Integrin signaling in epithelial cells

Hyaluronidase Hyal1 Increases Tumor Cell Proliferation and Motility through Accelerated Vesicle Trafficking

Hyaluronan (HA) turnover accelerates metastatic progression of prostate cancer in part by increasing rates of tumor cell proliferation and motility. To determine the mechanism, we overexpressed hyaluronidase 1 (Hyal1) as a fluorescent fusion protein and examined its impact on endocytosis and vesicular trafficking. Overexpression of Hyal1 led to increased rates of internalization of HA and the endocytic recycling marker transferrin. Live imaging of Hyal1, sucrose gradient centrifugation, and specific colocalization of Rab GTPases defined the subcellular distribution of Hyal1 as early and late endosomes, lysosomes, and recycling vesicles. Manipulation of vesicular trafficking by chemical inhibitors or with constitutively active and dominant negative Rab expression constructs caused atypical localization of Hyal1. Using the catalytically inactive point mutant Hyal1-E131Q, we found that enzymatic activity of Hyal1 was necessary for normal localization within the cell as Hyal1-E131Q was mainly detected within the endoplasmic reticulum. Expression of a HA-binding point mutant, Hyal1-Y202F, revealed that secretion of Hyal1 and concurrent reuptake from the extracellular space are critical for rapid HA internalization and cell proliferation. Overall, excess Hyal1 secretion accelerates endocytic vesicle trafficking in a substrate-dependent manner, promoting aggressive tumor cell behavior.

Dynamic Sialylation in Transforming Growth Factor-β (TGF-β)-induced Epithelial to Mesenchymal Transition

Epithelial-mesenchymal transition (EMT) is a fundamental process in embryonic development and organ formation. Aberrant regulation of EMT often leads to tumor progression. Changes in cell surface sialylation have recently been implicated in mediating EMT. Herein we report the visualization of dynamic changes of sialylation and glycoproteomic analysis of newly synthesized sialylated proteins in EMT by metabolic labeling of sialylated glycans with azides, followed by click labeling with fluorophores or affinity tags. We discovered that sialylation was down-regulated during EMT but then reverted and up-regulated in the mesenchymal state after EMT, accompanied by mRNA expression level changes of genes involved in the sialic acid biosynthesis. Quantitative proteomic analysis identified a list of sialylated proteins whose biosynthesis was dynamically regulated during EMT. Sialylation of cell surface adherent receptor integrin β4 was found to be down-regulated, which may regulate integrin functions during EMT. Furthermore, a global sialylation inhibitor was used to probe the functional role of sialylation during EMT. We found that inhibition of sialylation promoted EMT. Taken together, our findings suggest the important role of sialylation in regulating EMT and imply its possible function in related pathophysiological events, such as cancer metastasis.

α6β1- and αV-integrins are required for long-term self-renewal of murine embryonic stem cells in the absence of LIF

Background

The growth properties and self-renewal capacity of embryonic stem (ES) cells are regulated by their immediate microenvironment such as the extracellular matrix (ECM). Integrins, a central family of cellular ECM receptors, have been implicated in these processes but their specific role in ES cell self-renewal remains unclear.

Results

Here we have studied the effects of different ECM substrates and integrins in mouse ES cells in the absence of Leukemia Inhibitory Factor (LIF) using short-term assays as well as long-term cultures. Removal of LIF from ES cell culture medium induced morphological differentiation of ES cells into polarized epistem cell-like cells. These cells maintained epithelial morphology and expression of key stemness markers for at least 10 passages in the absence of LIF when cultured on laminin, fibronectin or collagen IV substrates. The specific functional roles of α6-, αV- and β1-integrin subunits were dissected using stable lentivirus-mediated RNAi methodology. β1-integrins were required for ES cell survival in long-term cultures and for the maintenance of stem cell marker expression. Inhibition of α6-integrin expression compromised self-renewal on collagen while αV-integrins were required for robust ES cell adhesion on laminin. Analysis of the stemness marker expression revealed subtle differences between α6- and αV-depleted ES cells but the expression of both was required for optimal self-renewal in long-term ES cell cultures.

Conclusions

In the absence of LIF, long-term ES cell cultures adapt an epistem cell-like epithelial phenotype and retain the expression of multiple stem cell markers. Long-term maintenance of such self-renewing cultures depends on the expression of β1-, α6- and αV-integrins.

Electronic supplementary material

The online version of this article (doi:10.1186/s12860-015-0051-y) contains supplementary material, which is available to authorized users.

Inhibition of Integrin-HER2 signaling by Cucurbitacin B leads to in vitro and in vivo breast tumor growth suppression

HER2, an oncogenic receptor is overexpressed in about 25-30% of breast cancer patients. HER2 has been shown to play role in tumor promotion by having cross-talk with multiple oncogenic pathways in cancer cells. Our results show that Cucurbitacin B (CuB), a triterpenoid steroidal compound inhibited the growth of various breast cancer cells with an IC50 ranging from 18-50nM after 48 and 72 h of treatment. Our study also revealed the significant inhibitory effects of CuB on HER2 and integrin signaling in breast cancer. Notably, CuB inhibited ITGA6 and ITGB4 (integrin α6 & integrin β4), which are overexpressed in breast cancer. Furthermore, CuB also induced the expression of major ITGB1and ITGB3, which are known to cause integrin-mediated cell death. In addition, we observed that TGFβ treatment resulted in the increased association of HER2 with ITGA6 and this association was inhibited by CuB treatment. Efficacy of CuB was tested in vivo using two different orthotopic models of breast cancer. MDA-MB-231 and 4T-1 cells were injected orthotopically in the mammary fat pad of female athymic nude mice or BALB/c mice respectively. Our results showed that CuB administration inhibited MDA-MB-231 orthotopic tumors by 55%, and 4T-1 tumors by 40%. The 4T-1 cells represent stage IV breast cancer and form very aggressive tumors. CuB mediated breast tumor growth suppression was associated with the inhibition of HER2/integrin signaling. Our results suggest novel targets of CuB in breast cancer in vitro and in vivo.

The effect of ROCK on TNF-α-induced CXCL8 secretion by intestinal epithelial cell lines is mediated through MKK4 and JNK signaling

Intestinal epithelial cells (IEC) play a role in mucosal inflammatory responses by producing important chemokines like CXCL8 when stimulated by TNF-α. Previously, we found that IEC cell lines required the Rho-associated kinase, ROCK, for CXCL8 responses after IL-1 stimulation. This study extends these findings by showing that inhibiting ROCK suppressed TNF-α-induced CXCL8 secretion by Caco-2 and DLD1 colonic epithelial cell lines and CXCL8 mRNA levels in Caco-2 cells. RNAi knockdown experiments indicated that the inhibitory effect was mediated by ROCK2, and not ROCK1. Inhibiting ROCK had no effect on TNF-stimulated IκBα phosphorylation and degradation or p38 MAPK phosphorylation indicating that ROCK plays no role in these signaling pathways. However, inhibiting ROCK suppressed TNF-induced phosphorylation of the p54 JNK isoform and phosphorylation of the upstream MKK4 kinase. These results suggest that ROCK is required for CXCL8 responses by TNF-stimulated IEC by affecting intracellular signaling through MKK4 and JNK.

Osteopontin expression in the intestine of chukar partridge (Alectoris chukar, Gray, 1830)

The intestinal mucosa is under continuous attack of microorganisms and is defended by the joint action of epithelial cells and specialized immune cells. Osteopontin (OPN), a member of the Small Integrin-Binding Ligand, N-linked Glycoprotein (SIBLING) family, is an adhesive phosphorylated glyco-protein that is synthesized by a variety of nonimmune and immune cells that is involved in interactions with cells mediating signaling. OPN is especially required for the maintenance of the epithelial barrier. To gain a better understanding of the biology of OPN, in the avian intestinal tract, we examined subcellular localization of OPN in the small and large intestine using immunohistochemistry. Immunostaining for OPN was prominently and significantly detected in the epithelial cells of the small and large intestine. However, intestinal stromal cells of the small intestine and the smooth muscle cells in the wall of the large intestine did not exhibit OPN immunoreactivity. Our results show that the differences between the localizations of OPN in the chukar partridge’s small and large intestine may be associated with functional differences of intestine parts. Therefore, the expression of OPN in the chukar partridge intestine may play a crucial role in barrier function, host defence, and/or secretion.

