Interaction between cisplatin-treated macrophages and Dalton's lymphoma cells in vitro.

Murine peritoneal macrophages treated with cisplatin (10 micrograms/ml) showed increased binding to Dalton's lymphoma cells in vitro. Macrophages and target cells both extend cytoplasmic extensions towards each other, which finally join and fuse to form a distinct cytoplasmic bridge between the two cells. At later stages of coincubation the macrophages and tumor cells get closely bound with several short cytoplasmic connections. Finally the plasmalemmae between the two cells fuse over a large surface area and the tumor cell is phagocyted. No tumor cell was found to form cytoplasmic bridges when incubated with untreated macrophages. The base of cytoplasmic bridge and the cytoplasmic bridge between the macrophage and tumor cells stained for actin and fibronectin, but not for tubulin. We also report the transfer of lysosomes from the cytoplasm of cisplatin-treated macrophages to the tumor cell cytoplasm through cytoplasmic bridges. It is further reported that cisplatin-induced macrophage cytotoxicity against DL cells is inhibited by nifedipine and chlorpromazine.