A Hypoxia-Independent Hypoxia-Inducible Factor-1 Activation Pathway Induced by Phosphatidylinositol-3 Kinase/Akt in HER2 Overexpressing Cells

HER2 Alterations in Non-Small Cell Lung Cancer: Biologico-Clinical Consequences and Interest in Therapeutic Strategies

Lung cancer stands as the first cause of death by cancer in the world. Despite the improvement in patients' outcomes in the past decades through the development of personalized medicine approaches, a substantial portion of patients remains ineligible for targeted therapies due to the lack of a "druggable" molecular target. HER2, a receptor tyrosine kinase member of the EGFR/ErbB family, is known to show oncogenic properties. In this review, we focus on the different HER2 dysregulation mechanisms that have been observed in non-small cell lung cancer (NSCLC): gene mutation, gene amplification, protein overexpression and protein hyper-phosphorylation, the latter suggesting that HER2 dysregulation can occur independently of any molecular aberration. These HER2 alterations inevitably have consequences on tumor biology. Here, we discuss how they are not only involved in abnormal proliferation and survival of cancer cells but also potentially in increased angiogenic properties, mesenchymal features and tumor immune escape. Finally, we review the impact of these HER2 alterations in various therapeutic approaches. While standard chemotherapy and groundbreaking immunotherapy seem rather ineffective for HER2-altered NSCLCs, the development of HER2-targeted therapies such as tyrosine kinase inhibitors, anti-HER2 antibodies and especially antibody-drug conjugates could provide new hopes for patients.

PET/MRI of hypoxia and vascular function in ER-positive breast cancer: correlations with immunohistochemistry

OBJECTIVES

To explore the relationship between indices of hypoxia and vascular function from 18F-fluoromisonidazole ([18F]-FMISO)-PET/MRI with immunohistochemical markers of hypoxia and vascularity in oestrogen receptor-positive (ER +) breast cancer.

METHODS

Women aged  > 18 years with biopsy-confirmed, treatment-naïve primary ER + breast cancer underwent [18F]-FMISO-PET/MRI prior to surgery. Parameters of vascular function were derived from DCE-MRI using the extended Tofts model, whilst hypoxia was assessed using the [18F]-FMISO influx rate constant, Ki. Histological tumour sections were stained with CD31, hypoxia-inducible factor (HIF)-1α, and carbonic anhydrase IX (CAIX). The number of tumour microvessels, median vessel diameter, and microvessel density (MVD) were obtained from CD31 immunohistochemistry. HIF-1α and CAIX expression were assessed using histoscores obtained by multiplying the percentage of positive cells stained by the staining intensity. Regression analysis was used to study associations between imaging and immunohistochemistry variables.

RESULTS

Of the lesions examined, 14/22 (64%) were ductal cancers, grade 2 or 3 (19/22; 86%), with 17/22 (77%) HER2-negative. [18F]-FMISO Ki associated negatively with vessel diameter (p = 0.03), MVD (p = 0.02), and CAIX expression (p = 0.002), whilst no significant relationships were found between DCE-MRI pharmacokinetic parameters and immunohistochemical variables. HIF-1α did not significantly associate with any PET/MR imaging indices.

CONCLUSION

Hypoxia measured by [18F]-FMISO-PET was associated with increased CAIX expression, low MVD, and smaller vessel diameters in ER + breast cancer, further corroborating the link between inadequate vascularity and hypoxia in ER + breast cancer.

KEY POINTS

• Hypoxia, measured by [18F]-FMISO-PET, was associated with low microvessel density and small vessel diameters, corroborating the link between inadequate vascularity and hypoxia in ER + breast cancer. • Increased CAIX expression was associated with higher levels of hypoxia measured by [18F]-FMISO-PET. • Morphologic and functional abnormalities of the tumour microvasculature are the major determinants of hypoxia in cancers and support the previously reported perfusion-driven character of hypoxia in breast carcinomas.

An antioxidant ameliorates allergic airway inflammation by inhibiting HDAC 1 via HIF-1α/VEGF axis suppression in mice

Histone deacetylase inhibitors (HDACi) are novel class of drugs as they are involved in post translational modification of several proteins involved in signaling pathways related to asthma. HDACi have been reported to elicit protective effects on asthma but the signaling pathways associated with it have not been investigated much. Recently, we have demonstrated that intranasal administrations of Pan-HDAC inhibitors, sodium butyrate and curcumin, which have effectively reduced asthma severity via HDAC1 inhibition in Ovalbumin induced mouse model. Present study aimed to investigate possible pathways by which curcumin and sodium butyrate may minimize asthma pathogenesis via HDAC 1 inhibition. Balb/c mice were exposed (sensitized and challenged) with Ovalbumin to establish allergic asthma model followed by pretreatment of curcumin (5 mg/kg) and sodium butyrate (50 mg/kg) through intranasal route. Effects of curcumin and sodium butyrate on HIF-1α/VEGF signaling through activation of PI3K/Akt axis has been investigated using protein expressions followed by chromatin immunoprecipitation of BCL2 and CCL2 against HDAC1. Molecular docking analysis was also performed to investigate effects of curcumin and butyrate on mucus hypersecretion, goblet cell hyperplasia and airway hyperresponsiveness. Augmented expressions of HDAC-1, HIF-1α, VEGF, p-Akt and p-PI3K were observed in asthmatic group which was suppressed in both the treatments. NRF-2 level was significantly restored by curcumin and butyrate treatments. Protein expressions of p-p38, IL-5 and mRNA expressions of GATA-3 were also reduced in curcumin and butyrate treatment groups. Our findings suggest that curcumin and sodium butyrate may attenuate airway inflammation via down regulation of p-Akt/p-PI3K/HIF-1α/VEGF axis.

HIF-1 signaling: an emerging mechanism for mitochondrial dynamics

A growing emphasis has been paid to the function of mitochondria in tumors, neurodegenerative disorders (NDs), and cardiovascular diseases. Mitochondria are oxygen-sensitive organelles whose function depends on their structural basis. Mitochondrial dynamics are critical in regulating the structure. Mitochondrial dynamics include fission, fusion, motility, cristae remodeling, and mitophagy. These processes could alter mitochondrial morphology, number, as well as distribution, to regulate complicated cellular signaling processes like metabolism. Meanwhile, they also could modulate cell proliferation and apoptosis. The initiation and progression of several diseases, such as tumors, NDs, cardiovascular disease, were all interrelated with mitochondrial dynamics. HIF-1 is a nuclear protein presented as heterodimers, and its transcriptional activity is triggered by hypoxia. It plays an important role in numerous physiological processes including the development of cardiovascular system, immune system, and cartilage. Additionally, it could evoke compensatory responses in cells during hypoxia through upstream and downstream signaling networks. Moreover, the alteration of oxygen level is a pivotal factor to promote mitochondrial dynamics and HIF-1 activation. HIF-1α might be a promising target for modulating mitochondrial dynamics to develop therapeutic approaches for NDs, immunological diseases, and other related diseases. Here, we reviewed the research progress of mitochondrial dynamics and the potential regulatory mechanism of HIF-1 in mitochondrial dynamics.

Mammalian orthoreovirus infection in human epidermal growth factor receptor 2 positive (HER2+) breast cancer cells

Mammalian orthoreovirus (MRV) is a clinically benign oncolytic virus which has been investigated for use in multiple cancer types, including breast cancer (BC). In human clinical trials, MRV has been shown to be safe, and multiple BC patients have shown partial responses to intratumoral and intravenous virus delivery. Combination therapies inclusive of MRV and current FDA approved BC chemotherapies are being investigated to target metastatic, early BC, and triple negative BC. Though MRV is being tested clinically, we still do not fully understand the highly variable patient responses to MRV therapy. One of the most aggressive BC subtypes is HER2+ BC, in which human epidermal growth factor receptor 2 (HER2) is dysregulated, resulting in increased growth, survival, and metastasis of cancer cells. FDA approved therapies, trastuzumab and pertuzumab, target HER2 to prevent signaling of the phosphoinositide 3-kinase (PI3K) pathway. However, recent findings show that accumulation of hypoxia inducible factor-1 alpha (HIF-1α) in HER2+ BC cells contributes to trastuzumab resistance. In this work, we provide evidence that MRV infects, replicates in, and kills HER2 overexpressing cells. MRV infection is also found to have variable effects on signaling pathways that activate or are activated by HER2 expression. Finally, we show that MRV reduces HIF-1α accumulation in all the cell lines tested, including a HER2+ BC cell line. These studies provide further evidence that MRV holds promise for use in conjunction with trastuzumab to treat HER2+ BC patients.

