The TWIST1 oncogene is a direct target of hypoxia-inducible factor-2alpha

The hypoxia factor Hif-1α controls neural crest chemotaxis and epithelial to mesenchymal transition

One of the most important mechanisms that promotes metastasis is the stabilization of Hif-1 (hypoxia-inducible transcription factor 1). We decided to test whether Hif-1α also was required for early embryonic development. We focused our attention on the development of the neural crest, a highly migratory embryonic cell population whose behavior has been likened to cancer metastasis. Inhibition of Hif-1α by antisense morpholinos in Xenopus laevis or zebrafish embryos led to complete inhibition of neural crest migration. We show that Hif-1α controls the expression of Twist, which in turn represses E-cadherin during epithelial to mesenchymal transition (EMT) of neural crest cells. Thus, Hif-1α allows cells to initiate migration by promoting the release of cell-cell adhesions. Additionally, Hif-1α controls chemotaxis toward the chemokine SDF-1 by regulating expression of its receptor Cxcr4. Our results point to Hif-1α as a novel and key regulator that integrates EMT and chemotaxis during migration of neural crest cells.

TWIST1 promoter methylation is associated with prognosis in tonsillar squamous cell carcinoma

Tonsillar squamous cell carcinomas (TSCC) frequently present with locally advanced diseases and cervical metastases, which are associated with poor prognoses. Epithelial-mesenchymal transition (EMT) is critical for tumor invasiveness and metastatic potential. Recent studies have shown that TWIST1-inducing EMT is overexpressed and hypermethylated in several cancers, indicating disease progression. The aim of the present study was to determine the clinical and prognostic significance of TWIST1 hypermethylation and EMT-related protein expression in TSCC. Methylation levels of TWIST1 promoter were analyzed by quantitative real-time methylation-specific polymerase chain reaction. Immunohistochemical analyses of TWIST1, Snail, and SMAD nuclear interacting protein-1 (SNIP1) were performed in 65 formalin-fixed, paraffin-embedded blocks of surgically resected specimens. TWIST1 promoter hypermethylation was found in 27.7% (18/65) of TSCCs. TWIST1 promoter hypermethylation was associated with poor differentiation (P = .012). Contralateral cervical lymph node metastasis was more frequently observed in TWIST1-methylated tumors (P = .029). High protein expressions of TWIST1, Snail, and SNIP1 were observed in 14 TSCC specimens (21.5%), 21 TSCC specimens (32.3%), and 38 TSCC specimens (58.5%), respectively. SNIP1 expression correlated significantly with TWIST1 methylation (P = .001), whereas TWIST1 protein expression did not. Contralateral cervical lymph node metastasis was an independent risk factor of the decreased overall survival rate (P = .002). TWIST1 methylation (P = .031) and pN stage (P = .037) were independent factors of poor prognoses affecting disease-free survival. TWIST1 promoter hypermethylation may be a useful molecular marker for predicting prognoses and contralateral cervical lymph node metastases in patients with TSCC.

HIF1α and HIF2α independently activate SRC to promote melanoma metastases

Malignant melanoma is characterized by a propensity for early lymphatic and hematogenous spread. The hypoxia-inducible factor (HIF) family of transcription factors is upregulated in melanoma by key oncogenic drivers. HIFs promote the activation of genes involved in cancer initiation, progression, and metastases. Hypoxia has been shown to enhance the invasiveness and metastatic potential of tumor cells by regulating the genes involved in the breakdown of the ECM as well as genes that control motility and adhesion of tumor cells. Using a Pten-deficient, Braf-mutant genetically engineered mouse model of melanoma, we demonstrated that inactivation of HIF1α or HIF2α abrogates metastasis without affecting primary tumor formation. HIF1α and HIF2α drive melanoma invasion and invadopodia formation through PDGFRα and focal adhesion kinase-mediated (FAK-mediated) activation of SRC and by coordinating ECM degradation via MT1-MMP and MMP2 expression. These results establish the importance of HIFs in melanoma progression and demonstrate that HIF1α and HIF2α activate independent transcriptional programs that promote metastasis by coordinately regulating cell invasion and ECM remodeling.

Twist1 induces CCL2 and recruits macrophages to promote angiogenesis

The transcription factor Twist1 induces epithelial-mesenchymal transition and extracellular matrix degradation to promote tumor metastasis. Although Twist1 also plays a role in embryonic vascular development and tumor angiogenesis, the molecular mechanisms that underlie these processes are not as well understood. Here, we report a novel function for Twist1 in modifying the tumor microenvironment to promote progression. We found that expression of Twist1 in human mammary epithelial cells potently promoted angiogenesis. Surprisingly, Twist1 expression did not increase the secretion of the common proangiogenic factors VEGF and basic fibroblast growth factor but rather induced expression of the macrophage chemoattractant CCL2. Attenuation of endogenous Twist1 in vivo blocked macrophage recruitment and angiogenesis, whereas exogenous CCL2 rescued the ability of tumor cells lacking Twist1 to attract macrophages and promote angiogenesis. Macrophage recruitment also was essential for the ability of Twist1-expressing cells to elicit a strong angiogenic response. Together, our findings show that how Twist1 recruits stromal macrophages through CCL2 induction to promote angiogenesis and tumor progression. As Twist1 expression has been associated with poor survival in many human cancers, this finding suggests that anti-CCL2 therapy may offer a rational strategy to treat Twist1-positive metastatic cancers.

Clinicopathological and prognostic significance of HIF-1α and HIF-2α expression in small cell lung cancer

Previous work from our laboratory has demonstrated that urokinase plasminogen activator receptor (uPAR) may be a potential stem-like cell marker in SCLC. Hypoxia inducible factor (HIF) has been shown to transcriptionally regulate uPAR expression. Therefore, the aim of this study was to evaluate the relationship between HIF-1α/HIF-2α and uPAR expression, and to investigate the role of HIF-1α/HIF-2α in the clinical pathology and prognosis of patients with SCLC. Immunohistochemical analysis showed that HIF-1α/HIF-2α staining was mainly present in the nuclei of cancer cells. HIF-1α-positive cells were diffusely distributed in the nests of the tumor, while HIF-2α-positive cells were frequently distributed around necrotic regions. HIF-1α and HIF-2α were expressed in 22/45 (48.9%) and in 11/45 (24.4%) of SCLC patients, respectively; HIF-1α did not correlate with any of the clinicopathological parameters as evaluated in our study. In contrast, a significant association of HIF-2α with uPAR expression, tumor growth and distant metastasis (p=0.001, 0.010 and 0.008, respectively) was noted; Kaplan-Meier survival analysis demonstrated that HIF-1α and HIF-2α expressions were related to shortened overall survival (p=0.027 and 0.001, respectively). However, in multivariate analysis, only HIF-2α expression and distant metastasis were the independent prognostic indicators of SCLC (p=0.004 and 0.018, respectively). Our results suggest that HIF-2α may represent a more aggressive phenotype in SCLC. HIF-2α, in addition to HIF-1α, needs to be considered when developing drugs that target HIF pathway.

CD133: holy of grail of neuro-oncology or promiscuous red-herring?

