PDCD1 and colorectal carcinoma: We searched PubMed, Web of Science, Google Scholar, and conference/congress paper using the search terms “colorectal cancer” or “CRC” along with these terms “immune checkpoint”, “CTLA-4”, “PD-1”, “PD-L1”, “LAG-3”, “TIM-3”, and “monoclonal antibodies (mAbs)” in combination with specific mAbs for each immune checkpoint.