis, lipolysis, Krebs cycle, respiratory chain, and oxidative phosphorylation enzymes simultaneously regulated by T3 and cAMP.

MATERIALS AND METHODS

We performed in silico analysis of 56 promoters to search for cis-cAMP (CREB) and cis-thyroid (TRE) response elements, considering UCP1, SERCA2 and glyceraldehyde 3-phosphate dehydrogenase as reference. Only regulatory regions with prior in vitro validation were selected.

RESULTS

29/56 enzymes presented potential TREs in their regulatory sequence, and some scored over 0.80 (better predictive value 1): citrate synthase, phosphoglucose isomerase, succinate dehydrogenases A/C, UCP3, UCP2, UCP4, UCP5, phosphoglycerate mutase, glyceraldehyde 3-P dehydrogenase, glucokinase, malate dehydrogenase, acyl-CoA transferase (thiolase), cytochrome a3, and lactate dehydrogenase. Moreover, some enzymes have not yet been described in the literature as genomically regulated by T3.

CONCLUSION

Our results point to other enzymes which may possibly be regulated by T3 and CREB, and speculate their joint roles in contributing to the optimal thermogenic acclimation.

Hypoxia inducible BHLHB2 is a novel and independent prognostic marker in pancreatic ductal adenocarcinoma

AIMS

The cyclic adenosine monophosphate-inducible basic helix-loop-helix (bHLH) domain containing class-B2 transcriptional factor BHLHB2 is differentially expressed in a number of human malignancies. In the present study, the expression, regulation, functions and prognostic impact of BHLHB2 in pancreatic cancer were investigated.

METHODS

Expression analyses were carried out in tissues of the normal pancreas (n=10) and pancreatic ductal adenocarcinoma (n=77) as well as in eight pancreatic cancer cell lines using quantitative RT-PCR, semiquantitative immunohistochemistry, and immunoblot analyses. In vitro functional experiments were conducted using siRNA transfection, hypoxia, serum starvation, apoptosis induction with gemcitabine and actinomycin-D, and invasion assays. Survival analysis was performed using the Kaplan-Meier method. Prognostic factors were determined in a multivariable analysis using a Cox proportional hazards model.

RESULTS

BHLHB2 mRNA and protein expressions were strongly induced by hypoxia and by serum starvation in pancreatic cancer cell lines. BHLHB2 silencing with RNAi had no significant effects on growth and invasion but increased apoptosis resistance against gemcitabine by reducing caspace-3 cleavage. In BHLHB2 silenced cells the ED50 of gemcitabine increased from 13.95 ± 1.353 to 38.70 ± 5.262 nM (p<0.05). Ex vivo, the weak/absent nuclear staining in normal pancreatic ducts and acinar cells was replaced by moderate to strong nuclear/cytoplasmic staining in PanIN lesions and pancreatic cancer cells. Patients with weak/absent nuclear BHLHB2 staining had significantly worse median survival compared to those with strong staining (13 months vs. 27 months, p=0.03). In a multivariable analysis, BHLHB2 staining was an independent prognostic factor (Hazard-Ratio=2.348, 95% CI=1.250-4.411, p=0.008).

CONCLUSIONS

Hypoxia-inducible BHLHB2 expression is a novel independent prognostic marker in pancreatic cancer patients and indicates increased chemosensitivity towards gemcitabine.

A biology-driven approach identifies the hypoxia gene signature as a predictor of the outcome of neuroblastoma patients

BACKGROUND

Hypoxia is a condition of low oxygen tension occurring in the tumor microenvironment and it is related to poor prognosis in human cancer. To examine the relationship between hypoxia and neuroblastoma, we generated and tested an in vitro derived hypoxia gene signature for its ability to predict patients' outcome.

RESULTS

We obtained the gene expression profile of 11 hypoxic neuroblastoma cell lines and we derived a robust 62 probesets signature (NB-hypo) taking advantage of the strong discriminating power of the l1-l2 feature selection technique combined with the analysis of differential gene expression. We profiled gene expression of the tumors of 88 neuroblastoma patients and divided them according to the NB-hypo expression values by K-means clustering. The NB-hypo successfully stratifies the neuroblastoma patients into good and poor prognosis groups. Multivariate Cox analysis revealed that the NB-hypo is a significant independent predictor after controlling for commonly used risk factors including the amplification of MYCN oncogene. NB-hypo increases the resolution of the MYCN stratification by dividing patients with MYCN not amplified tumors in good and poor outcome suggesting that hypoxia is associated with the aggressiveness of neuroblastoma tumor independently from MYCN amplification.

CONCLUSIONS

Our results demonstrate that the NB-hypo is a novel and independent prognostic factor for neuroblastoma and support the view that hypoxia is negatively correlated with tumors' outcome. We show the power of the biology-driven approach in defining hypoxia as a critical molecular program in neuroblastoma and the potential for improvement in the current criteria for risk stratification.

Tumor suppression by p53: making cells senescent

Cellular senescence is a permanent cell cycle arrest and a potent tumor suppression mechanism. The p53 tumor suppressor is a sequence-specific transcription factor and acts as a central hub sensing various stress signals and activating an array of target genes to induce cell cycle arrest, apoptosis, and senescence. Recent reports showed that restoration of p53 induces premature senescence and tumor regression in mice with hepatocarcinomas or sarcomas. Thus, p53-mediated senescence is capable of eliminating cancer cells in vivo. p63 and p73, two homologues of p53, have similar function in cell cycle arrest and apoptosis. However, the role of p63 and p73 in cellular senescence is elusive. In this review, we will discuss how p53 regulates senescence and future studies about p53 family members in senescence.

