Enhancing T cell immunity in the breast tumor microenvironment via localized ablative immunotherapy: insights from single-cell RNA sequencing

Metastatic breast cancer is challenging to treat due to the immunosuppressive tumor microenvironment (TME) and limited immune checkpoint inhibitor efficacy. We investigated localized ablative immunotherapy (LAIT), combining photothermal therapy with intratumoral N-dihydrogalactochitosan, in the MMTV-PyMT mouse model. Single-cell RNA sequencing and flow cytometry showed that LAIT increased tumor-infiltrating CD8⁺ and CD4⁺ T cells, driving naïve and memory subsets into activated states with elevated co-stimulatory molecules, interferon-responsive genes, and pro-inflammatory cytokines, while reducing immunosuppressive mediators. Cell–cell interaction analysis revealed enhanced IL16, TNF, and MHC-I/II signaling and decreased TGFβ and PD-L1 pathways. LAIT-specific T cell gene signatures correlated with longer overall survival in breast cancer patients, supporting its potential to remodel the TME and synergize with immune checkpoint blockade.