The ETAR and CXCR4 expression levels were closely correlated with each other: in the 48 NPC cases positive for the expression of CXCR4, 46 (95.8%, P < 0.0001) were also positive for ETAR expression (R = 0.338, P = 0.0001) (Table 2). The gene discussed is CXCR4; the disease is nasopharyngeal carcinoma.