Tumorigenesis and peritoneal colonization from fallopian tube epithelium

Comparative analysis of syngeneic mouse models of high-grade serous ovarian cancer

Ovarian cancers exhibit high rates of recurrence and poor treatment response. Preclinical models that recapitulate human disease are critical to develop new therapeutic approaches. Syngeneic mouse models allow for the generation of tumours comprising the full repertoire of non-malignant cell types but have expanded in number, varying in the cell type of origin, method for transformation, and ultimately, the properties of the tumours they produce. Here we have performed a comparative analysis of high-grade serous ovarian cancer models based on transcriptomic profiling of 22 cell line models, and intrabursal and intraperitoneal tumours from 12. Among cell lines, we identify distinct signalling activity, such as elevated inflammatory signalling in STOSE and OVE16 models, and MAPK/ERK signalling in ID8 and OVE4 models; metabolic differences, such as reduced glycolysis-associated expression in several engineered ID8 subclones; and relevant functional properties, including differences in EMT activation, PD-L1 and MHC class I expression, and predicted chemosensitivity. Among tumour samples, we observe increased variability and stromal content among intrabursal tumours. Finally, we predict differences in the microenvironment of ID8 models engineered with clinically relevant mutations. We anticipate that this work will serve as a valuable resource, providing new insight to help select models for specific experimental objectives.

Discovery and development of botanical natural products and their analogues as therapeutics for ovarian cancer

Covering: 2015 through the end of July 2022Ovarian cancer is one of the most common cancers affecting the female reproductive organs and has the highest mortality rate among gynecological cancers. Although botanical drugs and their derivatives, namely members of the taxane and camptothecin families, represent significant therapeutics currently available for the treatment of ovarian cancer, new drugs that have alternative mechanisms of action are still needed to combat the disease. For this reason, many efforts to identify additional novel compounds from botanical sources, along with the further development of existing therapeutics, have continued to appear in the literature. This review is designed to serve as a comprehensive look at both the currently available small-molecule therapeutic options and the recently reported botanically-derived natural products currently being studied and developed as potential future therapeutics that could one day be used against ovarian cancer. Specifically, key properties, structural features, and biological data are highlighted that are important for the successful development of potential agents. Recently reported examples are specifically discussed in the context of "drug discovery attributes," including the presence of structure-activity relationship, mechanism of action, toxicity, and pharmacokinetic studies, to help indicate the potential for future development and to highlight where these compounds currently exist in the development process. The lessons learned from both the successful development of the taxanes and camptothecins, as well as the strategies currently being employed for new drug development, are expected to ultimately help guide the future development of botanical natural products for ovarian cancer.

Versican secreted by the ovary links ovulation and migration in fallopian tube derived serous cancer

High grade serous ovarian cancers (HGSOC) predominantly arise in the fallopian tube epithelium (FTE) and colonize the ovary first, before further metastasis to the peritoneum. Ovarian cancer risk is directly related to the number of ovulations, suggesting that the ovary may secrete specific factors that act as chemoattractants for fallopian tube derived tumor cells during ovulation. We found that 3D ovarian organ culture produced a secreted factor that enhanced the migration of FTE non-tumorigenic cells as well as cells harboring specific pathway modifications commonly found in high grade serous cancers. Through size fractionation and a small molecule inhibitors screen, the secreted protein was determined to be 50-100kDa in size and acted through the Epidermal Growth Factor Receptor (EGFR). To correlate the candidates with ovulation, the PREDICT organ-on-chip system was optimized to support ovulation in a perfused microfluidic platform. Versican was found in the correct molecular weight range, contained EGF-like domains, and correlated with ovulation in the PREDICT system. Exogenous versican increased migration, invasion, and enhanced adhesion of both murine and human FTE cells to the ovary in an EGFR-dependent manner. The identification of a protein secreted during ovulation that impacts the ability of FTE cells to colonize the ovary provides new insights into the development of strategies for limiting primary ovarian metastasis.

