Identification of pY654-β-catenin as a critical co-factor in hypoxia-inducible factor-1α signaling and tumor responses to hypoxia

NOX1 and PRDX6 synergistically support migration and invasiveness of hepatocellular carcinoma cells through enhanced NADPH oxidase activity

The NADPH oxidase 1 (NOX1) complex formed by proteins NOX1, p22phox, NOXO1, NOXA1, and RAC1 plays an important role in the generation of superoxide and other reactive oxygen species (ROS) which are involved in normal and pathological cell functions due to their effects on diverse cell signaling pathways. Cell migration and invasiveness are at the origin of tumor metastasis during cancer progression which involves a process of cellular de-differentiation known as the epithelial-mesenchymal transition (EMT). During EMT cells lose their polarized epithelial phenotype and express mesenchymal marker proteins that enable cytoskeletal rearrangements promoting cell migration, expression and activation of matrix metalloproteinases (MMPs), tissue remodeling, and cell invasion during metastasis. In this work, we explored the importance of the peroxiredoxin 6 (PRDX6)-NOX1 enzyme interaction leading to NOXA1 protein stabilization and increased levels of superoxide produced by NOX in hepatocarcinoma cells. This increase was accompanied by higher levels of N-cadherin and MMP2, correlating with a greater capacity for cell migration and invasiveness of SNU475 hepatocarcinoma cells. The increase in superoxide and the associated downstream effects on cancer progression were suppressed when phospholipase A2 or peroxidase activities of PRDX6 were abolished by site-directed mutagenesis, reinforcing the importance of these catalytic activities in supporting NOX1-based superoxide generation. Overall, these results demonstrate a clear functional cooperation between NOX1 and PRDX6 catalytic activities which generate higher levels of ROS production, resulting in a more aggressive tumor phenotype.

WNT/β-catenin pathway is a key regulator of cardiac function and energetic metabolism

The WNT/β-catenin pathway is a master regulator of cardiac development and growth, and its activity is low in healthy adult hearts. However, even this low activity is essential for maintaining normal heart function. Acute activation of the WNT/β-catenin signaling cascade is considered to be cardioprotective after infarction through the upregulation of prosurvival genes and reprogramming of metabolism. Chronically high WNT/β-catenin pathway activity causes profibrotic and hypertrophic effects in the adult heart. New data suggest more complex functions of β-catenin in metabolic maturation of the perinatal heart, establishing an adult pattern of glucose and fatty acid utilization. Additionally, low basal activity of the WNT/β-catenin cascade maintains oxidative metabolism in the adult heart, and this pathway is reactivated by physiological or pathological stimuli to meet the higher energy needs of the heart. This review summarizes the current state of knowledge of the organization of canonical WNT signaling and its function in cardiogenesis, heart maturation, adult heart function, and remodeling. We also discuss the role of the WNT/β-catenin pathway in cardiac glucose, lipid metabolism, and mitochondrial physiology.

A reversible SRC-relayed COX2 inflammatory program drives resistance to BRAF and EGFR inhibition in BRAFV600E colorectal tumors

BRAF^V600E mutation confers a poor prognosis in metastatic colorectal cancer (CRC) despite combinatorial targeted therapies based on the latest understanding of signaling circuitry. To identify parallel resistance mechanisms induced by BRAF-MEK-EGFR co-targeting, we used a high-throughput kinase activity mapping platform. Here we show that SRC kinases are systematically activated in BRAF^V600E CRC following targeted inhibition of BRAF ± EGFR and that coordinated targeting of SRC with BRAF ± EGFR increases treatment efficacy in vitro and in vivo. SRC drives resistance to BRAF ± EGFR targeted therapy independently of ERK signaling by inducing transcriptional reprogramming through β-catenin (CTNNB1). The EGFR-independent compensatory activation of SRC kinases is mediated by an autocrine prostaglandin E₂ loop that can be blocked with cyclooxygenase-2 (COX2) inhibitors. Co-targeting of COX2 with BRAF + EGFR promotes durable suppression of tumor growth in patient-derived tumor xenograft models. COX2 inhibition represents a drug-repurposing strategy to overcome therapeutic resistance in BRAF^V600E CRC.

Phosphorylation-Dependent Regulation of WNT/Beta-Catenin Signaling

WNT/β-catenin signaling is a highly complex pathway that plays diverse roles in various cellular processes. While WNT ligands usually signal through their dedicated Frizzled receptors, the decision to signal in a β-catenin-dependent or -independent manner rests upon the type of co-receptors used. Canonical WNT signaling is β-catenin-dependent, whereas non-canonical WNT signaling is β-catenin-independent according to the classical definition. This still holds true, albeit with some added complexity, as both the pathways seem to cross-talk with intertwined networks that involve the use of different ligands, receptors, and co-receptors. β-catenin can be directly phosphorylated by various kinases governing its participation in either canonical or non-canonical pathways. Moreover, the co-activators that associate with β-catenin determine the output of the pathway in terms of induction of genes promoting proliferation or differentiation. In this review, we provide an overview of how protein phosphorylation controls WNT/β-catenin signaling, particularly in human cancer.

Development and Validation of an Mesenchymal-Related Long Non-Coding RNA Prognostic Model in Glioma

Glioma is well known as the most aggressive and prevalent primary malignant tumor in the central nervous system. Molecular subtypes and prognosis biomarkers remain a promising research area of gliomas. Notably, the aberrant expression of mesenchymal (MES) subtype related long non-coding RNAs (lncRNAs) is significantly associated with the prognosis of glioma patients. In this study, MES-related genes were obtained from The Cancer Genome Atlas (TCGA) and the Ivy Glioblastoma Atlas Project (Ivy GAP) data sets of glioma, and MES-related lncRNAs were acquired by performing co-expression analysis of these genes. Next, Cox regression analysis was used to establish a prognostic model, that integrated ten MES-related lncRNAs. Glioma patients in TCGA were divided into high-risk and low-risk groups based on the median risk score; compared with the low-risk groups, patients in the high-risk group had shorter survival times. Additionally, we measured the specificity and sensitivity of our model with the ROC curve. Univariate and multivariate Cox analyses showed that the prognostic model was an independent prognostic factor for glioma. To verify the predictive power of these candidate lncRNAs, the corresponding RNA-seq data were downloaded from the Chinese Glioma Genome Atlas (CGGA), and similar results were obtained. Next, we performed the immune cell infiltration profile of patients between two risk groups, and gene set enrichment analysis (GSEA) was performed to detect functional annotation. Finally, the protective factors DGCR10 and HAR1B, and risk factor SNHG18 were selected for functional verification. Knockdown of DGCR10 and HAR1B promoted, whereas knockdown of SNHG18 inhibited the migration and invasion of gliomas. Collectively, we successfully constructed a prognostic model based on a ten MES-related lncRNAs signature, which provides a novel target for predicting the prognosis for glioma patients.

