The role of extracellular signal-regulated protein kinase in transcriptional regulation of the hypoxia marker carbonic anhydrase IX

A CAF-Fueled TIMP-1/CD63/ITGB1/STAT3 Feedback Loop Promotes Migration and Growth of Breast Cancer Cells

Simple Summary

Carcinoma-associated fibroblasts (CAFs) are a major cellular component of the tumor microenvironment and influence cancer cell behavior in numerous ways. A large part of their actions is based on their high secretory activity, leading to the exposure of cancer cells to all kinds of bioactive factors, such as interleukin-6 (IL-6). Here, we present data showing that CAF-derived TIMP-1 activates STAT3 in breast cancer cells in cooperation with CD63 and integrin β1. In turn, STAT3 increases TIMP-1 secretion by breast cancer cells, leading to a TIMP-1/CD63/integrin β1/STAT3 positive feedback loop, which can be further fueled by IL-6. Functionally, this feedback loop is important for the CAF-induced increase in migratory activity and for CAF-induced resistance to the anti-estrogen fulvestrant.

Abstract

TIMP-1 is one of the many factors that CAFs have been shown to secret. TIMP-1 can act in a tumor-supportive or tumor-suppressive manner. The purpose of this study was to elucidate the role of CAF-secreted TIMP-1 for the effects of CAFs on breast cancer cell behavior. Breast cancer cells were exposed to conditioned medium collected from TIMP-1-secreting CAFs (CAF-CM), and the specific effects of TIMP-1 on protein expression, migration and growth were examined using TIMP-1-specifc siRNA (siTIMP1), recombinant TIMP-1 protein (rhTIMP-1) and TIMP-1 level-rising phorbol ester. We observed that TIMP-1 increased the expression of its binding partner CD63 and induced STAT3 and ERK1/2 activation by cooperating with CD63 and integrin β1. Since TIMP-1 expression was found to be dependent on STAT3, TIMP-1 activated its own expression, resulting in a TIMP-1/CD63/integrin β1/STAT3 feedback loop. IL-6, a classical STAT3 activator, further fueled this loop. Knock-down of each component of the feedback loop prevented the CAF-induced increase in migratory activity and inhibited cellular growth in adherent cultures in the presence and absence of the anti-estrogen fulvestrant. These data show that TIMP-1/CD63/integrin β1/STAT3 plays a role in the effects of CAFs on breast cancer cell behavior.

Role of carbonic anhydrases in ferroptosis-resistance

Iron is essential for all the lives on earth but may trigger a switch toward ferroptosis, a novel form of regulated necrosis. Carbonic anhydrases (CAs) are ubiquitous enzymes from microbes to humans. The primary function of CAs is to regulate cellular pH by hydrating carbon dioxide (CO₂) to protons (H⁺) and bicarbonate ions (HCO₃^-). Furthermore, CAs play roles in biosynthetic reactions, such as gluconeogenesis, lipogenesis, ureagenesis and are also associated with tumor metabolism, suggesting that CAs may be a potential target for the treatment of cancers. We have recently revealed a novel function of CA IX in ferroptosis-resistance by using human malignant mesothelioma cells. Herein, we aim to review the potential molecular association between ferroptosis and CAs, from the viewpoint of iron-metabolism, lipogenesis and signaling pathways both under physiological and pathological contexts.

Overexpression of Tie2 is associated with poor prognosis in patients with gastric cancer