β1 integrin mediates colorectal cancer cell proliferation and migration through regulation of the Hedgehog pathway

β1 integrin (ITGB1) is the major expressed integrin protein of normal cells and tumor-associated cells. It is often up-regulated in human malignancies and is involved in many developmental processes, such as tumor progression and metastasis. However, little is known about the function of ITGB1 in colorectal cancer. We constructed lentiviral vectors expressing ITGB1 or ITGB1-specific RNA interference (RNAi) and an unrelated control vector. After infecting HT29 cells in vitro, proliferation and migration were evaluated by Cell Counting Kit 8 (CCK-8) assays, transwell invasion assays, and Western blots. The influence of lentivirus infection on the tumor development capacity of HT29 cells in vivo was examined by xenografting the tumor cells. The expression of ITGB1 in the xenografted tumor cells was analyzed by immunohistochemistry. The up-regulation of ITGB1 significantly increased the proliferation in HT29 cells in vitro. Moreover, we found that the overexpression of ITGB1 up-regulated sonic hedgehog (Shh) while down-regulating Gli1 and SuFu in HT29-ITGB1 cells compared to controls. Moreover, the levels of c-myc and cyclin D1 proteins were up-regulated. Transwell assays showed that the number of migrating HT29-RNAi cells was lower than that in the other cell groups, indicating that ITGB1 significantly enhances the invasive ability of HT29 cells. In addition to these in vitro results, ITGB1 was found to be a significantly effective growth factor in a xenografted tumor mouse model. These results suggest that ITGB1 induces growth and invasion in a human colorectal cancer cell line through the hedgehog (Hh) signaling pathway in vitro and in vivo.

Expression analysis of integrin β1 isoforms during zebrafish embryonic development

Integrins are a superfamily of the major metazoan receptors for cell-cell and cell-extracellular matrix adhesion. Integrins and their ligands play critical roles in a variety of fundamental cellular processes. Integrins are heterodimeric cell surface glycoproteins comprised of non-covalently bound α- and β-subunits. A variety of integrin subunits have been identified in mouse, chicken, zebrafish, Xenopus laevis and other vertebrates. In zebrafish multiple integrin β1 homologs have been identified. However, zebrafish embryo is a largely untapped model for analyzing integrin β1 isoforms temporal-spatial expression pattern, function and its relevance to human disease in whole animal level. Currently, we systematically analyzed the expression pattern of zebrafish integrin β1 including integrin beta 1a (itgb1a), integrin beta 1b (itgb1b), integrin beta 1b.1 (itgb1b.1), and integrin beta 1b.2 (itgb1b.2) at embryo stage using whole amount in situ hybridization. We show itgb1a, itgb1b and itgb1b.1 were maternally expressed in zygote, cleavage and blastula periods, while itgb1b.2 was not detectable in the corresponding stages. A more tissue specific pattern emerges during organogenesis, including heart expression for itgb1a, myotome borders for itgb1b, intestinal epithelium for itgb1b.1, and branchial arch for itgb1b.2. All are similarly expressed in the early embryonic epidermis and notochord. Additionally, itgb1a, itgb1b and itgb1b.2 shared the common expression in otic vesicle. Our study provides new insight into the integrin β1 expression and the use of this model organism to tackle future studies on the role of integrin β1 in embryo development.

Switch from αvβ5 to αvβ6 integrin is required for CD9-regulated keratinocyte migration and MMP-9 activation

Our previous research found that tetraspanin CD9 is downregulated in migrating epidermis during wound healing, and CD9 downregulation contributes to keratinocyte migration via matrix metalloproteinase-9 (MMP-9) activation. However, little is known about the mechanisms involved in CD9-regulated keratinocyte migration and MMP-9 activation. In this study, we revealed that the expressions of integrin subunits β5 and β6 were regulated by CD9. Furthermore, CD9 silencing triggered the switch from αvβ5 to αvβ6 integrin in HaCaT keratinocytes and CD9 overexpression reversed the switch. Importantly, integrin αvβ6 functional blocking antibody 10D5 significantly inhibited CD9 silencing-induced keratinocyte migration and MMP-9 activation, suggesting that the switch from αvβ5 to αvβ6 integrin plays a key role in CD9-regulated cell migration and MMP-9 activation in keratinocytes.

Phosphoinositide 3-kinase p85beta regulates invadopodium formation

The acquisition of invasiveness is characteristic of tumor progression. Numerous genetic changes are associated with metastasis, but the mechanism by which a cell becomes invasive remains unclear. Expression of p85β, a regulatory subunit of phosphoinositide-3-kinase, markedly increases in advanced carcinoma, but its mode of action is unknown. We postulated that p85β might facilitate cell invasion. We show that p85β localized at cell adhesions in complex with focal adhesion kinase and enhanced stability and maturation of cell adhesions. In addition, p85β induced development at cell adhesions of an F-actin core that extended several microns into the cell z-axis resembling the skeleton of invadopodia. p85β lead to F-actin polymerization at cell adhesions by recruiting active Cdc42/Rac at these structures. In accordance with p85β function in invadopodium-like formation, p85β levels increased in metastatic melanoma and p85β depletion reduced invadopodium formation and invasion. These results show that p85β enhances invasion by inducing cell adhesion development into invadopodia-like structures explaining the metastatic potential of tumors with increased p85β levels.

The mechanism for keratinocyte detaching from pH-responsive chitosan

In this study, we compared the detachment ratio of HaCaT and Hs68 cells from pH-responsive chitosan surface by raising medium pH from 7.20 to 7.65 for 60 min. The detachment ratio of elongated Hs68 cells was over 75%, but that of round-shaped HaCaT cells was less than 50%, even extending the incubation time to 6 h or enhancing the cytoskeletal contractile force with the Rho activator CN01. However, the addition of 2 mm of EDTA into the medium at pH 7.65 could effectively detach HaCaT cells (detachment ratio > 90%), indicating that the calcium ion played an important role in the detachment process. Therefore, the family of Ca(+2)-dependent integrin receptors was examined by RT-PCR, real-time PCR and immunocytochemistry. It was found the expression of integrin β4 (ITGb4) was HaCaT cell-specific and the mRNA level of ITGb4 in undetached HaCaT cells was significantly higher than that in detached ones. By modulating ITGb4 activity with specific functional blocking antibody ASC-8, the detachment ratio of HaCaT cells could be increased to be greater than 85%. Conversely, the addition of the ligand of ITGb4 laminin into the culture system decreased the medium pH-induced detachment ratio for HaCaT cells, but not for Hs68 cells. Further addition of ASC-8 could rescue the effect of laminin on preventing the detachment of HaCaT cells from pH-sensitive chitosan surface. Therefore, this study demonstrated the interaction of ITGb4 and laminin played an important role in controlling the detachment of HaCaT cells on pH-responsive chitosan.

