Type I to type II ovarian carcinoma progression: mutant Trp53 or Pik3ca confers a more aggressive tumor phenotype in a mouse model of ovarian cancer

Ovarian Cancer-Epidemiology, Classification, Pathogenesis, Treatment, and Estrogen Receptors' Molecular Backgrounds

Global epidemiological reports indicate a steady increase in the tendency to develop ovarian cancer. The symptoms of ovarian cancer are non-specific, and there is no effective screening tool. Most often, surgery, chemotherapy, and radiotherapy, alone or in combination, are used to treat ovarian cancer. We have a better understanding of the biology of ovarian cancer, the genetic basis of hereditary ovarian cancer, the stage of the disease, and the role of cytoreductive surgery and more effective chemotherapy, which translates into an increase in the percentage of patients who survive 5 years after diagnosis. A growing body of evidence points to the role of genetic factors in the development of cancer. It is known that mutations in the BRCA1 gene are responsible for an increased risk of developing ovarian cancer. The role of other genetic disorders, such as polymorphic variants, in increasing the risk of developing cancer is still being investigated. Ovarian cancer is a hormone-dependent cancer and its steroid hormones are estrogens. Estrogens affect cells through the estrogen receptors ERα and ERβ. An imbalance between ERα and ERβ receptor expression may, therefore, be a key step in estrogen-dependent carcinogenesis. In 60% of cancer cases, significantly elevated levels of ERα receptors are detected. The ERα receptor is encoded by the ESR1 gene, so its polymorphisms can be considered molecular markers of ovarian cancer. This article discusses the epidemiology, pathogenesis, risk factors, genetic testing, treatment, and diagnosis of ovarian cancer, as well as providing an overview of standard treatment approaches and new, targeted biologic therapies.

Diagnostic value of contrast-enhanced ultrasound in ovarian cancer: a meta-analysis

BackgroundOvarian cancer has been reported to be the eighth most common cancer among women worldwide.PurposeTo assess the diagnostic efficacy of contrast-enhanced ultrasound (CEUS) in distinguishing between benign and malignant ovarian tumors.Material and MethodsA comprehensive search of scientific literature databases, including PubMed, Cochrane Library, Web of Science, Wanfang, and CNKI, was conducted from their inception to November 2019 to identify relevant studies on the use of CEUS in the differential diagnosis of benign and malignant ovarian tumors. Sensitivity (SEN), specificity (SPE), positive and negative likelihood ratios (LR+/LR-), diagnostic odds ratios (DORs), and their corresponding 95% confidence intervals (CIs) were retrieved and analyzed using Stata 15.0.ResultsAfter rigorous screening, a total of 15 high-quality clinical studies encompassing 934 patients with ovarian cancer, comprising 969 ovarian tumors (403 malignant tumors and 566 benign tumors), were included in the analysis. Data analysis revealed significant correlations between CEUS and various diagnostic indices for ovarian tumors: the combined SEN and SPE were 0.93 (95% CI = 0.88-0.96) and 0.93 (95% CI = 0.90-0.96), respectively, and the combined LR+ and LR- were 14.07 (95% CI = 9.46-20.92) and 0.08 (95% CI = 0.05-0.13), respectively, with a combined DOR of 185.15 (95% CI = 93.31-367.41). The area under the summary receiver operating characteristic curve (AUC) was 0.98 (95% CI = 0.96-0.99). No publication bias was detected in the meta-analysis (P = 0.62).ConclusionCEUS demonstrates significant value in the diagnosis and differential diagnosis of benign and malignant ovarian tumors.

Role of Akt/Protein Kinase B in Cancer Metastasis

Metastasis is a critical step in the process of carcinogenesis and a vast majority of cancer-related mortalities result from metastatic disease that is resistant to current therapies. Cell migration and invasion are the first steps of the metastasis process, which mainly occurs by two important biological mechanisms, i.e., cytoskeletal remodelling and epithelial to mesenchymal transition (EMT). Akt (also known as protein kinase B) is a central signalling molecule of the PI3K-Akt signalling pathway. Aberrant activation of this pathway has been identified in a wide range of cancers. Several studies have revealed that Akt actively engages with the migratory process in motile cells, including metastatic cancer cells. The downstream signalling mechanism of Akt in cell migration depends upon the tumour type, sites, and intracellular localisation of activated Akt. In this review, we focus on the role of Akt in the regulation of two events that control cell migration and invasion in various cancers including head and neck squamous cell carcinoma (HNSCC) and the status of PI3K-Akt pathway inhibitors in clinical trials in metastatic cancers.

Replication stress and defective checkpoints make fallopian tube epithelial cells putative drivers of high-grade serous ovarian cancer

Clinical and molecular evidence indicates that high-grade serous ovarian cancer (HGSOC) primarily originates from the fallopian tube, not the ovarian surface. However, the reasons for this preference remain unclear. Our study highlights significant differences between fallopian tube epithelial (FTE) and ovarian surface epithelial (OSE) cells, providing the molecular basis for FTEs as site of origin of HGSOC. FTEs, unlike OSEs, exhibit heightened replication stress (RS), impaired repair of stalled forks, ineffective G2/M checkpoint, and increased tumorigenicity. BRCA1 heterozygosity exacerbates these defects, resulting in RS suppression haploinsufficiency and an aggressive tumor phenotype. Examination of human and mouse sections reveals buildup of the RS marker 53BP1 primarily in the fallopian tubes, particularly at the fimbrial ends. Furthermore, menopausal status influences RS levels. Our study provides a mechanistic rationale for FTE as the site of origin for HGSOC, investigates the impact of BRCA1 heterozygosity, and lays the groundwork for targeting early HGSOC drivers.

Establishment of a novel model of endometriosis-associated ovarian cancer by transplanting uterine tissue from Arid1a/Pten knockout mice

Although endometriosis is primarily benign, it has been identified as a risk factor for endometriosis-associated ovarian cancer (EAOC). Genetic alterations in ARID1A, PTEN, and PIK3CA have been reported in EAOC; however, an appropriate EAOC animal model has yet to be established. Therefore, the present study aimed to create an EAOC mouse model by transplanting uterine pieces from donor mice, in which Arid1a and/or Pten was conditionally knocked out (KO) in Pax8-expressing endometrial cells by the administration of doxycycline (DOX), onto the ovarian surface or peritoneum of recipient mice. Two weeks after transplantation, gene KO was induced by DOX and endometriotic lesions were thereafter removed. The induction of only Arid1a KO did not cause any histological changes in the endometriotic cysts of recipients. In contrast, the induction of only Pten KO evoked a stratified architecture and nuclear atypia in the epithelial lining of all endometriotic cysts, histologically corresponding to atypical endometriosis. The induction of Arid1a; Pten double-KO evoked papillary and cribriform structures with nuclear atypia in the lining of 42 and 50% of peritoneal and ovarian endometriotic cysts, respectively, which were histologically similar to EAOC. These results indicate that this mouse model is useful for investigating the mechanisms underlying the development of EAOC and the related microenvironment.

MicroRNA-200 family governs ovarian inclusion cyst formation and mode of ovarian cancer spread

Epidemiologic and histopathologic findings and the laying hen model support the long-standing incessant ovulation hypothesis and cortical inclusion cyst involvement in sporadic ovarian cancer development. MicroRNA-200 (miR-200) family is highly expressed in ovarian cancer. Herewith, we show that ovarian surface epithelial (OSE) cells with ectopic miR-200 expression formed stabilized cysts in three-dimensional (3D) organotypic culture with E-cadherin fragment expression and steroid hormone pathway activation, whereas ovarian cancer 3D cultures with miR-200 knockdown showed elevated TGF-β expression, mitotic spindle disorientation, increased lumenization, disruption of ROCK-mediated myosin II phosphorylation, and SRC signaling, which led to histotype-dependent loss of collective movement in tumor spread. Gene expression profiling revealed that epithelial-mesenchymal transition and hypoxia were the top enriched gene sets regulated by miR-200 in both OSE and ovarian cancer cells. The molecular changes uncovered by the in vitro studies were verified in both human and laying hen ovarian cysts and tumor specimens. As miR-200 is also essential for ovulation, our results of estrogen pathway activation in miR-200-expressing OSE cells add another intriguing link between incessant ovulation and ovarian carcinogenesis.