Advanced glycation end products induce endothelial hyperpermeability via β-catenin phosphorylation and subsequent up-regulation of ADAM10

Endothelial hyperpermeability is the initial event in the development of diabetic microvascular complications, and advanced glycation end products (AGEs) are suggested to cause much of the endothelial hyperpermeability associated with diabetes mellitus, but the molecular mechanism remains to be characterized. β-catenin reportedly plays dual functions in maintaining normal endothelial permeability by serving both as an adhesive component and a signal transduction component. Here, we found that AGEs induced the phosphorylation of β-catenin at residues Y654 and Y142 and the endothelial hyperpermeability was reversed when the two residues were blocked. In mechanism, phosphorylation of Y654 was blocked by Src inactivation, whereas phosphorylation of Y142 was reduced by a focal adhesion kinase inhibitor. β-catenin Y654 phosphorylation induced by AGEs facilitated the dissociation of vascular endothelial (VE)-cadherin/β-catenin and the impairment of adherens junctions (AJs), whereas β-catenin Y142 phosphorylation favoured the dissociation of β-catenin and α-catenin. Further investigation revealed that β-catenin Y142 phosphorylation was required for AGEs-mediated β-catenin nuclear translocation, and this nuclear-located β-catenin subsequently activated the TCF/LEF pathway. This pathway promotes the transcription of the Wnt target, ADAM10 (a disintegrin and metalloprotease 10), which mediates VE-cadherin shedding and leads to further impairment of AJs. In summary, our study showed the role of β-catenin Y654 and Y142 phosphorylation in AGEs-mediated endothelial hyperpermeability through VE-cadherin/β-catenin/α-catenin dissociation and up-regulation of ADAM10, thereby advancing our understanding of the underlying mechanisms of AGEs-induced microvascular hyperpermeability.

Regulatory interplay between Vav1, Syk and β-catenin occurs in lung cancer cells

Vav1 exhibits two signal transducing properties as an adaptor protein and a regulator of cytoskeleton organization through its Guanine nucleotide Exchange Factor module. Although the expression of Vav1 is restricted to the hematopoietic lineage, its ectopic expression has been unraveled in a number of solid tumors. In this study, we show that in lung cancer cells, as such in hematopoietic cells, Vav1 interacts with the Spleen Tyrosine Kinase, Syk. Likewise, Syk interacts with β-catenin and, together with Vav1, regulates the phosphorylation status of β-catenin. Depletion of Vav1, Syk or β-catenin inhibits Rac1 activity and decreases cell migration suggesting the interplay of the three effectors to a common signaling pathway. This model is further supported by the finding that in turn, β-catenin regulates the transcription of Syk gene expression. This study highlights the elaborated connection between Vav1, Syk and β-catenin and the contribution of the trio to cell migration.

Mucosal Epithelial Jak Kinases in Health and Diseases

Janus kinases (Jaks) are a family of nonreceptor tyrosine kinase that include four different members, viz., Jak1, Jak2, Jak3, and Tyk2. Jaks play critical roles in immune cells functions; however, recent studies suggest they also play essential roles in nonimmune cell physiology. This review highlights the significance of epithelial Jaks in understanding the molecular basis of some of the diseases through regulation of epithelial-mesenchymal transition, cell survival, cell growth, development, and differentiation. Growth factors and cytokines produced by the cells of hematopoietic origin use Jak kinases for signal transduction in both immune and nonimmune cells. Among Jaks, Jak3 is widely expressed in both immune cells and in intestinal epithelial cells (IECs) of both humans and mice. Mutations that abrogate Jak3 functions cause an autosomal severe combined immunodeficiency disease (SCID) while activating Jak3 mutations lead to the development of hematologic and epithelial cancers. A selective Jak3 inhibitor CP-690550 (Xeljanz) approved by the FDA for certain chronic inflammatory conditions demonstrates immunosuppressive activity in rheumatoid arthritis, psoriasis, and organ transplant rejection. Here, we also focus on the consequences of Jak3-directed drugs on adverse effects in light of recent discoveries in mucosal epithelial functions of Jak3 with some information on other Jaks. Lastly, we brief on structural implications of Jak3 domains beyond the immune cells. As information about the roles of Jak3 in gastrointestinal functions and associated diseases are only just emerging, in the review, we summarize its implications in gastrointestinal wound repair, inflammatory bowel disease, obesity-associated metabolic syndrome, and epithelial cancers. Lastly, we shed lights on identifying potential novel targets in developing therapeutic interventions of diseases associated with dysfunctional IEC.

Inhibition of Carbonyl Reductase 1 Enhances Metastasis of Head and Neck Squamous Cell Carcinoma through β-catenin-Mediated Epithelial-Mesenchymal Transition

Objective: Human carbonyl reductase 1 (CBR1) plays key roles in the regulation of oxidative stress and tumor progression. However, the detailed mechanism and clinical correlation between CBR1 and tumor progression in head and neck squamous cell carcinoma (HNSCC) is largely unexplored. This study will focus the effects of CBR1 on head and neck cancer progression and explore the possible mechanisms.

Materials and Methods:CBR1 mRNA expression was analyzed according to lymph node metastasis (LNM) status in patients with HNSCC from publicly available databases. CBR1 protein levels were measured and compared in HNSCC patient tissues, with or without metastasis, using immunohistochemistry (IHC). The invasive ability of HNSCC with modulated CBR1 expression was assayed using an invasion assay. Expression levels of EMT marker proteins were analyzed using immunoblotting.

