Arsenic trioxide is an immune adjuvant in liver cancer treatment.

Tumor cells are inhibited effectively by As2 O3 in vitro and in vivo, although the underlying immune regulatory mechanisms remain unknown. Regulatory T cells play a key role in tumor immune escape. In the present study, we aimed to assess the in vivo effects of As2 O3 on the immune status in hepatic cancer and its in vitro regulatory role in cytokine-induced killers(CIKs)cytotoxicity. In a tumor H22 xenograft model of hepatic cancer, we demonstrated that As2 O3 treatment decreased tumor volumes and weights, and improved survival by reducing Tregs infiltration into the tumor. Moreover, our data indicated that the exact immune regulatory mechanism of As2 O3 might involve elevated CD3+T lymphocyte amounts more than reduced Tregs levels. Furthermore, As2 O3 significantly improved CIKs cytotoxicity in vitro by decreasing CD4+T lymphocytes and Tregs, and increasing CD8+T lymphocytes. Our results suggested that As2 O3 might act as an immune adjuvant in liver carcinoma treatment by increasing T lymphocytes and decreasing Treg infiltrated into the tumor.