The ultimate goal of this proposal is to develop agents to increase the efficacy of immunotherapy of malignant melanoma. The studies in this proposal involve a proof-of-principle combination immunotherapy protocol in a mouse model, using drugs to increase antigen expression and tumor targeting by adoptively transferred T cells specific for tumor antigens. As a product of a screening assay to identify compounds that enhance tumor antigen expression while allowing T cell function, we identified an enzyme inhibitory drug that increased melanoma antigen and MHC Class I expression in a panel of melanoma and glioma cell lines. As a follow-up to in vitro assays showing better T cell recognition of human tumors that were treated with the compound, we propose to exploit a mouse model melanoma for evaluation of combination in vivo therapy by adding the antigen-enhancing drug to adoptively transferred antigen-specific (TRP2 antigen presented on H2-Kb) T cells. The addition of the antigen enhancer to the treatment protocol will allow us to determine if we can first achieve enhanced antigen expression in an animal. We have confirmed in vitro that the mouse melanoma does respond to drug treatment with increased TRP2 and H2- Kb antigen expression. We will extend these in vitro studies with in vivo determinations of the doses needed for in vivo enhancement of antigen expression. From an analysis of a panel of related drugs, we will select a single best candidate for use in the combination therapy model to test whether pre-treatment with the antigen enhancer will make tumors more susceptible to immune cell targeting and destruction. The identification of a new drug that enhances immune-recognition is of great potential benefit for cancer therapy. If we are successful at demonstrating that the compounds are stimulatory to tumor antigen recognition in vivo, these murine studies will be invaluable in the design and implementation of human clinical trials using combination of antigen-enhancing drug and immunotherapy. The large number of related compounds that have proved safe for human in the treatment of a variety of diseases suggests that the class of antigen enhancing drugs we will evaluate could be highly beneficial in synergy with effective anti-tumor immunity.
We propose to use a mouse model to perform a combination cancer therapy that involves the use of drugs that we have found to increase targeting of tumor cells, together with immunotherapy that we hope to show will allow better tumor killing. The cancer we will treat is melanoma, a highly malignant cancer of pigmented cells that is highly resistant to conventional cancer therapies (irradiation and chemotherapy). We have already shown that tumors in cell culture can be recognized better after they are treated with the antigen enhancing drugs we propose to test in a mouse model that will provide proof-of-principle for eventual human therapy of melanoma. Melanoma has increased dramatically in the past 50 years, particularly as northern European peoples have migrated to more tropical locations, leading to epidemic increases in sun-damage related skin cancers, with striking increases in the highly lethal melanomas. There is increasing evidence that targeting melanoma cells with immune therapies can be beneficial in a small percentage of the treated patients, and that strategies to improve tumor targeting could provide a breakthrough in resistant tumors.