The CD133 glycoprotein is a controversial cancer stem cell marker in the field of neuro-oncology, based largely on the now considerable experimental evidence for the existence of both CD133+ve and CD133-ve populations as tumour-initiating cells. It is thought that decreasing oxygen tension enhances the complex regulation and phenotype of CD133 in glioma. In light of these ideologies, establishing the precise functional role of CD133 is becoming increasingly critical. In this article, we review the complex regulation of CD133 and its extracellular epitope AC133, and associated alterations, to tumour cell behaviour by hypoxia. Furthermore, its role in functional modulation of tumours, rather than determination of a specific stem cell type is therefore alluded to, while evidence for and against its ability as a cancer stem cell marker in primary brain tumours, is critically evaluated. Thus, the suggestion that CD133 may be a central 'holy grail' in identifying core cells for propagation of malignant glial neoplasms seems increasingly less convincing. It remains to be seen, however, whether CD133 is randomly expressed on such brain tumour cell populations or whether it is of major significance to brain biological behaviour.

Parasite neuropeptide biology: Seeding rational drug target selection?

The rationale for identifying drug targets within helminth neuromuscular signalling systems is based on the premise that adequate nerve and muscle function is essential for many of the key behavioural determinants of helminth parasitism, including sensory perception/host location, invasion, locomotion/orientation, attachment, feeding and reproduction. This premise is validated by the tendency of current anthelmintics to act on classical neurotransmitter-gated ion channels present on helminth nerve and/or muscle, yielding therapeutic endpoints associated with paralysis and/or death. Supplementary to classical neurotransmitters, helminth nervous systems are peptide-rich and encompass associated biosynthetic and signal transduction components - putative drug targets that remain to be exploited by anthelmintic chemotherapy. At this time, no neuropeptide system-targeting lead compounds have been reported, and given that our basic knowledge of neuropeptide biology in parasitic helminths remains inadequate, the short-term prospects for such drugs remain poor. Here, we review current knowledge of neuropeptide signalling in Nematoda and Platyhelminthes, and highlight a suite of 19 protein families that yield deleterious phenotypes in helminth reverse genetics screens. We suggest that orthologues of some of these peptidergic signalling components represent appealing therapeutic targets in parasitic helminths.

New insights into the regulation of epithelial-mesenchymal transition and tissue fibrosis

Tissue fibrosis often presents as the final outcome of chronic disease and is a significant cause of morbidity and mortality worldwide. Fibrosis is driven by continuous expansion of fibroblasts and myofibroblasts. Epithelial-mesenchymal transition (EMT) is a form of cell plasticity in which epithelia acquire mesenchymal phenotypes and is increasingly recognized as an integral aspect of tissue fibrogenesis. In this review, we describe recent insight into the molecular and cellular factors that regulate EMT and its underlying signaling pathways. We also consider how mechanical cues from the microenvironment affect the regulation of EMT. Finally, we discuss the role of EMT in fibrotic diseases and propose approaches for detecting and treating fibrogenesis by targeting EMT.

TWIST1 hypermethylation is observed in pancreatic cancer

Despite the growing evidence demonstrating that TWIST1 is a noteworthy tumor biomarker, little is known about the clinical significance of TWIST1 methylation in human primary pancreatic cancer. In the present study, the association of TWIST1 methylation with clinicopathological characteristics was examined in human primary pancreatic cancer. Primary pancreatic cancer specimens and corresponding healthy pancreatic non-tumorous tissues from 33 patients with pancreatic cancer were used. Methylation levels of TWIST1 were compared with clinicopathological characteristics. The TWIST1 methylation level was higher in pancreatic cancer compared to corresponding non-neoplastic pancreatic tissues. The mean TWIST1 methylation was 66.7% for pancreatic cancer tissue and 15.0% for corresponding nonneoplastic pancreatic tissue (P=0.0004). These results suggested that TWIST1 methylation is a useful biomarker for the screening of pancreatic cancers. Studies using independent data sets are required to confirm these findings.

The role of epithelial-mesenchymal transition in pancreatic cancer

Pancreatic cancer is the fourth leading cause of cancer related death in the US. Despite the advances in medical and surgical treatment, the 5-year survival rate for such cancer is only approximately 5% when considering all stages of disease. The lethal nature of pancreatic cancer stems from its high metastatic potential to the lymphatic system and distant organs. Lack of effective chemotherapies, which is believed to be due to drug-resistance, also contributes to the high mortality of pancreatic cancer. Recent evidence suggests that epithelial-mesenchymal transition of pancreatic cancer cells contributes to the development of drug resistance and an increase in invasiveness. Future strategies that specifically target against epithelial-mesenchymal transition phenotype could potentially reduce tumoral drug resistance and invasiveness and hence prolong the survival of patients with pancreatic cancer.

Attenuation of reactive oxygen species by antioxidants suppresses hypoxia-induced epithelial-mesenchymal transition and metastasis of pancreatic cancer cells

Hypoxia has been shown to promote metastasis of cancer cells through induction of epithelial-mesenchymal transition (EMT). It is also known to cause generation of reactive oxygen species (ROS). We investigated here the role of ROS in hypoxia-induced EMT and whether attenuation of ROS by antioxidants suppresses hypoxia-induced EMT and metastasis of human pancreatic cancer cells in a xenograft nude mouse model. PANC-1 and MiaPaCa-2 cells exposed to hypoxia (1 % O(2)) showed increased ROS generation and characteristic changes of EMT such as morphological changes, enhanced invasiveness, and upregulation of EMT regulators, SLUG, SNAI1 and TWIST. The antioxidants N-acetylcysteine (NAC) and ebselen significantly suppressed EMT and the expression of EMT regulators during hypoxia. NAC abrogated activation of HIF-1α and NF-κB, both of which were found to play an active role in hypoxia-induced EMT. Administration of NAC to nude mice with orthotopic tumors suppressed the expression of EMT regulators in hypoxic areas and significantly inhibited hepatic metastasis. Together, the present findings demonstrate that attenuation of ROS by antioxidants suppresses hypoxia-induced EMT and metastatic phenotype, suggesting that antioxidants may be of therapeutic value in treating pancreatic cancers.

EMT and stem cell-like properties associated with HIF-2α are involved in arsenite-induced transformation of human bronchial epithelial cells

BACKGROUND

Arsenic is well-established as a human carcinogen, but the molecular mechanisms leading to arsenic-induced carcinogenesis are complex and elusive. It is not been determined if the epithelial-mesenchymal transition (EMT) and stem cell-like properties contribute in causing to carcinogen-induced malignant transformation and subsequent tumor formation.

METHODS

To investigate the molecular mechanisms underlying EMT and the emergence of cancer stem cell-like properties during neoplastic transformation of human bronchial epithelial (HBE) cells induced by chronic exposure to arsenite. HBE cells were continuously exposed to arsenite. Spheroid formation assays and analyses of side populations (SPs) were performed to confirm that arsenite induces the acquired EMT and cancer stem cell-like phenotype. Treated HBE cells were molecularly characterized by RT-PCR, Western blots, immunofluorescence, Southwestern assays, reporter assays, and chromatin immunoprecipitation.

RESULTS

With chronic exposure to arsenite, HBE cells undergo an EMT and then acquire a malignant cancer stem cell-like phenotype. Twist1 and Bmi1 are involved in arsenite-induced EMT. The process is directly regulated by HIF-2α. The self-renewal genes, Oct4, Bmi1, and ALDH1, are necessary for arsenite-mediated maintenance of stem cells.

CONCLUSIONS

EMT, regulated by HIF-2α, and the development of a cancer stem cell-like phenotype are associated with arsenite-induced transformation of HBE cells.

