Identification of a novel-estrogen regulated gene (EIG121) that is over-expressed in type I but down-regulated in type II endometrial cancer
Authors: Lei Deng, Russell Broaddus, Adrienne McCampbell, Gregory L. Shipley, David S. Loose, George M. Stancel, Peter J. Davies
Journal: Cancer Research (2005)

Proc Amer Assoc Cancer Res, Volume 46, 2005

1651 

BACKGROUND: The positive association of endometrial hyperplasia / endometrioid adenocarcinoma and prolonged excessive estrogen stimulation has been well established, but the underlying molecular mechanisms are largely unknown. It is generally believed that estrogens are not genotoxic themselves and thus the effects of estrogen on the endometrium are likely mediated by an array of downstream genes whose expression may be regulated by estrogen. The identification of such genes and pathways that are affected by estrogenization may shed light on the mechanisms of estrogen action. DESIGN: Two pools of endometrial RNA, each from 20 postmenopausal women receiving either placebo or estrogen replacement therapy with a mixture of estrone and equilin sulfates (EES) for three months, were subjected to cDNA microarray analysis. A novel gene identified by this approach was EIG121. The expression level of this transcript was then measured by real-time quantitative RT-PCR in more normal endometrial biopsies from both postmenopausal (n=30) and premenopausal women (n=15). The expression of EIG121 was also measured in 95 endometrioid adenocarcinoma samples, 12 uterine papillary serous carcinoma (UPSC) samples, and 10 malignant mixed mullerian tumor (MMMT) samples. A polyclonal antibody was raised against the EIG121 C-terminal peptide and was used to detect EIG121 protein by immunochemistry. RESULTS & CONCLUSION: In the postmenopausal endometrium, we have confirmed that the expression of EIG121 was significantly induced by both forms of ERT. Premarin and EES induced the expression of EIG121 by 2- and 3-fold respectively. In pre-menopausal endometrium, the expression of EIG121 was significantly higher in the estrogen-dominated proliferative phase than the secretory phase (P< 0.01). In endometrial hyperplasia and type I endometrial carcinomas, two diseases that are usually associated with a hyperestrogenic state, the expression of EIG121 was significantly elevated (on average 2-fold and 5-fold, respectively). By immunochemistry, EIG121 protein was found to be predominately expressed in the endometrial epithelial cells, especially in the apical aspect of the glandular lumens. Compared with normal endometrium, both the number of EIG121-postive cells and the intensity of EIG121 staining in individual cells were significantly increased in type I endometrial carcinomas. Although the level of EIG121 mRNA expression was still significantly higher in grade 3 endometriod carcinomas, the EIG121 level tended to decline with increasing tumor grade. In sharp contrast, EIG121 expression was significantly suppressed in both UPSC and MMMT endometrial cancer samples, to only less than 5% of the average level in normal endometria. Taken together, EIG121 appeared to be a good biomarker associated with the hyperestrogenic state and type I endometrial adenocarcinoma.