Transforming growth factor-beta1 promotes invasiveness after cellular transformation with activated Ras in intestinal epithelial cells.
Invasion is a defining event in carcinoma progression. In general, invasive carcinoma is characterized by an epithelial-fibroblastoid conversion associated with loss of cell-cell adhesion receptors such as E-cadherin and beta-catenin. We report here that TGF-beta1 promotes the invasiveness by modulating the alterations of cellular plasticity including a loss of cell-cell contact in Ras-transformed epithelial cells. In order to examine the role of TGF-beta1 in the Ras-induced responses, intestinal epithelial cells expressing a conditionally activated Ha-Ras(Val12) (RIE-iRas cells) were used in this study. Induced expression of activated Ha-Ras(Val12) caused morphologic transformation of the RIE-iRas cells with an increase in vimentin expression and a decrease of E-cadherin levels. There was also redistribution of beta-catenin from the cytoplasm to the nucleus after the induction of Ras. TGF-beta1 treatment enhanced both the decrease in E-cadherin levels and the redistribution of beta-catenin. Interestingly, the activation of Ras markedly decreased the level of TGF-beta receptor type II (TbetaRII) in RIE-iRas cells. However, the expression of plasminogen activator inhibitor-1, which is known to be transcriptionally induced by TGF-beta1, was strongly induced by TGF-beta1 despite the marked downregulation of TbetaRII. The induction of Ha-Ras(Val12) markedly increased the invasiveness in RIE-iRas cells, as evaluated by a collagen type I-coated Boyden-chamber assay, and the Ras-mediated invasiveness was significantly enhanced by TGF-beta1 treatment. Expression of a dominant-negative form of TbetaRII in the RIE-iRas cells abrogated both growth-inhibitory and invasion responses to TGF-beta1. Collectively, these results suggest that TGF-beta1 and oncogenic Ras collaborate in promoting cellular invasiveness in intestinal epithelial cells. The enhancement of invasiveness was correlated with decreased E-cadherin levels and subcellular distribution of beta-catenin. The enhancement of oncogenic Ras-mediated cell transformation by TGF-beta1 occurs via TbetaRII.
Fujimoto
K
K
Department of Surgery, Vanderbilt University Medical Center and Vanderbilt-Ingram Cancer Center, Nashville, Tennessee 37232, USA.
Sheng
H
H
Shao
J
J
Beauchamp
R D
RD
D022005:Adherens Junctions / Q000187:drug effects; D015820:Cadherins / Q000378:metabolism; D002277:Carcinoma / Q000378:metabolism / Q000473:pathology*; D002461:Cell Line, Transformed; D015179:Colorectal Neoplasms / Q000378:metabolism / Q000473:pathology*; D003598:Cytoskeletal Proteins / Q000378:metabolism; D015536:Down-Regulation; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D007413:Intestinal Mucosa / Q000378:metabolism / Q000473:pathology*; D009361:Neoplasm Invasiveness; D015689:Oncogene Protein p21(ras) / Q000235:genetics* / Q000378:metabolism; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism; D015534:Trans-Activators; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1; D051176:beta Catenin
D015820:Cadherins; D003598:Cytoskeletal Proteins; D017395:Plasminogen Activator Inhibitor 1; D018125:Receptors, Transforming Growth Factor beta; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D051176:beta Catenin; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II; D015689:Oncogene Protein p21(ras)