Cell adhesion and the integrin-linked kinase regulate the LEF-1 and beta-catenin signaling pathways

The Secretome of the Inductive Tooth Germ Exhibits Signals Required for Tooth Development

Teeth develop from reciprocal signaling between inductive and receptive cells. The inductive signals for tooth development are initially in the epithelium of the developing branchial arch, but later shift to the underlying mesenchyme of a developing tooth germ. The inductive signals that are needed for tooth development have not yet been fully identified. Our lab previously provided a basis for bioengineering new teeth by separating the tooth germ's epithelial and mesenchyme cells into a single cell population and recombing them. This approach, however, is not clinically applicable as the cells lose their inductive ability when expanded in vitro. In this study, we investigate whether the secretome and small extracellular vehicles (sEV) derived from inductive tooth germ mesenchyme can contribute to inductive signals required for tooth development. To address this, small extracellular vesicles and secretome were purified from inductive tooth germ mesenchyme and characterized. We investigated the proteome of sEV and proteome of inductive tooth germ mesenchyme and the impact of the culture condition and duration on the proteome. Additionally, we investigated the transcriptomic changes in tooth germ epithelium after treatment with sEV from inductive tooth germ mesenchyme. We show that culture duration of inductive tooth germ mesenchyme has an impact on the proteome of sEV purified from these cells. Similarly, culturing these cells in 2D and 3D environments results in different protein content. Proteome unique to sEV derived from inductive shows an association with multiple signaling pathways related to tooth development. Our RNASeq results show that treatment of tooth germ epithelial cells with small extracellular vesicles derived from inductive tooth germ mesenchyme results in an increased expression of some of the known odontogenic genes. Whilst further analysis is required to harvest the full potential of these sEV, our results suggests that extracellular vehicles contribute to signals required during tooth development, potentially through modulation of cellular metabolism and ECM organization.

TMEM182 inhibits myocardial differentiation of human iPS cells by maintaining the activated state of Wnt/β-catenin signaling through an increase in ILK expression

Transmembrane protein 182 (TMEM182) is notably abundant in muscle and adipose tissue, but its role in the heart remains unknown. This study examined the contribution of TMEM182 in the differentiation of human induced pluripotent stem cells (hiPSCs) into cardiomyocytes. For this, we generated hiPSCs overexpressing TMEM182 in a doxycycline-inducible manner and induced their differentiation into cardiomyocytes. On Day 12 of differentiation, expression of the cardiomyocyte markers, TNNT2 and MYH6, was significantly decreased in TMEM182-overexpressing cells. Additionally, we found that phosphorylation of GSK-3β (Ser9) and β-catenin (Ser552) was increased during TMEM182 overexpression, suggesting activation of Wnt/β-catenin signaling. We further focused on integrin-linked kinase (ILK) as the mechanism by which TMEM182 activates Wnt/β-catenin signaling. Evaluation showed that ILK expression was increased in cells overexpressing TMEM182. These results suggest that TMEM182 maintains Wnt/β-catenin signaling in an activated state after mesoderm formation by increasing ILK expression, thereby suppressing hiPSCs differentiation into cardiomyocytes.

Adapting to change: resolving the dynamic and dual roles of NCK1 and NCK2

Adaptor proteins play central roles in the assembly of molecular complexes and co-ordinated activation of specific pathways. Through their modular domain structure, the NCK family of adaptor proteins (NCK1 and NCK2) link protein targets via their single SRC Homology (SH) 2 and three SH3 domains. Classically, their SH2 domain binds to phosphotyrosine motif-containing receptors (e.g. receptor tyrosine kinases), while their SH3 domains bind polyproline motif-containing cytoplasmic effectors. Due to these functions being established for both NCK1 and NCK2, their roles were inaccurately assumed to be redundant. However, in contrast with this previously held view, NCK1 and NCK2 now have a growing list of paralog-specific functions, which underscores the need to further explore their differences. Here we review current evidence detailing how these two paralogs are unique, including differences in their gene/protein regulation, binding partners and overall contributions to cellular functions. To help explain these contrasting characteristics, we then discuss SH2/SH3 structural features, disordered interdomain linker regions and post-translational modifications. Together, this review seeks to highlight the importance of distinguishing NCK1 and NCK2 in research and to pave the way for investigations into the origins of their interaction specificity.

Tissue transglutaminase activates integrin-linked kinase and β-catenin in ovarian cancer

Ovarian cancer (OC) is the most lethal gynecological cancer. OC cells have high proliferative capacity, are invasive, resist apoptosis, and tumors often display rearrangement of extracellular matrix (ECM) components, contributing to accelerated tumor progression. The multifunctional protein tissue transglutaminase (TG2) is known to be secreted in the tumor microenvironment (TME), where it interacts with fibronectin (FN) and the cell surface receptor β1 integrin. However, the mechanistic role of TG2 in cancer cell proliferation is unknown. Here, we demonstrate TG2 directly interacts with and facilitates the phosphorylation and activation of the integrin effector protein integrin-linked kinase (ILK) at Ser246. We show TG2 and p-Ser246-ILK form a complex that is detectable in patient-derived OC primary cells grown on FN-coated slides. In addition, we show co-expression of TGM2 and ILK correlates with poor clinical outcome. Mechanistically, we demonstrate TG2-mediated ILK activation causes phosphorylation of glycogen synthase kinase-3α/β (GSK-3α/β), allowing β-catenin nuclear translocation and transcriptional activity. Furthermore, inhibition of TG2 and ILK using small molecules, neutralizing antibodies, or shRNA-mediated knockdown block cell adhesion to the FN matrix, as well as the Wnt receptor response to the Wnt-3A ligand, and ultimately, cell adhesion, growth, and migration. In conclusion, we demonstrate TG2 directly interacts with and activates ILK in OC cells and tumors, and define a new mechanism which links ECM cues with β-catenin signaling in OC. These results suggest a central role of TG2/FN/integrin clusters in ECM rearrangement and indicate downstream effector ILK may represent a potential new therapeutic target in OC.

POSTN promotes proliferation and epithelial-mesenchymal transition in renal cell carcinoma through ILK/AKT/mTOR pathway

Periostin (POSTN) is an extracellular matrix (ECM) protein, involved in various diseases. This research focused on the detailed mechanisms study of periostin (POSTN) overexpression in renal cell carcinoma (RCC) invasion and migration. Western blot and RT-PCR were performed to explore POSTN expression in various RCC cells. Cells were transfected with siRNAs or lentivirus to regulate the expression of POSTN. The effects of POSTN on cell viability, apoptosis, migration, invasion and epithelial-to-mesenchymal transition (EMT) of RCC cells were determined by CCK-8, flow cytometry, migration and invasion assay and Western blot analysis. POSTN expression was significantly enhanced in RCC cells compared with renal tubular epithelial cells. In vitro experiments showed that POSTN knockdown could dramatically inhibit RCC cell proliferation, migration and invasion, while overexpression of POSTN could promote these biological behaviors. We further demonstrated that POSTN knockdown suppressed epithelial-mesenchymal transition (EMT), which was mediated via upregulation of E-cadherin and downregulation of N-cadherin and vimentin, through IKL/AKT/mTOR pathway. In contrast, overexpression of POSTN could promote EMT in RCC cells via the activation of IKL /AKT/mTOR pathway. Next, we demonstrated that higher POSTN expression promoted angiogenesis in vivo in an RCC xenograft tumor via activating IKL /AKT/mTOR pathway. Our study showed that POSTN could promote EMT through ILK/AKT/mTOR pathway and might be an alternative therapeutic strategy for RCC treatment.

Integrating transcriptomes and somatic mutations to identify RNA methylation regulators as a prognostic marker in hepatocellular carcinoma

BACKGROUND

RNA methylation modifying plays an important role in the occurrence and progression of a range of human cancers including hepatocellular carcinoma (HCC), which is characterized by a mass of genetic and epigenetic alterations. However, the treatment targeting these alterations is limited.

METHODS

We used comprehensive bioinformatics analysis to analyze the correlation between cancer-associated RNA methylation regulators and HCC malignant features in network datasets.

RESULTS

We identified two HCC subgroups (cluster 1 and 2), which had clearly distinct clinicopathological, biofunctional and prognostic characteristics, by consensus clustering. The cluster 2 subgroup correlated with malignancy of the primary tumor, higher tumor stage, higher histopathological grade and higher frequency of TP53 mutation, as well as with shorter survival when compared with cluster 1. Gene enrichment indicated that the cluster 2 correlated to the tumor malignancy signaling and biological processes. Based on these findings, an 11-gene risk signature was built, which not only was an independent prognostic marker but also had an excellent power to predict the tumor features.

