[Esophageal carcinoma in human fetus induced by N-methyl-N-benzylnitrosamine (NMBzA)].

Previous studies have suggested that N-nitroso compounds play a causative role. In the present study, human fetal esophageal epithelium was cultured for 3 weeks with NMBzA obtained in Linxian County (a high incidence area of esophageal cancer). Then, the explants were heterotransplanted to mesentery of BALB/c nude mice which were continually fed with NMBzA in drinking water for 8 months. The results showed that in NMBzA-treated mice, a small tumor was found on the mesentery two months after transplantation. The small tumor gradually grew to 2 x 1.8 cm in size 8 months after transplantation. No tumor was observed in control nude mice. Macroscopically, no tumor was seen in the esophagus of nude mice bearing esophageal tumor on mesentery. Pathology of the induced tumor showed squamous cell carcinoma. DNA extracted from the tumor induced by NMBzA was hybridized with Alu sequence using dot blot. Alu sequence was present in the induced tumor, indicating that the tumor is of human origin. This is the first report to confirm that human esophageal carcinoma could be induced by N-nitrosamine. It provides a direct evidence that NMBzA is a causative agent of esophageal cancer in Linxian County.