Dissecting the role of TGF-beta type I receptor/ALK5 in pancreatic ductal adenocarcinoma: Smad activation is crucial for both the tumor suppressive and prometastatic function.

Abstract

In the present study, we have analysed the effects of transforming growth factor-beta (TGF-beta) signaling on the growth behavior of pancreatic carcinoma cells in vitro and on their tumorigenicity in vivo. Ectopic expression of dominant-negative mutants of the TGF-beta type II receptor or type I receptor/activin receptor-like kinase 5 (ALK5) in TGF-beta-sensitive pancreatic ductal adenocarcinoma PANC-1 cells prevented the TGF-beta-induced activation of transfected Smad-responsive reporter genes and growth arrest. The growth-inhibitory effect was mimicked by stable expression of kinase-active ALK5 (ALK5-T204D), and was dependent on ALK5's ability to activate Smad signaling, as a ALK5-derived mutant with an intact kinase domain but deficient in its ability to activate Smads (RImL45) failed to suppress proliferation in the absence of added TGF-beta. Moreover, this mutant often displayed opposite effects to those of ALK5-TD and blocked various ligand-induced responses in vitro, indicating that it acts in a dominant-negative fashion to inhibit endogenous wild-type receptors. ALK5-TD-, but not RImL45-TD-transduced cells underwent epithelial-to-mesenchymal transition, exhibited a higher ratio of thrombospondin-1 to vascular endothelial growth factor-A expression and upregulated various metastasis-associated genes. Upon orthotopic transplantation of PANC-1 clones into immunodeficient mice, ALK5-TD, but not RImL45-TD, greatly reduced tumor size and induced the formation of liver metastases in otherwise non-metastatic PANC-1 cells. These results suggest a causal, dominant role for the endogenous Smad2/3 signaling pathway in the tumor suppressor and prometastatic activities of TGF-beta in pancreatic tumor cells.

• Authors: B Schniewind, S Groth, S Sebens Müerköster, B Sipos, H Schäfer, H Kalthoff, F Fändrich, H Ungefroren
• Journal: Oncogene (Oncogene) Vol. 26 Issue 33 Pg. 4850-62 (Jul 19 2007) ISSN: 0950-9232 [Print] England
• PMID: 17297450 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Receptors, Transforming Growth Factor beta
• Smad Proteins
• Transforming Growth Factor beta
• Protein Serine-Threonine Kinases
• Activin Receptors, Type I
• Receptor, Transforming Growth Factor-beta Type I
• TGFBR1 protein, human
• Tgfbr1 protein, mouse
• Tgfbr1 protein, rat

Topics

• Activin Receptors, Type I (genetics, metabolism, physiology)
• Adenocarcinoma (genetics, metabolism, pathology)
• Animals
• Carcinoma, Pancreatic Ductal (genetics, metabolism, pathology)
• Cell Line
• Cell Line, Tumor
• Cell Proliferation (drug effects)
• Female
• Gene Expression (drug effects)
• Humans
• Immunoblotting
• Mice
• Mice, SCID
• Mutation
• Neoplasm Metastasis
• Neoplasms, Experimental (genetics, metabolism, pathology)
• Pancreatic Neoplasms (genetics, metabolism, pathology)
• Phosphorylation (drug effects)
• Protein Binding (drug effects)
• Protein Serine-Threonine Kinases
• Rats
• Receptor, Transforming Growth Factor-beta Type I
• Receptors, Transforming Growth Factor beta (genetics, metabolism, physiology)
• Reverse Transcriptase Polymerase Chain Reaction
• Smad Proteins (metabolism)
• Transfection
• Transforming Growth Factor beta (pharmacology)
• Tumor Burden