The Tumor Immune Profile of Murine Ovarian Cancer Models: An Essential Tool For Ovarian Cancer Immunotherapy Research

Epithelial ovarian cancer (EOC) is the most lethal gynecologic cancer with an imperative need for new treatments. Immunotherapy has had marked success in some cancer types; however, clinical trials studying the efficacy of immune checkpoint inhibitors for the treatment of EOC benefited less than 15% of patients. Given that EOC develops from multiple tissues in the reproductive system and metastasizes widely throughout the peritoneal cavity, responses to immunotherapy are likely hindered by heterogeneous tumor microenvironments (TME) containing a variety of immune profiles. To fully characterize and compare syngeneic model systems that may reflect this diversity, we determined the immunogenicity of six ovarian tumor models in vivo, the T and myeloid profile of orthotopic tumors and the immune composition and cytokine profile of ascites, by single-cell RNA sequencing, flow cytometry and IHC. The selected models reflect the different cellular origins of EOC (ovarian and fallopian tube epithelium) and harbor mutations relevant to human disease, including Tp53 mutation, PTEN suppression, and constitutive KRAS activation. ID8-p53-/- and ID8-C3 tumors were most highly infiltrated by T cells, whereas STOSE and MOE-PTEN/KRAS tumors were primarily infiltrated by tumor associated macrophages and were unique in MHC class I and II expression. MOE-PTEN/KRAS tumors were capable of forming T cell clusters. This panel of well-defined murine EOC models reflects some of the heterogeneity found in human disease and can serve as a valuable resource for studies that aim to test immunotherapies, explore the mechanisms of immune response to therapy, and guide selection of treatments for patient populations.

In Vivo and Ex Vivo Analysis of Omental Adhesion in Ovarian Cancer

In vivo and ex vivo analyses of omental adhesion in ovarian cancer (OvCa) are necessary to understand the dynamics of OvCa metastasis. Here we describe methods to analyze OvCa omental adhesion, including in vivo and ex vivo fluorescent imaging, advanced microscopy, and histological techniques. The use of fluorescently tagged OvCa cells allows for omental tumor visualization and quantification in adhesion and tumor studies. Additionally, advanced microscopy modalities allow for visualization and multiplexed analysis of OvCa omental adhesion. Second harmonic generation microscopy permits the visualization and analysis of omental collagen, specifically the tumor-associated collagen signature that forms as the tumor progresses. Scanning electron microscopy is used for the observation of microscopic details between OvCa cells and the omentum, such as tunneling nanotubes or microvilli. Histological methods are used to investigate several intratumoral properties including visualizing tumor structure using hematoxylin and eosin stain; quantifying collagen with Masson's trichrome stain; analyzing collagen structure with a collagen hybridizing peptide; and identifying a number of markers including, but not limited to proliferation, immune cell types, adhesion molecules, and fibroblasts with immunohistochemistry. Both the in vivo and ex vivo imaging modalities and subsequent analysis can provide insight into the interaction of metastasizing OvCa cells and the omentum.

Fallopian Tube-Derived Tumor Cells Induce Testosterone Secretion from the Ovary, Increasing Epithelial Proliferation and Invasion

The fallopian tube epithelium is the site of origin for a majority of high grade serous ovarian carcinomas (HGSOC). The chemical communication between the fallopian tube and the ovary in the development of HGSOC from the fallopian tube is of interest since the fimbriated ends in proximity of the ovary harbor serous tubal intraepithelial carcinoma (STICs). Epidemiological data indicates that androgens play a role in ovarian carcinogenesis; however, the oncogenic impact of androgen exposure on the fallopian tube, or tubal neoplastic precursor lesions, has yet to be explored. In this report, imaging mass spectrometry identified that testosterone is produced by the ovary when exposed to tumorigenic fallopian tube derived PTEN deficient cells. Androgen exposure increased cellular viability, proliferation, and invasion of murine cell models of healthy fallopian tube epithelium and PAX2 deficient models of the preneoplastic secretory cell outgrowths (SCOUTs). Proliferation and invasion induced by androgen was reversed by co-treatment with androgen receptor (AR) antagonist, bicalutamide. Furthermore, ablation of phosphorylated ERK reversed proliferation, but not invasion. Investigation of two hyperandrogenic rodent models of polycystic ovarian syndrome revealed that peripheral administration of androgens does not induce fallopian proliferation in vivo. These data suggest that tumorigenic lesions in the fallopian tube may induce an androgenic microenvironment proximal to the ovary, which may in turn promote proliferation of the fallopian tube epithelium and preneoplastic lesions.

