Abstract
Abstract Despite significant improvements in cancer immunotherapies, enhancing immunogenicity of non-responsive tumors warrants further investigation. A prior drug screen of ~3,000 compounds identified NU7441, a DNA PK inhibitor, as an effective compound that promotes immunogenicity of various melanoma lines in vitro. In this study, we hypothesized that in vivo combination therapy NU7441, STING-L, and CD40 agonist will enhance tumor immunogenicity resulting in both expansion and increased cytotoxic activity of CD8+TCRβ tumor-reactive TILs in B16 melanoma models. Results obtained by flow cytometry demonstrated that combination treatment 1) significantly increased the ratio of CD8/CD4 TILs, 2) expanded several tumor-reactive TCRβ clones, 3) increased granzyme B production and expression of 4-1BB and PD-1, 4) increased ratio of DC/MDSC infiltration, and 5) potentially identified a novel cytotoxic CD8+CD11c+GR-1+ population. Additionally, the expansion of tumor-reactive TCRs was attributed to DNA-PKi’s ability to both expand and diversify the number of neoantigen transcripts resulting in a broader neoantigen expression profile. RNA-seq identified 27 unique neoantigens as potential novel targets in melanoma immunotherapy. TILs isolated from B16 tumors were co-cultured with dendritic cells transfected with tandem-mini genes, each encoding ~10 neoantigens, and T cells were analyzed by flow cytometry to quantify the TCRβ repertoire and functional response to neoantigens. We demonstrate combination treatment with NU7441, STING-L and CD40 agonist enhance antitumor responses through increased myeloid cell infiltration and sensitization of tumor cells to T cell-mediated killing from an expanded CD8+TCRβ repertoire. Supported by R01CA207913 NCI BX004935-01, VA, Merit Award P30CA046934, NCI Leukemia and Lymphoma Society Department of Defense Gates Grubstake University of Colorado Anschutz Medical Campus Cancer League of Colorado
Published Version
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