3688

ITGB1

Reduced epithelial cadherin (E-cad) is a hallmark of invasive carcinomas that have acquired epithelial-mesenchymal transition (EMT) phenotypes. Here we show that down-regulated E-cad expression induced by transforming growth factor-beta (TGF-beta) and EMT preceded breast cancer outgrowth in three-dimensional (3D) organotypic assays and in the lungs of mice. Pharmacological inhibitors against focal adhesion kinase prevented metastatic outgrowth of newly seeded organoids, but not that of their fully established counterparts. Interrogating the D2-HAN (hyperplastic alveolar nodule) model of breast cancer dormancy and metastasis showed that dormant D2.OR cells produced branched organoid morphologies in 3D-cultures, and expressed robust quantities of E-cad that was uncoupled from regulation by TGF-beta. In contrast, metastatic D2.A1 organoids were spherical and wholly lacked E-cad expression. Interestingly, D2.A1 cells engineered to re-express E-cad formed branched organoids, down-regulated beta1 integrin expression, and failed to undergo metastatic outgrowth. The tumor-suppressing function of E-cad was inactivated by increased microenvironmental rigidity, and was not recapitulated by expression of an E-cad mutant lacking its extracellular domain. Twist expression, but not that of Snail, reinitiated metastatic outgrowth in dormant D2.OR cells. Our findings show that EMT and its down-regulated expression of E-cad circumvent breast cancer dormancy in part by facilitating beta1 integrin expression necessary for metastatic outgrowth.

We have previously shown that integrinbeta1 associates with gefitinib resistance. As epithelial-mesenchymal transition (EMT) also induces gefitinib resistance in vitro, we wished to determine the relation of them in gefitinib resistance. In this study, we show that integrinbeta1 induced epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) resistance in xenograft tumors and gefitinib-resistant NSCLC tumors acquired EMT phenotype. Furthermore, inhibition of integrinbeta1 reverses EMT, meanwhile overexpression and activation of integrinbeta1 aggravates EMT. Lastly, we further identified that integrinbeta1 enhanced EMT via FAK-AKT signaling pathway. These findings highlight a novel relation of integrinbeta1 and EMT in EGFR TKI resistant NSCLC.

Prognosis for oral cancer patients has not improved in over 60 years due to invasion and recurrence. To understand the invasive behavior of this tumor, we evaluated the role of the alphavbeta6 integrin. Invasive oral SCC cells express the alphavbeta6 integrin, which contains an 11-amino-acid extension on its beta-subunit unique to the integrin family. We determined that this beta6 cytoplasmic extension regulates the composition of the intermediate filament network and the organization of signaling structures called focal contacts. The auto-phosphorylation of FAK, which is localized to focal contacts, was also regulated by the beta6-cytoplasmic tail, as were the transcription factors Notch and STAT3. Lastly, we also determined that activation of MAPK required the full-length beta6 integrin. Together these results indicate that the signaling critical to epithelial-to-mesenchymal transition (EMT) is regulated by the beta6 integrin cytoplasmic domain.

Human ovarian cancer is diagnosed in the late, metastatic stages but the underlying mechanisms remain poorly understood. We report a surprising functional link between CD151-alpha3beta1 integrin complexes and the malignancy of serous-type ovarian cancer. Analyses of clinical specimens indicate that CD151 expression is significantly reduced or diminished in 90% of metastatic lesions, while it remains detectable in 58% of primary tumors. These observations suggest a putative tumor-suppressing role of CD151 in ovarian cancer. Indeed, our analyses show that knocking down CD151 or alpha3 integrin enhances tumor cell proliferation, growth and ascites production in nude mice. These changes are accompanied by impaired cell-cell contacts and aberrant expression of E-cadherin, Mucin 5AC and fibronectin, largely reminiscent of an epithelial to mesenchymal transition (EMT)-like change. Importantly, Slug, a master regulator of EMT, is markedly elevated. Knocking down Slug partially restores CD151-alpha3beta1 integrin complex-dependent suppression of cell proliferation. Moreover, disruption of these adhesion protein complexes is accompanied by a concomitant activation of canonical Wnt signaling, including elevated levels of beta-catenin and Axin-2 as well as resistance to the inhibition in beta-catenin-dependent transcriptional complexes. Together, our study demonstrates that CD151-alpha3beta1 integrin complexes regulate ovarian tumor growth by repressing Slug-mediated EMT and Wnt signaling.

Integrins have been known to play pivotal roles in malignant progression and epithelial-mesenchymal transition (EMT) of non-small cell lung cancer (NSCLC). We previously demonstrated that MARVELD1, a potential tumor suppressor, is epigenetically silenced in multiple cancer cells. In this study, we found MARVELD1 silencing altered cell surface ultrastructure of NSCLC cells and inhibited the formation of punctate integrin beta1/beta4 cluster in microvillus, whereas MARVELD1 overexpression suppressed TGF-beta1-induced EMT. Remarkably, the balance of integrin beta1 and beta4 was modulated by MARVELD1. MARVELD1 silencing led to imbalance of integrin beta1/beta4 and significantly reduced microvillus length, furthermore affected the localization of beta1/beta4 at microvilli tips. TGF-beta1-induced EMT was promoted by MARVELD1 silencing, while rebalance of integrin beta1/beta4 partly rescued the epithelial phenotype of MARVELD1-silenced cells. Mechanistically, we demonstrate that MARVELD1-mediated balance of integrin beta1 and beta4 regulates cell surface ultrastructure and EMT phenotype of NSCLC cells, suggesting MARVELD1 has a potential to be developed as a therapeutic target for NSCLC. (c) 2015 Wiley Periodicals, Inc.CI - (c) 2015 Wiley Periodicals, Inc.

Twist, a highly conserved basic Helix-Loop-Helix transcription factor, functions as a major regulator of epithelial-mesenchymal transition (EMT) and tumor metastasis. In different cell models, signaling pathways such as TGF-beta, MAPK/ERK, WNT, AKT, JAK/STAT, Notch, and P53 have also been shown to play key roles in the EMT process, yet little is known about the signaling pathways regulated by Twist in tumor cells. Using iTRAQ-labeling combined with 2D LC-MS/MS analysis, we identified 194 proteins with significant changes of expression in MCF10A-Twist cells. These proteins reportedly play roles in EMT, cell junction organization, cell adhesion, and cell migration and invasion. ECM-receptor interaction, MAPK, PI3K/AKT, P53 and WNT signaling were found to be aberrantly activated in MCF10A-Twist cells. Ingenuity pathways Analysis showed that integrin beta1 (ITGB1) acts as a core regulator in linking integrin-linked kinase (ILK), Focal-adhesion kinase (FAK), MAPK/ERK, PI3K/AKT, and WNT signaling. Increased Twist and ITGB1 are associated with breast tumor progression. Twist transcriptionally regulates ITGB1 expression. Over-expression of ITGB1 or Twist in MCF10A led to EMT, activation of FAK/ILK, MAPK/ERK, PI3K/AKT, and WNT signaling. Knockdown of Twist or ITGB1 in BT549 and Hs578T cells decreased activity of FAK, ILK, and their downstream signaling, thus specifically impeding EMT and cell invasion. Knocking down ILK or inhibiting FAK, MAPK/ERK, or PI3K/AKT signaling also suppressed Twist-driven EMT and cell invasion. Thus, the Twist-ITGB1-FAK/ILK pathway and their downstream signaling network dictate the Twist-induced EMT process in human mammary epithelial cells and breast cancer cells.CI - Copyright (c) 2015 Elsevier Ltd. All rights reserved.