Silencing PTEN in the fallopian tube promotes enrichment of cancer stem cell-like function through loss of PAX2

High-grade serous ovarian cancer (HGSOC) is the most lethal gynecological malignancy that is primarily detected at the metastatic stage. Most HGSOC originates from the fallopian tube epithelium (FTE) and metastasizes to the ovary before invading the peritoneum; therefore, it is crucial to study disease initiation and progression using FTE-derived models. We previously demonstrated that loss of PTEN from the FTE leads to ovarian cancer. In the present study, loss of PTEN in FTE led to the enrichment of cancer stem cell markers such as LGR5, WNT4, ALDH1, CD44. Interestingly, loss of the transcription factor PAX2, which is a common and early alteration in HGSOC, played a pivotal role in the expression of cancer stem-like cells (CSC) markers and cell function. In addition, loss of PTEN led to the generation of two distinct subpopulations of cells with different CSC marker expression, tumorigenicity, and chemoresistance profiles. Taken together, these data suggest that loss of PTEN induces reprogramming of the FTE cells into a more stem-like phenotype due to loss of PAX2 and provides a model to study early events during the FTE-driven ovarian cancer tumor formation.

Cellular models of development of ovarian high-grade serous carcinoma: A review of cell of origin and mechanisms of carcinogenesis

High-grade serous carcinoma (HGSC) is the most common and malignant histological type of epithelial ovarian cancer, the origin of which remains controversial. Currently, the secretory epithelial cells of the fallopian tube are regarded as the main origin and the ovarian surface epithelial cells as a minor origin. In tubal epithelium, these cells acquire TP53 mutations and expand to a morphologically normal 'p53 signature' lesion, transform to serous tubal intraepithelial carcinoma and metastasize to the ovaries and peritoneum where they develop into HGSC. This shifting paradigm of the main cell of origin has revolutionarily changed the focus of HGSC research. Various cell lines have been derived from the two cellular origins by acquiring immortalization via overexpression of hTERT plus disruption of TP53 and the CDK4/RB pathway. Malignant transformation was achieved by adding canonical driver mutations (such as gain of CCNE1) revealed by The Cancer Genome Atlas or by noncanonical gain of YAP and miR181a. Alternatively, because of the extreme chromosomal instability, spontaneous transformation can be achieved by long passage of murine immortalized cells, whereas in humans, it requires ovulatory follicular fluid, containing regenerating growth factors to facilitate spontaneous transformation. These artificially and spontaneously transformed cell systems in both humans and mice have been widely used to discover carcinogens, oncogenic pathways and malignant behaviours in the development of HGSC. Here, we review the origin, aetiology and carcinogenic mechanism of HGSC and comprehensively summarize the cell models used to study this fatal cancer having multiple cells of origin and overt genomic instability.

Paraben exposure alters cell cycle progression and survival of spontaneously immortalized secretory murine oviductal epithelial (MOE) cells

The mammalian oviduct is a central organ for female reproduction as it is the site of fertilization and it actively transports the embryo to the uterus. The oviduct is responsive to ovarian steroids and thus, it is a potential target of endocrine disrupting chemicals. Parabens are antimicrobial compounds that are prevalently found in daily-used products. However, recent studies suggest that some parabens can impact female reproductive health. Yet, their effects on the oviduct are unknown. Here, we hypothesized that in vitro exposure of immortalized murine oviductal secretory epithelial (MOE) cells to methylparaben or propylparaben will result in disrupted cell cycle progression and increased cell death by dysregulation of molecular mechanisms that involve the cell cycle and apoptosis. Thus, we examined the effects of exposure to parabens on cell proliferation, cell cycle progression by flow cytometry, and mRNA levels of major cell cycle regulators and apoptotic factors, in MOE cells. Protein levels of estrogen and progesterone receptors were also quantified. Differences between treatments and controls were analyzed by linear mixed model followed by Dunnett post-hoc tests. The results indicate that methylparaben and propylparaben selectively reduce MOE cellular proliferation and colony numbers, compared to controls. Additionally, paraben exposure selectively dysregulates the progression through the cell cycle and decreases the levels of cell cycle regulators, compared to controls. Last, paraben selectively alters the levels of progesterone receptor. Overall, these findings suggest that parabens can affect mouse oviductal secretory epithelial cell proliferation and survival.

