However, the success of immunotherapy is variable between patients and likely to be dependent on the presence of the relevant target; for example, the success of targeting the PD-1/PD-L1 axis was limited to patients with tumors expressing PD-L1 and with CD8 T cell infiltration (20), and so far these drugs have demonstrated poor clinical efficacy in CRC (21). Here, PDCD1 is linked to colorectal carcinoma.