3D Models as a Tool to Assess the Anti-Tumor Efficacy of Therapeutic Antibodies: Advantages and Limitations

Therapeutic monoclonal antibodies (mAbs) are an emerging and very active frontier in clinical oncology, with hundred molecules currently in use or being tested. These treatments have already revolutionized clinical outcomes in both solid and hematological malignancies. However, identifying patients who are most likely to benefit from mAbs treatment is currently challenging and limiting the impact of such therapies. To overcome this issue, and to fulfill the expectations of mAbs therapies, it is urgently required to develop proper culture models capable of faithfully reproducing the interactions between tumor and its surrounding native microenvironment (TME). Three-dimensional (3D) models which allow the assessment of the impact of drugs on tumors within its TME in a patient-specific context are promising avenues to progressively fill the gap between conventional 2D cultures and animal models, substantially contributing to the achievement of personalized medicine. This review aims to give a brief overview of the currently available 3D models, together with their specific exploitation for therapeutic mAbs testing, underlying advantages and current limitations to a broader use in preclinical oncology.

Hypoxia-mediated drug resistance in breast cancers

Tissue hypoxia in solid tumors is caused by several pathological changes associated with tumor growth, including altered microvasculature structure, increased diffusional distances, and tumor-associated anemia. As the oxygen tension decreases, tumor cells adapt to the limited oxygen supply. Previous studies have shown that such adaptation leads to an aggressive phenotype that is resistant to many anti-cancer therapies. Induction of hypoxia inducible factors (HIFs) mediates many proteomic and genomic changes associated with tumor hypoxia. In breast cancers, HIFs not only predict poor prognosis, but also promote metastasis and drug resistance. Several studies have proposed HIF-1α as a druggable target in drug-resistant breast cancers, leading to the synthesis and development of small molecule inhibitors. Disappointingly, however, none of these small molecule inhibitors have progressed to clinical use. In this review, we briefly discuss the role of HIF-1α in breast cancer drug resistance and summarize the current and future approaches to targeting this transcription factor in breast cancer treatment.

CDK5RAP3 inhibits angiogenesis in gastric neuroendocrine carcinoma by modulating AKT/HIF-1α/VEGFA signaling

Background

Angiogenesis plays critical roles in the progression and metastasis of malignant tumors. Gastric neuroendocrine carcinoma is an uncommon stomach cancer that is rich in blood vessels and exhibits highly malignant biological behavior with a poor prognosis. The role of CDK5RAP3 in GNEC has not been reported to date.

Methods

Immunohistochemistry was used to assess the expression of CDK5RAP3 in GNEC tissues and adjacent non-tumor tissues. Cell lines with stable overexpression or knockdown of CDK5RAP3 were constructed using lentiviral transfection. Wound-healing assays, invasion and metastasis assays, tube formation assays, and tumor xenograft transplantation assays were performed to evaluate the effect of CDK5RAP3 on GNEC angiogenesis in vitro and in vivo. Real-time PCR, ELISA, western blot analysis, and confocal-immunofluorescence staining were used to explore the molecular mechanism of CDK5RAP3′s effect on angiogenesis.

Results

Compared with their respective adjacent non-tumor tissues, protein levels of CDK5RAP3 were significantly decreased in GNEC tissues. Furthermore, low expression of CDK5RAP3 was correlated with more advanced TNM stage, increased tumor microvessel density, and poor prognosis. Functionally, we found that GNEC cells with CDK5RAP3 knockdown promoted human umbilical vein endothelial cells migration and tube formation via activation of AKT/HIF-1α/VEGFA signaling, resulting in increased levels of VEGFA in GNEC cell supernatant. In addition, CDK5RAP3 overexpression in GNEC cells caused the opposing effect. Consistent with these results, nude mouse tumorigenicity assays showed that CDK5RAP3 expression downregulated angiogenesis in vivo. Lastly, patients with low CDK5RAP3 expression and high VEGFA expression exhibited the worst prognosis.

Conclusions

This study demonstrated that CDK5RAP3 inhibits angiogenesis by downregulating AKT/HIF-1α/VEGFA signaling in GNEC and improves patient prognosis, suggesting that CDK5RAP3 could be a potential therapeutic target for GNEC.

HER2 regulates HIF-2α and drives an increased hypoxic response in breast cancer

Background

Tumour hypoxia is a driver of breast cancer progression associated with worse prognosis and more aggressive disease. The cellular response to hypoxia is mediated by the hypoxia-inducible transcription factors HIF-1 and HIF-2, whose transcriptional activity is canonically regulated through their oxygen-labile HIF-α subunits. These are constitutively degraded in the presence of oxygen; however, HIF-1α can be stabilised, even at high oxygen concentrations, through the activation of HER receptor signalling. Despite this, there is still limited understanding on how HER receptor signalling interacts with HIF activity to contribute to breast cancer progression in the context of tumour hypoxia.

Methods

2D and 3D cell line models were used alongside microarray gene expression analysis and meta-analysis of publicly available gene expression datasets to assess the impact of HER2 overexpression on HIF-1α/HIF-2α regulation and to compare the global transcriptomic response to acute and chronic hypoxia in an isogenic cell line model of HER2 overexpression.

Results

HER2 overexpression in MCF7 cells leads to an increase in HIF-2α but not HIF-1α expression in normoxia and an increased upregulation of HIF-2α in hypoxia. Global gene expression analysis showed that HER2 overexpression in these cells promotes an exaggerated transcriptional response to both short-term and long-term hypoxia, with increased expression of numerous hypoxia response genes. HIF-2α expression is frequently higher in HER2-overexpressing tumours and is associated with worse disease-specific survival in HER2-positive breast cancer patients. HER2-overexpressing cell lines demonstrate an increased sensitivity to targeted HIF-2α inhibition through either siRNA or the use of a small molecule inhibitor of HIF-2α translation.

Conclusions

This study suggests an important interplay between HER2 expression and HIF-2α in breast cancer and highlights the potential for HER2 to drive the expression of numerous hypoxia response genes in normoxia and hypoxia. Overall, these findings show the importance of understanding the regulation of HIF activity in a variety of breast cancer subtypes and points to the potential of targeting HIF-2α as a therapy for HER2-positive breast cancer.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1097-0) contains supplementary material, which is available to authorized users.

Deficiency of HIF-1α in myeloid cells protects Escherichia coli or LPS-induced acute lung injury

BACKGROUND

Deficiency of hypoxia-induced factor-1α (HIF-1α) in macrophages reduced lipopolysaccharide (LPS)-induced mortality; however, whether HIF-1α expression in myeloid cells would contribute to the development of Escherichia coli (E. coli) or LPS-induced acute lung injury (ALI) is less investigated.

AIM

To test whether deletion of Hif1α in myeloid cells affects E. coli or LPS-induced ALI and to elicit the underlying mechanisms.

DESIGN

Laboratory study.

METHODS

We intratracheally challenged Hif1αfl/fl and Hif1αfl/flLysMCre mice with E. coli or LPS to analyze lung and spleen inflammatory responses. Flow cytometry was used to analyze the changes of α7 nAChR+CD11b+ cells in the lung and spleen. Double knockout of Chrna7 and Itgam mice were used to examine expression of HIF-1α during E. coli lung infection. Vagotomy was performed to demonstrate the role of vagus nerve in mediating protective effects of deletion of Hif1α in myeloid cells on LPS-induced ALI.

RESULTS

Deletion of Hif1α in myeloid cells could reduce lung edema, inflammatory cell infiltration, and lung and BAL inflammatory cytokines in E. coli-induced ALI. Flow cytometric analysis revealed that α7 nAChR+CD11b+ cells in the lung and spleen were markedly increased in E. coli-challenged Hif1αfl/flLysMCre mice compared with E. coli-challenged Hif1αfl/fl mice. Double knockout of Chrna7 and Itgam increased HIF-1α expression in lung and spleen cells during lung E. coli infection. Vagotomy abolished the protective effect of deletion of Hif1α in myeloid cells on LPS-induced ALI.

CONCLUSION

Deletion of Hif1α in myeloid cells could protect mice from lung injury depending on α7 nAChR+CD11b+ cells and innervation of vagal circuits.

