NGFR and esophageal cancer: Although Li S et al. reported that high expression of stem cell marker CD271 was closely associated with the patient's tolerability of chemotherapy and susceptibility to tumor invasion and metastasis [23], Forghanifard MM et al. found that the expression levels of stem cell regulators SALL4 and SOX2 in esophageal cancer tissues were closely correlated with poor prognosis and high metastasis rate in the patients [6].