Results: HNSCC patients with LNM showed lower expression of CBR1 than those without LNM. In addition, IHC in tissues indicated that patients with LNM had relatively lower levels of CBR1 in cancer tissue. Consistently, in vitro invasion assay, we found that CBR1 inhibition using specific short interfering RNA treatment resulted in two- to three-fold increased invasion ability of HNSCC cell lines. Also, we proved that depletion of CBR1 activated marker proteins participating in epithelial-mesenchymal transition (EMT) signaling. CBR1 inhibition increased levels of intracellular reactive oxygen species (ROS) in HNSCC cells leading to upregulation of β-catenin, one of main transcription factors that induce EMT-related genes.

Conclusion: Our findings suggested that CBR1 plays an important role in metastasis of HNSCC tumors via regulation of ROS-mediated β-catenin activity, and that CBR1 may be marker for progression of HNSCC to metastasis.

β‑catenin nuclear translocation induced by HIF‑1α overexpression leads to the radioresistance of prostate cancer

Hypoxia-inducible factor-1α (HIF-1α) is known to play crucial roles in tumor radioresistance; however, the molecular mechanisms responsible for the promotion of tumor radioresistance by HIF-1α remain unclear. β-catenin is known to be involved in the metastatic potential of prostate cancer (PCa). In this study, to investigate the role of HIF-1α and β-catenin in the radioresistance of PCa, two PCa cell lines, LNCaP and C4-2B, were grouped as follows: Negative control (no treatment), HIF-1α overexpression group (transfected with HIF-1α overexpression plasmid) and β-catenin silenced group (transfected with HIF-1α plasmids and β-catenin-shRNA). Cell proliferation, cell cycle, cell invasion and radiosensitivity were examined under normal or hypoxic conditions. In addition, radiosensitivity was examined in two mouse PCa models (the LNCaP orthotopic BALB/c-nu mice model and the C4-2B subcutaneous SCID mice model). Our results revealed that in both the LNCaP and C4-2B cells, transfection with HIF-1α overexpression plasmid led to an enhanced β-catenin nuclear translocation, while β-catenin silencing inhibited β-catenin nuclear translocation. The enhanced β-catenin nuclear translocation induced by HIF-1α overexpression resulted in an enhanced cell proliferation and cell invasion, an altered cell cycle distribution, decreased apoptosis, and improved non-homologous end joining (NHEJ) repair under normal and irradiation conditions. Similar results were observed in the animal models. HIF-1α overexpression enhanced β-catenin nuclear translocation, which led to the activation of the β-catenin/NHEJ signaling pathway and increased cell proliferation, cell invasion and DNA repair. These results thus suggest that HIF-1α overexpression promotes the radioresistance of PCa cells.

A Shared Pattern of β-Catenin Activation in Bronchopulmonary Dysplasia and Idiopathic Pulmonary Fibrosis

Wnt/β-catenin signaling is necessary for normal lung development, and abnormal Wnt signaling contributes to the pathogenesis of both bronchopulmonary dysplasia (BPD) and idiopathic pulmonary fibrosis (IPF), fibrotic lung diseases that occur during infancy and aging, respectively. Using a library of human normal and diseased human lung samples, we identified a distinct signature of nuclear accumulation of β-catenin phosphorylated at tyrosine 489 and epithelial cell cytosolic localization of β-catenin phosphorylated at tyrosine 654 in early normal lung development and fibrotic lung diseases BPD and IPF. Furthermore, this signature was recapitulated in murine models of BPD and IPF. Image analysis of immunofluorescence colocalization demonstrated a consistent pattern of elevated nuclear phosphorylated β-catenin in the lung epithelium and surrounding mesenchyme in BPD and IPF, closely resembling the pattern observed in 18-week fetal lung. Nuclear β-catenin phosphorylated at tyrosine 489 associated with an increased expression of Wnt target gene AXIN2, suggesting that the observed β-catenin signature is of functional significance during normal development and injury repair. The association of specific modifications of β-catenin during normal lung development and again in response to lung injury supports the widely held concept that repair of lung injury involves the recapitulation of developmental programs. Furthermore, these observations suggest that β-catenin phosphorylation has potential as a therapeutic target for the treatment and prevention of both BPD and IPF.

Signaling pathways and mesenchymal transition in pediatric high-grade glioma

Pediatric high-grade gliomas (pHGG), including diffuse intrinsic pontine gliomas (DIPG), are the most lethal types of cancer in children. In recent years, it has become evident that these tumors are driven by epigenetic events, mainly mutations involving genes encoding Histone 3, setting them apart from their adult counterparts. These tumors are exceptionally resistant to chemotherapy and respond only temporarily to radiotherapy. Moreover, their delicate location and diffuse growth pattern make complete surgical resection impossible. In many other forms of cancer, chemo- and radioresistance, in combination with a diffuse, invasive phenotype, are associated with a transcriptional program termed the epithelial-to-mesenchymal transition (EMT). Activation of this program allows cancer cells to survive individually, invade surrounding tissues and metastasize. It also enables them to survive exposure to cytotoxic therapy, including chemotherapeutic drugs and radiation. We here suggest that EMT plays an important, yet poorly understood role in the biology and therapy resistance of pHGG and DIPG. This review summarizes the current knowledge on the major signal transduction pathways and transcription factors involved in the epithelial-to-mesenchymal transition in cancer in general and in pediatric HGG and DIPG in particular. Despite the fact that the mesenchymal transition has not yet been specifically studied in pHGG and DIPG, activation of pathways and high levels of transcription factors involved in EMT have been described. We conclude that the mesenchymal transition is likely to be an important element of the biology of pHGG and DIPG and warrants further investigation for the development of novel therapeutics.