Estrogen-dependent downregulation of hypoxia-inducible factor (HIF)-2α in invasive breast cancer cells

The involvement of estrogen (E2) and hypoxia in tumor progression is well established. Hypoxia has been reported to activate and degrade estrogen receptor alpha (ERα) in breast cancer cells. Furthermore, E2 has been shown to regulate hypoxia-inducible factor (HIF)-1α protein, but its role in HIF-2α regulation remains largely unexplored. In this study, we found that both HIF-2α mRNA and protein were down-regulated in ER positive but not ER negative breast cancer cells upon treatment with E2. The analysis of 690 samples derived from 608 mixed and 82 triple-negative breast cancer patients revealed that high nuclear HIF-2α tumor levels are associated with a worse prognosis specifically in human epidermal growth factor receptor 2 (HER2) and hormone receptor positive patients. Consistently, ERα/HER2 positive breast cancer cells displayed less pronounced downregulation of HIF-2α by E2. Experiments using a histone deacetylase inhibitor indicate that the E2 mediated decrease in HIF-2α mRNA is due to transcriptional repression. A functional estrogen response element (ERE) was identified in the first intron of the gene encoding HIF-2α (EPAS1), suggesting transcriptional co-repressor recruitment by ERα. Our results demonstrate a novel modulation of HIF-2α in breast cancer cells, explaining the opposing regulation between HIF-1α and HIF-2α in hormone-responsive breast cancer.

Melanoma topology reveals a stem-like phenotype that promotes angiogenesis

Tumor angiogenesis provides critical nutrients for cancer progression and may also facilitate pathways for dissemination during the process of metastasis. It is well established that cells that metastasize display characteristics of stem cells; however, the prevailing paradigm points to these stem-like cells residing in the hypoxic niche within the tumor interior. Controlling the geometry at the interface of a population of melanoma cells reveals a role for perimeter topology in promoting a stem-like state with enhanced tumorigenicity. We show that this putative melanoma-initiating cell (MIC) demonstrates significant enhancement in the secretion of proangiogenic molecules. This finding suggests the possibility of an "invasive niche" at the perimeter of a growing tumor that promotes a MIC state with angiogenic activity. Using several in vitro and in vivo models of tumor angiogenesis, we see concurrent stem-like characteristics with initiation of neovascularization. In the absence of hypoxia, precise topological cues induce signaling through integrin α₅β₁ and downstream extracellular signal-regulated kinase (ERK) signaling to regulate the MIC secretome through the signal transducer and activator of transcription (STAT) and hypoxia-inducible factor 1α (HIF1α) pathways. Inhibiting integrin α₅β₁ and ERK signaling attenuates both the MIC phenotype and proangiogenic signaling. These results suggest that topological cues in the periphery of malignant melanoma promote the MIC state-using mechanotransduction in lieu of low oxygen-to facilitate the formation of new vasculature for progression and invasion.

Trefoil factor 3 contributes to the malignancy of glioma via regulating HIF-1α

Trefoil factor 3 (TFF3) plays significant roles in several solid tumors. However, the expression pattern and function of TFF3 in glioblastoma (GBM) have not been reported. Here, we report that expression level of TFF3 significantly elevated in glioma and correlated with the prognosis of glioma patients. Then we found TFF3 promotes proliferation, invasion, and migration and inhibits apoptosis of glioma cells in vitro, and delayed tumor progression in subcutaneous xenograft nude mice, and prolonged the median survival time in orthotopic xenograft mice. Moreover, knockdown of TFF3 reduced the expression of HIF-1α through a hypoxia-independent manner. These findings suggest that targeting TFF3 may offer a novel strategy for therapeutic intervention of malignant gliomas.

Hypoxia-inducible factor 1 alpha is a poor prognostic factor and potential therapeutic target in malignant peripheral nerve sheath tumor

Background

Malignant peripheral nerve sheath tumor (MPNST) is a rare soft tissue sarcoma with poor prognosis. Hypoxia-inducible factor 1 (HIF-1) plays a crucial role in the cellular response to hypoxia and regulates the expression of multiple genes involved in tumor progression in various cancers. However, the importance of the expression of HIF-1α in MPNSTs is unclear.

Methods

The expression of HIF-1α was examined immunohistochemically in 82 MPNST specimens. Cell culture assays of human MPNST cells under normoxic and hypoxic conditions were used to evaluate the impact of anti-HIF-1α–specific siRNA inhibition on cell survival. A screening kit was employed to identify small molecules that inhibited HIF-1α.

Results

The nuclear expression of HIF-1α was positive in 75.6% of MPNST samples (62/82 cases). Positivity for HIF-1α was a significant poor prognostic factor both in univariate (P = 0.048) and multivariate (P ≤ 0.0001) analyses. HIF-1α knockdown abrogated MPNST cell growth, inducing apoptosis. Finally, chetomin, an inhibitor of HIF-1α, effectively inhibited the growth of MPNST cells and induced their apoptosis.

Conclusion

Inhibition of HIF-1α signaling is a potential treatment option for MPNSTs.

All-trans retinoic acid preconditioning enhances proliferation, angiogenesis and migration of mesenchymal stem cell in vitro and enhances wound repair in vivo

OBJECTIVES

Stem cell therapy is considered to be a suitable alternative in treatment of a number of diseases. However, there are challenges in their clinical application in cell therapy, such as to reduce survival and loss of transplanted stem cells. It seems that chemical and pharmacological preconditioning enhances their therapeutic efficacy. In this study, we investigated effects of all-trans retinoic acid (ATRA) on survival, angiogenesis and migration of mesenchymal stem cells (MSCs) in vitro and in a wound-healing model.

MATERIALS AND METHODS

MSCs were treated with a variety of concentrations of ATRA, and mRNA expression of cyclo-oxygenase-2 (COX-2), hypoxia-inducible factor-1 (HIF-1), C-X-C chemokine receptor type 4 (CXCR4), C-C chemokine receptor type 2 (CCR2), vascular endothelial growth factor (VEGF), angiopoietin-2 (Ang-2) and Ang-4 were examined by qRT-PCR. Prostaglandin E2 (PGE2) levels were measured using an ELISA kit and MSC angiogenic potential was evaluated using three-dimensional tube formation assay. Finally, benefit of ATRA-treated MSCs in wound healing was determined with a rat excisional wound model.

RESULTS

In ATRA-treated MSCs, expressions of COX-2, HIF-1, CXCR4, CCR2, VEGF, Ang-2 and Ang-4 increased compared to control groups. Overexpression of the related genes was reversed by celecoxib, a selective COX-2 inhibitor. Tube formation and in vivo wound healing of ATRA-treated MSCs were also significantly enhanced compared to untreated MSCs.

CONCLUSION

Pre-conditioning of MSCs with ATRA increased efficacy of cell therapy by activation of survival signalling pathways, trophic factors and release of pro-angiogenic molecules.

Metabolic Reprogramming of Stem Cell Epigenetics

For many years, stem cell metabolism was viewed as a byproduct of cell fate status rather than an active regulatory mechanism; however, there is now a growing appreciation that metabolic pathways influence epigenetic changes associated with lineage commitment, specification, and self-renewal. Here we review how metabolites generated during glycolytic and oxidative processes are utilized in enzymatic reactions leading to epigenetic modifications and transcriptional regulation. We discuss how "metabolic reprogramming" contributes to global epigenetic changes in the context of naive and primed pluripotent states, somatic reprogramming, and hematopoietic and skeletal muscle tissue stem cells, and we discuss the implications for regenerative medicine.

Hypoxic inactivation of glycogen synthase kinase-3β promotes gastric tumor growth and angiogenesis by facilitating hypoxia-inducible factor-1 signaling

Since the molecular mechanism of hypoxic adaptation in cancer cells is cell-type specific, we investigated whether glycogen synthase kinase-3β (GSK-3β) activation is involved in hypoxia-induced gastric tumor promotion. Stable gastric cancer cell lines (SNU-638, SNU-484, MKN1, and MKN45) were cultured under hypoxic conditions. Cells overexpressing wild-type GSK-3β (WT-GSK-3β) or kinase-dead mutant of GSK-3β (KD-GSK-3β) were generated and used for cell culture and animal studies. In cell culture experiments, hypoxia decreased GSK-3β activation in gastric cancer cells. Cell viability and the expressions of HIF-1α protein and VEGF mRNA in gastric cancer cells were higher in KD-GSK-3β transfectants than in WT-GSK-3β transfectants under hypoxic conditions, but not under normoxic conditions. Gastric cancer xenografts showed that tumor growth, microvessel area, HIF-1α activation, and VEGF expression were higher in KD-GSK-3β tumors than in WT-GSK-3β tumors in vivo. In addition, the expression of hypoxia-induced HIF-1α protein was regulated by GSK-3β at the translational level. Our data suggest that GSK-3β is involved in hypoxic adaptation of gastric cancer cells as an inhibitory upstream regulator of the HIF-1α/VEGF signaling pathway.

