ALDH1A1 Is a Novel EZH2 Target Gene in Epithelial Ovarian Cancer Identified by Genome-Wide Approaches

Women's Cancer Program and Epigenetics and Progenitor Cell Keystone Program, Fox Chase Cancer Center, Philadelphia, PA 19111, USA.
Cancer Prevention Research (Impact Factor: 4.44). 12/2011; 5(3):484-91. DOI: 10.1158/1940-6207.CAPR-11-0414
Source: PubMed


Epithelial ovarian cancer (EOC) remains the most lethal gynecologic malignancy in the United States. EZH2 silences gene expression through trimethylating lysine 27 on histone H3 (H3K27Me3). EZH2 is often overexpressed in EOC and has been suggested as a target for EOC intervention. However, EZH2 target genes in EOC remain poorly understood. Here, we mapped the genomic loci occupied by EZH2/H3K27Me3 using chromatin immunoprecipitation followed by next-generation sequencing (ChIP-seq) and globally profiled gene expression in EZH2-knockdown EOC cells. Cross-examination of gene expression and ChIP-seq revealed a list of 60 EZH2 direct target genes whose expression was upregulated more than 1.5-fold upon EZH2 knockdown. For three selected genes (ALDH1A1, SSTR1, and DACT3), we validated their upregulation upon EZH2 knockdown and confirmed the binding of EZH2/H3K27Me3 to their genomic loci. Furthermore, the presence of H3K27Me3 at the genomic loci of these EZH2 target genes was dependent upon EZH2. Interestingly, expression of ALDH1A1, a putative marker for EOC stem cells, was significantly downregulated in high-grade serous EOC (n = 53) compared with ovarian surface epithelial cells (n = 10, P < 0.001). Notably, expression of ALDH1A1 negatively correlated with expression of EZH2 (n = 63, Spearman r = -0.41, P < 0.001). Thus, we identified a list of 60 EZH2 target genes and established that ALDH1A1 is a novel EZH2 target gene in EOC cells. Our results suggest a role for EZH2 in regulating EOC stem cell equilibrium via regulation of ALDH1A1 expression.