Tunica Interna endothelial cell kinase (Tie2)-expressing macrophages (TEMs) are a subgroup of tumor-associated macrophages that are associated with a poor prognosis in numerous types of cancer. The present study aimed to assess the prognostic impact of Tie2 expression in gastric cancer tissues. Between January 2009 and December 2009, 76 newly diagnosed patients with gastric cancer at the Southwest Hospital, Third Military Medical University (Chongqing, China) were enrolled. TEMs were detected using immunohistochemistry. Tie2, cluster of differentiation (CD)68 and carbonic anhydrase IX (CAIX) were analyzed using immunohistochemistry and immunofluorescent microscopy. Tie2 protein expression was analyzed using western blot analysis in hypoxic and normoxic gastric cancer tissues. The number of TEMs positively staining for Tie2 increased with the tumor-node-metastasis (TNM) stage: 0, 53.9, 75.6 and 100% in stages I, II, III and IV, respectively (P<0.001). Tumor size and lymph node involvement were significantly associated with the presence of Tie2 in the tumor stroma (P<0.001). There was no significant difference between Tie2 and CAIX, irrespective of how the patients were grouped (tumor size, lymph node involvement, TNM stage or histological grade). Tie2 protein expression was increased in the hypoxic regions of gastric tumors.Tie2 and CD68 expression colocalized in hypoxic and normoxic gastric cancer tissues. The 1-, 2- and 3-year recurrence rates of the TEM-positive group were 31.4, 56.9 and 66.7%, respectively, as compared with 8, 28 and 48%, respectively, for the TEM-negative group (P<0.05). In the TEM-negative group, 2 patients succumbed to the disease, as compared with 21 patients in the TEM-positive group (P<0.05). Therefore, high quantities of TEMs, represented by Tie2 expression, in gastric tumors may be associated with poor survival.

A Versatile Carbonic Anhydrase IX Targeting Ligand-Functionalized Porous Silicon Nanoplatform for Dual Hypoxia Cancer Therapy and Imaging

Hypoxia occurs in most solid tumors, and it has been shown to be an independent prognostic indicator of a poor clinical outcome for patients with various cancers. Therefore, constructing a nanosystem specifically targeting cancer cells under hypoxia conditions is a promising approach for cancer therapy. Herein, we develop a porous silicon (PSi)-based nanosystem for targeted cancer therapy. VD11-4-2, a novel inhibitor for carbonic anhydrase IX (CA IX), is anchored on PSi particles (VD-PSi). As CA IX is mainly expressed on the cancer cell membrane under hypoxia condition, this nanocomplex inherits a strong affinity toward hypoxic human breast adenocarcinoma (MCF-7) cells; thus, a better killing efficiency for the hypoxia-induced drug resistance cancer cell is observed. Furthermore, the release of doxorubicin (DOX) from VD-PSi showed pH dependence, which is possibly due to the hydrogen-bonding interaction between DOX and VD11-4-2. The fluorescence resonance energy transfer effect between DOX and VD11-4-2 is observed and applied for monitoring the DOX release intracellularly. Protein inhibition and binding assays showed that VD-PSi binds and inhibits CA IX. Overall, we developed a novel nanosystem inheriting several advantageous properties, which has great potential for targeted treatment of cancer cells under hypoxic conditions.

Hypoxia-Inducible Factors (HIFs) and Phosphorylation: Impact on Stability, Localization, and Transactivity

The hypoxia-inducible factor α-subunits (HIFα) are key transcription factors in the mammalian response to oxygen deficiency. The HIFα regulation in response to hypoxia occurs primarily on the level of protein stability due to posttranslational hydroxylation and proteasomal degradation. However, HIF α-subunits also respond to various growth factors, hormones, or cytokines under normoxia indicating involvement of different kinase pathways in their regulation. Because these proteins participate in angiogenesis, glycolysis, programmed cell death, cancer, and ischemia, HIFα regulating kinases are attractive therapeutic targets. Although numerous kinases were reported to regulate HIFα indirectly, direct phosphorylation of HIFα affects HIFα stability, nuclear localization, and transactivity. Herein, we review the role of phosphorylation-dependent HIFα regulation with emphasis on protein stability, subcellular localization, and transactivation.

