Interleukin-2 and cancer therapy

In summary, this meeting provided a useful overview of state-of-the-art research on IL-2. Significant gains have been made toward understanding the molecular biology and function of IL-2 and its receptors, but much remains to be learned about the intracellular signaling pathway by which IL-2 transduces its biological effects. Likewise, the nature of the lymphocyte subpopulation that responds to IL-2 requires detailed study, since it is now clear that T cells as well as LGLs can mediate non-MHC-restricted killing of tumor cells. Cell trafficking and effector cell activity within the tumor are other important issues to address. We also need to define the mechanism(s) by which IL-2-activated lymphoid cells mediate their antitumor effect in vivo; it is still far from clear whether these cells directly lyse the tumor cells, interrupt the tumor's vascular supply through endothelial cell damage, or produce other cytokines which then activate other cellular pathways. Preclinical data indicate that IL-2, with or without adoptive cellular therapy or in combination with other cytokines or drugs, can cause tumor regression. The success with animal model systems, however, has not always translated to success in the clinical setting-disappointingly, the majority of cancer patients still fail to respond to this treatment. It is hopeful the reasons for this will become apparent as more is learned about the molecular and cellular mechanisms involved in this "new" form of immunotherapy.