SOX2 is a high-mobility group box embryonic stem cell
transcription factor that is expressed in the developing foregut and normal gastric epithelium and is downregulated in intestinal
metaplasia of the stomach and esophagus. In addition, SOX2 colocalizes with p63 in the basal layer and plays a critical role in the maintenance of the stratified squamous epithelium of the esophagus. SOX2 expression in
squamous cell carcinomas of the gastrointestinal tract has not been previously evaluated. The purpose of this study was to determine whether SOX2 is differentially expressed in
squamous cell carcinomas versus
adenocarcinomas of the esophagus and rectum/anal canal and to compare its expression to p63,
cytokeratin 5/6, and CDX2. In total, 93
tumors were evaluated: 26 esophageal
squamous cell carcinomas, 23 esophageal
adenocarcinomas, 21
squamous cell carcinomas of the anal canal, and 23 rectal
adenocarcinomas. SOX2 was expressed in 81% of esophageal
squamous cell carcinomas and 91% of anal canal
squamous cell carcinomas, compared to 13% and 17% of esophageal and rectal
adenocarcinomas, respectively. p63 was expressed in 96% of esophageal
squamous cell carcinomas and 100% of anal canal
squamous cell carcinomas; the single
squamous cell carcinoma negative for p63 was strongly positive for SOX2.
Cytokeratin 5/6 was expressed in most esophageal and anal canal
squamous cell carcinomas, but was also positive in 43% of esophageal
adenocarcinomas and 13% of rectal
adenocarcinomas. In summary, SOX2 is preferentially expressed in
squamous cell carcinomas of the esophagus and anal canal compared to
adenocarcinomas from these sites. SOX2 may be useful in an immunohistochemical panel to differentiate between
squamous cell carcinomas and
adenocarcinomas of the gastrointestinal tract.