title: Prostate apoptosis response-4 mediates TGF-β-induced epithelial-to-mesenchymal transition.
abstract: A growing body of evidence supports that the epithelial-to-mesenchymal transition (EMT), which occurs during cancer development and progression, has a crucial role in metastasis by enhancing the motility of tumor cells. Transforming growth factor-β (TGF-β) is known to induce EMT in a number of cancer cell types; however, the mechanism underlying this transition process is not fully understood. In this study we have demonstrated that TGF-β upregulates the expression of tumor suppressor protein Par-4 (prostate apoptosis response-4) concomitant with the induction of EMT. Mechanistic investigations revealed that exogenous treatment with each TGF-β isoform upregulates Par-4 mRNA and protein levels in parallel levels of phosphorylated Smad2 and IκB-α increase. Disruption of TGF-β signaling by using ALK5 inhibitor, neutralizing TGF-β antibody or phosphoinositide 3-kinase inhibitor reduces endogenous Par-4 levels, suggesting that both Smad and NF-κB pathways are involved in TGF-β-mediated Par-4 upregulation. NF-κB-binding sites in Par-4 promoter have previously been reported; however, using chromatin immunoprecipitation assay we showed that Par-4 promoter region also contains Smad4-binding site. Furthermore, TGF-β promotes nuclear localization of Par-4. Prolonged TGF-β3 treatment disrupts epithelial cell morphology, promotes cell motility and induces upregulation of Snail, vimentin, zinc-finger E-box binding homeobox 1 and N-Cadherin and downregulation of Claudin-1 and E-Cadherin. Forced expression of Par-4, results in the upregulation of vimentin and Snail expression together with increase in cell migration. In contrast, small interfering RNA-mediated silencing of Par-4 expression results in decrease of vimentin and Snail expression and prevents TGF-β-induced EMT. We have also uncovered a role of X-linked inhibitor of apoptosis protein in the regulation of endogenous Par-4 levels through inhibition of caspase-mediated cleavage. In conclusion, our findings suggest that Par-4 is a novel and essential downstream target of TGF-β signaling and acts as an important factor during TGF-β-induced EMT.
authors: Department of Medical Biology, Research group in Molecular Oncology and Endocrinology, Université du Québec à Trois-Rivières, Trois-Rivières, Québec, Canada.
authors: P
authors: P
authors: Chaudhry
authors: Department of Medical Biology, Research group in Molecular Oncology and Endocrinology, Université du Québec à Trois-Rivières, Trois-Rivières, Québec, Canada.
authors: F
authors: F
authors: Fabi
authors: Department of Medical Biology, Research group in Molecular Oncology and Endocrinology, Université du Québec à Trois-Rivières, Trois-Rivières, Québec, Canada.
authors: M
authors: M
authors: Singh
authors: Department of Medical Biology, Research group in Molecular Oncology and Endocrinology, Université du Québec à Trois-Rivières, Trois-Rivières, Québec, Canada.
authors: S
authors: S
authors: Parent
authors: Department of Medical Biology, Research group in Molecular Oncology and Endocrinology, Université du Québec à Trois-Rivières, Trois-Rivières, Québec, Canada.
authors: V
authors: V
authors: Leblanc
authors: Department of Medical Biology, Research group in Molecular Oncology and Endocrinology, Université du Québec à Trois-Rivières, Trois-Rivières, Québec, Canada.
authors: E
authors: E
authors: Asselin
mesh_terms: D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D016889:Endometrial Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D058750:Epithelial-Mesenchymal Transition; D005260:Female; D006801:Humans; D051379:Mice; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D015398:Signal Transduction; D051901:Smad4 Protein / Q000235:genetics / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D002583:Uterine Cervical Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology
chemical_list: D051017:Apoptosis Regulatory Proteins; D016328:NF-kappa B; D051901:Smad4 Protein; D016212:Transforming Growth Factor beta; C101296:prostate apoptosis response-4 protein