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Overexpression of piRNA pathway genes in epithelial ovarian cancer.

ABSTRACT: The importance of the Piwi-interacting RNA (piRNA) pathway for germ cell maintenance, genome integrity, DNA methylation and retrotransposon control raises possible roles of this pathway in cancer. Indeed aberrant expression of human PIWI orthologs and Maelstrom has been observed in various cancers. In this study we explored the expression and function of piRNA pathway genes in human ovarian cancer, based on our recent work, which showed widespread expression of piRNA pathway genes in the mammalian. Our work shows that PIWIL1 and MAEL expression is significantly increased in malignant EOC (n = 25) compared to benign tumor tissues (n = 19) and normal ovarian tissue (n = 8). The expression of PIWIL3 is lower in malignant and benign tissues when compared to normal ovary. Sequencing of PIWIL1 transcript revealed that in many tumors deletion of exon 17 leads to the introduction of a premature stop codon in the PIWI domain, likely due to a splicing error. In situ hybridization on tumor sections revealed that L1, PIWIL1, 2 and MAEL are specifically expressed in epithelial cells (cancerous cells) of EOC. Furthermore, PIWIL2 and MAEL are co-expressed in the stromal cells adjacent to tumor cells. Since PIWIL1 and MAEL are up regulated in malignant EOC and expressed in the epithelial cells, we investigated if these two genes affect invasiveness of ovarian cancer cell lines that do not normally express these genes. PIWIL1 and MAEL were transiently over expressed in the ovarian cancer cell line SKOV3, followed by real-time measurements of cell invasiveness. Surprisingly both PIWIL1 and MAEL over expression decreased the invasiveness of SKOV3 cells. Our findings support a growing body of evidence that shows that genes in this pathway are upregulated in cancer. In ovarian cancer we show for the first time that Piwil1 transcript may often be abnormal result in non functional product. In contrast to what has been observed in other cell types, we found that PIWIL1 and MAEL have a repressive effect on cell invasiveness.

SUBMITTER: Lim SL

PROVIDER: S-EPMC4059699 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Overexpression of piRNA pathway genes in epithelial ovarian cancer.

Lim Shu Ly SL Ricciardelli Carmela C Oehler Martin K MK Tan Izza M D De Arao IM Russell Darryl D Grützner Frank F

PloS one 20140616 6

The importance of the Piwi-interacting RNA (piRNA) pathway for germ cell maintenance, genome integrity, DNA methylation and retrotransposon control raises possible roles of this pathway in cancer. Indeed aberrant expression of human PIWI orthologs and Maelstrom has been observed in various cancers. In this study we explored the expression and function of piRNA pathway genes in human ovarian cancer, based on our recent work, which showed widespread expression of piRNA pathway genes in the mammali ...[more]

PMID: 24932571

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Project description:Objective: DUSP6 is a negative regulator of the ERK signaling pathway and plays an important role in chemotherapy-resistance. Previously we showed that DUSP6 is overexpressed in ovarian cancer side population (SP) cells that possess cancer stem cell-like properties and are quiescent and chemotherapy-resistant. Here, we explore the effects of DUSP6 on chemotherapy-resistance by examining its regulation of the ERK signaling pathway and G0/G1 cell cycle arrest. Methods: mRNA and protein expression of DUSP6 and G0/G1 cell cycle checkpoint regulating proteins (CyclinD1, CyclinD3 and CyclinE2) was evaluated among ovarian cancer cell lines and tissue samples. Ovarian cancer cells were transiently transfected to overexpress DUSP6. After treatment with cisplatin, cell viability was measured by the MTS assay at 48 hours and the half maximal inhibitory concentration (IC50) for each cell line was calculated. Subcellular localization and cell cycle analysis were determined by using immunofluorescence and FACS, respectively. Results: SKOV3 and OVCAR8 SP cells were shown to express higher levels of DUSP6 and lower levels of CyclinD3 compared with non-SP (NSP) cells (P<0.001). Among 39 ovarian cancer tissue samples, expression of DUSP6 in the chemotherapy-resistant group (12 samples) was higher than in the chemotherapy-sensitive group (27 samples) (P<0.05). While a lower level of expression of CyclinD3 was seen in the chemotherapy-resistant group, it was not statistically different from the chemotherapy-sensitive group. HO8910 cells where shown to have higher IC50 to cisplatin than SKOV3 or OVCAR8 cells, and this correlated with higher levels of DUSP6 expression. Overexpression of DUSP6 in SKOV3 cells led to an increase in cisplatin IC50 values (P<0.05), and also markedly reduced the expression levels of phospho-ERK1/2 and CyclinD3 and to the predominance of cells in the G0/G1 phase. Conclusion: Our findings reveal an enhancement of chemotherapy-resistance and a predominance of cells in G1 cell cycle arrest in DUSP6-overexpressing ovarian cancer cells. This suggests that overexpression of DUSP6 promotes chemotherapy-resistance through the negative regulation of the ERK signaling pathway, increasing the G0/G1 phase ratio among ovarian cancer cells, and leading to cellular quiescence.

Project description:Epithelial ovarian carcinoma (EOC) is an aggressive tumor often diagnosed at an advanced stage, when there is little or no prospect of cure. Despite advances in surgical and chemotherapeutic strategies, only marginal improvements in patient outcome have been obtained. Hence, unraveling the biological mechanisms underpinning EOC progression is critical for improving patients' survival. Recently, we reported that CD157 (an ectoenzyme regulating leukocyte diapedesis) is expressed in EOC and that high expression of the molecule is negatively correlated with the disease outcome in patients. Here, we demonstrate that forced overexpression of CD157 in OVCAR-3, TOV-21G, A2780 and OV-90 ovarian cancer cell lines promotes morphological and phenotypic changes characterized by disruption of intercellular junctions, downregulation of epithelial markers and upregulation of mesenchymal ones. These changes in cell shape and phenotype bring to reduced sensitivity to anoikis, increased anchorage-independent growth, cell motility and mesothelial invasion. Conversely, knockdown of CD157 in OV-90 and OC314 cells reverts the mesenchymal phenotype and reduces the cells' migratory potential. Transcriptome profiling analysis highlighted 378 significantly differentially expressed genes, representing the signature of CD157-overexpressing OVCAR-3 and OV-90 cells. The modulation of selected genes translates into alteration of protein expression that give cells a highly malignant phenotype. The overall picture deduced from the analysis of the modulated transcripts is that high expression of CD157 strengthens a number of biological processes favoring tumor progression (including development and cell motility), and weakens several biological processes hindering tumor progression (such as apoptosis, cell death and response to stress). Together, these findings implicate CD157 in the progression of EOC to metastatic disease and suggest that CD157 may represent a valuable therapeutic target.

Dataset Information

Overexpression of piRNA pathway genes in epithelial ovarian cancer.

Publications

Overexpression of piRNA pathway genes in epithelial ovarian cancer.

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