Distinct DNA methylation profiles in ovarian serous neoplasms and their implications in ovarian carcinogenesis

The Diversity of Methylation Patterns in Serous Borderline Ovarian Tumors and Serous Ovarian Carcinomas

Background: Changes in DNA methylation patterns are a pivotal mechanism of carcinogenesis. In some tumors, aberrant methylation precedes genetic changes, while gene expression may be more frequently modified due to methylation alterations than by mutations. Methods: Herein, 128 serous ovarian tumors were analyzed, including borderline ovarian tumors (BOTS) with (BOT.V600E) and without (BOT) the BRAF V600E mutation, low-grade (lg), and high-grade (hg) ovarian cancers (OvCa). The methylome of the samples was profiled with Infinium MethylationEPIC microarrays. Results: The biggest number of differentially methylated (DM) CpGs and regions (DMRs) was found between lgOvCa and hgOvCa. By contrast, the BOT.V600E tumors had the lowest number of DM CpGs and DMRs compared to all other groups and, in relation to BOT, their genome was strongly downmethylated. Remarkably, the ten most significant DMRs, discriminating BOT from lgOvCa, encompassed the MHC region on chromosome 6. We also identified hundreds of DMRs, being of potential use as predictive biomarkers in BOTS and hgOvCa. DMRs with the best discriminative capabilities overlapped the following genes: BAIAP3, IL34, WNT10A, NEU1, SLC44A4, and HMOX1, TCN2, PES1, RP1-56J10.8, ABR, NCAM1, RP11-629G13.1, AC006372.4, NPTXR in BOTS and hgOvCa, respectively. Conclusions: The global genome-wide hypomethylation positively correlates with the increasing aggressiveness of ovarian tumors. We also assume that the immune system may play a pivotal role in the transition from BOTS to lgOvCa. Given that the BOT.V600E tumors had the lowest number of DM CpGs and DMRs compared to all other groups, when methylome is considered, such tumors might be placed in-between BOT and OvCa.

Molecular Analysis of High-Grade Serous Ovarian Carcinoma Exhibiting Low-Grade Serous Carcinoma and Serous Borderline Tumor

Ovarian cancer is classified as type 1 or 2, representing low- and high-grade serous carcinoma (LGSC and HGSC), respectively. LGSC arises from serous borderline tumor (SBT) in a stepwise manner, while HGSC develops from serous tubal intraepithelial carcinoma (STIC). Rarely, HGSC develops from SBT and LGSC. Herein, we describe the case of a patient with HGSC who presented with SBT and LGSC, and in whom we analyzed the molecular mechanisms of carcinogenesis. We performed primary debulking surgery, resulting in a suboptimal simple total hysterectomy and bilateral salpingo-oophorectomy due to strong adhesions. The diagnosis was stage IIIC HGSC, pT3bcN0cM0, but the tumor contained SBT and LGSC lesions. After surgery, TC (Paclitaxel + Carbopratin) + bevacizumab therapy was administered as adjuvant chemotherapy followed by bevacizumab as maintenance therapy. The tumor was chemo-resistant and caused ileus, and bevacizumab therapy was conducted only twice. Next-Generation Sequencing revealed KRAS (p.G12V) and NF2 (p.W184*) mutations in all lesions. Interestingly, the TP53 mutation was not detected in every lesion, and immunohistochemistry showed those lesions with wild-type p53. MDM2 was amplified in the HGSC lesions. DNA methylation analysis did not show differentially methylated regions. This case suggests that SBT and LGSC may transform into HGSC via p53 dysfunction due to MDM2 amplification.

The Roles of Histone Deacetylases in the Regulation of Ovarian Cancer Metastasis

Ovarian cancer is the most lethal gynecologic malignancy, and metastasis is the major cause of death in patients with ovarian cancer, which is regulated by the coordinated interplay of genetic and epigenetic mechanisms. Histone deacetylases (HDACs) are enzymes that can catalyze the deacetylation of histone and some non-histone proteins and that are involved in the regulation of a variety of biological processes via the regulation of gene transcription and the functions of non-histone proteins such as transcription factors and enzymes. Aberrant expressions of HDACs are common in ovarian cancer. Many studies have found that HDACs are involved in regulating a variety of events associated with ovarian cancer metastasis, including cell migration, invasion, and the epithelial-mesenchymal transformation. Herein, we provide a brief overview of ovarian cancer metastasis and the dysregulated expression of HDACs in ovarian cancer. In addition, we discuss the roles of HDACs in the regulation of ovarian cancer metastasis. Finally, we discuss the development of compounds that target HDACs and highlight their importance in the future of ovarian cancer therapy.

Current and Emerging Methods for Ovarian Cancer Screening and Diagnostics: A Comprehensive Review

With a 5-year survival rate of less than 50%, ovarian high-grade serous carcinoma (HGSC) is one of the most highly aggressive gynecological malignancies affecting women today. The high mortality rate of HGSC is largely attributable to delays in diagnosis, as most patients remain undiagnosed until the late stages of -disease. There are currently no recommended screening tests for ovarian cancer and there thus remains an urgent need for new diagnostic methods, particularly those that can detect the disease at early stages when clinical intervention remains effective. While diagnostics for ovarian cancer share many of the same technical hurdles as for other cancer types, the low prevalence of the disease in the general population, coupled with a notable lack of sensitive and specific biomarkers, have made the development of a clinically useful screening strategy particularly challenging. Here, we present a detailed review of the overall landscape of ovarian cancer diagnostics, with emphasis on emerging methods that employ novel protein, genetic, epigenetic and imaging-based biomarkers and/or advanced diagnostic technologies for the noninvasive detection of HGSC, particularly in women at high risk due to germline mutations such as BRCA1/2. Lastly, we discuss the translational potential of these approaches for achieving a clinically implementable solution for screening and diagnostics of early-stage ovarian cancer as a means of ultimately improving patient outcomes in both the general and high-risk populations.

The Origin of Ovarian Cancer Species and Precancerous Landscape

Unlike other human cancers, in which all primary tumors arise de novo, ovarian epithelial cancers are primarily imported from either endometrial or fallopian tube epithelium. The prevailing paradigm in the genesis of high-grade serous carcinoma (HGSC), the most common ovarian cancer, posits to its development in fallopian tubes through stepwise tumor progression. Recent progress has been made not only in gathering terabytes of omics data but also in detailing the histologic-molecular correlations required for looking into, and making sense of, the tissue origin of HGSC. This emerging paradigm is changing many facets of ovarian cancer research and routine gynecology practice. The precancerous landscape in fallopian tubes contains multiple concurrent precursor lesions, including serous tubal intraepithelial carcinoma (STIC), with genetic heterogeneity providing a platform for HGSC evolution. Mathematical models imply that a prolonged time (decades) elapses from the development of a TP53 mutation, the earliest known molecular alteration, to an STIC, followed by a shorter span (6 years) for progression to an HGSC. Genetic predisposition accelerates the trajectory. This timeline may allow for the early diagnosis of HGSC and STIC, followed by intent-to-cure surgery. This review discusses the recent advances in this tubal paradigm and its biological and clinical implications, alongside the promise and challenge of studying STIC and other precancerous lesions of HGSC.

