PDCD1 and colorectal carcinoma: However, clinical immunotherapeutic trials have revealed that anti-CTLA-4 monoclonal antibodies (mAbs) yield unsatisfactory clinical efficacies in unselective CRC patients (Chung et al., 2010), and anti-PD-L1 mAbs and anti-PD-1 have shown little or no response rates in metastatic CRC (mCRC) (Le, Uram and Wang 2015; Overman and McDermott 2017).