H-Ras selectively up-regulates MMP-9 and COX-2 through activation of ERK1/2 and NF-κB:: An implication for invasive phenotype in rat liver epithelial cells

One of the most frequent events in carcinogenesis is uncontrolled activation of Ras signaling pathway. A previous study demonstrated that the introduction of H-Ras into the normal WB-F344 rat liver epithelial (WB) cell line and adult male F344 rats resulted in tumorigenicity. The present study investigated whether H-Ras induced the invasive and migrative phenotypes in WB cells, and subsequently aimed at characterizing the underlying mechanisms. H-Ras induced the invasive and migrative phenotypes of WB cells with a selective up-regulation of matrix metalloproteinase (MMP)-9, but not MMP-2. Cyclooxygenase (COX)-2 and the subsequent production of prostaglandin E-2 (PGE(2)) were also induced by H-Ras. Treatment of H-Ras WB cells with GM6001 and NS398, the inhibitors of MMPs and COX-2, respectively, significantly inhibited the H-Ras-induced invasive and migrative phenotypes. DNA binding activity of nuclear factor (NF)-kappa B, but not that of activator protein (AP)-1, was increased by H-Ras. Caffeic acid phenethyl ester and Bay 11-7082, specific inhibitors of NF-kappa B and IKK, respectively, significantly inhibited the expression of MMP-9 and COX-2, invasion and migration of H-Ras WB cells, revealing NF-kappa B as a transcriptional factor responsible for HRas-induced malignant phenotypic conversion of WB cells. Activation of ERKs pathway was critical for H-Ras-induced invasive and migrative phenotypes, up-regulation of MMP-9 and COX-2 as well as enhanced DNA binding activity of NF-kappa B in WB cells. Taken together, these results demonstrate that H-Ras up-regulates MMP-9 and COX-2 through activation of ERKs and IKK-I kappa B alpha-NF-kappa B signal pathway which may contribute to the malignant progression of WB rat liver epithelial cells. (c) 2006 Wiley-Liss, Inc.