Estrogen receptor β is expressed in human stomach adenocarcinoma

Purpose: In stomach adenocarcinoma, the role of the hormonal receptor, estrogen receptor (ER), has been controversial. Recently, a new estrogen receptor, called estrogen receptor β (ERβ), was found to be expressed in various tissues including normal gastrointestinal tract. In this paper, the expression of ERβ in stomach adenocarcinomas has been investigated for the first time, specifically in signet ring cell adenocarcinomas, together with surrounding non-cancerous tissues. Methods: By immunohistochemistry the expression of ERα and β was studied in 29 stomach adenocarcinomas, ten signet ring cell adenocarcinomas, and 19 other adenocarcinomas. Western blotting was performed to examine the immunohistochemical result. Statistical studies (Student's t test and x²-test) explored the relation between the immunohistochemical result and clinicopathological characteristics. Results: All 29 adenocarcinomas, including the signet ring cell ones, demonstrated clear ERβ nucleus staining. Lymphocytes, venous endothelial cells, smooth muscle, and non-cancerous stomach glands also showed strong ERβ staining, while no staining was observed in the immunohistochemistry of ERα. Western blotting showed equivalent ERβ protein levels in cancerous and non-cancerous tissues, which was consistent with the results of immunohistochemical staining. Among signet ring cell adenocarcinomas of the stomach, cytoplasm were stained in addition to nuclei, specifically in patients under the age of 40 years. Conclusions: Our results imply that the effects of estrogen in stomach cancer, as well as those in normal stomach, may be mediated by ERβ, and that the role of ERβ may differ by the subtype of stomach adenocarcinoma - specifically signet ring cell adenocarcinomas and other ones - although large scale samples are needed to confirm these findings.