Histologic Type, Organ of Origin, and Wnt Pathway Status: Effect on Gene Expression in Ovarian and Uterine Carcinomas

A Novel Set of WNT Pathway Effectors as a Predictive Marker of Uterine Corpus Endometrial Carcinoma-Study Based on Weighted Co-expression Matrices

Uterine corpus endometrial carcinomas (UCEC) are clinically divided into two subgroups-endometrioid endometrial carcinoma (EEC) or non-endometrioid endometrial carcinoma (NEEC). The first group shows relatively better prognosis. However, the discrimination seems to be insufficient due to the fact that in the mildest EEC are patients with poor treatment response and bad prognosis. Our aim was to examine the molecular background of such phenomenon and whether gene expression patterns might be of importance for the clinic. We focused our analysis on WNT pathway target genes since it is one of the main regulators of endometrial proliferation and differentiation. In silico analysis of TCGA data, including Weighted Co-expression Network Analysis, Principle Component Analysis, and Multiple Factor Analysis, allows to select 28 genes that serve as a predictive markers for UCEC patients. Our study revealed that there is a subgroup of the endometrioid cases that molecularly resembles mixed/serous groups. This may explain the reason for existence of subgroup of patients, that although clinically diagnosed with the mildest endometrioid UCEC type, yet present failure in treatment and aggressive course of the disease. Our study suggests that worse outcome in these patients may be based on a disruption of proper WNT signalling pathway resulting in deregulation of its effector genes. Moreover, we showed that mixed group consisting of tumours containing both endometrioid and serous types of cells, has serous expression profile of WNT targets. The proposed gene set allows to predict progression of the disease trough dividing patients into groups of low or high grade with 70.8% sensitivity and 88.6% specificity (AUC = 0.837) as well as could predict patient prognosis associated with UCEC subtype with 70.1% sensitivity and 86.2% specificity (AUC = 0.855). Relatively small number of implicated genes makes it highly applicable and possibly clinically simple and useful tool.

Meta-analysis of gene expression studies in endometrial cancer identifies gene expression profiles associated with aggressive disease and patient outcome

Although endometrioid endometrial cancer (EEC; comprising ~80% of all endometrial cancers diagnosed) is typically associated with favourable patient outcome, a significant portion (~20%) of women with this subtype will relapse. We hypothesised that gene expression predictors of the more aggressive non-endometrioid endometrial cancers (NEEC) could be used to predict EEC patients with poor prognosis. To explore this hypothesis, we performed meta-analysis of 12 gene expression microarray studies followed by validation using RNA-Seq data from The Cancer Genome Atlas (TCGA) and identified 1,253 genes differentially expressed between EEC and NEEC. Analysis found 121 genes were associated with poor outcome among EEC patients. Forward selection likelihood-based modelling identified a 9-gene signature associated with EEC outcome in our discovery RNA-Seq dataset which remained significant after adjustment for clinical covariates, but was not significant in a smaller RNA-Seq dataset. Our study demonstrates the value of employing meta-analysis to improve the power of gene expression microarray data, and highlight genes and molecular pathways of importance for endometrial cancer therapy.

Elevated glucose levels impair the WNT/β-catenin pathway via the activation of the hexosamine biosynthesis pathway in endometrial cancer

Endometrial cancer (EC) is one of the most common gynecological malignancies in the world. Associations between fasting glucose levels (greater than 5.6mmol/L) and the risk of cancer fatality have been reported. However, the underlying link between glucose metabolic disease and EC remains unclear. In the present study, we explored the influence of elevated glucose levels on the WNT/β-catenin pathway in EC. Previous studies have suggested that elevated concentrations of glucose can drive the hexosamine biosynthesis pathway (HBP) flux, thereby enhancing the O-GlcNAc modification of proteins. Here, we cultured EC cell lines, AN3CA and HEC-1-B, with various concentrations of glucose. Results showed that when treated with high levels of glucose, both lines showed increased expression of β-catenin and O-GlcNAcylation levels; however, these effects could be abolished by the HBP inhibitors, Azaserine and 6-Diazo-5-oxo-l-norleucine, and be restored by glucosamine. Moreover the AN3CA and HEC-1-B cells that were cultured with or without PUGNAc, an inhibitor of the O-GlcNAcase, showed that PUGNAc increased β-catenin levels. The results suggest that elevated glucose levels increase β-catenin expression via the activation of the HBP in EC cells. Subcellular fractionation experiments showed that AN3CA cells had a higher expression of intranuclear β-catenin in high glucose medium. Furthermore, TOP/FOP-Flash and RT-PCR results showed that glucose-induced increased expression of β-catenin triggered the transcription of target genes. In conclusion, elevated glucose levels, via HBP, increase the O-GlcNAcylation level, thereby inducing the over expression of β-catenin and subsequent transcription of the target genes in EC cells.