CONCLUSIONS

Our study indicated that RNA methylation regulators are vital for HCC malignant progression and provide an important evidence for RNA methylation, methylation regulators are actionable targets for anticancer drug discovery.

Integrin alpha-2 and beta-1 expression increases through multiple generations of the EDW01 patient-derived xenograft model of breast cancer-insight into their role in epithelial mesenchymal transition in vivo gained from an in vitro model system

Background

Breast cancers acquire aggressive capabilities via epithelial to mesenchymal transition (EMT), in which various integrins/integrin-linked kinase signalling are upregulated.

Methods

We investigated this in two patient-derived xenografts (PDXs) developed from breast-to-bone metastases, and its functional significance in a breast cancer cell line system. ED03 and EDW01 PDXs were grown subcutaneously in immunocompromised SCID mice through 11 passages and 7 passages, respectively. Tumour tissue was assessed using immunohistochemistry (IHC) for oestrogen receptor (ER)-alpha, E-cadherin, vimentin, Twist1, beta-catenin, P120-RasGAP, CD44, CD24 and Ki67, and RT-qPCR of EMT-related factors (CDH1, VIM, CD44, CD24), integrins beta 1 (ITGB1), alpha 2 (ITGA2) and ILK. Integrin and ILK expression in epidermal growth factor (EGF)-induced EMT of the PMC42-ET breast cancer cell line was assessed by RT-qPCR and Western blotting, as were the effects of their transient knockdown via small interfering RNA +/− EGF. Cell migration, changes in cell morphology and adhesion of siRNA-transfected PMC42-ET cells to various extracellular matrix (ECM) substrates was assessed.

Results

The ED03 (ER+/PR−/HER2−/lobular) and EDW01 (ER+/PR−/HER2−/ductal) PDXs were both classified as molecular subtype luminal A. ED03 xenografts exhibited mutated E-cadherin with minimal expression, but remained vimentin-negative across all passages. In EDW01, the hypoxic indicator gene CAIX and Twist1 were co-ordinately upregulated at passages 4–5, corresponding with a decrease in E-cadherin. At passages 6–7, VIM was upregulated along with ITGB1 and ITGA2, consistent with an increasing EMT. The ED03 PDX displayed minimal change over passages in mice, for all genes examined. ILK, ITGB1 and ITGA2 mRNAs were also increased in the EGF-induced EMT of PMC42-ET cells (in which CDH1 was downregulated) although siRNA against these targets revealed that this induction was not necessary for the observed EMT. However, their knockdown significantly reduced EMT-associated adhesion and Transwell migration.

Conclusion

Our data suggest that despite an increase in ITGA2 and ITGB1 gene expression in the EMT exhibited by EDW01 PDX over multiple generations, this pathway may not necessarily drive the EMT process.

Supplementary information

The online version contains supplementary material available at 10.1186/s13058-020-01366-8.

Microarray analysis identification of key pathways and interaction network of differential gene expressions during osteogenic differentiation

BACKGROUND

Adult bone marrow-derived mesenchymal stem cells (BM-MSCs) are multipotent stem cells that can differentiate into three lineages. They are suitable sources for cell-based therapy and regenerative medicine applications. This study aims to evaluate the hub genes and key pathways of differentially expressed genes (DEGs) related to osteogenesis by bioinformatics analysis in three different days. The DEGs were derived from the three different days compared with day 0.

RESULTS

Gene expression profiles of GSE37558 were obtained from the Gene Expression Omnibus (GEO) database. A total of 4076 DEGs were acquired on days 8, 12, and 25. Gene ontology (GO) enrichment analysis showed that the non-canonical Wnt signaling pathway and lipopolysaccharide (LPS)-mediated signaling pathway were commonly upregulated DEGs for all 3 days. KEGG pathway analysis indicated that the PI3K-Akt and focal adhesion were also commonly upregulated DEGs for all 3 days. Ten hub genes were identified by CytoHubba on days 8, 12, and 25. Then, we focused on the association of these hub genes with the Wnt pathways that had been enriched from the protein-protein interaction (PPI) by the Cytoscape plugin MCODE.

CONCLUSIONS

These findings suggested further insights into the roles of the PI3K/AKT and Wnt pathways and their association with osteogenesis. In addition, the stem cell microenvironment via growth factors, extracellular matrix (ECM), IGF1, IGF2, LPS, and Wnt most likely affect osteogenesis by PI3K/AKT.

The emerging potential of SIRT-3 in oxidative stress-inflammatory axis associated increased neuroinflammatory component for metabolically impaired neural cell

People suffering from conditions like epilepsy, where there is an excess of neuron excitement, stroke, and cardiac arrest, where there are oxygen and glucose deprivation, Alzheimer, Parkinson, and Huntington's disease that causes metabolic and also oxidative stress-inflammatory axis; are known to be more vulnerable to disturbances in the metabolism, and there is a lot of inadequacy in defining the inflammation's mechanistic connections, as well as neurodegeneration and the bioenergetic deficiencies in the CNS. We retrieved relevant studies from PubMed/ScienceDirect/Medline/Public library of science/Mendeley/Springer link as well as Google Scholar. We used various keywords both individually and in combination with the literature search. 'Epidemiology of neurodegenerative disorders', 'neurodegenerative diseases associated hyper inflammation', 'Mechanism of inflammation in neuronal cell', 'Involvement of SIRTin inflammation', 'Pathogenesis of mitochondrial associated metabolic impairment in neurons', 'Reactive oxygen species-mediated mitochondrial dysfunction' were a few of the keywords used for the search. PINCH, which is a chronic neuro-inflammatory component that cannot be detected in matured neurons which are healthy, though expressed in oxidative stress inflammatory axis related tauopathy and diseases that cause neurodegeneration. We attempted to study the regulatory mechanisms that cause changes in the bioenergetics and its neuronal defects and mitochondrial subcellular localization that are PINCH protein-mediated on the other handSIRT1, the most intensively studied sirtuin, in oxidative stress-mediated inflammatory consequence for many diseases but very few research data explore the role of SIRT-3 for correction of the chronic neuroinflammatory component. Thus, in this review, we investigate the very recently identified molecules involving in the pathogenesis during stimulated oxidative stress-inflammatory axis in the excitatory neuronal cell which changes brain metabolism. Simultaneously, in CNS neurons of diseases with a component of chronic neuroinflammation which exhibit neuroprotective response, the consequences (mechanistic and biological) of SIRT-3, could be emerging future targets for neurodegenerative disorder treatment with impaired metabolisms.

A proteomics outlook towards the elucidation of epithelial-mesenchymal transition molecular events

The main cause of death in cancer is the spread, or metastasis, of cancer cells to distant organs with consequent tumor formation. Additionally, metastasis is a process that demands special attention, as the cellular transformations make cancer at this stage very difficult or occasionally even impossible to be cured. The main process that converts epithelial tumor cells to mesenchymal-like metastatic cells is the Epithelial to Mesenchymal Transition (EMT). This process allows stationary and polarized epithelial cells, which are connected laterally to several types of junctions as well as the basement membrane, to undergo multiple biochemical changes that enable disruption of cell-cell adherence and apical-basal polarity. Moreover, the cells undergo important reprogramming to remodel the cytoskeleton and acquire mesenchymal characteristics such as enhanced migratory capacity, invasiveness, elevated resistance to apoptosis and a large increase in the production of ECM components. As expected, the alterations of the protein complement are extensive and complex, and thus exploring this by proteomic approaches is of particular interest. Here we review the overall findings of proteome modifications during EMT, mainly focusing on molecular signatures observed in multiple proteomic studies as well as coordinated pathways, cellular processes and their clinical relevance for altered proteins. As a result, an interesting set of proteins is highlighted as potential targets to be further investigated in the context of EMT, metastasis and cancer progression.

