The limitations of current anti-angiogenic therapies necessitate other targets with complimentary mechanisms. Here, we show for the first time that soluble E-cadherin (sE-cad) (an 80-kDa soluble ...form), which is highly expressed in the malignant ascites of ovarian cancer patients, is a potent inducer of angiogenesis. In addition to ectodomain shedding, we provide further evidence that sE-cad is abundantly released in the form of exosomes. Mechanistically, sE-cad-positive exosomes heterodimerize with VE-cadherin on endothelial cells and transduce a novel sequential activation of β-catenin and NFκB signaling. In vivo and clinical data prove the relevance of sE-cad-positive exosomes for malignant ascites formation and widespread peritoneal dissemination. These data advance our understanding of the molecular regulation of angiogenesis in ovarian cancer and support the therapeutic potential of targeting sE-cad. The exosomal release of sE-cad, which represents a common route for externalization in ovarian cancer, could potentially be biomarkers for diagnosis and prognosis.
Drug resistance is an obstacle to the treatment of ovarian cancer. Using a unique cell model, we have proven previously that a subpopulation of ovarian cancer cells is more resistant to cisplatin ...than are the original cells. MicroRNAs (miRNAs), small noncoding RNAs, are involved in many biological events in cancer cells. In our study, we explored whether miRNAs are involved in cisplatin resistance of ovarian cancer cells. Cisplatin‐resistant cells expressed a lower level of miR‐29a/b/c. Manipulation of microRNA‐29 (miR‐29) expression modulated cisplatin sensitivity of CP70, HeyC2, SKOV3 and A2780 ovarian cancer cells. Knockdown of miR‐29a/b/c increased the ability of cells to escape cisplatin‐induced cell death partly through upregulation of collagen type I alpha 1 (COL1A1) and increased the activation of extracellular signal‐regulated kinase 1/2 and inactivation of glycogen synthase kinase 3 beta. When combined with cisplatin treatment, knockdown of miR‐29 decreased the amount of the active form of caspase‐9 and caspase‐3. Ectopic expression of miR‐29 alone or in combination with cisplatin treatment efficaciously reduced the tumorigenicity of CP70 cells in vivo. Our data show that downregulation of miR‐29 increases cisplatin resistance in ovarian cancer cells. Taken together, these data suggest that overexpression of miR‐29 is a potential sensitizer to cisplatin treatment that may have therapeutic implications.
What's new?
MicroRNAs (miRNAs) are small, noncoding RNAs that are involved in a number of processes in cancer cells. In this study, the authors found that overexpression of miR‐29 can reduce drug resistance in ovarian cancer cells, in part through increased expression of collagen. Ectopic expression of miR‐29 alone or in combination with cisplatin treatment also reduced the tumorigenicity of CP70 cells in vivo. These data suggest that overexpression of miR‐29 may sensitize tumor cells to cisplatin treatment, and that this miRNA may therefore have therapeutic potential.
Pyruvate kinase M2 (PKM2) regulates glycolysis and oxidative phosphorylation; however, the role of PKM2 in ovarian cancer remains largely unknown. We investigated whether ovarian cancer metabolism ...could provide insight into the development of therapeutic strategies. We performed immunohistochemical staining for PKM2 on a tissue microarray for multivariate analysis. It revealed that patients exhibiting higher PKM2 expression were significantly associated with malignancy groups (p < 0.001) and pathogenesis models (p < 0.001), had poor progression-free survival rates (p = 0.01) as compared with patients exhibiting lower PKM2 levels, and yielded a hazard ratio of death of 2.02 (95% confidence interval: 0.70-5.85). In cell lines, PKM2 inhibitor significantly inhibited the glycolytic rate according to cellular glucose consumption (p < 0.001). We also utilized Seahorse assays to assess metabolism-related cell-specific factors and the impact of PKM2 inhibitors. Energy shifts as per Seahorse analysis showed attenuation of the extracellular acidification rate (p < 0.05) and no significant difference in oxygen-consumption rate in SKOV3 cells. Treatment with PKM2 inhibitor suppressed ovarian cancer growth and cell migration in vitro and inhibited tumor growth without significant toxicity in a xenograft study. PKM2 inhibition disturbed Warburg effects and inhibited ovarian cancer cell growth. Targeting PKM2 may constitute a promising therapy for patients with ovarian cancer, and clinical trials involving shikonin are warranted.
