Amplification of the EGF receptor and c‐myc genes in human esophageal cancers

The incidence of esophageal cancer is extremely high in Linxian County and certain other regions of the People's Republic of China. Epidemiologic and laboratory studies suggest that N‐nitroso carcinogens and other environmental factors play a causative role. In the present study, employing over 100 DNA samples obtained from Lin‐xian patients who underwent surgery for esophageal cancer, we have found a significant frequency of amplification of either the human epidermal growth factor receptor (HER‐I) gene or the c‐myc oncogene. These changes were found not only in tumor specimens, but also in adjacent non‐tumor (grossly normal) tissue specimens obtained from patients with esophageal cancer. RNA samples were also obtained from over 30 tissue samples. These revealed considerable variation in the abundance of HER‐I and c‐myc transcripts in both the tumor and adjacent non‐tumor specimens. A few samples revealed extremely high levels of these transcripts. Thus, changes in gene copy number or level of expression of HER‐I or c‐myc DNA sequences may play an important role in the pathogenesis of esophageal cancer in this high‐risk region.