CD274 and colorectal cancer: Due to unstable and hyper-mutational nature, colorectal cancers with MSI-H profile also tend to express high level of checkpoint proteins, including programmed death 1 (PD-1) and programmed death ligand 1 (PD-L1) [45], which makes MSI-H tumors more responsive to immunotherapy with PD-L1/PD-1 blockade (see the following discussion).