Ovarian high‐grade serous carcinoma (HGSC) is the most lethal gynecological malignancy. Prevailing evidences suggest that drug resistance and recurrence of ovarian HGSC are caused by the presence of ...cancer stem cells. Therefore, targeting cancer stems is appealing, however, all attempts to date, have failed. To circumvent this limit, we analyzed differential transcriptomes at early differentiation of ovarian HGSC stem cells and identified the developmental transcription factor GATA3 as highly expressed in stem, compared to progenitor cells. GATA3 expression associates with poor prognosis of ovarian HGSC patients, and was found to recruit the histone H3, lysine 27 (H3K27) demethylase, UTX, activate stemness markers, and promote stem‐like phenotypes in ovarian HGSC cell lines. Targeting UTX by its inhibitor, GSKJ4, impeded GATA3‐driven stemness phenotypes, and enhanced apoptosis of GATA3‐expressing cancer cells. Combinations of gemcitabine or paclitaxel with GSKJ4, resulted in a synergistic cytotoxic effect. Our findings provide evidence for a new role for GATA3 in ovarian HGSC stemness, and demonstrate that GATA3 may serve as a biomarker for precision epigenetic therapy in the future.
What's new?
Cancer stem cells (CSCs) routinely evade conventional cancer therapies and fuel tumor regrowth. However, while CSC targeting is an appealing therapeutic strategy, studies are needed to better understand CSC differentiation. Here, in multipotent CSCs from ovarian high‐grade serous carcinomas (HGSCs), complexes consisting of the stemness regulator GATA3 and the histone demethylase UTX were found to maintain cancer stemness via epigenetic activation of c‐MYC, CD44, and NANOG. GATA3 was further identified as an independent risk factor in early‐stage ovarian HGSC. The results suggest that GATA3 is a prognostic marker in ovarian tumorigenesis and that targeting GATA3/UTX is a promising therapeutic approach.
Mucinous type of epithelial ovarian cancer (MuOC) is a unique subtype with a poor survival outcome in recurrent and advanced stages. The role of type‐specific epigenomics and its clinical ...significance remains uncertain. We analyzed the methylomic profiles of 6 benign mucinous adenomas, 24 MuOCs, 103 serous type of epithelial ovarian cancers (SeOCs) and 337 nonepithelial ovarian cancers. MuOC and SeOC exhibited distinct DNA methylation profiles comprising 101 genes, 81 of which exhibited low methylation in MuOC and were associated with the response to glucocorticoid, ATP hydrolysis‐coupled proton transport, proteolysis involved in the cellular protein catabolic process and ion transmembrane transport. Hierarchical clustering analysis showed that the profiles of MuOC were similar to colorectal adenocarcinoma and stomach adenocarcinoma. Genetic interaction network analysis of differentially methylated genes in MuOC showed a dominant network module is the proteasome subunit beta (PSMB) family. Combined functional module and methylation analysis identified PSMB8 as a candidate marker for MuOC. Immunohistochemical staining of PSMB8 used to validate in 94 samples of ovarian tumors (mucinous adenoma, MuOC or SeOC) and 62 samples of gastrointestinal cancer. PSMB8 was commonly expressed in MuOC and gastrointestinal cancer samples, predominantly as strong cytoplasmic and occasionally weak nuclei staining, but was not expressed in SeOC samples. Carfilzomib, a second‐generation proteasome inhibitor, suppressed MuOC cell growth in vitro. This study unveiled a mucinous‐type‐specific methylation profile and suggests the potential use of a proteasome inhibitor to treat MuOC.
