The mediating role of joint attention in the relationship between motor skills and receptive and expressive language in siblings at risk for autism spectrum disorder

Language problems are highly prevalent in younger siblings of children with autism spectrum disorder (HR-sibs), yet little is known about early predictors. There is growing evidence that motor and language development are linked and this connection might be mediated by joint attention. Developmental changes in motor abilities change how children interact with objects and people (e.g., by showing), which may influence language development. This association has however not yet been studied in HR-sibs. The interrelationship between motor, joint attention and language skills was explored in younger siblings of typically developing children (LR-sibs, N = 31) and HR-sibs (N = 32). In both groups, motor skills (composite of fine and gross motor skills) at 10 months influenced receptive and expressive language at 36 months directly and indirectly through joint attention at 14 months. Group status moderated this direct and indirect effect with mainly significant effects in HR-sibs. This indicates that lower motor skills can have cascading effects on joint attention and language in HR-sibs. Consequently, assessment of early motor skills in HR-sibs might hold promise for early identification of motor difficulties but can also be indicative of language difficulties later in life, especially when difficulties with joint attention are also present.

Down-regulation of myopodin expression reduces invasion and motility of PC-3 prostate cancer cells

Enhanced motility of cancer cells by remodelling of the actin cytoskeleton is crucial in the process of cancer cell invasion and metastasis. Although several studies propose a tumor suppressor role for the actin bundling protein myopodin, it was also shown previously that overexpression of mouse myopodin promotes invasion in vitro. In the present study, the role of myopodin in human cancer cell motility and invasion was explored using RNA interference with siRNA duplexes designed to down-regulate all human myopodin isoforms currently identified. We show that down-regulation of myopodin expression in human cancer cells significantly reduces the invasive properties of these cells both in collagen type I and in Matrigel. Furthermore, the motile characteristics of cancer cells are also curbed by reduced myopodin expression whereas cell-cell contacts are reinforced. These results point to a role for myopodin as tumor activator. While these findings are at variance with the suggested tumor suppressor role for myopodin, we hypothesize that the subcellular localization of the protein is involved in its suppressor or activator function in tumorigenesis.

Insulin-like growth factor-I receptor, E-cadherin and alpha v integrin form a dynamic complex under the control of alpha-catenin

Dynamic crosstalk between cell adhesion molecules, extracellular matrix and soluble informative factors is essential for cancer cell migration and invasion. Here, we investigated the mechanisms by which the E-cadherin/catenin complex and alpha v integrin can modulate insulin-like growth factor-I (IGF-I)-induced cell migration. Human colon mucosa, human colon cancer cell lines, HT29-D4 and HCT-8 derivatives that differ in their expression of alpha-catenin, were used as models. Interactions between E-cadherin, alpha v integrin and IGF-I receptor (IGF-IR) were analyzed by coimmunoprecipitation and immunolocalization experiments. The impact of these interactions on cell mobility was determined by haptotaxis assays. We report that alpha v integrin, E-cadherin and IGF-IR form a ternary complex in both cultured cancer cells and human normal colonic mucosa. alpha-Catenin regulates the scaffolding of this complex. IGF-IR ligation by IGF-I induces the disruption of the complex and the relocalization of alpha v integrin from cell-cell contacts to focal contact sites. This perturbation is correlated with the observed increase in cell migration. These results suggest that regulation of the alpha v integrin/E-cadherin/IGF-IR scaffolding is essential for the modulation of cell mobility. Its alteration could be of major importance to sustain alterations in cell adhesion that occur during cancer cell invasion and metastasis.

Activation of the FAK-src molecular scaffolds and p130Cas-JNK signaling cascades by alpha1-integrins during colon cancer cell invasion

Increased src tyrosine kinase expression and activity has been associated with colon cancer cell invasion and survival. Several signaling pathways are involved in the oncogenic activation of src during the adenoma to carcinoma progression and cellular invasion. In the present study, the synthetic ether lipid analog ET-18-OMe was shown to promote invasion of HCT-8/S11 colon cancer cells into collagen type I through the concomitant activation of src by phosphorylation at Tyr416 (5-30 min) in alpha1-integrin immunoprecipitates containing the integrin binding proteins talin and paxillin, as well as the phoshorylated and activated forms of focal adhesion kinase (FAK) at Tyr397 (a FAK kinase activation signal), Tyr576 and Tyr861. This was associated with the lateral redistribution of alpha1-integrins in focal aggregates and persistent activation of the p130Cas/JNK pathways at 5-30 min, with the subsequent induction and activation of the matrix metalloproteinases MMP-2 and MMP-9 (2-12 h). These activated molecular scaffolds and signaling cascades were not observed in immunoprecipitates of alpha2- and beta1-integrins, and tetraspanin CD9, an invasion and metastasis suppressor linked to integrins and FAK signaling. Our data demonstrate that the lateral redistribution and clustering of alpha1-integrins results in the recruitment of the FAK/src motility-promoting signaling complex involved in cancer cell invasion. Disruption of this proinvasive pathway was accomplished by the dominant negative mutant of src (K295R, kinase dead), src pharmacological inhibitor (PP1) and alpha1-integrin function blocking antibodies. These findings support the notion that the alpha1-integrin- and src-dependent signalosome is a relevant therapeutic target against tumor progression in colon cancer patients.

Downregulation of gelsolin family proteins counteracts cancer cell invasion in vitro

Gelsolin and CapG are both actin binding proteins that modulate a variety of physiological processes by interacting differently with the actin cytoskeleton. Several studies suggest that overexpression of these proteins promotes invasion in vitro. In this study we explored the contribution of these proteins in human cancer cell invasion and motility. We show that down regulation of CapG or gelsolin in several types of cancer cells, including MDA-MB 231 and PC-3 cells, significantly reduces the invasive and motile properties of cells, as well as cell aggregation. These results point to a role for CapG and gelsolin as tumor activator.

Proinvasive activity of BMP-7 through SMAD4/src-independent and ERK/Rac/JNK-dependent signaling pathways in colon cancer cells

Recent data indicate that the Bone Morphogenetic Protein BMP-7 exhibits mucosal protection against experimental colitis in rats, suggesting that this cytokine exerts direct actions in intestinal epithelial cells during inflammatory bowel diseases and other precancerous lesions of the colon. In this study, we investigated the functional expression of BMP-7 and its receptors in normal human colon crypts, aberrant crypt foci (ACF) in sigmoiditis and colorectal tumors, and their derived cancer cell lines. Transcripts encoding BMP-7 receptors type II (BMPRII, ActRII, ActRIIB) and type I (ALK-2) were clearly detected by RT-PCR in several premalignant and carcinoma cell lines. The cytokine was identified by immunohistochemistry in surface epithelial cells and crypts in the normal colon mucosa, ACF in sigmoiditis, sporadic high grade dysplastic adenoma, and in 9 of 16 colon carcinomas (56.2%). In addition, the conditioned medium collected from the adenoma PC/AA/C1 and carcinoma HCT8/S11 and SW48 cell lines in culture contained significant levels of BMP-7 ranging from 0.17 to 0.38 ng/ml. We found that BMP-7 induced scattering and proinvasive responses (EC50=1 ng/ml) in kidney and colon cancer cell lines through SMAD4 and src -independent pathways and signaling cascades using FAK phosphorylation at Y925 and activation of ERK1/2, Rac1 and JNK. This phosphorylation of FAK on Y925 was also induced by the proinvasive agent EGF. Taken together, our findings suggest that BMP-7 exerts divergent effects in the colon mucosa, one counteracting transient inflammatory situations and the other linked to pejorative functions during chronic ulcerative diseases and the neoplastic progression.

The tandem PDZ domains of syntenin promote cell invasion

Syntenin is a tandem PDZ protein that has recently been shown to be overexpressed in several cancer cells and tissues, and that might play an active role in tumor cell invasion and metastasis. Here we show that overexpression of the tandem PDZ domains of syntenin in non-invasive cells is necessary and sufficient to stimulate these cells to invade a collagen I matrix, and this effect can be regulated by ligand binding to the PDZ domains. Furthermore, we show that syntenin-induced invasion requires signaling through ras, rho and PI3K/MAPK signaling pathways and involves changes in cell-cell adhesion. Inversely, when we used RNA interference to inhibit syntenin expression in different invasive cancer cell lines, we observed a drastically decreased ability of these cells to migrate and invade into collagen type I or Matrigel. RNAi-treated cells also show increased cell aggregation, indicating that syntenin is important for cell-cell adhesion in epithelial cells. Together, these results suggest that downregulation of syntenin by RNA interference could provide a means of inhibiting tumor invasion and possibly metastasis in different cancers, and point to syntenin as a potential cancer biomarker and drug target.

