of Research ActivitiesI. Development of cell transfer immunotherapies for the treatment of patients with cancerCell transfer therapies have a variety of advantages compared to other approaches. It is possible to administer large numbers of highly selected cells with high avidity for tumor antigens, the cells can be activated ex vivo to exhibit anti-tumor effector function and thus do not depend on activating stimuli at the tumor site, the exact cell subpopulations and effector functions that are required for cancer regression in vivo can be identified, and it is possible to manipulate the host prior to cell transfer to provide an alternate environment for the transferred cells. The studies we are currently performing fall into three general categories:a. Lymphodepletion prior to cell transfer: Prior lymphodepletion of the host serves both to eliminate """"""""regulatory"""""""" or """"""""suppressor"""""""" cells that can inhibit anti-tumor reactions and also provides for improved homeostatic proliferation of the transferred cells. The combined administration of CD8+ and CD4+ cells also appears to play an important part in this approach to therapy. We have recently published an approach to cell transfer therapy that can mediate substantial cancer regressions in patients with metastatic melanoma that are refractory to treatment with high dose IL-2 and chemotherapy. A clonal repopulation can occur resulting in over 75% of circulating CD8+ cells that are tumor reactive and this is associated with regression of substantial tumor volumes in vivo.b. Gene modification of transfer T cells: Laboratory studies are identifying important properties of T cells that are required for anti-tumor activity. Transduction of the gene for IL-2 into T cells has resulted in T cells capable of growing in vitro in the absence of IL-2. We have now begun a clinical trial utilizing the transfer of IL-2 gene modified cells. Additional studies are in progress to introduce, into T cells, genes encoding T cell receptors with high avidity for tumor antigens and the genes for interleukin-7 or interleukin-15. Studies of the biologic properties of these cells will then determine whether to utilize them in clinical protocols.II. Development of cancer vaccinesImmunization of cancer vaccines against cancer antigens is an active area of investigation. Our studies in this area are divided into several categories. a. Antigen discovery utilizing tumor infiltrating lymphocytes: Over two dozen tumor antigens have now been discovered by our group. In the past two years new antigens with potential for use in cancer vaccines have been identified including BING-4, SOX-10, new class II epitopes from the TRP-1 antigen, new class II epitopes from the ESO-1 antigen, a new isoform of the TRP-2 antigen and a variety of mutated antigens including NOP-56, A-11, and p14-ARF.b. Evaluation of cancer vaccines: Clinical studies are underway to evaluate the ability to immunize cancer patients including the use of immunodominant peptides as well as recombinant viruses. We have recently shown that fowlpox viruses encoding the gp100 melanoma antigen with appropriate modification of HLA-A2 binding anchor residues is an effective immunogen in patients with melanoma. In the adjuvant vaccine setting which enables immunization with peptides for up to 48 weeks, levels of anti-tumor T cell precursors can be induced to levels of 2-5% which is higher than that seen in any other cancer vaccine study.
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