Antitumor activity of recombinant human interleukin-1 against heterotransplanted human non-Hodgkin lymphomas in nude mice

Antitumor activity of recombinant human interleukin 1 alpha (IL-1) against seven human non-Hodgkin lymphomas grown in athymic nude mice was studied. Growth of the lymphomas was markedly inhibited after an injection of 0.4 mg/kg IL-1. The growth inhibition of Burkitt lymphoma was found to be dose-dependent up to 0.4 mg/kg, reaching a plateau thereafter. The loss of colony-forming ability of the cells and the loss of cell viability showed the same type of dose-dependence and progressed during 24 h following an injection of IL-1. In accordance with these observations, histopathologic examination revealed progressively spreading coagulative necrosis without bleeding. Little infiltration of inflammatory cells into the tumor tissue was observed. IL-1 growth inhibition of T lymphoma in beige nude mice having low natural killer activity was similar to that in nude mice. These findings suggested that the antitumor effects might not be produced through cell-mediated antitumor actions. Immunocytological examination with anti-IL-1 antibody revealed that administered IL-1 was bound to the lymphoma cells, suggesting that IL-1 receptor is probably expressed on these cells in vivo. The antitumor action of IL-1 on the lymphomas may be exerted directly through the IL-1 receptor.