Expression profiling of mouse melanomas with or without UVB-induced neoantigens and after combination immunotherapy

Syngeneic grafts of the D4M.3A.3 (parental) mouse melanoma cell line (derived from a Tyr::CreER;BrafCA;Ptenlox/lox mouse) in C56BL/6 mice model poorly immunogenic, low neoantigen human melanomas. The D3UV2 (UV2) cell line was derived by serial UVB irradiation and single cell cloning. The addition of UVB-induced putative neoantigens sensitizes UV2 syngeneic melanoma grafts to immune checkpoint inhibitors and triggers epitope skewing to tumor-lineage self-antigens, a phenomenon that can be successfully mimicked in parental melanomas through treatment combinations such as anti-PD-1 with ablative fractional photothermolysis and imiquimod. Our mouse models were used to characterize gene expression changes between neoantigen rich and neoantigen poor melanomas, and with immunotherapy. RNA-sequencing was performed to study gene expression changes in bulk tumors after addition of UVB-induced putative neoantigens (parental vs. UV2 melanomas) or treatment with anti-PD-1 or combination immunotherapy (anti-PD-1 + ablative fractional photothermolysis + imiquimod).