Long noncoding RNA NORAD, a novel competing endogenous RNA, enhances the hypoxia-induced epithelial-mesenchymal transition to promote metastasis in pancreatic cancer

Background

Pancreatic cancer, one of the top two most fatal cancers, is characterized by a desmoplastic reaction that creates a dense microenvironment, promoting hypoxia and inducing the epithelial-to-mesenchymal transition (EMT) to facilitate invasion and metastasis. Recent evidence indicates that the long noncoding RNA NORAD may be a potential oncogenic gene and that this lncRNA is significantly upregulated during hypoxia. However, the overall biological role and clinical significance of NORAD remains largely unknown.

Methods

NORAD expression was measured in 33 paired cancerous and noncancerous tissue samples by real-time PCR. The effects of NORAD on pancreatic cancer cells were studied by overexpression and knockdown in vitro. Insights into the mechanism of competitive endogenous RNAs (ceRNAs) were gained from bioinformatics analyses and luciferase assays. In vivo, metastatic potential was identified using an orthotopic model of PDAC and quantified using bioluminescent signals. Alterations in RhoA expression and EMT levels were identified and verified by immunohistochemistry and Western blotting.

Results

NORAD is highly expressed in pancreatic cancer tissues and upregulated in hypoxic conditions. NORAD upregulation is correlated with shorter overall survival in pancreatic cancer patients. Furthermore, NORAD overexpression promoted the migration and invasion of pancreatic carcinoma cells, while NORAD depletion inhibited EMT and metastasis in vitro and in vivo. In particular, NORAD may function as a ceRNA to regulate the expression of the small GTP binding protein RhoA through competition for hsa-miR-125a-3p, thereby promoting EMT.

Conclusions

Elevated expression of NORAD in pancreatic cancer tissues is linked to poor prognosis and may confer a malignant phenotype upon tumor cells. NORAD may function as a ceRNA to regulate the expression of the small GTP binding protein RhoA through competition for hsa-miR-125a-3p. This finding may contribute to a better understanding of the role played by lncRNAs in hypoxia-induced EMT and provide a potential novel diagnostic and therapeutic target for pancreatic cancer.

Electronic supplementary material

The online version of this article (10.1186/s12943-017-0738-0) contains supplementary material, which is available to authorized users.

Paving the Rho in cancer metastasis: Rho GTPases and beyond

Malignant carcinomas are often characterized by metastasis, the movement of carcinoma cells from a primary site to colonize distant organs. For metastasis to occur, carcinoma cells first must adopt a pro-migratory phenotype and move through the surrounding stroma towards a blood or lymphatic vessel. Currently, there are very limited possibilities to target these processes therapeutically. The family of Rho GTPases is an ubiquitously expressed division of GTP-binding proteins involved in the regulation of cytoskeletal dynamics and intracellular signaling. The best characterized members of the Rho family GTPases are RhoA, Rac1 and Cdc42. Abnormalities in Rho GTPase function have major consequences for cancer progression. Rho GTPase activation is driven by cell surface receptors that activate GTP exchange factors (GEFs) and GTPase-activating proteins (GAPs). In this review, we summarize our current knowledge on Rho GTPase function in the regulation of metastasis. We will focus on key discoveries in the regulation of epithelial-mesenchymal-transition (EMT), cell-cell junctions, formation of membrane protrusions, plasticity of cell migration and adaptation to a hypoxic environment. In addition, we will emphasize on crosstalk between Rho GTPase family members and other important oncogenic pathways, such as cyclic AMP-mediated signaling, canonical Wnt/β-catenin, Yes-associated protein (YAP) and hypoxia inducible factor 1α (Hif1α) and provide an overview of the advancements and challenges in developing pharmacological tools to target Rho GTPase and the aforementioned crosstalk in the context of cancer therapeutics.

Redox regulation in tumor cell epithelial-mesenchymal transition: molecular basis and therapeutic strategy

Epithelial–mesenchymal transition (EMT) is recognized as a driving force of cancer cell metastasis and drug resistance, two leading causes of cancer recurrence and cancer-related death. It is, therefore, logical in cancer therapy to target the EMT switch to prevent such cancer metastasis and recurrence. Previous reports have indicated that growth factors (such as epidermal growth factor and fibroblast growth factor) and cytokines (such as the transforming growth factor beta (TGF-β) family) are major stimulators of EMT. However, the mechanisms underlying EMT initiation and progression remain unclear. Recently, emerging evidence has suggested that reactive oxygen species (ROS), important cellular secondary messengers involved in diverse biological events in cancer cells, play essential roles in the EMT process in cancer cells by regulating extracellular matrix (ECM) remodeling, cytoskeleton remodeling, cell–cell junctions, and cell mobility. Thus, targeting EMT by manipulating the intracellular redox status may hold promise for cancer therapy. Herein, we will address recent advances in redox biology involved in the EMT process in cancer cells, which will contribute to the development of novel therapeutic strategies by targeting redox-regulated EMT for cancer treatment.

Janus kinase 3 regulates adherens junctions and epithelial mesenchymal transition through β-catenin

Compromise in adherens junctions (AJs) is associated with several chronic inflammatory diseases. We reported previously that Janus kinase 3, a non-receptor tyrosine kinase, plays a crucial role in AJ formation through its interaction with β-catenin. In this report, we characterize the structural determinants responsible for Jak3 interactions with β-catenin and determine the functional implications of previously unknown tyrosine residues on β-catenin phosphorylated by Jak3. We demonstrate that Jak3 autophosphorylation was the rate-limiting step during Jak3 trans-phosphorylation of β-catenin, where Jak3 directly phosphorylated three tyrosine residues, viz. Tyr³⁰, Tyr⁶⁴, and Tyr⁸⁶ in the N-terminal domain (NTD) of β-catenin. However, prior phosphorylation of β-catenin at Tyr⁶⁵⁴ was essential for further phosphorylation of β-catenin by Jak3. Interaction studies indicated that phosphorylated Jak3 bound to phosphorylated β-catenin with a dissociation constant of 0.28 μm, and although both the kinase and FERM (Band 41, ezrin, radixin, and moesin) domains of Jak3 interacted with β-catenin, the NTD domain of β-catenin facilitated its interactions with Jak3. Physiologically, Jak3-mediated phosphorylation of β-catenin suppressed EGF-mediated epithelial-mesenchymal transition and facilitated epithelial barrier functions by AJ localization of phosphorylated β-catenin through its interactions with α-catenin. Moreover, loss of Jak3-mediated phosphorylation sites in β-catenin abrogated its AJ localization and compromised epithelial barrier functions. Thus, we not only characterize Jak3 interaction with β-catenin but also demonstrate the mechanism of molecular interplay between AJ dynamics and EMT by Jak3-mediated NTD phosphorylation of β-catenin.