Validation of Novel Prognostic Biomarkers for Early-Stage Clear-Cell, Endometrioid and Mucinous Ovarian Carcinomas Using Immunohistochemistry

Early-stage (I and II) ovarian carcinoma patients generally have good prognosis. Yet, some patients die earlier than expected. Thus, it is important to stratify early-stage patients into risk groups to identify those in need of more aggressive treatment regimens. The prognostic value of 29 histotype-specific biomarkers identified using RNA sequencing was evaluated for early-stage clear-cell (CCC), endometrioid (EC) and mucinous (MC) ovarian carcinomas (n = 112) using immunohistochemistry on tissue microarrays. Biomarkers with prognostic significance were further evaluated in an external ovarian carcinoma data set using the web-based Kaplan-Meier plotter tool. Here, we provide evidence of aberrant protein expression patterns and prognostic significance of 17 novel histotype-specific prognostic biomarkers [10 for CCC (ARPC2, CCT5, GNB1, KCTD10, NUP155, RPL13A, RPL37, SETD3, SMYD2, TRIO), three for EC (CECR1, KIF26B, PIK3CA), and four for MC (CHEK1, FOXM1, KIF23, PARPBP)], suggesting biological heterogeneity within the histotypes. Combined predictive models comprising the protein expression status of the validated CCC, EC and MC biomarkers together with established clinical markers (age, stage, CA125, ploidy) improved the predictive power in comparison with models containing established clinical markers alone, further strengthening the importance of the biomarkers in ovarian carcinoma. Further, even improved predictive powers were demonstrated when combining these models with our previously identified prognostic biomarkers PITHD1 (CCC) and GPR158 (MC). Moreover, the proteins demonstrated improved risk prediction of CCC-, EC-, and MC-associated ovarian carcinoma survival. The novel histotype-specific prognostic biomarkers may not only improve prognostication and patient stratification of early-stage ovarian carcinomas, but may also guide future clinical therapy decisions.

PIK3CA gene aberrancy and role in targeted therapy of solid malignancies

Phosphoinositide kinases (PIKs) are a group of lipid kinases that are important upstream activators of various signaling pathways that drive oncogenesis. Hyperactivation of the PI3K/AKT/mTOR pathways-either via mutations or genomic amplification-confers key oncogenic activity, essential for the development and progression of several solid tumors. Alterations in the PIK3CA gene are associated with poor prognosis of solid malignancies. Contradictory reports exist in the literature regarding the prognostic value of PIK3CA in aggressive cancers, but most available data highlights an important role of PIK3CA mutation in mediating tumorigenesis via increased signaling of the PI3K/AKT/mTOR survival pathway. Several inhibitors of PI3K/AKT/mTOR pathways have been investigated as potential therapeutic options in solid malignancies. This article reviews the role of PIK3CA mutations and inhibitors of the PI3K/AKT/mTOR pathway in cancer and examines association with the clinico-pathological parameters and prognosis.

Metabolic Remodeling as a Way of Adapting to Tumor Microenvironment (TME), a Job of Several Holders

The microenvironment depends and generates dependence on all the cells and structures that share the same niche, the biotope. The contemporaneous view of the tumor microenvironment (TME) agrees with this idea. The cells that make up the tumor, whether malignant or not, behave similarly to classes of elements within a living community. These elements inhabit, modify and benefit from all the facilities the microenvironment has to offer and that will contribute to the survival and growth of the tumor and the progression of the disease.The metabolic adaptation to microenvironment is a crucial process conducting to an established tumor able to grow locally, invade and metastasized. The metastatic cancer cells are reasonable more plastic than non-metastatic cancer cells, because the previous ones must survive in the microenvironment where the primary tumor develops and in addition, they must prosper in the microenvironment in the metastasized organ.The metabolic remodeling requires not only the adjustment of metabolic pathways per se but also the readjustment of signaling pathways that will receive and obey to the extracellular instructions, commanding the metabolic adaptation. Many diverse players are pivotal in cancer metabolic fitness from the initial signaling stimuli, going through the activation or repression of genes, until the phenotype display. The new phenotype will permit the import and consumption of organic compounds, useful for energy and biomass production, and the export of metabolic products that are useless or must be secreted for a further recycling or controlled uptake. In the metabolic network, three subsets of players are pivotal: (1) the organic compounds; (2) the transmembrane transporters, and (3) the enzymes.This chapter will present the "Pharaonic" intent of diagraming the interplay between these three elements in an attempt of simplifying and, at the same time, of showing the complex sight of cancer metabolism, addressing the orchestrating role of microenvironment and highlighting the influence of non-cancerous cells.

Trp53 null and R270H mutant alleles have comparable effects in regulating invasion, metastasis, and gene expression in mouse colon tumorigenesis

Somatic APC (adenomatous polyposis coli), TP53, KRAS mutations are present in roughly 80%, 60%, and 40%, respectively, of human colorectal cancers (CRCs). Most TP53 mutant alleles in CRCs encode missense mutant proteins with loss-of-function (LOF) of p53's transcriptional activity and dominant negative (DN) effects on wild-type p53 function. Missense mutant p53 proteins have been reported to exert gain-of-function (GOF) effects in cancer. We compared the phenotypic effects of the common human cancer-associated TP53 R273H missense mutation to p53 null status in a genetically engineered mouse CRC model. Inactivation of one allele of Apc together with activation of a Kras mutant allele in mouse colon epithelium instigated development of serrated and hyperplastic epithelium and adenomas (AK mice). Addition of a Trp53^R270H or Trp53^null mutant allele to the model (AKP mice) led to markedly shortened survival and increased tumor burden relative to that of AK mice, including adenocarcinomas in AKP mice. Comparable life span and tumor burden were seen in AKP mice carrying Trp53^R270H or Trp53^null alleles, along with similar frequencies of spontaneous metastasis to lymph nodes, lung, and liver. The fraction of adenocarcinomas with submucosa or deeper invasion was higher in AKP^270/fl mice than in AKP^fl/fl mice, but the incidence of adenocarcinomas per mouse did not differ significantly between AKP^fl/fl and AKP^270/fl mice. In line with their comparable biological behaviors, mouse primary tumors and tumor-derived organoids with the Trp53^R270H or Trp53^null alleles had highly similar gene expression profiles. Human CRCs with TP53 R273 missense mutant or null alleles also had essentially homogeneous gene expression patterns. Our findings indicate the R270H/R273H p53 mutant protein does not manifest definite GOF biological effects in mouse and human CRCs, suggesting possible GOF effects of mutant p53 in cancer phenotypes are likely allele-specific and/or context-dependent.

Oncogenic Roles of the PI3K/AKT/mTOR Axis

The PI3K/AKT/mTOR pathway is frequently activated in various human cancers and has been considered a promising therapeutic target. Many of the positive regulators of the PI3K/AKT/mTOR axis, including the catalytic (p110α) and regulatory (p85α), of class IA PI3K, AKT, RHEB, mTOR, and eIF4E, possess oncogenic potentials, as demonstrated by transformation assays in vitro and by genetically engineered mouse models in vivo. Genetic evidences also indicate their roles in malignancies induced by activation of the upstream oncoproteins including receptor tyrosine kinases and RAS and those induced by the loss of the negative regulators of the PI3K/AKT/mTOR pathway such as PTEN, TSC1/2, LKB1, and PIPP. Possible mechanisms by which the PI3K/AKT/mTOR axis contributes to oncogenic transformation include stimulation of proliferation, survival, metabolic reprogramming, and invasion/metastasis, as well as suppression of autophagy and senescence. These phenotypic changes are mediated by eIF4E-induced translation of a subset of mRNAs and by other downstream effectors of mTORC1 including S6K, HIF-1α, PGC-1α, SREBP, and ULK1 complex.