Insight updating of the molecular hallmarks in ovarian carcinoma

Background and purpose

Ovarian cancer (OC) is the deadliest gynaecologic cancer characterised by a high heterogeneity not only at the clinical point of view but also at the molecular level. This review focuses on the new insights about the OC molecular classification.

Materials and methods

We performed a bibliographic search for different indexed articles focused on the new molecular classification of OC. All of them have been published in PubMed and included information about the most frequent molecular alterations in OC confirmed by omics approaches. In addition, we have extracted information about the role of liquid biopsy in the OC diagnosis and prognosis.

Results

New molecular insights into OC have allowed novel clinical entities to be defined. Among OC, high-grade serous ovarian carcinoma (HGSOC) which is the most common OC is characterised by omics approaches, mutations in TP53 and in other genes involved in the homologous recombination repair, especially BRCA1/2. Recent studies in HGSOC have allowed a new molecular classification in subgroups according to their mutational, transcriptional, methylation and copy number variation signatures with a real impact in the characterisation of new therapeutic targets for OC to be defined. Furthermore, despite the intrinsic intra-tumour heterogeneity, the advances in next generation sequencing (NGS) analyses of ascetic liquid from OC have opened new ways for its characterisation and treatment.

Conclusions

The advances in genomic approaches have been used for the identification of new molecular profiling techniques which define OC subgroups and has supposed advances in the diagnosis and in the personalised treatment of OC.

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Classification of ovarian cancer regarding to widespread genetic and genomic data.

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Highlighted role of p53 and BRCA1/2 in ovarian cancer for diagnosis and treatment.

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Intra-tumour genetic heterogeneity in ovarian cancer.

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Useful of liquid biopsy study in ovarian cancer diagnosis.

Reprogramming of Ovarian Granulosa Cells by YAP1 Leads to Development of High-Grade Cancer with Mesenchymal Lineage and Serous Features

Understanding the cell-of-origin of ovarian high grade serous cancer (HGSC) is the prerequisite for efficient prevention and early diagnosis of this most lethal gynecological cancer. Recently, a mesenchymal type of ovarian HGSC with the poorest prognosis among ovarian cancers was identified by both TCGA and AOCS studies. The cell-of-origin of this subtype of ovarian cancer is unknown. While pursuing studies to understand the role of the Hippo pathway in ovarian granulosa cell physiology and pathology, we unexpectedly found that the Yes-associated protein 1 (YAP1), the major effector of the Hippo signaling pathway, induced dedifferentiation and reprogramming of the ovarian granulosa cells, a unique type of ovarian follicular cells with mesenchymal lineage and high plasticity, leading to the development of high grade ovarian cancer with serous features. Our research results unveil a potential cell-of-origin for a subtype of HGSC with mesenchymal features.

Epigenetics in ovarian cancer

Ovarian cancer is a disease with a poor prognosis and little progress has been made to improve treatment. It is now recognized that there are several histotypes of ovarian cancer, each with distinct epidemiologic and genomic characteristics. Cancer therapy is moving beyond classical chemotherapy to include epigenetic approaches. Epigenetics is the dynamic regulation of gene expression by DNA methylation and histone post translational modification in response to environmental cues. Improvement in technology to study DNA methylation has enabled a more agnostic approach and, with larger samples sets, has begun to unravel how epigenetics contributes to the etiology, response to chemotherapy and prognosis in of ovarian cancer. Investigations into histone modifications in ovarian cancer are more nascent. Much more is needed to be done to fully realize the potential that epigenetics holds for ovarian cancer clinical care.

One-Carbon Metabolism: Biological Players in Epithelial Ovarian Cancer

Metabolism is deeply involved in cell behavior and homeostasis maintenance, with metabolites acting as molecular intermediates to modulate cellular functions. In particular, one-carbon metabolism is a key biochemical pathway necessary to provide carbon units required for critical processes, including nucleotide biosynthesis, epigenetic methylation, and cell redox-status regulation. It is, therefore, not surprising that alterations in this pathway may acquire fundamental importance in cancer onset and progression. Two of the major actors in one-carbon metabolism, folate and choline, play a key role in the pathobiology of epithelial ovarian cancer (EOC), the deadliest gynecological malignancy. EOC is characterized by a cholinic phenotype sustained via increased activity of choline kinase alpha, and via membrane overexpression of the alpha isoform of the folate receptor (FRα), both of which are known to contribute to generating regulatory signals that support EOC cell aggressiveness and proliferation. Here, we describe in detail the main biological processes associated with one-carbon metabolism, and the current knowledge about its role in EOC. Moreover, since the cholinic phenotype and FRα overexpression are unique properties of tumor cells, but not of normal cells, they can be considered attractive targets for the development of therapeutic approaches.

MicroRNA‑665 suppresses the growth and migration of ovarian cancer cells by targeting HOXA10

Ovarian cancer is the most lethal gynecological cancer and its metastasis leads to a poor prognosis. The present study was designed to elucidate how microRNA (miR)-665 regulates the proliferation and migration of ovarian tumor cells. Reverse transcription-polymerase chain reaction (RT-PCR) demonstrated that miR-665 expression was decreased in ovarian cancer tissues. Increased expression of miR-665 suppressed the growth and migration of ovarian cancer cells, whereas the downregulated expression of miR-665 led to the opposite results. Bioinformatics tools identified homeobox A10 (HOXA10) as a target of miR-665. Following miR-665 overexpression, HOXA10 protein expression was significantly reduced. A dual luciferase assay revealed that miR-665 bound to the 3′-untranslated region of HOXA10. Immunohistochemistry and RT-PCR revealed that the expression of HOXA10 was negatively correlated with the expression of miR-665. It was concluded that miR-665 targets HOXA10 and may act as a tumor-suppressing gene in ovarian cancer. This pathway may be involved in the development and metastasis of ovarian cancer.

Distinct DNA Methylation Profiles in Ovarian Tumors: Opportunities for Novel Biomarkers

Aberrant methylation of multiple promoter CpG islands could be related to the biology of ovarian tumors and its determination could help to improve treatment strategies. DNA methylation profiling was performed using the Methylation Ligation-dependent Macroarray (MLM), an array-based analysis. Promoter regions of 41 genes were analyzed in 102 ovarian tumors and 17 normal ovarian samples. An average of 29% of hypermethylated promoter genes was observed in normal ovarian tissues. This percentage increased slightly in serous, endometrioid, and mucinous carcinomas (32%, 34%, and 45%, respectively), but decreased in germ cell tumors (20%). Ovarian tumors had methylation profiles that were more heterogeneous than other epithelial cancers. Unsupervised hierarchical clustering identified four groups that are very close to the histological subtypes of ovarian tumors. Aberrant methylation of three genes (BRCA1, MGMT, and MLH1), playing important roles in the different DNA repair mechanisms, were dependent on the tumor subtype and represent powerful biomarkers for precision therapy. Furthermore, a promising relationship between hypermethylation of MGMT, OSMR, ESR1, and FOXL2 and overall survival was observed. Our study of DNA methylation profiling indicates that the different histotypes of ovarian cancer should be treated as separate diseases both clinically and in research for the development of targeted therapies.

