Adhesion of renal carcinoma cells to endothelial cells depends on PKCmu.

BACKGROUND: The formation of metastases includes the separation of tumor cells from the primary tumor, cell migration into subendothelial tissue and cell proliferation in secondary organ. In this process, cell adhesion of tumor cells to the endothelium is an essential requirement for formation of metastases. Protein kinase C (PKC) regulates adhesion and proliferation. To identify a relation between PKC isoforms and tumor progression in renal cell carcinoma (RCC), the influence of PKC isoforms on cell adhesion and proliferation, and possible influences of integrins were analyzed in RCC cells. METHODS: The experiments were performed in the RCC cell lines CCF-RC1 and CCF-RC2 after pre-incubation (16 h) with the PKC inhibitors GF109203X (inhibits PKCalpha, betaI, betaII, gamma, delta and epsilon), GO6976 (inhibits PKCalpha, betaI and mu), RO31-8220 (inhibits PKCalpha, betaI, betaII, gamma and epsilon) and rottlerin (inhibits PKCdelta). Cell adhesion was assessed through adherence of RCC cells to an endothelial monolayer. Cell proliferation was analyzed by a BrdU incorporation assay. The expression of beta1 integrins was analyzed by flow cytometry. RESULTS: In CCF-RC1 cells, cell adhesion was significantly reduced by GO6976 to 55% and by RO31-8220 to 45% of control. In CCF-RC2 cells, only GO6976 induced a significant reduction of cell adhesion to 50% of control levels. Proliferation of both cell lines was reduced by rottlerin to 39% and 45% of control, respectively. The beta1 integrin expression on the cell surface of CCF-RC1 and CCR-RC2 cells was decreased by RO31-8220 to 8% and 7% of control, respectively. beta2 and beta3 integrins were undetectable in both cell lines. CONCLUSIONS: The combination of the PKC inhibitors leads to the assumption that PKCmu influences cell adhesion in CCF-RC1 and CCF-RC2 cells, whereas in CCF-RC1 cells PKCepsilon also seems to be involved in this process. The expression of beta1 integrins appears to be regulated in particular by PKCepsilon. Cell proliferation was inhibited by rottlerin, so that PKCdelta might be involved in cell proliferation in these cells.

Migration of renal carcinoma cells is dependent on protein kinase Cdelta via beta1 integrin and focal adhesion kinase.

Migration and adhesion of tumor cells are essential prerequisites for the formation of metastases in malignant diseases. Protein kinase C (PKC) has been shown to regulate cell migration, adhesion and proliferation. In order to identify a connection between PKC isoforms and tumor progression in renal cell carcinoma (RCC), the influence of PKC isoforms on cell migration, adhesion and proliferation and possible influences of the activity of integrins and focal adhesion kinase (FAK) were analyzed in RCC cells. The experiments were performed in the RCC cell line CCF-RC1 after pre-incubation of the cells with the PKC inhibitors GF109203X, GO6976, RO31-8220 and rottlerin. Cell migration and adhesion were assessed through chemotaxis analysis and adhesion to an endothelial monolayer, respectively. Cell proliferation was analysed by a BrdU incorporation assay. The expression and activity of beta1 integrins and FAK were analysed by Western blot analysis. GF109203X reduced cell migration to 69%, the activity of beta1 integrins to 63% and FAK expression to 82% compared to untreated cells. Rottlerin reduced cell migration in a concentration-dependent manner to 36%, cell proliferation to 81%, expression and activity of beta1 integrins to 72 and 79%, and expression and activity of FAK to 56 and 76% of untreated cells, respectively. RO31-8220 also reduced the expression and activity of beta1 integrins as well as the expression of FAK to 84, 66 and 66% of untreated cells, respectively. GO6976 reduced the expression of FAK to 60% of untreated cells. Cell migration was only slightly reduced by GO6976 to 84% of untreated cells, and cell adhesion remained uninfluenced. These findings show a critical role of PKCdelta in the regulation of tumor cell migration, which seems to be caused by affecting the expression and activity of beta1 integrins and FAK. These results can provide a basis for new strategies in preventing metastases of renal cell carcinoma.