A minimal critical region of the 8p22-23 amplicon in esophageal adenocarcinomas defined using sequence tagged site-amplification mapping and quantitative polymerase chain reaction includes the GATA-4 gene.

The incidence of esophageal adenocarcinomas has increased greatly over the past 20 years. The genetic alterations associated with this disease, however, remain largely unknown. We identified recently a novel amplicon at 8p22-23 in esophageal adenocarcinomas using the restriction landmark genomic scanning two-dimensional gel technique. Four known genes within or near this amplicon were initially characterized. The cathepsin B (CTSB) gene was found to be amplified in 13% of esophageal tumors. CTSB was shown previously to be overexpressed without amplification in many other human cancers. An approach termed sequence tagged site-amplification mapping has been implemented in the present study, allowing the 8p22-23 amplicon to be narrowed from 12 cM to a <2-cM minimal amplified area located between markers D8S552 and D8S1759. The CTSB gene maps within this region. To identify other cancer-related candidate genes in this region, a positional candidate gene approach was subsequently applied to characterize this minimal critical region. An expressed sequence tag (EST), which was included in the minimal critical region, demonstrated both amplification and overexpression. This EST and the extended sequence from the EST were determined to be a novel sequence in the 3' untranslated region of the human GATA-4 gene. GATA-4, a member of a zinc finger transcription factor family, was confirmed to be amplified and overexpressed in esophageal adenocarcinomas and was localized within <0.5 kb from CTSB. Furthermore, amplification of 8p22-23 was detected in one of eight gastric cardia adenocarcinomas but was not observed in either human lung adenocarcinomas (n = 39) or in esophageal squamous cell carcinomas (n = 24). The relatively high frequency of the 8p22-23 amplification in esophageal (13.6%) and gastric cardia (12.5%) adenocarcinomas may indicate a specificity of this amplicon for tumors of gastroesophageal origin.