Hypoxia-Inducible Factor 1α Signaling Promotes Repair of the Alveolar Epithelium after Acute Lung Injury

During the acute respiratory distress syndrome, epithelial cells, primarily alveolar type (AT) I cells, die and slough off, resulting in enhanced permeability. ATII cells proliferate and spread onto the denuded basement membrane to reseal the barrier. Repair of the alveolar epithelium is critical for clinical recovery; however, mechanisms underlying ATII cell proliferation and spreading are not well understood. We hypothesized that hypoxia-inducible factor (HIF)1α promotes proliferation and spreading of ATII cells during repair after lung injury. Mice were treated with lipopolysaccharide or hydrochloric acid. HIF activation in ATII cells after injury was demonstrated by increased luciferase activity in oxygen degradation domain-Luc (HIF reporter) mice and expression of the HIF1α target gene GLUT1. ATII cell proliferation during repair was attenuated in ATII cell-specific HIF1α knockout (SftpcCreERT2+/-;HIF1αf/f) mice. The HIF target vascular endothelial growth factor promoted ATII cell proliferation in vitro and after lung injury in vivo. In the scratch wound assay of cell spreading, HIF stabilization accelerated, whereas HIF1α shRNA delayed wound closure. SDF1 and its receptor, CXCR4, were found to be HIF1α-regulated genes in ATII cells and were up-regulated during lung injury. Stromal cell-derived factor 1/CXCR4 inhibition impaired cell spreading and delayed the resolution of permeability after lung injury. We conclude that HIF1α is activated in ATII cells after lung injury and promotes proliferation and spreading during repair.

CEACAM1 controls the EMT switch in murine mammary carcinoma in vitro and in vivo

We analyzed the molecular basis for carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1)-controlled inhibition of epithelial-mesenchymal transition (EMT) in a mouse model for mammary adenocarcinoma (WAP-T mice). We demonstrate that silencing of CEACAM1 in WAP-T tumor-derived G-2 cells induces epithelial-mesenchymal plasticity (EMP), as evidenced by typical changes of gene expression, morphology and increased invasion. In contrast, reintroduction of CEACAM1 into G-2 cells reversed up-regulation of genes imposing mesenchymal transition, as well as cellular invasion. We identified the Wnt-pathway as target for CEACAM1-mediated repression of EMT. Importantly, β-catenin phosphorylation status and transcriptional activity strongly depend on CEACAM1 expression: CEACAM1high G-2 cells displayed enhanced phosphorylation of β-catenin at S33/S37/T41 and decreased phosphorylation at Y86, thereby inhibiting canonical Wnt/β-catenin signaling. We identified Src-homology 2 domain-containing phosphatase 2 (SHP-2) as a critical binding partner of CEACAM1 that could modulate β-catenin Y86 phosphorylation. Hence, CEACAM1 serves as a scaffold that controls membrane proximal β-catenin signaling. In vivo, mammary tumors of WAP-T/CEACAM1null mice displayed increased nuclear translocation of β-catenin and a dramatically enhanced metastasis rate compared to WAP-T mice. Hence, CEACAM1 controls EMT in vitro and in vivo by site-specific regulation of β-catenin phosphorylation. Survival analyses of human mammary carcinoma patients corroborated these data, indicating that CEACAM1 is a prognostic marker for breast cancer survival.

The WNT-less wonder: WNT-independent β-catenin signaling

β-catenin is known as an Armadillo protein that regulates gene expression following WNT pathway activation. However, WNT-independent pathways also activate β-catenin. During the establishment of the melanocyte lineage, β-catenin plays an important role. In the context of physiopathology, β-catenin is activated genetically or transiently in various cancers, including melanoma, where it can be found in the nucleus of tumors. In this review, we discuss alternative pathways that activate β-catenin independent of WNTs and highlight what is known regarding these pathways in melanoma. We also discuss the role of β-catenin as a transcriptional regulator in various cell types, with emphasis on the different transcription factors it associates with independent of WNT induction. Finally, the role of WNT-independent β-catenin in melanocyte development and melanomagenesis is also discussed.

Frequent inactivation of MCC/CTNNBIP1 and overexpression of phospho-beta-catenin(Y654) are associated with breast carcinoma: Clinical and prognostic significance

Transcriptional activation of β-catenin is a hallmark of Wnt/β-catenin pathway activation. The MCC (Mutated in colorectal cancers) and CTNNBIP1 (catenin, beta interacting protein 1) are two candidate genes which inhibit the transcriptional activity of nuclear β-catenin. The importance of MCC and CTNNBIP1 in breast cancer (BC) development has not yet been studied in detail. For this reason, in present study, the alterations (deletion/methylation/mutation/expression) of MCC and CTNNBIP1 were analyzed in BC of Indian patients (N=120) followed by expression/mutation analysis of β-catenin. Then transcriptional activity of β-catenin was checked by expression analysis of its target genes (EGFR, C-MYC and CCND1) in the same set of samples. Frequent methylation (44-45%) than deletion (20-32%) with overall alterations of 52-55% was observed in MCC/CTNNBIP1 in the BC samples. The alterations of MCC/CTNNBIP1 showed significant correlation with increased nuclear β-catenin/p-β-catenin(Y654) expression. Also, a significant correlation was seen between nuclear β-catenin expression and overexpression of its target genes like EGFR, MYC and CCND1 in the BC samples (P<0.0001). An upregulation of MCC and CTNNBIP1 expression by 5-Aza-2'-deoxycytidine treatment of MCF7 and MDA-MB-231 cell lines lead to downregulation of β-catenin and its target genes. The expression of nuclear p-β-catenin(Y654), EGFR, MYC and CCND1 were significantly high in TNBC (Triple negative BC) and Her2+ compared to Luminal A/B+ subtypes. The TNBC patients in stage III/IV having reduced expression of MCC in the tumors showed poor prognosis. Thus, our data suggests that inactivation of MCC/CTNNBIP1 could be an important event in activation of β-catenin mediated transcription of target genes in BC.