Signaling pathways in anchoring junctions of epithelial cells: cell-to-cell and cell-to-extracellular matrix interactions

Epithelial cells form the epithelium, one of the basic tissues of the human body. These cells present specializations from tissue to tissue, determining different structures and functions. Tissues formed by epithelial cells are characterized by the few extracellular matrix found between adjacent cells. In this way, to preserve tissue integrity, cells have to stick to each other and have to maintain a strict communication with the environment via cell junctions. Signal transduction is the main way of cell communication, being vital for the regulation of cell survival and proliferation. In cell junctions, this communication occurs through cell adhesion molecules that promote cell-to-cell and cell-to-extracellular matrix adhesion, as well as, enable the flow of information to the inside and to the outside of the cell. These molecules include integrins and cadherins, among others. The impairment of cell signaling in epithelial junctions has been involved in several pathological processes that underlie the development of, for example, colorectal cancer. Thus, epithelial cell signaling mediators have been explored as potential therapeutic targets and efforts have been made to achieve a deeper understanding of molecular events that occur at cell junctions. In this review, we address the current knowledge on the main signaling events that take place in anchoring junctions of epithelial cells, focusing both on cell-to-cell and cell-to-matrix interactions. To conclude, we explore some relevant consequences from epithelial cell signaling impairment and demonstrate that the molecular mediators of the pathways analyzed may be putative therapeutic targets.

β1 integrin modulates tumor growth and apoptosis of human colorectal cancer

We aimed to ascertain whether β1 integrin (ITGB1) induces apoptosis of colorectal cancer (CRC) through regulation of the mitochondrial pathway in vitro and in vivo. We generated lentiviral vectors expressing ITGB1 or ITGB1-specific RNAi and an unrelated control vector. After infection of the HT29 cells, we used western blot analysis and flow cytometric analysis to validate the patterns of ITGB1 expression. Proliferation and apoptosis were evaluated by colony formation assay, flow cytometry and western blot analysis. Upregulation of ITGB1 significantly increased the proliferation of HT29 cells; however, the levels of Bcl-2 and cyclin D1 proteins were upregulated while Bax, caspase-3, caspase-9 and p21 were downregulated in the HT29-ITGB1 cells compared to these levels in the controls. Hoechst 33258 staining and flow cytometric analysis showed that ITGB1 may play a significant role in the apoptosis of CRC cells. Moreover, ITGB1 promoted the proliferation of cells in a xenograft tumor mouse model. TUNEL staining revealed a marked increase in the percentage of positive cells in the HT29-RNAi group (84.3 ± 4.0%), which were more significant than in the HT29-ITGB1 group (48.3 ± 2.9%) and the other two control groups, HT29 (52.0 ± 3.6%) and HT29-NC (49.7 ± 4.5%). These results suggest that ITGB1 regulates the growth and apoptosis of human colorectal cancer cells.

Integrin modulators: a patent review

INTRODUCTION

Integrins are heterodimeric cell surface receptors, which enable adhesion, proliferation, and migration of cells by recognizing binding motifs in extracellular matrix (ECM) proteins. As transmembrane linkers between the cytoskeleton and the ECM, they are able to recruit a huge variety of proteins and to influence signaling pathways bidirectionally, thereby regulating gene expression and cell survival. Hence, integrins play a key role in various physiological as well as pathological processes, which has turned them into an attractive target for pharmaceutical research.

AREAS COVERED

In this review, the latest therapeutic developments of drug candidates and recently patented integrin ligands are summarized.

EXPERT OPINION

Integrins have been proven to be valuable therapeutic targets in the treatment of several inflammatory and autoimmune diseases, where leukocyte adhesion processes are regulated by them. Furthermore, they play an important role in pathological angiogenesis and tumor metastasis, being a promising target for cancer therapy.

Equid herpesvirus type 4 uses a restricted set of equine major histocompatibility complex class I proteins as entry receptors

Equid herpesvirus type 1 (EHV-1) was shown to use an unusual receptor for cellular entry - MHC-I molecules. Here, we demonstrated that the closely related EHV, EHV-4, also uses this strategy for cellular invasion, both in equine cells in culture and in the heterologous, non-permissive murine mastocytoma cell line (P815) after stable transfection with horse MHC-I genes. Using a panel of P815 cell lines transfected with individual horse MHC-I genes, we provided support for the hypothesis that EHV-1 and EHV-4 target classical polymorphic MHC-I molecules as viral entry receptors. All known equine MHC-I molecules from the two principal classical polymorphic loci specify alanine at position 173 (A173), whilst other MHC-I loci encoded different amino acids at this position and did not permit viral entry. Site-directed mutagenesis of position 173 diminished or enhanced viral entry, depending upon the initial amino acid. However, there were other, as yet undefined, constraints to this process: MHC-I genes from two non-classical loci carried A173 but did not enable viral entry in P815 transfectants. Our study suggested that the capacity to bind MHC-I molecules arose in the common ancestor of EHV-1 and EHV-4. The widespread occurrence of A173 in classical polymorphic horse MHC-I molecules indicated that horses of most MHC haplotypes should be susceptible to infection via this entry portal.

Pectin of Prunus domestica L. alters sulfated structure of cell-surface heparan sulfate in differentiated Caco-2 cells through stimulation of heparan sulfate 6-O-endosulfatase-2

Although previous reports have suggested that pectin induces morphological changes of the small intestine in vivo, the molecular mechanisms have not been elucidated. As heparan sulfate plays important roles in development of the small intestine, to verify the involvement of heparan sulfate (HS) in the pectin-induced morphological changes of the small intestine, the effects of pectin from Prunus domestica L. on cell-surface HS were investigated using differentiated Caco-2 cells. Disaccharide compositional analysis revealed that sulfated structures of HS were markedly changed by pectin administration. Real-time RT-PCR showed that pectin upregulated human HS 6-O-endosulfatase-2 (HSulf-2) expression and markedly inhibited HSulf-1 expression. Furthermore, inhibition analysis suggested that pretreatment with fibronectin III1C fragment, RGD peptide, and ERK1/2 inhibitor suppressed pectin-induced HSulf-2 expression. These observations indicate that pectin induced the expression of HSulf-2 through the interaction with fibronectin, α5β1 integrin, and ERK1/2, thereby regulating the sulfated structure of HS on differentiated Caco-2 cells.

Integrin Regulation of Epidermal Functions in Wounds

Significance: Integrins are bidirectional signaling receptors for extracellular matrix that regulate both inside-out signaling that controls keratinocyte-mediated changes to the wound microenvironment and outside-in signaling that controls keratinocyte responses to microenvironmental changes. As such, integrins represent attractive therapeutic targets for treatment of chronic wounds or general promotion of wound healing. Advances in wound management are particularly important as the elderly and diabetic populations within the United States continue to grow. Recent Advances: Although integrins are best known for mediating cell adhesion and migration, integrins in wound epidermis also control cell survival, proliferation, matrix remodeling, and paracrine crosstalk to other cellular compartments of the wound. Importantly, the concept of targeting integrins in the clinic has been established for treatment of certain cancers and other diseases, laying the groundwork for similar exploitation of integrins as targets to treat chronic wounds. Critical Issues: Despite their attractiveness as therapeutic targets, integrins have complex roles in wound healing that are impacted by both their own expression and a highly dynamic wound microenvironment that determines ligand availability. Therefore, identifying relevant integrin ligands in the wound and understanding both distinct and overlapping functions that different integrins play in the epidermis will be critical to determine their precise roles in wound healing. Future Directions: Future research should focus on gaining a thorough understanding of the highly coordinated functions of different integrins in wound epidermis, and on determining which of these functions go awry in pathological wounds. This focus should facilitate development of integrin-targeting therapeutics for treating chronic wounds.

