OBJECTIVETo study the expression of SEL1L (human Sel-1-like gene) mRNA and protein and its significance in esophageal cancer.

METHODSImmunohistochemical staining (S-P method) for SEL1L protein was performed in 90 samples of esophageal squamous cell carcinoma, 35 samples of normal esophageal mucosa 5 cm away from the tumor, 60 samples of esophageal mucosa adjacent to the tumor and 20 samples of esophageal squamous dysplasia. In situ hybridization for SEL1L mRNA was also carried out in the esophageal carcinoma cases and normal esophageal mucosa distant from and adjacent to the tumor.

RESULTSThe positive rate of SEL1L mRNA was higher in esophageal carcinoma (80.0%, 72/90), as compared with that in normal esophageal mucosa distant from (14.3%, 5/35) and adjacent to (16.7%, 10/60) the tumor (P < 0.01). The positive rate of SEL1L mRNA in tumors with lymph node metastasis (92.7%, 38/41) was higher than that in tumors without lymph node metastasis (69.4%, 34/49) (P < 0.01). On the other hand, the expression rate of SEL1L protein was higher in esophageal carcinoma (87.8%, 79/90) and esophageal dysplasia (90.0%, 18/20), as compared with that in normal esophageal mucosa distant from (14.3%, 5/35) and adjacent to (13.3%, 8/60) the tumor (P < 0.01). The expression of SEL1L protein in esophageal cancer however did not correlate with age and sex of the patient, tumor location, tumor size, degree of differentiation, depth of tumor invasion, lymph node metastasis and tumor clinical stage (P > 0.05). A positive correlation was found between the expression of SEL1L mRNA and SEL1L protein (r = 0.492, P < 0.01).

CONCLUSIONSL1L protein expression is regulated at the transcriptional level. The high SEL1L protein expression is mainly the result of increased transcription. Overexpression of SEL1L protein is likely an early event during the pathogenesis of esophageal squamous cell carcinoma. SEL1L protein may serve as an important biomarker in identifying patients with higher risk of developing esophageal cancer.