In an aggressive spontaneous murine model of breast cancer (MMTV-PyMT), in which TAMs were also the major tumoral source of HO-1, an influx of T-cells into the TME were generated using the immune-stimulating CCT 5-fluorouracil (5-FU) which synergized with pharmacological inhibition of HO using SnMP to alleviate immune suppression and permit CD8+ T-cell dependent control of tumor growth (2). The gene discussed is CD8A; the disease is breast carcinoma.