Role of the PI3K/AKT/mTOR signaling pathway in ovarian cancer: Biological and therapeutic significance

Ovarian cancer (OC) is a lethal gynecological cancer. The phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway plays an important role in the regulation of cell survival, growth, and proliferation. Irregularities in the major components of the PI3K/AKT/mTOR signaling pathway are common in human cancers. Despite the availability of strong pre-clinical and clinical data of PI3K/AKT/mTOR pathway inhibitors in OC, there is no FDA approved inhibitor available for the treatment of OC. Here, we outline the importance of PI3K/AKT/mTOR signaling pathway in OC tumorigenesis, proliferation and progression, and pre-clinical and clinical experience with several PI3K/AKT/mTOR pathway inhibitors in OC.

Challenges for the Clinical Development of PI3K Inhibitors: Strategies to Improve Their Impact in Solid Tumors

The PI3K pathway is mutated and aberrantly activated in many cancers and plays a central role in tumor cell proliferation and survival, making it a rational therapeutic target. Until recently, however, results from clinical trials with PI3K inhibitors in solid tumors have been largely disappointing. Here, we describe several factors that have limited the success of these agents, including the weak driver oncogenic activity of mutant PI3K, suboptimal patient selection in trials, drug-related toxicities, feedback upregulation of compensatory mechanisms when PI3K is blocked, increased insulin production upon PI3Kα inhibition, lack of mutant-specific inhibitors, and a relative scarcity of studies using combinations with PI3K antagonists. We also suggest strategies to improve the impact of these agents in solid tumors. Despite these challenges, we are optimistic that isoform-specific PI3K inhibitors, particularly in combination with other agents, may be valuable in treating appropriately selected patients with PI3K-dependent tumors. SIGNIFICANCE: Despite the modest clinical activity of PI3K inhibitors in solid tumors, there is an increasing understanding of the factors that may have limited their success. Strategies to ameliorate drug-related toxicities, use of rational combinations with PI3K antagonists, development of mutant-selective PI3K inhibitors, and better patient selection should improve the success of these targeted agents against solid tumors.

When Is "Type I" Ovarian Cancer Not "Type I"? Indications of an Out-Dated Dichotomy

The dualistic classification of epithelial ovarian cancer (EOC) into “type I” and “type II” is widely applied in the research setting; it is used as a convenient way of conceptualizing different mechanisms of tumorigenesis. However, this classification conflicts with recent molecular insights of the etiology of EOC. Molecular and cell of origin studies indicate that while type II tumors could be classed together, type I tumors are not homogenous, even within the histological types, and can have poor clinical outcomes. Type II high grade serous carcinoma and type I low grade serous carcinomas best fit the description of the dualistic model, with different precursors, and distinct molecular profiles. However, endometriosis-associated cancers should be considered a separate group, without assuming an indolent course or type I genetic profiles. Furthermore, the very clear differences between mucinous ovarian carcinomas and other type I tumors, including an uncertain origin, and heterogeneous mutational spectrum and clinical behavior, indicate a non-type I classification for this entity. The impression that only type II carcinomas are aggressive, have poor prognosis, and carry TP53 mutations is an unhelpful misinterpretation of the dualistic classification. In this review, we revisit the history of EOC classification, and discuss the misunderstanding of the dualistic model by comparing the clinical and molecular heterogeneity of EOC types. We also emphasize that all EOC research, both basic and clinical, should consider the subtypes as different diseases beyond the type I/type II model, and base novel therapies on the molecular characteristics of each tumor.

The Endometriotic Tumor Microenvironment in Ovarian Cancer

Women with endometriosis are at increased risk of developing ovarian cancer, specifically ovarian endometrioid, low-grade serous, and clear-cell adenocarcinoma. An important clinical caveat to the association of endometriosis with ovarian cancer is the improved prognosis for women with endometriosis at time of ovarian cancer staging. Whether endometriosis-associated ovarian cancers develop from the molecular transformation of endometriosis or develop because of the endometriotic tumor microenvironment remain unknown. Additionally, how the presence of endometriosis improves prognosis is also undefined, but likely relies on the endometriotic microenvironment. The unique tumor microenvironment of endometriosis is composed of epithelial, stromal, and immune cells, which adapt to survive in hypoxic conditions with high levels of iron, estrogen, and inflammatory cytokines and chemokines. Understanding the unique molecular features of the endometriotic tumor microenvironment may lead to impactful precision therapies and/or modalities for prevention. A challenge to this important study is the rarity of well-characterized clinical samples and the limited model systems. In this review, we will describe the unique molecular features of endometriosis-associated ovarian cancers, the endometriotic tumor microenvironment, and available model systems for endometriosis-associated ovarian cancers. Continued research on these unique ovarian cancers may lead to improved prevention and treatment options.

Glutathione in Ovarian Cancer: A Double-Edged Sword

Glutathione (GSH) has several roles in a cell, such as a reactive oxygen species (ROS) scavenger, an intervenient in xenobiotics metabolism and a reservoir of cysteine. All of these activities are important in the maintenance of normal cells homeostasis but can also constitute an advantage for cancer cells, allowing disease progression and resistance to therapy. Ovarian cancer is the major cause of death from gynaecologic disease and the second most common gynaecologic malignancy worldwide. In over 50 years, the overall survival of patients diagnosed with epithelial ovarian cancer has not changed, regardless of the efforts concerning early detection, radical surgery and new therapeutic approaches. Late diagnosis and resistance to therapy are the main causes of this outcome, and GSH is profoundly associated with chemoresistance to platinum salts, which, together with taxane-based chemotherapy and surgery, are the main therapy strategies in ovarian cancer treatment. Herein, we present some insights into the role of GSH in the poor prognosis of ovarian cancer, and also point out how some strategies underlying the dependence of ovarian cancer cells on GSH can be further used to improve the effectiveness of therapy.

Protein expression patterns in cancer-associated fibroblasts and cells undergoing the epithelial-mesenchymal transition in ovarian cancers

Recent studies have shown that cancer-associated fibroblasts (CAFs) and the epithelial-mesenchymal transition (EMT) contribute to invasive and metastatic abilities of ovarian cancer (OC) cells. In the present study, we attempted to identify the role of CAF- and EMT-related proteins in OCs, including serous carcinoma, mucinous carcinoma, endometrioid carcinoma and clear cell carcinoma using an immunohistochemical approach. The following CAF-related markers were used: CD10, podoplanin, fibroblast activating protein (FAP), platelet derived growth factor receptor (PDGFRα), PDGFRβ, S100A4 and α-smooth muscle actin (α-SMA). In addition, the following EMT-related markers were investigated: Slug, TWIST1 and ZEB1We performed hierarchical cluster analysis to group the samples according to their scoring. Subgroup 1 was characterized by high expression of CD10, podoplanin, α-SMA, Slug and ZEB1, whereas subgroup 2 was closely associated with high expression of podoplanin, PDGFRα, PDGFRβ, α-SMA, and Slug. In addition, marked expression of CD10 was observed in subgroup 3. High expression of α-SMA was a distinctive feature in subgroup 4, and expression of podoplanin and α-SMA characterized subgroup 5. Each subgroup was correlated with a histological type. The fact that different histological types were associated with different subgroups suggests the presence of distinct and heterogeneous subpopulations of CAFs in OC.