Differential expression of HO-1 and CYP1A2 during up-regulation of ERK in stressed fish hepatocytes

Induction of heme oxygenase-1 (HO-1) and extracellular signal-regulated kinase (ERK) is a crucial step in the cellular response to oxidative stress. Altered expression of such proteins in response to stress conditions is a key factor for the maintenance of cellular integrity and survival. Hypoxia-inducible factor-1 (HIF-1) and cytochrome P450 1A (CYP1A) are critical indicators of environmental exposure to hypoxia. The current study was aimed to analyse the expression pattern of HO-1, p-ERK, HIF-1α and CYP1A2 in hepatocytes of Mugil cephalus inhabiting Kovalam (unpolluted site) and Ennore (polluted site) estuaries. The impact of stress on hepatocytes was assessed by measuring the level of lipid hydroperoxides (LHP) and reduced glutathione (GSH) in hepatocytes of M. cephalus inhabiting these estuaries. The expression of HO-1, p-ERK, HIF-1α and CYP1A2 was analysed by ELISA and immunoblot analysis, respectively. There was significant decrease of GSH (19%) and CYP1A2 (34%) along with significant increase of LHP (31%), HO-1 (96%), p-ERK (p < 0.01) and HIF-1α (41%) in hepatocytes of M. cephalus inhabiting Ennore estuary than Kovalam estuary. The present study shows that increased synthesis of HO-1 mainly regulated by p-ERK and HIF-1α may significantly contribute to the environmental adaptation processes of grey mullet, by protecting the cells from oxidative stress and stress-induced degenerative changes.

Combination of carbonic anhydrase inhibitor, acetazolamide, and sulforaphane, reduces the viability and growth of bronchial carcinoid cell lines

Background

Bronchial carcinoids are pulmonary neuroendocrine cell-derived tumors comprising typical (TC) and atypical (AC) malignant phenotypes. The 5-year survival rate in metastatic carcinoid, despite multiple current therapies, is 14-25%. Hence, we are testing novel therapies that can affect the proliferation and survival of bronchial carcinoids.

Methods

In vitro studies were used for the dose–response (AlamarBlue) effects of acetazolamide (AZ) and sulforaphane (SFN) on clonogenicity, serotonin-induced growth effect and serotonin content (LC-MS) on H-727 (TC) and H-720 (AC) bronchial carcinoid cell lines and their derived NOD/SCID mice subcutaneous xenografts. Tumor ultra structure was studied by electron microscopy. Invasive fraction of the tumors was determined by matrigel invasion assay. Immunohistochemistry was conducted to study the effect of treatment(s) on proliferation (Ki67, phospho histone-H3) and neuroendocrine phenotype (chromogranin-A, tryptophan hydroxylase).

Results

Both compounds significantly reduced cell viability and colony formation in a dose-dependent manner (0–80 μM, 48 hours and 7 days) in H-727 and H-720 cell lines. Treatment of H-727 and H-720 subcutaneous xenografts in NOD/SCID mice with the combination of AZ + SFN for two weeks demonstrated highly significant growth inhibition and reduction of 5-HT content and reduced the invasive capacity of H-727 tumor cells. In terms of the tumor ultra structure, a marked reduction in secretory vesicles correlated with the decrease in 5-HT content.

Conclusions

The combination of AZ and SFN was more effective than either single agent. Since the effective doses are well within clinical range and bioavailability, our results suggest a potential new therapeutic strategy for the treatment of bronchial carcinoids.

Carbonic anhydrase IX as a specific biomarker for clear cell renal cell carcinoma: comparative study of Western blot and immunohistochemistry and implications for diagnosis

OBJECTIVE

This study aimed to evaluate the usefulness of carbonic anhydrase IX (CA-IX) expression in clear cell renal cell carcinoma (CCRCC) using two different techniques to detect protein expression.

MATERIAL AND METHODS

An experimental, cross-sectional, analytical study was conducted to analyse proteins in renal tumour and healthy tissue specimens from 38 consecutive patients who underwent nephrectomy for renal cancer. CA-IX protein expression was measured by immunohistochemistry and Western blot analysis and quantified. Statistical analysis was performed with the positive and negative specific agreements and kappa coefficient. The sensitivity and specificity of both techniques were assessed. Statistical tests were conducted to analyse the association between CA-IX expression quantitation and normal prognosis factors (TNM stage and Fuhrman nuclear grade), only in CCRCC.