Phosphorylation on Ser5 increases the F-actin-binding activity of L-plastin and promotes its targeting to sites of actin assembly in cells

L-plastin, a malignant transformation-associated protein, is a member of a large family of actin filament cross-linkers. Here, we analysed how phosphorylation of L-plastin on Ser5 of the headpiece domain regulates its intracellular distribution and its interaction with F-actin in transfected cells and in in vitro assays. Phosphorylated wild-type L-plastin localised to the actin cytoskeleton in transfected Vero cells. Ser5Ala substitution reduced the capacity of L-plastin to localise with peripheral actin-rich membrane protrusions. Conversely, a Ser5Glu variant mimicking a constitutively phosphorylated state, accumulated in actin-rich regions and promoted the formation of F-actin microspikes in two cell lines. Similar to phosphorylated wild-type L-plastin, this variant remained associated with cellular F-actin in detergent-treated cells, whereas the Ser5Ala variant was almost completely extracted. When compared with non-phosphorylated protein, phosphorylated L-plastin and the Ser5Glu variant bound F-actin more efficiently in an in vitro assay. Importantly, expression of L-plastin elicited collagen invasion in HEK293T cells, in a manner dependent on Ser5 phosphorylation. Based on our findings, we propose that conversely to other calponin homology (CH)-domain family members, phosphorylation of L-plastin switches the protein from a low-activity to a high-activity state. Phosphorylated L-plastin might act as an integrator of signals controlling the assembly of the actin cytoskeleton and cell motility in a 3D-space.

Opposing roles of netrin-1 and the dependence receptor DCC in cancer cell invasion, tumor growth and metastasis

Deleted in colon cancer (DCC) and UNC5 function as netrin dependence receptors by inducing apoptosis in the absence of their ligand and accordingly were recently designated as putative conditional tumor suppressors. Herein, we determined whether netrin-1 and its receptors are implicated in cancer cell invasion and tumor progression. Expression of DCC, UNC5 and adenosine A2B-receptors (A2B-Rs) was investigated by reverse transcription polymerase chain reaction in human colon cancer cells. The impact of DCC restitution and netrin-1 was evaluated on collagen type I invasion, tumor growth and metastasis in nude mice, cancer cell survival and gene expression profiling. Flow cytometry, poly(ADP-ribose)polymerase-1 and caspase-8 activation were used to evaluate the impact of DCC on cell death. Both netrin-1 and A2B-R activation induced the invasive phenotype through the Rho-Rho kinase axis in DCC-deficient human colorectal cancer cells. Restitution of wild-type DCC blocked invasion induced by netrin-1, A2B-R agonist and other agents. Ectopic expression of netrin-1 led to increased growth of human colon tumor xenografts in athymic mice. Conversely, introduction of wt-DCC in kidney MDCKts.src-ggl cells strongly inhibited metastasis in lymph nodes and lungs and increased sensitivity to apoptosis in hypoxia. DNA microarrays revealed that netrin and DCC had common and divergent impacts on gene expression linked to cell cycle, survival, surface signaling and adhesion. Our findings underscore that netrin is a potent invasion and tumor growth-promoting agent and that DCC is a metastasis suppressor gene targeting both proinvasive and survival pathways in a cumulative manner.

E-cadherin regulates human Nanos1, which interacts with p120ctn and induces tumor cell migration and invasion

Down-regulation of the epithelial cell-cell adhesion molecule E-cadherin is frequently associated with tumor formation and progression. Besides its role in physical cell-cell adhesion, E-cadherin is also thought to be involved in intracellular signaling in normal epithelial cells. In these cells, the Armadillo catenin p120ctn binds to the cytoplasmic domain of E-cadherin and stabilizes the adhesion complexes. On loss of E-cadherin, cytoplasmic p120ctn might accumulate and contribute to tumor malignancy. We used suppression subtractive hybridization to search for genes regulated by E-cadherin expression. We isolated human Nanos1 as a transcript of which levels decrease on E-cadherin reexpression in a human breast cancer cell line. The hNanos1 protein bears a COOH-terminal (CCHC)(2) zinc finger domain and belongs to an evolutionarily conserved protein family sharing functions in germ cell development in both vertebrates and invertebrates. We found an inverse correlation between E-cadherin and hNanos1 expression in various cell lines and under diverse conditions. Conditional expression of hNanos1 in human colorectal DLD1 cancer cells functionally abolished cell-cell adhesion. It induced cytoplasmic translocation of p120ctn, as well as strong migratory and invasive properties. We also found that the NH(2)-terminal domain of hNanos1, which is conserved only among mammals, interacts with p120ctn. hNanos1 counteracted the stimulatory effect of p120ctn on cell protrusion formation. Together, these findings describe a new function for hNanos1 as a downstream effector of E-cadherin loss contributing to tumor progression. Targeting hNanos1 might be a promising strategy in the treatment of E-cadherin-negative tumors in particular.

Inhibition of vascular endothelial growth factor (VEGF)-165 and semaphorin 3A-mediated cellular invasion and tumor growth by the VEGF signaling inhibitor ZD4190 in human colon cancer cells and xenografts

We recently showed by DNA microarray analysis that vascular endothelial growth factor (VEGF) receptor (VEGFR) is expressed in HCT8/S11 human colon cancer cells, suggesting that several angiogenic factors may target colon cancer cells themselves. In this study, transcripts encoding the VEGF-165 and semaphorin 3A (Sema3A) receptors and coreceptors Flt-1, KDR/Flk-1, plexin A1, and neuropilins NP-1 and NP-2 were identified by reverse transcription-PCR in the human colon cancer cell lines HCT8/S11, HT29, HCT116, and PCmsrc. Collagen invasion induced by VEGF-165 and Sema3A in HCT8/S11 cells (EC(50), 0.4-1 nmol/L) required p42/44 mitogen-activated protein kinase and signaling through RhoA/Rho-kinase-dependent and -independent pathways, respectively. As expected, the VEGFR signaling inhibitor ZD4190 selectively abrogated the proinvasive activity of VEGF in collagen gels (IC(50), 10 nmol/L) and chick heart fragments. We identify a novel function for VEGF-165 and Sema3A as proinvasive factors for human colorectal cancer cells. Interestingly, oral administration of the single drug ZD4190 to athymic mice (50 mg/kg/d, once daily) inhibited by 70% the growth of HCT8/S11 tumor cell xenografts. Combinations between the src tyrosine kinase inhibitor M475271 and ZD4190 or cisplatin resulted in additive therapeutic activity against LNM35 human lung tumor xenografts. Our data have significant implications for new therapeutic approaches and individualized treatment targeting VEGFR and src signaling pathways in combination with established clinical drugs at primary tumors and distant metastases in colon and lung cancer patients.

Anticancer activity of BIM-46174, a new inhibitor of the heterotrimeric Galpha/Gbetagamma protein complex

A large number of hormones and local agonists activating guanine-binding protein-coupled receptors (GPCR) play a major role in cancer progression. Here, we characterize the new imidazo-pyrazine derivative BIM-46174, which acts as a selective inhibitor of heterotrimeric G-protein complex. BIM-46174 prevents the heterotrimeric G-protein signaling linked to several GPCRs mediating (a) cyclic AMP generation (Galphas), (b) calcium release (Galphaq), and (c) cancer cell invasion by Wnt-2 frizzled receptors and high-affinity neurotensin receptors (Galphao/i and Galphaq). BIM-46174 inhibits the growth of a large panel of human cancer cell lines, including anticancer drug-resistant cells. Exposure of cancer cells to BIM-46174 leads to caspase-3-dependent apoptosis and poly(ADP-ribose) polymerase cleavage. National Cancer Institute COMPARE analysis for BIM-46174 supports its novel pharmacologic profile compared with 12,000 anticancer agents. The growth rate of human tumor xenografts in athymic mice is significantly reduced after administration of BIM-46174 combined with either cisplatin, farnesyltransferase inhibitor, or topoisomerase inhibitors. Our data validate the feasibility of targeting heterotrimeric G-protein functions downstream the GPCRs to improve anticancer chemotherapy.