Molecular structure, expression, and functional role of Clec11a in skeletal biology and cancers

C-type lectin domain family 11 member A (Clec11a), also known as stem cell growth factor (SCGF), C-type lectin superfamily member 3 (CLECSF3), or osteolectin was initially identified as a growth factor for hematopoietic progenitor cells. The human Clec11a gene encodes a polypeptide of 323 amino acids with characteristics of a secreted glycoprotein encompassing two integrin-binding motifs, RGD (Arg-Gly-Asp) and LDT (Leu-Asp-Thr), a putative leucine zipper domain, and a functional C-type lectin domain. It regulates hematopoietic differentiation and homeostasis and exhibits a protective effect against severe malarial anemia and lipotoxicity. Furthermore, Clec11a promotes the differentiation of mesenchymal progenitors into mature osteoblasts in vitro and plays an important role in the maintenance of adult skeleton age-related bone loss and fracture repair. Receptor ligand binding results in activation of downstream signaling cascades including glycogen synthase kinase 3 (GSK3), β-catenin, and Wnt, resulting in the expression of osteoblast-related gene transcripts including Alp, Runx2, Lef1, and Axin2. In addition, Clec11a is also associated with the development of several cancers, including leukemia, multiple myeloma, and gastrointestinal tract tumors. To date, however, the mechanisms governing transcription regulation of the Clec11a gene are not known and remain to be uncovered. Understanding the function and mechanism of action of Clec11a will pave the way for the development of Clec11a as a novel therapeutic target for conditions such as cancer, anemia, and skeletal diseases.

Integrin-linked kinase controls retinal angiogenesis and is linked to Wnt signaling and exudative vitreoretinopathy

Familial exudative vitreoretinopathy (FEVR) is a human disease characterized by defective retinal angiogenesis and associated complications that can result in vision loss. Defective Wnt/β-catenin signaling is an established cause of FEVR, whereas other molecular alterations contributing to the disease remain insufficiently understood. Here, we show that integrin-linked kinase (ILK), a mediator of cell-matrix interactions, is indispensable for retinal angiogenesis. Inactivation of the murine Ilk gene in postnatal endothelial cells results in sprouting defects, reduced endothelial proliferation and disruption of the blood-retina barrier, resembling phenotypes seen in established mouse models of FEVR. Retinal vascularization defects are phenocopied by inducible inactivation of the gene for α-parvin (Parva), an interactor of ILK. Screening genomic DNA samples from exudative vitreoretinopathy patients identifies three distinct mutations in human ILK, which compromise the function of the gene product in vitro. Together, our data suggest that defective cell-matrix interactions are linked to Wnt signaling and FEVR.

Integrin-linked kinase (ILK) is an important mediator of integrin signaling. Here Park et al. show that mice with endothelial-specific deletion of Ilk develop vascular defects that resemble familial exudative vitreoretinopathy, and identify mutations in ILK in patients with exudative vitreoretinopathy suggesting a potential role in human pathogenesis.

Telomere erosion in Sjögren's syndrome: A multi-tissue comparative analysis

BACKGROUND

Acinar progenitor cells within salivary glands have decreased regenerative capacity and exhibit shorter telomeres in primary Sjögren's syndrome (pSS) patients. We investigated whether DNA of saliva, PBMCs, and labial salivary gland (LSG) biopsy tissue have shorter telomeres in pSS compared to controls. mRNA expression of genes associated with pSS pathogenesis (ETS1, LEF1, and MMP9), telomere DNA damage response (ATM), senescence (CDKN2A), telomerase inhibition (IFN-y, TGFβ1), and the shelterin complex (TPP1, POT1) were assessed in LSG tissue by qRT-PCR to examine potential defects in telomere maintenance.

METHODS

Relative telomere length in DNA of saliva, PBMCs, and LSGs from non-pSS sicca and pSS patients was measured using qPCR. Saliva DNA telomere length was further compared to healthy controls. Expression of genes affecting telomere maintenance was analyzed in LSGs using qRT-PCR.

RESULTS

Primary Sjögren's syndrome patients have shorter telomeres in saliva DNA (n = 21) than healthy controls (n = 27) (P = .0035). ATM mRNA expression was higher in pSS LSG tissue (n = 16) vs non-pSS sicca patients (n = 13) (P = .0283) and strongly correlated with LEF1, TPP1, and POT1 (P < .01, r > 0.6).

CONCLUSIONS

Patients with pSS exhibited significant telomere erosion in saliva DNA. Overexpression of ATM in LSGs could represent a compensatory response to telomere shortening. The role of LEF1 in telomere erosion remains to be elucidated.

Insulin attenuates apoptosis in neuronal cells by an integrin-linked kinase-dependent mechanism

Insulin promotes neuronal survival by activating a phosphatidylinositol 3-kinase (PI 3-kinase)/AKT-dependent signaling pathway and reducing caspase activation. We investigated a role for integrin-linked kinase (ILK) in insulin-mediated cell survival in cultured neurons and differentiated R28 cells. We used a serum and depolarization withdrawal model to induce apoptosis in cerebellar granule neurons and a serum withdrawal model to induce apoptosis in differentiated R28 cells. ILK knock-out decreased insulin-mediated protection as did the addition of pharmacological inhibitors of ILK, KP-392 or QLT-0267. Prosurvival effects of insulin were rescued by Boc-Asp (O-methyl)-CH₂F (BAF), a pancaspase inhibitor, in the presence of KP-392. Insulin and IGF-1 decreased caspase-3 activation, an effect that was inhibited by KP-392 and QLT-0267. Western blot analysis indicates that insulin-induced stimulation of AKT Ser-473 phosphorylation was decreased after the ILK gene was conditionally knocked-out, following overexpression of AKT-DN or in the presence of QLT-0267. Insulin and IGF-1 stimulated ILK kinase activity in primary neurons and this was inhibited following ILK-DN overexpression. Western blot analysis indicates that insulin exposure upregulated the expression of the cellular inhibitor of apoptosis protein c-IAP2 in an extracellular matrix-dependent manner, an effect blocked by KP-392. These results indicate that ILK is an important effector in insulin-mediated neuroprotection.

Integrin alpha11 is an Osteolectin receptor and is required for the maintenance of adult skeletal bone mass

We previously discovered a new osteogenic growth factor that is required to maintain adult skeletal bone mass, Osteolectin/Clec11a. Osteolectin acts on Leptin Receptor⁺ (LepR⁺) skeletal stem cells and other osteogenic progenitors in bone marrow to promote their differentiation into osteoblasts. Here we identify a receptor for Osteolectin, integrin α11, which is expressed by LepR⁺ cells and osteoblasts. α11β1 integrin binds Osteolectin with nanomolar affinity and is required for the osteogenic response to Osteolectin. Deletion of Itga11 (which encodes α11) from mouse and human bone marrow stromal cells impaired osteogenic differentiation and blocked their response to Osteolectin. Like Osteolectin deficient mice, Lepr-cre; Itga11^fl/fl mice appeared grossly normal but exhibited reduced osteogenesis and accelerated bone loss during adulthood. Osteolectin binding to α11β1 promoted Wnt pathway activation, which was necessary for the osteogenic response to Osteolectin. This reveals a new mechanism for maintenance of adult bone mass: Wnt pathway activation by Osteolectin/α11β1 signaling.

Throughout our lives, our bones undergo constant remodeling. Cells called osteoclasts break down old bone and cells called osteoblasts lay down new. Normally, the two cell types work in balance but if the rate of breakdown outpaces new bone formation the skeleton can become weak. This weakness leads to a condition called osteoporosis, in which people suffer from fragile bones. Osteoporosis is hard to reverse, in part because our ability to encourage new bone to form is limited.

In 2016, researchers discovered a protein called osteolectin, which promotes new bone formation during adulthood by helping skeletal stem cells transform into bone cells. But so far, it has been unclear how osteolectin achieves this. To investigate this further, Shen et al. – including some researchers involved in the 2016 study – marked osteolectin with a molecular tag and tested what it bound on the surface of mouse and human bone marrow cells.

The experiments revealed that osteolectin binds to a specific receptor protein called α11 integrin, which can only be found on skeletal stem cells and the osteoblasts they give rise to. Once osteolectin binds to the receptor, it activates a signaling pathway that induces the stem cells to develop into osteoblasts. Mice that lacked either osteolectin or α11 integrin produced less bone and lost bone tissue faster as adults.

Osteolectin could potentially be useful in the treatment of osteoporosis or broken bones. Since only skeletal stem cells and osteoblasts cells produce α11 integrin, osteolectin would specifically target these cells without affecting cells that do not form bones. A next step will be to assess how well osteolectin compares to existing treatments for fragile bones.

Significance of integrin-linked kinase (ILK) in tumorigenesis and its potential implication as a biomarker and therapeutic target for human cancer

Integrin-linked kinase (ILK), which is an ankyrin repeat-containing serine/threonine protein kinase, interacts with integrin β1 and the β3 cytoplasmic domain and phosphorylates integrin β1. ILK has multiple functions in cells, such as cell-extracellular matrix interactions, cell cycle, apoptosis, cell proliferation and cell motility, which are associated with the interacting partners of ILK and downstream signaling pathways. Upregulation of ILK is frequently observed in cancer tissues compared to corresponding normal tissues. Emerging evidence has demonstrated that ILK plays an important role in biological processes associated with tumorigenesis, including cancer cell proliferation, angiogenesis, metastasis, and drug resistance. Furthermore, inhibition of ILK expression and activity using siRNA or chemical inhibitors has shown a significant suppressive effect on cancer development and progression, implicating the potential of ILK as a target for cancer treatment. In this review, we summarized the functional role of ILK in tumorigenesis, with the expectation that targeting ILK could provide more evidence for cancer therapy.