Metabolic transformation in cancer

In 2000, Douglas Hanahan and Robert Weinberg published a review detailing the six hallmarks of cancer. These are six phenotypes that a tumour requires in order to become a fully fledged malignancy: persistent growth signals, evasion of apoptosis, insensitivity to anti-growth signals, unlimited replicative potential, angiogenesis and invasion and metastasis. However, it is becoming increasingly clear that these phenotypes do not portray the whole story and that other hallmarks are necessary: one of which is a shift in cellular metabolism. The tumour environment creates a unique collection of stresses to which cells must adapt in order to survive. This environment is formed by the uncontrolled proliferation of cells, which ignore the cues that would create normal tissue architecture. As a result, the cells forming the tumour are exposed to low oxygen and nutrient levels, as well as high levels of toxic cellular waste products, which is thought to propel cells towards a more transformed phenotype, resistant to cell death and pro-metastatic.

FDG PET imaging of Ela1-myc mice reveals major biological differences between pancreatic acinar and ductal tumours

PURPOSE

The aim was to evaluate FDG PET imaging in Ela1-myc mice, a pancreatic cancer model resulting in the development of tumours with either acinar or mixed acinar-ductal phenotype.

METHODS

Transversal and longitudinal FDG PET studies were conducted; selected tissue samples were subjected to autoradiography and ex vivo organ counting. Glucose transporter and hexokinase mRNA expression was analysed by quantitative reverse transcription polymerase chain reaction (RT-PCR); Glut2 expression was analysed by immunohistochemistry.

RESULTS

Transversal studies showed that mixed acinar-ductal tumours could be identified by FDG PET several weeks before they could be detected by hand palpation. Longitudinal studies revealed that ductal--but not acinar--tumours could be detected by FDG PET. Autoradiographic analysis confirmed that tumour areas with ductal differentiation incorporated more FDG than areas displaying acinar differentiation. Ex vivo radioactivity measurements showed that tumours of solely acinar phenotype incorporated more FDG than pancreata of non-transgenic littermates despite the fact that they did not yield positive PET images. To gain insight into the biological basis of the differential FDG uptake, glucose transporter and hexokinase transcript expression was studied in microdissected tumour areas enriched for acinar or ductal cells and validated using cell-specific markers. Glut2 and hexokinase I and II mRNA levels were up to 20-fold higher in ductal than in acinar tumours. Besides, Glut2 protein overexpression was found in ductal neoplastic cells but not in the surrounding stroma.

CONCLUSION

In Ela1-myc mice, ductal tumours incorporate significantly more FDG than acinar tumours. This difference likely results from differential expression of Glut2 and hexokinases. These findings reveal previously unreported biological differences between acinar and ductal pancreatic tumours.

HIF-1: an age-dependent regulator of lens cell proliferation

PURPOSE

The lens grows throughout life, and lens size is a major risk factor for nuclear and cortical cataracts. A previous study showed that the hypoxic environment around the lens suppressed lens growth in older rats. The present study was conducted to investigate the mechanism responsible for the age-dependent decline in lens cell proliferation.

METHODS

Transgenic mice expressing Cre recombinase in the lens were bred to mice containing floxed Hif1a alleles. Transgenic mice expressing oxygen insensitive forms of HIF-1alpha in lens epithelial cells were exposed to room air or 60% oxygen. Proliferation was measured by BrdU labeling and cell death by using the TUNEL assay. Morphology was assessed in histologic sections. HIF-1alpha and p27(KIP1) levels were determined by Western blot. The expression of HIF-regulated genes was assessed on microarrays.

RESULTS

Lenses lacking Hif1a degenerated, precluding study in older animals. Breathing 60% oxygen reduced HIF-1alpha levels and HIF-1-regulated transcripts in lens epithelial cells from young and older lenses. Overexpression of oxygen-insensitive HIF-1alpha had no effect on lens size, but suppressed increased proliferation in response to oxygen. Systemic injection of the iron chelator, 1,10-phenanthroline prevented the degradation of HIF-1alpha and reduced oxygen-induced proliferation. Increasing oxygen decreased levels of p27(KIP1) in the epithelial cells of older mice, which was prevented by expressing oxygen-insensitive forms of HIF-1alpha.

CONCLUSIONS

HIF-1alpha is present and HIF-1 is transcriptionally active throughout life, but suppresses growth only in older lenses. Maintaining elevated levels of p27(KIP1) in older lenses requires HIF-1. p27(KIP1) and other growth regulators may selectively suppress the proliferation of older lens epithelial cells.

The tumor microenvironment and metastatic disease

The microenvironment of solid tumors is a heterogeneous, complex milieu for tumor growth and survival that includes features such as acidic pH, low nutrient levels, elevated interstitial fluid pressure (IFP) and chronic and fluctuating levels of oxygenation that relate to the abnormal vascular network that exists in tumors. The metastatic potential of tumor cells is believed to be regulated by interactions between the tumor cells and their extracellular environment (extracellular matrix (ECM)). These interactions can be modified by the accumulation of genetic changes and by the transient alterations in gene expression induced by the local tumor microenvironment. Clinical and experimental evidence suggests that altered gene expression in response to the hypoxic microenvironment is a contributing factor to increased metastatic efficiency. A number of genes that have been implicated in the metastatic process, involving angiogenesis, intra/extravasation, survival and growth, have been found to be hypoxia-responsive. The various metastatic determinants, genetic and epigenetic, somatic and inherited may serve as precedents for the future identification of more genes that are involved in metastasis. Much research has focused on genetic and molecular properties of the tumor cells themselves. In the present review we discuss the epigenetic and physiological regulation of metastasis and emphasize the need for further studies on the interactions between the pathophysiologic tumor microenvironment and the tumor extracellular matrix.