β1 integrin signaling maintains human epithelial progenitor cell survival in situ and controls proliferation, apoptosis and migration of their progeny

β1 integrin regulates multiple epithelial cell functions by connecting cells with the extracellular matrix (ECM). While β1 integrin-mediated signaling in murine epithelial stem cells is well-studied, its role in human adult epithelial progenitor cells (ePCs) in situ remains to be defined. Using microdissected, organ-cultured human scalp hair follicles (HFs) as a clinically relevant model for studying human ePCs within their natural topobiological habitat, β1 integrin-mediated signaling in ePC biology was explored by β1 integrin siRNA silencing, specific β1 integrin-binding antibodies and pharmacological inhibition of integrin-linked kinase (ILK), a key component of the integrin-induced signaling cascade. β1 integrin knock down reduced keratin 15 (K15) expression as well as the proliferation of outer root sheath keratinocytes (ORSKs). Embedding of HF epithelium into an ECM rich in β1 integrin ligands that mimic the HF mesenchyme significantly enhanced proliferation and migration of ORSKs, while K15 and CD200 gene and protein expression were inhibited. Employing ECM-embedded β1 integrin-activating or -inhibiting antibodies allowed to identify functionally distinct human ePC subpopulations in different compartments of the HF epithelium. The β1 integrin-inhibitory antibody reduced β1 integrin expression in situ and selectively enhanced proliferation of bulge ePCs, while the β1 integrin-stimulating antibody decreased hair matrix keratinocyte apoptosis and enhanced transferrin receptor (CD71) immunoreactivity, a marker of transit amplifying cells, but did not affect bulge ePC proliferation. That the putative ILK inhibitor QLT0267 significantly reduced ORSK migration and proliferation and induced massive ORSK apoptosis suggests a key role for ILK in mediating the ß1 integrin effects. Taken together, these findings demonstrate that ePCs in human HFs require β1 integrin-mediated signaling for survival, adhesion, and migration, and that different human HF ePC subpopulations differ in their response to β1 integrin signaling. These insights may be exploited for cell-based regenerative medicine strategies that employ human HF-derived ePCs.

Suppression of anoikis in human intestinal epithelial cells: differentiation state-selective roles of α2β1, α3β1, α5β1, and α6β4 integrins

Background

Regulation of anoikis in human intestinal epithelial cells (IECs) implicates differentiation state-specific mechanisms. Human IECs express distinct repertoires of integrins according to their state of differentiation. Therefore, we investigated whether α2β1, α3β1, α5β1, and α6β4 integrins perform differentiation state-specific roles in the suppression of IEC anoikis.

Results

Human (HIEC, Caco-2/15) IECs were exposed to specific antibodies that block the binding activity of integrin subunits (α2, α3, α5, α6, β1 or β4) to verify whether or not their inhibition induced anoikis. The knockdown of α6 was also performed by shRNA. Additionally, apoptosis/anoikis was induced by pharmacological inhibition of Fak (PF573228) or Src (PP2). Anoikis/apoptosis was assayed by DNA laddering, ISEL, and/or caspase activity (CASP-8, -9, or -3). Activation levels of Fak and Src, as well as functional Fak-Src interactions, were also assessed. We report herein that differentiated IECs exhibit a greater sensitivity to anoikis than undifferentiated ones. This involves an earlier onset of anoikis when kept in suspension, as well as significantly greater contributions from β1 and β4 integrins in the suppression of anoikis in differentiated cells, and functional distinctions between β1 and β4 integrins in engaging both Fak and Src, or Src only, respectively. Likewise, Fak performs significantly greater contributions in the suppression of anoikis in differentiated cells. Additionally, we show that α2β1 and α5β1 suppress anoikis in undifferentiated cells, whereas α3β1 does so in differentiated ones. Furthermore, we provide evidence that α6β4 contributes to the suppression of anoikis in a primarily α6 subunit-dependent manner in undifferentiated cells, whereas this same integrin in differentiated cells performs significantly greater contributions in anoikis suppression than its undifferentiated state-counterpart, in addition to doing so through a dependence on both of its subunits.

Conclusions

Our findings indicate that the suppression of human IEC anoikis implicates differentiation state-selective repertoires of integrins, which in turn results into distinctions in anoikis regulation, and sensitivity, between undifferentiated and differentiated IECs. These data further the functional understanding of the concept that the suppression of anoikis is subjected to cell differentiation state-selective mechanisms.

β4-integrin-mediated cytotoxic activity of AexU in human prostate cancer PC3 cells

The present study aimed to characterize the cytotoxic activity of AexU, an effector-mediating type three secretion system (TTSS) of gram-negative bacteria, in human prostate cancer cells, focusing on the association with β4-integrin expression. The cytotoxic effects of AexU either alone or in combination with chemotherapeutic agents were evaluated using several human prostate cancer cell lines. Human prostate cancer PC3 cells, in which an expression vector containing siRNA targeting β4-integrin had been introduced, were established (PC3/sh-In), and the cytotoxic effects of AexU on the PC3/sh-In cells were compared with the PC3 cells that were transfected with a control vector (PC3/C). The expression levels of β4-integrin in the PC3 cells were markedly higher compared with those in the LNCaP or DU145 cells, and the cytotoxic effects of AexU in the PC3 cells were more pronounced compared with those in the LNCaP or DU145 cells. The sensitivity of the PC3 cells to docetaxel and cisplatin was significantly enhanced following treatment with AexU, resulting in a decrease in the IC₅₀ of the two agents by ~90%. The cytotoxic effect of AexU in the PC3/C cells was more marked compared with that in the PC3/sh-In cells, and the phosphorylation of Akt in the PC3/C cells appeared to be significantly more inhibited by the treatment with AexU compared with the PC3/sh-In cells. In conclusion, treatment with AexU may be a useful therapeutic option for prostate cancer when β4-integrin is overexpressed. The treatment appears to exert its effects through growth inhibition and by enhancing the sensitivity of the cancer cells to chemotherapeutic agents.

Tumour-suppressive microRNA-29s inhibit cancer cell migration and invasion by targeting laminin-integrin signalling in head and neck squamous cell carcinoma

Background:

Our recent studies of microRNA (miRNA) expression signatures demonstrated that microRNA-29s (miR-29s; miR-29a/b/c) were significantly downregulated in head and neck squamous cell carcinoma (HNSCC) and were putative tumour-suppressive miRNAs in human cancers. Our aim in this study was to investigate the functional significance of miR-29s in cancer cells and to identify novel miR-29s-mediated cancer pathways and responsible genes in HNSCC oncogenesis and metastasis.

Methods:

Gain-of-function studies using mature miR-29s were performed to investigate cell proliferation, migration and invasion in two HNSCC cell lines (SAS and FaDu). To identify miR-29s-mediated molecular pathways and targets, we utilised gene expression analysis and in silico database analysis. Loss-of-function assays were performed to investigate the functional significance of miR-29s target genes.

Results:

Restoration of miR-29s in SAS and FaDu cell lines revealed significant inhibition of cancer cell migration and invasion. Gene expression data and in silico analysis demonstrated that miR-29s modulated the focal adhesion pathway. Moreover, laminin γ2 (LAMC2) and α6 integrin (ITGA6) genes were candidate targets of the regulation of miR-29s. Luciferase reporter assays showed that miR-29s directly regulated LAMC2 and ITGA6. Silencing of LAMC2 and ITGA6 genes significantly inhibited cell migration and invasion in cancer cells.

Conclusion:

Downregulation of miR-29s was a frequent event in HNSCC. The miR-29s acted as tumour suppressors and directly targeted laminin–integrin signalling. Recognition of tumour-suppressive miRNA-mediated cancer pathways provides new insights into the potential mechanisms of HNSCC oncogenesis and metastasis and suggests novel therapeutic strategies for the disease.

A high level of integrin α6 expression in human intrahepatic cholangiocarcinoma cells is associated with a migratory and invasive phenotype

BACKGROUND

The integrin α6 subunit is part of the integrin α6β1 and α6β4 complexes, which are known to mediate the invasion of carcinoma cells. However, the precise role of integrin α6 in intrahepatic cholangiocarcinoma (ICC) has not yet been addressed.

METHODS

Twenty cases of ICCs and matched nontumor samples were used to analyze integrin α6 expression by immunohistochemistry. After the expression of integrin α6 was determined by RT-PCR and Western blot in ICC cells, we regulated the expression of integrin α6 in ICC cells with specific vshRNA-integrin α6, and assessed the role of integrin α6 in the proliferation and metastasis/invasion of ICC cells. Finally, the involved mechanisms and clinical significance were further investigated.