Hypoxia-induced modulation of PTEN activity and EMT phenotypes in lung cancers

Background

Persistent hypoxia stimulation, one of the most critical microenvironmental factors, accelerates the acquisition of epithelial–mesenchymal transition (EMT) phenotypes in lung cancer cells. Loss of phosphatase and tensin homologue deleted from chromosome 10 (PTEN) expression might accelerate the development of lung cancer in vivo. Recent studies suggest that tumor microenvironmental factors might modulate the PTEN activity though a decrease in total PTEN expression and an increase in phosphorylation of the PTEN C-terminus (p-PTEN), resulting in the acquisition of the EMT phenotypes. Nevertheless, it is not known whether persistent hypoxia can modulate PTEN phosphatase activity or whether hypoxia-induced EMT phenotypes are negatively regulated by the PTEN phosphatase activity. We aimed to investigate hypoxia-induced modulation of PTEN activity and EMT phenotypes in lung cancers.

Methods

Western blotting was performed in five lung cancer cell lines to evaluate total PTEN expression levels and the PTEN activation. In a xenograft model of lung cancer cells with endogenous PTEN expression, the PTEN expression was evaluated by immunohistochemistry. To examine the effect of hypoxia on phenotypic alterations in lung cancer cells in vitro, the cells were cultured under hypoxia. The effect of unphosphorylated PTEN (PTEN4A) induction on hypoxia-induced EMT phenotypes was evaluated, by using a Dox-dependent gene expression system.

Results

Lung cancer cells involving the EMT phenotypes showed a decrease in total PTEN expression and an increase in p-PTEN. In a xenograft model, loss of PTEN expression was observed in the tumor lesions showing tissue hypoxia. Persistent hypoxia yielded an approximately eight-fold increase in the p-PTEN/PTEN ratio in vitro. PTEN4A did not affect stabilization of hypoxia-inducible factor 1α. PTEN4A blunted hypoxia-induced EMT via inhibition of β-catenin translocation into the cytoplasm and nucleus.

Conclusion

Our study strengthens the therapeutic possibility that compensatory induction of unphosphorylated PTEN may inhibit the acquisition of EMT phenotypes in lung cancer cells under persistent hypoxia.

A novel mechanism of action for salidroside to alleviate diabetic albuminuria: effects on albumin transcytosis across glomerular endothelial cells

Salidroside (SAL) is a phenylethanoid glycoside isolated from the medicinal plant Rhodiola rosea. R. rosea has been reported to have beneficial effects on diabetic nephropathy (DN) and high-glucose (HG)-induced mesangial cell proliferation. Given the importance of caveolin-1 (Cav-1) in transcytosis of albumin across the endothelial barrier, the present study was designed to elucidate whether SAL could inhibit Cav-1 phosphorylation and reduce the albumin transcytosis across glomerular endothelial cells (GECs) to alleviate diabetic albuminuria as well as to explore its upstream signaling pathway. To assess the therapeutic potential of SAL and the mechanisms involved in DN albuminuria, we orally administered SAL to db/db mice, and the effect of SAL on the albuminuria was measured. The albumin transcytosis across GECs was explored in a newly established in vitro cellular model. The ratio of albumin to creatinine was significantly reduced upon SAL treatment in db/db mice. SAL decreased the albumin transcytosis across GECs in both normoglycemic and hyperglycemic conditions. SAL reversed the HG-induced downregulation of AMP-activated protein kinase and upregulation of Src kinase and blocked the upregulation Cav-1 phosphorylation. Meanwhile, SAL decreased mitochondrial superoxide anion production and moderately depolarized mitochondrial membrane potential. We conclude that SAL exerts its proteinuria-alleviating effects by downregulation of Cav-1 phosphorylation and inhibition of albumin transcytosis across GECs. These studies provide the first evidence of interference with albumin transcytosis across GECs as a novel approach to the treatment of diabetic albuminuria.

Reactive Oxygen Species and Targeted Therapy for Pancreatic Cancer

Pancreatic cancer is the fourth leading cause of cancer-related death in the United States. Reactive oxygen species (ROS) are generally increased in pancreatic cancer cells compared with normal cells. ROS plays a vital role in various cellular biological activities including proliferation, growth, apoptosis, and invasion. Besides, ROS participates in tumor microenvironment orchestration. The role of ROS is a doubled-edged sword in pancreatic cancer. The dual roles of ROS depend on the concentration. ROS facilitates carcinogenesis and cancer progression with mild-to-moderate elevated levels, while excessive ROS damages cancer cells dramatically and leads to cell death. Based on the recent knowledge, either promoting ROS generation to increase the concentration of ROS with extremely high levels or enhancing ROS scavenging ability to decrease ROS levels may benefit the treatment of pancreatic cancer. However, when faced with oxidative stress, the antioxidant programs of cancer cells have been activated to help cancer cells to survive in the adverse condition. Furthermore, ROS signaling and antioxidant programs play the vital roles in the progression of pancreatic cancer and in the response to cancer treatment. Eventually, it may be the novel target for various strategies and drugs to modulate ROS levels in pancreatic cancer therapy.

Nuclear signaling from cadherin adhesion complexes

The arrival of multicellularity in evolution facilitated cell-cell signaling in conjunction with adhesion. As the ectodomains of cadherins interact with each other directly in trans (as well as in cis), spanning the plasma membrane and associating with multiple other entities, cadherins enable the transduction of "outside-in" or "inside-out" signals. We focus this review on signals that originate from the larger family of cadherins that are inwardly directed to the nucleus, and thus have roles in gene control or nuclear structure-function. The nature of cadherin complexes varies considerably depending on the type of cadherin and its context, and we will address some of these variables for classical cadherins versus other family members. Substantial but still fragmentary progress has been made in understanding the signaling mediators used by varied cadherin complexes to coordinate the state of cell-cell adhesion with gene expression. Evidence that cadherin intracellular binding partners also localize to the nucleus is a major point of interest. In some models, catenins show reduced binding to cadherin cytoplasmic tails favoring their engagement in gene control. When bound, cadherins may serve as stoichiometric competitors of nuclear signals. Cadherins also directly or indirectly affect numerous signaling pathways (e.g., Wnt, receptor tyrosine kinase, Hippo, NFκB, and JAK/STAT), enabling cell-cell contacts to touch upon multiple biological outcomes in embryonic development and tissue homeostasis.