Early embryo-maternal communication in the oviduct: A review

An intact embryo-maternal communication is critical for the establishment of a successful pregnancy. To date, a huge number of studies have been performed describing the complex process of embryo-maternal signaling within the uterus. However, recent studies indicate that the early embryo communicates with the oviductal cells shortly after fertilizationand that this is important for the successful establishment of pregnancy. Only if the early embryo is capable to signal the mother within a precise timeframe and to garner a response, will the embryo be able to survive and reach the uterus. This review will give an overview of all the experimental designs which have investigated embryo-maternal interaction in the oviduct. In addition to that, it will provide a comprehensive analysis of the findings to date elucidating the morphological and molecular changes in the oviduct which are induced by the presence of the early embryo highlighting how the tubal responses affect embryo development and survival.

Fallopian tube initiation of high grade serous ovarian cancer and ovarian metastasis: Mechanisms and therapeutic implications

Ovarian cancer is the most lethal gynecologic malignancy and the fifth leading cause of cancer-related death in women. Although outcomes have improved in recent years, there remains an unmet clinical need to understand the early pathogenesis of ovarian cancer in order to identify new diagnostic approaches and agents of chemoprevention and chemotherapy. While high grade serous ovarian cancer (HGSOC), the most abundant histotype, was initially thought to arise from the ovarian surface epithelium, there is an increasing body of evidence suggesting that HGSOC originates in the fallopian tube. With this new understanding of cell of origin, understanding of disease development requires analysis with a novel perspective. Currently, factors that drive the initiation and migration of dysplastic tubal epithelial cells from the fallopian tube to the ovary are not yet fully defined. These factors include common mutations to fallopian tube epithelial cells, as well as factors originating from both the fallopian tube and ovary which are capable of inducing transformation and dissemination in said cells. Here, we review these changes, their causative agents, and various potential means of intervention.

Exposure of the extracellular matrix and colonization of the ovary in metastasis of fallopian-tube-derived cancer

High-grade serous ovarian cancer (HGSOC) can originate in the fallopian tube epithelium (FTE), but the role of the ovary in these tumors is unclear. Tumorigenic murine oviductal epithelial (MOE) cells allografted in the ovarian bursa resulted in aggressive tumors that spread throughout the peritoneum whereas intraperitoneal xenografting the same number of cells did not form tumors, indicating that colonization of the ovary may play a role in metastasis. Physical tearing of the ovarian surface to mimic rupture of the ovary during ovulation (independent of hormonal changes) resulted in more MOE and HGSOC cells adhering to the ovary compared with intact ovaries. More MOE cells also adhered to three-dimensional (3D) collagen and primary ovarian stromal cells than to ovarian surface epithelia, indicating that FTE cells adhered to the extracellular matrix exposed during ovulation. However, plating cells on 3D collagen reduced the viability of normal FTE but not cancer cells. Mutation of p53 (R273H or R248W) and activation of Kirsten Rat Sarcoma Viral Oncogene Homolog (KRAS) (G12V) did not increase the viability of MOE cells on 3D collagen. In contrast, loss of phosphatase and tensin homolog (PTEN) allowed MOE cells to retain normal viability on 3D collagen. Loss of PTEN activated AKT and RAC1/c-jun N-terminal kinase signaling that each contributed to the increased viability, invasion and attachment in the collagen rich ovarian microenvironment. These results show that loss of PTEN activates multiple pathways that together enhance colonization of the ovary due to access to 3D collagen, which is a critical organ in the colonization of FTE-derived HGSOC.

