CXCR4 and esophageal squamous cell carcinoma: The expression of tumor-derived cytokine MIF and its receptor CXCR4 were significantly associated with poor survivals of patients with ESCC; and the MIF and CXCR4 expression levels in tumor cells were independent predictive factors of survivals in patients with ESCC, as were the MIF expression level in TILs.