Adoptive therapies: quo vadis?

The success of adoptive immunotherapy using interleukin-2 (IL-2) and lymphokine-activated killer (LAK) cells in treating a percentage of patients with melanoma and renal cell carcinoma has provided impetus to research into both how to optimize this treatment as well as approaches into making immunotherapy in general more successful. As the question on how to optimize IL-2 dose, schedule, cell culture conditions, and other specifics of IL-2 plus LAK therapy are addressed in clinical trials, other approaches suggested by data from in vitro, animal, and the clinical studies using IL-2 are emerging into clinical trials. (table; see text) These include two major areas of focus at the present time: (1) the use of IL-2 +/- LAK in combination with a variety of agents which have been shown to be synergistic with it, including other biological response modifiers (such as interferons), agents which may act both as interferon inducers as well as by other mechanisms (poly-IC:LC and flavone-8-acetic acid), and chemotherapeutic agents (especially cyclophosphamide, doxorubicin and agents which have some activity against the disease being treated such as DTIC for melanoma), and (2) various approaches aimed at inducing and expanding tumor-specific immune cells which appear to have greater antitumor activity than LAK cells and which may be major contributors to the antitumor efficacy of IL-2 therapy. These approaches also have the potential benefit of inducing memory cells with a resultant long-term immune antitumor response. Approaches aimed at activating specific antitumor immune cells include the use of IL-2-expanded infiltrating lymphocytes from tumors, exposure of peripheral blood cells cultured in IL-2 to tumor cells to hopefully expand those with a specific antitumor response, and the use of tumor cell vaccines in conjunction with IL-2. In addition to approaches using activated and expanded LAK effectors or specific T cells, the potential role of activated (e.g. by gamma interferon) and expanded (e.g. by macrophage colony stimulating factor) macrophages in the adoptive immunotherapy of cancer remains an area of ongoing exploration both in preclinical studies and clinical trials. As a greater understanding of the antitumor mechanisms of IL-2 and LAK therapy and other forms of adoptive immunotherapy is achieved, therapeutic approaches can be defined which will maximize the ability to mediate the immune destruction of tumor cells.(ABSTRACT TRUNCATED AT 400 WORDS)