The expression of IMP3 in 366 cases with ovarian carcinoma of high grade serous, endometrioid and clear cell subtypes

The clear cell (CCC), high grade serous (HGSC) and endometrioid (EC) ovarian carcinomas share overlapping histological features. The oncogene IMP3 is implicated in CCC with an elusive utility in differential diagnosis. We collected 366 cases with ovarian primary carcinomas to detect IMP3, Napsin-A and HNF-1β by immunochemistry. In 351 cases, the positive expression rate of IMP3 in CCC was significantly higher than that either in EC or HGSC (p < 0.01). The sensitivity of IMP3 in CCC was higher than Napsin-A but lower than HNF-1β (p < 0.01). The specificity of IMP3 in CCC was lower than Napsin-A but higher than HNF-1β (p < 0.01). The composite markers Napsin-A+/IMP3+ and the IMP3+/HNF-1β+/Napsin-A+ offered the highest odds ratio (p < 0.001), the highest specificity, the highest positive predictive value and the highest positive likelihood ratio. The ROC analysis showed that the combination of Napsin-A, HNF-1β and IMP3 offered the biggest AUC compared with either the singular marker performances or the other binary combinations (p < 0.001). In 15 cases of EC mixed with CCC, IMP3 showed a better discrimination value than the other two markers. Consequently, adding IMP3 to the diagnostic panel might provide some help with the pathological diagnosis of ovarian CCC.

Epithelialization of mouse ovarian tumor cells originating in the fallopian tube stroma

Epithelial ovarian carcinoma accounts for 90% of all ovarian cancer and is the most deadly gynecologic malignancy. Recent studies have suggested that fallopian tube fimbriae can be the origin of cells for high-grade serous subtype of epithelial ovarian carcinoma (HGSOC). A mouse HGSOC model with conditional Dicer-Pten double knockout (Dicer-Pten DKO) developed primary tumors, intriguingly, from the fallopian tube stroma. We examined the growth and epithelial phenotypes of the Dicer-Pten DKO mouse tumor cells contributable by each gene knockout. Unlike human ovarian epithelial cancer cells that expressed full-length E-cadherin, the Dicer-Pten DKO stromal tumor cells expressed cleaved E-cadherin fragments and metalloproteinase 2, a mixture of epithelial and mesenchymal markers. Although the Dicer-Pten DKO tumor cells lost the expression of mature microRNAs as expected, they showed high levels of tRNA fragment expression and enhanced AKT activation due to the loss of PTEN function. Introduction of a Dicer1-expressing construct into the DKO mouse tumor cells significantly reduced DNA synthesis and the cell growth rate, with concurrent diminished adhesion and ZO1 epithelial staining. Hence, it is likely that the loss of Dicer promoted mesenchymal-epithelial transition in fallopian tube stromal cells, and in conjunction with Pten loss, further promoted cell proliferation and epithelial-like tumorigenesis.

Ovarian tumour growth is characterized by mevalonate pathway gene signature in an orthotopic, syngeneic model of epithelial ovarian cancer

Epithelial ovarian cancer (EOC) is the most lethal gynecological cancer and often is not detected until late stages when cancer cells transcoelomically metastasize to the abdomen and typically become resistant to therapy resulting in very low survival rates. We utilize an orthotopic, syngeneic mouse model to study late stage disease and have discovered that the tumor cells within the abdominal ascites are irreversibly re-programmed, with an increased tumorigenicity and resistance to apoptosis. The goal of this study was to characterize the reprogramming that occurred in the aggressive ascites-derived cells (28-2 cells) compared to the original cell line used for tumor induction (ID8 cells). Microarray experiments showed that the majority of genes upregulated in the 28-2 cells belonged to the mevalonate pathway, which is involved in cholesterol biosynthesis, protein prenylation, and activation of small GTPases. Upregulation of mevalonate appeared to be associated with the acquisition of a p53 mutation in the ascites-derived cells. Treatment with simvastatin to inhibit HMG CoA reductase, the rate limiting enzyme of this pathway, induced apoptosis in the 28-2 cell line. Rescue experiments revealed that mevalonate, but not cholesterol, could inhibit the simvastatin-mediated effects. In vivo, daily intraperitoneal simvastatin treatment significantly regressed advanced stage disease and induced death of metastatic tumor cells. These data suggest that ovarian cancer cells become reprogrammed, with genetic mutations, and upregulation of the mevalonate pathway, which facilitates the development of advanced stage disease. The use of statins to inhibit HMGCR may provide novel therapeutic opportunities for the treatment of advanced stage EOC.

Sequential molecular changes and dynamic oxidative stress in high-grade serous ovarian carcinogenesis

The mechanism of high-grade serous ovarian cancer (HGSC) development remains elusive. This review outlines recent advances in the understanding of sequential molecular changes associated with the development of HGSC, as well as describes oxidative stress-induced genomic instability and carcinogenesis. This article reviews the English language literature between 2005 and 2017. Clinicopathological features analysis provides a sequential progression of fallopian tubal epithelium to precursor lesions to type 2 HGSC. HGSC may develop over a long time after incessant ovulation and repeated retrograde menstruation via stepwise accumulation of genetic alterations, including PAX2, ALDH1A1, STMN1, EZH2 and CCNE1, which confer positive selection of cells with growth advantages through acquiring driver mutations such as BRCA1/2, p53 or PTEN/PIK3CA. Haemoglobin and iron-induced oxidative stress leads to the emergence of genetic alterations in fallopian tubal epithelium via increased DNA damage and impaired DNA repair. Serous tubal intraepithelial carcinoma (STIC), the likely precursor of HGSC, may be susceptible to DNA double-strand breaks, exhibit DNA replication stress and increase genomic instability. The induction of genomic instability is considered to be a driving mechanism of reactive oxygen species (ROS)-induced carcinogenesis. HGSC exemplifies the view of stepwise cancer development. We describe how genetic alterations emerge during HGSC carcinogenesis related to oxidative stress.

A synthetic peptide hijacks the catalytic subunit of class I PI3K to suppress the growth of cancer cells

Activation of class I Phosphoinositide 3-kinases (PI3Ks) by mutation or overexpression closely correlates with the development of various human cancers. Class I PI3Ks are heterodimers composed of p110 catalytic subunits and regulatory subunits represented by p85. PAQR3 has been found to inhibit p110α activity by blocking its interaction with p85. In this study, we identified the N-terminal 6-55 amino acid residues of PAQR3 being sufficient for its interaction with p110α. A synthetic peptide, P6-55, that contains the N-terminus of PAQR3 could disrupt the interactions of p110α with both PAQR3 and p85. The activity of PI3K was also inhibited by P6-55, accompanied by significant inhibition of cancer cell proliferation. In a xenograft mouse model, P6-55 was able to reduce tumor growth in vivo. Furthermore, P6-55 was capable of inhibiting the elevated basal PI3K activity of H1047R, a hotspot mutation found in many types of human cancers. The cell proliferation and migration of cancer cells bearing H1047R mutation were also reduced by P6-55. In conclusion, our study provides a proof of concept that blocking the interaction of p110α with p85 by a peptide can serve as a new strategy to inhibit the oncogenic activity of PI3K in cancer therapy.

A combined biomarker panel shows improved sensitivity for the early detection of ovarian cancer allowing the identification of the most aggressive type II tumours

Background:

There is an urgent need for biomarkers for the early detection of ovarian cancer (OC). The purpose of this study was to assess whether changes in serum levels of lecithin-cholesterol acyltransferase (LCAT), sex hormone-binding globulin (SHBG), glucose-regulated protein, 78 kDa (GRP78), calprotectin and insulin-like growth factor-binding protein 2 (IGFBP2) are observed before clinical presentation and to assess the performance of these markers alone and in combination with CA125 for early detection.

