Bakin AV, Tomlinson AK, Bhowmick NA, Moses HL, Arteaga CL.. Phosphatidylinositol 3-kinase function is required for TGFbeta-mediated epithelial to mesenchymal transition and cell migration. J Biol Chem 275: 36803-36810
Division of Hematology and Oncology, Vanderbilt University, Нашвилл, Michigan, United States Journal of Biological Chemistry
(Impact Factor: 4.57).
12/2000; 275(47):36803-10. DOI: 10.1074/jbc.M005912200
We have studied the role of phosphatidylinositol 3-OH kinase (PI3K)-Akt signaling in transforming growth factor beta (TGFbeta)-mediated epithelial to mesenchymal transition (EMT). In NMuMG mammary epithelial cells, exogenous TGFbeta1 induced phosphorylation of Akt at Ser-473 and Akt in vitro kinase activity against GSK-3beta within 30 min. These responses were temporally correlated with delocalization of E-cadherin, ZO-1, and integrin beta(1) from cell junctions and the acquisition of spindle cell morphology. LY294002, an inhibitor of the p110 catalytic subunit of PI3K, and a dominant-negative mutant of Akt blocked the delocalization of ZO-1 induced by TGFbeta1, whereas transfection of constitutively active p110 induced loss of ZO-1 from tight junctions. In addition, LY294002 blocked TGFbeta-mediated C-terminal phosphorylation of Smad2. Consistent with these data, TGFbeta-induced p3TP-Lux and p(CAGA)(12)-Lux reporter activities were inhibited by LY294002 and transiently expressed dominant-negative p85 and Akt mutants in NMuMG and 4T1 cells. Dominant-negative RhoA inhibited TGFbeta-induced phosphorylation of Akt at Ser-473, whereas constitutively active RhoA increased the basal phosphorylation of Akt, suggesting that RhoA in involved in TGFbeta-induced EMT. Finally, LY294002 and neutralizing TGFbeta1 antibodies inhibited ligand-independent constitutively active Akt as well as basal and TGFbeta-stimulated migration in 4T1 and EMT6 breast tumor cells. Taken together, these data suggest that PI3K-Akt signaling is required for TGFbeta-induced transcriptional responses, EMT, and cell migration.
Available from: Panagiotis Papageorgis
- "Furthermore, the PI3K/Akt pathway has been implicated in mediating some of cellular functions of TGFí µí»½. Studies have shown that TGFí µí»½ can rapidly induce PI3K activation followed by phosphorylation of its effector Akt to promote EMT, cell migration, and survival  . Mechanistically, the p85 regulatory subunit of PI3K appears to be constitutively bound to the TGFí µí»½RII and, upon TGFí µí»½ stimulation, TGFí µí»½RI is recruited to the complex to activate PI3K and initiate downstream signaling . "
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ABSTRACT: Retaining the delicate balance in cell signaling activity is a prerequisite for the maintenance of physiological tissue homeostasis. Transforming growth factor-beta (TGFβ) signaling is an essential pathway that plays crucial roles during embryonic development as well as in adult tissues. Aberrant TGFβ signaling activity regulates tumor progression in a cancer cell-autonomous or non-cell-autonomous fashion and these effects may be tumor suppressing or tumor promoting depending on the cellular context. The fundamental role of this pathway in promoting cancer progression in multiple stages of the metastatic process, including epithelial-to-mesenchymal transition (EMT), is also becoming increasingly clear. In this review, we discuss the latest advances in the effort to unravel the inherent complexity of TGFβ signaling and its role in cancer progression and metastasis. These findings provide important insights into designing personalized therapeutic strategies against advanced cancers.
