[Studies on lymphokine-activated killer (LAK) cell: accumulation in tumor tissue and the therapeutic effects of adoptive immunotherapy]

Abstract

We studied the therapeutic effects of adoptive immunotherapy with lymphokine-activated killer (LAK) cells combined with chemotherapy on BMT-11 fibrosarcoma in C57BL/6 mice. Compared with the untreated group, no significant therapeutic effect was brought about by CY therapy alone or LAK.rIL-2 alone and all mice belonging to these three groups died with a mean survival time (MST) of 45.3, 51.8 and 45.9 days respectively. CY plus LAK.rIL-2 brought about complete cures in 3 out of 8 mice (37.5%) and a significant prolongation of MST of mice which died (64.4 days) and the accumulation of LAK cells (% Dose/g) at tumor sites was enhanced more than 7-fold by combination with CY. On the other hand, the therapeutic effects of cytotoxic T lymphocytes (CTLs) was sufficiently high even in the CTL.rIL-2 alone and were only slightly enhanced by combination with CY compared with LAK cells. Also, we detected LAK-attractant activity in the conditioned medium (CM) of CY-treated tumor tissues but not in that of untreated tumor tissues, and peak activity was reached 5 days after CY-treatment. This attractant activity was located in two major 10,000-50,000 M. W. fractions of CM. We then observed that LAK-attractant was produced in CM of host reactive cell enriched fractions from CY-treated tumor tissues, but not in that of tumor cell enriched fractions. The above findings imply that the effects of adoptive immunotherapy depend upon the accumulation of transferred effector cells at tumor sites, and we believe that the production of LAK-attractant by tumor tissue, facilitated by chemotherapy, is one of the mechanisms responsible for enhanced LAK-cell-accumulation at tumor sites. We performed a preliminary clinical trial with adriamycin, autologous spleen-LAK cells and rIL-2 on 30 hepatocellular carcinoma patients after radical resection on the basis of the experimental results above. There were no significant therapeutic effects after adoptive immunotherapy during the postoperative course but tendency for temporary inhibition of recurrence. Thus it is shown that this method has probable value as effective adjuvant postoperative therapy.