Expression of Neurotensin and NT1 Receptor in Human Breast Cancer: A Potential Role in Tumor Progression

Emerging evidence supports neurotensin as a trophic and antiapoptotic factor, mediating its control via the high-affinity neurotensin receptor (NT1 receptor) in several human solid tumors. In a series of 51 patients with invasive ductal breast cancers, 34% of all tumors were positive for neurotensin and 91% positive for NT1 receptor. We found a coexpression of neurotensin and NT1 receptor in a large proportion (30%) of ductal breast tumors, suggesting a contribution of the neurotensinergic signaling cascade within breast cancer progression. Functionally expressed NT1 receptor, in the highly malignant MDA-MB-231 human breast cancer cell line, coordinated a series of transforming functions, including cellular migration, invasion, induction of the matrix metalloproteinase (MMP)-9 transcripts, and MMP-9 gelatinase activity. Disruption of NT1 receptor signaling by silencing RNA or use of a specific NT1 receptor antagonist, SR48692, caused the reversion of these transforming functions and tumor growth of MDA-MB-231 cells xenografted in nude mice. Our findings support the contribution of neurotensin in human breast cancer progression and point out the utility to develop therapeutic molecules targeting neurotensin or NT1 receptor signaling cascade. These strategies would increase the range of therapeutic approaches and be beneficial for specific patients.

Induction of the adenoma-carcinoma progression and Cdc25A-B phosphatases by the trefoil factor TFF1 in human colon epithelial cells

TFF1 is overexpressed in inflammatory diseases and human cancers of the digestive and urogenital systems. To examine the transforming potential of TFF1 in human colon epithelial cells, premalignant PC/AA/C1 adenoma cells (PC) derived from a patient with familial adenomatous polyposis (FAP) were transformed by the TFF1 cDNA and used as a model of the adenoma-carcinoma transition. Constitutive expression of TFF1 increased anchorage-independent cell growth in soft agar, and induced or potentiated the growth of colon PC-TFF1 and kidney MDCKts.src-TFF1 tumor xenografts in athymic mice. This resulted in reduction of thapsigargin-induced apoptosis and promotion of collagen type I invasion through several oncogenic pathways. Using the differential display approach to identify TFF1 target genes, we found that the dual specific phosphatases Cdc25A and B implicated in cell cycle transitions are strongly upregulated under active forms in both PC-TFF1 and HCT8/S11-TFF1 colon cancer cells. Accordingly, TFF1 expression is absent in normal human colon crypts but is induced in correlation with Cdc25a and b transcript levels and tumor grade in familial and sporadic colon adenomas and carcinomas. We propose that TFF1 and Cdc25A-B cooperate with other dominant oncogenic pathways to induce the adenoma and adenocarcinoma transitions. Agents that target TFF1/Cdc25 signaling pathways may be useful for treating patients with TFF1-positive solid tumors.

Commutators of PAR-1 signaling in cancer cell invasion reveal an essential role of the Rho-Rho kinase axis and tumor microenvironment

We recently reported that proteinase-activated receptors type I (PAR-1) are coupled to both negative and positive invasion pathways in colonic and kidney cancer cells cultured on collagen type I gels. Here, we found that treatments with the cell-permeant analog 8-Br-cGMP and the soluble guanylate cyclase activator BAY41-2272, and Rho kinase (ROK) inhibition by Y27632 or a dominant negative form of ROK lead to PAR-1-mediated invasion through differential Rac1 and Cdc42 signaling. Hypoxia or the counteradhesive matricellular protein SPARC/BM-40 (SPARC: secreted protein acidic rich in cysteine) overexpressed during cancer progression also commutated PAR-1 to cellular invasion through the cGMP/protein kinase G (PKG) cascade, RhoA inactivation, and Rac1-dependent or -independent signaling. Cultured primary cancer cells isolated from peritoneal and pleural effusions from patients with colon cancer or other malignant tumors harbored PAR-1, as shown by RT-PCR and FACS analyses. These malignant effusions also contained high levels of activated thrombin and fibrin, and induced a proinvasive response in HCT8/S11 human colorectal cancer cells. Our data underline the essential role of the tumor microenvironment and of several commutators targeting cGMP/PKG signaling and the RhoA-ROK axis in the control of PAR-1 proinvasive activity and metastatic potential of cancer cells in distant organs and peritoneal or pleural cavities. We also add new insights into the mechanisms linking the coagulation mediators thrombin and PAR-1 in the context of blood coagulation disorders and venous thrombosis often observed in cancer patients, as described in 1865 by Armand Trousseau.

SIP1/ZEB2 induces EMT by repressing genes of different epithelial cell-cell junctions

SIP1/ZEB2 is a member of the deltaEF-1 family of two-handed zinc finger nuclear factors. The expression of these transcription factors is associated with epithelial mesenchymal transitions (EMT) during development. SIP1 is also expressed in some breast cancer cell lines and was detected in intestinal gastric carcinomas, where its expression is inversely correlated with that of E-cadherin. Here, we show that expression of SIP1 in human epithelial cells results in a clear morphological change from an epithelial to a mesenchymal phenotype. Induction of this epithelial dedifferentiation was accompanied by repression of several cell junctional proteins, with concomitant repression of their mRNA levels. Besides E-cadherin, other genes coding for crucial proteins of tight junctions, desmosomes and gap junctions were found to be transcriptionally regulated by the transcriptional repressor SIP1. Moreover, study of the promoter regions of selected genes by luciferase reporter assays and chromatin immunoprecipitation shows that repression is directly mediated by SIP1. These data indicate that, during epithelial dedifferentiation, SIP1 represses in a coordinated manner the transcription of genes coding for junctional proteins contributing to the dedifferentiated state; this repression occurs by a general mechanism mediated by Smad Interacting Protein 1 (SIP1)-binding sites.

Neurotensin receptor 1 gene activation by the Tcf/beta-catenin pathway is an early event in human colonic adenomas

Alterations in the Wnt/APC (adenomatous polyposis coli) signalling pathway, resulting in beta-catenin/T cell factor (Tcf)-dependent transcriptional gene activation, are frequently detected in familial and sporadic colon cancers. The neuropeptide neurotensin (NT) is widely distributed in the gastrointestinal tract. Its proliferative and survival effects are mediated by a G-protein coupled receptor, the NT1 receptor. NT1 receptor is not expressed in normal colon epithelial cells, but is over expressed in a number of cancer cells and tissues suggesting a link to the outgrowth of human colon cancer. Our results demonstrate that the upregulation of NT1 receptor occurring in colon cancer is the result of Wnt/APC signalling pathway activation. We first established the functionality of the Tcf response element within the NT1 receptor promoter. Consequently, we observed the activation of NT1 receptor gene by agents causing beta-catenin cytosolic accumulation, as well as a strong decline of endogenous receptor when wt-APC was restored. At the cellular level, the re-establishment of wt-APC phenotype resulted in the impaired functionality of NT1 receptor, like the breakdown in NT-induced intracellular calcium mobilization and the loss of NT pro-invasive effect. We corroborated the Wnt/APC signalling pathway on the NT1 receptor promoter activation with human colon carcinogenesis, and showed that NT1 receptor gene activation was perfectly correlated with nuclear or cytoplasmic beta-catenin localization while NT1 receptor was absent when beta-catenin was localized at the cell-cell junction in early adenomas of patients with familial adenomatous polyposis, hereditary non-polyposis colorectal cancer and loss of heterozygosity tumours. In this report we establish a novel link in vitro between the Tcf/beta-catenin pathway and NT1 receptor promoter activation.

Nerve growth factor mediates its pro-invasive effect in parallel with the release of a soluble E-cadherin fragment from breast cancer MCF-7/AZ cells

To define better the function of Nerve Growth Factor (NGF) in breast cancer progression, we investigated whether this polypeptide was able to induce breast cancer cell invasion. NGF inhibited aggregation of tumour cells through modulation of the E-cadherin/catenin complex function. In addition, NGF induced the breast cancer cells to invade into Matrigel. We focused our attention on how NGF prevents aggregation, in order to discover the signalling pathway that leads tumour cells to acquire the invasive phenotype. Moreover, studies on the identification of signalling pathways that are responsive for NGF-induced invasion will be basically described.