Hypoxia-independent drivers of melanoma angiogenesis

Tumor angiogenesis is a process which is traditionally regarded as the tumor’s response to low nutrient supply occurring under hypoxic conditions. However, hypoxia is not a pre-requisite for angiogenesis. The fact that even single tumor cells or small tumor cell aggregates are capable of attracting blood vessels reveals the early metastatic capability of tumor cells. This review sheds light on the hypoxia-independent mechanisms of tumor angiogenesis in melanoma.

In vitro study of normoxic epidermal growth factor receptor-induced hypoxia-inducible factor-1-alpha, vascular endothelial growth factor, and BNIP3 expression in head and neck squamous cell carcinoma cell lines: Implications for anti-epidermal growth factor receptor therapy

BACKGROUND

We previously showed that activation of epidermal growth factor receptor (EGFR) induces hypoxia inducible factor-1α (HIF-1α) in head and neck squamous cell carcinoma (HNSCC) cells. In this study, we have furthered this by investigating the mechanism of HIF-1α activation by epidermal growth factor (EGF) and its association with the sensitivity to gefitinib.

METHODS

EGFR/HIF-1α signaling was tested by immunoblot, polymerase chain reaction (PCR), cell proliferation, and apoptosis assays.

RESULTS

HIF-1α accumulated in cells overexpressing EGF and phosphorylated epidermal growth factor receptor (pEGFR), phosphatidylinositol-3-kinase (pPI3K), and mitogen-activated protein kinase (pMAPK). EGF-induced expression of HIF-1α and its targets, vascular endothelial growth factor (VEGF) and BNIP3, were blocked by gefitinib and PI3K-inhibitors and MAPK-inhibitors. HIF-1α-siRNAs abrogated EGF-induced BNIP3 but not VEGF expression. Gefitinib inhibited cell proliferation and induced apoptosis more strongly in cells with constitutively active EGFR/HIF-1α signaling than in cells lacking activation of these pathways. HIF-1α-siRNA treatment reduced sensitivity to gefitinib.

CONCLUSION

The search for molecular predictors of sensitivity to gefitinib in HNSCC should be extended to the activation status of EGFR-downstream pathways, phosphorylated protein kinase B, pMAPK, and HIF-1α.

Link between PI3K/AKT/PTEN Pathway and NOX Proteinin Diseases

Accumulating evidence has revealed that thePI3K/AKT/PTENpathway acts as a pivotal determinant of cell fate regarding senescence and apoptosis, which is mediated by intracellular reactive oxygen species (ROS) generation. NADPH oxidase (NOX) family of enzymes generates the ROS. The regulation of NOX enzymes is complex, with many members of this family exhibiting complexity in terms of subunit composition, cellular location, and tissue-specific expression. Cells are continuously exposed to the ROS, which represent mutagens and are thought to be a major contributor to several diseases including cancer and aging process. Therefore, cellular ROS sensing and metabolism are firmly regulated by a variety of proteins involved in the redox mechanism. In this review, the roles of oxidative stress in PI3K/AKT/PTEN signaling are summarized with a focus on the links between the pathways and NOX protein in several diseases including cancer and aging.

Profilin-1 phosphorylation directs angiocrine expression and glioblastoma progression through HIF-1α accumulation

The tumor vascular microenvironment supports tumorigenesis by supplying not only oxygen and diffusible nutrients but also by secreting soluble factors that promote tumorigenesis. Here we identify a feed-forward mechanism in which endothelial cells (EC), in response to tumor-derived mediators, release angiocrines driving aberrant vascularization and glioblastoma multiforme (GBM) progression through a hypoxia-independent induction of hypoxia-inducible factor (HIF)-1α. Phosphorylation of profilin-1 (Pfn-1) at Tyr¹²⁹ in EC induces binding to tumor suppressor protein von Hippel-Lindau (VHL), prevents VHL-mediated degradation of prolyl-hydroxylated HIF-1α, culminating in HIF-1α accumulation even in normoxia. Elevated HIF-1α induces expression of multiple angiogenic factors, leading to vascular abnormality and tumor progression. In a genetic model of GBM, mice with an EC-specific defect in Pfn-1 phosphorylation exhibit reduced tumor angiogenesis, normalized vasculature, and improved survival. Moreover, EC-specific Pfn-1 phosphorylation is associated with tumor aggressiveness in human glioma. These findings suggest that targeting Pfn-1 phosphorylation may offer a selective strategy for therapeutic intervention of malignant solid tumors.

Nonhypoxic regulation and role of hypoxia-inducible factor 1 in aromatase inhibitor resistant breast cancer

Introduction

Although aromatase inhibitors (AIs; for example, letrozole) are highly effective in treating estrogen receptor positive (ER+) breast cancer, a significant percentage of patients either do not respond to AIs or become resistant to them. Previous studies suggest that acquired resistance to AIs involves a switch from dependence on ER signaling to dependence on growth factor-mediated pathways, such as human epidermal growth factor receptor-2 (HER2). However, the role of HER2, and the identity of other relevant factors that may be used as biomarkers or therapeutic targets remain unknown. This study investigated the potential role of transcription factor hypoxia inducible factor 1 (HIF-1) in acquired AI resistance, and its regulation by HER2.

Methods

In vitro studies using AI (letrozole or exemestane)-resistant and AI-sensitive cells were conducted to investigate the regulation and role of HIF-1 in AI resistance. Western blot and RT-PCR analyses were conducted to compare protein and mRNA expression, respectively, of ERα, HER2, and HIF-1α (inducible HIF-1 subunit) in AI-resistant versus AI-sensitive cells. Similar expression analyses were also done, along with chromatin immunoprecipitation (ChIP), to identify previously known HIF-1 target genes, such as breast cancer resistance protein (BCRP), that may also play a role in AI resistance. Letrozole-resistant cells were treated with inhibitors to HER2, kinase pathways, and ERα to elucidate the regulation of HIF-1 and BCRP. Lastly, cells were treated with inhibitors or inducers of HIF-1α to determine its importance.

Results

Basal HIF-1α protein and BCRP mRNA and protein are higher in AI-resistant and HER2-transfected cells than in AI-sensitive, HER2- parental cells under nonhypoxic conditions. HIF-1α expression in AI-resistant cells is likely regulated by HER2 activated-phosphatidylinositide-3-kinase/Akt-protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) pathway, as its expression was inhibited by HER2 inhibitors and kinase pathway inhibitors. Inhibition or upregulation of HIF-1α affects breast cancer cell expression of BCRP; AI responsiveness; and expression of cancer stem cell characteristics, partially through BCRP.

Conclusions

One of the mechanisms of AI resistance may be through regulation of nonhypoxic HIF-1 target genes, such as BCRP, implicated in chemoresistance. Thus, HIF-1 should be explored further for its potential as a biomarker of and therapeutic target.

Anoikis molecular pathways and its role in cancer progression

Anoikis is a programmed cell death induced upon cell detachment from extracellular matrix, behaving as a critical mechanism in preventing adherent-independent cell growth and attachment to an inappropriate matrix, thus avoiding colonizing of distant organs. As anchorage-independent growth and epithelial-mesenchymal transition, two features associated with anoikis resistance, are vital steps during cancer progression and metastatic colonization, the ability of cancer cells to resist anoikis has now attracted main attention from the scientific community. Cancer cells develop anoikis resistance due to several mechanisms, including change in integrins' repertoire allowing them to grow in different niches, activation of a plethora of inside-out pro-survival signals as over-activation of receptors due to sustained autocrine loops, oncogene activation, growth factor receptor overexpression, or mutation/upregulation of key enzymes involved in integrin or growth factor receptor signaling. In addition, tumor microenvironment has also been acknowledged to contribute to anoikis resistance of bystander cancer cells, by modulating matrix stiffness, enhancing oxidative stress, producing pro-survival soluble factors, triggering epithelial-mesenchymal transition and self-renewal ability, as well as leading to metabolic deregulations of cancer cells. All these events help cancer cells to inhibit the apoptosis machinery and sustain pro-survival signals after detachment, counteracting anoikis and constituting promising targets for anti-metastatic pharmacological therapy. This article is part of a Special Section entitled: Cell Death Pathways.