Bioinformatic approaches to augment study of epithelial-to-mesenchymal transition in lung cancer

Bioinformatic approaches are intended to provide systems level insight into the complex biological processes that underlie serious diseases such as cancer. In this review we describe current bioinformatic resources, and illustrate how they have been used to study a clinically important example: epithelial-to-mesenchymal transition (EMT) in lung cancer. Lung cancer is the leading cause of cancer-related deaths and is often diagnosed at advanced stages, leading to limited therapeutic success. While EMT is essential during development and wound healing, pathological reactivation of this program by cancer cells contributes to metastasis and drug resistance, both major causes of death from lung cancer. Challenges of studying EMT include its transient nature, its molecular and phenotypic heterogeneity, and the complicated networks of rewired signaling cascades. Given the biology of lung cancer and the role of EMT, it is critical to better align the two in order to advance the impact of precision oncology. This task relies heavily on the application of bioinformatic resources. Besides summarizing recent work in this area, we use four EMT-associated genes, TGF-β (TGFB1), NEDD9/HEF1, β-catenin (CTNNB1) and E-cadherin (CDH1), as exemplars to demonstrate the current capacities and limitations of probing bioinformatic resources to inform hypothesis-driven studies with therapeutic goals.

Long non-coding RNA-LET is a positive prognostic factor and exhibits tumor-suppressive activity in gallbladder cancer

The identification of cancer-associated long non-coding RNAs (lncRNAs) and the investigation of their molecular and biological functions are vital for understanding the molecular biology and progression of cancer. The lncRNA-LET, a newly identified lncRNA, was demonstrated to be down-regulated in hepatocellular cancer. However, little is known about its role in gallbladder cancer. In the present study, an obvious down-regulation of lncRNA-LET was observed in gallbladder cancer compared to their adjacent normal tissues. Meanwhile, patients with low expression of lncRNA-LET have significantly poorer prognosis than those with high expression. We confirmed that hypoxia decreased lncRNA-LET levels in gallbladder cancer cells. Moreover, lncRNA-LET overexpression was further validated to inhibit the invasion of gallbladder cancer cells under hypoxic or normoxic conditions in vitro. We demonstrated that lncRNA-LET overexpression conferred a proliferative advantage to tumor cells under hypoxic conditions. The ectopic expression of lncRNA-LET led to the promotion of cell cycle arrest at G0/G1 phase and to the induction of apoptosis under hypoxic conditions. Ectopic expression of LncRNA-LET also suppressed gallbladder tumor growth in vivo. Our findings indicate that lncRNA-LET may represent a prognostic marker and a potential therapeutic target for gallbladder cancer.

Downregulation of FOXO3a promotes tumor metastasis and is associated with metastasis-free survival of patients with clear cell renal cell carcinoma

PURPOSE

To explore the mechanisms underlying clear-cell renal cell carcinoma (ccRCC) metastasis using transcriptional profiling and bioinformatics analysis of ccRCC samples, and to elucidate the role of FOXO3a in ccRCC metastasis.

EXPERIMENTAL DESIGN

Gene expression profiling was performed using four primary metastatic and five primary nonmetastatic ccRCC samples. The mRNA and protein levels of FOXO3a in ccRCC samples were investigated by real-time reverse transcription PCR and immunohistochemistry, respectively. The association between metastasis-free survival of patients with ccRCC and FOXO3a mRNA levels was analyzed. Biologic functions of FOXO3a in renal cancer cell lines were investigated. The influence of FOXO3a on tumor metastasis was also studied in vivo orthotopic xenograft tumor model. Finally, the mechanism by which FOXO3a attenuation could increase invasion and migration of tumor cells was explored.

RESULTS

Bioinformatics analysis of the profiling data identified FOXO3a as a key factor in ccRCC metastasis. FOXO3a expression was decreased in primary metastatic ccRCC samples. Patients with low FOXO3a mRNA levels had poor metastasis-free survival (P = 0.003). Knocking down FOXO3a induced tumor cell invasion and migration in the nonmetastatic ccRCC cells. Induced FOXO3a overexpression in SN12-PM6 cells could inhibit tumor metastasis in vivo. Downregulation of FOXO3a increased SNAIL1 expression, thereby activating the epithelial-mesenchymal transition (EMT) of RCC cell lines.

CONCLUSIONS

The loss of FOXO3a induced EMT of tumor cells by upregulating SNAIL1, which promoted tumor cells metastasis in vitro and in vivo. Thus, FOXO3a could be considered as an independent prognostic factor in ccRCC metastasis and could be a marker of occult metastases.

Enhanceosomes as integrators of hypoxia inducible factor (HIF) and other transcription factors in the hypoxic transcriptional response

Hypoxia is a prevalent attribute of the solid tumor microenvironment that promotes the expression of genes through posttranslational modifications and stabilization of alpha subunits (HIF1α and HIF2α) of hypoxia-inducible factors (HIFs). Despite significant similarities, HIF1 (HIF1α/ARNT) and HIF2 (HIF2α/ARNT) activate common as well as unique target genes and exhibit different functions in cancer biology. More surprisingly, accumulating data indicates that the HIF1- and/or HIF2-mediated hypoxia responses can be oncogenic as well as tumor suppressive. While the role of HIF in the hypoxia response is well established, recent data support the concept that HIF is necessary, but not sufficient for the hypoxic response. Other transcription factors that are activated by hypoxia are also required for the HIF-mediated hypoxia response. HIFs, other transcription factors, co-factors and RNA poll II recruited by HIF and other transcription factors form multifactorial enhanceosome complexes on the promoters of HIF target genes to activate hypoxia inducible genes. Importantly, HIF1 or HIF2 requires distinct partners in activating HIF1 or HIF2 target genes. Because HIF enhanceosome formation is required for the gene activation and distinct functions of HIF1 and HIF2 in tumor biology, disruption of the HIF1 or HIF2 specific enhanceosome complex may prove to be a beneficial strategy in tumor treatment in which tumor growth is specifically dependent upon HIF1 or HIF2 activity.

