Expression of metastasis-associated protein 1 (MTA1) in benign endometrium and endometrial adenocarcinomas

Endometrial carcinoma is one of the most common malignancies of the female genital tract. Metastasis-associated protein 1 (MTA1) is a component of the Mi-2/nucleosome remodeling and deacetylating complex and acts as a potent corepressor of estrogen receptor in breast cancer cells. MTA1 expression has been demonstrated in various cancers but has never been explored in endometrial carcinoma. We investigated the expression profile of MTA1 in different stages of benign endometrium as well as in endometrial endometrioid adenocarcinoma using immunohistochemistry and Western blotting. In the proliferative and secretory phases, MTA1 was expressed in both the glandular and the stromal compartments and was localized in nucleus and cytoplasm of these cells. MTA1 expression in secretory phase was less prominent when compared with the proliferative phase. In postmenopausal sections, MTA1 staining was observed in both glandular and stromal compartments and was localized in both nucleus and cytoplasm. Western blot analysis of 6 tumor specimens showed increased expression of MTA1 in all the tumors analyzed. Immunohistochemical staining performed on tumor microarray containing 70 endometrial endometrioid adenocarcinomas of various grades showed increased expression of MTA1 in 53 (75.7%) tumors. In grade 1 and grade 2 tumors, MTA1 was present in both nucleus and cytoplasm. Interestingly, in grade 3 tumors, MTA1 was localized in the cytoplasm only. Our results suggest a potential role of MTA1 in endometrial carcinomas.