PD-1 and PD-L1 expression was significantly elevated in cluster 1, and immune checkpoint inhibitors targeting them had been applied in the treatment of solid tumors such as cutaneous malignant melanoma, non-small cell lung cancer and colorectal cancer.[5,14,15] Immune checkpoint inhibitors targeting the CTLA4 gene had also shown efficacy in cutaneous malignant melanoma.[16] The study of Durante et al[17] indicated that in UM, tumor-infiltrating immune cells, including CD8 + T cells, predominantly expressed the checkpoint marker LAG3, rather than PD-1 or CTLA4. Here, PDCD1 is linked to colorectal cancer.