Ovarian cancer: genomic analysis

OBJECTIVES

Despite improvements in the management of ovarian cancer patients over the last 30 years, there has been only a minimal improvement in overall survival. While targeted therapeutic approaches for the treatment of cancer have evolved, major challenges in ovarian cancer research persist, including the identification of predictive biomarkers with clinical relevance, so that empirical drug selection can be avoided. In this article, we review published genomic analysis studies including data generated in our laboratory and how they have been incorporated into modern clinical trials in a rational and effective way.

METHODS

Multiple published genomic analysis studies were collected for review and discussion with emphasis on their potential clinical applicability.

RESULTS

Genomic analysis has been shown to be a powerful tool to identify dysregulated genes, aberrantly activated pathways and to uncover uniqueness of subclasses of ovarian tumors. The application of this technology has provided a solid molecular basis for different clinical behaviors associated with tumor histology and grade. Genomic signatures have been obtained to predict clinical end points for patients with cancer, including response rates, progression-free survival, and overall survival. In addition, genomic analysis has provided opportunities to identify biomarkers, which either result in a modification of existing clinical management or to stratification of patients to novel therapeutic approaches designed as clinical trials.

CONCLUSIONS

Genomic analyses have accelerated the identification of relevant biomarkers and extended our understanding of the molecular biology of ovarian cancer. This in turn, will hopefully lead to a paradigm shift from empirical, uniform treatment to a more rational, personalized treatment of ovarian cancers. However, validation of potential biomarkers on both the statistical and biological levels is needed to confirm they are of clinical relevance, in order to increase the likelihood that the desired outcome can be predicted and achieved.

Micro-RNAs and ovarian cancer: the state of art and perspectives of clinical research

Dysregulation of microRNA (mi-RNA) expression plays a major role in the development and progression of most human malignancies. Members of the miR-200 family, miR-182, miR-214 and miR-221 are frequently up-regulated, whereas miR-100, let-7i, miR-199a, miR-125b, mir-145 and miR-335 are often down-regulated in ovarian cancer compared with normal ovarian tissue. Most mi-RNA signatures are overlapping in different tumor histotypes but some mi-RNAs seem to be histotype specific. For instance, the endometrioid type shares with the serous and clear cell types the up-regulation of miR-200 family members, but also presents over-expression of miR-21, miR-202 and miR-205. Clear cell carcinoma has a significantly higher expression of miR-30a and miR-30a*, whereas mucinous histotype has elevated levels of miR-192/194. In vitro and in vivo investigations have shown that several mi-RNAs can modulate the sensitivity of ovarian cancer to platinum and taxane, and clinical studies have suggested that mi-RNA profiling may predict the outcome of patients with this malignancy. Some mi-RNAs could be used as biomarkers to identify patients that might benefit from the addition of molecularly targeted agents (i.e. anti-angiogenic agents, MET inhibitors and poly(ADP-ribose) polymerase (PARP) inhibitors) to standard chemotherapy. Moreover, mi-RNAs could represent potential targets for the development of novel therapies.

Gene expression analysis in ovarian cancer - faults and hints from DNA microarray study

The introduction of microarray techniques to cancer research brought great expectations for finding biomarkers that would improve patients’ treatment; however, the results of such studies are poorly reproducible and critical analyses of these methods are rare. In this study, we examined global gene expression in 97 ovarian cancer samples. Also, validation of results by quantitative RT-PCR was performed on 30 additional ovarian cancer samples. We carried out a number of systematic analyses in relation to several defined clinicopathological features. The main goal of our study was to delineate the molecular background of ovarian cancer chemoresistance and find biomarkers suitable for prediction of patients’ prognosis. We found that histological tumor type was the major source of variability in genes expression, except for serous and undifferentiated tumors that showed nearly identical profiles. Analysis of clinical endpoints [tumor response to chemotherapy, overall survival, disease-free survival (DFS)] brought results that were not confirmed by validation either on the same group or on the independent group of patients. CLASP1 was the only gene that was found to be important for DFS in the independent group, whereas in the preceding experiments it showed associations with other clinical endpoints and with BRCA1 gene mutation; thus, it may be worthy of further testing. Our results confirm that histological tumor type may be a strong confounding factor and we conclude that gene expression studies of ovarian carcinomas should be performed on histologically homogeneous groups. Among the reasons of poor reproducibility of statistical results may be the fact that despite relatively large patients’ group, in some analyses one has to compare small and unequal classes of samples. In addition, arbitrarily performed division of samples into classes compared may not always reflect their true biological diversity. And finally, we think that clinical endpoints of the tumor probably depend on subtle changes in many and, possibly, alternative molecular pathways, and such changes may be difficult to demonstrate.

