CHI3L1 and esophageal squamous cell carcinoma: To investigate the expression of YKL-40 in ESCC, the YKL-40 mRNA and protein levels were detected by real-time RT-PCR and Western Blotting, respectively, in several esophageal carcinoma cell lines (Eca-109, Kyse180, Kyse510, Kyse30, Kyse140 and Kyse520) and the immortalized esophageal epithelial cell line NE-3.