Augmentation of interleukin-2 immunotherapeutic effects by lymphokine-activated killer cells and allogeneic stimulation in murine tumor cells

Interleukin-2 (IL-2) and lymphokine-activated killer (LAK) cells were used in intraperitoneal and pulmonary tumor models in C57BL/6 mice. To maintain the immmunotherapeutic effects of IL-2 plus LAK treatment but reduce its toxicity, ways were sought to augment IL-2 effects. The investigation showed that the adoptive transfer of LAK cells was a prerequisite for successful therapy of intraperitoneal cancer. When LAK cells were given on consecutive days within one course of immunotherapy, antitumor efficacy was augmented with additional doses of LAK cells. However, with the reduction of 1 complete cycle of IL-2 + LAK cells, no further reduction in intraperitoneal tumor was observed as compared to the reduction after 2 or 4 cycles. LAK cells generated from splenocytes of mice that had received an allogeneic tumor challenge 1 week earlier exerted a highly increased cytotoxicity as compared to normal LAK cells. Furthermore, the potentiation effect of an allogeneic response of the host at the tumor site was demonstrated by decreased numbers of lung implants and improved survival in mice given mixtures of syngeneic and allogeneic tumor cell suspensions. An alloimmune response within the microenvironment of tumor tissue markedly enhanced the antitumor effect of IL-2 against the syngeneic tumor. It was concluded that there is a fundamental need to improve the recruitment of adoptively transferred LAK cells or LAK precursors into tumor tissue. This may be the next step required in the further development of IL-2 and LAK immunotherapy.