Ovarian and endometrial endometrioid carcinomas have distinct CTNNB1 and PTEN mutation profiles

Ovarian endometrioid carcinomas and endometrial endometrioid carcinomas share many histological and molecular alterations. These similarities are likely due to a common endometrial epithelial precursor cell of origin, with most ovarian endometrioid carcinomas arising from endometriosis. To directly compare the mutation profiles of two morphologically similar tumor types, endometrial endometrioid carcinomas (n=307) and ovarian endometrioid carcinomas (n=33), we performed select exon capture sequencing on a panel of genes: ARID1A, PTEN, PIK3CA, KRAS, CTNNB1, PPP2R1A, TP53. We found that PTEN mutations are more frequent in low-grade endometrial endometrioid carcinomas (67%) compared with low-grade ovarian endometrioid carcinomas (17%) (P<0.0001). By contrast, CTNNB1 mutations are significantly different in low-grade ovarian endometrioid carcinomas (53%) compared with low-grade endometrial endometrioid carcinomas (28%) (P<0.0057). This difference in CTNNB1 mutation frequency may be reflective of the distinct microenvironments; the epithelial cells lining an endometriotic cyst within the ovary are exposed to a highly oxidative environment that promotes tumorigenesis. Understanding the distinct mutation patterns found in the PI3K and Wnt pathways of ovarian and endometrial endometrioid carcinomas may provide future opportunities for stratifying patients for targeted therapeutics.

Down-regulation of Sox7 is associated with aberrant activation of Wnt/b-catenin signaling in endometrial cancer

Although the mortality rate of endometrial cancer is comparatively low in gynecologic malignancies, a rising trend of this cancer has been observed for the past decade. The understanding of the molecular mechanism will favor for the clinical management of this disease. Aberrant activation of Wnt/β-catenin signaling pathway plays a major role in the pathogenesis of endometrioid adenocarcinoma including this cancer type. In this study, we reported that Sox7, one of Sox transcriptional factors, was frequently underexpressed in endometrial cancer and importantly, it was associated with dysregulation of the Wnt/β-catenin signaling activity. Immunohistochemical and quantitative RT-PCR analyses showed that Sox7 was underexpressed and was associated with high-grade tumor (P=0.021), increased expressions of β-catenin (P=0.038) and its downstream targets; CyclinD1 (P<0.001) and FGF9 (P<0.001). In addition, using HEK293T cell model, we found that Sox7 was able to inhibit TCF/LEF-1-dependent luciferase activity induced by Wnt-1. This was further proved by that Sox7 could significantly suppress the expressions of Wnt targets; Cyclin D1 and C-myc in endometrial cells. Immuno-fluorescent microscopy revealed that Sox7 was co-localizaed with either mutant β-catenin or TCF4 protein in nucleus, while co-immunopreciptation assay demonstrated that Sox7 could physically interact with not only wild-type but also mutant β-catenin, as well as TCF4 proteins. Functionally, enforced expression of Sox7 could significantly inhibit endometrial or endometrioid ovarian cancer cells (OEA) harboring either wild-type or mutant β-catenin. These data suggest Sox7 is a negative regulator of Wnt/β-catenin signaling pathway through impeding the transcriptional machinery of β-catenin/TCF/LEF-1 transcriptional complex, and the loss of expression may be involved in the pathogenesis of endometrial cancer.

Tissue transglutaminase regulates β-catenin signaling through a c-Src-dependent mechanism

Tissue transglutaminase (TG2) is a multifunctional enzyme involved in protein cross-linking and cell adhesion to fibronectin (FN). In cancer, TG2 induces an epithelial to mesenchymal transition, contributing to metastasis. Because cadherins bind β-catenin at cell-cell junctions, disruption of adherens junctions destabilizes cadherin-catenin complexes. The goal of the present study was to analyze whether and how TG2 interacts with and regulates β-catenin signaling in ovarian cancer (OC) cells. We observed a significant correlation between TG2 and β-catenin expression levels in OC cells and tumors. TG2 augmented Wnt/β-catenin signaling, as evidenced by enhanced β-catenin transcriptional activity, inducing transcription of target genes cyclin D1 and c-Myc. By promoting integrin-mediated cell adhesion to FN, TG2 physically associates with and recruits c-Src, which in turn phosphorylates β-catenin at Tyr(654), releasing it from E-cadherin and rendering it available for transcriptional regulation. By interacting with FN and enhancing β-catenin signaling, complexed TG2 stimulates OC cell proliferation. In summary, our data demonstrate that TG2 regulates β-catenin expression and function in OC cells and define the c-Src-dependent mechanism through which this occurs.