Proteomic analysis reveals a role for PAX8 in peritoneal colonization of high grade serous ovarian cancer that can be targeted with micelle encapsulated thiostrepton

High grade serous ovarian cancer (HGSOC) is the fifth leading cause of cancer deaths among women yet effective targeted therapies against this disease are limited. The heterogeneity of HGSOC, including few shared oncogenic drivers and origination from both the fallopian tube epithelium (FTE) and ovarian surface epithelium (OSE), has hampered development of targeted drug therapies. PAX8 is a lineage-specific transcription factor expressed in the FTE that is also ubiquitously expressed in HGSOC where it is an important driver of proliferation, migration, and cell survival. PAX8 is not normally expressed in the OSE, but it is turned on after malignant transformation. In this study, we use proteomic and transcriptomic analysis to examine the role of PAX8 leading to increased migratory capabilities in a human ovarian cancer model, as well as in tumor models derived from the OSE and FTE. We find that PAX8 is a master regulator of migration with unique downstream transcriptional targets that are dependent on the cell’s site of origin. Importantly, we show that targeting PAX8, either through CRISPR genomic alteration or through drug treatment with micelle encapsulated thiostrepton, leads to a reduction in tumor burden. These findings suggest PAX8 is a unifying protein driving metastasis in ovarian tumors that could be developed as an effective drug target to treat HGSOC derived from both the OSE and FTE.

Host CYP27A1 expression is essential for ovarian cancer progression

There is an urgent need for more effective strategies to treat ovarian cancer. Elevated cholesterol levels are associated with a decreased progression-free survival time (PFS) while statins are protective. 27-Hydroxycholesterol (27HC), a primary metabolite of cholesterol, has been shown to modulate the activities of the estrogen receptors (ERs) and liver x receptors (LXRs) providing a potential mechanistic link between cholesterol and ovarian cancer progression. We found that high expression of CYP27A1, the enzyme responsible for the synthesis of 27HC, was associated with decreased PFS, while high expression of CYP7B1, responsible for 27HC catabolism, was associated with increased PFS. However, 27HC decreased the cellular proliferation of various ovarian cancer cell lines in an LXR-dependent manner. Intriguingly, ID8 grafts were unable to effectively establish in CYP27A1-/- mice, indicating involvement of the host environment. Tumors from mice treated with 27HC had altered myeloid cell composition, and cells from the marrow stem cell lineage were found to be responsible for the effects in CYP27A1-/- mice. While inhibition of CYP27A1 or immune checkpoint did not significantly alter tumor size, their combination did, thereby highlighting this axis as a therapeutic target.

Loss of PTEN in Fallopian Tube Epithelium Results in Multicellular Tumor Spheroid Formation and Metastasis to the Ovary

High-grade serous ovarian cancer (HGSOC) can originate in the fallopian tube and then spread to the ovary. Our objective was to evaluate the role of multicellular tumor spheroids (MTS) in ovarian metastasis. By testing a panel of murine oviductal epithelial (MOE) cells with genetic alterations mimicking those seen in HGSOC, we found that loss of PTEN allowed MTS formation under ultra-low adhesion conditions. Confirming these results in vivo, MTS-like structures were observed in the oviducts of PAX8^Cre/+ PTEN^flox/flox mice. MOE PTEN^shRNA cells could incorporate up to 25% wild type cells into MTS, while higher percentages of wild type cells resulted in a loss of MTS formation. MTS formation allowed MOE PTEN^shRNA cells to survive better under ultra-low adhesion conditions than control cells. MTS also attached to the ovarian stroma, as would be exposed during ovulation. Interestingly, MTS more robustly cleared monolayers of murine ovarian surface epithelia than murine ovarian fibroblasts. When xenografted into the ovarian bursa, OVCAR8 MTS were able to form tumors in the ovary at a similar rate as an equal number of OVCAR8 cells grown on traditional cell culture plastic. In conclusion, loss of a single gene (PTEN) allows the fallopian tube epithelia to form MTS, which survive better under ultra-low adhesion conditions, attach to the extracellular matrix exposed during ovulation, and colonize the ovary. These results suggest that MTS may contribute to seeding of the ovary in HGSOC patients.