MicroRNA therapeutics: design of single-stranded miR-216b mimics to target KRAS in pancreatic cancer cells

Datasets reporting microRNA expression profiles in normal and cancer cells show that miR-216b is aberrantly downregulated in pancreatic ductal adenocarcinoma (PDAC). We found that KRAS, whose mutant G12D allele drives the pathogenesis of PDAC, is a target of miR-216b. To suppress oncogenic KRAS in PDAC cells, we designed single-stranded (ss) miR-216b mimics with unlocked nucleic acid (UNA) modifications to enhance their nuclease resistance. We prepared variants of ss-miR-216b mimics with and without a 5ʹ phosphate group. Both variants strongly suppressed oncogenic KRAS in PDAC cells and inhibited colony formation in pancreatic cancer cells. We observed that the designed ss-miR-216b mimics engaged AGO2 to promote the silencing of KRAS. We also tested a new delivery strategy based on the use of palmityl-oleyl-phosphatidylcholine (POPC) liposomes functionalized with ss-miR-216b conjugated with two palmityl chains and a lipid-modified cell penetrating peptide (TAT). These versatile nanoparticles suppressed oncogenic KRAS in PDAC cells.

Cell-cell adhesion: linking Wnt/β-catenin signaling with partial EMT and stemness traits in tumorigenesis

Changes in cell adhesion and motility are considered key elements in determining the development of invasive and metastatic tumors. Co-opting the epithelial-to-mesenchymal transition (EMT) process, which is known to occur during embryonic development, and the associated changes in cell adhesion properties in cancer cells are considered major routes for tumor progression. More recent in vivo studies in tumor tissues and circulating tumor cell clusters suggest a stepwise EMT process rather than an “all-or-none” transition during tumor progression. In this commentary, we addressed the molecular mechanisms underlying the changes in cell adhesion and motility and adhesion-mediated signaling and their relationships to the partial EMT states and the acquisition of stemness traits by cancer cells.

ILK Expression in Colorectal Cancer Is Associated with EMT, Cancer Stem Cell Markers and Chemoresistance

BACKGROUND/AIM

Epithelial-mesenchymal transition (EMT) and cancer stem cells (CSC) are critically implicated in cancer metastasis and chemoresistance. Herein, we investigated integrin-linked kinase (ILK)'s role in human colon cancer (CRC) progression and chemoresistance in relation to EMT and CSC markers.

PATIENTS AND METHODS

Expression of ILK, EMT and CSC markers were evaluated by immunohistochemistry in 149 CRC samples. We also generated colon cancer cells resistant to 5-FU and oxaliplatin and studied the effect of ILK inhibition on drug response by MTT assay and on EMT and CSC markers' expression.

RESULTS

ILK expression in human CRC correlates with EMT and CSC markers and is associated with metastasis and chemoresistance. ILK inhibition increases sensitivity of resistant cells to 5-FU and oxaliplatin and reduces the levels of EMT and CSC markers in 5-FU resistant cells.

CONCLUSION

ILK overexpression in human CRC associates with EMT and CSC traits, contributing to tumor progression and chemoresistance.

Expression/activation of α5β1 integrin is linked to the β-catenin signaling pathway to drive migration in glioma cells

The Wnt/beta catenin pathway has been highlighted as an important player of brain tumors aggressiveness and resistance to therapies. Increasing knowledges of the regulation of beta-catenin transactivation point out its hub position in different pathophysiological outcomes in glioma such as survival and migration. Crosstalks between integrins and beta-catenin pathways have been suggested in several tumor tissues. As we demonstrated earlier that α5β1 integrin may be considered as a therapeutic target in high grade glioma through its contribution to glioma cell migration and resistance to chemotherapy, we addressed here the potential relationship between α5β1 integrin and beta-catenin activation in glioma cells. We demonstrated that overexpression and activation by fibronectin of α5β1 integrin allowed the transactivation of beta-catenin gene targets included in an EMT-like program that induced an increase in cell migration. Hampering of beta catenin activation and cell migration could be similarly achieved by a specific integrin antagonist. In addition we showed that α5β1 integrin/AKT axis is mainly involved in these processes. However, blockade of beta-catenin by XAV939 (tankyrase inhibitor leading to beta-catenin degradation) did not synergize with p53 activation aiming to cell apoptosis as was the case with integrin antagonists. We therefore propose a dual implication of α5β1 integrin/AKT axis in glioma cell resistance to therapies and migration each supported by different signaling pathways. Our data thus suggest that α5β1 integrin may be added to the growing list of beta-catenin modulators and provide new evidences to assign this integrin as a valuable target to fight high grade glioma.

HMGA1 participates in MHCC97H cell proliferation and invasion through the ILK/Akt/GSK3β signaling pathway

Hepatocellular carcinoma (HCC) is one of the major causes of cancer‑related mortality, and the prognosis of HCC patients is unsatisfactory. It is known that the occurrence and development of HCC involves numerous genes, as well as various steps and stages in the pathological process. High mobility group AT‑hook 1 (HMGA1) and integrin‑linked kinase (ILK) may be overexpressed in HCC and may serve important roles in the development of cancer; however, the relationship between HMGA1 and ILK in HCC has not been examined. The present study demonstrated that inhibition of HMGA1 expression significantly decreased the levels of expression of ILK and the downstream elements phosphorylated (p)‑Akt, p‑glycogen synthase kinase 3β (GSK3β), matrix metalloproteinase (MMP)2, MMP9, CyclinD1 and c‑Myc. Transfection with an ILK expression vector was able to recover the decreased expression of these downstream genes, and affected cell proliferation and apoptosis. In addition, results from Transwell and wound‑healing experiments indicated that HMGA1 participates cell invasion and migration through the ILK/Akt/GSK3β pathway. The present study aimed to improve our understanding about the regulatory pathway involved in HCC and provides the basis for exploring HMGA1 inhibition as a therapy for patients with HCC and a new treatment strategy to prevent the development of HCC.

A proteomic analysis of LRRK2 binding partners reveals interactions with multiple signaling components of the WNT/PCP pathway

BACKGROUND

Autosomal-dominant mutations in the Park8 gene encoding Leucine-rich repeat kinase 2 (LRRK2) have been identified to cause up to 40% of the genetic forms of Parkinson's disease. However, the function and molecular pathways regulated by LRRK2 are largely unknown. It has been shown that LRRK2 serves as a scaffold during activation of WNT/β-catenin signaling via its interaction with the β-catenin destruction complex, DVL1-3 and LRP6. In this study, we examine whether LRRK2 also interacts with signaling components of the WNT/Planar Cell Polarity (WNT/PCP) pathway, which controls the maturation of substantia nigra dopaminergic neurons, the main cell type lost in Parkinson's disease patients.

METHODS

Co-immunoprecipitation and tandem mass spectrometry was performed in a mouse substantia nigra cell line (SN4741) and human HEK293T cell line in order to identify novel LRRK2 binding partners. Inhibition of the WNT/β-catenin reporter, TOPFlash, was used as a read-out of WNT/PCP pathway activation. The capacity of LRRK2 to regulate WNT/PCP signaling in vivo was tested in Xenopus laevis' early development.

RESULTS

Our proteomic analysis identified that LRRK2 interacts with proteins involved in WNT/PCP signaling such as the PDZ domain-containing protein GIPC1 and Integrin-linked kinase (ILK) in dopaminergic cells in vitro and in the mouse ventral midbrain in vivo. Moreover, co-immunoprecipitation analysis revealed that LRRK2 binds to two core components of the WNT/PCP signaling pathway, PRICKLE1 and CELSR1, as well as to FLOTILLIN-2 and CULLIN-3, which regulate WNT secretion and inhibit WNT/β-catenin signaling, respectively. We also found that PRICKLE1 and LRRK2 localize in signalosomes and act as dual regulators of WNT/PCP and β-catenin signaling. Accordingly, analysis of the function of LRRK2 in vivo, in X. laevis revelaed that LRKK2 not only inhibits WNT/β-catenin pathway, but induces a classical WNT/PCP phenotype in vivo.