RESULTS

The expression of integrin α6 in ICC tissues was much higher than that in nontumor samples, and the high level of integrin α6 was detected in ICC cells compared with normal liver cells and HepG2 cells. After the down-regulation of integrin α6 in HCCC-9810 cells, we showed that the ability of ICC cells to metastasize and invade was much decreased in vitro, and cell proliferation was inhibited significantly. Further study indicated high expression of integrin α6 enhanced the activation of ERK1/2 and AKT signals in ICC cells and the inhibition of ERK1/2 down-regulated ICC cell proliferation, while the inhibition of AKT markedly impaired ICC cell metastasis and invasion. Integrin α6 overexpression was significantly correlated with larger tumors, multiple nodular, microvascular/bile duct invasion, and lymphatic metastasis (p < 0.05). The postoperative 5-year overall survival (OS) rate in patients with integrin α6(low) was higher than that of the integrin α6(high) group.

CONCLUSIONS

Overexpression of integrin α6 is associated with a migratory and invasive phenotype of ICC, and integrin α6 may be used as molecular target for therapy of ICC.

Survivin promotion of melanoma metastasis requires upregulation of α5 integrin

Survivin is an apoptotic and mitotic regulator that is overexpressed in melanoma and a poor prognostic marker in patients with metastatic disease. We recently showed that Survivin enhances melanoma cell motility through Akt-dependent upregulation of α5 integrin. However, the functional role of Survivin in melanoma metastasis is not clearly understood. We found that overexpression of Survivin in LOX and YUSAC2 human melanoma cells increased colony formation in soft agar, and this effect was abrogated by knockdown of α5 integrin by RNA interference. We employed melanoma cell xenografts to determine the in vivo effect of Survivin overexpression on melanoma metastasis. Although Survivin overexpression did not affect primary tumor growth of YUSAC2 or LOX subcutaneous tumors, or indices of proliferation or apoptosis, it significantly increased expression of α5 integrin in the primary tumors and formation of metastatic colonies in the lungs. Additionally, Survivin overexpression resulted in enhanced lung colony formation following intravenous (i.v.) injection of tumor cells in vivo and increased adherence to fibronectin-coated plastic in vitro. Importantly, in vivo inhibition of α5 integrin via intraperitoneal injection of an α5β1 integrin-blocking antibody significantly slowed tumor growth and reduced Survivin-enhanced pulmonary metastasis. Knockdown of α5 integrin in cells prior to i.v. injection also blocked Survivin-enhanced lung colony formation. These findings support a direct role for Survivin in melanoma metastasis, which requires α5 integrin and suggest that inhibitors of α5 integrin may be useful in combating this process.

Proteogenomic analysis of human colon carcinoma cell lines LIM1215, LIM1899, and LIM2405

As part of the genome-wide and chromosome-centric human proteomic project (C-HPP), we have integrated shotgun proteomics approach and a genome-wide transcriptomic approach (RNA-Seq) of a set of human colon cancer cell lines (LIM1215, LIM1899 and LIM2405) that were selected to represent a wide range of pathological states of colorectal cancer. The combination of a standard proteomics approach (1D-gel electrophoresis coupled to LC/ion trap mass spectrometry) and RNA-Seq allowed us to exploit the greater depth of the transcriptomics measurement (∼ 9800 transcripts per cell line) versus the protein observations (∼ 1900 protein identifications per cell line). Conversely, the proteomics data were helpful in identifying both cancer associated proteins with differential expression patterns as well as protein networks and pathways which appear to be deregulated in these cell lines. Examples of potential markers include mortalin, nucleophosmin, ezrin, LASP1, alpha and beta forms of spectrin, exportin, the carcinoembryonic antigen family, EGFR and MET. Interaction analyses identified the large intermediate filament family, the protein folding network and adapter proteins in focal adhesion networks, which included the CDC42 and RHOA signaling pathways that may have potential for identifying phenotypic states representing poorly and moderately differentiated states of CRC, with or without metastases.

Formaldehyde and epigenetic alterations: microRNA changes in the nasal epithelium of nonhuman primates

BACKGROUND

Formaldehyde is an air pollutant present in both indoor and outdoor atmospheres. Because of its ubiquitous nature, it is imperative to understand the mechanisms underlying formaldehyde-induced toxicity and carcinogenicity. MicroRNAs (miRNAs) can influence disease caused by environmental exposures, yet miRNAs are understudied in relation to formaldehyde. Our previous investigation demonstrated that formaldehyde exposure in human lung cells caused disruptions in miRNA expression profiles in vitro.

OBJECTIVES

Using an in vivo model, we set out to test the hypothesis that formaldehyde inhalation exposure significantly alters miRNA expression profiles within the nasal epithelium of nonhuman primates.

METHODS

Cynomolgus macaques were exposed by inhalation to approximately 0, 2, or 6 ppm formaldehyde for 6 hr/day for 2 consecutive days. Small RNAs were extracted from nasal samples and assessed for genome-wide miRNA expression levels. Transcriptional targets of formaldehyde-altered miRNAs were computationally predicted, analyzed at the systems level, and assessed using real-time reverse transcriptase polymerase chain reaction (RT-PCR).

RESULTS

Expression analysis revealed that 3 and 13 miRNAs were dysregulated in response to 2 and 6 ppm formaldehyde, respectively. Transcriptional targets of the miRNA with the greatest increase (miR-125b) and decrease (miR-142-3p) in expression were predicted and analyzed at the systems level. Enrichment was identified for miR-125b targeting genes involved in apoptosis signaling. The apoptosis-related targets were functionally tested using RT-PCR, where all targets showed decreased expression in formaldehyde-exposed samples.

CONCLUSIONS

Formaldehyde exposure significantly disrupts miRNA expression profiles within the nasal epithelium, and these alterations likely influence apoptosis signaling.

HB-EGF promotes intestinal restitution by affecting integrin-extracellular matrix interactions and intercellular adhesions

Restitution is a critical form of intestinal epithelial cell (IEC) healing. We have previously shown that heparin-binding epidermal-like growth factor (HB-EGF) is necessary for IEC restitution; however, the mechanisms by which HB-EGF promotes restitution remain poorly understood. This study was designed to investigate whether HB-EGF promotes intestinal restitution by affecting integrin-extracellular matrix (ECM) interactions and intercellular adhesions. The effect of HB-EGF administration was examined in a murine necrotizing enterocolitis (NEC) model in vivo and an IEC line scrape-wound healing model in vitro. We evaluated the effect of HB-EGF on the expression of integrins, E-cadherin/β-catenin, and integrin α5β1-dependent cell-ECM interactions. We found that HB-EGF promoted intestinal restitution and the expression of integrin α5β1. HB-EGF promoted integrin α5β1-dependent cell adhesion and spreading. In addition, HB-EGF decreased the expression E-cadherin/β-catenin, via the activation of v-erb-b2 erythroblastic leukemia viral oncogene homolog (ErbB-1). We conclude that HB-EGF promotes intestinal restitution by affecting integrin-ECM interactions and intercellular adhesions.

A novel role for the Rho-associated kinase, ROCK, in IL-1-stimulated intestinal epithelial cell responses

Intestinal epithelial cells (IEC) play a role in mucosal inflammation by producing pro-inflammatory chemokines that may initiate or amplify local responses. IL-1 is a potent activator of IEC and its receptor localizes to focal adhesions. Since the Rho-associated kinase, ROCK, also localizes to focal adhesions, we examined the role of ROCK in IL-1-induced chemokine responses in IEC cell lines. Suppressing ROCK with the Y27632 inhibitor suppressed IL-1-stimulated Caco-2 cell CXCL8/IL-8 and IEC-6 cell CCL2/MCP-1 secretion and mRNA levels. ROCK inhibition also suppressed IL-1-induced JNK phosphorylation in both cell lines, but high levels of the inhibitor had no significant effect on IL-1-stimulated Caco-2 IκBα phosphorylation and degradation or IKK phosphorylation and kinase activity. Therefore, ROCK may exert an effect on IL-1-stimulated JNK signaling to AP-1 activation, with little effect on IKK/IκBα signaling, defining a potentially important mechanism for regulating IL-1 signaling in IEC that may be essential for optimal cytokine responses.

