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LY75 ablation mediates mesenchymal-epithelial transition (MET) in epithelial ovarian cancer (EOC) cells associated with aberrant DNA methylation alterations implicated in EOC dissemination

ABSTRACT: In epithelial ovarian cancer (EOC), acquisition of invasiveness is accompanied by the loss of the epithelial features and the gain of a mesenchymal phenotype, a process known as epithelial-mesenchymal transition (EMT). Understanding the regulation of cell behavior during EMT is crucial for identifying the molecular mechanisms of EOC dissemination. Previously we identified the mannose receptor LY75 as the cellular phenotype modulator. LY75 suppression induces the mesenchymal to epithelial transition (MET) in EOC cell lines with mesenchymal phenotype. In this study, we used the Reduced Representation Bisulfite Sequencing (RRBS) technology for a comprehensive analysis of DNA methylation alterations during LY75-mediated EMT in EOC cells. Three different comparison (M vs E) combinations were used for RRBS analysis, as further analysis of the sequencing data based on differentially methylated regions (DMRs) covering genes’ exons and promoter regions was indicative for about 10,000 genes displaying DMRs for each of the three experimental combinations. Consecutive Venn diagram analysis of the DMRs data from the of the three experimental combinations revealed 6666 genes, displaying common altered DMRs in their exons/promoter regions, following LY75-mediated EMT alterations in EOC cells. Based on the 6666 gene list, we further proceeded with a more stringent selection of genes displaying rather high degree (>70%) of methylation in their promoter regions and previously shown to be implicated in cancer-related EMT signaling. Our stringent selection retained 45 genes (see Supplemental Table 1E), as the DNA methylation status of the promoter regions of most of these genes was further validated by an alternative approach (BSP sequencing). Ten genes were finally selected, whose promoter DNA methylation pattern coincided with their mRNA and protein expression levels. Further in vitro and in vivo studies are warranted to more completely elucidate the functional implications of these 10 genes in ovarian tumorigenesis.

ORGANISM(S): Homo sapiens

PROVIDER: GSE142310 | GEO | 2020/03/30

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.

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LY75 ablation mediates mesenchymal-epithelial transition (MET) in epithelial ovarian cancer (EOC) cells associated with aberrant DNA methylation alterations implicated in EOC dissemination

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