Imaging Mass Spectrometry Reveals Crosstalk between the Fallopian Tube and the Ovary that Drives Primary Metastasis of Ovarian Cancer

High grade serous ovarian cancer (HGSOC) is the fifth leading cause of cancer deaths among women. New evidence suggests that HGSOC arises in the fallopian tube and then colonizes the ovary before spreading into the peritoneal space. Therefore, due to the proximity of this metastasis, an experimental design was optimized using imaging mass spectrometry to capture the spatial composition of small molecules uniquely expressed when fallopian-tube-derived tumor cells were grown in the microenvironment of the ovary as a model of primary metastasis. The observed mass-to-charge ratios (m/z's) that were induced specifically in coculture represent small molecules that may contribute to the metastasis of HGSOC selectively to the ovary. Human fallopian tube epithelial HGSOC and tumorigenic murine oviductal epithelial cells, but not normal cell types, repeatedly induced a signal from the ovary at m/z 170. This signal was identified as norepinephrine, which was confirmed to stimulate invasion of ovarian cancer cells lacking wild-type p53. These molecules may reveal pathways that contribute to metastasis and biological targets for therapeutic intervention to block ovarian metastasis of fallopian-tube-derived HGSOC. The developed mass spectrometry method can be adapted to other mammalian-based model systems for investigation of untargeted metabolomics that facilitate metastasis.

UnPAXing the Divergent Roles of PAX2 and PAX8 in High-Grade Serous Ovarian Cancer

High-grade serous ovarian cancer is a deadly disease that can originate from the fallopian tube or the ovarian surface epithelium. The PAX (paired box) genes PAX2 and PAX8 are lineage-specific transcription factors required during development of the fallopian tube but not in the development of the ovary. PAX2 expression is lost early in serous cancer progression, while PAX8 is expressed ubiquitously. These proteins are implicated in migration, invasion, proliferation, cell survival, stem cell maintenance, and tumor growth. Hence, targeting PAX2 and PAX8 represents a promising drug strategy that could inhibit these pro-tumorigenic effects. In this review, we examine the implications of PAX2 and PAX8 expression in the cell of origin of serous cancer and their potential efficacy as drug targets by summarizing their role in the molecular pathogenesis of ovarian cancer.

Aging Increases Susceptibility to Ovarian Cancer Metastasis in Murine Allograft Models and Alters Immune Composition of Peritoneal Adipose Tissue

Ovarian cancer, the most deadly gynecological malignancy in U.S. women, metastasizes uniquely, spreading through the peritoneal cavity and often generating widespread metastatic sites before diagnosis. The vast majority of ovarian cancer cases occur in women over 40 and the median age at diagnosis is 63. Additionally, elderly women receive poorer prognoses when diagnosed with ovarian cancer. Despite age being a significant risk factor for the development of this cancer, there are little published data which address the impact of aging on ovarian cancer metastasis. Here we report that the aged host is more susceptible to metastatic success using two murine syngeneic allograft models of ovarian cancer metastasis. This age-related increase in metastatic tumor burden corresponds with an increase in tumor infiltrating lymphocytes (TILs) in tumor-bearing mice and alteration of B cell-related pathways in gonadal adipose tissue. Based on this work, further studies elucidating the status of B cell TILs in mouse models of metastasis and human tumors in the context of aging are warranted.

Cadherin-6 type 2, K-cadherin (CDH6) is regulated by mutant p53 in the fallopian tube but is not expressed in the ovarian surface

High-grade serous ovarian cancer (HGSOC) is the most lethal gynecological malignancy and may arise in either the fallopian tube epithelium (FTE) or ovarian surface epithelium (OSE). A mutation in p53 is reported in 96% of HGSOC, most frequently at R273 and R248. The goal of this study was to identify specific gene targets in the FTE that are altered by mutant p53, but not in the OSE. Gene analysis revealed that both R273 and R248 mutant p53 reduces CDH6 expression in the oviduct, but CDH6 was not detected in murine OSE cells. p53^R273H induced SLUG and FOXM1 while p53^R248W did not induce SLUG and only modestly increased FOXM1, which correlated with less migration as compared to p53^R273H. An oviduct specific PAX8^Cre/+/p53^R270H/+ mouse model was created and confirmed that in vivo mutant p53 repressed CDH6 but was not sufficient to stabilize p53 expression alone. Overexpression of mutant p53 in the p53 null OVCAR5 cells decreased CDH6 levels indicating this was a gain-of-function. SLUG knockdown in murine oviductal cells with p53^R273H restored CDH6 repression and a ChIP analysis revealed direct binding of mutant p53 on the CDH6 promoter. NSC59984, a small molecule that degrades mutant p53^R273H, rescued CDH6 expression. In summary, CDH6 is expressed in the oviduct, but not the ovary, and is repressed by mutant p53. CDH6 expression with further validations may aide in establishing markers that inform upon the cell of origin of high grade serous tumors.

