Data from One CD4⁺TCR and One CD8⁺TCR Targeting Autochthonous Neoantigens Are Essential and Sufficient for Tumor Eradication

AbstractPurpose: To achieve eradication of solid tumors, we examined how many neoantigens need to be targeted with how many T-cell receptors (TCR) by which type of T cells. Experimental Design: Unmanipulated, naturally expressed (autochthonous) neoantigens were targeted with adoptively transferred TCR-engineered autologous T cells (TCR-therapy). TCR-therapy used CD8⁺ T-cell subsets engineered with TCRs isolated from CD8⁺ T cells (CD8⁺TCR-therapy), CD4⁺ T-cell subsets engineered with TCRs isolated from CD4⁺ T cells (CD4⁺TCR-therapy), or combinations of both. The targeted tumors were established for at least 3 weeks and derived from primary autochthonous cancer cell cultures, resembling natural solid tumors and their heterogeneity as found in humans. Results: Relapse was common with CD8⁺TCR-therapy even when targeting multiple different autochthonous neoantigens on heterogeneous solid tumors. CD8⁺TCR-therapy was only effective against homogenous tumors artificially derived from a cancer cell clone. In contrast, a combination of CD8⁺TCR-therapy with CD4⁺TCR-therapy, each targeting one neoantigen, eradicated large and established solid tumors of natural heterogeneity. CD4⁺TCR-therapy targeted a mutant neoantigen on tumor stroma while direct cancer cell recognition by CD8⁺TCR-therapy was essential for cure. In vitro data were consistent with elimination of cancer cells requiring a four-cell cluster composed of TCR-engineered CD4⁺ and CD8⁺ T cells together with antigen-presenting cells and cancer cells. Conclusions: Two cancer-specific TCRs can be essential and sufficient to eradicate heterogeneous solid tumors expressing unmanipulated, autochthonous targets. We demonstrate that simplifications to adoptive TCR-therapy are possible without compromising efficacy.