Abstract
To enhance the effect of adoptive immunotherapy (AIT), we investigated the induction and characteristics of lymphokine activated killer (LAK) cells and also analyzed the combined effects of AIT with an antitumor drug (cyclophosphamide: CPA) in mice models. LAK cells were generated from C57/BL/6 (B6) spleen cells. The spleen cells were passed through a nylon wool column and cultured in RPMI-1640 medium containing 10%FCS and 2 X 103 units of human recombinant IL-2 (hr IL-2) for up to 14 days. During this period, the time kinetic analyses of the LAK cells' cytotoxicity and motility were performed. The cytotoxicities against Lewis Lung Carcinoma (3LL), evaluated by standard 51Cr release assay, gradually increased during the cultured period, and the motilities, determined by a modified version of the Boyden chamber method, greatly increased within the first 7 days' incubation. Based on these in vitro findings, we examined the efficacy of AIT alone or in combination with chemotherapy (CPA) in in vivo studies. MT was performed in the following way: LAK cells were intravenously infused and rlL-2 was intraperitoneally administered for 5 consecutive days following LAK cell administration. CPA was intraperitoneally administered. The therapy protocols were as follows. There were seven experimental groups. Group I; the mice were infused with 3-day cultured LAK cells (3DLAKs) on the second day after tumor inoculation (day 2). Group II; the mice were infused with 3DLAKs on day 5. Group DI; 10-day cultured LAK cells (10DLAKs) on day 2. Group IV; 10DLAKs on day 5. Group V (MT and CPA combination); AIT (10DLAKs) was started on day 5 followed by CPA on day 10. Group VI; CPA was performed on day 5 followed by MT (10DLAKs) on day 10. Group VII; CPA was performed on day 5 without MT. Each group consisted on 15 mice. The therapeutic efficacies were evaluated by calculating the median survival time of each group. The results of these experiments were as follows (mean SD) ; Group I's median survival time was 16.8 ±3.2 days, Group II 15.1 ±2.1 days, Group III 19.2 ±5.4 ±d ays, Group IV 16.1 ±4.8 days, Group V 23 ±6.3 days, Group VI 32 ±8.4 days and Group VII 22 ±5.1 days. These results suggested that the efficacy of MT is closely related to the LAK cells' cytotoxicity and motility. Although MT alone in the advanced tumor bearing host had a limited effect, combination with CPA improved it's efficacy. Thus, chemoimmunotherapy leads to a significant survival advantage in vivo. Our findings may enhance the efficacy of adoptive immunotherapy.