CONCLUSIONS

Our study shows for the first time that LRRK2 activates the WNT/PCP signaling pathway through its interaction to multiple WNT/PCP components. We suggest that LRRK2 regulates the balance between WNT/β-catenin and WNT/PCP signaling, depending on the binding partners. Since this balance is crucial for homeostasis of midbrain dopaminergic neurons, we hypothesize that its alteration may contribute to the pathophysiology of Parkinson's disease.

Human steroid sulfatase induces Wnt/β-catenin signaling and epithelial-mesenchymal transition by upregulating Twist1 and HIF-1α in human prostate and cervical cancer cells

Steroid sulfatase (STS) catalyzes the hydrolysis of estrone sulfate and dehydroepiandrosterone sulfate (DHEAS) to their unconjugated biologically active forms. Although STS is considered a therapeutic target for estrogen-dependent diseases, the cellular functions of STS remain unclear. We found that STS induces Wnt/β-catenin s Delete ignaling in PC-3 and HeLa cells. STS increases levels of β-catenin, phospho-β-catenin, and phospho-GSK3β. Enhanced translocation of β-catenin to the nucleus by STS might activate transcription of target genes such as cyclin D1, c-myc, and MMP-7. STS knockdown by siRNA resulted in downregulation of Wnt/β-catenin signaling. β-Catenin/TCF-mediated transcription was also enhanced by STS. STS induced an epithelial-mesenchymal transition (EMT) as it reduced the levels of E-cadherin, whereas levels of mesenchymal markers such as N-cadherin and vimentin were enhanced. We found that STS induced Twist1 expression through HIFα activation as HIF-1α knockdown significantly blocks the ability of STS to induce Twist1 transcription. Furthermore, DHEA, but not DHEAS is capable of inducing Twist1. Treatment with a STS inhibitor prevented STS-mediated Wnt/β-catenin signaling and Twist1 expression. Interestingly, cancer cell migration, invasion, and MMPs expression induced by STS were also inhibited by a STS inhibitor. Taken together, these results suggest that STS induces Wnt/β-catenin signaling and EMT by upregulating Twist1 and HIF-1α. The ability of STS to induce the Wnt/β-catenin signaling and EMT has profound implications on estrogen-mediated carcinogenesis in human cancer cells.

Effect of Huayu Tongluo Herbs on Reduction of Proteinuria via Inhibition of Wnt/β-Catenin Signaling Pathway in Diabetic Rats

The study investigated the expression of Wnt/β-catenin pathway in diabetic rats and the intervention effect of Huayu Tongluo herbs (HTH). Ten rats were randomly selected as control group and the remaining rats were established as diabetic models. The diabetic rats were randomly divided into model group and HTH treatment group. The intervention was intragastric administration in all rats for 20 weeks. At the end of every 4 weeks, fasting blood glucose and 24 h urinary total protein quantitatively were measured. At the end of the 20th week, biochemical parameters and body weight were tested. The kidney tissues were observed under light microscope and transmission electron microscopy. We examined Wnt/beta-catenin signaling pathway key proteins and renal interstitial fibrosis related molecular markers expression. The results showed that HTH could reduce urinary protein excretion and relieve renal pathological damage. Wnt4, p-GSK3β (S9), and β-catenin expression were decreased in the signaling pathway, but GSK3β level was not changed by HTH in diabetic rats. Furthermore, the expressions of TGF-β1 and ILK were decreased, but the level of E-cadherin was increased in diabetic rats after treatment with HTH. This study demonstrated that HTH could inhibit the high expression of Wnt/β-catenin pathway in kidney of diabetic rats. The effect might be one of the main ways to reduce urinary protein excretion.

Correlation between PKB/Akt, GSK-3β expression and tubular epithelial-mesenchymal transition in renal allografts with chronic active antibody-mediated rejection

Chronic antibody-mediated rejection (ABMR) is a major cause of the transplant renal interstitial fibrosis and transplanted kidney epithelial cell transdifferentiation is one of the main mechanisms. The transforming growth factor (TGF)-β1/integrin-linked kinase (ILK) signaling pathway has a significant role in the epithelial-mesenchymal transition (EMT) of renal tubular epithelial cells; however, the molecular mechanisms of this process have remained elusive. The present study confirmed that Akt and glycogen synthase kinase (GSK)-3β, as TGF-β1 downstream signaling factors, are involved in fibrotic processes caused by kidney disease, which, however, has been rarely reported in the kidney transplant field. Based on the Banff 2009 standard, transplanted kidney specimens were classified according to the fibrosis level. The results showed that with the reduction of the interstitial fibrosis level, E-cadherin expression was gradually reduced, while α-smooth muscle actin expression progressively increased. The expression of Akt and GSK-3β in normal human kidney tissue was not obvious but showed a marked increase with the aggravation of the interstitial fibrosis level, which confirmed the occurrence of EMT during the fibrosis process, and that phosphorylated (p)-Akt and GSK-3β have an important role in the EMT process in the transplanted kidney. A correlation analysis of p-Akt, GSK-3β, TGF-β1 and ILK suggested that overexpression of p-Akt and GSK-3β may induce and mediate the transdifferentiation of renal tubular epithelial cells to myofibroblasts and that this proceeds via TGFβ1/ILK signaling pathways.

Localization and Level of Expression of β-Catenin in Human Laryngeal Squamous Cell Carcinoma

OBJECTIVE: We studied the participation of β-catenin in the histologic differentiation of laryngeal squamous cell carcinomas.

STUDY DESIGN AND SETTING: At the National Institute of Respiratory Diseases, a tertiary referral center, localization and level of expression of β-catenin were compared between normal epithelium (15 cases) and primary tumors in different degrees of differentiation (38 cases), using an immunohistochemical procedure.

RESULTS: Cell membrane staining of β-catenin was observed in normal epithelium and in well and moderately differentiated carcinomas. Cytoplasmic redistribution was observed in poorly differentiated carcinomas. Loss of β-catenin correlated with tumor dedifferentiation.

CONCLUSION: Reduction of cell membrane β-catenin expression correlated with tumor dedifferentiation.

SIGNIFICANCE: Loss of β-catenin may lead to diminishing the strength of the intercellular adhesion system, thereby promoting the invasive phenotype of the squamous cell carcinoma of the larynx.

Integrin-linked kinase regulates cadherin switch in bladder cancer

Cadherin switch is specific of epithelial-mesenchymal transition (EMT) and is closely related to tumor cell invasion. However, the molecular mechanism that promotes the phenotypic changes remains unclear and elusive. We found that integrin-linked kinase (ILK) is a key factor involved in cadherin switch. The expression and activity of ILK are elevated in a variety of cancers but its mechanisms are not exactly understood. In this report, we studied the role and mechanism of ILK in EMT of human bladder cancer. We showed that silencing of ILK expression by small interfering RNA (siRNA) significantly abolished the nuclear translocation or the presence of markers associated with EMT like Snail, Twist, Zeb, and beta-catenin. ILK knockdown by siRNA suppressed N-cadherin expression and increased re-expression of E-cadherin in bladder cancer cells. We suggest that ILK is a major signaling factor involved in EMT. It is essential to understand the molecular mechanism of EMT in aim to possibly use it in search for new therapeutic targets.

Expression of an Activated Integrin Promotes Long-Distance Sensory Axon Regeneration in the Spinal Cord

After CNS injury, axon regeneration is blocked by an inhibitory environment consisting of the highly upregulated tenascin-C and chondroitin sulfate proteoglycans (CSPGs). Tenascin-C promotes growth of axons if they express a tenascin-binding integrin, particularly α9β1. Additionally, integrins can be inactivated by CSPGs, and this inhibition can be overcome by the presence of a β1-binding integrin activator, kindlin-1. We examined the synergistic effect of α9 integrin and kindlin-1 on sensory axon regeneration in adult rat spinal cord after dorsal root crush and adeno-associated virus transgene expression in dorsal root ganglia. After 12 weeks, axons from C6-C7 dorsal root ganglia regenerated through the tenascin-C-rich dorsal root entry zone into the dorsal column up to C1 level and above (>25 mm axon length) through a normal pathway. Animals also showed anatomical and electrophysiological evidence of reconnection to the dorsal horn and behavioral recovery in mechanical pressure, thermal pain, and ladder-walking tasks. Expression of α9 integrin or kindlin-1 alone promoted much less regeneration and recovery.

SIGNIFICANCE STATEMENT

The study demonstrates that long-distance sensory axon regeneration over a normal pathway and with sensory and sensory-motor recovery can be achieved. This was achieved by expressing an integrin that recognizes tenascin-C, one of the components of glial scar tissue, and an integrin activator. This enabled extensive long-distance (>25 mm) regeneration of both myelinated and unmyelinated sensory axons with topographically correct connections in the spinal cord. The extent of growth and recovery we have seen would probably be clinically significant. Restoration of sensation to hands, perineum, and genitalia would be a significant improvement for a spinal cord-injured patient.