CCN5/WISP-2: A micromanager of breast cancer progression

The gain of plasticity by a subset of cancer cells is a unique but common sequence of cancer progression from epithelial phenotype to mesenchymal phenotype (EMT) that is followed by migration, invasion and metastasis to a distant organ, and drug resistance. Despite multiple studies, it is still unclear how cancer cells regulate plasticity. Recent studies from our laboratory and others' proposed that CCN5/WISP-2, which is found intracellularly (in the nucleus and cytoplasm) and extracellularly, plays a negative regulator of plasticity. It prevents the EMT process in breast cancer cells as well as pancreatic cancer cells. Multiple genetic insults, including the gain of p53 mutations that accumulate over the time, may perturb CCN5 expression in non-invasive breast cancer cells, which ultimately helps cells to gain invasive phenotypes. Moreover, emerging evidence indicates that several oncogenic lesions such as miR-10b upregulation and activation of TGF-β-signaling can accumulate during CCN5 crisis in breast cancer cells. Collectively, these studies indicate that loss of CCN5 activity may promote breast cancer progression; application of CCN5 protein may represent a novel therapeutic intervention in breast cancer and possibly pancreatic cancer.

Constitutive proteasomal degradation of TWIST-1 in epithelial-ovarian cancer stem cells impacts differentiation and metastatic potential

Epithelial-mesenchymal transition (EMT) is a critical process for embryogenesis but is abnormally activated during cancer metastasis and recurrence. This process enables epithelial cancer cells to acquire mobility and traits associated with stemness. It is unknown whether epithelial stem cells or epithelial cancer stem cells are able to undergo EMT, and what molecular mechanism regulates this process in these specific cell types. We found that Epithelial Ovarian Cancer Stem cells (EOC stem cells) are the source of metastatic progenitor cells through a differentiation process involving EMT and Mesenchymal-Epithelial Transition (MET). We demonstrate both in vivo and in vitro the differentiation of EOC stem cells into mesenchymal spheroid-forming cells (MSFCs) and their capacity to initiate an active carcinomatosis. Furthermore, we demonstrate that human EOC stem cells injected i.p in mice are able to form ovarian tumors, suggesting that the EOC stem cells have the ability to “home” to the ovaries and establish tumors. Most interestingly, we found that TWIST1 is constitutively degraded in EOC stem cells, and that the acquisition of TWIST1 requires additional signals that will trigger the differentiation process. These findings are relevant for understanding the differentiation and metastasis process in EOC stem cells.

Hypoxia regulates glutamate receptor trafficking through an HIF-independent mechanism

Oxygen influences behaviour in many organisms, with low levels (hypoxia) having devastating consequences for neuron survival. How neurons respond physiologically to counter the effects of hypoxia is not fully understood. Here, we show that hypoxia regulates the trafficking of the glutamate receptor GLR-1 in C. elegans neurons. Either hypoxia or mutations in egl-9, a prolyl hydroxylase cellular oxygen sensor, result in the internalization of GLR-1, the reduction of glutamate-activated currents, and the depression of GLR-1-mediated behaviours. Surprisingly, hypoxia-inducible factor (HIF)-1, the canonical substrate of EGL-9, is not required for this effect. Instead, EGL-9 interacts with the Mint orthologue LIN-10, a mediator of GLR-1 membrane recycling, to promote LIN-10 subcellular localization in an oxygen-dependent manner. The observed effects of hypoxia and egl-9 mutations require the activity of the proline-directed CDK-5 kinase and the CDK-5 phosphorylation sites on LIN-10, suggesting that EGL-9 and CDK-5 compete in an oxygen-dependent manner to regulate LIN-10 activity and thus GLR-1 trafficking. Our findings demonstrate a novel mechanism by which neurons sense and respond to hypoxia.

A tale with a Twist: a developmental gene with potential relevance for metabolic dysfunction and inflammation in adipose tissue

The Twist proteins (Twist-1 and -2) are highly conserved developmental proteins with key roles for the transcriptional regulation in mesenchymal cell lineages. They belong to the super-family of bHLH proteins and exhibit bi-functional roles as both activators and repressors of gene transcription. The Twist proteins are expressed at low levels in adult tissues but may become abundantly re-expressed in cells undergoing malignant transformation. This observation prompted extensive research on the roles of Twist proteins in cancer progression and metastasis. Very recent studies indicate a novel role for Twist-1 as a potential regulator of adipose tissue (AT) remodeling and inflammation. Several studies suggested that developmental genes are important determinants of obesity, fat distribution and remodeling capacity of different adipose depots. Twist-1 is abundantly and selectively expressed in the adult AT and its constitutive expression is significantly higher in subcutaneous (SAT) vs. visceral (VAT) fat in both mice and humans. Moreover, Twist1 expression is strongly correlated with BMI and insulin resistance in humans. However, the functional roles and transcriptional downstream targets of Twist1 in AT are largely unexplored. The purpose of this review is to highlight the major findings related to Twist1 expression in different fat depots and cellular components of AT and to discuss the potential mechanisms suggesting a role for Twist1 in AT metabolism, inflammation and remodeling.

Advanced prostate cancer: reinforcing the strings between inflammation and the metastatic behavior

It is currently estimated that inflammatory responses are linked to 15-20% of all deaths from cancer worldwide. Although many studies point to an important role of inflammation in prostate growth, the contribution of inflammation to castration-resistant prostate cancer is not completely understood. The presence of inflammatory mediators in tumor microenvironment raises the question whether genetic events that participate in cancer development and progression are responsible for the inflammatory milieu inside and surrounding tumors. Activated oncogenes, cytokines, chemokines and their receptors, sustained oxidative stress and antioxidant imbalance share the capacity to orchestrate these pro-inflammatory programs; however, the diversity of the inflammatory cell components will determine the final response in the prostate tissue. These observations give rise to the concept that early genetic events generate an inflammatory microenvironment promoting prostate cancer progression and creating a continuous loop that stimulates a more aggressive stage. It is imperative to dissect the molecular pathologic mechanism of inflammation involved in the generation of the castration-resistant phenotype in prostate cancer. Here, we present a hypothesis where molecular signaling triggered by inflammatory mediators may evolve in prostate cancer progression. Thus, treatment of chronic inflammation may represent an important therapeutic target in advanced prostate cancer.

Coexpression of hypoxia-inducible factor-2α, TWIST2, and SIP1 may correlate with invasion and metastasis of salivary adenoid cystic carcinoma

BACKGROUND

Adenoid cystic carcinoma (ACC) of salivary gland is characterized by advanced local invasion and distant metastasis. Intratumoral hypoxia was reported to be associated with epithelial-mesenchymal transition (EMT) regulators. The purpose of this study was to evaluate the relationship between hypoxia-inducible factor (HIF)-2α, TWIST2, and SIP1 expression and the invasion and metastasis in ACC of salivary gland.

METHOD

In vitro we first detected the expression of HIF-2α, TWIST2, and SIP1 in two ACC cell lines by Western blot and real-time RT-PCR. Then, in vivo, a retrospective investigation of 121 patients with ACC from Department of Oral and Maxillofacial Surgery, West China Hospital of Stomatology, Sichuan University between 1996 and 2005 was carried out using immunohistochemistry to analyze the association between the expression of these three factors and clinical-pathological factors of patients.