SLK-mediated phosphorylation of paxillin is required for focal adhesion turnover and cell migration

Focal adhesion turnover is a complex process required for cell migration. We have previously shown that the Ste20-like kinase (SLK) is required for cell migration and efficient focal adhesion (FA) turnover in a FA kinase (FAK)-dependent manner. However, the role of SLK in this process remains unclear. Using a candidate substrate approach, we show that SLK phosphorylates the adhesion adapter protein paxillin on serine 250. Serine 250 phosphorylation is required for paxillin redistribution and cell motility. Mutation of paxillin serine 250 prevents its phosphorylation by SLK in vitro and results in impaired migration in vivo as evidenced by an accumulation of phospho-FAK-Tyr397 and altered FA turnover rates. Together, our data suggest that SLK phosphorylation of paxillin on serine 250 is required for FAK-dependent FA dynamics.

Tumor suppressive microRNA-218 inhibits cancer cell migration and invasion through targeting laminin-332 in head and neck squamous cell carcinoma

Recent our microRNA (miRNA) expression signature revealed that expression of microRNA-218 (miR-218) was reduced in cancer tissues, suggesting a candidate of tumor suppressor in head and neck squamous cell carcinoma (HNSCC). The aim of this study was to investigate the functional significance of miR-218 and its mediated moleculer pathways in HNSCC. Restoration of miR-218 in cancer cells led to significant inhibition of cell migration and invasion activities in HNSCC cell lines (FaDu and SAS). Genome-wide gene expression analysis of miR-218 transfectants and in silico database analysis showed that focal adhesion pathway was a promising candidate of miR-218 target pathways. The laminins are an important and biologically active part of the basal lamina, the function of that are various such as influencing cell differentiation, migration and adhesion as well as proliferation and cell survival. Interestingly, all components of laminin-332 (LAMA3, LAMB3 and LAMC2) are listed on the candidate genes in focal adhesion pathway. Furthermore, we focused on LAMB3 which has a miR-218 target site and gene expression studies and luciferase reporter assays showed that LAMB3 was directly regulated by miR-218. Silencing study of LAMB3 demonstrated significant inhibition of cell migration and invasion. In clinical specimens with HNSCC, the expression levels of laminin-332 were significantly upregulated in cancer tissues compared to adjacent non-cancerous tissues. Our analysis data showed that tumor suppressive miR-218 contributes to cancer cell migration and invasion through regulating focal adhesion pathway, especially laminin-332. Tumor suppressive miRNA-mediated novel cancer pathways provide new insights into the potential mechanisms of HNSCC oncogenesis.

Integrin α5β1 simultaneously controls EGFR-dependent proliferation and Akt-dependent pro-survival signaling in epidermoid carcinoma cells

To delineate distinctive role of the components of α5β1 integrin-EGFR axis in control of epidermoid carcinoma cell proliferation, we performed individual inhibition of α5β1 and EGFR via genetic and phamacological methods, respectively. We demonstrated that pharmacological inhibition of epidermal growth factor receptor (EGFR) significantly affected proliferation of A431 human cells by inducing the G0/G1 cell cycle arrest, whereas shRNA-mediated depletion of α5 subunit of α5β1 integrin led to a similar type of cell cycle arrest followed by significant apoptosis. Both treatments resulted in suppression of activated (phosphorylated) forms of focal adhesion kinase (FAK) and Erk. However, unlike EGFR inhibition, depletion of α5 led to substantial suppression of AKT activity. Accordingly, pharmacological inhibition of EGFR and AKT recapitulated detrimental effects caused by shRNA-mediated depletion of α5. Moreover, depletion of α5 led to a severe drop in the amounts of active EGFR. Thus, for the first time, we demonstrated that α5β1 integrin simultaneously maintains pro-survival signaling via continuous activation of AKT and up-regulates proliferation via activation of EGFR.

Saccharomyces boulardii improves intestinal epithelial cell restitution by inhibiting αvβ5 integrin activation state

Intestinal epithelial cell damage is frequently seen in the mucosal lesions of infectious or inflammatory bowel diseases such as ulcerative colitis or Crohn's disease. Complete remission of these diseases requires both the disappearance of inflammation and the repair of damaged epithelium. Saccharomyces boulardii (Sb, Biocodex) is a non-pathogenic yeast widely used as a preventive and therapeutic probiotic for the prevention and treatment of diarrhea and other gastrointestinal disorders. We recently showed that it enhances the repair of intestinal epithelium through activation of α2β1 integrin collagen receptors. In the present study, we demonstrated that α2β1 integrin is not the sole cell-extracellular matrix receptor involved during Sb-mediated intestinal restitution. Indeed, by using cell adhesion assays, we showed that Sb supernatant contains heat sensitive molecule(s), with a molecular weight higher than 9 kDa, which decreased αvβ5 integrin-mediated adhesion to vitronectin by competing with the integrin. Moreover, Sb-mediated changes in cell adhesion to vitronectin resulted in a reduction of the αvβ5signaling pathway. We used a monolayer wounding assay that mimics in vivo cell restitution to demonstrate that down-modulation of the αvβ5 integrin-vitronectin interaction is related to Sb-induced cell migration. We therefore postulated that Sb supernatant contains motogenic factors that enhance cell restitution through multiple pathways, including the dynamic fine regulation of αvβ5 integrin binding activity. This could be of major importance in diseases characterized by severe mucosal injury, such as inflammatory and infectious bowel diseases.

Beta 1 integrin predicts survival in breast cancer: a clinicopathological and immunohistochemical study

Background

The main focus of several studies concerned with cancer progression and metastasis is to analyze the mechanisms that allow cancer cells to interact and quickly adapt with their environment. Integrins, a family of transmembrane glycoproteins, play a major role in invasive and metastatic processes. Integrins are involved in cell adhesion in both cell-extracellular matrix and cell-cell interactions, and particularly, β1 integrin is involved in proliferation and differentiation of cells in the development of epithelial tissues. This work aimed to investigate the putative role of β1 integrin expression on survival and metastasis in patients with breast invasive ductal carcinoma (IDC). In addition, we compared the expression of β1 integrin in patients with ductal carcinoma in situ (DCIS).

Methods

Through tissue microarray (TMA) slides containing 225 samples of IDC and 67 samples of DCIS, β1 integrin expression was related with several immunohistochemical markers and clinicopathologic features of prognostic significance.

Results

β1 integrin was overexpressed in 32.8% of IDC. In IDC, β1 integrin was related with HER-2 (p = 0.019) and VEGF (p = 0.011) expression and it had a significant relationship with metastasis and death (p = 0.001 and p = 0.05, respectively). Kaplan-Meier survival analysis showed that the overexpression of this protein is very significant (p = 0.002) in specific survival (number of months between diagnosis and death caused by the disease). There were no correlation between IDC and DCIS (p = 0.559) regarding β1 integrin expression.

Conclusions

Considering that the expression of β1 integrin in breast cancer remains controversial, specially its relation with survival of patients, our findings provide further evidence that β1 integrin can be a marker of poor prognosis in breast cancer.

