PDCD1 and breast carcinoma: However, it is notable that while a high-dosage (250 μg/mouse of anti-PD-1 antibody) PD-1 blockade was capable of enhancing the antitumor activity of anti-HER2 CAR-T cells in a syngeneic breast cancer model [42], the antibody failed to inhibit tumor growth or enhance the antitumor efficacy of CAR-T cells at a low dose (125 μg/mouse) [45].