Taken together, the PI3K inhibitor ZSTK474 at the intermediate dose (100 mg/kg) decreases Tregs and increases antitumor CD8+ T cells, and the antitumor CD8+ T cell responses are further augmented by pretreatment with anti-PD-1 mAb, resulting in a far stronger tumor growth inhibition by the combination treatment. The gene discussed is PDCD1; the disease is neoplasm.