The transcription factor snail induces tumor cell invasion through modulation of the epithelial cell differentiation program

Abberant activation of the process of epithelial-mesenchymal transition in cancer cells is a late event in tumor progression. A key inducer of this transition is the transcription factor Snail, which represses E-cadherin. We report that conditional expression of the human transcriptional repressor Snail in colorectal cancer cells induces an epithelial dedifferentiation program that coincides with a drastic change in cell morphology. Snail target genes control the establishment of several junctional complexes, intermediate filament networks, and the actin cytoskeleton. Modulation of the expression of these genes is associated with loss of cell aggregation and induction of invasion. Chromatin immunoprecipitation experiments showed that repression of selected target genes is associated with increased binding of Snail to their promoters, which contain consensus Snail-binding sites. Thus, Snail constitutes a master switch that directly represses the epithelial phenotype, resulting in malignant carcinoma cells.

Molecular basis for dissimilar nuclear trafficking of the actin-bundling protein isoforms T- and L-plastin

T- and L-plastin are highly similar actin-bundling proteins implicated in the regulation of cell morphology, lamellipodium protrusion, bacterial invasion and tumor progression. We show that T-plastin localizes predominantly to the cytoplasm, whereas L-plastin distributes between nucleus and cytoplasm in HeLa or Cos cells. T-plastin shows nuclear accumulation upon incubation of cells with the CRM1 antagonist leptomycin B (LMB). We identified a Rev-like nuclear export sequence (NES) in T-plastin that is able to export an otherwise nuclear protein in an LMB-dependent manner. Deletion of the NES promotes nuclear accumulation of T-plastin. Mutation of residues L17, F21 or L26 in the T-plastin NES inhibits nuclear efflux. L-plastin harbors a less conserved NES and lacks the F21 T-plastin residue. Insertion of a Phe residue in the L-plastin NES specifically enhances its export activity. These findings explain why both isoforms exhibit specific distribution patterns in eukaryotic cells.

The cancer chemopreventive agent resveratrol induces tensin, a cell–matrix adhesion protein with signaling and antitumor activities

During a search to identify resveratrol (3,5,4'-trihydroxy-trans-stilbene, RV) target genes in the human erythroleukemic K562 cell line, we show here that the tensin gene and protein levels are remarkably induced by this dietary polyphenol. Tensin, a cell-matrix adhesion protein binding the integrins and cytoskeletal actin filaments also interacts with PI3-kinase and JNK signaling pathways. Tensin induction by RV is associated with increased K562 cell adhesion to fibronectin, cell spreading and actin polymerization. The same responses were observed in the tensin-deficient MCF7 human breast cancer cell line. In K562 and MCF7 cells treated by RV, tensin was found in punctate and intracytoplasmic areas. In MCF7 epithelial cells, induction of tensin is not exclusively associated with plasma membrane-bound vinculin, suggesting a dual localization of tensin in both focal and fibrillar adhesions. Pharmacological blockade of PI3-kinase and Rho GTPases/Rho-kinase resulted in selective depletion of focal adhesions, disorganization of tensin localization and disruption of stress fibers. RV increased cell motility and attachment to fibronectin in MCF7 cells submitted to mechanical laminar flow stress, and abrogated estrogen-induced MCF7 cancer cell invasion. Our data support the conclusion that induction of tensin by RV contributes to the chemopreventive and anti-invasive activity of this natural dietary compound in tensin-negative and -deficient leukemic cells or epithelioid cancers.

Implication of STAT3 signaling in human colonic cancer cells during intestinal trefoil factor 3 (TFF3) -- and vascular endothelial growth factor-mediated cellular invasion and tumor growth

Signal transducer and activator of transcription (STAT) 3 is overexpressed or activated in most types of human tumors and has been classified as an oncogene. In the present study, we investigated the contribution of the STAT3s to the proinvasive activity of trefoil factors (TFF) and vascular endothelial growth factor (VEGF) in human colorectal cancer cells HCT8/S11 expressing VEGF receptors. Both intestinal trefoil peptide (TFF3) and VEGF, but not pS2 (TFF1), activate STAT3 signaling through Tyr(705) phosphorylation of both STAT3alpha and STAT3beta isoforms. Blockade of STAT3 signaling by STAT3beta, depletion of the STAT3alpha/beta isoforms by RNA interference, and pharmacologic inhibition of STAT3alpha/beta phosphorylation by cucurbitacin or STAT3 inhibitory peptide abrogates TFF- and VEGF-induced cellular invasion and reduces the growth of HCT8/S11 tumor xenografts in athymic mice. Differential gene expression analysis using DNA microarrays revealed that overexpression of STAT3beta down-regulates the VEGF receptors Flt-1, neuropilins 1 and 2, and the inhibitor of DNA binding/differentiation (Id-2) gene product involved in the neoplastic transformation. Taken together, our data suggest that TFF3 and the essential tumor angiogenesis regulator VEGF(165) exert potent proinvasive activity through STAT3 signaling in human colorectal cancer cells. We also validate new therapeutic strategies targeting STAT3 signaling by pharmacologic inhibitors and RNA interference for the treatment of colorectal cancer patients.

Implication of the MAGI‐1b/PTEN signalosome in stabilization of adherens junctions and suppression of invasiveness

We recently established the critical role of the lipid phosphatase activity of the PTEN tumor suppressor in stabilizing cell-cell contacts and suppressing invasiveness. To delineate the effector systems involved, we investigated the interaction of PTEN with E-cadherin junctional complexes in kidney and colonic epithelial cell lines. PTEN and the p85 regulatory subunit of phosphatidylinositol 3-OH kinase (PI3K) co-immunoprecipitated with E-cadherin and catenins. By using a yeast two-hybrid assay, we demonstrated that PTEN interacted indirectly with beta-catenin by binding the scaffolding protein MAGI-1b. This model was corroborated in various ways in mammalian cells. Ectopic expression of MAGI-1b potentiated the interaction of PTEN with junctional complexes, promoted E-cadherin-dependent cell-cell aggregation, and reverted the Src-induced invasiveness of kidney MDCKts-src cells. In this model, MAGI-1b slightly decreased the activity of AKT, a downstream effector of PI3K. By using dominant-negative and constitutively active AKT expression vectors, we demonstrated that this kinase was included in the pathways involved in Src-induced destabilization of junctional complexes and was necessary and sufficient to trigger invasiveness. We propose that the recruitment of PTEN at adherens junctions by MAGI-1b and the local down-regulation of phosphatidylinositol-3,4,5-trisphosphate pools and downstream effector systems at the site of cell-cell contacts are focal points for restraining both disruption of junctional complexes and induction of tumor cell invasion.

The proinvasive activity of Wnt‐2 is mediated through a noncanonical Wnt pathway coupled to GSK‐3β and c‐ Jun/AP‐1 signaling

Inappropriate activation of the Wnt/APC/beta-catenin signaling pathways plays a critical role at early stages in a variety of human cancers. However, their respective implication in tumor cell invasion is still hypothetical. Here, we show that two activators of the canonical Wnt/beta-catenin transcription pathway, namely Dvl-2, the Axin 501-560 fragment binding glycogen synthase kinase -3beta (GSK-3beta), and the negative Wnt regulator wt-Axin did not alter cell invasion into type I collagen. In addition, both Dvl-2 and Axin 501-560 exerted a permissive action on the proinvasive activity of HGF and intestinal trefoil factor. Upstream activation of Wnt signaling by the Wnt-2 and Wnt-3a ligands, stable overexpression of Wnt-2, as well as GSK-3beta inhibition by lithium, SB216763, and GSK-3beta dominant negative forms (K85R and R96E) conferred the invasive phenotype through several proinvasive pathways. Induction of the matrix metalloprotease MMP-7 (matrilysin) gene and protein by Wnt-2 was abolished by inactivation of the AP-1 binding site in the promoter. Accordingly, invasion induced by Wnt-2 was prevented by soluble FRP-3 and FRP-1, sequestration of Gbetagamma subunits, depletion of the GSK-3beta protein by RNA interference, the c-Jun dominant negative mutant TAM67 and was not reversed by wt-Axin. Thus, the proinvasive activity of Wnt-2 is mediated by a noncanonical Wnt pathway using GSK-3beta and the AP-1 oncogene. Our data provide a potential clue for our understanding of the action and crosstalk between Wnt activators and other proinvasive pathways, in relation with matrix substrates and proteases in human cancers.