Matrix rigidity activates Wnt signaling through down-regulation of Dickkopf-1 protein

Cells respond to changes in the physical properties of the extracellular matrix with altered behavior and gene expression, highlighting the important role of the microenvironment in the regulation of cell function. In the current study, culture of epithelial ovarian cancer cells on three-dimensional collagen I gels led to a dramatic down-regulation of the Wnt signaling inhibitor dickkopf-1 with a concomitant increase in nuclear β-catenin and enhanced β-catenin/Tcf/Lef transcriptional activity. Increased three-dimensional collagen gel invasion was accompanied by transcriptional up-regulation of the membrane-tethered collagenase membrane type 1 matrix metalloproteinase, and an inverse relationship between dickkopf-1 and membrane type 1 matrix metalloproteinase was observed in human epithelial ovarian cancer specimens. Similar results were obtained in other tissue-invasive cells such as vascular endothelial cells, suggesting a novel mechanism for functional coupling of matrix adhesion with Wnt signaling.

Development of targeted therapy in uterine serous carcinoma, a biologically aggressive variant of endometrial cancer

Endometrial cancer (EC) is the most common female genital malignancy in the USA. Most carcinomas arising from the uterus are estrogen dependent and are associated with obesity and hypertension. They are designated type I ECs and typically, due to their early diagnosis secondary to postmenopausal bleeding, have a good prognosis. By contrast, type II ECs develop in older patients, are not hormone dependent and are responsible for most recurrences and deaths from EC. Uterine serous cancer constitutes up to 10% of all endometrial tumors, and represents the most biologically aggressive variant of type II EC. This article will describe the most salient molecular markers that have been identified in uterine serous cancer, thus far with emphasis on the use of erbB2 (HER2/neu) as the first of a series of therapeutic markers for the treatment of this highly-aggressive subset of ECs.

Endometrial carcinoma: molecular alterations involved in tumor development and progression

In the western world, endometrial carcinoma (EC) is the most common cancer of the female genital tract. The annual incidence has been estimated at 10-20 per 100,000 women. Two clinicopathological variants are recognized: the estrogen related (type I, endometrioid) and the non-estrogen related (type II, non-endometrioid).The clinicopathological differences are paralleled by specific genetic alterations, with type I showing microsatellite instability and mutations in phosphatase and tensin homologue deleted on chromosome 10, PIK3CA, K-RAS and CTNNB1 (β-catenin), and type II exhibiting TP53 mutations and chromosomal instability. Some non-endometrioid carcinomas probably arise from pre-existing endometrioid carcinomas as a result of tumor progression and, not surprisingly, some tumors exhibit combined or mixed features at the clinical, pathological and molecular levels. In EC, apoptosis resistance may have a role in tumor progression. Understanding pathogenesis at the molecular level is essential in identifying biomarkers for successful targeted therapies. In this review, the genetic changes of endometrial carcinogenesis are discussed in the light of the morphological features of the tumors and their precursors.

Promoter methylation of sFRP5 in patients with ovarian clear cell adenocarcinoma

BACKGROUND

Specific tumour suppressor genes with promoter methylation in ovarian clear cell adenocarcinoma (OCCA) can be one important epigenetic mark distinguishing OCCA from ovarian serous adenocarcinoma (OSA), benign endometriotic cysts and normal ovarian epitheliums.

MATERIALS AND METHODS

Five OCCA cell lines, 63 cancer tissues (48 OCCA and 15 OSA), 10 benign endometriotic cysts and five normal ovarian epitheliums were analysed by methylation-specific PCR using pooled DNAs to determine the methylation status of the promoter of the target genes, including genes for secreted frizzled-related proteins (sFRP1 to 5), adenomatous polyposis coli (APC), retinoblastoma protein 1 (Rb1), breast cancer 1 gene (BRCA1), p14(ARF), p15(INK4b), p16(INK4a) and survivin. Methylation frequencies of identified targets were further analysed with individual DNA samples.