Graded hypoxia modulates the invasive potential of HT1080 fibrosarcoma and MDA MB231 carcinoma cells

Spatial and temporal oxygen heterogeneity exists in most solid tumour microenvironments due to an inadequate vascular network supplying a dense population of tumour cells. An imbalance between oxygen supply and demand leads to hypoxia within a significant proportion of a tumour, which has been correlated to the likelihood of metastatic dissemination in both rodent tumour models and human patients. Experimentally, it has been demonstrated that near-anoxic in vitro exposure results in transiently increased metastatic potential in some tumour cell lines. The purpose of this study was to examine the effect of graded low oxygen conditions on the invasive phenotype of human tumour cells using an in vitro model of basement membrane invasion, in which we measured oxygen availability directly at the invasion surface of the transwell chamber. Our results show a relationship between culture vessel geometry and time to achieve hypoxia which may affect the interpretation of low oxygen experiments. We exposed the human tumour cell lines, HT1080 and MDA MB231, to graded normobaric oxygen (5% O(2)-0.2% O(2)) either during or prior to in vitro basement membrane invasion to simulate conditions of intravasation and extravasation. A secondary aim was to investigate the potential regulation of matrix metalloproteinase activity by oxygen availability. We identified significant reductions in invasive ability under low oxygen conditions for the HT1080 cell line and an increase in invasion at intermediate oxygen conditions for the MDA MB231 cell line. There were differences in the absolute activity of the individual matrix metalloproteinases, MMP-2, -9, -14, between the two cell lines, however there were no significant changes following exposure to hypoxic conditions. This study demonstrates cell line specific effects of graded oxygen levels on invasive potential and suggests that intermediate levels of low oxygen may increase metastatic dissemination.

The role of autocrine motility factor in tumor and tumor microenvironment

Autocrine motility factor (AMF) is a tumor-secreted cytokine and is abundant at tumor sites, where it may affect the process of tumor growth and metastasis. AMF is a multifunctional protein capable of affecting cell migration, invasion, proliferation, and survival, and possesses phosphoglucose isomerase activity and can catalyze the step in glycolysis and gluconeogenesis. Here, we review the role of AMF and tumor environment on malignant processes. The outcome of metastasis depends on multiple interactions between tumor cells and homeostatic mechanisms, therefore elucidation of the tumor/host interactions in the tumor microenvironment is essential in the development of new prevention and treatment strategies. Such knowledge might provide clues to develop new future therapeutic approaches for human cancers.

ADAM8 expression is associated with increased invasiveness and reduced patient survival in pancreatic cancer

ADAM8 belongs to a family of transmembrane proteins implicated in cell–cell interactions, proteolysis of membrane proteins, and various aspects of carcinogenesis. In the present study, we aimed to evaluate the expression and function of ADAM8 in pancreatic cancer. ADAM8 mRNA levels were analysed by quantitative RT-PCR and correlated to patient survival. Immunohistochemistry was performed to localize ADAM8 in pancreatic tis-sues. Silencing of ADAM8 expression was carried out by transfection with specific siRNA oligonucleotides. Cell growth and invasion assays were used to assess the functional consequences of ADAM8 silencing. SELDI-TOF-MS was performed to detect the proteolytic activity of ADAM8 in pancreatic cancer cells. ADAM8 mRNA was significantly overexpressed in pancreatic ductal adenocarcinoma (PDAC) compared with normal pancreatic tissues (5.3-fold increase; P= 0.0008), and high ADAM8 mRNA and protein expression levels correlated with reduced survival time of PDAC patients (P= 0.048 and P= 0.065, respectively). Silencing of ADAM8 expression did not significantly influence pancreatic cancer cell growth but suppressed invasiveness. In addition, decreased proteolytic activity was measured in cell culture supernatants following silencing of ADAM8. In conclusion, ADAM8 is overexpressed in PDAC, influences cancer cell invasiveness and correlates with reduced survival, suggesting that ADAM8 might be a potential target in pancreatic cancer therapy.

Transforming growth factor-beta promotes survival of mammary carcinoma cells through induction of antiapoptotic transcription factor DEC1

Transforming growth factor-beta (TGF-beta) signaling facilitates tumor growth and metastasis in advanced cancer. In the present study, we identified differentially expressed in chondrocytes 1 (DEC1, also known as SHARP2 and Stra13) as a downstream target of TGF-beta signaling, which promotes the survival of breast cancer cells. In the mouse mammary carcinoma cell lines JygMC(A) and 4T1, the TGF-beta type I receptor kinase inhibitors A-44-03 and SB431542 induced apoptosis of cells under serum-free conditions. Oligonucleotide microarray and real-time reverse transcription-PCR analyses revealed that TGF-beta induced DEC1 in these cells, and the increase of DEC1 was suppressed by the TGF-beta type I receptor kinase inhibitors as well as by expression of dominant-negative TGF-beta type II receptor. Overexpression of DEC1 prevented the apoptosis of JygMC(A) cells induced by A-44-03, and knockdown of endogenous DEC1 abrogated TGF-beta-promoted cell survival. Moreover, a dominant-negative mutant of DEC1 prevented lung and liver metastasis of JygMC(A) cells in vivo. Our observations thus provide new insights into the molecular mechanisms governing TGF-beta-mediated cell survival and metastasis of cancer.

bHLH-Orange Transcription Factors in Development and Cancer

Basic helix-loop-helix (bHLH) proteins are a large superfamily of transcription factors that play critical roles in many physiological processes including cellular differentiation, cell cycle arrest and apoptosis. Based on structural and phylogenetic analysis, mammalian bHLH-Orange (bHLH-O) proteins, which constitute the repressor family of bHLH factors, can be grouped into four subfamilies: Hes, Hey, Helt and Stra13/Dec. In addition to the bHLH domain that mediates DNA-binding and protein dimerization, all members of this family are characterized by a distinctive motif called the "Orange domain" which is present exclusively in these factors. Genetic studies using targeted mutagenesis in mice have revealed essential roles for many bHLH-O genes in embryonic development, cell fate decisions, differentiation of a number of cell types and in apoptosis. Furthermore, growing evidence of crosstalk between bHLH-O proteins with the tumor suppressors p53 and hypoxia-inducible factor, have started to shed light on their possible roles in oncogenesis. Consistently, deregulated expression of several bHLH-O factors is associated with various human cancers. Here, we review the structure and biological functions of bHLH-O factors, and discuss recent studies that suggest a potential role for these factors in tumorigenesis and tumor progression.