Integral membrane protease fibroblast activation protein sensitizes fibrosarcoma to chemotherapy and alters cell death mechanisms

Fibroblast activation protein (FAP), an integral membrane serine protease, is found on fibro- and osteo-sarcoma and on myofibroblasts in epithelial carcinoma, but rarely on other adult tissue. FAP has been demonstrated to be an excellent target for tumor imaging in clinical trials, and antibodies and other FAP-targeting drugs are in development. Here we have shown that FAP overexpression increased the growth of HT1080 fibrosarcoma cells in vitro and in vivo, and found that the expression of FAP affects response to chemotherapy. When treated with doxorubicin, expression of FAP increased susceptibility to the drug. In spite of this, FAP-HT1080 cells had fewer markers of classical apoptosis than HT1080 cells and neither necrosis nor necroptosis were enhanced. However, levels of early mitochondrial and lysosomal membrane permeability markers were increased, and autophagy switched from a protective function in HT1080 cells to part of the cell death mechanism with FAP expression. Therefore, FAP may affect how the tumor responds to chemotherapeutic drugs overall, which should be considered in targeted drug development. The overexpression of FAP also alters cell signaling and responses to the environment in this cell line. This includes cell death mechanisms, changing the response of HT1080 cells to doxorubicin from classical apoptosis to an organelle membrane permeability-dependent form of cell death.

Comparison of ILK and ERP29 expressions in benign and malignant pancreatic lesions and their clinicopathological significances in pancreatic ductal adenocarcinomas

INTRODUCTION

Pancreatic ductal adenocarcinoma (PDAC) is a highly malignant tumor of the pancreas with poor prognosis. The lack of understanding of the molecular mechanisms of PDAC and biomarkers for early diagnosis might be two of the reasons for the poor prognosis of PDAC.

MATERIALS AND METHODS

ILK and ERP29 protein expressions in PDAC, peritumoral tissues, benign pancreatic lesions, and normal pancreatic tissues were measured by immunohistochemistry and the clinical and pathological significances of ILK and ERP29 in PDAC were analyzed.

RESULTS

The percentages of positive ILK and negative ERP29 expressions were significantly higher in PDAC tumors than in peritumoral tissues, benign pancreatic tissues, and normal pancreatic tissues (P < 0.01). Benign pancreatic lesions with positive ILK and negative ERP29 expressions exhibited dysplasia or intraepithelial neoplasia. The percentage of cases with positive ILK and negative ERP29 expressions was significantly lower in PDAC patients without lymph node metastasis and invasion, and having TNM stage I/II disease than in patients with lymph node metastasis, invasion, and TNM stage III/IV disease (P < 0.05 or P < 0.01). Kaplan-Meier survival analysis showed that positive ILK and negative ERP29 expressions were significantly associated with survival in PDAC patients (P < 0.001). Cox multivariate analysis revealed that positive ILK and negative ERP29 expressions were independent poor prognosis factors in PDAC patients.

CONCLUSIONS

Positive ILK and negative ERP29 expressions are associated with the progression of PDAC and poor prognosis in patients with PDAC.

Preservation of human limbal epithelial progenitor cells on carbodiimide cross-linked amniotic membrane via integrin-linked kinase-mediated Wnt activation

The Wnt pathway is a major signaling pathway that regulates corneal epithelial stem cells. However, little is known about how the ultrastructure of the limbal epithelial basement membrane (EBM) affects Wnt activity. Due to its enhanced matrix stability, the cross-linked amniotic membrane (AM) has gained increasing interest in the field of regenerative medicine. For the first time, we used EDC/NHS cross-linked denuded AM (CLDAM) as a simulated EBM substrate to investigate this mechanism. Human limbal epithelial (HLE) cells were cultured on dishes (HLE/dish), denuded AM (HLE/DAM) or CLDAM (HLE/CLDAM). Compared with HLE/dish or HLE/DAM cultures, HLE/CLDAM cultures showed greater BrdU retention and colony formation efficiency and expressed higher levels of p63, ABCG2, integrin β1, and integrin-linked kinase (ILK). Nuclear β-catenin and TCF-4 levels were higher in HLE/CLDAM cultures compared with HLE cells cultured on collagen IV, laminin, Matrigel, or DAM. Silencing of ILK in HLE/CLDAM cultures resulted in decreased levels of nuclear β-catenin, TCF-4 and deltaNp63α, whereas cytokeratin 12 expression increased. Over-expression of ILK in HLE/dish cultures had the opposite effects. Accordingly, we proposed that the CLDAM matrix, with its higher rigidity and rougher ultrastructure, better preserved HLE progenitor cells in vitro, possibly by activating integrin β1/ILK, which indirectly activated Wnt/β-catenin and subsequently deltaNp63α. Crosstalk between the integrin β1/ILK and Wnt/β-catenin pathways appears to play a crucial role in limbal progenitor cell survival on EBM.

STATEMENT OF SIGNIFICANCE

We demonstrated the superior capability of carbodiimide cross-linked denuded amniotic membrane (CLDAM) than natural DAM to preserve limbo-corneal epithelial progenitor cells in vitro, then we used CLDAM as a simulated epithelial basement membrane (EBM) to study how EBM maintains limbal epithelial stem cells (LESCs). We found that integrin-linked kinase (ILK) is an important mediator that transfers survival signals detected by integrin β1 to the Wnt/β-catenin pathway, which in turn up-regulates deltaNp63α, a master gene that regulates LESC function. The rougher surface of the limbal EBM suggests that the surface complexity of the LESC niche may be important in regulating LESC function, which is triggered by the recognition of topographic cues by integrin β1, followed by activation of the ILK/Wnt/β-catenin/p63 cascade.

Glycogen synthase kinase-3β inhibitor ameliorates imbalance of connexin 43 in an acute kidney injury model

This study was designed to evaluate whether glycogen synthase kinase-3β (GSK-3β) inhibitor, 4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione (TDZD-8) induced the the expression of connexin 43 (Cx43) to protect against renal ischemia–reperfusion (I/R) injury (RI/RI) in rats. Rats were subjected to 45 min ischemia followed 2 h reperfusion with TDZD-8 (1 mg/kg) for 5 min prior to reperfusion. The results indicated that TDZD-8 improved the recovery of renal function, reduced oxidative stress and inflammation injury, and upregulated the expression of (Cx43) as compared to I/R group. Therefore, our study demonstrated that TDZD-8 provided a protection to the kidney against I/R injury in rats through inducing the expression of (Cx43).

Different exercise modalities have distinct effects on the integrin-linked kinase (ILK) and Ca2+ signaling pathways in the male rat bone

Mechanical loading is essential to maintain optimal skeletal health. Despite the fact that early-life exercise has positive, long-lasting effects on the musculo-skeletal system, the response of the musculo-skeletal system to spontaneous low-impact exercise has been poorly studied. Previously, we identified subtle morphological changes in the femoral diaphysis of exercised animals compared to nonexercised controls. We hypothesized that significant changes in gene expression of cells should precede significant measurable phenotypic changes in the tissues of which they are part. Here, we employed RNA-Seq to analyse the transcriptome of the cortical bone from the femoral mid-diaphysis of prepubertal male Sprague-Dawley rats that were assigned to control (CON); bipedal stance (BPS); or wheel exercise (WEX) groups for 15 days. We identified 808 and 324 differentially expressed transcripts in the BPS and WEX animals respectively. While a number of transcripts change their levels in an exercise-specific manner, we identified 191 transcripts that were differentially expressed in both BPS and WEX. Importantly, we observed that the exercise mode had diametrically opposite effects on transcripts for multiple genes within the integrin-linked kinase (ILK) and Ca(2+) signaling pathways such that they were up-regulated in BPS and down-regulated in WEX. The findings are important for our understanding of possible ways in which different exercise regimens might affect bone when normal activities apply mechanical stimuli during postnatal growth and development.