RESULTS

The sFRP5 promoter was significantly methylated in all OCCA cell lines, with 64.6% in OCCA tissues compared with 13.3% in OSA, and 0% in benign endometriotic cysts and normal ovarian epitheliums (P < 0.0001). With a median follow-up of 44 months, the expected 5-year overall survival (OS) for patients with methylated sFRP5 promoter were significantly worse than for those with unmethylated sFRP5 (52% vs. 88%, P = 0.03). After adjusting for age, stage, and residual disease after primary surgery, patients with unmethylated sFRP5 promoter had an independent good prognostic factor in OS (P = 0.017).

CONCLUSION

The high percentage of promoter methylation in the sFRP5 gene in OCCA indicates its importance in the development of OCCA and is a potential useful marker for prognoses and target for treatment of OCCA.

EGF-receptor regulation of matrix metalloproteinases in epithelial ovarian carcinoma

Ovarian carcinoma is most frequently detected when disease has already disseminated intra-abdominally, resulting in a 5-year survival rate of less than 20% owing to complications of metastasis. Peritoneal ascites is often present, establishing a unique microenvironmental niche comprised of tumor and inflammatory cells, along with a wide range of bioactive soluble factors, several of which stimulate the EGF-receptor (EGFR). Elevated EGFR is associated with less favorable disease outcome in ovarian cancer, related in part to EGFR activation of signaling cascades that lead to enhanced matrix metalloproteinase expression and/or function. The available data suggest that modulating the expression or activity of the EGFR and/or matrix metalloproteinases offers opportunity for targeted intervention in patients with metastatic disease.

Biomarker discovery in ovarian cancer

Ovarian cancer is a leading cause of gynecologic cancer death among women. Tumors diagnosed early (in stage I) have a cure rate approaching 90%. However, because specific symptoms and screening tools are lacking, most ovarian cancers are very advanced when finally diagnosed. CA125 expression and pelvic ultrasonography are of limited efficacy in screening, and the search for new, complementary ovarian cancer biomarkers continues. New technology and research techniques have allowed the identification of over 100 possible tumor markers, many of which are still being evaluated for clinical relevance and several of which have entered clinical trials. Here, we review the methods of biomarker discovery, address the significance and functions of newly identified ovarian cancer tumor markers, and provide further insight into the future of ovarian cancer biomarkers.

Oviduct-specific glycoprotein is a molecular marker for invasion in endometrial tumorigenesis identified using a relevant mouse model

The light microscopic distinction between complex atypical hyperplasia (CAH) and invasive endometrioid carcinoma (UEC) on endometrial sampling is problematic and often has significant clinical implications. Using mouse models of endometrial tumorigenesis based on two of the most common molecular alterations found in primary human UEC we sought to characterize the transition from CAH to carcinoma to identify clinically useful biomarkers. We used the previously described Pten(+/-); Mlh1(-/-) mouse model. DNA was isolated from microdissected lesions (CAH and carcinoma) and analyzed for LOH and mutations of Pten and additional candidate genes. To identify novel candidate genes associated with invasion, global gene expression profiles were compared from uteri with extensive CAH and carcinoma. The majority of CAHs and carcinomas, arising in this model showed biallelic inactivation of Pten mediated through LOH or intragenic mutation of the wild-type allele suggesting that complete loss of Pten is insufficient for the development of carcinoma. The global gene expression studies detected increased expression of oviduct-specific glycoprotein (OGP) in carcinoma as compared with CAHs. This finding was validated using immunohistochemical staining in a collection of primary human UECs and CAHs. Our studies identify a molecular marker for invasive endometrial cancer that may have clinical significance, and highlight the usefulness of this mouse model in not only understanding the genetic underpinnings of endometrial carcinoma, but as a tool to develop clinically relevant biomarkers.

Ovarian cancer plasticity and epigenomics in the acquisition of a stem-like phenotype