Glycolysis inhibition for anticancer treatment

Most cancer cells exhibit increased glycolysis and use this metabolic pathway for generation of ATP as a main source of their energy supply. This phenomenon is known as the Warburg effect and is considered as one of the most fundamental metabolic alterations during malignant transformation. In recent years, there are significant progresses in our understanding of the underlying mechanisms and the potential therapeutic implications. Biochemical and molecular studies suggest several possible mechanisms by which this metabolic alteration may evolve during cancer development. These mechanisms include mitochondrial defects and malfunction, adaptation to hypoxic tumor microenvironment, oncogenic signaling, and abnormal expression of metabolic enzymes. Importantly, the increased dependence of cancer cells on glycolytic pathway for ATP generation provides a biochemical basis for the design of therapeutic strategies to preferentially kill cancer cells by pharmacological inhibition of glycolysis. Several small molecules have emerged that exhibit promising anticancer activity in vitro and in vivo, as single agent or in combination with other therapeutic modalities. The glycolytic inhibitors are particularly effective against cancer cells with mitochondrial defects or under hypoxic conditions, which are frequently associated with cellular resistance to conventional anticancer drugs and radiation therapy. Because increased aerobic glycolysis is commonly seen in a wide spectrum of human cancers and hypoxia is present in most tumor microenvironment, development of novel glycolytic inhibitors as a new class of anticancer agents is likely to have broad therapeutic applications.

A comparative gene-expression analysis of CD34+ hematopoietic stem and progenitor cells grown in static and stirred culture systems

Static and stirred culture systems are widely used to expand hematopoietic cells, but differential culture performances are observed between these systems. We hypothesize that these differential culture outcomes are caused by the physiological responses of CD34⁺ hematopoietic stem and progenitor cells (HSPCs) to the different physical microenvironments created in these culture devices. To understand the genetic changes provoked by culture microenvironments, the gene expression profiling of CD34⁺ HSPCs grown in static and stirred culture systems was compared using SMART-PCR and cDNA arrays. The results revealed that 103 and 99 genes were significantly expressed in CD34⁺ cells from static and stirred systems, respectively. Of those, 91 have similar levels of expression, while 12 show differential transcription levels. These differentially expressed genes are mainly involved in anti-oxidation, DNA repair, apoptosis, and chemotactic activity. A quantitative molecular understanding of the influences of growth microenvironments on transcriptional events in CD34⁺ HSPCs should give new insights into optimizing culture strategies to produce hematopoietic cells.

Patients with inflammatory arthritic diseases harbor elevated serum and synovial fluid levels of free and immune-complexed glucose-6-phosphate isomerase (G6PI)

In K/BxN mice, anti-glucose-6-phosphate isomerase (G6PI) IgG antibodies (Abs) cause joint-specific inflammation and destruction. Anti-G6PI Abs are also present in humans with inflammatory arthritis, especially among patients with rheumatoid arthritis (RA). A contributing factor to the induction of such autoantibodies may be upregulated expression of the corresponding antigen G6PI in affected tissues and/or increased levels of G6PI in the circulation. To determine G6PI levels and the presence of free G6PI and/or G6PI-containing immune complexes in sera and synovial fluids (SF) of patients with different arthritides, serum and SF obtained concomitantly from 91 clinically well-defined arthritis patients were assessed in a blinded manner for G6PI enzymatic assay and for G6PI protein concentration by ELISA. Sera and SF from patients with immune-based inflammatory arthritis contained significantly higher levels of G6PI enzymatic activity compared to sera or SF from patients with non-immune-based inflammatory arthritis or healthy controls. In addition, significantly higher levels of total G6PI protein concentration (including both enzymatically active and inactive forms) were present in sera of RA patients vs. those with other immune-based or non-immune-based inflammatory arthritis.G6PI in sera and SF were present both as G6PI-containing immune complexes and as free G6PI, with the majority of free G6PI existing as tetramers with lesser amounts of dimers and monomers. Levels of G6PI enzymatic activity in the sera of most immune-based inflammatory arthritis patients are elevated and may reflect ongoing inflammation and cell destruction. The high serum levels of enzymatically inactive forms of G6PI in RA relative to those in other arthritic diseases are partially due to G6PI-containing immune complexes, a portion of which also contains C1q. Overall, our study supports the notion that elevated G6PI levels present in patients with immune-based inflammatory arthritis may contribute to elevated levels of anti-G6PI Abs and G6PI/anti-G6PI immune complexes. This, in turn, may trigger production of proinflammatory cytokines and perpetuate the inflammatory process.

Cellular differentiation determines the expression of the hypoxia-inducible protein NDRG1 in pancreatic cancer

N-myc downstream-regulated gene-1 (NDRG1) is a recently described hypoxia-inducible protein that is upregulated in various human cancers. Pancreatic ductal adenocarcinoma, called pancreatic cancer, is a highly aggressive cancer that is characterised by its avascular structure, which results in a severe hypoxic environment. In this study, we investigated whether NDRG1 is upregulated in these tumours, thus providing a novel marker for malignant cells in the pancreas. By immunohistochemistry, we observed that NDRG1 was highly expressed in well-differentiated cells of pancreatic cancer, whereas the poorly differentiated tumour cells were negative. In addition, hyperplastic islets and ducts of nonquiescent pancreatic tissue were positive. To further explore its selective expression in tumours, two well-established pancreatic cancer cell lines of unequal differentiation status were exposed to 2% oxygen. NDRG1 mRNA and protein were upregulated by hypoxia in the moderately differentiated Capan-1 cells; however, its levels remained unchanged in the poorly differentiated Panc-1 cell line. Taken together, our data suggest that NDRG1 will not serve as a reliable marker of tumour cells in the pancreas, but may serve as a marker of differentiation. Furthermore, we present the novel finding that cellular differentiation may be an important factor that determines the hypoxia-induced regulation of NDRG1.

