One of the genes that the authors have isolated by a differential display of
hepatocellular carcinoma compared to adjacent liver is the
alpha6 integrin.
alpha6 integrin is the major
adhesion receptor for
laminin and is suggested to be involved in
tumor cell invasion and
metastasis. To our knowledge, however, there are no reports on
alpha6 integrin expression in esophageal
carcinoma. We thus conducted a study to determine its clinicopathologic significance in human esophageal
carcinoma. The
tumor/normal (T/N) ratio of
alpha6 integrin expression was calculated by Northern hybridization in 45 cases of esophageal
carcinoma. In selected cases the expression of the
alpha6 integrin variants A and B was also investigated by
reverse transcriptase-polymerase chain reaction, and immunostaining for
alpha6 integrin was performed. The expression levels of
alpha6 integrin mRNA in the
tumor tissue were greater than those of the corresponding normal tissue in 39 of 45 cases (87%). The overexpression of
alpha6 integrin was also recognized by immunostaining. Fifteen cases with a high T/N ratio demonstrated a deeper invasion into the esophageal wall than the 30 cases with a low T/N ratio. Although there was no significant difference, the 15 cases with a high T/N ratio had a tendency for a worse prognosis. The ratio of the two variants (alpha6A/alpha6B) did not show any relationship to survival. The findings imply that
alpha6 integrin is overexpressed in human esophageal
carcinomas and that
alpha6 integrin may play an important role in esophageal
tumor invasion.