RESULTS

The protein and mRNA levels of HIF-2α, TWIST2, and SIP1 in the high-metastasis cell line (ACC-M) were much higher than those of the low-metastasis cell line (ACC-2). The positive expression of HIF-2α, TWIST2, and SIP1 (71.07%, 42.98%, and 38.02%, respectively) was associated with the perineural invasion, the local recurrence, and distant metastasis of patients with ACC (P < 0.05). The patients with the positive coexpression of the three factors had a lower survival rate than those with the negative expression (P < 0.05).

CONCLUSION

It is proposed that the elevated expression of HIF-2α, TWIST2, and SIP1 can contribute to invasion and metastasis of ACC, and there might be some correlation between the hypoxia microenvironment and EMT in ACC.

ARTEMIN synergizes with TWIST1 to promote metastasis and poor survival outcome in patients with ER negative mammary carcinoma

Introduction

ARTEMIN (ARTN) is an estrogen regulated growth factor, the expression of which promotes resistance to antiestrogen therapies and predicts poorer survival outcome of patients with estrogen receptor (ER) positive mammary carcinoma (ER+MC) treated with tamoxifen. ARTN is also expressed in ER negative mammary carcinoma (ER-MC). Herein, we determined the role of ARTN in ER-MC and defined the mechanism of action producing poor patient prognosis.

Methods

We modulated the expression of ARTN in two ER- (mesenchymal/claudin-low) mammary carcinoma cell lines (BT549 and MDA-MB-231) by forced expression or small interfering RNA (siRNA) mediated depletion. The effects of modulation of ARTN expression were examined by various in vitro measures of oncogenicity, including the expression of TWIST1 messenger RNA (mRNA) and protein. In vitro results were correlated to xenograft studies in immunodeficient mice. Co-expression of ARTN and TWIST1 and their association to poor survival outcome were examined in a cohort of patients with ER-MC. Pathway analysis was performed by pharmacological inhibition of phosphorylation of AKT (pAKT-Ser 473) or modulation of TWIST1 expression.

Results

ARTN expression resulted in ER-MC cells with enhanced mesenchymal characteristics, including increased invasion and a gene expression profile consistent with enhanced mesenchymal phenotype. ARTN stimulated ER-MC cell anchorage independent and 3D matrigel growth, endothelial cell adhesion and transmigration of ER-MC cells through an endothelial cell barrier. Forced expression of ARTN produced a larger, locally invasive tumour mass with tumour emboli that produced distant metastasis. ARTN regulated TWIST1 expression in ER-MC cells and ARTN expression was significantly correlated to TWIST1 expression in a panel of mammary carcinoma cell lines and in a cohort of patients with ER-MC. Low expression of both ARTN and TWIST1 predicted 100% relapse free and overall survival in patients with ER-MC, whereas high expression of both ARTN and TWIST1 was associated with a poor survival outcome. ARTN stimulated an increase in TWIST1 expression via increased AKT activity. siRNA mediated depletion of TWIST1 abrogated ARTN stimulated cellular behaviour associated with metastasis, and forced expression of TWIST1 abrogated the functional effects of ARTN depletion.

Conclusions

ARTN and TWIST1 synergize to produce a worse outcome in ER-MC and combined inhibition of ARTN and phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) may therefore provide a novel therapeutic strategy in this subtype of mammary carcinoma.

The inflammatory tumor microenvironment, epithelial mesenchymal transition and lung carcinogenesis

The inflammatory tumor microenvironment (TME) has many roles in tumor progression and metastasis, including creation of a hypoxic environment, increased angiogenesis and invasion, changes in expression of microRNAs (miRNAs) and an increase in a stem cell phenotype. Each of these has an impact on epithelial mesenchymal transition (EMT), particularly through the downregulation of E-cadherin. Here we review seminal work and recent findings linking the role of inflammation in the TME, EMT and lung cancer initiation, progression and metastasis. Finally, we discuss the potential of targeting aspects of inflammation and EMT in cancer prevention and treatment.

Twist1 is up-regulated in gastric cancer-associated fibroblasts with poor clinical outcomes

Stromal fibroblasts perform important roles in cancer development and progression. Overexpression of Twist1, a basic helix-loop-helix transcription factor, is often associated with aggressive behavior in many tumors. In this study, we investigated Twist1 expression patterns in gastric stromal fibroblasts and cancer cells using a monoclonal Twist1 antibody after validating the effectiveness of four commercial Twist1-specific antibodies. Twist1 expression was more frequently observed in gastric cancer-associated fibroblasts (CAFs) than in other cancer cells but was otherwise rarely expressed in noncancerous tissue. In laser capture microdissection of stromal fibroblasts, Twist1 immunopositive fibroblasts exhibited significantly increased Twist1, fibroblast-specific protein 1, and CXCL14 mRNA expression. Furthermore, Twist1 mRNA expression showed a significant linear correlation with that of platelet-derived growth factor receptors β and α. We found that conditioned media from Twist1-expressing skin and lung fibroblasts significantly promote invasion of gastric cancer cells in vitro. In 195 gastric cancer samples, CAF Twist1 expression was associated with tumor size, invasion depth, and lymph node metastasis. Twist1 was also associated with poor prognosis in patients with gastric cancer, particularly in those with the diffuse type. In conclusion, CAFs in gastric cancer frequently have altered Twist1 expression, and increased Twist1 expression in fibroblasts contributes to the progression of cancer cells and poor patient survival.

E-Cadherin loss associated with EMT promotes radioresistance in human tumor cells

BACKGROUND AND PURPOSE

Hypoxia is a hallmark of solid cancers and associated with metastases and treatment failure. During tumor progression epithelial cells often acquire mesenchymal features, a phenomenon known as epithelial-to-mesenchymal transition (EMT). Intratumoral hypoxia has been linked to EMT induction. We hypothesized that signals from the tumor microenvironment such as growth factors and tumor oxygenation collaborate to promote EMT and thereby contribute to radioresistance.

MATERIALS AND METHODS

Gene expression changes under hypoxia were analyzed using microarray and validated by qRT-PCR. Conversion of epithelial phenotype upon hypoxic exposure, TGFβ addition or oncogene activation was investigated by Western blot and immunofluorescence. Cell survival following ionizing radiation was assayed using clonogenic survival.

RESULTS

Upon hypoxia, TGFβ addition or EGFRvIII expression, MCF7, A549 and NMuMG epithelial cells acquired a spindle shape and lost cell-cell contacts. Expression of epithelial markers such as E-cadherin decreased, whereas mesenchymal markers such as vimentin and N-cadherin increased. Combining hypoxia with TGFβ or EGFRvIII expression, lead to more rapid and pronounced EMT-like phenotype. Interestingly, E-cadherin expression and the mesenchymal appearance were reversible upon reoxygenation. Mesenchymal conversion and E-cadherin loss were associated with radioresistance.

CONCLUSIONS

Our findings describe a mechanism by which the tumor microenvironment may contribute to tumor radioresistance via E-cadherin loss and EMT.