Molecular cloning and characterization of beta-expansin gene related to root hair formation in barley

Root hairs are specialized epidermal cells that play a role in the uptake of water and nutrients from the rhizosphere and serve as a site of interaction with soil microorganisms. The process of root hair formation is well characterized in Arabidopsis (Arabidopsis thaliana); however, there is a very little information about the genetic and molecular basis of root hair development in monocots. Here, we report on isolation and cloning of the beta-expansin (EXPB) gene HvEXPB1, tightly related to root hair initiation in barley (Hordeum vulgare). Using root transcriptome differentiation in the wild-type/root-hairless mutant system, a cDNA fragment present in roots of wild-type plants only was identified. After cloning of full-length cDNA and genomic sequences flanking the identified fragment, the subsequent bioinformatics analyses revealed homology of the protein coded by the identified gene to the EXPB family. Reverse transcription-PCR showed that expression of HvEXPB1 cosegregated with the root hair phenotype in F2 progeny of the cross between the hairless mutant rhl1.a and the wild-type Karat parent variety. Expression of the HvEXPB1 gene was root specific; it was expressed in roots of wild-type forms, but not in coleoptiles, leaves, tillers, and spikes. The identified gene was active in roots of two other analyzed root hair mutants: rhp1.a developing root hair primordia only and rhs1.a with very short root hairs. Contrary to this, a complete lack of HvEXPB1 expression was observed in roots of the spontaneous root-hairless mutant bald root barley. All these observations suggest a role of the HvEXPB1 gene in the process of root hair formation in barley.

Temporal transcriptome of mouse ATDC5 chondroprogenitors differentiating under hypoxic conditions

The formation of cartilage takes place in vivo in an environment of reduced oxygen tension. To study the effect of hypoxia on the process of chondrogenesis, ATDC5 mouse chondroprogenitor cells were induced to differentiate by the addition of insulin and cultured under ambient and hypoxic conditions corresponding to 21% and 1% O2 in the gas phase, respectively. The production of extracellular proteoglycans as well as the transcriptional profile of 104 selected genes was determined by real-time RT-PCR. Hypoxia alone induced early chondrogenesis as evidenced by the synthesis of glycosaminoglycans and expression of aggrecan and collagen type II genes. Surprisingly, however, hypoxic incubation of insulin-treated cells delayed and suppressed the insulin-mediated early chondrogenesis and almost completely blocked hypertrophic differentiation. Analysis of the gene expression yielded several clues as to the mechanisms involved. In addition, a group of genes was identified that have not previously been associated with hypoxia, including Ak4, Akt3, Col X, Fmod, Ier3, IGFbp4, MafF, Mxi1, Rcor2, Rras, Sox6, Tnni2, Wnt5a, and Zfp313.

Growth properties of colonic tumor cells are a function of the intrinsic mitochondrial membrane potential

Development of malignant transformation in the colonic mucosa includes disruption in the equilibrium between proliferation and apoptosis, decreased expression and deletions of the mitochondrial genome, alterations in mitochondrial enzymatic activity, and elevations in the mitochondrial membrane potential (Deltapsim). Focusing on the role of the Deltapsim in tumor development and progression, we generated novel isogenic colonic carcinoma cell lines that exhibit highly significant, stable differences in their intrinsic Deltapsim. Using these cell lines, we have recently shown that the intrinsic Deltapsim has a significant influence on steady state mitochondrial activity and the extent to which cells enter butyrate-mediated growth arrest and apoptotic cascades. Here, we report that the Deltapsim is also profoundly linked to important tumorigenic properties of the cells. Compared with cells with lower Deltapsim, cells with elevated intrinsic Deltapsim have an enhanced capacity to (a) respond to hypoxia by avoiding apoptosis and initiating angiogenesis, (b) escape anoikis and grow under anchorage-independent conditions, and (c) invade the basement membrane. Combined with our previous work, these data implicate the intrinsic Deltapsim of colonic carcinoma cells in determining the probability of tumor expansion and progression.

Current understanding of HIF in renal disease

Hypoxia-inducible factors (HIF) are ubiquitous transcription factors regulated by oxygen-dependent proteolysis, and hence rapidly mount an adaptational response to hypoxia. The HIF system is apparently more complex than initially considered in the perspective of the increasing number of HIF target genes, and the inter-relationship with various additional regulatory pathways. Regional hypoxia is believed to play a major role in renal disease. Experimental data confirm a role for HIF in renal pathophysiology. The discovery of HIF prolyl-hydroxylases as key enzymes of oxygen sensing and HIF proteolysis offer new possibilities to therapeutically target HIF. Herein, we review basic concepts of HIF regulation, and existing data on HIF activation in renal disease.

Regulation of phosphoglucose isomerase/autocrine motility factor expression by hypoxia

Phosphoglucose isomerase (PGI; EC 5.3.1.9) is a housekeeping cytosolic enzyme of the sugar metabolism pathways that plays a key role in glycolysis and gluconeogenesis. PGI is a multifunctional dimeric protein that extracellularly acts as a cytokine with properties that include autocrine motility factor (AMF) eliciting mitogenic, motogenic, differentiation functions and has been implicated in tumor progression and metastasis. Since metastasis is regulated in part by hypoxia, which induces the transcription of metastasis-associated genes and anaerobic glycolic metabolism, we questioned whether hypoxia also regulates the expression level of tumor cells' PGI/AMF. We establish here that in the human breast carcinoma BT-549 cells hypoxia enhanced expression of the transcription factor hypoxia-inducible factor (HIF)-1, which in turn led to the up-regulation of PGI/AMF expression and was specifically inhibited by inhibitors of the phosphatidylinositol 3'-kinase signaling pathway. In addition, the hypoxia induction of PGI/AMF expression was suppressed by inhibitors of vascular endothelial growth factor (VEGF) or VEGF receptors, suggesting that hypoxia-inducible VEGF regulates the PGI/AMF expression. Hypoxia also enhanced cancer cell motility, and these effects were strongly inhibited by the PGI/AMF, VEGF, or VEGF receptor inhibitors. The results presented here suggest that under hypoxic conditions the expression of PGI/AMF is regulated in part by the HIF pathway, which in turn increases the flow of the glycolytic cascade leading to an increased anaerobic energy generation; thus, inhibition of PGI/AMF expression and activities may provide a new therapeutic modality for treatment of hypoxic tumors.