Twist2 promotes ovarian cancer cell survival through activation of Akt

Hypoxia-inducible factor-1 α (HIF-1α) is an important prognostic factor in ovarian carcinoma. Hypoxia contributes to tumor progression and is involved in the epithelial-mesenchymal transition (EMT). Twist2 is an EMT regulator, however, it remains poorly understood in ovarian carcinoma. The present study evaluated the expression of HIF-1α and Twist2 and further investigated whether Twist2 is involved in hypoxia-induced apoptosis in ovarian cancer. A series of matched paraffin-embedded tissue sections from human primary ovarian cancer and normal ovarian tissues were examined through immunohistochemical analysis, a Twist2-overexpressing stable ovarian cancer cell line was established and deferoxamine (DFO) was introduced to simulate hypoxic conditions. DFO-induced apoptosis was examined by fluorescence microscopy, MTT assays and flow cytometry. In addition, a western blot analysis was performed to examine the molecular mechanism(s) of action. Twist2 increased in epithelial ovarian cancers associated with HIF-1α expression. The acquired expression of Twist2 was able to promote the survival of ovarian cancer cells through Akt phosphorylation under DFO-induced hypoxic stress. The results suggest that Twist2 activates the PI-3K-Akt pathway to protect cells from apoptosis in a hypoxic environment. Moreover, Twist2 may be involved in the HIF-1α signaling pathway in ovarian cancer.

The oncogene HER2/neu (ERBB2) requires the hypoxia-inducible factor HIF-1 for mammary tumor growth and anoikis resistance

ERBB2, a receptor tyrosine kinase amplified in breast cancer, is a well established regulator of tumor growth in vivo and anoikis resistance leading to disruption of architecture in three-dimensional mammary epithelial acinar structures in vitro. ERBB2 promotes anoikis resistance by maintaining signaling pathways and by rescuing metabolic defects and thus inhibiting accumulation of deleterious reactive oxygen species. Recent evidence suggests that hypoxia, via hypoxia-inducible factors (HIFs), can inhibit anoikis; thus, we hypothesized that HIF-1 may play a role in ERBB2-mediated anoikis resistance and oncogenesis. Indeed, tumors isolated from MMTV-Neu mice contain elevated HIF-1α levels and tumor cells created from MMTV-Neu mice harboring deletion of Hif1α alleles reduced primary tumor growth in vivo. ERBB2 overexpressing cancer cells stabilize HIF under normoxic conditions and require HIF-1 for ERBB2-mediated anchorage-independence, three-dimensional culture growth and anoikis resistance. HIF-1 reduction in ERBB2 cells was associated with induction of the pro-anoikis protein BIM and decreased ERK and AKT signaling during cell detachment. ERBB2-mediated inhibition of metabolic defects, including decreased reactive oxygen species generation in suspension, required HIF-1 expression that was critical for ERBB2-mediated oncogenesis. Gene expression profiling of hypoxic three-dimensional acinar structures identified a number of genes elevated in response to hypoxia that are known ERBB2 targets, suggesting that hypoxic conditions and ERBB2 overexpression share both phenotypic and genetic components via HIF-1 regulation. Thus, our data demonstrate that ERBB2 requires HIF-1 for tumor growth and suggest that HIF is a major downstream regulator of ERBB2 that protects cells from anoikis and metabolic stress caused by decreased matrix adhesion.

Enhanced tumor suppression by adenoviral PTEN gene therapy combined with cisplatin chemotherapy in small-cell lung cancer

DNA-damaging anticancer drug cisplatin (cis-diamminedichloroplatinum) (DDP)-based chemotherapy is the mainstay and standard treatment for small-cell lung cancer (SCLC). However, frequent relapse and chemoresistance of SCLC remains a significant therapeutic hurdle. Tumor suppressor phosphatase and tensin homolog deleted on chromosome 10 (PTEN) as a negative regulator of phosphoinositide 3-kinase/AKT survival pathway exhibits strong tumor-suppressive activities. A combination of chemotherapy and gene therapy (chemogene therapy) is a promising practice in cancer therapy. In this report, we examined the combined antitumor effect of adenovirus-mediated PTEN (AdVPTEN) gene therapy and DDP chemotherapy on PTEN-null NCI-H446 human SCLC cells in vitro and in vivo in athymic BALB/c nude mice. We demonstrated that AdVPTEN plus DDP enhanced growth suppression, cell-cycle G1 phase arrest and apoptosis in in vitro NCI-H446 tumor cells and in vivo NCI-H446 xenografted tumors subcutaneously inoculated in nude mice. Mechanistically, AdVPTEN plus DDP exerted an overlapping effect on upregulation of P53, P21, P27, Bax and Cleaved Caspase-3 as well as downregulation of Bcl-2 and survivin in in vitro and in vivo NCI-H446 tumor cells. Moreover, AdVPTEN plus DDP additively reduced tumor vessel CD34 expression and microvessel density in vivo. The enhanced therapeutic efficacy elicited by AdVPTEN plus DDP was closely associated with additive induction of G1 phase arrest and apoptosis via substantially modulating cell-cycle regulation molecules and activating intrinsic apoptotic pathway through P53 restoration, and overlapping inhibition of tumor angiogenesis. Thus, our results indicated that AdVPTEN combined with DDP may be a novel and effective chemogene therapy modality for human SCLC.

Roles for PI3K/AKT/PTEN Pathway in Cell Signaling of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is the most common form of liver pathologies and is associated with obesity and the metabolic syndrome, which represents a range of fatty liver diseases associated with an increased risk of type 2 diabetes. Molecular mechanisms underlying how to make transition from simple fatty liver to nonalcoholic steatohepatitis (NASH) are not well understood. However, accumulating evidence indicates that deregulation of the phosphatidylinositol 3-kinase (PI3K)/AKT pathway in hepatocytes is a common molecular event associated with metabolic dysfunctions including obesity, metabolic syndrome, and the NAFLD. A tumor suppressor PTEN negatively regulates the PI3K/AKT pathways through its lipid phosphatase activity. Molecular studies in the NAFLD support a key role for PTEN in hepatic insulin sensitivity and the development of steatosis, steatohepatitis, and fibrosis. We review recent studies on the features of the PTEN and the PI3K/AKT pathway and discuss the protein functions in the signaling pathways involved in the NAFLD. The molecular mechanisms contributing to the diseases are the subject of considerable investigation, as a better understanding of the pathogenesis will lead to novel therapies for a condition.

Redox regulation of tumor suppressor PTEN in cancer and aging (Review)

Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) has been shown to act as a tumor suppressor whose function includes important roles in regulating oxidative stress, indicating a potential role in oxidative damage-associated cancer. Accumulating evidence has revealed that PTEN also acts as a pivotal determinant of cell fate, regarding senescence and apoptosis, which is mediated by intracellular reactive oxygen species (ROS) generation. Cells are continuously exposed to ROS, which represent mutagens and are thought to be a major contributor to cancer and the aging process. Therefore, cellular ROS sensing and metabolism are firmly regulated by a variety of proteins involved in the redox mechanism. In this review, PTEN and the roles of oxidative stress in phosphoinositide-3 kinase/AKT signaling are summarized with a focus on the links between the pathways and ROS in cancer and aging.

Nicotine promotes proliferation of human nasopharyngeal carcinoma cells by regulating α7AChR, ERK, HIF-1α and VEGF/PEDF signaling

Nicotine, the major component in cigarette smoke, can promote tumor growth and angiogenesis, but the precise mechanisms involved remain largely unknown. Here, we investigated the mechanism of action of nicotine in human nasopharyngeal carcinoma (NPC) cells. Nicotine significantly promoted cell proliferation in a dose and time-dependent manner in human NPC cells. The mechanism studies showed that the observed stimulation of proliferation was accompanied by the nicotine-mediated simultaneous modulation of α7AChR, HIF-1α, ERK and VEGF/PEDF signaling. Treatment of NPC cells with nicotine markedly upregulated the expression of α7AChR and HIF-1α proteins. Transfection with a α7AChR or HIF-1α-specific siRNA or a α7AChR-selective inhibitor significantly attenuated the nicotine-mediated promotion of NPC cell proliferation. Nicotine also promoted the phosphorylation of ERK1/2 but not JNK and p38 proteins, thereby induced the activation of ERK/MAPK signaling pathway. Pretreatment with an ERK-selective inhibitor effectively reduced the nicotine-induced proliferation of NPC cells. Moreover, nicotine upregulated the expression of VEGF but suppressed the expression of PEDF at mRNA and protein levels, leading to a significant increase of the ratio of VEGF/PEDF in NPC cells. Pretreatment with a α7AChR or ERK-selective inhibitor or transfection with a HIF-1α-specific siRNA in NPC cells significantly inhibited the nicotine-induced HIF-1α expression and VEGF/PEDF ratio. These results therefore indicate that nicotine promotes proliferation of human NPC cells in vitro through simultaneous modulation of α7AChR, HIF-1α, ERK and VEGF/PEDF signaling and suggest that the related molecules such as HIF-1α might be the potential therapeutic targets for tobacco-associated diseases such as nasopharyngeal carcinomas.