Available from: Amir Kedan
- " Whyte et al . , 2009 ; Pal and Mandal , 2012 ) . Furthermore , the PI3K / AKT pathway is abnormally activated in about 30% of breast cancer patients ( Cancer Genome Atlas Network , 2012 ) , and is required for EMT . Specific inhibitors of the PI3K / AKT pathway , dominant - negative AKT or a Myr - AKT mutant markedly affect EMT in mammary cells ( Bakin et al . , 2000 ; Grille et al . , 2003 ) . We show here that Myr - AKT can rescue the effects of Nir2 depletion on the expression of vimentin and CD44 ( Fig . 4 ) , two characteristic EMT markers , thus demonstrting the central role of AKT activation in Nir2 - mediated EMT effects . Interestingly , previous studies have shown that CD44s also enhances "
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ABSTRACT: The involvement of Epithelial-mesenchymal transition (EMT) in breast cancer metastasis has been demonstrated by many studies. However, the intracellular proteins and signaling pathways that regulate EMT have not been fully identified. Here we show that the lipid-transfer protein Nir2 enhances EMT in mammary epithelial and breast cancer cells. Nir2 overexpression induces down-regulation of epithelial markers and concomitant up-regulation of mesenchymal markers, while silencing of Nir2 by shRNA has opposite effects. Additionally, Nir2 expression is increased during EMT and affects cell morphology, while Nir2 depletion attenuates growth factor-induced cell migration. These effects of Nir2 on EMT-associated processes are mainly mediated through the PI3K/AKT and the ERK1/2 pathways. Nir2 depletion also inhibits cell invasion in vitro and lung metastasis in animal models. Immunohistochemical analysis of breast cancer tissue samples reveals a correlation between high Nir2 expression and tumor grade, and Kaplan-Meier survival curves correlate Nir2 expression with poor disease outcome. These results suggest that Nir2 not only enhances EMT in vitro and breast cancer metastasis in animal models, but also contributes to breast cancer progression in human patients.
Available from: sciencedirect.com
- "The TGFβ type I receptor also provides non-Smad signals, as for example, upon recruitment of the ubiquitin ligase TRAF6, activation of proteases leads to cleavage of the receptor and translocation of the cytoplasmic kinase domain of this receptor to the nucleus, where it binds to chromatin and together with the transcriptional co-activator p300 induces the expression of EMT-TFs like Snail . In addition, studies in NMuMG cells and in breast cancer cell lines have linked the TGFβ type I receptor with downstream activation of many key signaling enzymes that provide essential signals towards EMT, and include the phosphatidylinositol 3′ kinase (PI3K)/AKT kinase pair , the Src tyrosine kinase and the mitogen activated protein kinase (MAPK) p38  , the focal adhesion kinase (FAK) whose signaling is coupled to activation of the integrin-β1  , the Rho family of small GTPases , and more . A prominent and more recent pathway that mediates EMT signals downstream of TGFβ is the mammalian target of rapamycin (mTOR) kinase pathway, which is directly coupled to the PI3K . "
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The progression of cancer through stages that guide a benign hyperplastic epithelial tissue towards a fully malignant and metastatic carcinoma, is driven by genetic and microenvironmental factors that remodel the tissue architecture. The concept of epithelial-mesenchymal transition (EMT) has evolved to emphasize the importance of plastic changes in tissue architecture, and the cross-communication of tumor cells with various cells in the stroma and with specific molecules in the extracellular matrix (ECM).
Scope of the review
Among the multitude of ECM-embedded cytokines and the regulatory potential of ECM molecules, this article focuses on the cytokine transforming growth factor β (TGFβ) and the glycosaminoglycan hyaluronan, and their roles in cancer biology and EMT. For brevity, we concentrate our effort on breast cancer.
Both normal and abnormal TGFβ signaling can be detected in carcinoma and stromal cells, and TGFβ-induced EMT requires the expression of hyaluronan synthase 2 (HAS2). Correspondingly, hyaluronan is a major constituent of tumor ECM and aberrant levels of both hyaluronan and TGFβ are thought to promote a wounding reaction to the local tissue homeostasis. The link between EMT and metastasis also involves the mesenchymal-epithelial transition (MET). ECM components, signaling networks, regulatory non-coding RNAs and epigenetic mechanisms form the network of regulation during EMT-MET.
Understanding the mechanism that control epithelial plasticity in the mammary gland promises the development of valuable biomarkers for the prognosis of breast cancer progression and even provides new ideas for a more integrative therapeutic approach against disease. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.
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