Increased importin-beta-dependent nuclear import of the actin modulating protein CapG promotes cell invasion

CapG (gCap39) is a ubiquitous gelsolin-family actin modulating protein involved in cell signalling, receptor-mediated membrane ruffling, phagocytosis and motility. CapG is the only gelsolin-related actin binding protein that localizes constitutively to both nucleus and cytoplasm. Structurally related proteins like severin and fragmin are cytoplasmic because they contain a nuclear export sequence that is absent in CapG. Increased CapG expression has been reported in some cancers but a causal role for CapG in tumour development, including invasion and metastasis, has not been explored. We show that moderate expression of green fluorescent protein-tagged CapG (CapG-EGFP) in epithelial cells induces invasion into collagen type I and precultured chick heart fragments. Nuclear export sequence-tagged CapG-EGFP fails to induce invasion, whereas point mutations in the nuclear export sequence permitting nuclear re-entry restore cellular invasion. Nuclear import of CapG is energy-dependent and requires the cytosolic receptor importin beta but not importin alpha. Nuclear CapG does not possess intrinsic transactivation activity but suppresses VP16 transactivation of a luciferase reporter gene in a dose-dependent manner. Furthermore, invasion requires signalling through the Ras-phosphoinositide 3-kinase pathway and Cdc42 or RhoA, but not Rac1. We show for the first time active nuclear import of an actin binding protein, and our findings point to a role for nuclear CapG in eliciting invasion, possibly through interfering with the cellular transcription machinery.

Critical role of N-cadherin in myofibroblast invasion and migration in vitro stimulated by colon-cancer-cell-derived TGF-beta or wounding

Invasion of stromal host cells, such as myofibroblasts, into the epithelial cancer compartment may precede epithelial cancer invasion into the stroma. We investigated how colon cancer-derived myofibroblasts invade extracellular matrices in vitro in the presence of colon cancer cells. Myofibroblast spheroids invade collagen type I in a stellate pattern to form a dendritic network of extensions upon co-culture with HCT-8/E11 colon cancer cells. Single myofibroblasts also invade Matrigel trade mark when stimulated by HCT-8/E11 colon cancer cells. The confrontation of cancer cells with extracellular matrices and myofibroblasts, showed that cancer-cell-derived transforming growth factor-beta (TGF-beta) is required and sufficient for invasion of myofibroblasts. In myofibroblasts, N-cadherin expressed at the tips of filopodia is upregulated by TGF-beta. Functional N-cadherin activity is implicated in TGF-beta stimulated invasion as evidenced by the neutralizing anti-N-cadherin monoclonal antibody (GC-4 mAb), and specific N-cadherin knock-down by short interference RNA (siRNA). TGF-beta1 stimulates Jun N-terminal kinase (also known as stress-activated protein kinase) (JNK) activity in myofibroblasts. Pharmacological inhibition of JNK alleviates TGF-beta stimulated invasion, N-cadherin expression and wound healing migration. Neutralization of N-cadherin activity by the GC-4 or by a 10-mer N-cadherin peptide or by siRNA reduces directional migration, filopodia formation, polarization and Golgi-complex reorientation during wound healing. Taken together, our study identifies a new mechanism in which cancer cells contribute to the coordination of invasion of stromal myofibroblasts.

Disruption of STAT3 signaling leads to tumor cell invasion through alterations of homotypic cell-cell adhesion complexes

STAT3 is frequently overexpressed and constitutively activated by tyrosine phosphorylation during malignant transformation. Despite the clear importance of STAT3 in cell proliferation and survival in diverse human cancers, its possible contribution to tumor cell adhesion, motility and invasion remains hypothetical. We therefore compared the transforming properties of STAT3wt, its constitutively activated dimeric form STAT3C, and the dominant negative mutant STAT3-Y705F in human colorectal HCT8/S11 cancer cells. Both STAT3wt and STAT3C exert a permissive action to the proinvasive activity of the scatter factor HGF in HCT8/S11 cells. In contrast, the monomeric and cytoplasmic mutant Y705F induces a constitutive invasive phenotype through Wnt/Rho-independent and EGFR/PI3-kinase-dependent pathways. Accordingly, Y705F decreases cell-cell homotypic adhesions, and increases cell motility and scattering, as well as lamellipodia-type cellular extensions. STAT3-Y705F-transfected HCT8/S11 cells display an increased tyrosine phosphorylation of the cell-cell adhesion regulator beta-catenin and its dissociation from the invasion suppressor E-cadherin at cell-cell contacts. Our data imply that both invasion promoter and repressor genes are controlled by the canonical STAT3 transcription pathways. Disruption of this cascade by Y705F reveals the proinvasive potential of altered forms of STAT3 as a persistent signaling adaptor in cytokine/transforming growth factor receptor scaffolds and oncogenic pathways.

Inhibition of proprotein convertases enhances cell migration and metastases development of human colon carcinoma cells in a rat model

Although proprotein convertases are involved in tumor development, nothing is known about their role in metastatic dissemination. To investigate the involvement of convertase inhibition, we used human colon carcinoma cells overexpressing alpha1-antitrypsin Portland (alpha1-PDX, PDX39P cells), a potent convertase inhibitor. We previously reported that these cells bear uncleaved integrin alpha subunits and display an altered attachment to vitronectin that is correlated with defects in the intracellular signaling pathways activated by alphavbeta5 integrin ligation. In this study, we demonstrate that the inhibition of proprotein convertase activity either by overexpression of alpha1-PDX or with the synthetic inhibitor decanoyl-Arg-Val-Lys-Arg-chloromethylketone (dec-RVKR-cmk) led to a significant increase in cell migration supported by the alphavbeta5 integrin. A collagen gel invasion assay showed that PDX39P cells also displayed an invasive ability, contrary to control cells. Moreover, when injected to immunosuppressed newborn rats, PDX39P cells were highly invasive, as they induce 10 times more metastases than mock-transfected cells. In addition, the aggressiveness of PDX39P cells can be greatly reduced by a function-blocking monoclonal antibody (mAb) against the alphav subunit. It thus seems that inhibition of proprotein convertases enhances the in vivo invasiveness of colon tumor cells likely due to an increase in cell migration mediated by alphav integrins.

Parabutoporin--an antibiotic peptide from scorpion venom--can both induce activation and inhibition of granulocyte cell functions

Parabutoporin (PP) affects motility and NADPH oxidase activity in normal human polymorphonuclear neutrophils and in granulocytic HL-60 cells. These PP-induced interactions utilize a Rac activation pathway. PP induces chemotaxis of neutrophils and HL-60 cells via a pertussis toxin-sensitive way, thus using trimeric G-proteins. The enhanced chemotaxis is also apparent in undifferentiated HL-60 cells which lack functional formyl peptide receptors. On the other hand, PP strongly reduces the superoxide production by the NADPH oxidase complex after either PMA or fMLP activation of granulocytes. These combined results strongly suggest a direct activation of G-proteins and subsequent Rac activation as the basis for the observed effects. The unexpected inhibitory effect of PP, despite Rac activation, on superoxide production in granulocytes is explained by the direct interaction of membrane localized PP which prevents the formation of a functional NADPH oxidase complex.

[Cyclooxygenase 2 and carcinogenesis]

The membrane glycoprotein Cox2 is regulated at transcriptional and post-transcriptional levels by pro-inflammatory agents, cytokines, growth factors, oncogenes, and tumor-promoters. Cox2 is expressed during early stages of colorectal carcinogenesis from the premalignant adenoma stage, and adenocarcinomas of stomach, colon, breast, lung and prostate. Its expression is detected in neoplastic, inflammatory, endothelial and stromal cells. Cox2 is involved in the conversion of arachidonic acid into prostaglandins and thromboxanes, as well as the synthesis of malonaldehyde (MDA, a mutagen) and the production of hydrogen peroxide, which promotes carcinogenesis. The Cox2 products act in turn on serpentine receptors coupled to heterotrimeric G-proteins (R-TXA2, R-PG) that are connected to signaling elements implicated in oncogenesis. Thus, Cox2 plays a key role in early stages of carcinogenesis by promoting the proliferation of tumoral cells and their resistance to apoptosis, as well as angiogenesis. tumor cell invasion and setting up of the metastatic process. These mechanisms establish the rationale behind the therapeutic targeting of Cox2 in human solid tumors.

Trefoil factor family (TFF) peptides and cancer progression

TFF peptides are involved in mucosal maintenance and repair through motogenic and antiapoptotic activities. These peptides are overexpressed during inflammatory processes and cancer progression. They also function as scatter factors, proinvasive and angiogenic agents. Such a divergence is related to the pathophysiological state of tissues submitted to persistent aggressive situations during digestive processes in the normal gastrointestinal tract, inflammatory and neoplastic diseases. In agreement with this model, TFF peptides are connected with multiple oncogenic pathways. As a consequence, the TFF signaling pathways may serve as potential targets in the control of chronic inflammation and progression of human solid tumors.

