Contrary to the previously purported role of gap junction (GJ) associated-
protein connexin 26 (Cx26) as a
tumor suppressor, increased expression of Cx26 has recently been demonstrated in several human
malignancies. Surprisingly, this high expression is reportedly related to poor prognosis in squamous cell lung
carcinoma and
breast cancer. In this study, we examined levels of Cx26 in various human gastrointestinal (GI)
carcinomas, with a focus on
pancreatic carcinomas, using immunohistochemistry. Many GI
carcinomas displayed abundant Cx26 expression, predominantly in the cytoplasm. Cx26 was detected in 5/8
gastric cancers (62.5%), 6/8
squamous cell carcinomas of the esophagus (75.0%), 7/8
pancreatic cancers (87.5%) and 7/8
colon cancer cases (87.5%). However, Cx26 expression was not present in
hepatocellular carcinoma (HCC, 0/8). Extensive immunohistochemical examination was performed on
pancreatic carcinomas, revealing strong expression of Cx26
protein in 30/43 cases (70%), weak expression in 6/43 (14%) and no expression in 7/43 (16%). The present study demonstrated up-regulated Cx26 expression in a considerable percentage of GI
carcinomas, with the exception of HCC. Our findings suggest that Cx26 may be involved in some of the malignant processes of GI
cancers, and especially in
pancreatic carcinomas.