Unbiased functional identification and therapeutic targeting of T cell neoantigens in a spontaneous murine squamous cell carcinoma [Bulk-seq]

ABSTRACT: The comparative resistance of some cancers including head and neck squamous cell carcinoma to checkpoint blockade is speculated to derive from the low frequency of expressed somatic mutations targeted by T cells as neoantigens. SCCVII, a spontaneously arising murine squamous carcinoma resembling human HNSCC in several key features, is likewise poorly immunogenic as irradiated tumor cells alone fail to induce protective immunity within syngeneic hosts. Justifying use of this model to identify NeoAgs, we confirm activated CD4+ and CD8+ T cells are detectable and essential for vaccine efficacy of SCC VII and polyI:C co-administration. Whole-exome sequencing tumor versus normal genome identified 39 nonsynonymous missense mutations that were synthesized into 81 representative 20-mers. NeoAg-specific CD4+ T cell IFN-γ responses were found against mutations of Pik3ca, Ctnnd1, and Otud5 while both CD4+ and CD8+ T cells produced IFN-γ when stimulated by a single Cltc mutation during in vitro recall assays. Prophylactic immunization with a mixture of all stimulatory peptides or the Cltc NeoAg alone protected hosts from subsequent tumor challenge. Further, the Cltc NeoAg, eliciting both CD4+ and CD8+ T cell responses, was also therapeutically beneficial in vivo. Anti-PD-1 combinatorial blockade resulted in synergistic tumor rejection via boosting Cltc-specific responses and increasing response diversification via epitope spreading. These data show that a functional NeoAg identification platform can be used to select immunotherapeutically relevant targets and filtration of neoepitopes that co-prime both CD4+ and CD8+ T cell responses is superior for practical intervention of poorly immunogenic tumors.

ORGANISM(S): Mus musculus

PROVIDER: GSE125048 | GEO | 2021/01/15

REPOSITORIES: GEO