C. elegans homologs of insect clock proteins: a tale of many stories

As a consequence of the Earth's axial rotation, organisms display daily recurring rhythms in behavior and biochemical properties, such as hormone titers. The neuronal system controlling such changes is best studied in the fruit fly Drosophila melanogaster. In the nematode worm Caenorhabditis elegans, most homologs of these genes function in the heterochronic pathway controlling the (timing of) developmental events. Recent data indicate that in the worm at least one of the genes involved in developmental timing is also active in circadian rhythm control, thereby opening up new perspectives on a central (neuronal) timer interfering with many processes. Also, new neuropeptidergic clock homologs have been identified in nematodes, supporting the idea of a broad range of clock-regulated targets. We will describe the current knowledge on homologous clock genes in C. elegans with a focus on the recently discovered pigment dispersing factor gene homologs. Similarities between developmental and daily timing are discussed.

Artificially induced epithelial-mesenchymal transition in surgical subjects: its implications in clinical and basic cancer research

Background

Surgical samples have long been used as important subjects for cancer research. In accordance with an increase of neoadjuvant therapy, biopsy samples have recently become imperative for cancer transcriptome. On the other hand, both biopsy and surgical samples are available for expression profiling for predicting clinical outcome by adjuvant therapy; however, it is still unclear whether surgical sample expression profiles are useful for prediction via biopsy samples, because little has been done about comparative gene expression profiling between the two kinds of samples.

Methodology and Findings

A total of 166 samples (77 biopsy and 89 surgical) of normal and malignant lesions of the esophagus were analyzed by microarrays. Gene expression profiles were compared between biopsy and surgical samples. Artificially induced epithelial-mesenchymal transition (aiEMT) was found in the surgical samples, and also occurred in mouse esophageal epithelial cell layers under an ischemic condition. Identification of clinically significant subgroups was thought to be disrupted by the disorder of the expression profile through this aiEMT.

Conclusion and Significance

This study will evoke the fundamental misinterpretation including underestimation of the prognostic evaluation power of markers by overestimation of EMT in past cancer research, and will furnish some advice for the near future as follows: 1) Understanding how long the tissues were under an ischemic condition. 2) Prevalence of biopsy samples for in vivo expression profiling with low biases on basic and clinical research. 3) Checking cancer cell contents and normal- or necrotic-tissue contamination in biopsy samples for prevalence.

Oxygen homeostasis

Metazoan life is dependent upon the utilization of O(2) for essential metabolic processes and oxygen homeostasis is an organizing principle for understanding metazoan evolution, ontology, physiology, and pathology. Hypoxia-inducible factor 1 (HIF-1) is a transcription factor that is expressed by all metazoan species and functions as a master regulator of oxygen homeostasis. Recent studies have elucidated complex mechanisms by which HIF-1 activity is regulated and by which HIF-1 regulates gene expression, with profound consequences for prenatal development, postnatal physiology, and disease pathogenesis.

Hypoxia-inducible factor-1 alpha, in association with TWIST2 and SNIP1, is a critical prognostic factor in patients with tongue squamous cell carcinoma

It has become apparent that hypoxia and hypoxia-inducible factor-1 (HIF-1) activation have the potential of modulating the activity of major epithelial-mesenchymal transition (EMT)-triggering pathways by regulating the expression and activity levels of major transcriptional repressors. The aim of our study was to elucidate the role of HIF-1α and HIF-2α, and EMT regulators TWIST2 and SMAD nuclear interacting protein-1 (SNIP1) in tongue squamous cell carcinoma (TSCC). A retrospective analysis of 89 patients with TSCC from Department of Oral and Maxillofacial Surgery, West China Hospital of Stomatology, Sichuan University between 2002 and 2005 was performed using immunohistochemistry in paraffin-embedded and formalin-fixed tissues to analyze HIF-1α, HIF-2α, TWIST2 and SNIP1 expression. The association between HIF-1α, HIF-2α, TWIST2 and SNIP1 expression and patient survivals was investigated. Our results showed that overexpression of HIF-1α, HIF-2α, TWIST2 and SNIP1 were shown in 49.44% (44/89), 55.06% (49/89), 44.94% (40/89) and 34.83% (31/89) of TSCC, respectively. Overexpression of HIF-1α, TWIST2 and SNIP1 in TSCC was associated with a shorter disease-free survival (P=0.003, P=0.001, P=0.040, respectively), and HIF-2α had no significant association with either overall survival (P=0.195) or disease-free survival (P=0.356). Co-expression of more than two markers of HIF-1α, TWIST2 and SNIP1 was an independent prognostic indicator for both overall survival and disease-free survival by multivariate Cox proportional hazards model. It is proposed that co-expression of more than two markers from HIF-1α, TWIST2 and SNIP1 might be a significant prognostic predictor in patients with TSCC.

C. elegans twist gene expression in differentiated cell types is controlled by autoregulation through intron elements

The temporospatial regulation of genes encoding transcription factors is important during development. The hlh-8 gene encodes the C. elegans mesodermal transcription factor CeTwist. Elements in the hlh-8 promoter restrict gene expression to predominantly undifferentiated cells of the M lineage. We have discovered that hlh-8 expression in differentiated mesodermal cells is controlled by two well-conserved E box elements in the large first intron. Additionally, we found that these elements are bound in vitro by CeTwist and its transcription factor partner, CeE/DA. The E box driven expression is eliminated or diminished in an hlh-8 null allele or in hlh-2 (CeE/DA) RNAi, respectively. Expression of hlh-8 is also diminished in animals harboring an hlh-8 intron deletion allele. Altogether, our results support a model in which hlh-8 is initially expressed in the undifferentiated M lineage cells via promoter elements and then the CeTwist activates its own expression further (autoregulation) in differentiated cells derived from the M lineage via the intron elements. This model provides a mechanism for how a transcription factor may regulate distinct target genes in cells both before and after initiating the differentiation program. The findings could also be relevant to understanding human Twist gene regulation, which is currently not well understood.

Suppression of Her2/neu expression through ILK inhibition is regulated by a pathway involving TWIST and YB-1

In a previous study it was found that the therapeutic effects of QLT0267, a small molecule inhibitor of integrin-linked kinase (ILK), were influenced by Her2/neu expression. To understand how inhibition or silencing of ILK influences Her2/neu expression, Her2/neu signaling was evaluated in six Her2/neu-positive breast cancer cell lines (LCC6^Her2, MCF7^Her2, SKBR3, BT474, JIMT-1 and KPL-4). Treatment with QLT0267 engendered suppression (32–87%) of total Her2/neu protein in these cells. Suppression of Her2/neu was also observed following small interfering RNA-mediated silencing of ILK expression. Time course studies suggest that ILK inhibition or silencing caused transient decreases in P-AKT^ser473, which were not temporally related to Her2/neu downregulation. Attenuation of ILK activity or expression was, however, associated with decreases in YB-1 (Y-box binding protein-1) protein and transcript levels. YB-1 is a known transcriptional regulator of Her2/neu expression, and in this study it is demonstrated that inhibition of ILK activity using QLT0267 decreased YB-1 promoter activity by 50.6%. ILK inhibition was associated with changes in YB-1 localization, as reflected by localization of cytoplasmic YB-1 into stress granules. ILK inhibition also suppressed TWIST (a regulator of YB-1 expression) protein expression. To confirm the role of ILK on YB-1 and TWIST, cells were engineered to overexpress ILK. This was associated with a fourfold increase in the level of YB-1 in the nucleus, and a 2- and 1.5-fold increase in TWIST and Her2/neu protein levels, respectively. Taken together, these data indicate that ILK regulates the expression of Her2/neu through TWIST and YB-1, lending support to the use of ILK inhibitors in the treatment of aggressive Her2/neu-positive tumors.