c-Myc regulates proliferation and Fgf10 expression in airway smooth muscle after airway epithelial injury in mouse

During lung development, Fibroblast growth factor 10 (Fgf10), which is expressed in the distal mesenchyme and regulated by Wnt signaling, acts on the distal epithelial progenitors to maintain them and prevent them from differentiating into proximal (airway) epithelial cells. Fgf10-expressing cells in the distal mesenchyme are progenitors for parabronchial smooth muscle cells (PSMCs). After naphthalene, ozone or bleomycin-induced airway epithelial injury, surviving epithelial cells secrete Wnt7b which then activates the PSMC niche to induce Fgf10 expression. This Fgf10 secreted by the niche then acts on a subset of Clara stem cells to break quiescence, induce proliferation and initiate epithelial repair. Here we show that conditional deletion of the Wnt target gene c-Myc from the lung mesenchyme during development does not affect proper epithelial or mesenchymal differentiation. However, in the adult lung we show that after naphthalene-mediated airway epithelial injury c-Myc is important for the activation of the PSMC niche and as such induces proliferation and Fgf10 expression in PSMCs. Our data indicate that conditional deletion of c-Myc from PSMCs inhibits airway epithelial repair, whereas c-Myc ablation from Clara cells has no effect on airway epithelial regeneration. These findings may have important implications for understanding the misregulation of lung repair in asthma and COPD.

Utility of a bacterial infection model to study epithelial-mesenchymal transition, mesenchymal-epithelial transition or tumorigenesis

DCLK1 and Lgr5 have recently been identified as markers of quiescent and cycling stem cells in the small intestinal crypts, respectively. Epithelial-mesenchymal transition (EMT) is a key development program that is often activated during cancer invasion and metastasis, and also imparts a self-renewal capability to disseminating cancer cells. Utilizing the Citrobacter rodentium (CR)-induced transmissible murine colonic hyperplasia (TMCH) model, we observed a relative decrease in DCLK1 expression in the colonic crypts, with significant shift towards stromal staining at peak (12 days post infection) hyperplasia, whereas staining for Lgr5 and Msi-1 increased several fold. When hyperplasia was regressing (days 20-34), an expansion of DCLK1+ve cells in the CR-infected crypts compared with that seen in uninfected control was recorded. Purified colonic crypt cells exhibiting epigenetic modulation of the transforming growth factor-β (TGFβ), Wnt and Notch pathways on 12 or 34 days post infection formed monolayers in vitro, and underwent trans-differentiation into fibroblast-like cells that stained positive for vimentin, fibronectin and DCLK1. These cells when trypsinized and regrown in soft agar, formed colonospheres/organoids that developed into crypt-like structures (colonoids) in Matrigel and stained positive for DCLK1. Mice exhibiting 12 or 34 days of TMCH were given azoxymethane once for 8 h (Gp1) or weekly for 3 weeks (Gp2), and subjected to crypt isolation. Crypt cells from Gp1 animals formed monolayers as well as colonospheres in soft agar and nodules/tumors in nude mice. Crypt cells isolated from Gp2 animals failed to form the monolayers, but developed into colonospheres in soft agar and nodules/tumors in nude mice. Thus, both hyperplasia and increased presence of DCLK1+ve cells promote cellular transformation in response to a second hit. The TMCH model, therefore, provides an excellent template to study how alterations in intestinal stem cells promote trans-differentiation, crypt regeneration or colon carcinogenesis following bacterial infection.

Chemokines induce axon outgrowth downstream of Hepatocyte Growth Factor and TCF/β-catenin signaling

Axon morphogenesis is a complex process regulated by a variety of secreted molecules, including morphogens and growth factors, resulting in the establishment of the neuronal circuitry. Our previous work demonstrated that growth factors [Neurotrophins (NT) and Hepatocyte Growth Factor (HGF)] signal through β-catenin during axon morphogenesis. HGF signaling promotes axon outgrowth and branching by inducing β-catenin phosphorylation at Y142 and transcriptional regulation of T-Cell Factor (TCF) target genes. Here, we asked which genes are regulated by HGF signaling during axon morphogenesis. An array screening indicated that HGF signaling elevates the expression of chemokines of the CC and CXC families. In line with this, CCL7, CCL20, and CXCL2 significantly increase axon outgrowth in hippocampal neurons. Experiments using blocking antibodies and chemokine receptor antagonists demonstrate that chemokines act downstream of HGF signaling during axon morphogenesis. In addition, qPCR data demonstrates that CXCL2 and CCL5 expression is stimulated by HGF through Met/b-catenin/TCF pathway. These results identify CC family members and CXCL2 chemokines as novel regulators of axon morphogenesis downstream of HGF signaling.

Mechanisms of RAS/β-catenin interactions

Signaling through the WNT/β-catenin and the RAS (rat sarcoma)/MAPK (mitogen-activated protein kinase) pathways plays a key role in the regulation of various physiological cellular processes including proliferation, differentiation, and cell death. Aberrant mutational activation of these signaling pathways is closely linked to the development of cancer in many organs, in humans as well as in laboratory animals. Over the past years, more and more evidence for a close linkage of the two oncogenic signaling cascades has accumulated. Using different experimental approaches, model systems, and experimental conditions, a variety of molecular mechanisms have been identified by which signal transduction through WNT/β-catenin and RAS interact, either in a synergistic or an antagonistic manner. Mechanisms of interaction comprise an upstream crosstalk at the level of pathway-activating ligands and their receptors, interrelations of cytosolic kinases involved in either pathways, as well as interaction in the nucleus related to the joint regulation of target gene transcription. Here, we present a comprehensive review of the current knowledge on the interaction of RAS/MAPK- and WNT/β-catenin-driven signal transduction in mammalian cells.