Microsatellite stable (MSS) colorectal cancers represent 95% of all metastatic colorectal cancer cases and are characterized by low tumor mutation burden (TMB) and low immune infiltration compared with microsatellite instability–high (MSI-H) colorectal tumors.1 As a result, programmed cell death receptor 1/programmed cell death ligand 1 (PD-1/PD-L1) inhibition has led to robust clinical benefit in MSI-H colorectal cancers, whereas limited antitumor activity has been observed in colorectal cancers with MSS.2,3,4,5. The gene discussed is CD274; the disease is colorectal cancer.