[Cyclooxygenase 2 and carcinogenesis]

The membrane glycoprotein Cox2 is regulated at transcriptional and post-transcriptional levels by pro-inflammatory agents, cytokines, growth factors, oncogenes, and tumor-promoters. Cox2 is expressed during early stages of colorectal carcinogenesis from the premalignant adenoma stage, and adenocarcinomas of stomach, colon, breast, lung and prostate. Its expression is detected in neoplastic, inflammatory, endothelial and stromal cells. Cox2 is involved in the conversion of arachidonic acid into prostaglandins and thromboxanes, as well as the synthesis of malonaldehyde (MDA, a mutagen) and the production of hydrogen peroxide, which promotes carcinogenesis. The Cox2 products act in turn on serpentine receptors coupled to heterotrimeric G-proteins (R-TXA2, R-PG) that are connected to signaling elements implicated in oncogenesis. Thus, Cox2 plays a key role in early stages of carcinogenesis by promoting the proliferation of tumoral cells and their resistance to apoptosis, as well as angiogenesis, tumor cell invasion and setting up of the metastatic process. These mechanisms establish the rationale behind the therapeutic targeting of Cox2 in human solid tumors.

Tenascin-C and SF/HGF produced by myofibroblasts in vitro provide convergent pro-invasive signals to human colon cancer cells through RhoA and Rac

Myofibroblasts are present at the invasion front in colon cancer. In an attempt to understand their putative proinvasive activity, we have developed an in vitro model. Myofibroblasts isolated from colon cancer tissue or obtained through transdifferentiation of colon fibroblasts by transforming growth factor (TGF)-beta stimulate invasion of colon cancer cells into collagen type I and Matrigel. We identified two convergent proinvasive agents secreted by myofibroblasts: namely scatter factor/hepatocyte growth factor (SF/HGF) and the TGF-beta-upregulated extracellular matrix glycoprotein tenascin-C (TNC), each of which is necessary though not sufficient for invasion. Myofibroblast-stimulated invasion into collagen type I is characterized by a change from a round, nonmigratory morphotype with high RhoA and low Rac activity to an elongated, migratory morphotype with low RhoA and high Rac activity. RhoA inactivation is determined by the epidermal growth factor (EGF)-like repeats of TNC through EGF-receptor signaling that confers a permissive and priming signal for the proinvasive activity of SF/HGF that activates Rac via c-Met. We confirmed the validity of this mechanism by using pharmacological modulators and dominant negative or constitutive active mutants that interfere with RhoA-Rho kinase and Rac signaling. Our in vitro results point to a new putative proinvasive signal for colon cancer cells provided by myofibroblasts in the tumor stroma.

YSK1 is activated by the Golgi matrix protein GM130 and plays a role in cell migration through its substrate 14-3-3zeta

The Golgi apparatus has long been suggested to be important for directing secretion to specific sites on the plasma membrane in response to extracellular signaling events. However, the mechanisms by which signaling events are coordinated with Golgi apparatus function remain poorly understood. Here, we identify a scaffolding function for the Golgi matrix protein GM130 that sheds light on how such signaling events may be regulated. We show that the mammalian Ste20 kinases YSK1 and MST4 target to the Golgi apparatus via the Golgi matrix protein GM130. In addition, GM130 binding activates these kinases by promoting autophosphorylation of a conserved threonine within the T-loop. Interference with YSK1 function perturbs perinuclear Golgi organization, cell migration, and invasion into type I collagen. A biochemical screen identifies 14-3-3zeta as a specific substrate for YSK1 that localizes to the Golgi apparatus, and potentially links YSK1 signaling at the Golgi apparatus with protein transport events, cell adhesion, and polarity complexes important for cell migration.

Alpha-catenin is required for IGF-I-induced cellular migration but not invasion in human colonic cancer cells

The mechanisms by which growth factors cooperate with cell adhesion molecules to modulate epithelial cell motility remain poorly understood. Here, we investigated the role of the E-cadherin/catenin complex in insulin-like growth factor (IGF-I)-dependent cell migration and invasion. We used variants of the HCT-8 colon cancer family that differ in their expression of alphaE-catenin, an intracellular molecule that links the E-cadherin/catenin complex to the actin cytoskeleton. Migration was determined using a monolayer wound model and cell invasion by the penetration of the cells into type-I collagen gels. We showed that alpha-catenin-deficient cells were not able to migrate in cohort upon IGF-I stimulation. Transfection of these cells with alpha-catenin isoforms (alphaN- or alphaT-catenin) restored migratory response IGF-I. These results suggest that alpha-catenins are involved in the signal issued from the E-cadherin/catenin complex to regulate IGF-I-stimulated migration. In contrast, IGF-I promoted invasion of both alpha-catenin-deficient and alpha-catenin-expressing cells, indicating that alpha-catenin did not participate in the regulation of IGF-I-induced invasion. Inhibition of E-cadherin function by treatment with MB-2 monoclonal antibodies inhibited both IGF-I-dependent cell migration and invasion. Taken together, our results indicate that functional alpha-catenin is essential for migration but not for invasion, while E-cadherin is involved in both phenomena.

Germinal tumor invasion and the role of the testicular stroma

Testicular germ cell tumors (TGCTs) are the most frequent neoplasia among young people and their incidence has grown very quickly during recent decades in North America and Europe. Many studies have been carried out in order to elucidate the factors involved in the appearance and progression of these tumors. Little is known about the role of cancer cell-stroma crosstalk in TGCT invasive processes. Here, we review several factors which may be implicated in germ cell tumor progression, such as matrix metalloproteinases, insulin-like growth factor, transforming growth factor beta, the cadherin/catenin complex and integrins. Paradoxically, some of these molecules are also involved in the regulation of normal testicular function. Finally, we discuss prospects for future research on the role of the stroma in the progression and differentiation of male germ cell tumors.

Synergistic cooperation between the AP-1 and LEF-1 transcription factors in activation of the matrilysin promoter by the src oncogene: implications in cellular invasion

The matrix metalloprotease matrilysin is expressed in premalignant polyps and plays a key role in local invasion during the progression of digestive tumors. In the present work, we investigated the possible relationships between the activity of the mouse and human matrilysin promoters (Mp), endogenous matrilysin protein expression, and two early oncogenetic defects frequently observed in human colonic cancers, namely activation of the src oncogene and impairment of the Wnt/APC/beta-catenin pathway. Using transient transfection assays, we report here that src signaling and the HMG-box transcription factor LEF-1 act synergistically with the proximal (-61 to -67) AP-1 binding site to transactivate the Mp in premalignant and tumorigenic kidney and colonic epithelial cells, through beta-catenin- and axin-independent signaling pathways. This synergism involves the -109 and -194 Tcf/LEF-1 binding sites in the Mp and a physical interaction between LEF-1 and c-Jun. Furthermore, src coordinates accumulation of the c-Jun factor and matrilysin transcripts. Conversely, the c-Jun dominant negative mutant TAM67 and the src tyrosine kinase inhibitor M475271 impaired src-induced Mp activation, matrilysin protein accumulation, and invasion of type I collagen gels. This mechanism may thereby contribute to cellular invasion during the early-stage adenoma/adenocarcinoma conversion and the metastatic process of digestive tumors.

Upregulation of MMPs by soluble E-cadherin in human lung tumor cells

Loss of E-cadherin/catenin mediated cell-cell adhesion and overexpression of matrix metalloproteinases (MMPs) are largely involved in tumor invasion. It has been recently shown that high levels of a soluble 80 kDa fragment of E-cadherin, resulting from a cleavage by MMPs, are found in serum and in urine from cancer patients. Additionally, this soluble E-cadherin (sE-CAD) promotes cell invasion into chick heart and into collagen type I gels. The aim of our study was to examine the mechanism of sE-CAD-induced cell invasion. Since MMPs play a crucial role in invasion, we looked for induction of MMPs by sE-CAD in noninvasive human lung tumor cells 16HBE. An induction of MMP-2, MMP-9 and MT1-MMP expression was observed both at the mRNA and at the protein level in the presence of sE-CAD (in conditioned medium form or in E-cadherin HAV peptide form). No induction of MMP-1, -3 and -7 or variation of the levels of their inhibitors, TIMP-1 and TIMP-2, were detected. The biologic relevance of the sE-CAD-induced MMP upregulation was tested by demonstrating that sE-CAD promotes in vitro cell invasion in a modified Boyden chamber assay. These data provide new insight into mechanisms of tumor invasion by ectodomain shedding of the cell-cell adhesion molecule E-cadherin.

