Purpose: We hypothesized that estrogen receptor-a (ER-a) status in endometrial carcinomas, associated with poor prognosis, is reflected in transcriptional signatures suggesting targets for new therapy.Experimental Design: Endometrial carcinoma samples in a primary investigation cohort (n ¼ 76) and three independent validation cohorts (n ¼ 155/286/111) were analyzed through integrated molecular profiling. Biomarkers were assessed by immunohistochemistry (IHC), DNA oligonucleotide microarray, quantitative PCR (qPCR), single-nucleotide polymorphism (SNP) array, and Sanger sequencing in the cohorts, annotated for comprehensive histopathologic and clinical data, including follow-up.Results: ER-a immunohistochemical staining was strongly associated with mRNA expression of the receptor gene (ESR1) and patient survival (both P < 0.001). ER-a negativity associated with activation of genes involved in Wnt-, Sonic Hedgehog-, and TGF-b signaling in the investigation cohort, indicating epithelial-mesenchymal transition (EMT). The association between low ER-a and EMT was validated in three independent datasets. Furthermore, phosphoinositide 3-kinase (PI3K) and mTOR inhibitors were among the top-ranked drug signatures negatively correlated with the ER-a-negative tumors. Low ER-a was significantly associated with PIK3CA amplifications but not mutations. Also, low ER-a was correlated to high expression of Stathmin, a marker associated with PTEN loss, and a high PI3K activation signature.Conclusion: Lack of ER-a in endometrial cancer is associated with EMT and reduced survival. We present a rationale for investigating ER-a's potential to predict response to PI3K/mTOR inhibitors in clinical trials and also suggest EMT inhibitors to ER-a-negative endometrial carcinomas.

ABSTRACT

Chromosome 8q24 is the most commonly amplified region across multiple cancer types, and the typical length of the amplification suggests that it may target additional genes to MYC. To explore the roles of the genes most frequently included in 8q24 amplifications, we analyzed the relation between copy number alterations and gene expression in three sets of endometrial cancers (N = 252); and in glioblastoma, ovarian, and breast cancers profiled by TCGA. Among the genes neighbouring MYC, expression of the bromodomain-containing gene ATAD2 was the most associated with amplification. Bromodomain-containing genes have been implicated as mediators of MYC transcriptional function, and indeed ATAD2 expression was more closely associated with expression of genes known to be upregulated by MYC than was MYC itself. Amplifications of 8q24, expression of genes downstream from MYC, and overexpression of ATAD2 predicted poor outcome and increased from primary to metastatic lesions. Knockdown of ATAD2 and MYC in seven endometrial and 21 breast cancer cell lines demonstrated that cell lines that were dependent on MYC also depended upon ATAD2. These same cell lines were also the most sensitive to the histone deacetylase (HDAC) inhibitor Trichostatin-A, consistent with prior studies identifying bromodomain-containing proteins as targets of inhibition by HDAC inhibitors. Our data indicate high ATAD2 expression is a marker of aggressive endometrial cancers, and suggest specific inhibitors of ATAD2 may have therapeutic utility in these and other MYC-dependent cancers.