LncRNAs expression profiling in normal ovary, benign ovarian cyst and malignant epithelial ovarian cancer

Long noncoding RNA (lncRNA) has been recognized as a regulator of gene expression, and the dysregulation of lncRNAs is involved in the progression of many types of cancer, including epithelial ovarian cancer (EOC). To explore the potential roles of lncRNAs in EOC, we performed lncRNA and mRNA microarray profiling in malignant EOC, benign ovarian cyst and healthy control tissues. In this study, 663 transcripts of lncRNAs were found to be differentially expressed in malignant EOC compared with benign and normal control tissues. We also selected 18 altered lncRNAs to confirm the validity of the microarray analysis using quantitative real-time PCR (qPCR). Pathway and Gene Ontology (GO) analyses demonstrated that these altered transcripts were involved in multiple biological processes, especially the cell cycle. Furthermore, Series Test of Cluster (STC) and lncRNA-mRNA co-expression network analyses were conducted to predict lncRNA expression trends and the potential target genes of lncRNAs. We also determined that two antisense lncRNAs (RP11-597D13.9 and ADAMTS9-AS1) were associated with their nearby coding genes (FAM198B, ADAMTS9), which participated in cancer progression. This study offers helpful information to understand the initiation and development mechanisms of EOC.

Genome-wide methylation profiling of ovarian cancer patient-derived xenografts treated with the demethylating agent decitabine identifies novel epigenetically regulated genes and pathways

Background

In high-grade serous ovarian cancer (HGSOC), intrinsic and/or acquired resistance against platinum-containing chemotherapy is a major obstacle for successful treatment. A low frequency of somatic mutations but frequent epigenetic alterations, including DNA methylation in HGSOC tumors, presents the cancer epigenome as a relevant target for innovative therapy. Patient-derived xenografts (PDXs) supposedly are good preclinical models for identifying novel drug targets. However, the representativeness of global methylation status of HGSOC PDXs compared to their original tumors has not been evaluated so far. Aims of this study were to explore how representative HGSOC PDXs are of their corresponding patient tumor methylome and to evaluate the effect of epigenetic therapy and cisplatin on putative epigenetically regulated genes and their related pathways in PDXs.

Methods

Genome-wide analysis of the DNA methylome of HGSOC patients with their corresponding PDXs, from different generations, was performed using Infinium 450 K methylation arrays. Furthermore, we analyzed global methylome changes after treatment of HGSOC PDXs with the FDA approved demethylating agent decitabine and cisplatin. Findings were validated by bisulfite pyrosequencing with subsequent pathway analysis. Publicly available datasets comprising HGSOC patients were used to analyze the prognostic value of the identified genes.

Results

Only 0.6–1.0 % of all analyzed CpGs (388,696 CpGs) changed significantly (p < 0.01) during propagation, showing that HGSOC PDXs were epigenetically stable. Treatment of F3 PDXs with decitabine caused a significant reduction in methylation in 10.6 % of CpG sites in comparison to untreated PDXs (p < 0.01, false discovery rate <10 %). Cisplatin treatment had a marginal effect on the PDX methylome. Pathway analysis of decitabine-treated PDX tumors revealed several putative epigenetically regulated pathways (e.g., the Src family kinase pathway). In particular, the C-terminal Src kinase (CSK) gene was successfully validated for epigenetic regulation in different PDX models and ovarian cancer cell lines. Low CSK methylation and high CSK expression were both significantly associated (p < 0.05) with improved progression-free survival and overall survival in HGSOC patients.

Conclusions

HGSOC PDXs resemble the global epigenome of patients over many generations and can be modulated by epigenetic drugs. Novel epigenetically regulated genes such as CSK and related pathways were identified in HGSOC. Our observations encourage future application of PDXs for cancer epigenome studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s13073-016-0361-5) contains supplementary material, which is available to authorized users.

The green tea polyphenol EGCG alleviates maternal diabetes-induced neural tube defects by inhibiting DNA hypermethylation

BACKGROUND

Maternal diabetes increases the risk of neural tube defects in offspring. Our previous study demonstrated that the green tea polyphenol, Epigallocatechin gallate, inhibits high glucose-induced neural tube defects in cultured embryos. However, the therapeutic effect of Epigallocatechin gallate on maternal diabetes-induced neural tube defects is still unclear.

OBJECTIVE

We aimed to examine whether Epigallocatechin gallate treatment can reduce maternal diabetes-induced DNA methylation and neural tube defects.

STUDY DESIGN

Nondiabetic and diabetic pregnant mice at embryonic day 5.5 were given drinking water with or without 1 or 10 μM Epigallocatechin gallate. At embryonic day 8.75, embryos were dissected from the visceral yolk sac for the measurement of the levels and activity of DNA methyltransferases, the levels of global DNA methylation, and methylation in the CpG islands of neural tube closure essential gene promoters. embryonic day 10.5 embryos were examined for neural tube defect incidence.

RESULTS

Epigallocatechin gallate treatment did not affect embryonic development because embryos from nondiabetic dams treated with Epigallocatechin gallate did not exhibit any neural tube defects. Treatment with 1 μM Epigallocatechin gallate did not reduce maternal diabetes-induced neural tube defects significantly. Embryos from diabetic dams treated with 10 μM Epigallocatechin gallate had a significantly lower neural tube defect incidence compared with that of embryos without Epigallocatechin gallate treatment. Epigallocatechin gallate reduced neural tube defect rates from 29.5% to 2%, an incidence that is comparable with that of embryos from nondiabetic dams. Ten micromoles of Epigallocatechin gallate treatment blocked maternal diabetes-increased DNA methyltransferases 3a and 3b expression and their activities, leading to the suppression of global DNA hypermethylation. Additionally, 10 μM Epigallocatechin gallate abrogated maternal diabetes-increased DNA methylation in the CpG islands of neural tube closure essential genes, including Grhl3, Pax3, and Tulp3.

CONCLUSION

Epigallocatechin gallate reduces maternal diabetes-induced neural tube defects formation and blocks the enhanced expression and activity of DNA methyltransferases, leading to the suppression of DNA hypermethylation and the restoration of neural tube closure essential gene expression. These observations suggest that Epigallocatechin gallate supplements could mitigate the teratogenic effects of hyperglycemia on the developing embryo and prevent diabetes-induced neural tube defects.

Molecular Mechanism Linking BRCA1 Dysfunction to High Grade Serous Epithelial Ovarian Cancers with Peritoneal Permeability and Ascites

Ovarian cancer constitutes the second most common gynecological cancer with a five-year survival rate of 40%. Among the various histotypes associated with hereditary ovarian cancer, high-grade serous epithelial ovarian carcinoma (HGSEOC) is the most predominant and women with inherited mutations in BRCA1 have a lifetime risk of 40-60%. HGSEOC is a challenge for clinical oncologists, due to late presentation of patient, diagnosis and high rate of relapse. Ovarian tumors have a wide range of clinical presentations including development of ascites as a result of deregulated endothelial function thereby causing increased vascular permeability of peritoneal vessels. The molecular mechanisms remain elusive. Studies have shown that fallopian tube cancers develop in women with BRCA1 gene mutations more often than previously suspected. Recent studies suggest that many primary peritoneal cancers and some high-grade serous epithelial ovarian carcinomas actually start in the fallopian tubes. In this article we have addressed the molecular pathway of a recently identified potential biomarker Ubc9 whose deregulated expression due to BRCA1 dysfunction can result in HGSEOC with peritoneal permeability and formation of ascites. We also discuss the role of downstream targets Caveolin-1 and Vascular Endothelial Growth Factor (VEGF) in the pathogenesis of ascites in ovarian carcinomas. Finally we hypothesize a signaling axis between Ubc9 over expression, loss of Caveolin-1 and induction of VEGF in BRCA1 mutant HGSEOC cells. We suggest that Ubc9-mediated stimulation of VEGF as a novel mechanism underlying ovarian cancer aggressiveness and ascites formation. Agents that target Ubc9 and VEGF signaling may represent a novel therapeutic strategy to impede peritoneal growth and spread of HGSEOC.