PTEN loss in the fallopian tube induces hyperplasia and ovarian tumor formation

The signaling events involved in the onset of ovarian cancer from the fallopian tube epithelium (FTE) are crucial for early detection and treatment of the disease, but they remain poorly defined. Conditional homozygous knockout of PTEN mediated by PAX8-cre recombinase was sufficient to drive endometrioid and serous borderline ovarian carcinoma, providing the first model of FTE-derived borderline tumors. In addition, heterozygous PTEN deletion in the FTE resulted in hyperplasia, providing a model to study early events of human ovarian pathogenesis. To uncover the mechanism underlying the invasion of cancerous oviductal cells to the ovary, PTEN-deficient murine oviductal cells were developed and tagged with green fluorescent protein. Loss of PTEN increased cell migration, invasion, and upregulated WNT4, a key regulator of Müllerian duct development during embryogenesis. Further investigation revealed that WNT4 was required for increased migration and colonization of the ovary by PTEN-deficient oviductal cells in a β-catenin independent manner. Human tumor microarrays and ovarian cancer cells lines confirmed WNT4 expression in cancer and its role in migration. Together, these findings provide a novel model to study the mechanism of fallopian tube tumor initiation and invasion to the ovary mediated by loss of PTEN, which may help to define early events of human ovarian carcinogenesis.

Methods for the visualization and analysis of extracellular matrix protein structure and degradation

This chapter highlights methods for visualization and analysis of extracellular matrix (ECM) proteins, with particular emphasis on collagen type I, the most abundant protein in mammals. Protocols described range from advanced imaging of complex in vivo matrices to simple biochemical analysis of individual ECM proteins. The first section of this chapter describes common methods to image ECM components and includes protocols for second harmonic generation, scanning electron microscopy, and several histological methods of ECM localization and degradation analysis, including immunohistochemistry, Trichrome staining, and in situ zymography. The second section of this chapter details both a common transwell invasion assay and a novel live imaging method to investigate cellular behavior with respect to collagen and other ECM proteins of interest. The final section consists of common electrophoresis-based biochemical methods that are used in analysis of ECM proteins. Use of the methods described herein will enable researchers to gain a greater understanding of the role of ECM structure and degradation in development and matrix-related diseases such as cancer and connective tissue disorders.

Loss of PAX8 in high-grade serous ovarian cancer reduces cell survival despite unique modes of action in the fallopian tube and ovarian surface epithelium

High-grade serous carcinoma (HGSC) is the most common and lethal form of ovarian cancer. PAX8 is a transcription factor expressed in fallopian tube epithelial cells and in 80–96% of HGSC tumors. The ovarian surface epithelium (OSE) only acquires PAX8 expression after malignant transformation. In this study, forced PAX8 expression in OSE cells increased proliferation and migration through upregulation of EMT factors such as N-cadherin and Fibronectin. OSE cells expressing PAX8 also had an increase in the FOXM1 pathway, but PAX8 alone was not sufficient to drive tumorigenesis. PAX8 knockdown in the oviductal epithelium cells did not decrease expression of the FOXM1 pathway and induced only a slight decrease in cell proliferation. No changes in migration, cell cycle, or apoptosis were detected after PAX8 knockdown in oviductal cells. Finally, PAX8 knockdown in HGSC cell lines resulted in increased apoptosis and decreased FOXM1 levels. The results presented here suggest that PAX8 has a cell specific role in governing proliferation and migration in nontransformed ovarian surface epithelium cells compared to the oviductal cells, but its reduction in serous cancer cell lines provides a common mechanism for reducing cell survival.

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.

