Loss of SHP-1 in CD11c+ cells impairs anti-tumor immunity

Background Tyrosine kinases and phosphatases regulate protein phosphorylation and maintain cellular homeostasis. The phosphoprotein tyrosine phosphatase SHP-1 (encoded by the Ptpn6 gene) has been proposed as an immune checkpoint in CD8 + T cells in preclinical models, yet its pharmacological inhibition has shown no efficacy against tumor growth in clinical trials. This suggests that SHP-1 may play opposing roles in different cell types within the tumor microenvironment. Here, we investigated the effect of depleting SHP-1 in CD11c + cells on the anti-tumoral response. Methods To dissect the specific role of SHP1 in CD11c + antigen-presenting cells, or specifically in conventional type 1 dendritic cells (cDC1s) or macrophages, we subcutaneously inoculated different tumors in ItgaxΔPtpn6 , Xcr1 Δ Ptpn6 and Lyz2 Δ Ptpn6 mice, respectively. Tumor growth and survival were monitored, and immune infiltrates were analyzed using flow cytometry or scRNA-seq. Results Tumor rejection was impaired when SHP-1 was depleted in CD11c + cells, as well as in XCR1 + or Lyz2 + cells. scRNA-seq analysis revealed that both tumor-associated macrophages and cDC1s exhibited downregulation of interferon response pathways in tumor-bearing ItgaxΔPtpn6 mice compared with controls. Reduced MHC-II expression in tumor-associated macrophages was validated by flow cytometry, supporting impaired antigen presentation in these cells, whereas cDC subsets displayed heterogeneous alterations in co-stimulatory marker expression rather than a defect. Consistent with these findings, flow cytometry analysis showed that ItgaxΔPtpn6 mice injected with MC38 tumor and treated with anti-PD1 displayed a reduction in CD8 + IFN-γ cells in comparison with Ptpn6 f/f littermates. Conclusions These results show that SHP-1 depletion in CD11c + cells impairs anti-tumor immunity and suggest that both cDC1s and macrophages contribute to this effect.