Aggressive epithelial ovarian cancer (EOC) is genetically and epigenetically distinct from normal ovarian surface epithelial cells (OSE) and early neoplasia. Co-expression of epithelial and mesenchymal markers in EOC suggests an involvement of epithelial-mesenchymal transition (EMT) in cancer initiation and progression. This phenomenon is often associated with acquisition of a stem cell-like phenotype and chemoresistance that correlate with the specific gene expression patterns accompanying transformation, revealing a plasticity of the ovarian cancer cell genome during disease progression.Differential gene expressions between normal and transformed cells reflect the varying mechanisms of regulation including genetic changes like rearrangements within the genome, as well as epigenetic changes such as global genomic hypomethylation with localized promoter CpG island hypermethylation. The similarity of gene expression between ovarian cancer cells and the stem-like ovarian cancer initiating cells (OCIC) are surprisingly also correlated with epigenetic mechanisms of gene regulation in normal stem cells. Both normal and cancer stem cells maintain genetic flexibility by co-placement of activating and/or repressive epigenetic modifications on histone H3. The co-occupancy of such opposing histone marks is believed to maintain gene flexibility and such bivalent histones have been described as being poised for transcriptional activation or epigenetic silencing. The involvement of both-microRNA (miRNA) mediated epigenetic regulation, as well as epigenetic-induced changes in miRNA expression further highlight an additional complexity in cancer stem cell epigenomics.Recent advances in array-based whole-genome/epigenome analyses will continue to further unravel the genomes and epigenomes of cancer and cancer stem cells. In order to illuminate phenotypic signatures that delineate ovarian cancer from their associated cancer stem cells, a priority must lie in the expansion of current technologies and further implementation of bioinformatics to handle the complexity of the cancer epigenome and the various networks that coordinate disease initiation and progression. Great potential lies in the translation of these findings into epigenetic-based therapies. Additionally, targeting chemo-resistant cancer stem cells may provide a much needed breakthrough in treatment of advanced ovarian cancer and chemoresistant disease.

Potential regulatory functions of microRNAs in the ovary

The interactions between ovarian germ and somatic cells and expression of several intraovarian autocrine/paracrine regulators are major contributing factors in the ovary. These intraovarian mediators regulate various ovarian cellular activities including cell growth, differentiation, and apoptosis, which are critical in follicular development. MicroRNAs (miRNAs) have emerged as key components of posttranscriptional gene expression. Recent evidence generated in mice implicates the regulatory function of miRNAs in oocyte maturation and ovarian follicular development. In the human, miRNAs may target specific gene expression in granulosa cells and participate in establishment and progression of ovarian cancer. Here, we review the currently available information on the expression and potential regulatory functions of miRNAs in the ovary under normal and pathologic conditions. Understanding the underlying mechanisms of how ovarian germ cell and somatic cell miRNAs are regulated and identifying their specific target genes and their functions may lead to the development of strategies to achieve target-specific gene regulation for the prevention and treatment of various ovarian disorders.

Genomic analysis of epithelial ovarian cancer

Ovarian cancer is a major health problem for women in the United States. Despite evidence of considerable heterogeneity, most cases of ovarian cancer are treated in a similar fashion. The molecular basis for the clinicopathologic characteristics of these tumors remains poorly defined. Whole genome expression profiling is a genomic tool, which can identify dysregulated genes and uncover unique sub-classes of tumors. The application of this technology to ovarian cancer has provided a solid molecular basis for differences in histology and grade of ovarian tumors. Differentially expressed genes identified pathways implicated in cell proliferation, invasion, motility, chromosomal instability, and gene silencing and provided new insights into the origin and potential treatment of these cancers. The added knowledge provided by global gene expression profiling should allow for a more rational treatment of ovarian cancers. These techniques are leading to a paradigm shift from empirical treatment to an individually tailored approach. This review summarizes the new genomic data on epithelial ovarian cancers of different histology and grade and the impact it will have on our understanding and treatment of this disease.

Altered eIF6 and Dicer expression is associated with clinicopathological features in ovarian serous carcinoma patients

MicroRNAs are a group of small non-coding RNAs approximately 22 nucleotides in length. Recent work has shown differential expression of mature microRNAs in human cancers. Production and function of microRNAs require coordinated processing by proteins of the microRNA machinery. Dicer and Drosha (RNase III endonucleases) are essential components of the microRNA machinery. Recently, the ribosome anti-association factor eIF6 has also been found to have a role in microRNA-mediated post-transcriptional silencing. We characterized the alterations in the expression of genes encoding proteins of microRNA machinery in ovarian serous carcinoma. Protein expression of eIF6 and Dicer was quantified in a tissue microarray of 66 ovarian serous carcinomas. Dicer, Drosha and eIF6 mRNA expression was analysed using quantitative reverse transcription-PCR on an independent set of 50 formalin-fixed, paraffin-embedded ovarian serous carcinoma samples. Expression profiles of eIF6 and Dicer were correlated with clinicopathological and patient survival data. We provide definitive evidence that eIF6 and Dicer are both upregulated in a significant proportion of ovarian serous carcinomas and are associated with specific clinicopathological features, most notably low eIF6 expression being associated with reduced disease-free survival. The status of eIF6 and proteins of the microRNA machinery may help predict toxicity and susceptibility to future interfering RNA-based therapy.