(+)-Strebloside-Induced Cytotoxicity in Ovarian Cancer Cells Is Mediated through Cardiac Glycoside Signaling Networks

(+)-Strebloside, a cardiac glycoside isolated from the stem bark of Streblus asper collected in Vietnam, has shown some potential for further investigation as an antineoplastic agent. A mechanistic study using an in vitro assay and molecular docking analysis indicated that (+)-strebloside binds and inhibits Na+/K+-ATPase in a similar manner to digitoxin. Inhibition of growth of different high-grade serous ovarian cancer cells including OVCAR3, OVSAHO, Kuramochi, OVCAR4, OVCAR5, and OVCAR8 resulted from treatment with (+)-strebloside. Furthermore, this compound blocked cell cycle progression at the G2 phase and induced PARP cleavage, indicating apoptosis activation in OVCAR3 cells. (+)-Strebloside potently inhibited mutant p53 expression through the induction of ERK pathways and inhibited NF-κB activity in human ovarian cancer cells. However, in spite of its antitumor potential, the overall biological activity of (+)-strebloside must be regarded as being typical of better-known cardiac glycosides such as digoxin and ouabain. Further chemical alteration of cardiac glycosides might help to reduce negative side effects while increasing cancer cell cytotoxicity.

Activin A stimulates migration of the fallopian tube epithelium, an origin of high-grade serous ovarian cancer, through non-canonical signaling

Factors that stimulate the migration of fallopian tube epithelial (FTE)-derived high-grade serous ovarian cancer (HGSOC) to the ovary are poorly elucidated. This study characterized the effect of the ovarian hormone, activin A, on normal FTE and HGSOC. Activin A and TGFβ1 induced an epithelial-to-mesenchymal transition in murine oviductal epithelial (MOE) cells, but only activin A increased migration. The migratory effect of activin A was independent of Smad2/3 and required phospho-AKT, phospho-ERK, and Rac1. Exogenous activin A stimulated migration of the HGSOC cell line OVCAR3 through a similar mechanism. Activin A signaling inhibitors, SB431542 and follistatin, reduced migration in OVCAR4 cells, which expressed activin A subunits (encoded by INHBA). Murine superovulation increased phospho-Smad2/3 immunostaining in the FTE. In Oncomine, transcripts for the activin A receptors (ACVR1B and ACVR2A) were higher in serous tumors relative to the normal ovary, while inhibitors of activin A signaling (INHA and TGFB3) were lower. High expression of both INHBA and ACVR2A, but not TGFβ receptors or co-receptors, was associated with shorter disease-free survival in serous cancer patients. These results suggest activin A stimulates migration of FTE-derived tumors to the ovary.

PAX2 function, regulation and targeting in fallopian tube-derived high-grade serous ovarian cancer

The fallopian tube epithelium (FTE) is one of the progenitor populations for high-grade serous ovarian cancer (HGSC). Loss of PAX2 is the earliest known molecular aberration in the FTE occurring in serous carcinogenesis followed by a mutation in p53. Pathological studies report consistent loss of PAX2 in benign lesions as well as serous tumors. In the current study, the combined loss of PAX2 and expression of the R273H p53 mutant protein in murine oviductal epithelial (MOE) cells enhanced proliferation and growth in soft agar in vitro but was insufficient to drive tumorigenesis in vivo. A serially passaged model was generated to investigate the role of aging, but was also insufficient to drive tumorigenesis. These models recapitulate early benign lesions and suggest that a latency period exists between loss of PAX2, p53 mutation and tumor formation. Stathmin and fut8 were identified as downstream targets regulated by loss of PAX2 and mutation of p53 in MOE cells. Re-expression of PAX2 in PAX2-null human HGSC cells reduced cell survival via apoptosis. Phosphatase and tensin homolog (PTEN)^shRNA negatively regulated PAX2 expression and stable re-expression of PAX2 in MOE:PTEN^shRNA cells significantly reduced proliferation and peritoneal tumor formation in athymic nude mice. PAX2 was determined to be a direct transcriptional target that was activated by wild-type p53, whereas mutant p53 inhibited PAX2 transcription in MOE cells. A small molecule screen using the proximal PAX2 promoter driving luciferase identified four small molecules that were able to enhance PAX2 mRNA expression in MOE cells. PAX2 re-expression in HGSC cells and PTEN-deficient oviductal tumors may have the potential to induce apoptosis. In summary, mutant p53 and PTEN loss negatively regulated PAX2 and PAX2 re-expression in HGSC cells induced cell death.