['This study investigated the clinical relevance and biological function of paired box gene 2 (PAX2) in esophageal squamous cell carcinoma (ESCC).', 'Results showed that PAX2 expression was significantly increased in tumor tissues and that its expression correlated with the ESCC stage (P = 0.001), lymph node metastasis (pN, P = 0.019) and lymphatic invasion (P = 0.005) in 120 ESCC tissue specimens by immunohistochemistry. Furthermore, PAX2 overexpression resulted in markedly reduced cell proliferation but increased metastasis capacity in ESCC TE-1 and Eca-109 cells. Knockdown of PAX2 expression with a short hairpin RNA confirmed a role in the promotion of metastasis in ESCC cells. mRNA microarray screening revealed that PAX2 overexpression affected multiple genes that function in multiple pathways. Interleukin-5 (IL-5), which was induced by PAX2 and has been shown to promote tumor metastasis, was further studied in greater detail. Two PAX2 binding sites were identified in the IL-5 promoter, and PAX2 was observed to stimulate IL-5 promoter activity and IL-5 expression in esophageal cancer cells. Chromatin immunoprecipitation (ChIP) confirmed the direct binding of PAX2 in the IL-5 promoter. The expression of PAX2 mRNA significantly correlated with that of IL-5 in normal esophageal and ESCC tissues.'] Does upregulation of PAX2 promote the metastasis of esophageal cancer through interleukin-5?