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.
Subramanian
Gayathri
G
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.
Schwarz
Roderich E
RE
Higgins
Linda
L
McEnroe
Glenn
G
Chakravarty
Sarvajit
S
Dugar
Sundeep
S
Reiss
Michael
M
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