Resistin: functional roles and therapeutic considerations for cardiovascular disease

Resistin, originally described as an adipocyte-specific hormone, has been suggested to be an important link between obesity, insulin resistance and diabetes. Although its expression was initially defined in adipocytes, significant levels of resistin expression in humans are mainly found in mononuclear leukocytes, macrophages, spleen and bone marrow cells. Increasing evidence indicates that resistin plays important regulatory roles apart from its role in insulin resistance and diabetes in a variety of biological processes: atherosclerosis and cardiovascular disease (CVD), non-alcoholic fatty liver disease, autoimmune disease, malignancy, asthma, inflammatory bowel disease and chronic kidney disease. As CVD accounts for a significant amount of morbidity and mortality in patients with diabetes and without diabetes, it is important to understand the role that adipokines such as resistin play in the cardiovascular system. Evidence suggests that resistin is involved in pathological processes leading to CVD including inflammation, endothelial dysfunction, thrombosis, angiogenesis and smooth muscle cell dysfunction. The modes of action and signalling pathways whereby resistin interacts with its target cells are beginning to be understood. In this review, the current knowledge about the functions and pathophysiological implications of resistin in CVD development is summarized; clinical translations, therapeutic considerations and future directions in the field of resistin research are discussed.

LINKED ARTICLES

This article is part of a themed section on Fat and Vascular Responsiveness. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-3.

Resistin: functional roles and therapeutic considerations for cardiovascular disease

Resistin, originally described as an adipocyte-specific hormone, has been suggested to be an important link between obesity, insulin resistance and diabetes. Although its expression was initially defined in adipocytes, significant levels of resistin expression in humans are mainly found in mononuclear leukocytes, macrophages, spleen and bone marrow cells. Increasing evidence indicates that resistin plays important regulatory roles apart from its role in insulin resistance and diabetes in a variety of biological processes: atherosclerosis and cardiovascular disease (CVD), non-alcoholic fatty liver disease, autoimmune disease, malignancy, asthma, inflammatory bowel disease and chronic kidney disease. As CVD accounts for a significant amount of morbidity and mortality in patients with diabetes and without diabetes, it is important to understand the role that adipokines such as resistin play in the cardiovascular system. Evidence suggests that resistin is involved in pathological processes leading to CVD including inflammation, endothelial dysfunction, thrombosis, angiogenesis and smooth muscle cell dysfunction. The modes of action and signalling pathways whereby resistin interacts with its target cells are beginning to be understood. In this review, the current knowledge about the functions and pathophysiological implications of resistin in CVD development is summarized; clinical translations, therapeutic considerations and future directions in the field of resistin research are discussed.

LINKED ARTICLES

This article is part of a themed section on Fat and Vascular Responsiveness. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-3.

Silver nanoparticles modify VEGF signaling pathway and mucus hypersecretion in allergic airway inflammation

The anti-inflammatory action of silver nanoparticles (NPs) has been reported in a murine model of asthma in a previous study. But more specific mechanisms of silver NPs in an attenuation of allergic airway inflammation have not yet been established. Vascular and mucous changes are believed to contribute largely in pathophysiology in asthma. Among various factors related to vascular changes, vascular endothelial growth factor (VEGF) plays a pivotal role in vascular changes in asthma. Mucin proteins MUC5AC and MUC5B have been implicated as markers of goblet cell metaplasia in lung pathologies. The aim of this study was to investigate the effects of silver NPs on VEGF signaling pathways and mucus hypersecretion. Ovalbumin (OVA)-inhaled female BALBc mice were used to evaluate the role of silver NPs and the related molecular mechanisms in allergic airway disease. In this study, with an OVA-induced murine model of allergic airway disease, it was found that the increased levels of hypoxia-inducible factor (HIF)-1α, VEGF, phosphatidylinositol-3 kinase (PI3K) and phosphorylated-Akt levels, and mucous glycoprotein expression (Muc5ac) in lung tissues were substantially decreased by the administration of silver NPs. In summary, silver NPs substantially suppressed mucus hypersecretion and PI3K/HIF-1α/VEGF signaling pathway in an allergic airway inflammation.

Hypoxia decreased chemosensitivity of breast cancer cell line MCF-7 to paclitaxel through cyclin B1

Hypoxia, frequently found in the center of solid tumors, may lead to enhance the production of key factor in cell survival, invasion, angiogenesis and loss of apoptosis. The low oxygen tension in hypoxic tumors is also known to interfere with the efficacy of chemotherapy, but the underlying mechanisms are not very clear. Paclitaxel (PTX) is an active agent used in breast cancer chemotherapy, which disturbs microtubule dynamics and impairs the transition of cells from metaphase to anaphase in mitosis, leading to cell death by apoptosis. In the present study, we try to determine whether hypoxia can decrease the chemosensitivity of human breast carcinoma cells to PTX and elucidate the underlying mechanism. We found that hypoxia could decrease PTX-induced cell death and G(2)/M arrest. Furthermore, our results showed that hypoxia inhibit PTX-induced soluble tubulin polymerized. In addition, we also found hypoxia could suppress PTX-induced cell cycle protein-cyclin B1 expression in MCF-7 cells. To further investigate whether the inhibitory effect of hypoxia on PTX-induced cell death is mediated by decreasing levels of cyclin B1, cyclin B1-transfected MCF-7 cells were used under hypoxic condition. The data showed that the hypoxia-based decreasing chemosensitivity of breast cancer cells to PTX was reversed by cyclin B1. We also found that overexpression of cyclin B1 could significantly increase the sensitivity of MCF-7 cells to PTX by stimulating soluble polymerized tubulin. Overall, hypoxia decreases cyclin B1, which could in turn reverse hypoxia-induced decreasing chemosensitivity to PTX in breast cancer cell line MCF-7.

SV40 T/t-common polypeptide inhibits angiogenesis and growth of HER2-overexpressing human ovarian cancer

Human epidermal growth factor receptor 2 (HER2) is frequently overexpressed in human ovarian cancers and its overexpression is associated with increased angiogenesis, increased metastasis and reduced survival. Inhibition of HER2 in HER2-overexpressing cancers can lead to reduced angiogenesis and improved survival. Previously, we reported that SV40 T/t-common polypeptide has transcriptional repression activity and can inhibit HER2 expression. In this study, we investigated the effect of T/t-common on the angiogenesis-inducing activity of HER2-overexpressing human SK-OV-3 ovarian cancer cells. We found that compared to conditioned medium from control SK-OV-3 cancer cells, conditioned medium from T/t-common-expressing SK-OV-3 cells had a reduced ability to induce endothelial cell migration and tube formation in vitro and microvessel formation in vivo. These data indicate that T/t-common can inhibit the ability of SK-OV-3 cancer cells to induce angiogenesis. T/t-common was found to be able to downregulate the expression of several proangiogenic factors, including vascular endothelial growth factor-A, interleukin-8, basic fibroblast growth factor, matrix metalloproteinase-2 and urokinase-type plasminogen activator, and upregulate antiangiogenic factors, including thrombospondin-1 and tissue inhibitor of metalloproteinases-1 in SK-OV-3 cancer cells. Finally, we demonstrated that T/t-common could inhibit the angiogenesis and growth of HER2-overexpressing human ovarian tumor in NOD/SCID mice. Taken together, the data suggest that T/t-common had the potential to be developed as a new antiangiogenic agent specific for treating HER2-overexpressing ovarian cancers.

