Expression of YKL-40 mRNA or protein in ESCC cell lines, tissues and location in tissue. Expression of mRNA and protein in immortalized esophageal epithelial cell line (NE-3) and esophageal carcinoma cell lines was analyzed by real-time PCR and Western Blotting, respectively (A, B) and in six pairs of matched ESCC and noncancerous tissues (D, E). Expression level was normalized by GAPDH and α-tublin, respectively. Error bars represent standard deviations (SD) calculated from three parallel experiments. Protein level in supernatant was measured by ELISA (C). Location of YKL-40 was determined by immunohistochemistry (F). The normal esophageal epithelial tissue showed no expression of YKL-40 (F a-b, 200 × and 400×). The ESCC tissues showed low (F c-d), medium (F e-f) and high (F g-h) expression of YKL-40 (200× and 400×).