Genetic linkage analysis identifies SNX3 as a regulator of antigen cross-presentation during anti-tumor antibody therapy 2309751

Introduction Trastuzumab, an anti-HER2 targeted immunotherapy (ITx), has changed the landscape of HER2+ breast cancer survival, but drug resistance and disease recurrence still present a problem. Patients who develop anti-tumor immunity after targeted ITx show improved long-term benefit, but host-intrinsic mechanisms regulating immune priming remain unclear. Methods (Diversity OutbredxBALB/c)F1 (DOF1) mice bearing HER2/neu+ TUBO mammary tumors were treated with anti-HER2/neu mAb 7.16.4. Genetic linkage analysis was performed in R/qtl2 to identify loci associated with response and select Collaborative Cross (CC) mouse models with driver genetics. scRNAseq was performed on CD45+ TUBO infiltrates from CCF1 mice. To measure cross-presentation, DC2.4 dendritic cells were transduced with shSNX3 or control lentiviruses and cocultured with TUBO cells expressing ovalbumin (OVA) prior to the addition of OVA-specific OT-I CD8 T cells. scRNAseq was performed on 46 trastuzumab-treated HER2+ breast cancer samples (∼60% responders) collected prior to therapy. Results We find that host genetic background influences endogenous immune priming after targeted ITx in mice. DOF1 TUBO-bearing mice exhibited differential response to 7.16.4 treatment; ∼45% of mice eliminated primary tumor with protection against contralateral rechallenge. Genetic linkage analysis and tumor immune infiltrate scRNAseq identified SNX3 as a potential regulator of response to targeted ITx. We observed increased OT-I activation in the presence of DC2.4/shSNX3, suggesting SNX3 negatively regulates antigen cross-presentation. Supporting this hypothesis, our human breast cancer scRNAseq dataset showed an inverse correlation of trastuzumab response with dendritic cell SNX3 expression. Conclusion We demonstrate that genetic background influences response to targeted ITx and identify SNX3 as a regulator of response through antigen presentation to CD8 T cells. Future studies aim to leverage SNX3 as a novel actionable gene to improve targeted ITx outcomes.