RESULTS

The mean patient age was 65 years, 78.9% of patients were men and 57.9% of tumours were CCRCC. CA-IX protein expression was positive in 63.2% of tumours by immunohistochemistry and in 60.5% by Western blot. Both techniques detected CA-IX expression only in CCRCC and unclassifiable tumours. High concordance indices were observed for CCRCC diagnosis. Western blot and immunohistochemistry had a sensitivity of 95.5% and 100%, respectively; the specificity was 100% in both techniques. CA-IX expression quantitation did not correlate with tumour stage or Fuhrman nuclear grade.

CONCLUSIONS

Immunochemistry and Western blot techniques can be used to detect abnormal CA-IX protein expression in CCRCC and to support morphology-based diagnostic techniques.

Tumour hypoxia induces a metabolic shift causing acidosis: a common feature in cancer

Maintenance of cellular pH homeostasis is fundamental to life. A number of key intracellular pH (pHi) regulating systems including the Na⁺/H⁺ exchangers, the proton pump, the monocarboxylate transporters, the HCO₃⁻ transporters and exchangers and the membrane-associated and cytosolic carbonic anhydrases cooperate in maintaining a pHi that is permissive for cell survival. A common feature of tumours is acidosis caused by hypoxia (low oxygen tension). In addition to oncogene activation and transformation, hypoxia is responsible for inducing acidosis through a shift in cellular metabolism that generates a high acid load in the tumour microenvironment. However, hypoxia and oncogene activation also allow cells to adapt to the potentially toxic effects of an excess in acidosis. Hypoxia does so by inducing the activity of a transcription factor the hypoxia-inducible factor (HIF), and particularly HIF-1, that in turn enhances the expression of a number of pHi-regulating systems that cope with acidosis. In this review, we will focus on the characterization and function of some of the hypoxia-inducible pH-regulating systems and their induction by hypoxic stress. It is essential to understand the fundamentals of pH regulation to meet the challenge consisting in targeting tumour metabolism and acidosis as an anti-tumour approach. We will summarize strategies that take advantage of intracellular and extracellular pH regulation to target the primary tumour and metastatic growth, and to turn around resistance to chemotherapy and radiotherapy.

Regulatory role of HIF-1alpha in the pathogenesis of age-related macular degeneration (AMD)

Age-related macular degeneration (AMD) is a leading cause of irreversible blindness in the elderly throughout the world. AMD is attributed to a complex interaction of genetic and environmental factors. It is characterized by degeneration involving the retinal photoreceptors, retinal pigment epithelium (RPE), and Bruch's membrane, as well as alterations in choroidal capillaries. Aging and age-associated degenerative diseases, such as AMD, are intimately associated with decreased levels of tissue oxygenation and hypoxia that may induce accumulation of detrimental RPE-associated deposits, inflammation and neovascularization processes in retina. Hypoxia-inducible factor (HIF) is the master regulator for hypoxia-induced cellular adaptation that is involved in NF-kappaB signaling and the autophagic protein clearance system. In this review, we discuss role of HIF in AMD pathology and as a possible therapeutic target.

Hypoxia-induced expression of carbonic anhydrase 9 is dependent on the unfolded protein response

Adaptation to tumor hypoxia is mediated in large part by changes in protein expression. These are driven by multiple pathways, including activation of the hypoxia inducible factor-1 (HIF-1) transcription factor and the PKR-like endoplasmic reticulum kinase PERK, a component of the unfolded protein response. Through gene expression profiling we discovered that induction of the HIF-1 target gene CA9 was defective in mouse embryo fibroblasts derived from mice harboring an eIF2alpha S51A knock-in mutation. This finding was confirmed in two isogenic human cell lines with an engineered defect in eIF2alpha phosphorylation. We show that impaired CA9 expression was not due to changes in HIF activity or CA9 mRNA stability. Using chromatin immunoprecipitation we show that the eIF2alpha-dependent translationally regulated gene ATF4 binds directly to the CA9 promoter and is associated with loss of the transcriptional repressive histone 3 lysine 27 tri-methylation mark. Loss or overexpression of ATF4 confirmed its role in CA9 induction during hypoxia. Our data indicate that expression of CA9 is regulated through both the HIF-1 and unfolded protein response hypoxia response pathways in vitro and in vivo.