Phenotypic plasticity of neoplastic ovarian epithelium: unique cadherin profiles in tumor progression

The mesodermally derived normal ovarian surface epithelium (OSE) displays both epithelial and mesenchymal characteristics and exhibits remarkable phenotypic plasticity during post-ovulatory repair. The majority of epithelial ovarian carcinomas (EOC) are derived from the OSE and represent the most lethal of all gynecological malignancies, as most patients (approximately 70%) present at diagnosis with disseminated intra-abdominal metastasis. The predominant pattern of EOC metastasis involves pelvic dissemination rather than lymphatic or hematologic spread, distinguishing EOC from other solid tumors. Acquisition of the metastatic phenotype involves a complex series of interrelated cellular events leading to dissociation (shedding) and dispersal of malignant cells. A key event in this process is disruption of cell-cell contacts via modulation of intercellular junctional components. In contrast to most carcinomas that downregulate E-cadherin expression during tumor progression, a unique feature of primary well-differentiated ovarian cancers is a gain of epithelial features, characterized by an increase in expression of E-cadherin. Subsequent reacquisition of mesenchymal features is observed in more advanced tumors with concomitant loss of E-cadherin expression and/or function during progression to metastasis. The functional consequences of this remarkable phenotypic plasticity are not fully understood, but may play a role in modulation of cell survival in suspension (ascites), chemoresistance, and intraperitoneal anchoring of metastatic lesions.

MicroRNA signatures in human ovarian cancer

Epithelial ovarian cancer (EOC) is the sixth most common cancer in women worldwide and, despite advances in detection and therapies, it still represents the most lethal gynecologic malignancy in the industrialized countries. Unfortunately, still relatively little is known about the molecular events that lead to the development of this highly aggressive disease. The relatively recent discovery of microRNAs (miRNA), a class of small noncoding RNAs targeting multiple mRNAs and triggering translation repression and/or RNA degradation, has revealed the existence of a new level of gene expression regulation. Multiple studies involving various types of human cancers proved that miRNAs have a causal role in tumorigenesis. Here we show that, in comparison to normal ovary, miRNAs are aberrantly expressed in human ovarian cancer. The overall miRNA expression could clearly separate normal versus cancer tissues. The most significantly overexpressed miRNAs were miR-200a, miR-141, miR-200c, and miR-200b, whereas miR-199a, miR-140, miR-145, and miR-125b1 were among the most down-modulated miRNAs. We could also identify miRNAs whose expression was correlated with specific ovarian cancer biopathologic features, such as histotype, lymphovascular and organ invasion, and involvement of ovarian surface. Moreover, the levels of miR-21, miR-203, and miR-205, up-modulated in ovarian carcinomas compared with normal tissues, were significantly increased after 5-aza-2'-deoxycytidine demethylating treatment of OVCAR3 cells, suggesting that the DNA hypomethylation could be the mechanism responsible for their overexpression. Our results indicate that miRNAs might play a role in the pathogenesis of human EOC and identify altered miRNA gene methylation as a possible epigenetic mechanism involved in their aberrant expression.

Molecular genetic changes in epithelial, stromal and mixed neoplasms of the endometrium

Endometrial carcinoma, endometrial stromal tumours and mixed malignant mesodermal tumours (MMMT) develop along distinctive molecular genetic pathways. Two distinctive types of endometrial carcinoma are distinguished, type I and type II, which develop along distinctive pathways and show different clinical behaviour and histological features. Type I carcinomas show endometrioid histology, are oestrogen-related and develop from atypical endometrial hyperplasia. The molecular tumorigenesis is comparable to colorectal carcinoma with a step-like progression and an accumulation of genetic alterations. Alterations of PTEN, K-Ras mutations and microsatellite instability are frequent and early events in type I carcinoma, whereas p53 mutations occur during progression to grade 3 carcinoma. Serous and clear cell carcinomas are considered type II carcinomas which are mostly unrelated to oestrogen. p53 mutations occur in almost all serous carcinomas and seem to occur early, leading to massive chromosomal instability and rapid tumour progression. Gene expression profiling has supported this dualistic model of endometrial carcinoma. There is evidence of molecular differences between serous and clear cell carcinomas as well as between endometrioid carcinomas with and without microsatellite instability. A dualistic model of tumorigenesis may be also suggested for endometrial stromal tumours. Endometrial stromal sarcomas (ESS; type I endometrial sarcoma) are oestrogen-related and seem to develop from endometrial stromal nodules (ESN). They are histologically and genetically distinct from undifferentiated endometrial sarcoma (UES) which seem to be mostly unrelated to oestrogen (type II endometrial sarcoma). ESS and ESN share the fusion gene JAZF1/JJAZ1 caused by a t(7;17)(p15;q21) translocation, whereas UES lacks a distinctive molecular alteration so far. In MMMT, which is considered a metaplastic carcinoma, p53 alteration occurs early, before clonal expansion and acquisition of genetic diversity during progression.

