Synergistic antitumor activity of interleukin-2 and cimetidine against syngeneic murine tumor.
Cimetidine, an H2 histamine receptor antagonist, is a potent immunomodulating agent, which acts by inhibiting suppressor T lymphocyte function. The present work investigated the effect, if any, of cimetidine on interleukin-2 (IL-2)-induced natural killer (NK) and lymphokine-activated killer (LAK) cell activities, and on in vivo antitumor activity using syngeneic colon 26 adenocarcinoma as the model. Mimicking the clinical conditions, all in vitro experiments were evaluated with the splenocytes prepared from tumor-bearing BALB/c mice. Ten days after subcutaneous inoculation of tumor cells (5 x 10(5)), animals were treated intraperitoneally daily with phosphate-buffered saline (PBS), cimetidine (2 mg kg-1 day-1), IL-2 (300,000 IU/day), or cimetidine plus IL-2 for 7 consecutive days. The treatment of IL-2 plus cimetidine increased NK and LAK cell activities significantly and synergistically at the end of the treatment (i.e. on day 18) as well as 1 week after the treatment (i.e. on day 25), in comparison with those of the control groups (PBS, cimetidine alone, IL-2 alone). Also, in vivo antitumor activity, as analyzed by a Kaplan-Meier life table with the log-rank test, revealed a significantly prolonged survival in the group treated with IL-2 plus cimetidine compared to the control groups. Phenotyping performed on the murine splenocytes on day 18 indicated a significant reduction in Lyt2-positive cells in the cimetidine-treated group in comparison with the PBS group. A significant increase in asialo GM1-positive cells and IL-2-receptor-positive cells was detected in the group treated with IL-2 plus cimetidine in comparison with the PBS and IL-2 control groups. Therefore, this study indicates a synergistic enhancement of IL-2-induced NK and LAK cell activities in tumor-bearing hosts by cimetidine, a noncytotoxic inhibitor of suppressor T function, and a significantly prolonged survival of tumor-bearing animals treated by IL-2 plus cimetidine. It also suggests the clinical potential of combination therapy of IL-2 with cimetidine.
Nakajima
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Department of Diagnostic Immunology Research and Biochemistry, Roswell Park Memorial Institute, New York State Department of Health, Buffalo 14263.
Chu
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D000230:Adenocarcinoma / Q000188:drug therapy*; D000818:Animals; D000954:Antigens, Surface / Q000276:immunology; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D002927:Cimetidine / Q000494:pharmacology*; D003110:Colonic Neoplasms / Q000188:drug therapy*; D004357:Drug Synergism; D005260:Female; D016130:Immunophenotyping; D007376:Interleukin-2 / Q000494:pharmacology*; D015979:Killer Cells, Lymphokine-Activated / Q000187:drug effects; D007694:Killer Cells, Natural / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D009368:Neoplasm Transplantation
D000954:Antigens, Surface; D007376:Interleukin-2; D002927:Cimetidine