Role of aryl hydrocarbon receptor in modulation of the expression of the hypoxia marker carbonic anhydrase IX

Tumour-associated expression of CA IX (carbonic anhydrase IX) is to a major extent regulated by HIF-1 (hypoxia-inducible factor-1) which is important for transcriptional activation and consists of the oxygen-regulated subunit HIF-1alpha and the partner factor ARNT [AhR (aryl hydrocarbon receptor) nuclear translocator]. We have previously observed that HIF-1alpha competes with the AhR for interaction with ARNT under conditions when both conditionally regulated factors are activated. We have therefore investigated whether TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin)-induced activation of the AhR pathway might interfere with CA IX expression. The results from the present study suggest that TCDD treatment reduces hypoxic induction of both CA IX mRNA and protein expression. Moreover, the transcriptional activity of the CA9 promoter was significantly reduced by expression of CAAhR (constitutively active AhR), which activates transcription in a ligand-independent manner. Finally, we found that ARNT is critical for both hypoxic induction and the TCDD-mediated inhibition of CA9 expression.

PI3K/Akt activity has variable cell-specific effects on expression of HIF target genes, CA9 and VEGF, in human cancer cell lines

The phosphatidylinositol 3-kinase/Akt (PI3K) pathway regulates hypoxia-inducible factor (HIF) activity. Higher expression of HIF-1alpha and carbonic anhydrase IX (CAIX), a hypoxia-inducible gene, in HT10806TG fibrosarcoma cells (mutant N-ras allele), compared to derivative MCH603 cells (deleted mutant N-ras allele), correlated with increased PI3K activity. Constitutive activation of the PI3K pathway in MCH603/PI3K(act) cells increased HIF-1alpha but, surprisingly, decreased CAIX levels. The cell-type specific inhibitory effect on CAIX was confirmed at the transcriptional level whereas epigenetic modifications of CA9 were ruled out. In summary, our data do not substantiate the generalization that PI3K upregulation leads to increased HIF activity.

Transcriptional control of the tumor- and hypoxia-marker carbonic anhydrase 9: A one transcription factor (HIF-1) show?

Transcriptional activation by hypoxia is mediated by the hypoxia-inducible factor (HIF) via binding to the hypoxia-responsive element (HRE). Hypoxia in solid tumors associates with poorer outcome of the disease and reliable cellular markers of tumor hypoxia would represent a valuable diagnostic marker and a potential therapeutic target. In this category, carbonic anhydrase IX (CAIX) is one of the most promising candidates. Here, we summarize the knowledge about transcriptional regulation of CA9. The HRE is the central regulatory element in the CA9 promoter, whereas other elements are limited to lesser roles of amplification of signals received at the HRE. The analysis of known mechanisms of activation of CA9 reveals the prominent role of the HIF-1 pathway. Experimental paradigms with uncoupled HIF-1alpha stability and transcriptional activity (pericellular hypoxia, proteasomal inhibitor) provide evidence that CA9 expression monitors transcriptional activity of HIF-1, rather than the abundance of HIF-1alpha. Furthermore, these paradigms could provide a corollary to some of the apparently discordant cases (CAIX+, HIF-1alpha-) or (CAIX-, HIF-1alpha+) observed in vivo. In conclusion, the existing data support the notion that CA9, due to the unique structure of its promoter, is one of the most sensitive endogenous sensors of HIF-1 activity.