Hypoxia-inducible factors--regulation, role and comparative aspects in tumourigenesis

Hypoxia-inducible factors (HIFs) play a key role in the cellular response experienced in hypoxic tumours, mediating adaptive responses that allow hypoxic cells to survive in the hostile environment. Identification and understanding of tumour hypoxia and the influence on cellular processes carries important prognostic information and may help identify potential hypoxia circumventing and targeting strategies. This review summarizes current knowledge on HIF regulation and function in tumour cells and discusses the aspects of using companion animals as comparative spontaneous cancer models. Spontaneous tumours in companion animals hold a great research potential for the evaluation and understanding of tumour hypoxia and in the development of hypoxia-targeting therapeutics.

Genome-wide analysis reveals novel genes essential for heme homeostasis in Caenorhabditis elegans

Heme is a cofactor in proteins that function in almost all sub-cellular compartments and in many diverse biological processes. Heme is produced by a conserved biosynthetic pathway that is highly regulated to prevent the accumulation of heme—a cytotoxic, hydrophobic tetrapyrrole. Caenorhabditis elegans and related parasitic nematodes do not synthesize heme, but instead require environmental heme to grow and develop. Heme homeostasis in these auxotrophs is, therefore, regulated in accordance with available dietary heme. We have capitalized on this auxotrophy in C. elegans to study gene expression changes associated with precisely controlled dietary heme concentrations. RNA was isolated from cultures containing 4, 20, or 500 µM heme; derived cDNA probes were hybridized to Affymetrix C. elegans expression arrays. We identified 288 heme-responsive genes (hrgs) that were differentially expressed under these conditions. Of these genes, 42% had putative homologs in humans, while genomes of medically relevant heme auxotrophs revealed homologs for 12% in both Trypanosoma and Leishmania and 24% in parasitic nematodes. Depletion of each of the 288 hrgs by RNA–mediated interference (RNAi) in a transgenic heme-sensor worm strain identified six genes that regulated heme homeostasis. In addition, seven membrane-spanning transporters involved in heme uptake were identified by RNAi knockdown studies using a toxic heme analog. Comparison of genes that were positive in both of the RNAi screens resulted in the identification of three genes in common that were vital for organismal heme homeostasis in C. elegans. Collectively, our results provide a catalog of genes that are essential for metazoan heme homeostasis and demonstrate the power of C. elegans as a genetic animal model to dissect the regulatory circuits which mediate heme trafficking in both vertebrate hosts and their parasites, which depend on environmental heme for survival.

Heme is an iron-containing cofactor for proteins involved in many critical cellular processes. However, free heme is toxic to cells, suggesting that heme synthesis, acquisition, and transport is highly regulated. Efforts to understand heme trafficking in multicellular organisms have failed primarily due to the inability to separate the processes of endogenous heme synthesis from heme uptake and transport. Caenorhabditis elegans is unique among model organisms because it cannot synthesize heme but instead eats environmental heme to grow and develop normally. Thus, worms are an ideal genetic animal model to study heme homeostasis. This work identifies a novel list of 288 heme-responsive genes (hrgs) in C. elegans and a number of related genes in humans and medically relevant parasites. Knocking down the function of each of these hrgs reveals roles for several in heme uptake, transport, and detection within the organism. Our study provides insights into metazoan regulation of organismal heme homeostasis. The identification of parasite-specific hrg homologs may permit the selective design and screening of drugs that specifically target heme uptake pathways in parasites without affecting the host. Thus, this work has therapeutic implications for the treatment of human iron deficiency, one of the top ten mortality factors world-wide.

Hypoxia signaling and resistance in C. elegans

In normal development and homeostasis and in many disease states, cells and tissues must overcome the challenge of oxygen deprivation (hypoxia). The nematode C. elegans is emerging as an increasingly powerful system in which to understand how animals adapt to moderate hypoxia and survive extreme hypoxic insults. This review provides an overview of C. elegans responses to hypoxia, ranging from adaptation and arrest to death, and highlights some of the recent studies that have provided important insights into hypoxia signaling and resistance. Many of the key genes and pathways are evolutionarily conserved, and C. elegans hypoxia research promises to inform our understanding of oxygen-sensitive signaling and survival in mammalian development and disease.

TWIST1 hypermethylation is observed frequently in colorectal tumors and its overexpression is associated with unfavorable outcomes in patients with colorectal cancer

Although growing evidence demonstrates that TWIST1 is an interesting tumor biomarker, little is known about the clinical significance of TWIST1 expression and TWIST1 methylation in human primary colorectal cancer. In this study, we examined the association of TWIST1 expression and TWIST1 methylation with clinicopathologic features in human primary colorectal tumors. Primary colorectal cancer (CRC) specimens from 319 patients, corresponding normal colorectal nontumorous mucosa from 251 patients with cancer, and colorectal adenomas from 189 patients were used. Methylation and expression levels of TWIST1 were compared with clinicopathologic features. The TWIST1 methylation level was higher in colorectal adenoma and cancer than in normal colorectal mucosa. Elevated TWIST1 mRNA expression in normal colorectal mucosa in patients with CRC as well as in primary CRC specimens was associated with unfavorable outcomes. There was no correlation between TWIST1 methylation and TWIST1 expression. Our results suggest that TWIST1 methylation may be a useful biomarker for screening colorectal tumors. In addition, TWIST1 mRNA expression is a possible molecular marker for predicting the outcome in patients with CRC. Confirmatory studies using independent data sets are needed to confirm our findings.

COMMD1 disrupts HIF-1alpha/beta dimerization and inhibits human tumor cell invasion

The gene encoding COMM domain-containing 1 (COMMD1) is a prototypical member of the COMMD gene family that has been shown to inhibit both NF-kappaB- and HIF-mediated gene expression. NF-kappaB and HIF are transcription factors that have been shown to play a role in promoting tumor growth, survival, and invasion. In this study, we demonstrate that COMMD1 expression is frequently suppressed in human cancer and that decreased COMMD1 expression correlates with a more invasive tumor phenotype. We found that direct repression of COMMD1 in human cell lines led to increased tumor invasion in a chick xenograft model, while increased COMMD1 expression in mouse melanoma cells led to decreased lung metastasis in a mouse model. Decreased COMMD1 expression also correlated with increased expression of genes known to promote cancer cell invasiveness, including direct targets of HIF. Mechanistically, our studies show that COMMD1 inhibits HIF-mediated gene expression by binding directly to the amino terminus of HIF-1alpha, preventing its dimerization with HIF-1beta and subsequent DNA binding and transcriptional activation. Altogether, our findings demonstrate a role for COMMD1 in tumor invasion and provide a detailed mechanism of how this factor regulates the HIF pathway in cancer cells.

