[Strategy of cancer treatment using human recombinant interleukin 2 and lymphokine activated killer cells]

There are two strategies for evaluating the antitumor effect of IL-2. In the first approach IL-2 has been used to support the proliferation of T-effector cells or LAK cells in vitro in the hope that large quantities of these effector cells can be used therapeutically. This approach has shown some efficacy in animal models if LAK cells are administered in combination with IL-2. However, it is extremely difficult to standardize the numbers of lymphocytes and the biological activity of effector cells for clinical use. Recently the cloning of IL-2 has made available large quantities of purified recombinant IL-2 (rIL-2) for preclinical and clinical trials. Accordingly there have been recent attempts at injecting rIL-2 directly to stimulate effector cells in vivo. In this study, in vivo and in vitro augmentation of the cytotoxicity of spleen lymphocytes against syngeneic B-16 melanoma cells (induction of LAK cells) and the suppression of artificial pulmonary and liver metastases of B-16 melanoma in C57BL/6 mice was tried by subcutaneous multiple injections of high-dose human rIL-2. In addition, the immunosuppressive effect of a water-soluble nitrosourea derivative (ACNU) was determined in terms of the cytotoxicity of spleen lymphocytes, and the restoring effect of lymphokine-activated killer (LAK) cells and/or human recombinant interleukin-2 (rIL-2) on the cytotoxicities of spleen lymphocytes were examined in ACNU-treated C57 BL/6 mice. It was also tested whether the administration of LAK cells and/or rIL-2 could reduce the increased numbers of pulmonary metastases in ACNU-treated mice. The cytotoxicity of spleen lymphocytes against YAC-1 cells as well as against syngeneic B-16 and F-10 melanoma cells was augmented not only by incubation of spleen lymphocytes with human recombinant interleukin-2 (rIL-2) in vitro but also by injecting high-dose rIL-2 into C57BL/6 mice for more than 3 consecutive days. In animals injected with multiple high doses of rIL-2 subcutaneously, the numbers of tumor nodules in the lung were significantly decreased 21 days after intravenous tumor inoculation. In addition, in these groups of animals no liver metastases were observed although liver metastases were detected in 6/11 of control mice. The maximum effective dose of ACNU suppressed the cytotoxicity of spleen lymphocytes and pretreatment with ACNU enhanced the induction of artificial pulmonary metastases.(ABSTRACT TRUNCATED AT 400 WORDS)