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Available from: Peter J Tummino, Sep 30, 2015
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    • "Recently, EZH2 siRNA was reported to induce G2/M arrest in human lung cancer cells [21]. This suggests that the biological function of EZH2 is diverse in different cancer cells, EZH2 mediates histone methylation and recruits DNA methyltransferase in the silencing of a variety of genes, associated with cell cycle control, survival, and other malignant phenotypes [22] [23] [24]. In breast and prostate cancers, EZH2 negatively regulated the tumor suppressor RKIP transcription through repression-associated histone modifications , therefore promoting tumor progression and metastasis [25]. "
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    ABSTRACT: The long non-coding RNA Hox transcript antisense intergenic RNA (HOTAIR) was recently implicated in breast cancer metastasis and is predictive of poor prognosis in colorectal and pancreatic cancers. We recently discovered that HOTAIR is a cell cycle-related lncRNA in human glioma, and its expression is closely associated with glioma staging and poor prognosis. Although lysine specific demethylase 1 (LSD1) and polycomb repressive complex 2 (PRC2) have been demonstrated to be functional targets of HOTAIR, how HOTAIR regulates glioma cell cycle progression remains largely unknown. In this study, we found that EZH2 (predominant PRC2 complex component) inhibition blocked cell cycle progression in glioma cells, consistent with the effects elicited by HOTAIR siRNA. However, the inhibition of LSD1 did not affect cell cycle progression in glioma cells. These results suggest that HOTAIR might regulate cell cycle progression through EZH2. Our intracranial mice model also revealed delayed tumor growth in HOTAIR siRNA- and EZH2 inhibitor-treated groups. Moreover, in HOTAIR knock-down cell lines, the expression of the PRC2-binding domain of HOTAIR (5' domain) but not of the LSD1-binding domain of HOTAIR (3' domain) resulted in accelerated cell cycle progression. In conclusion, HOTAIR promotes cell cycle progression in glioma as a result of the binding of its 5' domain to the PRC2 complex.
    Oncotarget 11/2014; 6(1). DOI:10.18632/oncotarget.2681 · 6.36 Impact Factor
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    • "Thus, there is a continuing demand for a potent therapeutic approach to target the majority of human epithelial cancers in which EZH2 is often overexpressed but not mutated. Although a variety of EZH2 target genes have been identified in various cancers (Cao et al., 2008; Kodach et al., 2010; Li et al., 2012; Yu et al., 2007, 2010), a whole-genome analysis indicated that EZH2-silenced genes appear to be moving targets and vary from cancer to cancer (Kondo et al., 2008). An EZH2 target common to multiple cancers with both functional and therapeutic implications has not been described to date. "
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    ABSTRACT: Although small-molecule targeting of EZH2 appears to be effective in lymphomas carrying EZH2 activating mutations, finding similar approaches to target EZH2-overexpressing epithelial tumors remains challenging. In MYC-driven, but not PI3K-driven prostate cancer, we show that interferon-γ receptor 1 (IFNGR1) is directly repressed by EZH2 in a MYC-dependent manner and is downregulated in a subset of metastatic prostate cancers. EZH2 knockdown restored the expression of IFNGR1 and, when combined with IFN-γ treatment, led to strong activation of IFN-JAK-STAT1 tumor-suppressor signaling and robust apoptosis. Pharmacologic depletion of EZH2 by the histone-methylation inhibitor DZNep mimicked the effects of EZH2 knockdown on IFNGR1 induction and delivered a remarkable synergistic antitumor effect with IFN-γ. In contrast, although they efficiently depleted histone Lysine 27 trimethylation, EZH2 catalytic inhibitors failed to mimic EZH2 depletion. Thus, EZH2-inactivated IFN signaling may represent a therapeutic target, and patients with advanced prostate cancer driven by MYC may benefit from the combination of EZH2 and IFN-γ-targeted therapy.
    Cell Reports 06/2014; 8(1). DOI:10.1016/j.celrep.2014.05.045 · 8.36 Impact Factor
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    • "A lineage-specific ALDH1 expression in different histological type of ovarian tumors has been proposed. Penumatsa et al reported reduced expression of ALDH1 in serous ovarian tumors [24]; Li et al [25] reported that ALDH1 expression was repressed by histone-lysine N-methyltransferase EZH2 in high-grade serous ovarian carcinoma and Saw at al reported that ALDH1 expression was higher in the endometrioid and mucinous tumors compared with clear cell and serous tumors [21]. While our data shows a differential higher ALDH enzymatic activity in endometrioid and mucinous versus serous tumor types, we did not find any correlation (positive or negative) with both PFS and OS. "
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    ABSTRACT: The prognostic/predictive role of both CD133 and Aldehyde dehydrogenase (ALDH) expression in human ovarian cancer remains elusive. This is an observational study that investigated the expression of CD133 and of ALDH enzymatic activity in fresh ovarian cancer samples and their association with different clinic-pathological patient' characteristics and explored their possible predictive/prognostic role. We analyzed the expression of CD133 and ALDH enzymatic activity in 108 human ovarian cancer samples. We found that among the total patients analyzed, 13% of them was completely negative for ALDH activity and 26% was negative for CD133 staining. Both markers were variably expressed within the samples and when both studied in the same tumor sample, no statistically significant correlation between ALDH enzymatic activity and CD133 expression was found. No statistical significant correlation was found also between the percentage values of positive ALDH and CD133 cells and the number of serial passages patient's cultures underwent, suggesting that these markers do not confer by themselves a self-renewal growth advantage to the cultures. Lower levels of CD133 were associated with higher tumor grade. No correlation with response to therapy, progression free survival and overall survival was found. Our data suggest that neither ALDH enzymatic activity nor CD133 expression provide additional predictive/prognostic information in ovarian cancer patients.
    American Journal of Cancer Research 04/2013; 3(2):221-229. · 4.17 Impact Factor
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