TMIGD1 is a novel adhesion molecule that protects epithelial cells from oxidative cell injury

Oxidative damage to renal tubular epithelial cells is a fundamental pathogenic mechanism implicated in both acute kidney injury and chronic kidney diseases. Because epithelial cell survival influences the outcome of acute kidney injury and chronic kidney diseases, identifying its molecular regulators could provide new insight into pathobiology and possible new therapeutic strategies for these diseases. We have identified transmembrane and immunoglobulin domain-containing 1 (TMIGD1) as a novel adhesion molecule, which is highly conserved in humans and other species. TMIGD1 is expressed in renal tubular epithelial cells and promotes cell survival. The extracellular domain of TMIGD1 contains two putative immunoglobulin domains and mediates self-dimerization. Our data suggest that TMIGD1 regulates transepithelial electric resistance and permeability of renal epithelial cells. TMIGD1 controls cell migration, cell morphology, and protects renal epithelial cells from oxidative- and nutrient-deprivation-induced cell injury. Hydrogen peroxide-induced oxidative cell injury downregulates TMIGD1 expression and targets it for ubiquitination. Moreover, TMIGD1 expression is significantly affected in both acute kidney injury and in deoxy-corticosterone acetate and sodium chloride (deoxy-corticosterone acetate salt)-induced chronic hypertensive kidney disease mouse models. Taken together, we have identified TMIGD1 as a novel cell adhesion molecule expressed in kidney epithelial cells that protects kidney epithelial cells from oxidative cell injury to promote cell survival.

HANAC Syndrome Col4a1 Mutation Causes Neonate Glomerular Hyperpermeability and Adult Glomerulocystic Kidney Disease

Hereditary angiopathy, nephropathy, aneurysms, and muscle cramps (HANAC) syndrome is an autosomal dominant syndrome caused by mutations in COL4A1 that encodes the α1 chain of collagen IV, a major component of basement membranes. Patients present with cerebral small vessel disease, retinal tortuosity, muscle cramps, and kidney disease consisting of multiple renal cysts, chronic kidney failure, and sometimes hematuria. Mutations producing HANAC syndrome localize within the integrin binding site containing CB3[IV] fragment of the COL4A1 protein. To investigate the pathophysiology of HANAC syndrome, we generated mice harboring the Col4a1 p.Gly498Val mutation identified in a family with the syndrome. Col4a1 G498V mutation resulted in delayed glomerulogenesis and podocyte differentiation without reduction of nephron number, causing albuminuria and hematuria in newborns. The glomerular defects resolved within the first month, but glomerular cysts developed in 3-month-old mutant mice. Abnormal structure of Bowman's capsule was associated with metalloproteinase induction and activation of the glomerular parietal epithelial cells that abnormally expressed CD44,α-SMA, ILK, and DDR1. Inflammatory infiltrates were observed around glomeruli and arterioles. Homozygous Col4a1 G498V mutant mice additionally showed dysmorphic papillae and urinary concentration defects. These results reveal a developmental role for the α1α1α2 collagen IV molecule in the embryonic glomerular basement membrane, affecting podocyte differentiation. The observed association between molecular alteration of the collagenous network in Bowman's capsule of the mature kidney and activation of parietal epithelial cells, matrix remodeling, and inflammation may account for glomerular cyst development and CKD in patients with COL4A1-related disorders.

Wnt/β-catenin signaling mediates osteoblast differentiation triggered by peptide-induced α5β1 integrin priming in mesenchymal skeletal cells

The α5β1 integrin is a key fibronectin (FN) receptor that binds to RGD-containing peptides to mediate cell adhesion. We previously reported that α5β1 integrin promotes osteogenic differentiation in mesenchymal skeletal cells (MSCs), but the underlying mechanisms are not fully understood. In this study, we determined the signaling mechanisms induced by α5β1 integrin interaction with its high-affinity ligand CRRETAWAC in murine and human MSCs and in vivo. We show that cyclized CRRETAWAC fully displaced MSC adhesion to FN, whereas related peptides lacking the full RRET sequence produced a partial displacement, indicating that RRET acts as an RGD-like sequence that is required to antagonize FN-mediated cell adhesion. However, all peptides increased focal adhesion kinase phosphorylation, OSE2 transcriptional activity, osteoblast gene expression, and matrix mineralization in MSCs, indicating that peptide-induced α5β1 integrin priming can promote osteogenic differentiation independently of the RRET sequence. Biochemical analyses showed that peptide-induced α5β1 integrin priming transiently increased PI3K/Akt phosphorylation and promoted Wnt/β-catenin transcriptional activity independently of RRET. Consistently, pharmacological inhibition of PI3K activity reduced osteoblast differentiation and abolished Wnt regulatory gene expression induced by α5β1 integrin priming. In vivo, systemic delivery of cyclized GACRETAWACGA linked to (DSS)6 to allow delivery to bone-forming sites for 6 weeks increased serum osteocalcin levels and improved long bone mass and microarchitecture in SAMP-6 senescent osteopenic mice. The results support a mechanism whereby α5β1 integrin priming by high-affinity ligands integrates Wnt/β-catenin signaling to promote osteoblast differentiation independently of cell adhesion, which could be used to improve bone mass and microarchitecture in the aging skeleton.

From mechanical stimulation to biological pathways in the regulation of stem cell fate

Mechanical stimuli are important in directing the fate of stem cells; the effects of mechanical stimuli reported in recent research are reviewed here. Stem cells normally undergo two fundamental processes: proliferation, in which their numbers multiply, and differentiation, in which they transform into the specialized cells needed by the adult organism. Mechanical stimuli are well known to affect both processes of proliferation and differentiation, although the complete pathways relating specific mechanical stimuli to stem cell fate remain to be elucidated. We identified two broad classes of research findings and organized them according to the type of mechanical stress (compressive, tensile or shear) of the stimulus. Firstly, mechanical stress of any type activates stretch-activated channels (SACs) on the cell membrane. Activation of SACs leads to cytoskeletal remodelling and to the expression of genes that regulate the basic growth, survival or apoptosis of the cells and thus regulates proliferation. Secondly, mechanical stress on cells that are physically attached to an extracellular matrix (ECM) initiates remodelling of cell membrane structures called integrins. This second process is highly dependent on the type of mechanical stress applied and result into various biological responses. A further process, the Wnt pathway, is also implicated: crosstalk between the integrin and Wnt pathways regulates the switch from proliferation to differentiation and finally regulates the type of differentiation. Therefore, the stem cell differentiation process involves different signalling molecules and their pathways and most likely depends upon the applied mechanical stimulation.

Caveolin-1 promotes gastric cancer progression by up-regulating epithelial to mesenchymal transition by crosstalk of signalling mechanisms under hypoxic condition

Gastric cancer is the second most fatal common form of cancer. The crosstalk among signalling pathways that results in the acceleration of epithelial to mesenchymal transition (EMT) plays a pivotal role in the molecular mechanism of gastric carcinogenesis. To understand the role of caveolin-1 (Cav-1), the expression pattern was studied in human gastric adenocarcinoma tissues and also in AGS and KATO III cell lines. Here, we show that during hypoxic condition, the increase in the levels of hypoxia-inducible factor-1α (HIF-1α) results in a significant decrease in the expression of caveolin-1 which is regulated by heat shock protein 90 (HSP90). The reduced levels of Cav-1 correlated with the increased epidermal growth factor receptor (EGFR) activation resulting in the significant activation of its downstream target STAT3. Accumulation of pSTAT3 in the nucleus results in the decreased expression of E-cadherin and increased expression of mesenchymal markers (Slug, α-SMA, N-cadherin and vimentin). Crosstalk of EGFR and transforming growth factor β (TGF-β) signalling with Wnt signalling enhances cell proliferation, cell survival and upregulates EMT. There was no significant alteration in the expression of epithelial and mesenchymal molecules in both the cell lines studied. Thus, we provide evidence that Cav-1 was modulated by HSP90 and functions as a crucial regulator of EMT in gastric cancer.

Requirement for integrin-linked kinase in neural crest migration and differentiation and outflow tract morphogenesis

BACKGROUND

Neural crest defects lead to congenital heart disease involving outflow tract malformation. Integrin-linked-kinase (ILK) plays important roles in multiple cellular processes and embryogenesis. ILK is expressed in the neural crest, but its role in neural crest and outflow tract morphogenesis remains unknown.

RESULTS

We ablated ILK specifically in the neural crest using the Wnt1-Cre transgene. ILK ablation resulted in abnormal migration and overpopulation of neural crest cells in the pharyngeal arches and outflow tract and a significant reduction in the expression of neural cell adhesion molecule (NCAM) and extracellular matrix components. ILK mutant embryos exhibited an enlarged common arterial trunk and ventricular septal defect. Reduced smooth muscle differentiation, but increased ossification and neurogenesis/innervation were observed in ILK mutant outflow tract that may partly be due to reduced transforming growth factor β2 (TGFβ2) but increased bone morphogenetic protein (BMP) signaling. Consistent with these observations, microarray analysis of fluorescence-activated cell sorting (FACS)-sorted neural crest cells revealed reduced expression of genes associated with muscle differentiation, but increased expression of genes of neurogenesis and osteogenesis.