Methods:

This nested case–control study used samples from the United Kingdom Collaborative Trial of Ovarian Cancer Screening trial. The sample set consisted of 482 serum samples from 49 OC subjects and 31 controls, with serial samples spanning up to 7 years pre-diagnosis. The set was divided into the following: (I) a discovery set, which included all women with only two samples from each woman, the first at<14 months and the second at >32 months to diagnosis; and (ii) a corroboration set, which included all the serial samples from the same women spanning the 7-year period. Lecithin-cholesterol acyltransferase, SHBG, GRP78, calprotectin and IGFBP2 were measured using ELISA. The performance of the markers to detect cancers pre-diagnosis was assessed.

Results:

A combined threshold model IGFBP2 >78.5 ng ml⁻¹ : LCAT <8.831 μg ml⁻¹ : CA125 >35 U ml⁻¹ outperformed CA125 alone for the earlier detection of OC. The threshold model was able to identify the most aggressive Type II cancers. In addition, it increased the lead time by 5–6 months and identified 26% of Type I subjects and 13% of Type II subjects that were not identified by CA125 alone.

Conclusions:

Combined biomarker panels (IGFBP2, LCAT and CA125) outperformed CA125 up to 3 years pre-diagnosis, identifying cancers missed by CA125, providing increased diagnostic lead times for Type I and Type II OC. The model identified more aggressive Type II cancers, with women crossing the threshold dying earlier, indicating that these markers can improve on the sensitivity of CA125 alone for the early detection of OC.

Impact of oviductal versus ovarian epithelial cell of origin on ovarian endometrioid carcinoma phenotype in the mouse

Endometrioid carcinoma (EC) is a relatively indolent ovarian carcinoma subtype that is nonetheless deadly if detected late. Existing genetically engineered mouse models (GEMMs) of the disease, based on transformation of the ovarian surface epithelium (OSE), take advantage of known ovarian EC driver gene lesions, but do not fully recapitulate the disease features seen in patients. An EC model in which the Apc and Pten tumour suppressor genes are conditionally deleted in murine OSE yields tumours that are biologically more aggressive and significantly less differentiated than human ECs. Importantly, OSE is not currently thought to be the tissue of origin of most ovarian cancers, including ECs, suggesting that tumour initiation in Müllerian epithelium may produce tumours that more closely resemble their human tumour counterparts. We have developed Ovgp1-iCreER^T2 mice in which the Ovgp1 promoter controls expression of tamoxifen (TAM)-regulated Cre recombinase in oviductal epithelium - the murine equivalent of human Fallopian tube epithelium. Ovgp1-iCreER^T2 ;Apc^fl/fl ;Pten^fl/fl mice treated with TAM or injected with adenovirus expressing Cre into the ovarian bursa uniformly develop oviductal or ovarian ECs, respectively. On the basis of their morphology and global gene expression profiles, the oviduct-derived tumours more closely resemble human ovarian ECs than do OSE-derived tumours. Furthermore, mice with oviductal tumours survive much longer than their counterparts with ovarian tumours. The slow progression and late metastasis of oviductal tumours resembles the relatively indolent behaviour characteristic of so-called Type I ovarian carcinomas in humans, for which EC is a prototype. Our studies demonstrate the utility of Ovgp1-iCreER^T2 mice for manipulating genes of interest specifically in the oviductal epithelium, and establish that the cell of origin is an important consideration in mouse ovarian cancer GEMMs. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

The Functions of MicroRNA-200 Family in Ovarian Cancer: Beyond Epithelial-Mesenchymal Transition

The majority of studies on microRNA-200 family members (miR-200s) in human cancers are based on the premise that miR-200s maintain epithelial cell integrity by suppressing epithelial-mesenchymal transition (EMT) through direct inhibition of mesenchymal transcription factors zinc finger E-box-binding homeobox 1/2 (ZEB1/ZEB2) and transforming growth factor-β (TGF-β), a potent inducer of EMT. Hence, downregulation of miR-200 in cancer cells promotes EMT and cancer metastasis. Yet, miR-200s are highly expressed in ovarian cancer, and ovarian cancer metastasizes primarily by dissemination within the pelvic cavity. In this review, we will refocus the epithelial property of ovarian cancer cells and the role of miR-200s in safeguarding this property, as well as the diverse roles of miR-200s in inclusion cyst formation, cancer cell growth, collective movement, angiogenesis, exosome-mediated cell communication, and chemoresponse. Taken together, miR-200s play a significant role in the initiation, progression and metastasis of ovarian cancer and may serve as diagnostic biomarkers and a target in therapeutic development.

The Functions of MicroRNA-200 Family in Ovarian Cancer: Beyond Epithelial-Mesenchymal Transition

The majority of studies on microRNA-200 family members (miR-200s) in human cancers are based on the premise that miR-200s maintain epithelial cell integrity by suppressing epithelial-mesenchymal transition (EMT) through direct inhibition of mesenchymal transcription factors zinc finger E-box-binding homeobox 1/2 (ZEB1/ZEB2) and transforming growth factor-β (TGF-β), a potent inducer of EMT. Hence, downregulation of miR-200 in cancer cells promotes EMT and cancer metastasis. Yet, miR-200s are highly expressed in ovarian cancer, and ovarian cancer metastasizes primarily by dissemination within the pelvic cavity. In this review, we will refocus the epithelial property of ovarian cancer cells and the role of miR-200s in safeguarding this property, as well as the diverse roles of miR-200s in inclusion cyst formation, cancer cell growth, collective movement, angiogenesis, exosome-mediated cell communication, and chemoresponse. Taken together, miR-200s play a significant role in the initiation, progression and metastasis of ovarian cancer and may serve as diagnostic biomarkers and a target in therapeutic development.

The Functions of MicroRNA-200 Family in Ovarian Cancer: Beyond Epithelial-Mesenchymal Transition

The majority of studies on microRNA-200 family members (miR-200s) in human cancers are based on the premise that miR-200s maintain epithelial cell integrity by suppressing epithelial-mesenchymal transition (EMT) through direct inhibition of mesenchymal transcription factors zinc finger E-box-binding homeobox 1/2 (ZEB1/ZEB2) and transforming growth factor-β (TGF-β), a potent inducer of EMT. Hence, downregulation of miR-200 in cancer cells promotes EMT and cancer metastasis. Yet, miR-200s are highly expressed in ovarian cancer, and ovarian cancer metastasizes primarily by dissemination within the pelvic cavity. In this review, we will refocus the epithelial property of ovarian cancer cells and the role of miR-200s in safeguarding this property, as well as the diverse roles of miR-200s in inclusion cyst formation, cancer cell growth, collective movement, angiogenesis, exosome-mediated cell communication, and chemoresponse. Taken together, miR-200s play a significant role in the initiation, progression and metastasis of ovarian cancer and may serve as diagnostic biomarkers and a target in therapeutic development.

Prediction of therapy response in ovarian cancer: Where are we now?

Therapy resistance is a major challenge in the management of ovarian cancer (OC). Advances in detection and new technology validation have led to the emergence of biomarkers that can predict responses to available therapies. It is important to identify predictive biomarkers to select resistant and sensitive patients in order to reduce important toxicities, to reduce costs and to increase survival. The discovery of predictive and prognostic biomarkers for monitoring therapy is a developing field and provides promising perspectives in the era of personalized medicine. This review article will discuss the biology of OC with a focus on targetable pathways; current therapies; mechanisms of resistance; predictive biomarkers for chemotherapy, antiangiogenic and DNA-targeted therapies, and optimal cytoreductive surgery; and the emergence of liquid biopsy using recent studies from the Medline database and ClinicalTrials.gov.

