Effect of 5'-nucleotidase inhibitors on mouse immune system and experimental murine tumors

Nucleoticidin and melanocidins A and B exhibited potent inhibitory activity against 5'-nucleotidases from rat liver membrane and snake venom. Nucleoticidin retarded growth of Sarcoma 180 solid tumor, and melanocidins A and B prolonged the survival period of mice bearing B16 melanoma. These inhibitors enhanced phagocytic activity, interleukin-1 production and superoxide-generating activity of murine peritoneal macrophages. The tumor necrosis factor was also induced by the inhibitors. These results suggested that 5'-nucleotidase inhibitors inhibit tumor growth by modification of the immune system.