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/6652215267393871

Increased Cell-Matrix Adhesion upon Constitutive Activation of Rho Proteins by Cytotoxic Necrotizing Factors from E. Coli and Y. Pseudotuberculosis

Cytotoxic necrotizing factors (CNFs) encompass a class of autotransporter toxins produced by uropathogenic E. coli (CNF1) or Y. pseudotuberculosis (CNFy). CNF toxins deamidate and thereby constitutively activate RhoA, Rac1, and Cdc42. In this study, the effects of CNF1 on cell-matrix adhesion are analysed using functional cell-adhesion assays. CNF1 strongly increased cell-matrix binding of suspended Hela cells and decreased the susceptibly of cells to trypsin-induced cell detachment. Increased cell-matrix binding was also observed upon treatment of Hela cells with isomeric CNFy, that specifically deamidates RhoA. Increased cell-matrix binding thus appears to depend on RhoA deamidation. In contrast, increased cell spreading was specifically observed upon CNF1 treatment, suggesting that it rather depended on Rac1/Cdc42 deamidation. Increased cell-matrix adhesion is further presented to result in reduced cell migration of adherent cells. In contrast, migration of suspended cells was not affected upon treatment with CNF1 or CNFy. CNF1 and CNFy thus reduced cell migration specifically under the condition of pre-established cell-matrix adhesion.

Crossroads of integrins and cadherins in epithelia and stroma remodeling

Adhesion events mediated by cadherin and integrin adhesion receptors have fundamental roles in the maintenance of the physiological balance of epithelial tissues, and it is well established that perturbations in their normal functional activity and/or changes in their expression are associated with tumorigenesis. Over the last decades, increasing evidence of a dynamic collaborative interaction between these complexes through their shared interactions with cytoskeletal proteins and common signaling pathways has emerged not only as an important regulator of several aspects of epithelial cell behavior, but also as a coordinated adhesion module that senses and transmits signals from and to the epithelia surrounding microenvironment. The tight regulation of their crosstalk is particularly important during epithelial remodeling events that normally take place during morphogenesis and tissue repair, and when defective it leads to cell transformation and aggravated responses of the tumor microenvironment that contribute to tumorigenesis. In this review we highlight some of the interactions that regulate their crosstalk and how this could be implicated in regulating signals across epithelial tissues to sustain homeostasis.

The putative tumor suppressor VILIP-1 counteracts epidermal growth factor-induced epidermal-mesenchymal transition in squamous carcinoma cells

Epithelial-mesenchymal transition (EMT) is a crucial step for the acquisition of invasive properties of carcinoma cells during tumor progression. Epidermal growth factor (EGF)-treatment of squamous cell carcinoma (SCC) cells provokes changes in the expression of lineage markers, morphological changes, and a higher invasive and metastatic potential. Here we show that chronic stimulation with EGF induces EMT in skin-derived SCC cell lines along with the down-regulation of the epithelial marker E-cadherin, and of the putative tumor suppressor VILIP-1 (visinin-like protein 1). In esophageal squamous cell carcinoma and non-small cell lung carcinoma the loss of VILIP-1 correlates with clinicopathological features related to enhanced invasiveness. VILIP-1 has previously been shown to suppress tumor cell invasion via enhancing cAMP-signaling in a murine SCC model. In mouse skin SCC cell lines the VILIP-1-negative tumor cells have low cAMP levels, whereas VILIP-1-positive SCCs possess high cAMP levels, but low invasive properties. We show that in VILIP-1-negative SCCs, Snail1, a transcriptional repressor involved in EMT, is up-regulated. Snail1 expression is reduced by ectopic VILIP-1-expression in VILIP-1-negative SCC cells, and application of the general adenylyl cyclase inhibitor 2',3'-dideoxyadenosine attenuated this effect. Conversely, EGF-stimulation of VILIP-1-positive SCC cells leads to the down-regulation of VILIP-1 and the induction of Snail1 expression. The induction of Snail is inhibited by elevated cAMP levels. The role of cAMP in EMT was further highlighted by its suppressive effect on the EGF-induced enhancement of migration in VILIP-1-positive SCC cells. These findings indicate that VILIP-1 is involved in EMT of SCC by regulating the transcription factor Snail1 in a cAMP-dependent manner.

Involvement of host cell integrin α2 in Cryptosporidium parvum infection

Cryptosporidium parvum is an opportunistic pathogen in AIDS patients. It is an intracellular but extracytoplasmic parasite residing in a host cell-derived parasitophorous vacuole. It is still poorly understood how this parasite interacts with host cells. We observed that expression of the integrin α2 (ITGA2) gene in host cells was significantly upregulated upon C. parvum infection, and a higher level of ITGA2 protein was present in the parasite infection sites. The infection could be reduced by the treatment of antibodies against ITGA2 and integrin β1 (ITGB1) subunits, as well as by type I collagen (an integrin α2β1 ligand). We also generated stable knockdown of ITGA2 gene expression in HCT-8 cells and observed consistent reduction of parasite infection in these knockdown cells. Collectively, our evidence indicates that host cell ITGA2 might be involved in interacting with Cryptosporidium during infection, probably acting as part of the regulatory elements upstream of the reported recruiting and reorganization of F actin at the infection sites.

The EMILIN/Multimerin family

Elastin microfibrillar interface proteins (EMILINs) and Multimerins (EMILIN1, EMILIN2, Multimerin1, and Multimerin2) constitute a four member family that in addition to the shared C-terminus gC1q domain typical of the gC1q/TNF superfamily members contain a N-terminus unique cysteine-rich EMI domain. These glycoproteins are homotrimeric and assemble into high molecular weight multimers. They are predominantly expressed in the extracellular matrix and contribute to several cellular functions in part associated with the gC1q domain and in part not yet assigned nor linked to other specific regions of the sequence. Among the latter is the control of arterial blood pressure, the inhibition of Bacillus anthracis cell cytotoxicity, the promotion of cell death, the proangiogenic function, and a role in platelet hemostasis. The focus of this review is to highlight the multiplicity of functions and domains of the EMILIN/Multimerin family with a particular emphasis on the regulatory role played by the ligand-receptor interactions of the gC1q domain. EMILIN1 is the most extensively studied member both from the structural and functional point of view. The structure of the gC1q of EMILIN1 solved by NMR highlights unique characteristics compared to other gC1q domains: it shows a marked decrease of the contact surface of the trimeric assembly and while conserving the jelly-roll topology with two β-sheets of antiparallel strands it presents a nine-stranded β-sandwich fold instead of the usual 10-stranded fold. This is likely due to the insertion of nine residues that disrupt the ordered strand organization and forma a highly dynamic protruding loop. In this loop the residue E933 is the site of interaction between gC1q and the α4β1 and α9β1 integrins, and contrary to integrin occupancy that usually upregulates cell growth, when gC1q is ligated by the integrin the cells reduce their proliferative activity.

Integrin-α5 coordinates assembly of posterior cranial placodes in zebrafish and enhances Fgf-dependent regulation of otic/epibranchial cells

Vertebrate sensory organs develop in part from cranial placodes, a series of ectodermal thickenings that coalesce from a common domain of preplacodal ectoderm. Mechanisms coordinating morphogenesis and differentiation of discrete placodes are still poorly understood. We have investigated whether placodal assembly in zebrafish requires Integrin- α5 (itga5), an extracellular matrix receptor initially expressed throughout the preplacodal ectoderm. Morpholino knockdown of itga5 had no detectable effect on anterior placodes (pituitary, nasal and lens), but posterior placodes developed abnormally, resulting in disorganization of trigeminal and epibranchial ganglia and reduction of the otic vesicle. Cell motion analysis in GFP-transgenic embryos showed that cell migration in itga5 morphants was highly erratic and unfocused, impairing convergence and blocking successive recruitment of new cells into these placodes. Further studies revealed genetic interactions between itga5 and Fgf signaling. First, itga5 morphants showed changes in gene expression mimicking modest reduction in Fgf signaling. Second, itga5 morphants showed elevated apoptosis in the otic/epibranchial domain, which was rescued by misexpression of Fgf8. Third, knockdown of the Fgf effector erm had no effect by itself but strongly enhanced defects in itga5 morphants. Finally, proper regulation of itga5 requires dlx3b/4b and pax8, which are themselves regulated by Fgf. These findings support a model in which itga5 coordinates cell migration into posterior placodes and augments Fgf signaling required for patterning of these tissues and cell survival in otic/epibranchial placodes.