Selective abrogation of the proinvasive activity of the trefoil peptides pS2 and spasmolytic polypeptide by disruption of the EGF receptor signaling pathways in kidney and colonic cancer cells

Trefoil peptides (TFFs) are now considered as scatter factors, proinvasive and angiogenic agents acting through cyclooxygenase-2 (COX-2)- and thromboxane A2 receptor (TXA2-R)-dependent signaling pathways. As expression and activation levels of the epidermal growth factor receptor (EGFR) predict the metastatic potential of human colorectal cancers, the purpose of this study was to establish whether the EGF receptor tyrosine kinase (EGFR-TK) contributes to cellular invasion induced by TFFs in kidney and colonic cancer cells. Both the dominant negative form of the EGFR (HER-CD533) and the EGFR-TK inhibitor ZD1839 (Iressa) abrogated cellular invasion induced by pS2, spasmolytic polypeptide (SP) and the src oncogene, but not by ITF and the TXA2-R. Similarly, EGFR-TK inhibition by ZD1839 reversed the invasive phenotype promoted by the constitutively activated form of the EGFR (EGFRvIII) and the EGFR agonists transforming growth factor alpha (TGFalpha), amphiregulin and EGF. We also provide evidence that TFFs, EGFRvIII, and TGFalpha trigger common proinvasive pathways using the PI3'-kinase and Rho/Rho- kinase cascades. These findings identify the EGFR-TK as a key signaling element for pS2- and SP-mediated cellular invasion. It is concluded that although pS2, SP and ITF belong to the same family of inflammation- and cancer-associated regulatory peptides, they do not control identical signaling networks.

The Nucleo-cytoplasmic actin-binding protein CapG lacks a nuclear export sequence present in structurally related proteins

Despite thorough structure-function analyses, it remains unclear how CapG, a ubiquitous F-actin barbed end capping protein that controls actin microfilament turnover in cells, is able to reside in the nucleus and cytoplasm, whereas structurally related actin-binding proteins are predominantly cytoplasmic. Here we report the molecular basis for the different subcellular localization of CapG, severin, and fragminP. Green fluorescent protein-tagged fragminP and severin accumulate in the nucleus upon treatment of transfected cells with the CRM1 inhibitor leptomycin B. We identified a nuclear export sequence in severin and fragminP, which is absent in CapG. Deletion of amino acids Met(1)-Leu(27) resulted in nuclear accumulation of severin and fragminP. Tagging this sequence to CapG triggered nuclear export, whereas mutation of single leucine residues (Leu(17), Leu(21), and Leu(27)) in the export sequence inhibited nuclear export. Based on these findings, a nuclear export signal was identified in myopodin, a muscle-specific actin-binding protein, and the Bloom syndrome protein, a RecQ-like helicase. Deletion of the myopodin nuclear export sequence blocked invasion into collagen type I of C2C12 cells transiently overexpressing myopodin. Our findings explain regulated subcellular targeting of distinct classes of actin-binding proteins.

Requirement of both mucins and proteoglycans in cell-cell dissociation and invasiveness of colon carcinoma HT-29 cells

Human colon carcinomas are characterized by an aberrant expression of mucins, which in some case leads to an abundant presence of mucus such as in mucinous and signet ring cell carcinomas. Cellular cloning of the human colon carcinoma cell line HT-29 (HT-29 STD), which is mainly composed of undifferentiated cells, yielded a highly mucin-secreting variant (HT-29 5M21). The latter cloned cells cultured on plastic display a polarized organization with an apical secretion of MUC5AC mucin (Lesuffleur et al., Int J Cancer 1998;76:383-92.). Our aim was to study these 2 cell-types as for the invasive and adhesive properties with regard to the function of E-cadherin. HT-29 STD cells were noninvasive in collagen type I, whereas HT-29 5M21 cells were invasive, and the latter behavior was connected to a loss of function of E-cadherin. Likewise, HT-29 5M21 cells were characterized by a cell-cell adhesion independent of E-cadherin, in contrast to the E-cadherin dependent cell-cell adhesion of HT-29 STD cells. Immunofluorescence of HT-29 5M21 cells cultured on collagen type I showed the disappearance of the polarized organization, with a redistribution of apical mucins to the entire cell surface. Treatment of HT-29 5M21 cells by 1-benzyl-2-acetamido-2-deoxy-alpha-D-galactopyranoside (GalNAcalpha-O-bn) or by beta-D-xyloside revealed that both mucins and proteoglycans were involved in the loss of E-cadherin function. The use of specific antibodies allowed to show that MUC5AC, MUC1 and heparan sulfate proteoglycans cooperated in the formation of a biological inhibitory complex towards the function of E-cadherin in this invasive HT-29 clone.

Invasion of retinal pigment epithelial cells: N-cadherin, hepatocyte growth factor, and focal adhesion kinase

PURPOSE

To investigate the role of N-cadherin and hepatocyte growth factor (HGF) in the invasion of collagen type I by human retinal pigment epithelial (RPE) cells.

METHODS

RPE sheets from eight human eyes were used for characterization through Western blot analysis of the expression of cadherin in total lysates or after immunoprecipitation with anti beta-catenin antibody. First-passage primary cultures of RPE sheets were successfully established from 28 of 56 human eyes. First-passage primary RPE cell cultures on glass substrate, consisting of patches of cells, were used for immunocytochemistry. Fifteen first-passage primary RPE cell cultures in culture vessels were grown to confluence. Four of the 15 first-passage primary RPE cell cultures were investigated for cadherin expression by immunocytochemistry, and the other 11 were further subcultured for two to six passages. These 11 cultures were used for functional assays and investigated for expression of cadherin at regular time intervals. Cells from passage-3 to -4 primary RPE cell cultures were tested for invasion into collagen type I gels, with or without neutralizing antibodies for HGF and N-cadherin, respectively. Activation of the c-Met receptor for HGF and of focal adhesion kinase (FAK) was investigated by immunoprecipitation with anti-phosphotyrosine antibody, gel electrophoresis, and immunostaining on Western blot. Levels of HGF in conditioned medium (CM) of RPE cells were determined by ELISA.

RESULTS

RPE cells in culture displayed two phenotypes: Both fibroblast-like and epithelioid cells were present in all 15 first-passage primary cultures and in further passaged cultures derived therefrom. When seeded on collagen, all RPE cells acquired a fibroblast-like phenotype and invaded the collagen type I gel. RPE cells also stimulated branching morphogenesis of MDCK/AZ epithelial canine kidney cell colonies inside collagen. HGF was found in RPE CM, suggesting an autocrine loop for invasion through its c-Met receptor. HGF-neutralizing antibody inhibited invasion of collagen. The major cadherin expressed by RPE cells in culture was N(euronal)-cadherin. Invasion of collagen by RPE cells was also inhibited by an N-cadherin-neutralizing antibody. N-cadherin and c-Met coimmunoprecipitated in RPE cells. FAK and c-Met were both phosphorylated in RPE cells in culture, and phosphorylation was inhibited by antibodies neutralizing either N-cadherin or HGF.

CONCLUSIONS

The present investigation provides evidence for an autocrine HGF/c-Met loop that stimulates RPE cell invasion into collagen through FAK. The invasion-stimulatory molecule N-cadherin also activates FAK in invasive RPE cells.

Trefoil peptides as proangiogenic factors in vivo and in vitro: implication of cyclooxygenase-2 and EGF receptor signaling

We previously established that the trefoil peptides (TFFs) pS2, spasmolytic polypeptide, and intestinal trefoil factor are involved in cellular scattering and invasion in kidney and colonic cancer cells. Using the chorioallantoic membrane (CAM) assay and the formation of tube-like structures by human umbilical vein endothelial cells (HUVEC) plated on the Matrigel matrix substratum, we report here that TFFs are proangiogenic factors. Angiogenic activity of TFFs is comparable to that induced by vascular endothelial growth factor, leptin, and transforming growth factor-alpha. Stimulation of angiogenesis by pS2 in the CAM assay is blocked by pharmacological inhibitors of cyclooxygenase COX-2 (NS-398) and epidermal growth factor receptor (EGF-R) tyrosine kinase (ZD1839), but is independent of KDR/Flk-1 and thromboxane A2 receptors. In contrast, the morphogenic switch induced by pS2 in HUVEC cells could be inhibited by the specific KDR heptapeptide antagonist ATWLPPR and by inhibitors of COX-2 and EGF-R signaling. These results implicate TFFs in the formation of new blood vessels during normal and pathophysiological processes linked to wound healing, inflammation, and cancer progression in the digestive mucosa and other human solid tumors associated with aberrant expression of TFFs.