Emerging diagnostic, prognostic and therapeutic biomarkers for ovarian cancer

BACKGROUND

In spite of various treatment options currently available, ovarian cancer (OC) still remains a leading cause of death in women world-wide. Diagnosis at an early stage is one of the most important factors that determines survival. Current clinical diagnostic tools have, however, a limited efficacy in early OC detection. Therefore, there is a critical need for new (early) diagnostic biomarkers and tools. Through advances in genomic, proteomic and metabolomic techniques, several novel molecular OC biomarkers have recently been identified. These biomarkers are currently subject to validation. In addition, integration of genomic, proteomic and metabolomic data, in conjunction with epidemiologic and clinical data, is considered essential for obtaining useful results. Interesting recent work has already shown that specific diagnostic biomarkers, such as BRCA mutations, may have profound therapeutic implications. Here, we review the current state of OC research through literature and database searches, with a focus on various recently identified biomarkers via different technologies for the (early) diagnosis, prognosis and treatment of OC.

CONCLUSIONS

Multi-biomarker panels accompanied by a meticulous determination of their sensitivity and specificity, as well their validation, using multivariate analyses will be critical for its clinical application, including early OC detection and tailor-made OC treatment.

Recent Advances in Understanding, Diagnosing, and Treating Ovarian Cancer

Ovarian cancer, a term that encompasses ovarian, fallopian, and peritoneal cancers, is the leading cause of gynecologic cancer mortality. To improve patient outcomes, the field is currently focused on defining the mechanisms of cancer formation and spread, early diagnosis and prevention, and developing novel therapeutic options. This review summarizes recent advances in these areas.

Novel risk models for early detection and screening of ovarian cancer

PURPOSE

Ovarian cancer (OC) is the most lethal gynaecological cancer. Early detection is required to improve patient survival. Risk estimation models were constructed for Type I (Model I) and Type II (Model II) OC from analysis of Protein Z, Fibronectin, C-reactive protein and CA125 levels in prospectively collected samples from the United Kingdom Collaborative Trial of Ovarian Cancer Screening (UKCTOCS).

RESULTS

Model I identifies cancers earlier than CA125 alone, with a potential lead time of 3-4 years. Model II detects a number of high grade serous cancers at an earlier stage (Stage I/II) than CA125 alone, with a potential lead time of 2-3 years and assigns high risk to patients that the ROCA Algorithm classified as normal.

MATERIALS AND METHODS

This nested case control study included 418 individual serum samples serially collected from 49 OC cases and 31 controls up to six years pre-diagnosis. Discriminatory logit models were built combining the ELISA results for candidate proteins with CA125 levels.

CONCLUSIONS

These models have encouraging sensitivities for detecting pre-clinical ovarian cancer, demonstrating improved sensitivity compared to CA125 alone. In addition we demonstrate how the models improve on ROCA for some cases and outline their potential future use as clinical tools.

Emerging diagnostic, prognostic and therapeutic biomarkers for ovarian cancer

BACKGROUND

In spite of various treatment options currently available, ovarian cancer (OC) still remains a leading cause of death in women world-wide. Diagnosis at an early stage is one of the most important factors that determines survival. Current clinical diagnostic tools have, however, a limited efficacy in early OC detection. Therefore, there is a critical need for new (early) diagnostic biomarkers and tools. Through advances in genomic, proteomic and metabolomic techniques, several novel molecular OC biomarkers have recently been identified. These biomarkers are currently subject to validation. In addition, integration of genomic, proteomic and metabolomic data, in conjunction with epidemiologic and clinical data, is considered essential for obtaining useful results. Interesting recent work has already shown that specific diagnostic biomarkers, such as BRCA mutations, may have profound therapeutic implications. Here, we review the current state of OC research through literature and database searches, with a focus on various recently identified biomarkers via different technologies for the (early) diagnosis, prognosis and treatment of OC.

CONCLUSIONS

Multi-biomarker panels accompanied by a meticulous determination of their sensitivity and specificity, as well their validation, using multivariate analyses will be critical for its clinical application, including early OC detection and tailor-made OC treatment.

Emerging diagnostic, prognostic and therapeutic biomarkers for ovarian cancer

BACKGROUND

In spite of various treatment options currently available, ovarian cancer (OC) still remains a leading cause of death in women world-wide. Diagnosis at an early stage is one of the most important factors that determines survival. Current clinical diagnostic tools have, however, a limited efficacy in early OC detection. Therefore, there is a critical need for new (early) diagnostic biomarkers and tools. Through advances in genomic, proteomic and metabolomic techniques, several novel molecular OC biomarkers have recently been identified. These biomarkers are currently subject to validation. In addition, integration of genomic, proteomic and metabolomic data, in conjunction with epidemiologic and clinical data, is considered essential for obtaining useful results. Interesting recent work has already shown that specific diagnostic biomarkers, such as BRCA mutations, may have profound therapeutic implications. Here, we review the current state of OC research through literature and database searches, with a focus on various recently identified biomarkers via different technologies for the (early) diagnosis, prognosis and treatment of OC.

CONCLUSIONS

Multi-biomarker panels accompanied by a meticulous determination of their sensitivity and specificity, as well their validation, using multivariate analyses will be critical for its clinical application, including early OC detection and tailor-made OC treatment.

Loss of E-cadherin disrupts ovarian epithelial inclusion cyst formation and collective cell movement in ovarian cancer cells

Increased inclusion cyst formation in the ovary is associated with ovarian cancer development. We employed in vitro three-dimensional (3D) organotypic models formed by normal human ovarian surface epithelial (OSE) cells and ovarian cancer cells to study the morphologies of normal and cancerous ovarian cortical inclusion cysts and the molecular changes during their transitions into stromal microenvironment. When compared with normal cysts that expressed tenascin, the cancerous cysts expressed high levels of laminin V and demonstrated polarized structures in Matrigel; and the cancer cells migrated collectively when the cyst structures were positioned in a stromal-like collagen I matrix. The molecular markers identified in the in vitro 3D models were verified in clinical samples. Network analysis of gene expression of the 3D structures indicates concurrent downregulation of transforming growth factor beta pathway genes and high levels of E-cadherin and microRNA200 (miR200) expression in the cancerous cysts and the migrating cancer cells. Transient silencing of E-cadherin expression in ovarian cancer cells disrupted cyst structures and inhibited collective cell migration. Taken together, our studies employing 3D models have shown that E-cadherin is crucial for ovarian inclusion cyst formation and collective cancer cell migration.

Tumorigenesis and peritoneal colonization from fallopian tube epithelium

Ovarian cancer is the most lethal gynecological malignancy, primarily because its origin and initiation factors are unknown. A secretory murine oviductal epithelial (MOE) model was generated to address the hypothesis that the fallopian tube is an origin for high-grade serous cancer. MOE cells were stably altered to express mutation in p53, silence PTEN, activate AKT, and amplify KRAS alone and in combination, to define if this cell type gives rise to tumors and what genetic alterations are required to drive malignancy. Cell lines were characterized in vitro and allografted into mice. Silencing PTEN formed high-grade carcinoma with wide spread tumor explants including metastasis into the ovary. Addition of p53 mutation to PTEN silencing did not enhance this phenotype, whereas addition of KRAS mutation reduced survival. Interestingly, PTEN silencing and KRAS mutation originating from ovarian surface epithelium generated endometrioid carcinoma, suggesting that different cellular origins with identical genetic manipulations can give rise to distinct cancer histotypes. Defining the roles of specific signaling modifications in tumorigenesis from the fallopian tube/oviduct is essential for early detection and development of targeted therapeutics. Further, syngeneic MOE allografts provide an ideal model for pre-clinical testing in an in vivo environment with an intact immune system.