The expression of antiapoptotic protein survivin is transcriptionally upregulated by DEC1 primarily through multiple sp1 binding sites in the proximal promoter

Human differentially expressed in chondrocytes (DEC), mouse stimulated with retinoic acid and rat split and hairy related proteins constitute a structurally distinct class of the basic helix-loop-helix proteins. DEC1 is abundantly expressed in tumors and protects against apoptosis induced by serum starvation. In this study, we report that DEC1 antiapoptosis is achieved by inducing survivin, an antiapoptotic protein. In paired tumor-normal tissues, survivin and DEC1 exhibited a paralleled expression pattern. Tetracycline-induced expression of DEC1 in stable lines proportionally increased the expression of survivin. In reporter assays, DEC1 transactivated the survivin promoter but repressed the DEC2 promoter. In contrast to the repression, the activation was delayed and varied depending on serum concentrations and cycle blockers. Studies with reporter mutants located, in the survivin promoter, two Sp1 sites that supported DEC1 transactivation. Electrophoretic mobility shift assay and chromatin immunoprecipitation detected the presence of DEC1 in the survivin promoter. These findings establish that the survivin gene is a transcription target of DEC1, and induction of survivin is at least in part responsible for DEC1 antiapoptosis.

The hypoxic proteome is influenced by gene-specific changes in mRNA translation

BACKGROUND AND PURPOSE

Hypoxia causes a rapid reduction in mRNA translation efficiency. This inhibition does not affect all mRNA species to the same extent and can therefore contribute significantly to hypoxia-induced differential protein expression. Our aim in this study was to characterize changes in gene expression during acute hypoxia and evaluate the contribution of regulation via mRNA translation on these changes. For each gene, the contribution of changes in mRNA abundance versus mRNA translation was determined.

MATERIALS AND METHODS

DU145 prostate carcinoma cells were exposed to 4h of hypoxia (<0.02% O2). Efficiently translated mRNAs were isolated by sedimentation through a sucrose gradient. Affymetrix microarray technology was used to evaluate both the transcriptional and translational contribution to gene expression. Results were validated by quantitative PCR.

RESULTS

One hundred and twenty genes were more than 4-fold upregulated by hypoxia in the efficiently translated fraction of mRNA, in comparison to only 76 genes at the level of transcription. Of the 50 genes demonstrating the largest changes in translation, 11 were found to be more than 2-fold over represented in the translated fraction in comparison to their overall transcriptional level. The gene with the highest translational contribution to its induction was CITED-2, which is a negative regulator of HIF-1 transcriptional activity.

CONCLUSIONS

Gene-specific regulation of mRNA translation contributes significantly to differential gene expression during hypoxia.

pH-specific sequestration of phosphoglucose isomerase/autocrine motility factor by fibronectin and heparan sulphate

Phosphoglucose isomerase (PGI) is a glycolytic enzyme that moonlights as a cytokine under the aliases autocrine motility factor (AMF), neuroleukin and maturation factor. The cytokine function of PGI/AMF targets multiple cell types however mechanisms that regulate and sequester this ubiquitous, circulating cytokine remain largely unidentified. PGI/AMF is shown here to exhibit fibronectin (FN)-dependent cell surface association at both neutral and acid pH. Direct PGI/AMF binding to FN and fluorescence resonance energy transfer (FRET) between PGI/AMF and FN were detected only at pH 5. At neutral pH, the interaction of PGI/AMF with FN is receptor-mediated requiring prior clathrin-dependent endocytosis. PGI/AMF and FN do not co-internalize and PGI/AMF undergoes a second round of endocytosis upon recycling to the plasma membrane indicating that recycling PGI/AMF receptor complexes associate with FN fibrils. Heparan sulphate does not affect cell association of PGI/AMF at neutral pH but enhances the FN-independent cell surface association of PGI/AMF at acid pH identifying two distinct mechanisms for PGI/AMF sequestration under acidic conditions. However, only PGI/AMF sequestration by FN at acid pH was able to stimulate cell motility upon pH neutralization identifying FN as a pH-dependent cytokine trap for PGI/AMF. The multiple ways of cellular association of PGI/AMF may represent acquired mechanisms to regulate and harness the cytokine function of PGI/AMF.

Hypoxia induces chondrocyte-specific gene expression in mesenchymal cells in association with transcriptional activation of Sox9

Endochondral bone is formed during an avascular period in an environment of low oxygen. Under these conditions, pluripotential mesenchymal stromal cells preferentially differentiate into chondrocytes and form cartilage. In this study, we investigated the hypothesis that oxygen tension modulates bone mesenchymal cell fate by altering the expression of genes that function to promote chondrogenesis. Microarray of RNA samples from ST2 cells revealed significant changes in 728 array elements (P < 0.01) in response to hypoxia. Real-time PCR on these RNA samples, and separate samples from C3H10T1/2 cells, revealed hypoxia-induced changes in the expression of additional genes known to be expressed by chondrocytes including Sox9 and its downstream targets aggrecan and Col2a. These changes were accompanied by the accumulation of mucopolysacharide as detected by alcian blue staining. To investigate the mechanisms responsible for upregulation of Sox9 by hypoxia, we determined the effect of hypoxia on HIF-1alpha levels and Sox9 promoter activity in ST2 cells. Hypoxia increased nuclear accumulation of HIF-1alpha and activated the Sox9 promoter. The ability of hypoxia to transactivate the Sox9 promoter was virtually abolished by deletion of HIF-1alpha consensus sites within the proximal promoter. These findings suggest that hypoxia promotes the differentiation of mesenchymal cells along a chondrocyte pathway in part by activating Sox-9 via a HIF-1alpha-dependent mechanism.

