PDCD1 and colorectal carcinoma: However, the efficacy of PD‐1 inhibitors varies across different phenotypes of CRC.[4] The clinical classification of CRC is mainly based on microsatellite instability (MSI‐H) and microsatellite stability (MSS).[5] PD‐1 inhibitors have demonstrated good therapeutic efficacy in 15% of all CRC patients exhibit MSI‐H (objective response rate, 53%).[4] However, the remaining 85% of patients with MSS CRC have almost no response to PD‐1 inhibitors.[6]