Gene methylation of human ovarian carcinoma stromal progenitor cells promotes tumorigenesis

Background

This study aimed to investigate whether the DNA methylation of human ovarian carcinoma stromal progenitor cells (OCSPCs) could promote the tumorigenesis of ovarian carcinoma.

Methods

OCSPCs were first isolated from fresh tumor tissues and ascites of ovarian cancer patients. In vivo and in vitro experiments on the effect of the OCSPCs on tumorigenesis and the effects of DNA demethylation on the OCSPCs were then performed.

Results

The OCSPCs possessed self-renewal and multipotent differentiation capacity with elevated expressions of OCT4, NANOG, BMP2, BMP4, Rex-1, AC133 and TGF-β. The OCSPCs, when combined with tumor cells in vivo could promote tumor growth. The methylation profiles of tumor suppressor genes (TSGs) were significantly higher in the OCSPCs than in ovarian cancer cells (p < 0.001). 5-aza-2-dC could alter the methylation levels of TSGs in OCSPCs and also inhibit the tumor promoting capabilities of the OCSPCs by decreasing the proliferation of tumors cells. The expression levels of TSGs were re-expressed by 5-aza-2-dC to inhibit the self-renewal and growth of OCSPCs.

Conclusions

OCSPCs with decreased TSG expressions in the ovarian tumor microenvironment were able to promote tumorigenesis which could be reversed by DNA demethylation. DNA demethylation reversing the expression of TSGs in OCSPCs may represent a potential therapeutic target for ovarian cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0722-7) contains supplementary material, which is available to authorized users.

DNA methylation changes in epithelial ovarian cancer histotypes

Survival after a diagnosis of ovarian cancer has not improved, and despite histological differences, treatment is similar for all cases. Understanding the molecular basis for ovarian cancer risk and prognosis is fundamental, and to this end much has been gleaned about genetic changes contributing to risk, and to a lesser extent, survival. There's considerable evidence for genetic differences between the four pathologically defined histological subtypes; however, the contribution of epigenetics is less well documented. In this report, we review alterations in DNA methylation in ovarian cancer, focusing on histological subtypes, and studies examining the roles of methylation in determining therapy response. As epigenetics is making its way into clinical care, we review the application of cell free DNA methylation to ovarian cancer diagnosis and care. Finally, we comment on recurrent limitations in the DNA methylation literature for ovarian cancer, which can and should be addressed to mature this field.

CD40 ligand induces RIP1-dependent, necroptosis-like cell death in low-grade serous but not serous borderline ovarian tumor cells

Ovarian high-grade serous carcinomas (HGSCs) and invasive low-grade serous carcinomas (LGSCs) are considered to be distinct entities. In particular, LGSCs are thought to arise from non-invasive serous borderline ovarian tumors (SBOTs) and show poor responsiveness to conventional chemotherapy. The pro-apoptotic effects of CD40 ligand (CD40L) have been demonstrated in HGSC, though the underlying mechanisms are not fully understood. Conversely, the therapeutic potential of the CD40L-CD40 system has yet to be evaluated in LGSC. We now show that CD40 protein is focally expressed on tumor cells in two of five primary LGSCs compared with no expression in eight primary SBOTs. Treatment with CD40L or agonistic CD40 antibody decreased the viability of LGSC-derived MPSC1 and VOA1312 cells, but not SBOT3.1 cells. Small interfering RNA (siRNA) targeting CD40 was used to show that it is required for these reductions in cell viability. CD40L treatment increased cleaved caspase-3 levels in MPSC1 cells though, surprisingly, neither pan-caspase inhibitor nor caspase-3 siRNA reversed or even attenuated CD40L-induced cell death. In addition, CD40-induced cell death was not affected by knockdown of the mitochondrial proteins apoptosis-inducing factor (AIF) and endonuclease G (EndoG). Interestingly, CD40L-induced cell death was blocked by necrostatin-1, an inhibitor of receptor-interacting protein 1 (RIP1), and attenuated by inhibitors of RIP3 (GSK'872) or MLKL (mixed lineage kinase domain-like; necrosulfonamide). Our results indicate that the upregulation of CD40 may be relatively common in LGSC and that CD40 activation induces RIP1-dependent, necroptosis-like cell death in LGSC cells.

Gene methylation profiles as prognostic markers in ovarian clear cell and endometrioid adenocarcinomas

Ovarian cancer is a cancer of high mortality. Aberrant gene methylation of tumor suppressor genes has been shown to be related to the development of malignancy. This study aimed to investigate the methylation of various genes in ovarian clear cell adenocarcinoma (OCCA) and ovarian endometrioid adenocarcinoma (OEA) and evaluate methylation biomarkers in terms of patient chemo-response and outcome. Eight candidate genes from 66 OCCA and 51 OEA patients were evaluated by methylation-specific polymerase chain reaction and capillary electrophoresis. Clinico-pathological parameters and patient outcomes were analyzed. The frequencies of gene methylation in RASSF1A (79% vs. 59%, p=0.025), E-cadherin (30% vs. 10%, p=0.011), and DLEC1 (71% vs. 43%, p=0.003) were higher in the patients with OCCA than in those with OEA. The chemo-resistant group had a significantly higher percentage of E-cadherin methylation (36.7% vs. 16.1%, p=0.036) than the chemo-sensitive group. In multivariate analysis (log-rank test), advanced stage (4.79 [2.10-10.94], p<0.001) was the only risk factor for mortality. Those with methylation of more than two out of three genes (E-cadherin, DLEC1, and SFRP5) had a shorter disease-free survival (1.89 [1.07-3.32], p=0.028) and overall survival (3.29 [1.57-6.87], p=0.002) than those with methylation of one or no gene. In advanced-stage malignancies, those with more than two out of the three gene methylations also had a shorter overall survival (3.86 [1.63-9.09], p=0.002) than those with methylation of only one or no gene. Patients with OCCA have different patterns of gene methylation than those with OEA. Methylation of the E-cadherin, DLEC1 and SFRP5 genes can be a prognostic biomarker for OCCA and OEA.