Activation of HIF-1alpha in exponentially growing cells via hypoxic stimulation is independent of the Akt/mTOR pathway

Accumulation of HIF-1alpha during normoxic conditions at high cell density has previously been shown to occur and can be used to stabilize HIF-1alpha protein in the absence of a specific anaerobic chamber. However, the impact and origin of this pool of HIF-1alpha, obtained under normoxia, has been underestimated. In this study, we have systematically compared the related pools of HIF-1alpha stabilized in normoxia by high cell density to those obtained at low density in hypoxia. At first glance, these two stimuli appear to have similar outcomes: HIF-1alpha stabilization and induction of HIF-1-dependent genes. However, upon careful analysis, we observed that molecular mechanisms involved are different. We clearly demonstrate that density-dependant HIF-1alpha accumulation during normoxia is due to the cells high consumption of oxygen, as demonstrated by using a respiration inhibitor (oligomycin) and respiratory-defective mutant cells (GSK3). Finally and most importantly, our data indicate that a decrease in AKT activity followed by a total decrease in p70(S6K) phosphorylation reflecting a decrease in mTOR activity occurs during high oxygen consumption, resulting from high cell density. In contrast, hypoxia, even at severe low O(2) levels, only slightly impacts upon the mTOR pathway under low cell density conditions. Thus, activation of HIF-1alpha in exponentially growing cells via hypoxic stimulation is independent of the Akt/mTOR pathway whereas HIF-1alpha activation obtained in high confluency is totally dependent on mTOR pathway as rapamycin totally impaired (i) HIF-1alpha stabilization and (ii) mRNA levels of CA9 and BNIP3, two HIF-target genes.

Cyclooxygenase-2/carbonic anhydrase-IX up-regulation promotes invasive potential and hypoxia survival in colorectal cancer cells

Inflammation promotes colorectal carcinogenesis. Tumour growth often generates a hypoxic environment in the inner tumour mass. We here report that, in colon cancer cells, the expression of the pro-inflammatory enzyme cyclooxygenase-2 (COX-2) associates with that of the hypoxia response gene carbonic anhydrase-IX (CA-IX). The COX-2 knockdown, achieved by the stable infection of a COX-2 specific short harpin RNA interference (shCOX-2), down-regulates CA-IX gene expression. In colorectal cancer (CRC) cells, PGE₂, the main COX-2 gene products, promotes CA-IX gene expression by ERK1/2 activation. In normoxic environment, shCOX-2 infected/CA-IX siRNA transfected CRC cells show a reduced level of active metalloproteinase-2 (MMP-2) that associates with a decreased extracellular matrix invasion capacity. In presence of hypoxia, COX-2 gene expression and PGE₂ production increase. The knockdown of COX-2/CA-IX blunts the survival capability of CRC cells in hypoxia. At a high cell density, a culture condition that creates a mild pericellular hypoxic environment, the expression of COX-2/CA-IX genes is increased and triggers the invasive potential of colon cancer cells. In human colon cancer tissues, COX-2/CA-IX protein expression levels, assessed by Western blot and immunohistochemistry, correlate each other and increase with tumour stage. In conclusion, these data indicate that COX-2/CA-IX interplay promotes the aggressive behaviour of CRC cells.

Regulation of gene expression by hypoxia: integration of the HIF-transduced hypoxic signal at the hypoxia-responsive element

Cells experiencing lowered O(2) levels (hypoxia) undergo a variety of biological responses in order to adapt to these unfavorable conditions. The master switch, orchestrating the cellular response to low O(2) levels, is the transcription factor, termed hypoxia-inducible factor (HIF). The alpha subunits of HIF are regulated by 2-oxoglutarate-dependent oxygenases that, in the presence of O(2), hydroxylate specific prolyl and asparaginyl residues of HIF-alpha, inducing its proteasome-dependent degradation and repression of transcriptional activity, respectively. Hypoxia inhibits oxygenases, stabilized HIF-alpha translocates to the nucleus, dimerizes with HIF-beta, recruits the coactivators p300/CBP, and induces expression of its transcriptional targets via binding to hypoxia-responsive elements (HREs). HREs are composite regulatory elements, comprising a conserved HIF-binding sequence and a highly variable flanking sequence that modulates the transcriptional response. In summary, the transcriptional response of a cell is the end product of two major functions. The first (trans-acting) is the level of activation of the HIF pathway that depends on regulation of stability and transcriptional activity of the HIF-alpha. The second (cis-acting) comprises the characteristics of endogenous HREs that are determined by the availability of transcription factors cooperating with HIF and/or individual HIF-alpha isoforms.

