ABSTRACT: Global gene expression patterns associated with early stage endometrial cancer have been reported, but changes in molecular expression associated with tumor grade, depth of myometrial invasion, and non-endometrioid histology have not been previously elucidated. Our group hypothesized there are unique genetic events underlying early endometrial carcinogenesis. Ninety-two samples of pathologically reviewed stage I endometrial cancers (80 endometrioid and 12 serous) with a heterogeneous distribution of grade and depth of myometrial invasion (i.e. 9 IAG1, 14 IAG2, 7 IAG3, 14 IBG1, 12 IBG2, 13 IBG3, 7 ICG1, 10 ICG2, and 6 ICG3) were examined in relation to 12 samples of atrophic endometrium from postmenopausal women. Specimens were analyzed using oligonucleotide microarray analysis and a subset of the differentially expressed transcripts was validated using quantitative PCR. Comparison of early stage cancers with normal endometrium samples by the univariate t-test with 10,000 permutations identified 900 genes that were differentially regulated by at least 4-fold at a p value of <0.001. Unsupervised analysis revealed that when compared to normal endometrium, serous and endometrioid stage I cancers appeared to have similar expression patterns. However, when compared in the absence of normal controls, they were distinct. Differential expression analysis revealed a number of transcripts that were common as well as unique to both histologic types. This data uncovers previously unrecognized, novel pathways involved in early stage endometrial cancers and identifys targets for prevention strategies that are inclusive of both endometrioid and serous histologic subtypes. Ninety-one samples of pathologically reviewed stage I endometrial cancers (79 endometrioid and 12 serous) with a heterogeneous distribution of grade and depth of myometrial invasion (i.e. 9 IAG1, 14 IAG2, 7 IAG3, 14 IBG1, 12 IBG2, 13 IBG3, 7 ICG1, 10 ICG2, and 6 ICG3) were examined in relation to 12 samples of atrophic endometrium from postmenopausal women. Specimens were analyzed using oligonucleotide array analysis.
