Adoptive immunotherapy using lymphokine-activated killer cells and recombinant interleukin-2 in preventing and treating spontaneous pulmonary metastases of syngeneic Dunning rat prostate tumor.

Lymphokine-activated killer (LAK) cells were generated from splenocytes of rats bearing a weakly immunogenic Dunning prostate tumor (R-3227 AT-3) and activated with recombinant interleukin-2 (rIL-2). The maximal LAK activity was obtained from splenocytes of rats bearing tumors for 10 to 14 days after incubation with 1000 U/ml./day of rIL-2 for five to eight days. The majority of these LAK cells expressed high levels of asialo GM1 (89%), laminin (83%), OX-19 (80%) and OX-8 (88%) surface markers. LAK cells exhibited higher cytotoxicity to rat prostate tumor cells and mouse lymphoma in vitro than to other non-prostate tumor cells or normal rat splenocytes and thymocytes. Splenocytes of rats bearing prostate tumors have higher LAK activity than normal splenocytes. The Winn type assay showed that Dunning prostate tumor growth was inhibited effectively by LAK cells at a tumor cell:LAK cell ratio of 1:50. The therapeutic efficacy of LAK cells in the treatment of primary solid prostate tumors and pulmonary metastases of Dunning rats was evaluated. LAK cells in combination with rIL-2 showed a greater therapeutic benefit in 1) prevention of prostate tumor metastases to lung, 2) retardation of the primary tumor growth, 3) regression of spontaneously established pulmonary metastases, and 4) prolongation of survival as compared to untreated controls or those groups treated with LAK cells or rIL-2 alone. The results of this study indicate that the conjunctive therapeutic approach of using surgical therapy to remove primary solid tumors followed by adoptive immunotherapy with LAK cells plus in vivo administration of IL-2 may be potentially valuable in the treatment of prostate tumors, particularly for the spontaneous pulmonary metastases.