Abstract 4741: Therapeutic efficacy of a human-derived antibody against cancer-testis antigen NY-ESO-1

2011
Rationale: It is accepted that the immune system can control cancer and a favorable clinical course correlates with high infiltration by CD8+ T cells in different cancer entities. Thus, boosting cancer-specific immunity is an interesting therapeutic modality. Cancer-testis antigens(CTA) are promising target antigens due to their tumor-restricted expression pattern and high immunogenicity. NY-ESO-1is one of the best characterized CTA, and spontaneous anti- NY-ESO-1humoral and cellular responses were described in patients with various cancers. We propose that antibodies (Abs) against intracellular CTA have therapeutic potential because they may facilitate the uptake and presentation of antigens by dendritic cells (DC), which supports cancer-specific T cell responses. This effect may be more pronounced when Abs are used in combination with therapies that result in death, and thus antigen release, of cancer cells. We report here the characterization of the first human anti- NY-ESO-1monoclonal Ab. Methods: Human-derived monoclonal Ab 12D7 was obtained by molecular cloningfrom memory B cellsof a melanoma patient, ZH-311. To characterize the binding of 12D7 we performed ELISA, Biacore analysis and tissue staining. In addition, we used 12D7 to immunoprecipitate native NY-ESO-1from human melanoma cell line SK-MEL-37. As a proof of concept, we compared the activation of NY-ESO-1-specific CD8+ T cell clones by DC fed with NY-ESO-1vs. NY-ESO-1/12D7 immune complexes (IC) in vitro. To determine the therapeutic effect in vivo, we treated BALB/c mice bearing syngeneic CT26/ NY-ESO-1colorectal tumors with 5-FU +/- 12D7. To investigate Ab accumulation in established tumors 12D7 was labeled with FITC and injected into mice 2 days after 5-FU treatment. Results: Human monoclonal 12D7 specifically bound to NY-ESO-1with high affinity (pM range) and precipitated endogenous NY-ESO-1from SK-MEL-37. The uptake and cross-presentationof NY-ESO-1by DC was greatly enhanced when NY-ESO-1was complexed with 12D7 before feeding. Importantly, uptake of NY-ESO-1/12D7 IC, but not NY-ESO-1, resulted in maturation of DCs as determined by upregulation of co-stimulatory molecules. Finally, 12D7 significantly improved the therapeutic efficacy of 5-FU treatment in established CT26/ NY-ESO-1tumors. Ab accumulation in CT26/ NY-ESO-1tumors was enhanced when mice were treated with 5-FU as compared with untreated mice. Conclusion: We propose that the release of intracellular tumor antigensby chemotherapy and the accumulation of Ab to such antigens results in the local formation of IC. These IC are efficiently cross-presentedto tumor-specific CD8+ T cells by DCs and may induce in situ maturation of the latter, both of which support tumor-specific effector function and thus contributes to tumor control. Our results suggest that targeting intracellular antigens, more specifically CTA, with Abs is a useful strategy for cancer treatment. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4741. doi:10.1158/1538-7445.AM2011-4741
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