RESUMEN

Transforming growth factor (TGF)-beta1 has a biphasic effect on rat intestinal epithelial (RIE) cells. By itself, TGF-beta1 functions as a tumor suppressor by inhibiting the growth, migration and invasion of RIE cells. We show in this study that in conjunction with epidermal growth factor (EGF), TGF-beta1 helped to augment migration, invasion and anchorage-independent growth (AIG) compared to that by EGF alone. EGF plus TGF-beta1 induced a dramatic morphological change characteristic of epithelial-mesenchymal transition (EMT). The mechanism for this enhanced effect of TGF-beta1 and EGF on oncogenic properties was explored by analysis of EGF- and TGF-beta1-mediated signaling pathways and complementary DNA arrays. TGF-beta1 augmented EGF-mediated signaling of mitogen-activated protein kinase (MAPK) and AKT by enhancing and prolonging the activation of the former and prolonging the activation of the latter. Inhibition of MAPK, but not phosphoinositide-3 kinase (PI3K), abolished TGF-beta1 plus EGF-induced EMT and downregulation of E-cadherin at mRNA and protein levels. By contrast, cell migration and invasion were sensitive to inhibition of either MAPK or PI3 kinase. TGF-beta1 plus EGF-induced AIG was significantly more resistant to inhibition of PI3K and MAPK compared to that induced by EGF alone. EGF and TGF-beta1 synergistically induced the expression of a series of proteases including matrix metalloproteinase (MMP) 1 (collagenase), MMP3, MMP9, MMP10, MMP14 and cathepsin. Among them, the expression of MMP1, MMP3, MMP9 and MMP10 was MAPK dependent. Inhibition of the MMPs or cathepsin significantly blocked EGF plus TGF-beta1-induced invasion, but had no effect on colony formation. Phospholipase C (PLC) and Cox2 induced by EGF plus TGF-beta1 also played a significant role in invasion, whereas PLC was also important for colony formation. Our study reveals specific signaling functions and induction of genes differentially required for enhanced effect of EGF- and TGF-beta1-induced oncogenic properties, and helps to explain the tumor-promoting effect of TGF-beta1 in human cancer with elevated expression or activation of TGF-beta1 and receptor protein tyrosine kinases.

Asunto(s)

Transformación Celular Neoplásica/efectos de los fármacos , Factor de Crecimiento Epidérmico/farmacología , Células Epiteliales/metabolismo , Mucosa Intestinal/metabolismo , Transducción de Señal/efectos de los fármacos , Factor de Crecimiento Transformador beta1/farmacología , Proteínas Supresoras de Tumor/agonistas , Animales , Catepsinas/antagonistas & inhibidores , Catepsinas/metabolismo , Movimiento Celular/efectos de los fármacos , Proliferación Celular/efectos de los fármacos , Transformación Celular Neoplásica/inducido químicamente , Transformación Celular Neoplásica/metabolismo , Sinergismo Farmacológico , Factor de Crecimiento Epidérmico/agonistas , Factor de Crecimiento Epidérmico/metabolismo , Células Epiteliales/patología , Quinasas MAP Reguladas por Señal Extracelular/metabolismo , Perfilación de la Expresión Génica , Humanos , Mucosa Intestinal/patología , Inhibidores de la Metaloproteinasa de la Matriz , Metaloproteinasas de la Matriz/metabolismo , Análisis de Secuencia por Matrices de Oligonucleótidos , Fosfatidilinositol 3-Quinasas/metabolismo , Proteínas Proto-Oncogénicas c-akt/metabolismo , Ratas , Factor de Crecimiento Transformador beta1/agonistas , Factor de Crecimiento Transformador beta1/metabolismo , Proteínas Supresoras de Tumor/metabolismo , Proteínas Supresoras de Tumor/farmacología , Fosfolipasas de Tipo C/metabolismo