Hypoxia modulates EWS-FLI1 transcriptional signature and enhances the malignant properties of Ewing's sarcoma cells in vitro

Hypoxia is an important condition in the tumor cell microenvironment and approximately 1% to 1.5% of the genome is transcriptionally responsive to hypoxia with hypoxia-inducible factor-1 (HIF-1) as a major mediator of transcriptional activation. Tumor hypoxia is associated with a more aggressive phenotype of many cancers in adults, but data on pediatric tumors are scarce. Because, by immunohistochemistry, HIF-1alpha expression was readily detectable in 18 of 28 primary Ewing's sarcoma family tumors (ESFT), a group of highly malignant bone-associated tumors in children and young adults, we studied the effect of hypoxia on ESFT cell lines in vitro. Intriguingly, we found that EWS-FLI1 protein expression, which characterizes ESFT, is upregulated by hypoxia in a HIF-1alpha-dependent manner. Hypoxia modulated the EWS-FLI1 transcriptional signature relative to normoxic conditions. Both synergistic as well as antagonistic transcriptional effects of EWS-FLI1 and of hypoxia were observed. Consistent with alterations in the expression of metastasis-related genes, hypoxia stimulated the invasiveness and soft agar colony formation of ESFT cells in vitro. Our data represent the first transcriptome analysis of hypoxic ESFT cells and identify hypoxia as an important microenvironmental factor modulating EWS-FLI1 expression and target gene activity with far-reaching consequences for the malignant properties of ESFT.

TWISTing an embryonic transcription factor into an oncoprotein

Over the past decade, the reactivation of TWIST embryonic transcription factors has been described as a frequent event and a marker of poor prognosis in an impressive array of human cancers. Growing evidence now supports the premise that these cancers hijack TWIST's embryonic functions, granting oncogenic and metastatic properties. In this review, we report on the history and recent breakthroughs in understanding TWIST protein functions and the emerging role of the associated epithelial-mesenchymal transition (EMT) in tumorigenesis. We then broaden the discussion to address the general contribution of reactivating embryonic programs in cancerogenesis.

Fatty acid composition and gene expression profiles are altered in aryl hydrocarbon receptor-1 mutant Caenorhabditis elegans

The aryl hydrocarbon receptor (AHR) is a eukaryotic transcription factor that plays an essential role in neuronal, immune, vascular, hepatic and hematopoietic development. In mammals, AHR induces metabolism-associated genes in response to xenobiotics. AHR is evolutionarily conserved, and the C. elegans AHR ortholog likely shares many physiologic functions with the mammalian version. While the role of AHR in development is known, the molecular basis of AHR action is less well understood. To understand the physiologic role of AHR in C. elegans, a combination of fatty acid profiling, transcriptomics, and phenotyping approaches was used. Fatty acid profiles from L4 larval stage whole animals indicated that C17isoA, C18:1n9t, C20:3n6 and C20:4n6 were significantly increased in an ahr-1 mutant compared to wild-type. Consistent with these changes, we observed a significant 5.8 fold increase in fat-7, and 1.7-1.9 fold increases in elo-5, nhr-49, and mdt-15 gene expression during the L4 stage. The ahr-1(ju145) mutant displayed deficits in growth and development including a reduced number of eggs laid, a higher proportion of dead embryos, delay in time to reach L4 stage, and movement deficits including a fewer number of body bends and a longer defecation cycle. To understand global effects of AHR-1 on transcription, microarray analysis was performed on L1 stage animals. Expression changes (324 under- and 238 over-expressed) were found in genes associated with metabolism, growth, and development. These results indicate a role for C. elegans AHR in regulating fatty acid composition and in contributing to some aspects of development. Since the transcriptional control of AHR targets may be evolutionarily conserved, these results provide a deeper understanding of the molecular actions of AHR in a model invertebrate system that may be informative for higher organisms.

The lysyl oxidases LOX and LOXL2 are necessary and sufficient to repress E-cadherin in hypoxia: insights into cellular transformation processes mediated by HIF-1

Hypoxia has been shown to promote tumor metastasis and lead to therapy resistance. Recent work has demonstrated that hypoxia represses E-cadherin expression, a hallmark of epithelial to mesenchymal transition, which is believed to amplify tumor aggressiveness. The molecular mechanism of E-cadherin repression is unknown, yet lysyl oxidases have been implicated to be involved. Gene expression of lysyl oxidase (LOX) and the related LOX-like 2 (LOXL2) is strongly induced by hypoxia. In addition to the previously demonstrated LOX, we characterize LOXL2 as a direct transcriptional target of HIF-1. We demonstrate that activation of lysyl oxidases is required and sufficient for hypoxic repression of E-cadherin, which mediates cellular transformation and takes effect in cellular invasion assays. Our data support a molecular pathway from hypoxia to cellular transformation. It includes up-regulation of HIF and subsequent transcriptional induction of LOX and LOXL2, which repress E-cadherin and induce epithelial to mesenchymal transition. Lysyl oxidases could be an attractive molecular target for cancers of epithelial origin, in particular because they are partly extracellular.

RNF4 and VHL regulate the proteasomal degradation of SUMO-conjugated Hypoxia-Inducible Factor-2alpha

Hypoxia-inducible factors (HIFs) are critical transcription factors that mediate cell survival during reduced oxygen conditions (hypoxia). At regular oxygen conditions (normoxia), HIF-1alpha and HIF-2alpha are continuously synthesized in cells and degraded via the ubiquitin-proteasome pathway. During hypoxia, these proteins are stabilized and translocate to the nucleus to activate transcription of target genes that enable cell survival at reduced oxygen levels. HIF proteins are tightly regulated via post-translational modifications including phosphorylation, acetylation, prolyl-hydroxylation and ubiquitination. Here we show for the first time that exogenous and endogenous HIF-2alpha are also regulated via the ubiquitin-like modifier small ubiquitin-like modifiers (SUMO). Using mutational analysis, we found that K394, which is situated in the sumoylation consensus site LKEE, is the major SUMO acceptor site in HIF-2alpha. Functionally, sumoylation reduced the transcriptional activity of HIF-2alpha. Similar to HIF-1alpha, HIF-2alpha is regulated by the SUMO protease SENP1. The proteasome inhibitor MG132 strongly stabilized SUMO-2-conjugated HIF-2alpha during hypoxia but did not affect the total level of HIF-2alpha. The ubiquitin E3 ligases von Hippel-Lindau and RNF4 control the levels of sumoylated HIF-2alpha, indicating that sumoylated HIF-2alpha is degraded via SUMO-targeted ubiquitin ligases.

Identification and characterization of a putative basic helix-loop-helix (bHLH) transcription factor interacting with calcineurin in C. elegans

Calcineurin is a Ca(2+)/Calmodulin activated Ser/Thr phosphatase that is well conserved from yeast to human. It is composed of catalytic subunit A (CnA) and regulatory subunit B (CnB). C. elegans homolog of CnA and CnB has been annotated to tax-6 and cnb-1, respectively and in vivo function of both genes has been intensively studied. In C. elegans, calcineurin play roles in various signaling pathways such as fertility, movement, body size regulation and serotonin-mediated egg laying. In order to understand additional signaling pathway(s) in which calcineurin functions, we screened for binding proteins of TAX-6 and found a novel binding protein, HLH-11. The HLH-11, a member of basic helix-loop-helix (bHLH) proteins, is a putative counterpart of human AP4 transcription factor. Previously bHLH transcription factors have been implicated to regulate many developmental processes such as cell proliferation and differentiation, sex determination and myogenesis. However, the in vivo function of hlh-11 is largely unknown. Here, we show that hlh-11 is expressed in pharynx, intestine, nerve cords, anal depressor and vuvla muscles where calcineurin is also expressed. Mutant analyses reveal that hlh-11 may have role(s) in regulating body size and reproduction. More interestingly, genetic epistasis suggests that hlh-11 may function to regulate serotonin-mediated egg laying at the downstream of tax-6.

