The origin of ovarian carcinomas: A developmental view

Uncloaking the Fimbria Ovarica: Histologic Recognition of an Elusive Anatomic Structure

A portion of the fimbriated end of the fallopian tube known as the fimbria ovarica extends along the lateral edge of the mesosalpinx to the ovary to which it is attached at its lateral pole. Seventy-four examples of fimbrial plicae that were attached to the ovary or broad ligament and lacked features of adhesions were studied. The fimbrio-ovarian attachments were characterized by one or more of the following: continuity between the tubal epithelium and either the ovarian surface epithelium, peritoneum, or both, in 51 cases; direct continuity of the ovarian stroma into the stroma of the fimbria ovarica in 42 cases; and direct insertion of plicae into the ovarian surface or ovarian stroma in 18 cases. In 21 cases, there was a direct attachment of plicae to the broad ligament close to the ovary. The mean size of the fimbria ovarica was 6.6 mm. The plicae were lined by normal tubal-type epithelium. The plical morphology was typically abnormal displaying one or more of the following features: short and blunted in 24 (32%), thickened in 18 (24%), elongated in 14 (19%), fusion in 13 (18%), edema in 13 (18%), and fibrosis in 11 (15%). Also noted were a mesothelial component in 69 cases (93%), the tubal-peritoneal junction in 53 cases (72%), transitional cell metaplasia/Walthard cell nests in 11 cases (15%), and foci resembling incipient fimbrial adenofibroma in 7 cases (9%). An understanding of the microanatomy and histology of the fimbria ovarica has important implications, particularly as: (a) portions may be left behind after prophylactic salpingectomy, providing a nidus for future development of high grade serous carcinoma (HGSC); (b) it constitutes an anatomic connection that may facilitate the spread of HGSC to the ovary, and (c) epithelial junctions are hotspots for carcinogenesis, and stem cells arising in such regions may be a source of HGSCs. In addition, understanding the fimbria ovarica has implications for the pathogenesis of ovarian surface epithelial inclusions, endosalpingiosis, and certain types of infertility. Its potential role as a site of origin of extrauterine HGSC, which typically arises in the fimbriae as serous tubal intraepithelial carcinoma, remains to be investigated.

Exploring the characteristics of immortalized human ovarian surface epithelial cell lines

The origins of epithelial ovarian cancer (EOC) have long been debated, with proposed sources including ovarian surface epithelial (OSE) cells, secondary Müllerian tract structures, or fallopian tube epithelium. Despite being the second most common gynecological cancer and a leading cause of death in the United States, in vitro cell models mimicking normal ovarian epithelial cells and their malignant counterparts are lacking. To address this gap, we established immortalized human OSE (IHOSE) cell lines that demonstrate stable in vitro growth without malignant properties. IHOSE cell lines were unique cell lines by analyzing short tandem repeat (STR) profiling. In addition, the epithelial characteristics were confirmed by cytokeratin 7 and cytokeratin 18 marker expression. IHOSE cell lines were subjected to Opal multiplex immunohistochemistry (IHC) analysis, which established four distinct subtypes based on marker dominance. These studies offer the most basic but essential cellular characterization information for IHOSE cell lines, providing critical data that can guide the selection of cells when inducing normal controls or disease models.

Primary Retroperitoneal Carcinomas: New Insights into Pathogenesis and Clinical Management in Comparison with Ovarian Carcinomas and Carcinoma of Unknown Primary

Primary retroperitoneal carcinomas are very rare tumors. Their pathogenesis remains unknown but may be associated with that of ovarian carcinomas, considering the similarity in morphology and gender preference. Although metaplasia of coelomic epithelium is the most widely accepted theory, the pathogenesis of retroperitoneal carcinomas may differ by histologic subtype, like ovarian carcinomas. Mucinous carcinoma, which develops in both women and men, may originate in both primordial germ cells and Walthard cell nests that may be derived from the fallopian tube. Serous carcinomas may be associated with endosalpingiosis, the presence of fallopian tube-like epithelium outside the fallopian tube, and a remnant Müllerian tract. Endometrioid and clear cell carcinomas appear to be associated with extraovarian endometriosis. Additionally, both carcinomas in the retroperitoneal lymph nodes may be metastatic diseases from endometrial and/or renal cell cancer that regress spontaneously (carcinoma of unknown primary). Retroperitoneal carcinomas are difficult to diagnose, as they have no characteristic symptoms and signs. Surgery is the cornerstone of treatment, but the necessity of chemotherapy may depend on histological subtype. Further studies are necessary, in particular studies on endosalpingiosis, as endosalpingiosis is a poorly understood condition, although it is associated with the development of both serous and mucinous carcinomas.