The cooperative action of bacterial fibronectin-binding proteins and secreted proteins promote maximal Campylobacter jejuni invasion of host cells by stimulating membrane ruffling

This study was performed to elucidate the host cell scaffolding and signalling molecules that Campylobacter jejuni utilizes to invade epithelial cells. We hypothesized that the C. jejuni fibronectin-binding proteins and secreted proteins are required for cell signalling and maximal invasion of host cells. C. jejuni binding to host cells via the CadF and FlpA fibronectin-binding proteins activated the epidermal growth factor (EGF) pathway, as evidenced by inhibitor studies and immunoprecipitation coupled with immunoblot analysis using antibodies reactive against total and active EGF receptor. Inhibitor studies revealed maximal C. jejuni host cell invasion was dependent upon PI3-Kinase, c-Src and focal adhesion kinase (FAK), all of which are known to participate in cytoskeletal rearrangements. Knockdown of endogenous Dock180, which is a Rac1-specific guanine nucleotide exchange factor, using siRNA revealed that C. jejuni invasion was significantly reduced compared with cells treated with scrambled siRNA. We further demonstrated that the C. jejuni Cia proteins are, in part, responsible for Rho GTPase Rac1 recruitment and activation, as judged by immunofluorescence microscopy and Rac1 activation. Based on these data, we present a model that illustrates that C. jejuni utilizes a coordinated mechanism involving both adhesins and secreted proteins to promote membrane ruffling and host cell invasion.

EMILIN1-α4/α9 integrin interaction inhibits dermal fibroblast and keratinocyte proliferation

The α4/α9 integrins directly engage the ECM glycoprotein EMILIN1 to inhibit skin cell proliferation upstream of TGF-β signaling.

EMILIN1 promotes α4β1 integrin–dependent cell adhesion and migration and reduces pro–transforming growth factor–β processing. A knockout mouse model was used to unravel EMILIN1 functions in skin where the protein was abundantly expressed in the dermal stroma and where EMILIN1-positive fibrils reached the basal keratinocyte layer. Loss of EMILIN1 caused dermal and epidermal hyperproliferation and accelerated wound closure. We identified the direct engagement of EMILIN1 to α4β1 and α9β1 integrins as the mechanism underlying the homeostatic role exerted by EMILIN1. The lack of EMILIN1–α4/α9 integrin interaction was accompanied by activation of PI3K/Akt and Erk1/2 pathways as a result of the reduction of PTEN. The down-regulation of PTEN empowered Erk1/2 phosphorylation that in turn inhibited Smad2 signaling by phosphorylation of residues Ser245/250/255. These results highlight the important regulatory role of an extracellular matrix component in skin proliferation. In addition, EMILIN1 is identified as a novel ligand for keratinocyte α9β1 integrin, suggesting prospective roles for this receptor–ligand pair in skin homeostasis.

MicroRNAs in the regulation of interfacial behaviors of MSCs cultured on microgrooved surface pattern

Cell-substrate interaction is one of the most important aspects of tissue engineering. Changes of MSCs interfacial behaviors were found to be triggered by 10 μm wide grooved pattern on poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx). Global marker genes expression and miRNAs profiling analysis provided insights into the regulation network of the topography induced MSCs' cell responses including adhesion, proliferation, differentiation and apoptosis. Compared to MSCs cultured on the smooth substrates, MSCs incubated on microgrooved PHBHHx substrates showed increased expression of osteogenesis-related marker genes including cbfa1, col1a1 and bmp2, and decreased expression of vcl, vinculin encoding gene, adipogenesis-related genes including lpl, des and acta2, as well as myogenesis-related genes of myh11 and nse. The miRNA microarrays revealed that 18 differentially-expressed miRNAs on microgrooved pattern had multiple target genes, contributing comprehensively to the cellular regulation process. Similar to the topography-triggered ostegenenesis, co-transfection of the osteogenic miRNAs combination (miR-140, miR-214, miR-320, miR-351 and miR-674-5p) was able to stimulate the expression of osteogenic marker genes. This study elucidated the important roles of miRNAs in the regulation processes of the microenvironment triggered cell behaviors, and provided clues for the PHA biomedical materials development.

Integrin signaling, cell survival, and anoikis: distinctions, differences, and differentiation

Cell survival and apoptosis implicate an increasing complexity of players and signaling pathways which regulate not only the decision-making process of surviving (or dying), but as well the execution of cell death proper. The same complex nature applies to anoikis, a form of caspase-dependent apoptosis that is largely regulated by integrin-mediated, cell-extracellular matrix interactions. Not surprisingly, the regulation of cell survival, apoptosis, and anoikis furthermore implicates additional mechanistic distinctions according to the specific tissue, cell type, and species. Incidentally, studies in recent years have unearthed yet another layer of complexity in the regulation of these cell processes, namely, the implication of cell differentiation state-specific mechanisms. Further analyses of such differentiation state-distinct mechanisms, either under normal or physiopathological contexts, should increase our understanding of diseases which implicate a deregulation of integrin function, cell survival, and anoikis.

Three-Dimensional Invasion of Epithelial–Mesenchymal Transition–Positive Human Peritoneal Mesothelial Cells into Collagen Gel is Promoted by the Concentration Gradient of Fibronectin

Background

In long-term peritoneal dialysis, myofibroblast-like cells found in the interstitium of the peritoneum are assumed to be a transformed type of mesothelial cell—epithelial-mesenchymal transition-positive [EMT(+)] human peritoneal mesothelial cells (HPMCs)—because they express a mesothelial marker, cytokeratin. However, no direct evidence about how these cells are able to invade from the mesothelium has yet been obtained.

Aim

In this study, we aimed to verify whether EMT(+) HPMCs would, in vitro, invade three-dimensionally along certain chemotactic factors.

Methods

We used reverse-transcriptase polymerase chain reaction to measure expression of Snail, E-cadherin, α5-integrin, and matrix metalloproteinase 2 (MMP2) messenger RNA (mRNA) in HPMCs exposed to 10 ng/mL transforming growth factor β1 (TGFβ1) and how that expression corresponds to cell motility, as represented by a video movie. We used the Transwell (12 μm pore diameter: Sigma-Aldrich, Tokyo, Japan) to construct a three-dimensional (3D) cell migration chamber. In the lower chamber, a concentration gradient of fibronectin (FN) or albumin(Alb) was formed in 0.1% type I collagen by diffusion ( C0 = 22 nmol/L; concentration gradient: C / C0 = 0.7). All cells beneath the membrane were counted 72 hours after 5x104 EMT(+) HPMCs (HPMCs after a 48-hour exposure to 10 ng/mL TGFβ1) had been spread in the upper chamber.

Results

After 72 hours, the increased motility of HPMCs resulting from their exposure to 10 ng/mL TGFβ1 had returned to baseline, but they retained an elongated morphology. Expression of Snail and MMP2 mRNA reached maximum at 24 hours. Expression of E-cadherin declined, and expression of α5-integrin increased continuously. In the 3D invasion study, significantly enhanced invasion by EMT(+) but not EMT(-) HPMCs was clearly seen in the presence of a FN concentration gradient ( p < 0.01), although invasion by EMT(+) and EMT(-) HPMCs in the absence of a FN concentration gradient was not statistically significantly different. Compared with the EMT(+) control (no concentration gradient), invasion by EMT(+) HPMCs was 2.1 ± 0.5 times (p < 0.05) and 1.4 ± 0.4 times (p = nonsignificant) higher along the FN and Alb concentration gradients respectively. Increased invasion along the FN concentration gradient was significantly inhibited (p < 0.05) when the HPMCs were pre-incubated with 5 μg/mL RGDS (a blocker for α5-integrin to FN).

Conclusions

We conclude that EMT(+) HPMCs invade collagen gel along the FN concentration gradient because of specific binding to RGDS receptors, which bind integrins such as α5-integrin, upregulating invasion-related gene expression associated with synthesis of the cytoskeleton protein α smooth muscle actin.