Expression of Autocrine Motility Factor Correlates with the Angiogenic Phenotype of and Poor Prognosis for Human Gastric Cancer

Autocrine motility factor (AMF) is a cytokine known to regulate tumor cell motility. Recent studies have extended its role to many other aspects of cancer biology. In the present study, we examined the level of AMF expression and its relationship with vascular endothelial growth factor (VEGF) expression and the angiogenic phenotype in human gastric cancer and their effect on survival. The AMF and VEGF expression level and tumor microvessel density (MVD) status in archived tissue specimens from 86 resected gastric cancer cases were determined. AMF expression was significantly higher in both primary tumors and lymph node metastases than in adjacent normal gastric mucosa and normal gastric mucosa from individuals without gastric cancer. In univariate survival analyses, strong AMF expression was associated with inferior survival (P = 0.028). In a Cox proportional hazards model, strong AMF expression (P = 0.019) was independently prognostic of poor survival. Strong AMF expression in the lymph node metastases was associated with poor survival (P = 0.011). Furthermore, AMF expression in the primary tumors was directly correlated with VEGF expression and MVD status. We found the first clinical evidence that AMF expression is directly correlated with VEGF expression and MVD status and predicts clinical outcome in patients with gastric cancer, supporting the hypothesis that the AMF/AMF receptor pathway plays an important role in multiple aspects of cancer biology.

Hypoxia-inducible factor-1 drives the motility of the erythroid progenitor cell line, UT-7/Epo, via autocrine motility factor

OBJECTIVE

It is well known that hypoxic stress strongly enhances erythropoiesis, but the effect of hypoxia on erythroid progenitors has not been examined precisely. In the present study, using the erythropoietin-dependent cell line UT-7/Epo, which has characteristics of erythroid progenitors, we investigated a novel role of hypoxia in erythropoiesis.

METHODS

UT-7/Epo and four other hematopoietic and lymphoid cell lines (HL-60, THP-1, Raji, and CEM) were cultured in 20%, 5%, or 1% O2. Morphology was observed under a phase-contrast microscope. Cell motility was evaluated using the Transwell migration assay. An analysis of the protein level of hypoxia-inducible factor-1 (HIF-1) alpha and autocrine motility factor (AMF) was conducted using Western blotting and immunocytochemistry, respectively. Reverse transcription polymerase chain reaction was performed to evaluate the expression of AMF mRNA. Human bone marrow stromal cells were used in cocultures with UT-7/Epo. Apoptosis of UT-7/Epo was examined by immunocytochemistry using an antiactive form of caspase 3 antibody.

RESULTS

Among the five cell lines, UT-7/Epo exhibited active pseudopodial extension in hypoxia (1% O2), and cell motility was increased. HL-60, THP-1, Raji, and CEM did not show an increase in cell motility even in 1% O2. In addition, expression of the alpha-subunit of HIF-1 was activated by hypoxia, and expression of the mRNA and protein of AMF induced by HIF-1, increasing cell motility, was promoted. The addition of an HIF-1 inhibitor, cadmium chloride (CdCl2), or alpha-ketoglutarate (2-oxoglutarate) decreased the AMF mRNA expression, and an AMF inhibitor, erythrose 4-phosphate, decreased the cell motility. When UT-7/Epo was cocultured with human bone marrow-derived stromal cells that significantly inhibit the apoptosis of UT-7/Epo, the migration of UT-7/Epo under the stromal cells (pseudoemperipolesis) was increased in hypoxia.

CONCLUSION

Under hypoxic conditions, erythroid progenitors may exhibit active migration in the bone marrow and the opportunity for contact with stromal cells increases, inhibiting apoptosis.

Differential Regulation of Phosphoglucose Isomerase/Autocrine Motility Factor Activities by Protein Kinase CK2 Phosphorylation

Phosphoglucose isomerase (PGI; EC 5.3.1.9) is a cytosolic housekeeping enzyme of the sugar metabolism pathways that plays a key role in both glycolysis and gluconeogenesis. PGI is a multifunctional dimeric protein that extracellularly acts as a cytokine with properties that include autocrine motility factor (AMF)-eliciting mitogenic, motogenic, and differentiation functions, and PGI has been implicated in tumor progression and metastasis. Little is known of the biochemical regulation of PGI/AMF activities, although it is known that human PGI/AMF is phosphorylated at Ser(185) by protein kinase CK2 (CK2); however, the physiological significance of this phosphorylation is unknown. Thus, by site-directed mutagenesis, we substituted Ser(185) with aspartic acid (S185D) or glutamic acid (S185E), which introduces a negative charge and conformational changes that mimic phosphorylation. A Ser-to-Ala mutant protein (S185A) was generated to abolish phosphorylation. Biochemical analyses revealed that the phosphorylation mutant proteins of PGI exhibited decreased enzymatic activity, whereas the S185A mutant PGI protein retained full enzymatic activity. PGI phosphorylation by CK2 also led to down-regulation of enzymatic activity. Furthermore, CK2 knockdown by RNA interference was associated with up-regulation of cellular PGI enzymatic activity. The three recombinant mutant proteins exhibited indistinguishable cytokine activity and receptor-binding affinities compared with the wild-type protein. In both in vitro and in vivo assays, the wild-type and S185A mutant proteins underwent active species dimerization, whereas both the S185D and S185E mutant proteins also formed tetramers. These results demonstrate that phosphorylation affects the allosteric kinetic properties of the enzyme, resulting in a less active form of PGI, whereas non-phosphorylated protein species retain cytokine activity. The process by which phosphorylation modulates the enzymatic activity of PGI thus has an important implication for the understanding of the biological regulation of this key glucose metabolism-regulating enzyme.

Tumor hypoxia correlates with metastatic tumor growth of pancreatic cancer in an orthotopic murine model

BACKGROUND

The role of tumor hypoxia has become a major focus in cancer research since it influences both local and systemic tumor growth. Oxygen measurements taken in human pancreatic cancer have shown extremely low oxygen tension. The aim of this study was to develop an orthotopic model for pancreatic cancer that mimics the specific tumor microenvironment and to evaluate the role of tumor oxygenation in local tumor growth and systemic dissemination in this model.

