A Protein Kinase C Inhibitor NA-382 Prolongs the Life Span of AH66F-Bearing Rats as Well as Inhibiting Leukocyte Function-Associated Antigen-1 (LFA-1)-Dependent Adhesion of the Cells

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Rat ascites hepatoma AH66F is a high malignant tumor line, and AH66F-bearing rats died about 10 d after tumor inoculation. When treated with a protein kinase C (PKC) inhibitor, NA-382, the life span of AH66F-bearing rats was significantly prolonged, while a potent protein kinase A inhibitor, H-89, was not effective. In the adhesion assay, the adhesive ability to the mesentery-derived mesothelial cells (M-cells) of AH66F cells from rats injected with 10 mg/kg of NA-382 was significantly decreased, while the adhesion rate of the cells from the vehicle control group and from the H-89 (10 mg/kg)-treated group was about 50%. The adhesion of AH66F cells from the vehicle control group was curtailed to one half by leukocyte function-associated antigen-1 (LFA-1) β-chain monoclonal antibody (WT.3), but that from the NA-382 group was not further influenced by WT.3. In flow cytometric analysis using WT.3, the expression of LFA-1 β-chain on AH66F cells from the NA-382-treated group was also partially decreased, while that from the H-89-treated group was not changed. It was confirmed in vitro that after treatment with these protein kinase inhibitors for 48 h the expression of LFA-1 β-chain in the cells was decreased by NA-382, but not by H-89. These results suggested that the PKC inhibitor prolongs the life span of AH66F-bearing rats through inhibition of LFA-1-dependent adhesion of the cells.