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Grainyhead-like 2 (GRHL2) maintains the epithelial status of ovarian cancer through miR-200-ZEB1 regulatory networks (ChIP-Seq)

ABSTRACT: Epithelial ovarian cancer (EOC) is clinically heterogeneous, comprising different histological and biological subtypes. Multiple studies have implicated epithelial-mesenchymal transition (EMT), a biological process by which polarized epithelial cells convert into a mesenchymal phenotype, to contribute significantly to this molecular heterogeneity of EOC. From gene expression analyses of a collection of EMT-characterized EOC cell lines, we found that the expression of the transcription factor Grainyhead-like 2 (GRHL2) correlates with E-cadherin expression and the epithelial phenotype. EOC tumors with lower levels of GRHL2 are associated with the Mes (mesenchymal) molecular subtype and show poorer overall survival in patients. Here, we demonstrate that shRNA-mediated knockdown of GRHL2 in EOC cells with an epithelial phenotype resulted in EMT changes, with increased cell migration, invasion and motility. By ChIP-sequencing and gene expression microarray, we identified a variety of target genes regulated by GRHL2, including protein-coding and non-coding genes. Our data suggest that GRHL2 maintains the epithelial phenotype of EOC cells through the regulatory networks of miR-200b/a, ZEB1 and E-cadherin. These findings support GRHL2 as a crucial player in the molecular heterogeneity of EOC.

ORGANISM(S): Homo sapiens

PROVIDER: GSE71018 | GEO | 2016/02/25

SECONDARY ACCESSION(S): PRJNA290109

REPOSITORIES: GEO

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Project description:Epithelial ovarian cancer (EOC) accounts for 4% of all cancers in women and is the leading cause of death from gynecologic malignancies. It is well established that cancer invasion and metastasis still represent the major causes of the failure of cancer treatment. Previously, we identified the mannose receptor LY75 (DEC205/CD205) gene as notably hypomethylated in high-grade (HG) serous epithelial ovarian tumors, compared to normal ovarian tissues. LY75 has been identified as a putative antigen-uptake receptor, which is expressed abundantly on dendritic cells, which are specialist antigen presenting cells to T lymphocytes for the initiation of an immune response. The implication of LY75 in EOC tumorigenesis is currently unknown. Here we show that LY75 is strongly overexpressed in HG serous EOC tumors as compared to normal ovarian tissue. Importantly, shRNA-mediated LY75 knockout in the mesenchymal EOC cells (SKOV3) led to mesenchymal to epithelial transition (MET), associated with overexpression of epithelial markers E-cadherin and EPCAM and loss of expression of mesenchymal markers Fibronectin, N-cadherin Snail1 and Twist1. In addition, LY75 suppression significantly inhibited EOC cell migration and invasion in vitro. However, LY75 knockdown led to enhanced tumor cell dissemination and significantly increased lethality in vivo, in xenograft model of advanced peritoneal EOC. Thus, our findings indicate that LY75 could play an essential role in the mesenchymal-to-epithelial transition (MET) of EOC cells and support the hypothesis that, while epithelial-to-mesenchymal transition (EMT) enables the invasiveness of tumor cells, a MET-associated epithelial phenotype could be essential for their metastatic colonization. To better understand the molecular mechanisms of LY75 gene action in epithelial ovarian cancer (EOC), we employed the Agilent Whole Human Genome microarrays, containing ~ 44,000 genes to identify global gene expression changes upon LY75 suppression in SKOV3 EOC cells. We compared the gene expression of the previously selected shRNA-mediated LY75-knockdown clones sh-S3 and sh-S6 against the corresponding control (ctrl) clone. The microarray experiments were performed in duplicates, as two hybridizations were carried out for each of the LY75-suppressing cell clone against the corresponding control, using a fluorescent dye reversal (dye-swap) technique.

Project description:Using a retrovirus-mediated cDNA expression cloning approach we identified the grainyhead-like 2 (GRHL2) transcription factor as novel protooncogene. Overexpression of GRHL2 in NIH3T3 cells induced striking morphological changes, an increase in cell proliferation, anchorage-independent growth, and tumor growth in vivo. By combining a microarray analysis and a phylogenetic footprinting analysis with various biochemical assays we identified the epidermal growth factor receptor family member Erbb3 as a novel GRHL2 target gene. In breast cancer cell lines, shRNA-mediated knockdown of GRHL2 expression or functional inactivation of GRHL2 using dominant-negative GRHL2 proteins induce downregulation of ERBB3 gene expression, a striking reduction in cell proliferation and morphological and phenotypical alterations characteristic of an epithelial-to-mesenchymal transition (EMT), thus implying dual roles of GRHL2 in breast carcinogenesis. Interestingly, we could further demonstrate that expression of GRHL2 is directly suppressed by the transcription factor zinc-finger-enhancer binding protein 1 (ZEB1) which in turn is a direct target for repression by GRHL2, suggesting that the EMT transcription factors GRHL2 and ZEB1 form a double negative regulatory feedback loop in breast cancer cells. Finally, a comprehensive immunohistochemical analysis of GRHL2 expression in primary breast cancers showed loss of GRHL2 expression at the invasive front of primary tumors. A pathophysiological relevance of GRHL2 in breast cancer metastasis is further demonstrated by our finding of a statistically significant association between loss of GRHL2 expression in primary breast cancers and lymph-node metastasis. We thus demonstrate a crucial role of GRHL2 in breast carcinogenesis. To evaluate the role of the GRHL2 transcription factor in carcinogenessis we overexpressed the human GRHL2 protein in NIH3T3 cells. Parental NIH3T3 cells do not express the orthologic protein. Alterations in genome-wide transcriptional profiles were determined by microarray analysis.

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Grainyhead-like 2 (GRHL2) maintains the epithelial status of ovarian cancer through miR-200-ZEB1 regulatory networks (ChIP-Seq)

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