Federica La Terza

Cross-presentation by type 1 DCs (cDC1) is critical to induce and sustain antitumoral CD8 T cell responses to model antigens, in various tumor settings. However, the impact of cross-presenting cDC1 and the potential of DC-based therapies in tumors carrying varied levels of bona-fide neoantigens (neoAgs) remain unclear. Here we develop a hypermutated model of non-small cell lung cancer in female mice, encoding genuine MHC-I neoepitopes to study neoAgs-specific CD8 T cell responses in spontaneous settings and upon Flt3L + αCD40 (DC-therapy). We find that cDC1 are required to generate broad CD8 responses against a range of diverse neoAgs. DC-therapy promotes immunogenicity of weaker neoAgs and strongly inhibits the growth of high tumor-mutational burden (TMB) tumors. In contrast, low TMB tumors respond poorly to DC-therapy, generating mild CD8 T cell responses that are not sufficient to block progression. scRNA transcriptional analysis, immune profiling and functional assays unveil the changes induced by DC-therapy in lung tissues, which comprise accumulation of cDC1 with increased immunostimulatory properties and less exhausted effector CD8 T cells. We conclude that boosting cDC1 activity is critical to broaden the diversity of anti-tumoral CD8 T cell responses and to leverage neoAgs content for therapeutic advantage.

Abstract The efficacy of immune checkpoint blockade (ICB) in NSCLC depends on the tumor mutational burden (TMB). However, a fraction of patients with high TMB and predicted immunogenic neoantigens (neoAgs) do not respond. Here we show that in a model of highly mutated NSCLC, cross-presenting cDC1s are required to induce broad effector CD8+ T cell responses to both strong and weak endogenous neoAgs. Importantly, cDC1 amplification by Flt3L increases immunogenicity of MHC class-I neoepitopes and promotes tumor regression, whilst PD-L1 blockade is ineffective. cDC1 density correlates to CD8+ T cell scores and prognosis, particularly in hypermutated human NSCLC. Single-cell RNA sequencing reveals the molecular determinants of Flt3L-therapy including expansion of immunogenic lung cDC1 and proliferation of cytotoxic CD8+ T cells with reduced exhaustion. We conclude that boosting cDC1 activity is critical to leverage neoAgs content for therapeutic advantage in hypermutated lung tumors that do not respond to ICB.

Abstract Cross-presentation by type 1 cDCs (cDC1) is critical to induce and sustain antitumoral CD8 T cell responses to model antigens, in various tumor settings. However, the impact of cross-presenting cDC1 and the potential of DC-based therapies in tumors carrying varied levels of bona-fide neoantigens (neoAgs) remains unclear. Here we generated a non-small cell lung cancer model with distinct ranges of TMB and MHC-I neoepitopes to test immunogenicity and response to Flt3L+αCD40 (DC-therapy). We found that cDC1 are required to broaden the pattern of CD8 responses to basal and acquired neoAgs and DC-therapy strongly inhibits the growth of TMB high tumors. In contrast, TMB low tumors induce weaker responses that are not sufficient to block progression. scRNA transcriptional analysis, immune profiling and functional assays show that DC-therapy triggers the accumulation of lung cDC1 with increased immunostimulatory properties and CD8 T cells with enhanced cytotoxic functions and reduced exhaustion, most prominently in neoAgs high tumors. We conclude that boosting cDC1 activity is critical to broaden the diversity of anti-tumoral CD8 T cell responses and to leverage neoAgs content for therapeutic advantage.