Targeting IL27RA Enhances Immunotherapy in Triple‐Negative Breast Cancer by Modulating Tumor Cells and the Tumor Microenvironment

Immune checkpoint blockade (ICB) has improved outcomes for patients with triple-negative breast cancer (TNBC), yet resistance remains widespread and its molecular basis is not fully understood. Through single-cell RNA sequencing (scRNA-seq) of paired pre- and post-treatment tumor samples from patients who failed to achieve pathological complete response (non-pCR) after neoadjuvant PD-1 therapy, we identified a marked upregulation of interleukin-27 receptor subunit alpha (IL27RA) in malignant epithelial cells within residual lesions. Integration with scRNA-seq profiles from an independent cohort of three pCR patients showed that this IL27RA upregulation in malignant epithelium is largely restricted to non-pCR residual tumors, and high IL27RA expression correlated with poor survival in TNBC cohorts. Mechanistically, IL27RA suppresses MHC-I expression by activating the PI3K/AKT pathway-rather than the classical IL-27/STAT axis-thereby impairing CD8⁺ T-cell cytotoxic function. Inhibition of AKT reversed this phenotype and restored antigen-specific killing. In orthotopic tumor models, mimicking systemic loss of Il27ra significantly reduced tumor growth and prolonged survival in immunocompetent mice, with single-cell profiling indicating enhanced intratumoral T-cell and NK-cell effector activity. Collectively, our findings identify an epithelial-intrinsic IL27RA-PI3K/AKT-MHC-I axis as a central driver of immune evasion and ICB resistance in TNBC and support IL27RA as a promising therapeutic target for overcoming immunotherapy resistance.