BRAF mutation is associated with a specific cell type with features suggestive of senescence in ovarian serous borderline (atypical proliferative) tumors

Serous borderline tumor also known as atypical proliferative serous tumor (APST) is the precursor of ovarian low-grade serous carcinoma (LGSC). In this study, we correlated the morphologic and immunohistochemical phenotypes of 71 APSTs and 18 LGSCs with the mutational status of KRAS and BRAF, the most common molecular genetic changes in these neoplasms. A subset of cells characterized by abundant eosinophilic cytoplasm (EC), discrete cell borders, and bland nuclei was identified in all (100%) 25 BRAF-mutated APSTs but in only 5 (10%) of 46 APSTs without BRAF mutations (P<0.0001). Among the 18 LGSCs, EC cells were found in only 2, and both contained BRAF mutations. The EC cells were present admixed with cuboidal and columnar cells lining the papillae and appeared to be budding from the surface, resulting in individual cells and clusters of detached cells "floating" above the papillae. Immunohistochemistry showed that the EC cells always expressed p16, a senescence-associated marker, and had a significantly lower Ki-67 labeling index than adjacent cuboidal and columnar cells (P=0.02). In vitro studies supported the interpretation that these cells were undergoing senescence, as the same morphologic features could be reproduced in cultured epithelial cells by ectopic expression of BRAF(V600E). Senescence was further established by markers such as SA-β-gal staining, expression of p16 and p21, and reduction in DNA synthesis. In conclusion, this study sheds light on the pathogenesis of this unique group of ovarian tumors by showing that BRAF mutation is associated with cellular senescence and the presence of a specific cell type characterized by abundant EC. This "oncogene-induced senescence" phenotype may represent a mechanism that impedes progression of APSTs to LGSC.

Intratumoral heterogeneity in a minority of ovarian low-grade serous carcinomas

Background

Ovarian low-grade serous carcinoma (LGSC) has fewer mutations than ovarian high-grade serous carcinoma (HGSC) and a less aggressive clinical course. However, an overwhelming majority of LGSC patients do not respond to conventional chemotherapy resulting in a poor long-term prognosis comparable to women diagnosed with HGSC. KRAS and BRAF mutations are common in LGSC, leading to clinical trials targeting the MAPK pathway. We assessed the stability of targetable somatic mutations over space and/or time in LGSC, with a view to inform stratified treatment strategies and clinical trial design.

Methods

Eleven LGSC cases with primary and recurrent paired samples were identified (stage IIB-IV). Tumor DNA was isolated from 1–4 formalin-fixed paraffin-embedded tumor blocks from both the primary and recurrence (n = 37 tumor and n = 7 normal samples). Mutational analysis was performed using the Ion Torrent AmpliSeq^TM Cancer Panel, with targeted validation using Fluidigm-MiSeq, Sanger sequencing and/or Raindance Raindrop digital PCR.

Results

KRAS (3/11), BRAF (2/11) and/or NRAS (1/11) mutations were identified in five unique cases. A novel, non-synonymous mutation in SMAD4 was observed in one case. No somatic mutations were detected in the remaining six cases. In two cases with a single matched primary and recurrent sample, two KRAS hotspot mutations (G12V, G12R) were both stable over time. In three cases with multiple samplings from both the primary and recurrent surgery some mutations (NRAS Q61R, BRAF V600E, SMAD4 R361G) were stable across all samples, while others (KRAS G12V, BRAF G469V) were unstable.

Conclusions

Overall, the majority of cases with detectable somatic mutations showed mutational stability over space and time while one of five cases showed both temporal and spatial mutational instability in presumed drivers of disease. Investigation of additional cases is required to confirm whether mutational heterogeneity in a minority of LGSC is a general phenomenon that should be factored into the design of clinical trials and stratified treatment for this patient population.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-982) contains supplementary material, which is available to authorized users.

The apoptosis associated tyrosine kinase gene is frequently hypermethylated in human cancer and is regulated by epigenetic mechanisms

Epigenetic gene inactivation through promoter hypermethylation is an important aberration involved in the silencing of tumor-associated genes in cancer. Here we identified the apoptosis associated tyrosine kinase (AATK) as an epigenetically downregulated tumor related gene. We analyzed the epigenetic regulation of AATK in several human cancer cell lines and normal tissues by methylation and expression analysis. Hypermethylation of AATK was also analyzed in 25 primary lung tumors, 30 breast cancers and 24 matching breast tissues. In normal tissues the AATK CpG island promoter was unmethylated and AATK was expressed. Hypermethylation of AATK occurred frequently in 13 out of 14 (93%) human cancer cell lines. Methylation was reversed by 5-aza-2′-deoxycytidine treatment leading to re-expression of AATK in cancer cell lines. Aberrant methylation of AATK was also revealed in primary lung (40%) and breast (53%) cancers, but was found to be significantly less methylated in matching normal breast tissues (17%; p<0.01). In addition, we observed that AATK is epigenetically reactivated through the chromatin regulator CTCF. We further show that overexpression of Aatk significantly suppresses colony formation in cancer cell lines. Our findings suggest that the apoptosis associated tyrosine kinase is frequently inactivated in human cancers and acts as a tumor suppressive gene.

KRAS (but not BRAF) mutations in ovarian serous borderline tumour are associated with recurrent low-grade serous carcinoma

BRAF and KRAS mutations in ovarian serous borderline tumours (OSBTs) and ovarian low-grade serous carcinomas (LGSCs) have been previously described. However, whether those OSBTs would progress to LGSCs or whether those LGSCs were developed from OSBT precursors in previous studies is unknown. Therefore, we assessed KRAS and BRAF mutations in tumour samples from 23 recurrent LGSC patients with a known initial diagnosis of OSBT. Paraffin blocks from both OSBT and LGSC samples were available for five patients, and either OSBTs or LGSCs were available for another 18 patients. Tumour cells from paraffin-embedded tissues were dissected out for mutation analysis by conventional polymerase chain reaction (PCR) and Sanger sequencing. Tumours that appeared to have wild-type KRAS by conventional PCR-Sanger sequencing were further analysed by full COLD (co-amplification at lower denaturation temperature)-PCR and deep sequencing. Full COLD-PCR was able to enrich the amplification of mutated alleles. Deep sequencing was performed with the Ion Torrent personal genome machine (PGM). By conventional PCR-Sanger sequencing, BRAF mutation was detected only in one patient and KRAS mutations were detected in ten patients. Full COLD-PCR deep sequencing detected low-abundance KRAS mutations in eight additional patients. Three of the five patients with both OSBT and LGSC samples available had the same KRAS mutations detected in both OSBT and LGSC samples. The remaining two patients had only KRAS mutations detected in their LGSC samples. For patients with either OSBT or LGSC samples available, KRAS mutations were detected in seven OSBT samples and six LGSC samples. Surprisingly, patients with the KRAS G12V mutation have shorter survival times. In summary, KRAS mutations are very common in recurrent LGSC, while BRAF mutations are rare. The findings indicate that recurrent LGSC can arise from proliferation of OSBT tumour cells with or without detectable KRAS mutations.

