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Transforming growth factor-beta1 mediates epithelial to mesenchymal transdifferentiation through a RhoA-dependent mechanism.

ABSTRACT: Transforming growth factor-beta1 (TGF-beta) can be tumor suppressive, but it can also enhance tumor progression by stimulating the complex process of epithelial-to-mesenchymal transdifferentiaion (EMT). The signaling pathway(s) that regulate EMT in response to TGF-beta are not well understood. We demonstrate the acquisition of a fibroblastoid morphology, increased N-cadherin expression, loss of junctional E-cadherin localization, and increased cellular motility as markers for TGF-beta-induced EMT. The expression of a dominant-negative Smad3 or the expression of Smad7 to levels that block growth inhibition and transcriptional responses to TGF-beta do not inhibit mesenchymal differentiation of mammary epithelial cells. In contrast, we show that TGF-beta rapidly activates RhoA in epithelial cells, and that blocking RhoA or its downstream target p160(ROCK), by the expression of dominant-negative mutants, inhibited TGF-beta-mediated EMT. The data suggest that TGF-beta rapidly activates RhoA-dependent signaling pathways to induce stress fiber formation and mesenchymal characteristics.

SUBMITTER: Bhowmick NA

PROVIDER: S-EPMC30565 | biostudies-literature | 2001 Jan

REPOSITORIES: biostudies-literature

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Transforming growth factor-beta1 mediates epithelial to mesenchymal transdifferentiation through a RhoA-dependent mechanism.

Bhowmick N A NA Ghiassi M M Bakin A A Aakre M M Lundquist C A CA Engel M E ME Arteaga C L CL Moses H L HL

Molecular biology of the cell 20010101 1

Transforming growth factor-beta1 (TGF-beta) can be tumor suppressive, but it can also enhance tumor progression by stimulating the complex process of epithelial-to-mesenchymal transdifferentiaion (EMT). The signaling pathway(s) that regulate EMT in response to TGF-beta are not well understood. We demonstrate the acquisition of a fibroblastoid morphology, increased N-cadherin expression, loss of junctional E-cadherin localization, and increased cellular motility as markers for TGF-beta-induced EM ...[more]

PMID: 11160820

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Project description:Transforming growth factor-? (TGF-?) and epidermal growth factor (EGF) have critical roles in regulating the metastasis of aggressive breast cancers, yet the impact of epithelial-mesenchymal transition (EMT) induced by TGF-? in altering the response of breast cancer cells to EGF remains unknown. We show in this study that murine metastatic 4T1 breast cancer cells formed compact and dense spheroids when cultured under three-dimensional (3D) conditions, which was in sharp contrast to the branching phenotypes exhibited by their nonmetastatic counterparts. Using the human MCF10A series, we show that epithelial-type and nonmetastatic breast cancer cells were unable to invade to EGF, whereas their mesenchymal-type and metastatic counterparts readily invaded to EGF. Furthermore, EMT induced by TGF-? was sufficient to manifest dense spheroid morphologies, a phenotype that increased primary tumor exit and invasion to EGF. Post-EMT invasion to EGF was dependent on increased activation of EGF receptor (EGFR) and p38 mitogen-activated protein kinase, all of which could be abrogated either by pharmacologic (PF-562271) or by genetic (shRNA) targeting of focal adhesion kinase (FAK). Mechanistically, EMT induced by TGF-? increased cell-surface levels of EGFR and prevented its physical interaction with E-cadherin, leading instead to the formation of oncogenic signaling complexes with T?R-II. Elevated EGFR expression was sufficient to transform normal mammary epithelial cells, and to progress their 3D morphology from that of hollow acini to branched structures characteristic of nonmetastatic breast cancer cells. Importantly, we show that TGF-? stimulation of EMT enabled this EGFR-driven breast cancer model to abandon their inherent branching architecture and form large, undifferentiated masses that were hyperinvasive to EGF and showed increased pulmonary tumor growth upon tail vein injection. Finally, chemotherapeutic targeting of FAK was sufficient to revert the aggressive behaviors of these structures. Collectively, this investigation has identified a novel EMT-based approach to neutralize the oncogenic activities of EGF and TGF-? in aggressive and invasive forms of breast cancer.

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Transforming growth factor-beta1 mediates epithelial to mesenchymal transdifferentiation through a RhoA-dependent mechanism.

Publications

Transforming growth factor-beta1 mediates epithelial to mesenchymal transdifferentiation through a RhoA-dependent mechanism.

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