title: H-Ras-specific activation of Rac-MKK3/6-p38 pathway: its critical role in invasion and migration of breast epithelial cells.
abstract: Human tumors frequently exhibit constitutively activated Ras signaling, which contributes to the malignant phenotype. Mounting evidence suggests unique roles of the Ras family members, H-Ras, N-Ras and K-Ras, in normal and pathological conditions. In an effort to dissect distinct Ras isoform-specific functions in malignant phenotypic changes, we previously established H-Ras- and N-Ras-activated MCF10A human breast epithelial cell lines. Using these, we showed that p38 kinase is a key signaling molecule differentially regulated between H-Ras and N-Ras, leading to H-Ras-specific induction of invasive and migrative phenotypes. The present study is to further investigate H-Ras- and N-Ras-mediated signaling pathways and to unveil how these pathways are integrated for regulation of invasive/migrative phenotypic conversion of human breast epithelial cells. Here we report that the Rac-MAPK kinase (MKK)3/6-p38 pathway is a unique signaling pathway activated by H-Ras, leading to the invasive/migrative phenotype. In contrast, Raf-MEK-ERK and phosphatidylinositol 3-kinase-Akt pathways, which are fundamental to proliferation and differentiation, are activated by both H-Ras and N-Ras. A significant role for p38 in cell invasion is further supported by the observation that p38 activation by MKK6 transfection is sufficient to induce invasive and migrative phenotypes in MCF10A cells. Activation of the MKK6-p38 pathway results in a marked induction of matrix metalloproteinase (MMP)-2, whereas it had little effect on MMP-9, suggesting MMP-2 up-regulation by MKK6-p38 pathway as a key step for H-Ras-induced invasion and migration. We also provide evidence for cross-talk among the Rac, Raf, and phosphatidylinositol 3-kinase pathways critical for regulation of MMP-2 and MMP-9 expression and invasive phenotype. Taken together, the present study elucidated the role of the Rac-MKK3/6-p38 pathway leading to H-Ras-specific induction of malignant progression in breast epithelial cells, providing implications for developing therapeutic strategies for mammary carcinoma to target Ras downstream signaling molecules required for malignant cancer cell behavior but less critical for normal cell functions.
authors.affiliation: College of Pharmacy, Duksung Women's University, Seoul 132-714, Korea.
authors.forename: Ilchung
authors.initials: I
authors.lastname: Shin
authors.forename: Seonhoe
authors.initials: S
authors.lastname: Kim
authors.forename: Hyun
authors.initials: H
authors.lastname: Song
authors.forename: Hyeong-Reh Choi
authors.initials: HR
authors.lastname: Kim
authors.forename: Aree
authors.initials: A
authors.lastname: Moon
mesh_terms: D001940:Breast / Q000166:cytology*; D002454:Cell Differentiation; D002460:Cell Line; D045744:Cell Line, Tumor; D002465:Cell Movement; D049109:Cell Proliferation; D004847:Epithelial Cells / Q000166:cytology* / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D048371:MAP Kinase Kinase 3 / Q000378:metabolism*; D048669:MAP Kinase Kinase 6 / Q000378:metabolism*; D020778:Matrix Metalloproteinase 2 / Q000096:biosynthesis; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D009361:Neoplasm Invasiveness; D010641:Phenotype; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D020033:Protein Isoforms; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D014162:Transfection; D015854:Up-Regulation; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D020033:Protein Isoforms; D019869:Phosphatidylinositol 3-Kinases; D019908:Proto-Oncogene Proteins c-raf; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048371:MAP Kinase Kinase 3; D048669:MAP Kinase Kinase 6; C482530:MAP2K3 protein, human; C482566:MAP2K6 protein, human; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; D020830:rac1 GTP-Binding Protein; D018631:ras Proteins