PDCD1 and colorectal cancer: In non-small cell lung carcinoma, immunoregulatory agents targeting CTLA4, PD-1, or PD-L1 have showed promising inhibitory effect (Osmani et al., 2018), but in gastric cancer, anti-CTLA4 drug tremelimumab failed to bring anticipated results in clinical setting (Ralph et al., 2010), and PD-1 and PD-L1 inhibitors failed to make for complete response in most advanced gastric cancer and colorectal cancer patients (Le et al., 2015; Muro et al., 2016; Overman et al., 2017).