Protein Z: A putative novel biomarker for early detection of ovarian cancer

Ovarian cancer (OC) has the highest mortality of all gynaecological cancers. Early diagnosis offers an approach to achieving better outcomes. We conducted a blinded-evaluation of prospectively collected preclinical serum from participants in the multimodal group of the United Kingdom Collaborative Trial of Ovarian Cancer Screening. Using isobaric tags (iTRAQ) we identified 90 proteins differentially expressed between OC cases and controls. A second targeted mass spectrometry analysis of twenty of these candidates identified Protein Z as a potential early detection biomarker for OC. This was further validated by ELISA analysis in 482 serial serum samples, from 80 individuals, 49 OC cases and 31 controls, spanning up to 7 years prior to diagnosis. Protein Z was significantly down-regulated up to 2 years pre-diagnosis (p = 0.000000411) in 8 of 19 Type I patients whilst in 5 Type II individuals, it was significantly up-regulated up to 4 years before diagnosis (p = 0.01). ROC curve analysis for CA-125 and CA-125 combined with Protein Z showed a statistically significant (p = 0.00033) increase in the AUC from 77 to 81% for Type I and a statistically significant (p= 0.00003) increase in the AUC from 76 to 82% for Type II. Protein Z is a novel independent early detection biomarker for Type I and Type II ovarian cancer; which can discriminate between both types. Protein Z also adds to CA-125 and potentially the Risk of Ovarian Cancer algorithm in the detection of both subtypes.

Models of endometriosis and their utility in studying progression to ovarian clear cell carcinoma

Endometriosis is a common benign gynaecological condition affecting at least 10% of women of childbearing age and is characterized by pain--frequently debilitating. Although the exact prevalence is unknown, the economic burden is substantial (∼$50 billion a year in the USA alone) and it is associated with considerable morbidity. The development of endometriosis is inextricably linked to the process of menstruation and thus the models that best recapitulate the human disease are in menstruating non-human primates. However, the use of these animals is ethically challenging and very expensive. A variety of models in laboratory animals have been developed and the most recent are based on generating menstrual-like endometrial tissue that can be transferred to a recipient animal. These models are genetically manipulable and facilitate precise mechanistic studies. In addition, these models can be used to study malignant transformation in epithelial ovarian carcinoma. Epidemiological and molecular evidence indicates that endometriosis is the most plausible precursor of both clear cell and endometrioid ovarian cancer (OCCA and OEA, respectively). While this progression is rare, understanding the underlying mechanisms of transformation may offer new strategies for prevention and therapy. Our ability to pursue this is highly dependent on improved animal models but the current transgenic models, which genetically modify the ovarian surface epithelium and oviduct, are poor models of ectopic endometrial tissue. In this review we describe the various models of endometriosis and discuss how they may be applicable to developing our mechanistic understanding of OCCA and OEA.

Mutant p53 Promotes Epithelial Ovarian Cancer by Regulating Tumor Differentiation, Metastasis, and Responsiveness to Steroid Hormones

Mutations in the tumor protein p53 (TP53) are the most frequently occurring genetic events in high-grade ovarian cancers, especially the prevalence of the Trp53(R172H)-mutant allele. In this study, we investigated the impact of the Trp53(R172H)-mutant allele on epithelial ovarian cancer (EOC) in vivo We used the Pten/Kras(G12D)-mutant mouse strain that develops serous EOC with 100% penetrance to introduce the mutant Trp53(R172H) allele (homolog for human Trp53(R172H)). We demonstrate that the Trp53(R172H) mutation promoted EOC but had differential effects on disease features and progression depending on the presence or absence of the wild-type (WT) TP53 allele. Heterozygous WT/Trp53(R172H) alleles facilitated invasion into the ovarian stroma, accelerated intraperitoneal metastasis, and reduced TP53 transactivation activity but retained responsiveness to nutlin-3a, an activator of WT TP53. Moreover, high levels of estrogen receptor α in these tumors enhanced the growth of both primary and metastatic tumors in response to estradiol. Ovarian tumors homozygous for Trp53(R172H) mutation were undifferentiated and highly metastatic, exhibited minimal TP53 transactivation activity, and expressed genes with potential regulatory functions in EOC development. Notably, heterozygous WT/Trp53(R172H) mice also presented mucinous cystadenocarcinomas at 12 weeks of age, recapitulating human mucinous ovarian tumors, which also exhibit heterozygous TP53 mutations (∼50%-60%) and KRAS mutations. Therefore, we present the first mouse model of mucinous tumor formation from ovarian cells and supporting evidence that mutant TP53 is a key regulator of EOC progression, differentiation, and responsiveness to steroid hormones. Cancer Res; 76(8); 2206-18. ©2016 AACR.

Arid1a inactivation in an Apc- and Pten-defective mouse ovarian cancer model enhances epithelial differentiation and prolongs survival

Inactivation of the ARID1A tumour suppressor gene is frequent in ovarian endometrioid (OEC) and clear cell (OCCC) carcinomas, often in conjunction with mutations activating the PI3K-AKT and/or canonical Wnt signalling pathways. Prior work has shown that conditional bi-allelic inactivation of the Apc and Pten tumour suppressor genes in the mouse ovarian surface epithelium (OSE) promotes outgrowth of tumours that reflect the biological behaviour and gene expression profiles of human OECs harbouring comparable Wnt and PI3K-AKT pathway defects, although the mouse tumours are more poorly differentiated than their human tumour counterparts. We found that conditional inactivation of one or both Arid1a alleles in OSE concurrently with Apc and Pten inactivation unexpectedly prolonged the survival of tumour-bearing mice and promoted striking epithelial differentiation of the cancer cells, resulting in morphological features akin to those in human OECs. Enhanced epithelial differentiation was linked to reduced expression of the mesenchymal markers N-cadherin and vimentin, and increased expression of the epithelial markers Crb3 and E-cadherin. Global gene expression profiling showed enrichment for genes associated with mesenchymal-epithelial transition in the Arid1a-deficient tumours. We also found that an activating (E545K) Pik3ca mutation, unlike Pten inactivation or Pik3ca H1047R mutation, cannot cooperate with Arid1a loss to promote ovarian cancer development in the mouse. Our results indicate that the Arid1a tumour suppressor gene has a key role in regulating OEC differentiation, and paradoxically the mouse cancers with more initiating tumour suppressor gene defects had a less aggressive phenotype than cancers arising from fewer gene alterations. Microarray data have been deposited in NCBI's Gene Expression Omnibus (GSE67695).

Spontaneous Transformation of Murine Oviductal Epithelial Cells: A Model System to Investigate the Onset of Fallopian-Derived Tumors

High-grade serous carcinoma (HGSC) is the most lethal ovarian cancer histotype. The fallopian tube secretory epithelial cells (FTSECs) are a proposed progenitor cell type. Genetically altered FTSECs form tumors in mice; however, a spontaneous HGSC model has not been described. Apart from a subpopulation of genetically predisposed women, most women develop ovarian cancer spontaneously, which is associated with aging and lifetime ovulations. A murine oviductal cell line (MOE(LOW)) was developed and continuously passaged in culture to mimic cellular aging (MOE(HIGH)). The MOE(HIGH) cellular model exhibited a loss of acetylated tubulin consistent with an outgrowth of secretory epithelial cells in culture. MOE(HIGH) cells proliferated significantly faster than MOE(LOW), and the MOE(HIGH) cells produced more 2D foci and 3D soft agar colonies as compared to MOE(LOW) MOE(HIGH) were xenografted into athymic female nude mice both in the subcutaneous and the intraperitoneal compartments. Only the subcutaneous grafts formed tumors that were negative for cytokeratin, but positive for oviductal markers, such as oviductal glycoprotein 1 and Pax8. These tumors were considered to be poorly differentiated carcinoma. The differential molecular profiles between MOE(HIGH) and MOE(LOW) were determined using RNA-Seq and confirmed by protein expression to uncover pathways important in transformation, like the p53 pathway, the FOXM1 pathway, WNT signaling, and splicing. MOE(HIGH) had enhanced protein expression of c-myc, Cyclin E, p53, and FOXM1 with reduced expression of p21. MOE(HIGH) were also less sensitive to cisplatin and DMBA, which induce lesions typically repaired by base-excision repair. A model of spontaneous tumorogenesis was generated starting with normal oviductal cells. Their transition to cancer involved alterations in pathways associated with high-grade serous cancer in humans.