Tumor hypomethylation at 6p21.3 associates with longer time to recurrence of high-grade serous epithelial ovarian cancer

To reveal biologic mechanisms underlying clinical outcome of high-grade serous (HGS) epithelial ovarian carcinomas (EOC), we evaluated the association between tumor epigenetic changes and time to recurrence (TTR). We assessed methylation at approximately 450,000 genome-wide CpGs in tumors of 337 Mayo Clinic (Rochester, MN) patients. Semi-supervised clustering of discovery (n=168) and validation (n=169) sets was used to determine clinically relevant methylation classes. Clustering identified two methylation classes based on 60 informative CpGs, which differed in TTR in the validation set [R vs. L class, P=2.9×10(-3), HR=0.52; 95% confidence interval (CI), 0.34-0.80]. Follow-up analyses considered genome-wide tumor mRNA expression (n=104) and CD8 T-cell infiltration (n=89) in patient subsets. Hypomethylation of CpGs located in 6p21.3 in the R class associated with cis upregulation of genes enriched in immune response processes (TAP1, PSMB8, PSMB9, HLA-DQB1, HLA-DQB2, HLA-DMA, and HLA-DOA), increased CD8 T-cell tumor infiltration (P=7.6×10(-5)), and trans-regulation of genes in immune-related pathways (P=1.6×10(-32)). This is the most comprehensive assessment of clinical outcomes with regard to epithelial ovarian carcinoma tumor methylation to date. Collectively, these results suggest that an epigenetically mediated immune response is a predictor of recurrence and, possibly, treatment response for HGS EOC.

Promoter methylation of AREG, HOXA11, hMLH1, NDRG2, NPTX2 and Tes genes in glioblastoma

Epigenetic alterations alone or in combination with genetic mechanisms play a key role in brain tumorigenesis. Glioblastoma is one of the most common, lethal and poor clinical outcome primary brain tumors with extraordinarily miscellaneous epigenetic alterations profile. The aim of this study was to investigate new potential prognostic epigenetic markers such as AREG, HOXA11, hMLH1, NDRG2, NTPX2 and Tes genes promoter methylation, frequency and value for patients outcome. We examined the promoter methylation status using methylation-specific polymerase chain reaction in 100 glioblastoma tissue samples. The value for clinical outcome was calculated using Kaplan-Meier estimation with log-rank test. DNA promoter methylation was frequent event appearing more than 45 % for gene. AREG and HOXA11 methylation status was significantly associated with patient age. HOXA11 showed the tendency to be associated with patient outcome in glioblastomas. AREG gene promoter methylation showed significant correlation with poor patient outcome. AREG methylation remained significantly associated with patient survival in a Cox multivariate model including MGMT promoter methylation status. This study of new epigenetic targets has shown considerably high level of analyzed genes promoter methylation variability in glioblastoma tissue. AREG gene might be valuable marker for glioblastoma patient survival prognosis, however further analysis is needed to clarify the independence and appropriateness of the marker.

Epigenome-wide ovarian cancer analysis identifies a methylation profile differentiating clear-cell histology with epigenetic silencing of the HERG K+ channel

Ovarian cancer remains the leading cause of death in women with gynecologic malignancies, despite surgical advances and the development of more effective chemotherapeutics. As increasing evidence indicates that clear-cell ovarian cancer may have unique pathogenesis, further understanding of molecular features may enable us to begin to understand the underlying biology and histology-specific information for improved outcomes. To study epigenetics in clear-cell ovarian cancer, fresh frozen tumor DNA (n = 485) was assayed on Illumina Infinium HumanMethylation450 BeadChips. We identified a clear-cell ovarian cancer tumor methylation profile (n = 163) which we validated in two independent replication sets (set 1, n = 163; set 2, n = 159), highlighting 22 CpG loci associated with nine genes (VWA1, FOXP1, FGFRL1, LINC00340, KCNH2, ANK1, ATXN2, NDRG21 and SLC16A11). Nearly all of the differentially methylated CpGs showed a propensity toward hypermethylation among clear-cell cases. Several loci methylation inversely correlated with tumor gene expression, most notably KCNH2 (HERG, a potassium channel) (P = 9.5 × 10(-7)), indicating epigenetic silencing. In addition, a predicted methylation class mainly represented by the clear-cell cases (20 clear cell out of 23 cases) had improved survival time. Although these analyses included only 30 clear-cell carcinomas, results suggest that loss of expression of KCNH2 (HERG) by methylation could be a good prognostic marker, given that overexpression of the potassium (K(+)) channel Eag family members promotes increased proliferation and results in poor prognosis. Validation in a bigger cohort of clear-cell tumors of the ovary is warranted.

The DNA methylomes of serous borderline tumors reveal subgroups with malignant- or benign-like profiles

Serous borderline tumors (SBOTs) are a challenging group of ovarian tumors positioned between benign and malignant disease. We have profiled the DNA methylomes of 12 low-grade serous carcinomas (LGSCs), 19 SBOTs, and 16 benign serous tumors (BSTs) across 27,578 CpG sites to further characterize the epigenomic relationship between these subtypes of ovarian tumors. Unsupervised hierarchical clustering of DNA methylation levels showed that LGSCs differ distinctly from BSTs, but not from SBOTs. Gene ontology analysis of genes showing differential methylation at linked CpG sites between LGSCs and BSTs revealed significant enrichment of gene groups associated with cell adhesion, cell-cell signaling, and the extracellular region, consistent with a more invasive phenotype of LGSCs compared with BSTs. Consensus clustering highlighted differences between SBOT methylomes and returned subgroups with malignant- or benign-like methylation profiles. Furthermore, a two-loci DNA methylation signature can distinguish between these SBOT subgroups with benign- and malignant-like methylation characteristics. Our findings indicate striking similarities between SBOT and LGSC methylomes, supporting a common origin and the view that LGSC may arise from SBOT. A subgroup of SBOTs can be classified into tumors with a benign- or a malignant-like methylation profile that may help in identifying tumors more likely to progress into LGSCs.

Integrative prediction of gene function and platinum-free survival from genomic and epigenetic features in ovarian cancer

The identification of genetic and epigenetic alterations from primary tumor cells has become a common method to discover genes critical to the development, progression, and therapeutic resistance of cancer. We seek to identify those genetic and epigenetic aberrations that have the most impact on gene function within the tumor. First, we perform a bioinformatics analysis of copy number variation (CNV) and DNA methylation covering the genetic landscape of ovarian cancer tumor cells. We were specifically interested in copy number variation as our base genomic property in the prediction of tumor suppressors and oncogenes in the altered ovarian tumor. We identify changes in DNA methylation and expression specifically for all amplified and deleted genes. We statistically define tumor suppressor and oncogenic gene function from integrative analysis of three modalities: copy number variation, DNA methylation, and gene expression. Our method (1) calculates the extent of genomic and epigenetic alterations of defined tumor suppressor and oncogenic features for the functional prediction of significant ovarian cancer gene candidates and (2) identifies the functional activity or inactivity of known tumor suppressors and oncogenes in ovarian cancer. We applied our protocol on 42 primary serous ovarian cancer samples using MOMA-ROMA representational array assays. Additionally, we provide the basis for incorporating epigenetic profiles of ovarian tumors for the purposes of platinum-free survival prediction in the context of TCGA data.

