title: Graded activation of the MEK1/MT1-MMP axis determines renal epithelial cell tumor phenotype.
abstract: Activation of Raf/Ras/mitogen-activated protein kinase (MEK)/mitogen-activated protein kinase signaling and elevated expression of membrane type-1 matrix metalloproteinase (MT1-MMP) are associated with von Hippel-Lindau gene alterations in renal cell carcinoma. We postulated that the degree of MEK activation was related to graded expression of MT1-MMP and the resultant phenotype of renal epithelial tumors. Madin Darby canine kidney epithelial cells transfected with a MEK1 expression plasmid yielded populations with morphologic phenotypes ranging from epithelial, mixed epithelial/mesenchymal to mesenchymal. Clones were analyzed for MEK1 activity, MT1-MMP expression and extent of epithelial-mesenchymal transition. Phenotypes of the MDCK-MEK1 clones were evaluated in vivo with nu/nu mice. Tissue microarray of renal cell cancers was quantitatively assessed for expression of phosphorylated MEK1 and MT1-MMP proteins and correlations drawn to Fuhrman nuclear grade. Graded increases in the MEK signaling module were associated with graded induction of epithelial-mesenchymal transition of the MDCK cells and induction of MT1-MMP transcription and synthesis. Inhibition of MEK1 and MT1-MMP activity reversed the epithelial-mesenchymal transition. Tumors generated by epithelial, mixed epithelial/mesenchymal and mesenchymal MDCK clones demonstrated a gradient of phenotypes extending from well-differentiated, fully encapsulated non-invasive tumors to tumors with an anaplastic morphology, high Fuhrman nuclear score, neoangiogenesis and invasion. Tumor microarray demonstrated a statistically significant association between the extent of phosphorylated MEK1, MT1-MMP expression and nuclear grade. We conclude that graded increases in the MEK1 signaling module are correlated with M1-MMP expression, renal epithelial cell tumor phenotype, invasive activity and nuclear grade. Phosphorylated MEK1 and MT1-MMP may represent novel, and mechanistic, biomarkers for the assessment of renal cell carcinoma.
authors.affiliation: Department of Medicine, San Francisco Department of Veterans Affairs Medical Center, University of California, San Francisco, CA 94121, USA.
authors.forename: Rajeev
authors.initials: R
authors.lastname: Mahimkar
authors.forename: Maria Alejandra
authors.initials: MA
authors.lastname: Alfonso-Jaume
authors.forename: Leslie M
authors.initials: LM
authors.lastname: Cape
authors.forename: Rajvir
authors.initials: R
authors.lastname: Dahiya
authors.forename: David H
authors.initials: DH
authors.lastname: Lovett
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002292:Carcinoma, Renal Cell / Q000201:enzymology* / Q000473:pathology; D004285:Dogs; D004789:Enzyme Activation; D006801:Humans; D007150:Immunohistochemistry; D007680:Kidney Neoplasms / Q000201:enzymology* / Q000473:pathology; D048369:MAP Kinase Kinase 1 / Q000235:genetics / Q000378:metabolism*; D053511:Matrix Metalloproteinase 14 / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype
chemical_list: D048369:MAP Kinase Kinase 1; D053511:Matrix Metalloproteinase 14