From polyps to people: a highly familiar response to hypoxia

Obligate aerobes, by definition, require oxygen in order to sustain life. Therefore, changes in environment or physiology that cause metabolic demand for oxygen to exceed supply (hypoxia) can be highly detrimental. Despite considerable variation in physiology and habitat between species, a majority of metazoa employ homologues of the hypoxia-inducible factor (HIF) transcription factors to adapt to oxygen deprivation. Studies in mammals, Drosophila and C. elegans have shown that regulation of HIF-alpha by prolyl hydroxylase (PHD)-mediated proteasomal degradation is conserved, as are a number of HIF target genes. More recently, analysis of coral and beetle HIFs has revealed that, unlike flies and worms, the C-terminal transactivation domain of HIF-alpha and its regulatory hydroxylase FIH-1 are also preserved. The reasons for variable conservation of this system are unknown. However, discovery of the "intermediary" properties of the beetle HIF pathway may prove a useful tool to better define HIF signaling in both mammals and invertebrates.

Pathophysiological Consequences of HIF Activation: HIF as a modulator of fibrosis

Tissue fibrosis is associated with structural and functional changes that limit blood flow and oxygen availability. In the kidney, tubulointerstitial fibrosis, which leads to progressive destruction of renal tissue and irreversible loss of kidney function, is associated with reduced tissue oxygen levels and activation of hypoxia-inducible factor (HIF) signaling. Although cytoprotective in acute injury models, HIF-1 was found to promote fibrosis in an experimental model of chronic renal injury following unilateral ureteral obstruction. Pharmacological inhibition of lysyl oxidases phenocopied the effects of genetic HIF-1 ablation on cell motility in vitro and on fibrogenesis in vivo, suggesting that lysyl oxidases are important mediators of profibrotic HIF signaling. These findings support the notion that HIF-mediated cellular responses differ under conditions of acute and chronic oxygen deprivation. Under certain conditions, these responses may lead to further tissue destruction by promoting fibrogenesis.

Two distinct roles for EGL-9 in the regulation of HIF-1-mediated gene expression in Caenorhabditis elegans

Oxygen is critically important to metazoan life, and the EGL-9/PHD enzymes are key regulators of hypoxia (low oxygen) response. When oxygen levels are high, the EGL-9/PHD proteins hydroxylate hypoxia-inducible factor (HIF) transcription factors. Once hydroxylated, HIFalpha subunits bind to von Hippel-Lindau (VHL) E3 ligases and are degraded. Prior genetic analyses in Caenorhabditis elegans had shown that EGL-9 also acted through a vhl-1-independent pathway to inhibit HIF-1 transcriptional activity. Here, we characterize this novel EGL-9 function. We employ an array of complementary methods to inhibit EGL-9 hydroxylase activity in vivo. These include hypoxia, hydroxylase inhibitors, mutation of the proline in HIF-1 that is normally modified by EGL-9, and mutation of the EGL-9 catalytic core. Remarkably, we find that each of these treatments or mutations eliminates oxygen-dependent degradation of HIF-1 protein, but none of them abolishes EGL-9-mediated repression of HIF-1 transcriptional activity. Further, analyses of new egl-9 alleles reveal that the evolutionarily conserved EGL-9 MYND zinc finger domain does not have a major role in HIF-1 regulation. We conclude that C. elegans EGL-9 is a bifunctional protein. In addition to its well-established role as the oxygen sensor that regulates HIF-1 protein levels, EGL-9 inhibits HIF-1 transcriptional activity via a pathway that has little or no requirement for hydroxylase activity or for the EGL-9 MYND domain.

HIF2alpha cooperates with RAS to promote lung tumorigenesis in mice

Members of the hypoxia-inducible factor (HIF) family of transcription factors regulate the cellular response to hypoxia. In non-small cell lung cancer (NSCLC), high HIF2alpha levels correlate with decreased overall survival, and inhibition of either the protein encoded by the canonical HIF target gene VEGF or VEGFR2 improves clinical outcomes. However, whether HIF2alpha is causal in imparting this poor prognosis is unknown. Here, we generated mice that conditionally express both a nondegradable variant of HIF2alpha and a mutant form of Kras (KrasG12D) that induces lung tumors. Mice expressing both Hif2a and KrasG12D in the lungs developed larger tumors and had an increased tumor burden and decreased survival compared with mice expressing only KrasG12D. Additionally, tumors expressing both KrasG12D and Hif2a were more invasive, demonstrated features of epithelial- mesenchymal transition (EMT), and exhibited increased angiogenesis associated with mobilization of circulating endothelial progenitor cells. These results implicate HIF2alpha causally in the pathogenesis of lung cancer in mice, demonstrate in vivo that HIF2alpha can promote expression of markers of EMT, and define HIF2alpha as a promoter of tumor growth and progression in a solid tumor other than renal cell carcinoma. They further suggest a possible causal relationship between HIF2alpha and prognosis in patients with NSCLC.

Emerging role of nuclear protein 1 (NUPR1) in cancer biology

NUPR1, or p8 or com1, was first identified from rat pancreas during acute pancreatitis and later as a gene whose expression was upregulated in metastatic breast cancer cells. NUPR1 is a molecule whose expression is upregulated in response to stress and is hence influenced by the host microenvironment. While NUPR1 has been implicated in several diseases, there is no singular biochemical pathway that can be attributed to its role in cancer. NUPR1 has been found to aid the establishment of metastasis and to play a key role in the progression of several malignancies including those of breast, thyroid, brain and pancreas. NUPR1 has been implicated in inducing chemoresistance in pancreatic and breast cancer cells, protecting them from apoptosis and making tumor cells genetically unstable. In prostate cancer, however, NUPR1 appears to have tumor suppressive activity. Understanding the mechanism of action of the multifaceted functions of NUPR1 may open up new dimensions towards creating novel therapies against cancer as well as other pathologies. This review draws on several published studies on NUPR1, mainly in cancer biology, and assesses NUPR1 from the perspective of its functional role in making cancer cells resistant to the action of conventional chemotherapeutic drugs.

The HIF-1 hypoxia-inducible factor modulates lifespan in C. elegans

During normal development or during disease, animal cells experience hypoxic (low oxygen) conditions, and the hypoxia-inducible factor (HIF) transcription factors implement most of the critical changes in gene expression that enable animals to adapt to this stress. Here, we examine the roles of HIF-1 in post-mitotic aging. We examined the effects of HIF-1 over-expression and of hif-1 loss-of-function mutations on longevity in C. elegans, a powerful genetic system in which adult somatic cells are post-mitotic. We constructed transgenic lines that expressed varying levels of HIF-1 protein and discovered a positive correlation between HIF-1 expression levels and lifespan. The data further showed that HIF-1 acted in parallel to the SKN-1/NRF and DAF-16/FOXO transcription factors to promote longevity. HIF-1 over-expression also conferred increased resistance to heat and oxidative stress. We isolated and characterized additional hif-1 mutations, and we found that each of 3 loss-of-function mutations conferred increased longevity in normal lab culture conditions, but, unlike HIF-1 over-expression, a hif-1 deletion mutation did not extend the lifespan of daf-16 or skn-1 mutants. We conclude that HIF-1 over-expression and hif-1 loss-of-function mutations promote longevity by different pathways. These data establish HIF-1 as one of the key stress-responsive transcription factors that modulate longevity in C. elegans and advance our understanding of the regulatory networks that link oxygen homeostasis and aging.