Use of N-acetyl cysteine to increase intracellular glutathione during the induction of antitumor responses by IL-2.
IL-2 therapy can induce marked oxidative stress via reactive oxygen and nitrogen intermediates. Glutathione, the major intracellular reductant, may become rate limiting to cytotoxic lymphocyte activation and proliferation under these circumstances. N-Acetyl cysteine (NAc-cys) was used to increase intracellular glutathione levels during lymphokine-activated killer (LAK) cell activation by IL-2. Incubation of splenocytes with NAc-cys (0.6 to 1.0 mM) resulted in significant changes in intracellular reduced and total glutathione (92% and 58% increase, respectively) at 96 h. These levels correlated with markedly enhanced cell proliferation (threefold) and cytolytic effector cell generation (> fivefold increase in LU/10(6) cells) induced by the combination of NAc-cys with IL-2. IL-2 exposure by itself unexpectedly increased intracellular reduced glutathione by 43%. IL-2 and NAc-cys were synergistic in increasing glutathione levels (reduced glutathione: 292% increase; total: 251% increase). Inhibition of glutathione synthesis, using L-buthionine-(S,R)-sulfoximine reversed the effects of NAc-cys on intracellular glutathione, as well as cellular proliferation and cytotoxicity. This experiment established that the effects of NAc-cys required de novo glutathione synthesis. In conjunction with IL-2/LAK treatment, oral NAc-cys administration (260 to 900 mg/kg/day for 7 days) significantly decreased tumor progression in a refractory s.c. tumor model. A small fraction of mice (11 to 17%) had complete tumor regressions. NAc-cys may be useful as an adjunct to increase the antitumor activity of IL-2/LAK therapy.
Yim
C Y
CY
Department of Internal Medicine, University of Utah, Salt Lake City 84132.
Hibbs
J B
JB
McGregor
J R
JR
Galinsky
R E
RE
Samlowski
W E
WE
D000111:Acetylcysteine / Q000008:administration & dosage / Q000627:therapeutic use*; D000284:Administration, Oral; D000818:Animals; D003602:Cytotoxicity, Immunologic / Q000187:drug effects; D005260:Female; D005354:Fibrosarcoma / Q000276:immunology / Q000378:metabolism / Q000628:therapy*; D005978:Glutathione / Q000378:metabolism*; D007167:Immunotherapy; D066298:In Vitro Techniques; D007376:Interleukin-2 / Q000008:administration & dosage / Q000627:therapeutic use*; D015979:Killer Cells, Lymphokine-Activated / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D008213:Lymphocyte Activation / Q000187:drug effects; D008214:Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D010641:Phenotype
D007376:Interleukin-2; D005978:Glutathione; D000111:Acetylcysteine