Another study discovered that in patients with colorectal cancer liver metastases, the expression of CXCR4 CXCR7, TLR2/TLR4, and PD-1/PD-L1 was significantly increased in metastatic liver tissues compared to unaffected liver tissues (D’Alterio et al., 2016). The gene discussed is PDCD1; the disease is colorectal cancer.