The duplicitous origin of ovarian cancer

The past few decades have seen many advances in the treatment of a variety of cancers. Unfortunately, for ovarian cancer, which is the most lethal type of gynecologic malignancy, no new therapeutic approach has been successfully introduced since the 1990s. Ovarian cancer is usually detected in later stages, when remission rates are high and tumors are resistant to chemotherapy. Little is known about the primary lesion in ovarian cancer. Recently, it has been shown that the origin of ovarian cancer can be cells from adjacent tissue or cells from other primary tumors, which make their way to the ovaries due to the unique nature of their microenvironment during ovulation. The tumor in ovarian cancer is heterogeneous and hierarchically organized. In this review, we discuss the role of ovarian cancer stem cells in the process of tumor formation and recurrence. We propose the need to shift the paradigm away from the classification of ovarian cancer as a single disease with a single cellular origin. Understanding the complexity of the disease will facilitate devising new methods for fighting this cancer and improving the life of many women inflicted with the disease.

The mitogen-activated protein kinase phosphatase-1 (MKP-1) gene is a potential methylation biomarker for malignancy of breast cancer

The mitogen-activated protein kinase (MAPK) phosphatase- 1 (MKP-1) belongs to the MAPK cascades which are central to cell proliferation and apoptosis. The carcinogenic role of MKP-1 has been reported in many types of cancer but it has rarely been investigated in breast cancer. The present study was designed to evaluate the MKP-1 mRNA expression and its possible regulation by methylation of MKP-1 promoter in the model of several breast cancer cell lines and tissues as well as controls. Our data demonstrate MKP-1 mRNA expression significantly decreased in five breast cancer cell lines compared to breast controls (P<0.01). Using the methylation-specific PCR (MSP) analysis, the unmethylated reaction (U) is dominant in both normal cell lines and benign breast tumors (100% vs. 86.2%), whereas the methylated reaction (M) is dominant in both breast cancer cell lines and invasive breast tumors (100% vs. 57.2%). In terms of methylation ratio (M/M+U), methylation level in MKP-1 promoter is significantly higher in the invasive breast tumor tissues (n = 152) than in benign breast tumor tissues (n = 29) (P<0.0001). Assessing the methylation ratio of the promoter of MKP-1 gene to diagnose the breast malignancy (invasive vs. benign), the area under the receiver- operating characteristic (ROC) curve was 0.809 (95% CI: 0.711-0.906, P<0.001). The best performance for this prediction has a sensitivity of 76.32% and a specificity of 82.76% at the cutoff value of 0.38. Taken together, we firstly demonstrated that the promoter methylation of MKP-1 gene is a potential breast cancer biomarker for breast malignancy.

Genome-wide methylation profiling identifies hypermethylated biomarkers in high-grade cervical intraepithelial neoplasia

Epigenetic modifications, such as aberrant DNA promoter methylation, are frequently observed in cervical cancer. Identification of hypermethylated regions allowing discrimination between normal cervical epithelium and high-grade cervical intraepithelial neoplasia (CIN2/3), or worse, may improve current cervical cancer population-based screening programs. In this study, the DNA methylome of high-grade CIN lesions was studied using genome-wide DNA methylation screening to identify potential biomarkers for early diagnosis of cervical neoplasia. Methylated DNA Immunoprecipitation (MeDIP) combined with DNA microarray was used to compare DNA methylation profiles of epithelial cells derived from high-grade CIN lesions with normal cervical epithelium. Hypermethylated differentially methylated regions (DMRs) were identified. Validation of nine selected DMRs using BSP and MSP in cervical tissue revealed methylation in 63.2-94.7% high-grade CIN and in 59.3-100% cervical carcinomas. QMSP for the two most significant high-grade CIN-specific methylation markers was conducted exploring test performance in a large series of cervical scrapings. Frequency and relative level of methylation were significantly different between normal and cancer samples. Clinical validation of both markers in cervical scrapings from patients with an abnormal cervical smear confirmed that frequency and relative level of methylation were related with increasing severity of the underlying CIN lesion and that ROC analysis was discriminative. These markers represent the COL25A1 and KATNAL2 and their observed increased methylation upon progression could intimate the regulatory role in carcinogenesis. In conclusion, our newly identified hypermethylated DMRs represent specific DNA methylation patterns in high-grade CIN lesions and are candidate biomarkers for early detection.

Targeting the epigenome in ovarian cancer

Epithelial ovarian cancer is the leading cause of death from gynecological cancers, largely owing to the development of recurrent intractable disease. Only a small number of distinct genetic mutations are known to contribute to ovarian carcinogenesis. Furthermore, understanding mechanistic genotype-phenotype links is complicated by frequent aneuploidy. Epigenetic deregulation is even more prominent, and ovarian cancers are replete with such aberrations that repress tumor suppressors and activate proto-oncogenes. Epigenetic therapies are emerging as promising agents for resensitizing platinum-resistant ovarian cancers. These drugs may also have the potential to alter epigenetic programming in cancer progenitor cells and provide a strategy for improving therapy of ovarian cancer.

Differential analysis of ovarian and endometrial cancers identifies a methylator phenotype

Despite improved outcomes in the past 30 years, less than half of all women diagnosed with epithelial ovarian cancer live five years beyond their diagnosis. Although typically treated as a single disease, epithelial ovarian cancer includes several distinct histological subtypes, such as papillary serous and endometrioid carcinomas. To address whether the morphological differences seen in these carcinomas represent distinct characteristics at the molecular level we analyzed DNA methylation patterns in 11 papillary serous tumors, 9 endometrioid ovarian tumors, 4 normal fallopian tube samples and 6 normal endometrial tissues, plus 8 normal fallopian tube and 4 serous samples from TCGA. For comparison within the endometrioid subtype we added 6 primary uterine endometrioid tumors and 5 endometrioid metastases from uterus to ovary. Data was obtained from 27,578 CpG dinucleotides occurring in or near promoter regions of 14,495 genes. We identified 36 locations with significant increases or decreases in methylation in comparisons of serous tumors and normal fallopian tube samples. Moreover, unsupervised clustering techniques applied to all samples showed three major profiles comprising mostly normal samples, serous tumors, and endometrioid tumors including ovarian, uterine and metastatic origins. The clustering analysis identified 60 differentially methylated sites between the serous group and the normal group. An unrelated set of 25 serous tumors validated the reproducibility of the methylation patterns. In contrast, >1,000 genes were differentially methylated between endometrioid tumors and normal samples. This finding is consistent with a generalized regulatory disruption caused by a methylator phenotype. Through DNA methylation analyses we have identified genes with known roles in ovarian carcinoma etiology, whereas pathway analyses provided biological insight to the role of novel genes. Our finding of differences between serous and endometrioid ovarian tumors indicates that intervention strategies could be developed to specifically address subtypes of epithelial ovarian cancer.

Constitutive proteasomal degradation of TWIST-1 in epithelial-ovarian cancer stem cells impacts differentiation and metastatic potential

Epithelial-mesenchymal transition (EMT) is a critical process for embryogenesis but is abnormally activated during cancer metastasis and recurrence. This process enables epithelial cancer cells to acquire mobility and traits associated with stemness. It is unknown whether epithelial stem cells or epithelial cancer stem cells are able to undergo EMT, and what molecular mechanism regulates this process in these specific cell types. We found that Epithelial Ovarian Cancer Stem cells (EOC stem cells) are the source of metastatic progenitor cells through a differentiation process involving EMT and Mesenchymal-Epithelial Transition (MET). We demonstrate both in vivo and in vitro the differentiation of EOC stem cells into mesenchymal spheroid-forming cells (MSFCs) and their capacity to initiate an active carcinomatosis. Furthermore, we demonstrate that human EOC stem cells injected i.p in mice are able to form ovarian tumors, suggesting that the EOC stem cells have the ability to “home” to the ovaries and establish tumors. Most interestingly, we found that TWIST1 is constitutively degraded in EOC stem cells, and that the acquisition of TWIST1 requires additional signals that will trigger the differentiation process. These findings are relevant for understanding the differentiation and metastasis process in EOC stem cells.

