Macrophage potentiation of invasive capacity of rat ascites hepatoma cells.

In vitro and in vivo invasive capacities of rat ascites hepatoma cells (AH 130) that had been cultured on the feeder layers of rat macrophages were examined. The in vitro invasive capacity of the tumor cells was measured by their ability to form tumor cell colonies underneath cultured mesothelial cell monolayers; in vivo invasive capacity was examined by the implantation of the tumor cells into the rat peritoneal cavity. When the tumor cells were precultured on a macrophage feeder layer, the in vitro invasive capacity of the tumor cells increased almost 10 times as much as that of uncocultred control cells. The cocultured tumor cells, when implanted in rat peritoneal cavity, infiltrated extensively in the peritoneum and formed many tumor nodules and enlarged metastatic lymph nodes. Implantation of the uncocultured tumor cells did not develop any macroscopically detectable nodules. The effect of macrophages was reversed by subculturing the cocultured tumor cells without macrophages. Treatment of the tumor cells with the medium conditioned by macrophage culture did not result in the increase in invasive capacity. Almost 50% of the macrophage-mediated enhancement of the in vitro invasive capacity was inhibited by the simultaneous addition of superoxide dismutase and catalase at the time of tumor cell-macrophage coculture.