CD24+ Ovarian Cancer Cells Are Enriched for Cancer-Initiating Cells and Dependent on JAK2 Signaling for Growth and Metastasis

Ovarian cancer is known to be composed of distinct populations of cancer cells, some of which demonstrate increased capacity for cancer initiation and/or metastasis. The study of human cancer cell populations is difficult due to long requirements for tumor growth, interpatient variability, and the need for tumor growth in immune-deficient mice. We therefore characterized the cancer initiation capacity of distinct cancer cell populations in a transgenic murine model of ovarian cancer. In this model, conditional deletion of Apc, Pten, and Trp53 in the ovarian surface epithelium (OSE) results in the generation of high-grade metastatic ovarian carcinomas. Cell lines derived from these murine tumors express numerous putative stem cell markers, including CD24, CD44, CD90, CD117, CD133, and ALDH. We show that CD24(+) and CD133(+) cells have increased tumor sphere-forming capacity. CD133(+) cells demonstrated a trend for increased tumor initiation while CD24(+) cells versus CD24(-) cells had significantly greater tumor initiation and tumor growth capacity. No preferential tumor-initiating or growth capacity was observed for CD44(+), CD90(+), CD117(+), or ALDH(+) versus their negative counterparts. We have found that CD24(+) cells, compared with CD24(-) cells, have increased phosphorylation of STAT3 and increased expression of STAT3 target Nanog and c-myc. JAK2 inhibition of STAT3 phosphorylation preferentially induced cytotoxicity in CD24(+) cells. In vivo JAK2 inhibitor therapy dramatically reduced tumor metastases, and prolonged overall survival. These findings indicate that CD24(+) cells play a role in tumor migration and metastasis and support JAK2 as a therapeutic target in ovarian cancer.

Mutant p53 expression in fallopian tube epithelium drives cell migration

Ovarian cancer is the fifth leading cause of cancer death among US women. Evidence supports the hypothesis that high-grade serous ovarian cancers (HGSC) may originate in the distal end of the fallopian tube. Although a heterogeneous disease, 96% of HGSC contain mutations in p53. In addition, the "p53 signature," or overexpression of p53 protein (usually associated with mutation), is a potential precursor lesion of fallopian tube derived HGSC suggesting an essential role for p53 mutation in early serous tumorigenesis. To further clarify p53-mutation dependent effects on cells, murine oviductal epithelial cells (MOE) were stably transfected with a construct encoding for the R273H DNA binding domain mutation in p53, the most common mutation in HGSC. Mutation in p53 was not sufficient to transform MOE cells but did significantly increase cell migration. A similar p53 mutation in murine ovarian surface epithelium (MOSE), another potential progenitor cell for serous cancer, was not sufficient to transform the cells nor change migration suggesting tissue specific effects of p53 mutation. Microarray data confirmed expression changes of pro-migratory genes in p53(R273H) MOE compared to parental cells, which could be reversed by suppressing Slug expression. Combining p53(R273H) with KRAS(G12V) activation caused transformation of MOE into high-grade sarcomatoid carcinoma when xenografted into nude mice. Elucidating the specific role of p53(R273H) in the fallopian tube will improve understanding of changes at the earliest stage of transformation. This information can help develop chemopreventative strategies to prevent the accumulation of additional mutations and reverse progression of the "p53 signature" thereby, improving survival rates.

The promise and challenge of ovarian cancer models

The complexity and heterogeneity of ovarian cancer cases are difficult to reproduce in in vitro studies, which cannot adequately elucidate the molecular events involved in tumor initiation and disease metastasis. It has now become clear that, although the multiple histological subtypes of ovarian cancer are being treated with similar surgical and therapeutic approaches, they are in fact characterized by distinct phenotypes, cell of origin, and underlying key genetic and genomic alterations. Consequently, the development of more personalized treatment methodologies, which are aimed at improving patient care and prognosis, will greatly benefit from a better understanding of the key differences between various subtypes. To accomplish this, animal models of all histotypes need to be generated in order to provide accurate in vivo platforms for research and the testing of targeted treatments and immune therapies. Both genetically engineered mouse models (GEMMs) and xenograft models have the ability to further our understanding of key mechanisms facilitating tumorigenesis, and at the same time offer insight into enhanced imaging and treatment modalities. While genetic models may be better suited to examine oncogenic functions and interactions during tumorigenesis, patient-derived xenografts (PDXs) are likely a superior model to assess drug efficacy, especially in concurrent clinical trials, due to their similarity to the tumors from which they are derived. Genetic and avatar models possess great clinical utility and have both benefits and limitations. Additionally, the laying hen model, which spontaneously develops ovarian tumors, has inherent advantages for the study of epithelial ovarian cancer (EOC) and recent work champions this model especially when assessing chemoprevention strategies. While high-grade ovarian serous tumors are the most prevalent form of EOC, rarer ovarian cancer variants, such as small cell ovarian carcinoma of the hypercalcemic type and transitional cell carcinoma, or non-epithelial tumors, including germ cell tumors, will also benefit from the generation of improved models to advance our understanding of tumorigenic mechanisms and the development of selective therapeutic options.

PI3K in cancer: divergent roles of isoforms, modes of activation and therapeutic targeting

Phosphatidylinositol 3-kinases (PI3Ks) are crucial coordinators of intracellular signalling in response to extracellular stimuli. Hyperactivation of PI3K signalling cascades is one of the most common events in human cancers. In this Review, we discuss recent advances in our knowledge of the roles of specific PI3K isoforms in normal and oncogenic signalling, the different ways in which PI3K can be upregulated, and the current state and future potential of targeting this pathway in the clinic.

Advances in tumor screening, imaging, and avatar technologies for high-grade serous ovarian cancer

The majority of high-grade serous ovarian carcinoma cases are detected in advanced stages when treatment options are limited. Surgery is less effective at eradicating the disease when it is widespread, resulting in high rates of disease relapse and chemoresistance. Current screening techniques are ineffective for early tumor detection and consequently, BRCA mutations carriers, with an increased risk for developing high-grade serous ovarian cancer, elect to undergo risk-reducing surgery. While prophylactic surgery is associated with a significant reduction in the risk of cancer development, it also results in surgical menopause and significant adverse side effects. The development of efficient early-stage screening protocols and imaging technologies is critical to improving the outcome and quality of life for current patients and women at increased risk. In addition, more accurate animal models are necessary in order to provide relevant in vivo testing systems and advance our understanding of the disease origin and progression. Moreover, both genetically engineered and tumor xenograft animal models enable the preclinical testing of novel imaging techniques and molecularly targeted therapies as they become available. Recent advances in xenograft technologies have made possible the creation of avatar mice, personalized tumorgrafts, which can be used as therapy testing surrogates for individual patients prior to or during treatment. High-grade serous ovarian cancer may be an ideal candidate for use with avatar models based on key characteristics of the tumorgraft platform. This review explores multiple strategies, including novel imaging and screening technologies in both patients and animal models, aimed at detecting cancer in the early-stages and improving the disease prognosis.