Furthermore, numerous investigations showed that PD-1 rs11568821 was not associated with NSCLC (Ma et al., 2015), Leukemia (Ramzi et al., 2018), colorectal cancer (Yousefi et al., 2013), Benign Brain Tumors (Namavar et al., 2017) and hepatocellular carcinoma (Bayram et al., 2012). Here, PDCD1 is linked to colorectal cancer.