Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Systemic interleukin-2 (IL-2) therapy has been limited by a major side effect known as "capillary leak syndrome", characterized by retention of extravascular fluid, severe hypotension, and multiple organ system dysfunction. The present study tested the hypothesis that an overproduction of nitric oxide (NO) induced by IL-2 therapy was, at least in part, responsible for this syndrome. Studies were undertaken in healthy or C3-L5 mammary adenocarcinoma bearing C3H/HeJ mice to evaluate whether treatment with inhibitors of NO synthesis (N{dollar}\rm\sp{lcub}G{rcub}{dollar}-Methyl-L-Arginine, NMMA and N{dollar}\rm\sp{lcub}G{rcub}{dollar}-Nitro-L-Arginine methyl ester, L-NAME) can prevent IL-2 induced capillary leakage without compromising the therapeutic benefit of IL-2. Intraperitoneal IL-2 therapy in both groups of mice caused substantial capiliary leakage, and a substantial rise in NO production in vivo. Addition of subcutaneous NMMA failed to ameliorate IL-2 induced capillary leakage, or NO overproduction, and did not compromise antitumor effects of IL-2. Subcutaneous NMMA alone reduced primary tumor growth, spontaneous pulmonary metastasis and tumor-induced pulmonary edema. Chronic administration of NMMA by the oral route, however, succeeded in abrogating IL-2 induced NO overproduction as well as capillary leakage in healthy mice.;L-NAME given chronically in the drinking water led to a parallel reduction in the IL-2 therapy-induced NO overproduction and capillary leakage in healthy mice. IL-2 therapy (1) caused structural damage to the lungs and its capillaries; (2) induced inducible type NO synthase (iNOS) expression in numerous tissues, including the endothelium, muscles of the anterior thoracic wall and splenic macrophages; (3) induced a high NOS activity in the lungs and the anterior thoracic wall of animals exhibiting pulmonary edema and pleural effusion. Addition of L-NAME therapy totally abolished NOS activity, but not necessarily iNOS expression, and significantly restored structural integrity of the lungs in conjunction with an amelioration of pulmonary edema and pleural effusion. These results strongly suggested that local NO overproduction, resulting from an induction of iNOS enzyme by IL-2 therapy, was responsible for the structural damage and consequent fluid leakage from the capillaries.;In mammary adenocarcinoma bearing mice, oral L-NAME alone produced significant antitumor as well as antimetastatic effects. L-NAME in combination with IL-2 therapy in these mice succeeded in ameliorating IL-2 induced as well as tumor-induced capillary leakage and potentiated tumor reductive function of IL-2. An abrogation of IL-2 induced NO production by L-NAME treatment in vivo as well as in vitro markedly stimulated IL-2 induced generation of antitumor cytotoxicity of splenocytes of healthy as well as tumor-bearing mice. IL-2 induced increase in NO production interfered with optimal lymphokine activated killer (LAK) cell activation which can be overcome by NO inhibition with L-NAME therapy.;NO apparetnly promoted tumor progression in the C3-L5 mammary tumor model. Tumor cells as well as endothelium of the tumor vasculature were identified as the source of NO within the tumor. Immunoreactive endothelial type NOS (eNOS) was detected in both cell classes within the primary as well as metastatic tumors. Furthermore, C3-L5 cells in vitro were positive for eNOS and expressed iNOS when incubated with LPS+IFN{dollar}\tau.{dollar} Treatment with NO inhibitors NMMA or L-NAME, reduced in vitro invasive ability of C3-L5 tumor cells, which was restored by addition of excess L-arginine. Treatment with IFN{dollar}\tau{dollar}+LPS stimulated NO production by these cells and also stimulated their invasiveness. Thus, NO production by the tumor cells promoted tumor cell invasiveness. (Abstract shortened by UMI.)



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