A new clinical-translational study found that combining anti‑PD‑1 immunotherapy with chemotherapy induces profound cellular reprogramming in early-stage, hormone-receptor–positive (HR+) breast cancer. Researchers analyzed tumor tissue before and after treatment and documented shifts in tumor cell states and immune microenvironment composition. The lead finding is a treatment-driven change in cell phenotypes—suggesting adaptive remodeling of tumor and stromal compartments when immunotherapy is added to standard cytotoxic regimens. The authors detail single-cell and bulk transcriptomic evidence linking therapy to altered antigen-presentation and immune infiltration patterns. The results raise practical questions for trial design in HR+ disease—historically less immunogenic than triple-negative breast cancer—including timing of immunotherapy, biomarker selection, and whether reprogramming correlates with long‑term outcomes. Larger randomized studies will be required to validate whether the observed cellular shifts translate to improved recurrence-free survival.