CXCR4 and cancer: However, in contrast to other cancer types, so far only three studies have identified and experimentally proved target genes of miR-622 in liver cancer (i.e., mitogen-activated protein 4 kinase 4 (MAP4K4), CXC chemokine receptor 4 (CXCR4), and kirsten rat sarcoma (KRAS) [6,32,33].