Expression of c-Kit (CD117) in benign and malignant human endometrial epithelium

Background.-The proto-oncogene c-kit encodes a tyrosine kinase receptor (CD 117) with a molecular weight of 145 kd. Previous studies, predominantly uti lizing immunohistochemistry, have led to contradictory findings regarding t he expression of CD117 in the endometrium. To help resolve this issue, we a nalyzed a series of benign and malignant endometrial tissues using both imm unohistochemistry and Western blot analysis. Objective.-To examine the expression of CD117 in benign and malignant human endometrial tissues. Methods.-The expression of CD117 in 35 benign endometrial tissues (7 hyperp lastic, 14 proliferative, 14 secretory) and 10 endometrioid carcinomas was investigated by immunohistochemistry (clone K45 monoclonal antibody). Immun oprecipitation (clone K69 monoclonal antibody) followed by Western blotting (clone K45 monoclonal antibody and clone 1.D9.3D6 monoclonal antibody) was performed to confirm CD117 expression. Results.-Fifty-seven percent of the hyperplasias, 93% of proliferative endo metria, and 79% of secretory endometria immunostained positively for CD117. in benign endometria, epithelial staining tended to be more intense in the hyperplastic and proliferative endometria as compared to the secretory end ometria, whereas endometrial stromal cells were not immunoreactive. Of the 10 frozen endometrial tissues analyzed by immunohistochemistry, 4 of 9 endo metrioid carcinomas and a single case of an endometrioid polyp developing i n association with a carcinoma expressed CD117. Immunoprecipitation followe d by Western blot analysis confirmed expression of full-length CD117 in an endometrial polyp and carcinoma, and revealed a correlation between levers of immunoprecipitated CD117 and immunohistochemical staining intensity. Conclusions.-Benign and malignant endometrial tissues express CD117. Our da ta suggest (a) a possible relationship between estrogen and CD117 expressio n in benign endometrium and (b) potential involvement of this growth factor receptor in endometrial carcinogenesis.