Purpose: In stomach adenocarcinoma, the role of the hormonal receptor, estrogen receptor (ER), has been controversial. Recently, a new estrogen receptor, called estrogen receptor beta (ER beta), was found to be expressed in various tissues including normal gastrointestinal tract. In this paper, the expression of ER beta 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 ER alpha and beta 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 chi(2)-test) explored the relation between the immunohistochemical result and clinicopathological characteristics.
Results: All 29 adenocarcinomas, including the signet ring cell ones, demonstrated clear ER beta nucleus staining. Lymphocytes, venous endothelial cells, smooth muscle, and non-cancerous stomach glands also showed strong ER beta staining, while no staining was observed in the immunohistochemistry of ER alpha. Western blotting showed equivalent ER beta 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 ER beta, and that the role of ER beta 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.