Targeting endogenous transforming growth factor beta receptor signaling in SMAD4-deficient human pancreatic carcinoma cells inhibits their invasive phenotype1.
Transforming growth factor-beta (TGF-beta) suppresses tumor formation by blocking cell cycle progression and maintaining tissue homeostasis. In pancreatic carcinomas, this tumor suppressive activity is often lost by inactivation of the TGF-beta-signaling mediator, Smad4. We found that human pancreatic carcinoma cell lines that have undergone deletion of MADH4 constitutively expressed high endogenous levels of phosphorylated receptor-associated Smad proteins (pR-Smad2 and pR-Smad3), whereas Smad4-positive lines did not. These elevated pR-Smad levels could not be attributed to a decreased dephosphorylation rate nor to increased expression of TGF-beta type I (TbetaR-I) or type II (TbetaR-II) receptors. Although minimal amounts of free bioactive TGF-beta1 and TGF-beta2 were detected in conditioned medium, treatment with a pan-specific (but not a TGF-beta3 specific) TGF-beta-neutralizing antibody and with anti-alpha(V)beta(6) integrin antibody decreased steady-state pSmad2 levels and activation of a TGF-beta-inducible reporter gene in neighboring cells, respectively. Thus, activation of TGF-beta at the cell surface was responsible for the increased autocrine endogenous and paracrine signaling. Blocking TbetaR-I activity using a selective kinase inhibitor (SD-093) strongly decreased the in vitro motility and invasiveness of the pancreatic carcinoma cells without affecting their growth characteristics, morphology, or the subcellular distribution of E-cadherin and F-actin. Moreover, exogenous TGF-beta strongly stimulated in vitro invasiveness of BxPC-3 cells, an effect that could also be blocked by SD-093. Thus, the motile and invasive properties of Smad4-deficient pancreatic cancer cells are at least partly driven by activation of endogenous TGF-beta signaling. Therefore, targeting the TbetaR-I kinase represents a potentially powerful novel therapeutic approach for the treatment of this disease.
Departments of Internal Medicine (Medical Oncology), The Cancer Institute of New Jersey, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, 195 Little Albany Street, New Brunswick, NJ 08903, USA.
Gayathri
G
Subramanian
Roderich E
RE
Schwarz
Linda
L
Higgins
Glenn
G
McEnroe
Sarvajit
S
Chakravarty
Sundeep
S
Dugar
Michael
M
Reiss
D030201:Activin Receptors, Type I / Q000378:metabolism*; D000951:Antigens, Neoplasm / Q000276:immunology / Q000378:metabolism; D015820:Cadherins / Q000378:metabolism; D002465:Cell Movement; D004268:DNA-Binding Proteins / Q000172:deficiency* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017353:Gene Deletion; D006801:Humans; D016023:Integrins / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism; D009361:Neoplasm Invasiveness; D010190:Pancreatic Neoplasms / Q000378:metabolism* / Q000473:pathology; D010641:Phenotype; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism*; D015398:Signal Transduction; D051899:Smad2 Protein; D051900:Smad3 Protein; D051901:Smad4 Protein; D015534:Trans-Activators / Q000172:deficiency* / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism; D053773:Transforming Growth Factor beta1; D053781:Transforming Growth Factor beta2; D053782:Transforming Growth Factor beta3; D014407:Tumor Cells, Cultured; D014945:Wound Healing
D000951:Antigens, Neoplasm; D015820:Cadherins; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D016023:Integrins; D018125:Receptors, Transforming Growth Factor beta; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; C497796:SMAD4 protein, human; D051899:Smad2 Protein; D051900:Smad3 Protein; D051901:Smad4 Protein; C508960:TGFB1 protein, human; C509041:TGFB2 protein, human; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D053781:Transforming Growth Factor beta2; D053782:Transforming Growth Factor beta3; C073878:integrin alphavbeta6; D017346:Protein Serine-Threonine Kinases; D030201:Activin Receptors, Type I; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II