Gelsolin-induced epithelial cell invasion is dependent on Ras-Rac signaling

Gelsolin is a widely distributed actin binding protein involved in controlling cell morphology, motility, signaling and apoptosis. The role of gelsolin in tumor progression, however, remains poorly understood. Here we show that expression of green fluorescent protein (GFP)-tagged gelsolin in MDCK-AZ, MDCKtsSrc or HEK293T cells promotes invasion into collagen type I. In organ culture assays, MDCK cells expressing gelsolin-GFP invaded pre-cultured chick heart fragments. Gelsolin expression inhibited E-cadherin-mediated cell aggregation but did not disrupt the E-cadherin-catenin complex. Co-expression of dominant-negative Rac1N17, but not RhoAN19 or Cdc42N17, counteracted gelsolin-induced invasion, suggesting a requirement for Rac1 activity. Increased ARF6, PLD or PIP5K 1alpha activity canceled out gelsolin-induced invasion. Furthermore, we found that invasion induced by gelsolin is dependent on Ras activity, acting through the PI3K-Rac pathway via the Ras guanine nucleotide exchange factor Sos-1. These findings establish a connection between gelsolin and the Ras oncogenic signaling pathway.

The c-kit tyrosine kinase inhibitor STI571 for colorectal cancer therapy

The c-kit tyrosine kinase inhibitor STI571 exhibits a substantial therapeutic activity in patients with chronic myeloid leukemia and gastrointestinal stromal tumors respectively associated with constitutive activation of the BCR-ABL and c-kit tyrosine kinases. Human colorectal tumors also express the c-kit proto-oncogene. The present study focuses on the anticancer activity of STI571 in human colorectal tumor cells in vitro and in vivo. The c-kit receptor was identified as a M(r) 145,000 immunoreactive band in human colon cancer cells HT29, HCT8/S11, and HCT116. Cellular invasion induced by 10 ng/ml stem cell factor (EC(50) = 3 ng/ml) in HT29 cells was blocked by 1 micro M STI571 (IC(50) = 56 nM) and pharmacological inhibitors of several oncogenic signaling pathways, namely, phosphatidylinositol 3-kinase (LY294002), Rho GTPases (Clostridium botulinum exoenzyme C3 transferase), and Rho-kinase (Y27632). STI571 inhibited HT29 cell proliferation (IC(50) = 6 micro M) and induced apoptosis in vitro. These cellular effects were associated with a decrease in tumor growth. We also demonstrated that stem cell factor is a proangiogenic factor in vivo and in vitro. These encouraging results warrant further preclinical investigations and clinical trials on the use of the c-kit inhibitor STI571 as a chemotherapeutic agent in colon cancer prevention and in treatment of advanced colorectal cancers associated with liver metastases.

Gastrin significantly modifies the migratory abilities of experimental glioma cells

Malignant astrocytic tumors are characterized by the pronounced and diffuse migration of tumor astrocytes into the brain parenchyma. The present study shows that gastrin is a brain neuropeptide that is able to significantly modulate astrocytic tumor migration at both invasion and motility levels. In the matter of invasion, gastrin severely reduces the in vitro invasive abilities of C6 rat glioma, 9L rat gliosarcoma, and U373 human glioma cells in a collagen matrix. In vitro, gastrin also markedly modifies the motility features in both C6 and U373 cells, at least partly through a decrease in the expression of the RhoA small GTPase, and so brings about some dramatic modifications to the organization in the actin cytoskeleton. The in vitro preincubation of C6 tumor cells with gastrin significantly increases the life spans of rats stereotactically implanted with these cells as compared with the survival periods of rats implanted with gastrin-untreated C6 cells. As suggested by our in vitro experiments, these effects, observed in vivo cannot relate to only the gastrin-induced decrease in tumor astrocyte migratory abilities. Indeed, gastrin also induces immunomodulatory effects, because we observed a marked gastrin-induced recruitment of lymphocytes into C6 gliomas and 9L gliosarcomas. These data all suggest that gastrin can act as an endogenous modulator of glioma progression.

G-protein alpha(olf) subunit promotes cellular invasion, survival, and neuroendocrine differentiation in digestive and urogenital epithelial cells

The heterotrimeric G-protein subunits Galpha and Gbetagamma are involved in cellular transformation and tumor development. Here, we report the expression of Galpha(olf) in human digestive and urogenital epithelial cells using RT-PCR and Western blot. When the constitutively activated form of Galpha(olf)Q214L (AGalpha(olf)) was stably transfected in canine kidney MDCKts.src and human colonic HCT-8/S11 epithelial cells, it induced cellular invasion in collagen gels. AGalpha(olf)-mediated invasion was abrogated by agonists of platelet activating factor receptors (PAF-R) and protease-activated receptors -1 (PAR-1), pharmacological inhibitors of PI3'-Kinase (wortmannin), protein kinase C (Gö6976 and GF109203X), Rho GTPase (C3T exoenzyme), but was independent of protein kinase A. Accordingly, the invasive phenotype induced by AGalpha(olf) in HCT-8/S11 cells was reversed by the RhoA antagonist RhoD (G26V). Although AGalpha(olf) protected MDCKts.src cells against serum starvation-mediated apoptosis via a Rho-independent pathway, both AGalpha(olf) and Rho inhibition by C3T induced neuroendocrine-like differentiation linked to extensive neurite outgrowth and parathyroid hormone-related protein expression in human prostatic LNCaP-AGalpha(olf) cells. Since prostate tumors with a larger neuroendocrine cell population display increased invasiveness, persistent activation of the G-protein alpha(olf) may exert convergent adverse effects on cellular invasion and survival in solid tumors during the neoplastic progression towards metastasis. doi:10.1038/sj.onc.1205498

RhoA- and RhoD-dependent regulatory switch of Galpha subunit signaling by PAR-1 receptors in cellular invasion

Thrombin and proteinase-activated receptors (PAR) specifically regulate several functions that markedly enhance the transformation phenotype such as inflammation, cell proliferation, tumor growth, and metastasis. We recently reported that thrombin inhibits cellular invasion induced by src, hepatocyte growth factor (HGF), and leptin in kidney and colonic epithelial cells via predominant activation of the pertussis toxin (PTx) -sensitive G-proteins Galphao/Galphai. We provide pharmacological and biochemical evidence that in the presence of PTx, PAR-1 induced cellular invasion through Galpha12/Galpha13- and RhoA/Rho kinase (ROCK) -dependent signaling. However, inhibition of the endogenous small GTPase RhoA by the C3 exoenzyme, dominant-negative N19-RhoA, activated G26V-RhoD, and activators of the nitric oxide/cGMP pathways conferred invasive activity to PAR-1 via a signaling cascade using Galphaq, phospholipase C (PLC), Ca(2+)/calmodulin myosin light chain kinase (CaM-MLCK), and phosphorylation of MLC. We found that cellular invasion induced by the src oncogene is abrogated by inhibitors of the RhoA/ROCK pathway and is independent of PLC/CaM-MLCK signaling. Our data demonstrate that the RhoA and RhoD small GTPases are acting as a molecular switch of cellular invasion and reveal a novel critical mechanism by which PAR-1 bypass Galphao/i and RhoA inhibition via differential coupling to heterotrimeric G-proteins linked to divergent or convergent biological responses. Our data also indicate that Rho GTPases and ROCK mediate a src-dependent invasion signal in kidney and colonic cancer cells. We conclude that dynamic regulation of Rho GTPases activation and inactivation by oncogenes, growth factors, cGMP-inducing agents, and adhesion molecules can initiate convergent invasion signals controlled by the thrombin PAR-1 in cancer cells.-Nguyen, Q.-D., Faivre, S., Bruyneel, E., Rivat, C., Seto, M., Endo, T., Mareel, M., Emami, S., Gespach, C. RhoA- and RhoD-dependent regulatory switch of Galpha subunit signaling by PAR-1 receptors in cellular invasion.