27 - 30 May 2005

PATTERNS OF GENE EXPRESSION IN NORMAL AND MALIGNANT ENDOMETRIUM David S. Loose PhD University of Texas Health Science Center Houston, Texas USA

Our laboratory is interested in identifying surrogate biomarkers whose expression is altered in endometrial hyperplasia or cancer. We have used a combination of approaches including microarray analysis and real-time quantitative PCR to identify such candidate genes. Type I endometrial cancer is thought to follow a progression from normal to a hyperplasia and then on to cancer.

It is generally considered that this is an estrogen dependent process (1). To substantiate this hypothesis, we used real-time quantitative PCR and quantified a group of mRNAs that we previously had shown are markedly regulated by chronic estrogen treatment in normal post-menopausal endometrium.

For example, the progesterone receptor (PR) mRNA was induced by 9-fold following 3 months of Premarin treatment in normal post-menopausal women; similarly, IGF-1 was induced by 17-fold, retinaldehyde dehydrogenase Type II (RALDHII) was induced 6.4-fold and secreted frizzled-related protein (sFRP4) by 9-fold. We prepared total RNA from carefully dissected endometrial hyperplasias and quantified the same transcripts and compared them with RNA samples from normal endometrium.

Surprisingly, none of these markers of estrogenization were elevated in the hyperplasias: PR, 1.33+/-1.07 vs. 3.22+/-0.9 (normal endometrium vs. hyperplasia, transcript normalized to 18S rRNA), IGF-1, 4.0+/-0.312 vs. 1.8+/-0.318, RALDHII, 0.12+/-0.58 vs. 0.11+/-0.12, 0.9+/-0.22 vs. 0.4+/-0.1. This suggests that hyperplasia is not typified phenotypically as overexpression of estrogen-regulated genes.

Using a panel of candidate biomarkers we have identified potential markers of hyperplasia and cancer. Estrogen-induced protein 121 kd (EIG121) is a recently discovered protein of unknown function that was identified by microarray analysis of estrogen-induced genes in human post-menopausal endometrium.

Compared to baseline, 3 months of Premarin treatment increased EIG-121 transcript levels by about 5-fold. Computer modeling suggests that EIG121 codes for a putative transmembrane protein. EIG121 is highly over expressed in endometrial cancers and hyperplasias compared to normal endometrium, and may represent an early-stage biomarker for endometrial cancer. Other biomarkers that may be useful to distinguish normal from hyperplastic endometrium include IGF1-R, the receptor for IGF-1, which is markedly upregulated in endometrial hyperplasia but not in endometrial cancers. The upregulation in IGF1R in hyperplasias was associated with a marked increase in phospho-AKT suggesting that signaling via important pathway is altered in endometrial hyperplasia.

References:

1. Matias-Guiu, Catasus, et al, 2001, Hum Path 32:569-5767.

List of abstracts from the 3rd International Conference on the Female Reproductive Tract