IL2 and cancer: Also, it was observed that IL-2 has a dynamic variation in BC pathogenesis and affects the circulation of tumor cells in patients with advanced BC,30 while the level of IL-2 and the circulation of tumor cells have a reverse correlation in BC patients Although IL-2 can be used as monotherapy, its combination with some anti-cancer immunotherapies, e.g., antigen-specific vaccination, adoptive cell transfer, chimeric antigen receptor (CAR) T cell therapy, and immune checkpoint blockade has led to promising therapies.31