PD-1/PD-L1 immune check points blockade to attenuate growth of metastatic colon cancer in the CBP/β-catenin inhibited liver.

556Background: Immune check points blockade with specific antibodies can accelerate anti-tumor immunity, resulting in a clinical response in patients with various types of cancer. Thus, a wide variety of treatment combinations based on PD-L1/ PD-1 pathway blockage are under development to enhance the therapeutic effect. Here, the effects of the combination treatment of PRI-724, a selective inhibitor of the CBP/β-catenin, with anti-PD-L1 antibody were examined in a mouse model of the liver metastasis of colon cancer. Methods: Mice were inoculated with SL4 colon cancer cells into the spleen to produce metastatic liver tumors. The animals were intraperitoneally injected with or without PRI-724 and/or anti-PD-L1 antibody (10F.9G2) 3 times a week. A part of mice treated with PRI-724 and anti-PD-L1 antibody was administrated with anti-mouse CD4 or CD8 antibody 3 times a week. First, to evaluate anti-tumor effect in those mice, we analyzed liver histology and survival rates after treatment. Next, to examine immu...