CONCLUSIONS

Our results demonstrate that ILK plays essential roles in neural crest and outflow tract development by mediating complex crosstalk between cell matrix and multiple signaling pathways. Changes in these pathways may collectively result in the unique neural crest and outflow tract phenotypes observed in ILK mutants.

Inactivation of the integrin-linked kinase (ILK) in osteoblasts increases mineralization

In osteoblasts, Integrin-Linked Kinase (ILK)-dependent phosphorylation of the cJUN transcriptional coactivator, αNAC, induces the nuclear accumulation of the coactivator and potentiates cJUN-dependent transcription. Mutation of the ILK phosphoacceptor site within the αNAC protein leads to cytoplasmic retention of the coactivator and cell-autonomous increases in osteoblastic activity. In order to gain further insight into the ILK-αNAC signaling cascade, we inactivated ILK using RNA knockdown in osteoblastic cells and engineered mice with specific ablation of ILK in osteoblasts. ILK knockdown in MC3T3-E1 osteoblast-like cells reduced phosphorylation of its downstream target glycogen synthase kinase 3β (GSK3β), which led to cytoplasmic retention of αNAC and increased mineralization with augmented expression of the osteoblastic differentiation markers, pro-α1(I) collagen (col1A1), Bone Sialoprotein (Bsp) and Osteocalcin (Ocn). Cultured ILK-deficient primary osteoblasts also showed increased cytoplasmic αNAC levels, and augmented mineralization with higher Runx2, Col1a1 and Bsp expression. Histomorphometric analysis of bones from mutant mice with ILK-deficient osteoblasts (Col1-Cre;Ilk(-/fl)) revealed transient changes, with increased bone volume in newborn animals that was corrected by two weeks of age. Our data suggest that the ILK-αNAC cascade acts to reduce the pace of osteoblast maturation. We propose that in vivo, functional redundancy is able to compensate for the loss of ILK activity, leading to the absence of an obvious phenotype when osteoblast-specific Ilk-deficient mice reach puberty.

β1 integrin is a crucial regulator of pancreatic β-cell expansion

Development of the endocrine compartment of the pancreas, as represented by the islets of Langerhans, occurs through a series of highly regulated events encompassing branching of the pancreatic epithelium, delamination and differentiation of islet progenitors from ductal domains, followed by expansion and three-dimensional organization into islet clusters. Cellular interactions with the extracellular matrix (ECM) mediated by receptors of the integrin family are postulated to regulate key functions in these processes. Yet, specific events regulated by these receptors in the developing pancreas remain unknown. Here, we show that ablation of the β1 integrin gene in developing pancreatic β-cells reduces their ability to expand during embryonic life, during the first week of postnatal life, and thereafter. Mice lacking β1 integrin in insulin-producing cells exhibit a dramatic reduction of the number of β-cells to only ∼18% of wild-type levels. Despite the significant reduction in β-cell mass, these mutant mice are not diabetic. A thorough phenotypic analysis of β-cells lacking β1 integrin revealed a normal expression repertoire of β-cell markers, normal architectural organization within islet clusters, and a normal ultrastructure. Global gene expression analysis revealed that ablation of this ECM receptor in β-cells inhibits the expression of genes regulating cell cycle progression. Collectively, our results demonstrate that β1 integrin receptors function as crucial positive regulators of β-cell expansion.

Tissue transglutaminase regulates β-catenin signaling through a c-Src-dependent mechanism

Tissue transglutaminase (TG2) is a multifunctional enzyme involved in protein cross-linking and cell adhesion to fibronectin (FN). In cancer, TG2 induces an epithelial to mesenchymal transition, contributing to metastasis. Because cadherins bind β-catenin at cell-cell junctions, disruption of adherens junctions destabilizes cadherin-catenin complexes. The goal of the present study was to analyze whether and how TG2 interacts with and regulates β-catenin signaling in ovarian cancer (OC) cells. We observed a significant correlation between TG2 and β-catenin expression levels in OC cells and tumors. TG2 augmented Wnt/β-catenin signaling, as evidenced by enhanced β-catenin transcriptional activity, inducing transcription of target genes cyclin D1 and c-Myc. By promoting integrin-mediated cell adhesion to FN, TG2 physically associates with and recruits c-Src, which in turn phosphorylates β-catenin at Tyr(654), releasing it from E-cadherin and rendering it available for transcriptional regulation. By interacting with FN and enhancing β-catenin signaling, complexed TG2 stimulates OC cell proliferation. In summary, our data demonstrate that TG2 regulates β-catenin expression and function in OC cells and define the c-Src-dependent mechanism through which this occurs.

Deletion of integrin linked kinase in endothelial cells results in defective RTK signaling caused by caveolin 1 mislocalization

Integrin linked kinase (ILK) connects the ILK-Pinch-Parvin complex with integrin adhesion sites. Because of the functional relevance of integrin-linked signaling for endothelial cell (EC) biology, we have explored this pathway in Ilk(-/-) embryonic stem (ES) cells differentiated into ECs and vessel-like structures. We have focused in particular on the mechanistic relevance of ILK-Pinch-Parvin complex-related signaling for EC development and tube formation. Our analysis revealed that the formation of vessel-like structures was strongly reduced in Ilk(-/-) ES cells and that this phenotype could be rescued by re-expression of ILK in ES cells. ECs were MACS sorted from wild-type (WT) and Ilk(-/-) ES cells and functional analysis using intracellular calcium imaging as the read-out yielded a complete lack of vascular endothelial growth factor- and epidermal growth factor-dependent responses. The possibility of a caveolin 1-related defect was investigated by transfecting WT and Ilk(-/-) ECs with a caveolin 1-EGFP fusion protein. Time-lapse microscopy showed that the prominent phenotype is due to altered dynamics of caveolin 1 and to a lack of positioning of caveolin 1 in the vicinity of the plasma membrane and that it is rescued by re-expressing ILK in the Ilk(-/-) ES cells. We also found that the defect is caused by the perturbed organization of microtubules and cortical actin filaments. Thus, ILK is required as a scaffold to allow actin-microtubule interactions and correct positioning of caveolin 1 close to the plasma membrane. This is crucial for signaling compartmentalization in ECs and explains the key role of ILK for EC development and function.

Sheep, wolf, or werewolf: cancer stem cells and the epithelial-to-mesenchymal transition

Multiple cancers contain subpopulations that exhibit characteristics of cancer stem cells (CSCs), the ability to self-renew and seed heterogeneous tumors. Recent evidence suggests two potentially overlapping models for these phenotypes: one where stem cells arise from multipotent progenitor cells, and another where they are created via an epithelial to mesenchymal transition. Unraveling this issue is critical, as it underlies phenomena such as metastasis and therapeutic resistance. Therefore, there is intense interest in understanding these two types of CSSs, how they differ from differentiated cancer cells, the mechanisms that drive their phenotypes, and how that knowledge can be incorporated into therapeutics.

Integrin-linked kinase regulates interphase and mitotic microtubule dynamics

Integrin-linked kinase (ILK) localizes to both focal adhesions and centrosomes in distinct multiprotein complexes. Its dual function as a kinase and scaffolding protein has been well characterized at focal adhesions, where it regulates integrin-mediated cell adhesion, spreading, migration and signaling. At the centrosomes, ILK regulates mitotic spindle organization and centrosome clustering. Our previous study showed various spindle defects after ILK knockdown or inhibition that suggested alteration in microtubule dynamics. Since ILK expression is frequently elevated in many cancer types, we investigated the effects of ILK overexpression on microtubule dynamics. We show here that overexpressing ILK in HeLa cells was associated with a shorter duration of mitosis and decreased sensitivity to paclitaxel, a chemotherapeutic agent that suppresses microtubule dynamics. Measurement of interphase microtubule dynamics revealed that ILK overexpression favored microtubule depolymerization, suggesting that microtubule destabilization could be the mechanism behind the decreased sensitivity to paclitaxel, which is known to stabilize microtubules. Conversely, the use of a small molecule inhibitor selective against ILK, QLT-0267, resulted in suppressed microtubule dynamics, demonstrating a new mechanism of action for this compound. We further show that treatment of HeLa cells with QLT-0267 resulted in higher inter-centromere tension in aligned chromosomes during mitosis, slower microtubule regrowth after cold depolymerization and the presence of a more stable population of spindle microtubules. These results demonstrate that ILK regulates microtubule dynamics in both interphase and mitotic cells.