Proliferation of the Fallopian Tube Fimbriae and Cortical Inclusion Cysts: Effects of the Menstrual Cycle and the Levonorgestrel Intrauterine Contraceptive System

BACKGROUND

The objectives of this study were (i) to explore whether differences in cell proliferation may help explain why most high-grade serous ovarian cancers (HGSOC) arise in the fallopian tube fimbriae (FTF) rather than in ovarian cortical inclusion cysts (CIC); (ii) to compare premenopausal and postmenopausal FTF proliferation as a reason why the age incidence of HGSOC increases at a slower rate after menopause; and (iii) to compare FTF proliferation in cycling women and women using the levonorgestrel intrauterine contraceptive system (Lng-IUS) to see whether proliferation on the Lng-IUS was lower.

METHODS

We studied 60 women undergoing a salpingo-oophorectomy. We used Ki67, paired-box gene 8 (PAX8, Müllerian marker), and calretinin (mesothelial marker) to study FTF and CIC proliferation.

RESULTS

FTF Ki67%+ was greater in the follicular than in the luteal phase (4.9% vs. 1.5%; P = 0.003); postmenopausal Ki67%+ was 1.7%. Ki67%+ in PAX8 negative (PAX8-) CICs was extremely low. Proliferation in PAX8+ CICs did not vary by menstrual phase or menopausal status. Follicular Ki67%+ was 2.6-fold higher in FTF than PAX8+ CICs. FTF Ki67%+ from 10 women using the Lng-IUS was not lower than in cycling women.

CONCLUSIONS

Overall FTF Ki67%+ is greater than overall CIC Ki67%+. Overall FTF Ki67%+ in postmenopausal women is lower than in premenopausal women. The Lng-IUS is not associated with lower FTF Ki67%+.

IMPACT

Ki67%+ provides an explanation of the preponderance of FTF-derived HGSOCs, and of the slower increase of HGSOCs after menopause. The Lng-IUS may not be associated with a protective effect against HGSOCs.

Association Between Benign Ovarian Tumors and Ovarian Cancer Risk: A Meta-Analysis of Ten Epidemiological Studies

Background

Epidemiological evidence on the relationship between benign ovarian tumors and ovarian cancer risk has been controversial; therefore, this systematic review and meta-analysis evaluated this association.

Methods

The PubMed and Web of Knowledge databases were searched for eligible studies published up to April 30, 2020. The study-specific risk estimates were pooled using a random-effects model.

Results

Ten articles (two cohorts, seven case-control studies, and one pooled analysis of eight case-control studies) with 10331 ovarian cancer patients were included. Benign ovarian tumors were associated with an increased risk of ovarian cancer (pooled relative risk [RR]=1.39, 95% confidence interval [CI]: 1.01–1.90), with high heterogeneity among studies. The pooled RR was 2.02 (95%CI: 1.32–3.11) for two cohort studies, which was higher than the pooled result of eight case-control studies (pooled RR: 1.15; 95%CI: 0.92–1.44). When stratifying by histological type, the pooled RRs were 1.53 (95% CI: 0.37–6.29) and 3.62 (95%CI: 0.81–16.20) for serous and mucinous tumors, respectively. The pooled RRs were 1.61 (95%CI: 0.65–3.95) and 1.54 (95%CI: 1.29–1.84) for the associations of ovarian cyst with invasive and borderline cancers, respectively.

Conclusions

Benign ovarian tumors were associated with an increased risk of ovarian cancer. Due to the high heterogeneity among the studies and the risks of bias, more studies are warranted to confirm these findings.

