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.
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.
Schniewind
B
B
Department of General Surgery and Thoracic Surgery, UKSH, Campus Kiel, Kiel, Germany.
Groth
S
S
Sebens Müerköster
S
S
Sipos
B
B
Schäfer
H
H
Kalthoff
H
H
Fändrich
F
F
Ungefroren
H
H
D030201:Activin Receptors, Type I / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D000230:Adenocarcinoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D000818:Animals; D021441:Carcinoma, Pancreatic Ductal / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D015151:Immunoblotting; D051379:Mice; D016513:Mice, SCID; D009154:Mutation; D009362:Neoplasm Metastasis; D009374:Neoplasms, Experimental / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases; D051381:Rats; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051785:Smad Proteins / Q000378:metabolism; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D047368:Tumor Burden
D018125:Receptors, Transforming Growth Factor beta; D051785:Smad Proteins; D016212:Transforming Growth Factor beta; D017346:Protein Serine-Threonine Kinases; D030201:Activin Receptors, Type I; D000077293:Receptor, Transforming Growth Factor-beta Type I; C000625841:TGFBR1 protein, human; C000625842:Tgfbr1 protein, mouse; C000625843:Tgfbr1 protein, rat