Aldose reductase inhibition prevents hypoxia-induced increase in hypoxia-inducible factor-1alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF) by regulating 26 S proteasome-mediated protein degradation in human colon cancer cells

The development of intratumoral hypoxia, a hallmark of rapidly progressing solid tumors, renders tumor cells resistant to chemotherapy and radiation therapy. We have recently shown that inhibition of aldose reductase (AR), an enzyme that catalyzes the reduction of lipid aldehydes and their glutathione conjugates, prevents human colon cancer cell growth in culture as well as in nude mouse xenografts by inhibiting the NF-κB-dependent activation of oxidative stress-mediated inflammatory and carcinogenic markers. However, the role of AR in mediating hypoxic stress signals is not known. We therefore investigated the molecular mechanisms by which AR inhibition prevents the hypoxia-induced human colon cancer cells growth and invasion. Our results indicate that AR inhibition by the pharmacological inhibitor fidarestat or ablation by AR-specific siRNA prevents hypoxia-induced proliferation of HT29, SW480, and Caco-2 colon cancer cells. Furthermore, hypoxia-induced increase in the level of HIF-1α in colon cancer cells was significantly decreased by AR inhibition. During hypoxic conditions, treatment of HT29 cells with the AR inhibitor fidarestat significantly decreased the expression of vascular endothelial growth factor, a down target of HIF-1α, at both mRNA and protein levels and also prevented the activation of PI3K/AKT, GSK3β, Snail, and lysyl oxidase. Furthermore, inhibition of hypoxia-induced HIF-1α protein accumulation by AR inhibition was abolished in the presence of MG132, a potent inhibitor of the 26 S proteasome. In addition, AR inhibition also prevented the hypoxia-induced inflammatory molecules such as Cox-2 and PGE2 and expression of extracellular matrix proteins such as MMP2, vimentin, uPAR, and lysyl oxidase 2. In conclusion, our results indicate that AR mediates hypoxic signals, leading to tumor progression and invasion.

Carbonic anhydrase IX overexpression is associated with diminished prognosis in esophageal cancer and correlates with Her-2 expression

BACKGROUND

Carbonic anhydrase IX (CAIX), a transmembrane glycoprotein, seems to play a key role in the adaption of tumor cells to hypoxia. This study was designed to investigate the clinical role of CAIX and its association with Her-2 in a large cohort of adeno- (AC) and squamous cell carcinomas (SCC) of the esophagus and their metastases.

METHODS

Expression of CAIX and Her-2 was investigated immunohistochemically in formalin fixed, paraffin-embedded tissue from 330 esophageal cancers (182 ACS, 148 SCCs). Corresponding lymph node metastases in 137 cases, distant metastases in 34 cases, and local recurrences in 14 cases were analyzed for CAIX expression.

RESULTS

A total of 147 cases (44.5%) showed strong CAIX expression (AC: 46.7%; ACC: 41.9%). CAIX status of the primary tumor influenced CAIX expression in corresponding lymph node metastases (P<0.001, linear regression). High CAIX-expression was an independent prognostic factor for shorter overall and disease-free survival (P≤0.05, Cox regression). Twenty-nine ACs (15.9%) and 6 SCCs (4.1%) showed Her-2 overexpression. In AC, a significant positive correlation between the Her-2 status and CAIX expression was found (P=0.009, chi-square test).

CONCLUSIONS

High CAIX expression is associated with shorter survival in esophageal cancer, and the hypoxic phenotype seems to be preserved at least during formation of lymph node metastases. Inhibition of CAIX might reduce the ability of tumor cells to establish disseminated disease. In Her-2 overexpressing ACs, blocking of this tyrosine kinase, e.g., by monoclonal antibodies, might induce this effect.

Oncogene activation induces metabolic transformation resulting in insulin-independence in human breast cancer cells

Normal breast epithelial cells require insulin and EGF for growth in serum-free media. We previously demonstrated that over expression of breast cancer oncogenes transforms MCF10A cells to an insulin-independent phenotype. Additionally, most breast cancer cell lines are insulin-independent for growth. In this study, we investigated the mechanism by which oncogene over expression transforms MCF10A cells to an insulin-independent phenotype. Analysis of the effects of various concentrations of insulin and/or IGF-I on proliferation of MCF10A cells demonstrated that some of the effects of insulin were independent from those of IGF-I, suggesting that oncogene over expression drives a true insulin-independent proliferative phenotype. To test this hypothesis, we examined metabolic functions of insulin signaling in insulin-dependent and insulin-independent cells. HER2 over expression in MCF10A cells resulted in glucose uptake in the absence of insulin at a rate equal to insulin-induced glucose uptake in non-transduced cells. We found that a diverse set of oncogenes induced the same result. To gain insight into how HER2 oncogene signaling affected increased insulin-independent glucose uptake we compared HER2-regulated gene expression signatures in MCF10A and HER2 over expressing MCF10A cells by differential analysis of time series gene expression data from cells treated with a HER2 inhibitor. This analysis identified genes specifically regulated by the HER2 oncogene, including VAMP8 and PHGDH, which have known functions in glucose uptake and processing of glycolytic intermediates, respectively. Moreover, these genes specifically implicated in HER2 oncogene-driven transformation are commonly altered in human breast cancer cells. These results highlight the diversity of oncogene effects on cell regulatory pathways and the importance of oncogene-driven metabolic transformation in breast cancer.

HIF-1α inhibition ameliorates an allergic airway disease via VEGF suppression in bronchial epithelium

Hypoxia-inducible factor-1α (HIF-1α) plays a critical role in immune and inflammatory responses. One of the HIF-1α target genes is vascular endothelial growth factor (VEGF), which is a potent stimulator of inflammation, airway remodeling, and physiologic dysregulation in allergic airway diseases. Using OVA-treated mice and murine tracheal epithelial cells, the signaling networks involved in HIF-1α activation and the role of HIF-1α in the pathogenesis of allergic airway disease were investigated. Transfection of airway epithelial cells with HIF-1α siRNA suppressed VEGF expression. In addition, the increased levels of HIF-1α and VEGF in lung tissues after OVA inhalation were substantially decreased by an HIF-1α inhibitor, 2-methoxyestradiol. Our data also show that the increased numbers of inflammatory cells, increased airway hyperresponsiveness, levels of IL-4, IL-5, IL-13, and vascular permeability in the lungs after OVA inhalation were significantly reduced by 2-methoxyestradiol or a VEGF inhibitor, CBO-P11. Moreover, we found that inhibition of the PI3K p110δ isoform (PI3K-δ) or HIF-1α reduced OVA-induced HIF-1α activation in airway epithelial cells. These findings indicate that HIF-1α inhibition may attenuate antigen-induced airway inflammation and hyperresponsiveness through the modulation of vascular leakage mediated by VEGF, and that PI3K-δ signaling may be involved in the allergen-induced HIF-1α activation.

EGFR overexpression induces activation of telomerase via PI3K/AKT-mediated phosphorylation and transcriptional regulation through Hif1-alpha in a cellular model of oral-esophageal carcinogenesis

Telomerase plays an important role during immortalization and malignant transformation as crucial steps in the development of human cancer. In a cellular model of oral-esophageal carcinogenesis, recapitulating the human disease, immortalization occurred independent of the activation of telomerase but through the recombination-based alternative lengthening of telomeres (ALT). In this stepwise model, additional overexpression of EGFR led to in vitro transformation and activation of telomerase with homogeneous telomere elongation in already immortalized oral squamous epithelial cells (OKF6-D1_dnp53). More interestingly, EGFR overexpression activated the PI3K/AKT pathway. This strongly suggested a role for telomerase in tumor progression in addition to just elongating telomeres and inferring an immortalized state. Therefore, we sought to identify the regulatory mechanisms involved in this activation of telomerase and in vitro transformation induced by EGFR. In the present study we demonstrate that telomerase expression and activity are induced through both direct phosphorylation of hTERT by phospho-AKT as well as PI3K-dependent transcriptional regulation involving Hif1-alpha as a key transcription factor. Furthermore, EGFR overexpression enhanced cell cycle progression and proliferation via phosphorylation and translocation of p21. Whereas immortalization was induced by ALT, in vitro transformation was associated with telomerase activation, supporting an additional role for telomerase in tumor progression besides elongating telomeres.

A hypoxia-dependent upregulation of hypoxia-inducible factor-1 by nuclear factor-κB promotes gastric tumour growth and angiogenesis

BACKGROUND

The underlying mechanisms involved in the activation of hypoxia-inducible factor-1 (HIF-1) in gastric cancer remain unclear. As nuclear factor-κB (NF-κB) as well as HIF-1 have been implicated in angiogenesis of various cancers, we investigated their relationship in gastric cancer.

METHODS

Nuclear expressions of HIF-1α and NF-κB/RelA were assessed in 251 human gastric carcinoma specimens by immunohistochemical tissue array analysis. Stable human gastric cancer cells, infected with a retroviral vector containing super-suppressive mutant form of IκBα (IκBαM), were used for animal studies as well as cell culture experiments. Xenografted tumours were measured and IκBαM effects on angiogenesis and HIF-1α activation were assessed by immunohistochemistry, western blotting, luciferase reporter assay, and semiquantitative reverse transcription-polymerase chain reaction. In addition, NF-κB effects on the HIF-1α degradation and synthesis were examined.