Biomarker discovery in epithelial ovarian cancer by genomic approaches

Ovarian cancer is the fifth most common form of cancer in women in the United States. It is a complex disease composed of different histological grades and histological types. Most of epithelial ovarian cancer cases are detected at an advanced stage. Patients usually respond to primary treatment with surgery and chemotherapy. However, the disease usually recurs and is ultimately fatal. So far, a satisfactory screening procedure and regime to treat the recurrence disease are not available. High-throughput genomic analyses have the potential to change the detection and the treatment of ovarian neoplasms. They can help diagnose subtypes of disease and predict patient survival. New diagnostic and prognostic markers for ovarian cancer are emerging. One day, profiling may influence treatment decisions, informing both which patients should receive chemotherapy and what type of chemotherapeutic agents should be employed. As greater numbers of tumor samples are analyzed, the power of these profiling studies will increase, raising the possibility that novel molecular targets and less toxic therapies will be identified. These powerful techniques hold the potential to unravel the genetic origins of ovarian cancer. Hopefully, this will translate into earlier diagnosis and better patient outcome from disease.

The management of serous papillary uterine cancer

PURPOSE OF REVIEW

Uterine papillary serous cancer is an extremely aggressive cancer, the optimum management of which is still being determined. It is important to understand advances that have been made in 2005 regarding the molecular biology, diagnosis, and management of this deadly disease.

RECENT FINDINGS

The main themes in the literature regarding uterine papillary serous cancer are that a potential precursor lesion, serous endometrial intraepithelial carcinoma, has been recognized as an early form of the disease. A variety of molecular biologically important markers have now been identified, including p53, HER2/neu, IL-6, kallikrein 6, and claudin-4, some of which may be susceptible to molecularly targeted therapy. Systematic surgical staging is necessary before additional therapy is recommended. Stage I uterine papillary serous cancer requires aggressive treatment, including surgery, chemotherapy, and radiation therapy for successful treatment. The most effective management of advanced stage disease remains to be resolved.

SUMMARY

Serous endometrial intraepithelial carcinoma should be treated as a form of uterine papillary serous cancer. Multimodality therapy is required for the successful management of early stage uterine papillary serous cancer. Advanced disease is often unresponsive to conventional therapy. Molecularly targeted therapies are now being introduced into the management of this disease.

Gene expression profiles of serous, endometrioid, and clear cell subtypes of ovarian and endometrial cancer

PURPOSE

The presence of similar histologic subtypes of epithelial ovarian and endometrial cancers has long been noted, although the relevance of this finding to pathogenesis and clinical management is unclear. Despite similar clinical characteristics, histologic subtypes of cancers of the ovary and endometrium are treated according to organ of origin. This study compares the gene expression profiles of analogous histologic subtypes of cancers of the ovary and endometrium using the same genomic platform to determine the similarities and differences between these tumors.

EXPERIMENTAL DESIGN

Gene expression profiles of 75 cancers (endometrioid, serous, and clear cell) of the ovary and endometrium, five renal clear cell cancers, and seven normal epithelial brushings were determined using a 11,000-element cDNA array. All images were analyzed using BRB ArrayTools. Validation was done using real-time PCR on select genes and immunohistochemical staining.

RESULTS

Comparison across endometrial and ovarian cancers and serous and endometrioid tumors showed expression patterns reflecting their organ of origin. Clear cell tumors, however, showed remarkably similar expression patterns regardless of their origin, even when compared with renal clear cell samples. A set of 43 genes was common to comparisons of each of the three histologic subtypes of ovarian cancer with normal ovarian surface epithelium.

CONCLUSIONS

The comparison of the gene expression profiles of endometrioid and serous subtypes of ovarian and endometrial cancer are largely unique to the combination of a particular subtype in a specific organ. In contrast, clear cell cancers show a remarkable similarity in gene expression profiles across organs (including kidney) and could not be statistically distinguished.