Hypoxia up-regulates hypoxia-inducible factor-1alpha transcription by involving phosphatidylinositol 3-kinase and nuclear factor kappaB in pulmonary artery smooth muscle cells

The oxygen sensitive alpha-subunit of the hypoxia-inducible factor-1 (HIF-1) is a major trigger of the cellular response to hypoxia. Although the posttranslational regulation of HIF-1alpha by hypoxia is well known, its transcriptional regulation by hypoxia is still under debate. We, therefore, investigated the regulation of HIF-1alpha mRNA in response to hypoxia in pulmonary artery smooth muscle cells. Hypoxia rapidly enhanced HIF-1alpha mRNA levels and HIF-1alpha promoter activity. Furthermore, inhibition of the phosphatidylinositol 3-kinase (PI3K)/AKT but not extracellular signal-regulated kinase 1/2 pathway blocked the hypoxia-dependent induction of HIF-1alpha mRNA and HIF-1alpha promoter activity, suggesting involvement of a PI3K/AKT-regulated transcription factor. Interestingly, hypoxia also induced nuclear factor-kappaB (NFkappaB) nuclear translocation and activity. In line, expression of the NFkappaB subunits p50 and p65 enhanced HIF-1alpha mRNA levels, whereas blocking of NFkappaB by an inhibitor of nuclear factor-kappaB attenuated HIF-1alpha mRNA induction by hypoxia. Reporter gene assays revealed the presence of an NFkappaB site within the HIF-1alpha promoter, and mutation of this site abolished induction by hypoxia. In line, gel shift analysis and chromatin immunoprecipitation confirmed binding of p50 and p65 NFkappaB subunits to the HIF-1alpha promoter under hypoxia. Together, these findings provide a novel mechanism in which hypoxia induces HIF-1alpha mRNA expression via the PI3K/AKT pathway and activation of NFkappaB.

The role of hypoxia inducible factor-1 in cell metabolism--a possible target in cancer therapy

In many cancer types, intratumoural hypoxia is linked to increased expression and activity of the transcription factor hypoxia-inducible factor (HIF-1alpha), which is associated with poor patient prognosis. This increased the interest in HIF-1alpha as a cancer drug target. Further, HIF-1alpha has also a central role in the adaptive cellular programme responding to hypoxia in normal tissues. Many of the HIF-1alpha-regulated genes encode enzymes of metabolic pathways. Therefore, studying the link and the feedback mechanisms between metabolism and HIF-1alpha is of major importance to find new and specific therapeutic strategies.

p66Shc/Notch-3 interplay controls self-renewal and hypoxia survival in human stem/progenitor cells of the mammary gland expanded in vitro as mammospheres

The comprehension of the basic biology of stem cells is expected to provide a useful insight into the pathogenesis of cancer. In particular, there is evidence that hypoxia promotes stem cell renewal in vitro as well as in vivo. It therefore seems reasonable that stem cell survival and hypoxia response are strictly connected at molecular level. We here report that the 66-kDa isoform of the SHC gene (p66Shc) is induced in a breast cancer cell line by the exposure to hypoxic environment and that it controls the expression of the stem cell regulatory gene Notch-3. Then, we show that p66Shc/Notch-3 interplay modulates self-renewal (by inducing the Notch-ligand Jagged-1) and hypoxia survival (by inducing the hypoxia-survival gene carbonic anhydrase IX) in mammary gland stem/progenitor cells, expanded in vitro as multicellular spheroids (mammospheres). We conclude that mechanisms that regulate stem cell renewal and hypoxia survival are integrated at the level of the p66Shc/Notch3 interplay. Because Notch-3, Jagged-1, and carbonic anhydrase IX are dysregulated in breast cancer, and because p66Shc is an aging-regulating gene, we envision that these data may help in understanding the relationship among aging, cancer, and stem cells.