Highly malignant rat hepatoma AH66F cells respond to ascitic fluid.

Rat ascites hepatoma (AH) 66F cells are more maligant than AH130 cells. AH66F cells grew faster than AH130 cells in media supplemented with both 5% fetal calf serum (FCS) and 5% ascites fluid (ASF), which is obtained from rats bearing these cells. The growth of AH66F cells was more accelerated in ASF than in FCS. The motility of AH66F cells was significantly increased by ASF, while the cells hardly moved in FCS. The growth and motility of AH130 cells were not different in FCS and ASF. Moreover, the adhesion ability of AH66F cells to mesothelial cells (M-cells) isolated from the mesentery was significantly higher than that of AH130 cells just after harvesting from the rats. The fresh AH66F cells adhered to M-cells at about 60%, and the adhesion rate of the cells decreased to about 47% after culturing with 5% FCS for 48 hours but was maintained in the presence of ASF. The adhesion ability of AH130 cells was not changed after incubation with both FCS and ASF. On the other hand, it has been reported that AH66F cells are unique in having leukocyte function-associated antigen-1 (LFA-1) on the outer cell membrane, adhering through interaction with intercellular adhesion molecule-1 (ICAM-1) on M-cells, although AH130 cells are not so efficient as other hepatoma cells. Consequently, the adhesion of AH66F cells to M-cells was inhibited by anti-LFA-1 beta-chain monoclonal antibody and anti-ICAM-1 antibody. When cells were cultured separately with FCS or ASF, and the adhesion molecules were analysed using flow cytometry, the expression of LFA-1 molecules on AH66F cells was not changed by eitherv FCS or ASF, but the ICAM-1 molecule on M-cells was increased time-dependently by ASF. From these results, the high malignancy of AH66F cells attributes to responsibility to ASF for tumor growth and motility and to irregular expression of LFA-1 on the membrane, in comparison to AH130 cells.