Targeting endogenous transforming growth factor beta receptor signaling in SMAD4-deficient human pancreatic carcinoma cells inhibits their invasive phenotype1.

Abstract

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.

• Authors: Gayathri Subramanian, Roderich E Schwarz, Linda Higgins, Glenn McEnroe, Sarvajit Chakravarty, Sundeep Dugar, Michael Reiss
• Journal: Cancer research (Cancer Res) Vol. 64 Issue 15 Pg. 5200-11 (Aug 01 2004) ISSN: 0008-5472 [Print] United States
• PMID: 15289325 (Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Antigens, Neoplasm
• Cadherins
• DNA-Binding Proteins
• Enzyme Inhibitors
• Integrins
• Receptors, Transforming Growth Factor beta
• SMAD2 protein, human
• SMAD3 protein, human
• SMAD4 protein, human
• Smad2 Protein
• Smad3 Protein
• Smad4 Protein
• TGFB1 protein, human
• TGFB2 protein, human
• Trans-Activators
• Transforming Growth Factor beta
• Transforming Growth Factor beta1
• Transforming Growth Factor beta2
• Transforming Growth Factor beta3
• integrin alphavbeta6
• Protein Serine-Threonine Kinases
• Activin Receptors, Type I
• Receptor, Transforming Growth Factor-beta Type I
• Receptor, Transforming Growth Factor-beta Type II

Topics

• Activin Receptors, Type I (metabolism)
• Antigens, Neoplasm (immunology, metabolism)
• Cadherins (metabolism)
• Cell Movement
• DNA-Binding Proteins (deficiency, metabolism)
• Enzyme Inhibitors (pharmacology)
• Gene Deletion
• Humans
• Integrins (antagonists & inhibitors, immunology, metabolism)
• Neoplasm Invasiveness
• Pancreatic Neoplasms (metabolism, pathology)
• Phenotype
• Phosphorylation (drug effects)
• Protein Serine-Threonine Kinases (antagonists & inhibitors)
• Receptor, Transforming Growth Factor-beta Type I
• Receptor, Transforming Growth Factor-beta Type II
• Receptors, Transforming Growth Factor beta (metabolism)
• Signal Transduction
• Smad2 Protein
• Smad3 Protein
• Smad4 Protein
• Trans-Activators (deficiency, metabolism)
• Transforming Growth Factor beta (antagonists & inhibitors, immunology, metabolism)
• Transforming Growth Factor beta1
• Transforming Growth Factor beta2
• Transforming Growth Factor beta3
• Tumor Cells, Cultured
• Wound Healing