The Immunohistochemical expression of endothelial cell differentiation gene-2 receptor in human colorectal adenomas

The EDG-2 (endothelial cell differentiation gene-2) has been characterized as one of the high-affinity receptors of lysophosphatidic acid: an extracellular lipid mediator which can induce tumor progression. Recent studies have revealed that EDG-2 plays an important role in various pathological events including cell proliferation and tumor development. The investigation of EDG-2 is thus considered important for eliciting the mechanism of tumorigenesis. However, in colorectal tissue, the clinical significance of EDG-2 expression remains unclear. In the current study, we examined the immunohistochemical expression of EDG-2 in colorectal mucosa and adenoma, and clarified its relation with the clinicopathological features.

One hundred and sixty-one colorectal polyps were resected endoscopically or surgically at our institute from 2000 to 2001. According to the degree of dysplasia, adenomas were grouped into two categories: low-grade (mild or moderate dysplasia) and high-grade (severe dysplasia or carcinoma in situ). We investigated EDG-2 expression by immunohistochemistry.

EDG-2 was expressed almost exclusively in the cytoplasm in colorectal normal mucosa and adenoma. EDG-2 expression in normal mucosa and adenoma was 8% and 76%, respectively. EDG-2 expression was increased in low-grade adenoma compared with that in normal mucosa (P < 0.001). EDG-2 expression was significantly greater in adenomas with larger diameters (P < 0.001).

We demonstrated that EDG-2 expression was increased in the early stage of adenoma. A significant correlation between EDG-2 expression and the size of the adenomas suggests that EDG-2 may play an important role in the growth of these adenomas.