RESULTS

Hypoxia-inducible factor-1α activation positively correlated with RelA activation in clinical gastric cancer samples (P<0.001). The IκBαM overexpression suppressed tumour growth, microvessel density, and HIF-1α activation in xenografted tumours. Cell culture experiments showed that hypoxia-induced HIF-1α expression was reduced by NF-κB inhibition under hypoxic conditions at the translational level.

CONCLUSION

The hypoxia-dependent activation of the NF-κB/HIF-1α/VEGF pathway contributes, at least in part, to gastric cancer promotion via enhancement of angiogenesis.

DLC1 negatively regulates angiogenesis in a paracrine fashion

The Rho GTPase-activating protein DLC1 is a tumor suppressor that is often deleted in liver cancer and downregulated in other cancers. DLC1 regulates the actin cytoskeleton, cell shape, adhesion, migration, and proliferation through its Rho GTPase-activating protein activity and focal adhesion localization. In this study, we silenced DLC1 in nonmalignant prostate epithelial cells to explore its tumor suppression functions. Small hairpin RNA-mediated silencing of DLC1 was insufficient to promote more aggressive phenotypes associated with tumor cell growth. In contrast, DLC1 silencing promoted pro-angiogenic responses through vascular endothelial growth factor (VEGF) upregulation, accompanied by the accumulation of hypoxia-inducible factor 1α and its nuclear localization. Notably, modulation of VEGF expression by DLC1 was dependent on epidermal growth factor receptor-MAP/ERK kinase-hypoxia-inducible factor 1 signaling but on RhoA pathways. Clinically, VEGF upregulation is a highly significant event in prostate cancers in which DLC1 is downregulated. Thus, our results strongly suggest that loss of DLC1 may serve as a "second hit" in promoting angiogenesis in a paracrine fashion during tumorigenesis.

Pdcd4 repression of lysyl oxidase inhibits hypoxia-induced breast cancer cell invasion

Metastasis to bone, liver and lungs is the primary cause of death in breast cancer patients. Our studies have revealed that the novel tumor suppressor Pdcd4 inhibits breast cancer cell migration and invasion in vitro. Loss of Pdcd4 in human nonmetastatic breast cancer cells increased the expression of lysyl oxidase (LOX) mRNA. LOX is a hypoxia-inducible amine oxidase, the activity of which enhances breast cancer cell invasion in vitro and in vivo. Specific inhibition of LOX activity by beta-aminopropionitrile or small interfering RNA decreased the invasiveness of T47D and MCF7 breast cancer cells attenuated for Pdcd4 function. Most significantly, loss of Pdcd4 augments hypoxia induction of LOX as well. Conversely, overexpression of Pdcd4 significantly reversed the hypoxia induction of LOX expression in T47D cells attenuated for Pdcd4. However, Pdcd4 did not affect hypoxia-inducible factor-1 (HIF-1) protein expression or HIF-1-responsive element-luciferase activity in response to hypoxia, suggesting that Pdcd4 regulation of LOX occurs through an HIF-independent mechanism. Nevertheless, the loss of Pdcd4 early in cancer progression may have an important role in the increased sensitivity of cancer cells to hypoxia through increased LOX activity and concomitant enhanced invasiveness.

Bisphosphonates suppress insulin-like growth factor 1-induced angiogenesis via the HIF-1alpha/VEGF signaling pathways in human breast cancer cells

Adjunctive chemotherapy with bisphosphonates has been reported to delay bone metastasis and improve overall survival in breast cancer. Aside from its antiresorptive effect, bisphosphonates exhibit antitumor activities, in vitro and in vivo, via several mechanisms, including antiangiogenesis. In this study, we investigated the potential molecular mechanisms underlying the antiangiogenic effect of non-nitrogen-containing and nitrogen-containing bisphosphonates, clodronate and pamidronate, respectively, in insulin-like growth factor (IGF)-1 responsive human breast cancer cells. We tested whether bisphosphonates had any effects on hypoxia-inducible factor (HIF)-1alpha/vascular endothelial growth factor (VEGF) axis that plays a pivotal role in tumor angiogenesis, and our results showed that both pamidronate and clodronate significantly suppressed IGF-1-induced HIF-1alpha protein accumulation and VEGF expression in MCF-7 cells. Mechanistically, we found that either pamidronate or clodronate did not affect mRNA expression of HIF-1alpha, but they apparently promoted the degradation of IGF-1-induced HIF-1alpha protein. Meanwhile, we found that the presence of pamidronate and clodronate led to a dose-dependent decease in the newly-synthesized HIF-1alpha protein induced by IGF-1 in breast cancer cells after proteasomal inhibition, thus, indirectly reflecting the inhibition of protein synthesis. In addition, our results indicated that the inhibitory effects of bisphosphonates on the HIF-1alpha/VEGF axis are associated with the inhibition of the phosphoinositide 3-kinase/AKT/mammalian target of rapamycin signaling pathways. Consistently, we demonstrated that pamidronate and clodronate functionally abrogated both in vitro and in vivo tumor angiogenesis induced by IGF-1-stimulated MCF-7 cells. These findings have highlighted an important mechanism of the pharmacological action of bisphosphonates in the inhibition of tumor angiogenesis in breast cancer cells.

Control of cyclin D1 and breast tumorigenesis by the EglN2 prolyl hydroxylase

2-Oxoglutarate-dependent dioxygenases, including the EglN prolyl hydroxylases that regulate HIF, can be inhibited with drug-like molecules. EglN2 is estrogen inducible in breast carcinoma cells and the lone Drosophila EglN interacts genetically with Cyclin D1. Although EglN2 is a nonessential gene, we found that EglN2 inactivation decreases Cyclin D1 levels and suppresses mammary gland proliferation in vivo. Regulation of Cyclin D1 is a specific attribute of EglN2 among the EglN proteins and is HIF independent. Loss of EglN2 catalytic activity inhibits estrogen-dependent breast cancer tumorigenesis and can be rescued by exogenous Cyclin D1. EglN2 depletion also impairs the fitness of lung, brain, and hematopoietic cancer lines. These findings support the exploration of EglN2 inhibitors as therapeutics for estrogen-dependent breast cancer and other malignancies.

Assessment of tumour hypoxia for prediction of response to therapy and cancer prognosis

Tumour cells exploit both genetic and adaptive means to survive and proliferate in hypoxic microenvironments, resulting in the outgrowth of more aggressive tumour cell clones. Direct measurements of tumour oxygenation, and surrogate markers of the hypoxic response in tumours (for instance, hypoxia inducible factor-1α, carbonic anhydrase 9 and glucose transporter-1) are well-established prognostic markers in solid cancers. However, individual markers do not fully capture the complex, dynamic and heterogeneous hypoxic response in cancer. To overcome this, expression profiling has been employed to identify hypoxia signatures in cohorts or models of human cancer. Several of these hypoxia signatures have demonstrated prognostic significance in independent cancer datasets. Nevertheless, individual hypoxia markers have been shown to predict the benefit from hypoxia-modifying or anti-angiogenic therapies. This review aims to discuss the clinical impact of translational work on hypoxia markers and to explore future directions for research in this area.

TNFalpha induces HIF-1alpha expression through activation of IKKbeta

The transcription factor hypoxia-inducible factor 1alpha (HIF-1alpha) is regulated by oxygen availability as well as various inflammatory mediators, including tumor necrosis factor alpha (TNFalpha). Early work suggested that the phosphatidylinositol-3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) signaling pathways are involved in TNFalpha-mediated HIF-1alpha accumulation and activation under normoxic conditions. Here, we provide evidence showing that IkappaB kinase beta (IKKbeta) is required for HIF-1alpha regulation by TNFalpha. We found that TNFalpha enhances HIF-1alpha protein expression in various breast cancer cell lines under either normoxic or hypoxia-mimicking conditions, but has little effect on the HIF-1alpha mRNA level. Increased HIF-1alpha expression was found in IKKbeta stable clones and transient transfectants, and depletion of IKKbeta consistently reduced the amount of HIF-1alpha protein. Treatment of cells with the IKKbeta inhibitor Bay 11-7082 reduced the TNFalpha-induced HIF-1alpha expression, suggesting that IKKbeta is required in this signaling pathway. Decreased expression of vascular endothelial growth factor (VEGF), a direct target of HIF-1alpha, was shown in IKKbeta-knockout mouse embryonic fibroblast cells. We further demonstrated a positive correlation between IKKbeta and VEGF expression in primary human breast cancer specimens. Our findings indicate that TNFalpha-induced HIF-1alpha accumulation is IKKbeta dependent, and may enable further understanding of the HIF-1alpha regulation by inflammatory signals.