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Identification of a GαGβγ, AKT and PKCα signalome associated with invasive growth in two genetic models of human breast cancer cell epithelial-to-mesenchymal transition

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The epithelial-to-mesenchymal transition (EMT) confers an aggressive subtype associated with chemotherapy resistance in epithelial cancers. However, the mechanisms underlying the EMT and its associated signaling dysfunctions are still poorly understood. In two genetic models of MCF-7 breast cancer cells induced to EMT by WISP-2 silencing and Snail transformation, we investigated the status of several signaling elements downstream of G-protein receptors (GPR) and their functional roles in the invasive growth potential. We report that the E-cadherin repressors Slug, Zeb1/2 and Twist are overexpressed in these EMT cells characterized by a triple negative phenotype (loss of estrogen ERα and progesterone PRA/PRB receptors, no HER2 amplification), combined with loss of the alternative GPR30 estrogen receptor and induction of the invasive growth in collagen type I gels. Ectopic Snail expression suppressed WISP-2 transcripts and down-regulated WISP-2 gene promoter expression in transfected cells. Accordingly, WISP-2 transcripts and Wisp-2 protein were depleted in these two convergent models of BC cell EMT. The EMT caused dominance of several proinvasive pathways downstream of GPR, including GαGβγ subunits, PKCα, AKT and c-Jun induction, constitutive activation of the actin-remodeling GTPase Rac1, coupled with growth responses (more cells at S and G2/M phases of the cell cycle), in line with inhibition of the p27kip1/cyclin-dependent kinase CDK3 cascade. RNA interference or selective inhibitors targeting GαGβγ subunits (BIM-46187, gallein), PKCα (Gö6976, MT477, sh-RNAs) and PI3K-AKT (wortmannin) alleviated the invasive phenotype. In contrast, MCF-7 cells in EMT showed signaling independence to inhibitors of HER family tyrosine kinases and the mitogen- and stress-activated protein kinases. Our study suggests that the signaling protagonists GαGβγ, PKCα and PI3K-AKT are promising candidates as predictive molecular biomarkers and therapeutic targets in the management of clinical BC in EMT.
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Document Type: Research Article

Affiliations: 1: Laboratory of Cancer Biology and Therapeutics, Centre de Recherche Saint-Antoine and Université Pierre et Marie Curie (Paris 6), Paris, France 2: Laboratory of Experimental Cancer Research, Department of Radiotherapy and Nuclear Medicine,Ghent University Hospital, B-9000 Ghent, Belgium 3: INSERM UMR_S938, Centre de Recherche Saint-Antoine and Université Pierre et Marie Curie (Paris 6), Paris, France 4: Goormaghtigh Institute of Pathology, Ghent University Hospital, B-9000 Ghent, Belgium 5: Medisyn Technologies, Inc. Minnetonka, MN, USA 6: InteRNA Technologies, Utrecht, The Netherlands 7: The University of Texas M.D. Anderson Cancer Center, TX, USA 8: Molecular and Clinical Oncology, Centre de Recherche Saint-Antoine and Université Pierre et Marie Curie (Paris 6), Paris, France

Publication date: January 1, 2012

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  • The International Journal of Oncology provides an international forum for the publication of the latest, cutting-edge research in the broad area of oncology and cancer treatment. The journal accepts original high quality works and reviews on all aspects of oncology research including carcinogenesis, metastasis, epidemiology, chemotherapy and viral oncology. Through fair and efficient peer review, the journal is dedicated to publishing top tier research in the field, offering authors rapid publication as well as high standards of copy-editing and production. The International Journal of Oncology is published on a monthly basis in both print and early online.
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