MATERIALS AND METHODS

We used two established human pancreatic cancer cell lines for xenobiotic tumor induction. After subcutaneous tumor formation one small tumor piece was transplanted into the pancreatic parenchyma of mice of the different study groups. Upon orthotopic tumor induction tumor oxygenation was measured with the Eppendorf histograph. Histological evaluation was performed with pimonidazole, an in vivo marker of hypoxia.

RESULTS

The tumor take rate was 100% in this model. Metastatic tumor dissemination occurred within the abdominal cavity, and distant metastasis were observed in the lung parenchyma. Oxygen measurements taken in various abdominal organs and xenograft tumor showed a high variation between different organs and xenografted tumors. Tumor oxygenation correlated well with the metastatic score in this model. Furthermore hypoxia was found both in the tumor center and also at the rim of a growing tumor mass. A high number of hypoxic cells were detectable in metastases located in the lung parenchyma.

CONCLUSION

This study provides experimental evidence that tumor hypoxia influences metastatic disease progression and supports recent assumptions that tumor hypoxia is actively involved in progression of pancreatic cancer. It further demonstrates that tumor hypoxia is not only found in the center of a tumor mass, but also occurs at the invasion front.

Autocrine motility factor signaling induces tumor apoptotic resistance by regulations Apaf-1 and Caspase-9 apoptosome expression

Autocrine motility factor (AMF) is a cytokine that regulates locomotion and metastasis of tumor cells. It is well known that expression levels of AMF secretion and its receptor (AMF R) are closely related to tumor malignancy and rheumatoid arthritis. We have established that AMF signaling induced anti-apoptotic activity and that human fibrosarcoma HT-1080 line that secreted high levels of AMF were resistant to drug-induced apoptosis. These cells did not express the apoptotic protease activating factor-1 (Apaf-1) and Caspase-9 genes that encode for the proteins that form the "apoptosome" complex. The disappearance of the Apaf-1 and Caspase-9 gene was recovered by a cellular signaling inhibitor of protein kinase C, phosphatidylinositol 3-phosphate kinase and mitogen-activated protein kinase of the in vitro cultured human fibrosarcoma HT-1080 line. Treatment with these inhibitors favored apoptotic cell death induced by anti-cancer drugs of the murine ascites Ehrlich line. Apoptotic resistance of tumor cells allows them to escape death from cancer chemotherapy, so an understanding of malignant anti-apoptotic activities is important. Antibodies against AMF induced Ehrlich ascites apoptosis in vitro, and effectively aided in vivo apoptosis induced by anti-cancer drugs. The results might indicate a novel route by which tumor cells protect themselves with products, such as AMF, and proliferate despite various stresses and chemical insults; AMF regulates expression of Apaf-1 and caspase-9 genes via a complex signaling pathway and indirectly regulates formation of the apoptosome.

Tumor hypoxia: a target for selective cancer therapy

Tumor hypoxia has been considered to be a potential therapeutic problem because it renders solid tumors more resistant to sparsely ionizing radiation (IR) and chemotherapeutic drugs. Moreover, recent laboratory and clinical data have shown that tumor hypoxia is also associated with a more malignant phenotype and poor survival in patients suffering from various solid tumors. Therefore, selective targeting of hypoxic tumor cells has been explored, and since severe hypoxia (pO(2) < 0.33%, 2.5 mmHg) does not occur in normal tissue, tumor hypoxia could be exploited for therapeutic advantage. However, the following three characteristics of hypoxic tumor regions present obstacles in targeting hypoxic cells. First, it is difficult to deliver a sufficient amount of drug to a region that is remote from blood vessels. Second, one must specifically target hypoxic tumor cells while sparing normal well-oxygenated tissue from damage. Finally, the severely hypoxic tumor cells to be attacked have often stopped dividing. Therefore, high delivery efficiency, high specificity and selective cytotoxicity are all necessary to target and combat hypoxic tumor cells. The current review describes progress on the biological aspects of tumor hypoxia and provides a compilation of the recent molecular approaches used to target hypoxic tumors. These approaches include our work with a unique hypoxia-targeting protein drug, TOP3, with which we have sought to address the above three difficulties.

Acid-induced conformational changes in phosphoglucose isomerase result in its increased cell surface association and deposition on fibronectin fibrils

Phosphoglucose isomerase (PGI) is a glycolytic enzyme that exhibits extracellular cytokine activity as autocrine motility factor, neuroleukin, and maturation factor and that has been recently implicated as an autoantigen in rheumatoid arthritis. In contrast to its receptor-mediated endocytosis at neutral pH, addition of 25 microg/ml of either Alexa 568- or FITC-conjugated PGI to NIH-3T3 cells at progressively acid pH results in its quantitatively increased association with cell surface fibrillar structures that is particularly evident at pH 5. A similar pH-dependent cell surface association of PGI is observed for first passage human chondrocytes obtained from osteoarthritic joints. At acid pH, PGI colocalizes with fibronectin fibrils, and this association occurs directly upon addition of PGI to the cells. In contrast to the receptor-mediated endocytosis of PGI, fibril association of 25 microg/ml PGI at pH 5 is not competed with an excess (2 mg/ml) of unlabeled PGI. PGI binding at acid pH is therefore neither saturable nor mediated by its receptor. PGI is enzymatically active as a dimer and we show here by non-denaturing gel electrophoresis as well as by glutaraldehyde cross-linking that it exists at neutral pH in a tetrameric form. Increasingly acid pH results in the appearance of PGI monomers that correlates directly with its enhanced cell surface association. However, glutaraldehyde cross-linked PGI is endocytosed at neutral pH and still exhibits enhanced cell surface binding at pH 5. Circular dichroism analysis revealed pH-dependent changes in the near but not the far UV spectra indicating that the tertiary structure of the protein is specifically altered at pH 5. Conformational changes of PGI and exposure of the monomer-monomer interface under acidic conditions, such as those encountered in the synovial fluid of arthritic joints, could therefore result in its deposition on the surface of joints and the induction of an autoimmune response.