Expression of Raf-1 Kinase Inhibitory Protein in Extrahepatic Bile Duct Carcinoma

BACKGROUND: Raf-1 kinase inhibitory protein (RKIP) recently has been identified as a metastasis suppressor in a variety of human carcinomas. The prognostic significance of RKIP expression in extrahepatic bile duct (EBD) carcinoma has not been studied. The aims of the current study were to evaluate RKIP expression and to determine the prognostic significance of RKIP expression in EBD carcinoma. METHODS: Immunohistochemical staining for RKIP was performed for 131 cases of EBD carcinoma. The associations of RKIP expression with clinicopathologic parameters and patient outcomes were examined. Multivariate logistic regression analysis was used to identify independent predictive parameters for lymphovascular invasion and nodal and distant metastases. RESULTS: Loss of RKIP expression was observed in 55.0% (72/131) of cases. EBD carcinoma had significantly lower RKIP immunoreactivity than normal EBD (p < 0.001). Loss of RKIP expression was significantly associated with lymphatic invasion (p = 0.030) and nodal metastasis (p = 0.036), but it was not found to be a significant prognostic predictor for overall, disease-free or distant metastasis-free survival. In addition, loss of RKIP expression was an independent predictor for lymphatic invasion (p = 0.027). CONCLUSIONS: These results suggest that RKIP may play a role in the suppression of lymphatic invasion and nodal metastasis in EBD carcinoma.

Differential Physiological Effects of Raf-1 Kinase Pathways Linked to Protein Kinase C Activation Depending on the Stimulus in v-H-ras-transformed Cells / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: We investigated the molecular mechanism by which the Raf-1 kinase pathways that are linked to protein kinase C induce differential physiological effects, depending on the stimulus, by employing the pharmacological PKC activator PMA. MATERIALS AND METHODS: Parental and v-Ha-ras transfected NIH 3T3 cells were chosen as test systems and these cells were transiently transfected with the pMTH vector that encodes dominant-negative (DN) PKC-epsilon with using Lipofectamine 2000. The cell proliferation reagent WST-1 was used for the quantitative determination of cellular proliferation. The Raf-1 kinase activity was measured by assessing the phosphorylation of recombinant MEK with using the immunoprecipitated Raf-1 proteins. The phosphorylated MEK protein bands were quantified by using Quantity One analysis software. RESULTS: The pharmacological PKC activator phorbol-12-myristate-13-acetate (PMA) and platelet-derived growth factor (PDGF) were able to induce the activation of Raf-1 kinase in the v-H-ras-transformed NIH3T3 fibroblasts. However, PMA was found to be much less sensitive PI3 kinase inhibitor or the chemical antioxidant than is PDGF. Especially, PMA mediated growth arrest while PDGF induced mitogenic signaling through the PKC-epsilon activation. Thus, the regulation of the Raf-1 cascade by both PDGF and PMA is likely to be intimately linked and they converge at the PKC level through different upstream pathways, as was shown by the inhibition of PDGF-induced Raf-1 kinase activation by the transient transfection with a dominant-negative mutant of PKC-epsilon. CONCLUSIONS: Taken together, these results imply that, depending on the stimulus, Raf-1 kinase leads to different physiological effects.

Expression and Mutation Analysis of RKIP (Raf-1 Kinase Inhibitor Protein) in Human Gastric Cancer

PURPOSE: RKIP (Raf kinase inhibitor protein) is a novel candidate tumor suppressor, known to inhibit the MAPK signaling by interfering with the MEK phosphorylation by Raf-1. The aim of this study was to investigate the expression of RKIP and analyze the pattern of inactivation and mutation of the RKIP gene in human gastric cancer. METHODS: To explore if RKIP inactivation is implicated in gastric tumorigenesis, an expression analysis on the transcription and protein expression levels and a mutational analysis of RKIP were performed in 15 human gastric cancer cell lines and 92 primary carcinoma tissues. RESULTS: Abnormal reduction of the level of RKIP expression was frequently detected in the cancer cell lines and primary tumor tissues, at both the transcript and protein levels. Moreover, the expression level of RKIP in the tumor cells was inversely correlated with the level of Erk phosphorylation, indicating that RKIP plays a key role in the regulation of the Raf-MEK-Erk signaling pathway in human gastric cells. While the expression of the RKIP transcript was not re-activated in low expressor cells by treatment with the demethylating agent 5'Aza-dC, the genomic RKIP was detected at low levels in many cancer cell lines, suggesting that an abnormal reduction of level of RKIP expression in tumors might be caused by allelic deletion of the gene rather than transcriptional silencing due to aberrant DNA hypermethylation. A loss of heterozygosity study, using an intragenic polymorphic marker, revealed that approximately 21% of the gastric cancers harbored allelic loss of the RKIP gene. CONCLUSION: Collectively, this study has demonstrated that RKIP is a tumor suppressor, whose expression is frequently downregulated by allelic deletion in human gastric cancers. This study also suggests that an altered expression of RKIP might contribute to the development of gastric cancer via abnormal elevation of the Raf-Erk signaling pathway.

Mechanism of protein kinase C regulating CD44 gene expression in vascular endothelial cells / 中国免疫学杂志

Objective:To study the mechanism of protein kinase C regulating CD44 gene expression in vascular endothelial cells.Methods:Human umbilical vein endothelial cells (HUVECs)were taken as study model.The extract of Raf-1 kinase by immunoprecipitation was used for the Western blot analysis,and its activity was determined by enhanced chemiluminescene assay.CD44 gene expression was detected with RT-PCR,and phosphorylation was measurated by autoradiography.Results:CD44 phosphorylation in HUVECs was enhanced by 10ng/ml PMA treatment as compared with untreated cells, which reached the highest level at 30 minutes. Raf-1 kinase activity increased significantly after exposure to 10ng /ml PMA, and 0.05 ?mol/L Calphostinc could inhibit the role of Protein kinase C(PKC). CD44 gene expression level increased obviously after exposure to 10 ng /ml PMA (PKC activator) for only 1 minute(P