Clinicopathological analysis of PD-L2 expression in colorectal cancer

(PD-L2), a ligand of programmed cell death protein 1 (PD-1), is an inhibitory receptor of T cells and activated B cells. Many studies have focused on PD-L1, another ligand of PD-1, and the prognostic significance of PD-L1 has been reported in many tumors. However, the expression of PD-L2 in relation to clinical outcomes has not been fully investigated in cancer patients. In this study, we investigated the expression of PD-L2 via immunohistochemistry (IHC) in the pathological specimens of 348 patients treated for colorectal cancer (CRC). Strong PD-L2 expression was found in the cancer tissues from 41% of the CRC patients who also had a high TNM stage and carcinoembryonic antigen (CEA) concentration. We also carried out functional studies in vitro, which showed that PD-L2 did not influence the growth of the CRC cell line HCT116, but increased cell invasion. Collectively, these findings suggest that PD-L2 may be a potential therapeutic target for CRC.