Constitutive activation of mitogen-activated protein (MAP) kinases in human renal cell carcinoma.
Mitogen-activated protein kinases (MAPKs) play a pivotal role in the mitogenic signal transduction pathway and are essential components of the MAPK cascade, which includes MEK (also known as MAP kinase kinase), Raf-1, and Ras. In this study, we examined whether constitutive activation of the MAPK cascade was associated with the carcinogenesis of human renal cell carcinomas in a series of 25 tumors and in corresponding normal kidneys. Constitutive activation of MAPKs in tumor tissue, as determined by the appearance of phosphorylated forms, was found in 12 cases (48%), and this activation was confirmed by a direct in vitro kinase assay of immunoprecipitate using myelin basic protein as the substrate. The phosphorylation of MEK and of Raf-1, as monitored by a mobility shift in SDS-PAGE, which is reportedly associated with the activation of these kinases, occurred in 9 of 18 cases (50%) and in 6 of 11 cases (55%) respectively. The activation of MAPKs was correlated with MEK activation (P = 0.0045) and with Raf-1 activation (P = 0.067). Furthermore, overexpression of MEK was found in 13 of 25 cases (52%) by Western blot analysis, and this overexpression was associated significantly with MAPK activation (P = 0.034). No mutations were noted in H-,K-, or N-ras genes by PCR direct sequencing in any of the 25 tumor samples. Of the patients studied, 8 of 18 (44%) stage pT2 patients and four of six (67%) stage pT3 patients showed MAPK activation. The single stage pT1 patient did not evidence MAPK activation. Furthermore, one of seven (14%) grade 1 patients, 9 of 13 (69%) grade 2 patients, and two of five (40%) grade 3 patients showed MAPK activation (grade 1 versus grades 2 and 3, P = 0.046). Our results suggest that constitutive activation of MAPKs may be associated with the carcinogenesis of human RCCs.
Oka
H
H
Department of Urology, Faculty of Medicine, Kyoto University, Japan.
Chatani
Y
Y
Hoshino
R
R
Ogawa
O
O
Kakehi
Y
Y
Terachi
T
T
Okada
Y
Y
Kawaichi
M
M
Kohno
M
M
Yoshida
O
O
D000595:Amino Acid Sequence; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002292:Carcinoma, Renal Cell / Q000201:enzymology* / Q000473:pathology; D004789:Enzyme Activation; D011905:Genes, ras; D006801:Humans; D007680:Kidney Neoplasms / Q000201:enzymology* / Q000473:pathology; D020929:Mitogen-Activated Protein Kinase Kinases; D008969:Molecular Sequence Data; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf; D014407:Tumor Cells, Cultured
D011518:Proto-Oncogene Proteins; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases