In a small-scale screening using seven FDA-approved drugs in a genetically engineered mouse model of breast cancer, we previously described the earliest cellular events of induced anti-tumor immunity and found a pan-histone deacetylase (HDAC) inhibitor, panobinostat, that induces ICD, recruits CD8 T cells inside the tumor bed, and synergizes with the anti-PD-1 monoclonal antibody to decrease the tumor burden [1]. Here, HDAC9 is linked to breast cancer.