The new face of ovarian cancer modeling: better prospects for detection and treatment

Ovarian cancer has a disproportionately high mortality rate because patients typically present with late-stage metastatic disease. The vast majority of these deaths are from high-grade serous carcinoma. Recent studies indicate that many of these tumors arise from the fallopian tube and subsequently metastasize to the ovary. This may explain why such tumors have not been detected at early stage as detection efforts have been focused purely on the ovary. In keeping with this leap in understanding other advances such as the development of ex-vivo models and immortalization of human fallopian tube epithelial cells, and the use of integrated genomic analyses to identify hundreds of novel candidate oncogenes and tumor suppressors potentially involved in tumorigenesis now engender hope that we can begin to truly define the differences in pathogenesis between fallopian tube and ovarian-derived tumors. In doing so, we can hopefully improve early detection, treatment, and outcome.

DNA Damage Response is Prominent in Ovarian High-Grade Serous Carcinomas, Especially Those with Rsf-1 (HBXAP) Overexpression

DNA damage commonly occurs in cancer cells as a result of endogenous and tumor microenvironmental stress. In this study, we applied immunohistochemistry to study the expression of phosphorylated Chk2 (pChk2), a surrogate marker of the DNA damage response, in high grade and low grade of ovarian serous carcinoma. A phospho-specific antibody specific for threonine 68 of Chk2 was used for immunohistochemistry on a total of 292 ovarian carcinoma tissues including 250 high-grade and 42 low-grade serous carcinomas. Immunostaining intensity was correlated with clinicopathological features. We found that there was a significant correlation between pChk2 immunostaining intensity and percentage of pChk2 positive cells in tumors and demonstrated that high-grade serous carcinomas expressed an elevated level of pChk2 as compared to low-grade serous carcinomas. Normal ovarian, fallopian tube, ovarian cyst, and serous borderline tumors did not show detectable pChk2 immunoreactivity. There was no significant difference in pChk2 immunoreactivity between primary and recurrent high-grade serous carcinomas. In high-grade serous carcinomas, a significant correlation (P < 0.0001) in expression level (both in intensity and percentage) was found between pChk2 and Rsf-1 (HBXAP), a gene involved in chromatin remodeling that is amplified in high-grade serous carcinoma. Our results suggest that the DNA damage response is common in high-grade ovarian serous carcinomas, especially those with Rsf-1 overexpression, suggesting that Rsf-1 may be associated with DNA damage response in high-grade serous carcinomas.

Molecular pathogenesis and extraovarian origin of epithelial ovarian cancer--shifting the paradigm

Recent morphologic, immunohistochemical, and molecular genetic studies have led to the development of a new paradigm for the pathogenesis and origin of epithelial ovarian cancer based on a dualistic model of carcinogenesis that divides epithelial ovarian cancer into 2 broad categories designated types I and II. Type I tumors comprise low-grade serous, low-grade endometrioid, clear cell and mucinous carcinomas, and Brenner tumors. They are generally indolent, present in stage I (tumor confined to the ovary), and are characterized by specific mutations, including KRAS, BRAF, ERBB2, CTNNB1, PTEN, PIK3CA, ARID1A, and PPP2R1A, which target specific cell signaling pathways. Type I tumors rarely harbor TP53 mutations and are relatively stable genetically. Type II tumors comprise high-grade serous, high-grade endometrioid, malignant mixed mesodermal tumors (carcinosarcomas), and undifferentiated carcinomas. They are aggressive, present in advanced stage, and have a very high frequency of TP53 mutations but rarely harbor the mutations detected in type I tumors. In addition, type II tumors have molecular alterations that perturb expression of BRCA either by mutation of the gene or by promoter methylation. A hallmark of these tumors is that they are genetically highly unstable. Recent studies strongly suggest that fallopian tube epithelium (benign or malignant) that implants on the ovary is the source of low-grade and high-grade serous carcinoma rather than the ovarian surface epithelium as previously believed. Similarly, it is widely accepted that endometriosis is the precursor of endometrioid and clear cell carcinomas and, as endometriosis, is thought to develop from retrograde menstruation; these tumors can also be regarded as involving the ovary secondarily. The origin of mucinous and transitional cell (Brenner) tumors is still not well established, although recent data suggest a possible origin from transitional epithelial nests located in paraovarian locations at the tuboperitoneal junction. Thus, it now appears that type I and type II ovarian tumors develop independently along different molecular pathways and that both types develop outside the ovary and involve it secondarily. If this concept is confirmed, it leads to the conclusion that the only true primary ovarian neoplasms are gonadal stromal and germ cell tumors analogous to testicular tumors. This new paradigm of ovarian carcinogenesis has important clinical implications. By shifting the early events of ovarian carcinogenesis to the fallopian tube and endometrium instead of the ovary, prevention approaches, for example, salpingectomy with ovarian conservation, may play an important role in reducing the burden of ovarian cancer while preserving hormonal function and fertility.

The insulin-like growth factor 1 pathway is a potential therapeutic target for low-grade serous ovarian carcinoma

OBJECTIVE

To validate the overexpression of insulin-like growth factor 1 (IGF-1) and its receptor (IGF-1R) in low-grade serous ovarian carcinoma (SOC), and to investigate whether the IGF-1 pathway is a potential therapeutic target for low-grade SOC.

METHODS

Gene expression profiling was performed on serous borderline ovarian tumors (SBOTs) and low-grade SOC, and overexpression of IGF-1 in low-grade SOC was validated by RT-PCR and immunohistochemistry. The effect of exogenous IGF-1 on cell proliferation was determined in cell lines by cell proliferation assays, cell migration assays, and Western blot. Signaling pathways downstream of IGF-1 and the effects of the AKT inhibitor MK-2206 were investigated by Western blot analysis and by generating IGF-1R short hairpin RNA stable knockdown cell lines. Low- and high-grade cell lines were treated with the dual IGF-1R- and insulin receptor-directed tyrosine kinase inhibitor OSI-906, and cellular proliferation was measured.

RESULTS

mRNA analysis and immunostaining revealed significantly higher IGF-1 expression in low-grade SOCs than in SBOTs or high-grade SOCs. In response to exogenous treatment with IGF-1, low-grade cell lines exhibited more intense upregulation of phosphorylated AKT than did high-grade cell lines, an effect that was diminished with IGF-1R knockdown and MK-2206 treatment. Low-grade SOC cell lines were more sensitive to growth inhibition with OSI-906 than were high-grade cell lines.

CONCLUSIONS

IGF-1 is overexpressed in low-grade SOCs compared with SBOTs and high-grade SOCs. Additionally, low-grade SOC cell lines were more responsive to IGF-1 stimulation and IGF-1R inhibition than were high-grade lines. The IGF-1 pathway is therefore a potential therapeutic target in low-grade SOC.