CXCL12 and neoplasm: Some studies found that in CXCR4-positive esophageal cancer, the level of CXCL12 expression was significantly correlated with lymphatic metastasis [12]; Koishi K et al. found that continuous up-regulation of CXCR4 in patients with esophageal cancer caused by radiotherapy and chemotherapy was significantly correlated with poor prognosis [13]; Numerous studies showed that radiotherapy and chemotherapy could gather or up-regulate the ratio of tumor stem cells, indirectly indicating that esophageal cancer might highly express CXCR4.