What's new?
Epigenetic changes such as DNA methylation play an important role in cancer development. In this study, the authors found that mucinous epithelial ovarian cancers (MuOC) display changes in methylation similar to those seen in colorectal and gastric cancers, especially in the proteasome system. They also found that a proteasome subunit called PSMB8 may provide a useful diagnostic marker for MuOC, and that proteasome inhibitors blocked the growth of MuOC cells. These results suggest that the proteasome system may offer a useful target for both diagnosis and treatment of MuOC.
Cancer cells exhibit phenotypic plasticity during epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) involving intermediate states. To study genome-wide epigenetic ...remodeling associated with EMT plasticity, we integrate the analyses of DNA methylation, ChIP-sequencing of five histone marks (H3K4me1, H3K4me3, H3K27Ac, H3K27me3 and H3K9me3) and transcriptome profiling performed on ovarian cancer cells with different epithelial/mesenchymal states and on a knockdown model of EMT suppressor Grainyhead-like 2 (GRHL2). We have identified differentially methylated CpG sites associated with EMT, found at promoters of epithelial genes and GRHL2 binding sites. GRHL2 knockdown results in CpG methylation gain and nucleosomal remodeling (reduction in permissive marks H3K4me3 and H3K27ac; elevated repressive mark H3K27me3), resembling the changes observed across progressive EMT states. Epigenetic-modifying agents such as 5-azacitidine, GSK126 and mocetinostat further reveal cell state-dependent plasticity upon GRHL2 overexpression. Overall, we demonstrate that epithelial genes are subject to epigenetic control during intermediate phases of EMT/MET involving GRHL2.
Using DNA methylation biomarkers in cancer detection is a potential direction in clinical testing. Some methylated genes have been proposed for cervical cancer detection; however, more reliable ...methylation markers are needed. To identify new hypermethylated genes in the discovery phase, we compared the methylome between a pool of DNA from normal cervical epithelium (n = 19) and a pool of DNA from cervical cancer tissues (n = 38) using a methylation bead array. We integrated the differentially methylated genes with public gene expression databases, which resulted in 91 candidate genes. Based on gene expression after demethylation treatment in cell lines, we confirmed 61 genes for further validation. In the validation phase, quantitative MSP and bisulfite pyrosequencing were used to examine their methylation level in an independent set of clinical samples. Fourteen genes, including ADRA1D, AJAP1, COL6A2, EDN3, EPO, HS3ST2, MAGI2, POU4F3, PTGDR, SOX8, SOX17, ST6GAL2, SYT9, and ZNF614, were significantly hypermethylated in CIN3+ lesions. The sensitivity, specificity, and accuracy of POU4F3 for detecting CIN3+ lesions were 0.88, 0.82, and 0.85, respectively. A bioinformatics function analysis revealed that AJAP1, EDN3, EPO, MAGI2, and SOX17 were potentially implicated in β‐catenin signaling, suggesting the epigenetic dysregulation of this signaling pathway during cervical cancer development. The concurrent methylation of multiple genes in cancers and in subsets of precancerous lesions suggests the presence of a driver of methylation phenotype in cervical carcinogenesis. Further validation of these new genes as biomarkers for cervical cancer screening in a larger population‐based study is warranted.
What's New?
The identification of novel genes that are hypermethylated in cancer and precancerous lesions is needed in order to achieve a better sensitivity and specificity in cervical cancer screening. Using a genome‐wide approach, here the authors identified 14 genes that were frequently hypermethylated in CIN3+ and might thus become useful biomarkers in future molecular cervical cancer screening. A bioinformatics function analysis revealed that five of these genes were potentially implicated in β‐catenin signaling, suggesting the epigenetic dysregulation of Wnt signaling during cervical cancer development. The concurrent hypermethylation of multiple genes also suggests the involvement of a CpG island methylator phenotype.
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