USP13 promotes development and metastasis of high-grade serous ovarian carcinoma in a novel mouse model

Epithelial ovarian cancer is the most lethal gynecologic malignancy and one of the most common causes of cancer mortality among women worldwide. Ubiquitin-Specific Peptidase 13 (USP13) gene copy is strongly amplified in human epithelial ovarian cancer, and high USP13 expression is correlated with poor survival outcomes. Yet, its pathological contribution to ovarian tumorigenesis remains unknown. We crossed a conditional Usp13 overexpressing knock-in mouse with a conditional knockout of Trp53 and Pten mouse and generated a novel ovarian cancer genetically engineered mouse model (GEMM), which closely recapitulates the genetic changes driving ovarian cancer in humans. Overexpression of USP13 with deletion of Trp53 and Pten in murine ovarian surface epithelium accelerated ovarian tumorigenesis and led to decreased survival in mice. Notably, USP13 greatly enhanced peritoneal metastasis of ovarian tumors with frequent development of hemorrhagic ascites. The primary and metastatic tumors exhibited morphology and clinical behavior similar to human high-grade serous ovarian cancer. Co-inhibition of USP13 and AKT significantly decreased the viability of the primary murine ovarian cancer cells isolated from the GEMM. USP13 also increased the tumorigenic and metastatic abilities of primary murine ovarian cancer cells in a syngeneic mouse study. These findings suggest a critical role of USP13 in ovarian cancer development and reveal USP13 as a potential therapeutic target for ovarian cancer.

Human Papillomaviruses as Infectious Agents in Gynecological Cancers. Oncogenic Properties of Viral Proteins

Human papillomaviruses (HPVs), which belong to the Papillomaviridae family, constitute a group of small nonenveloped double-stranded DNA viruses. HPV has a small genome that only encodes a few proteins, and it is also responsible for 5% of all human cancers, including cervical, vaginal, vulvar, penile, anal, and oropharyngeal cancers. HPV types may be classified as high- and low-risk genotypes (HR-HPVs and LR-HPVs, respectively) according to their oncogenic potential. HR-HPV 16 and 18 are the most common types worldwide and are the primary types that are responsible for most HPV-related cancers. The activity of the viral E6 and E7 oncoproteins, which interfere with critical cell cycle points such as suppressive tumor protein p53 (p53) and retinoblastoma protein (pRB), is the major contributor to HPV-induced neoplastic initiation and progression of carcinogenesis. In addition, the E5 protein might also play a significant role in tumorigenesis. The role of HPV in the pathogenesis of gynecological cancers is still not fully understood, which indicates a wide spectrum of potential research areas. This review focuses on HPV biology, the distribution of HPVs in gynecological cancers, the properties of viral oncoproteins, and the molecular mechanisms of carcinogenesis.

A Review of Principal Studies on the Development and Treatment of Epithelial Ovarian Cancer in the Laying Hen Gallus gallus

Often referred to as the silent killer, ovarian cancer is the most lethal gynecologic malignancy. This disease rarely shows any physical symptoms until late stages and no known biomarkers are available for early detection. Because ovarian cancer is rarely detected early, the physiology behind the initiation, progression, treatment, and prevention of this disease remains largely unclear. Over the past 2 decades, the laying hen has emerged as a model that naturally develops epithelial ovarian cancer that is both pathologically and histologically similar to that of the human form of the disease. Different molecular signatures found in human ovarian cancer have also been identified in chicken ovarian cancer including increased CA125 and elevated E-cadherin expression, among others. Chemoprevention studies conducted in this model have shown that decreased ovulation and inflammation are associated with decreased incidence of ovarian cancer development. The purpose of this article is to review the major studies performed in laying hen model of ovarian cancer and discuss how these studies shape our current understanding of the pathophysiology, prevention, and treatment of epithelial ovarian cancer.

Most Commonly Mutated Genes in High-Grade Serous Ovarian Carcinoma Are Nonessential for Ovarian Surface Epithelial Stem Cell Transformation

High-grade serous ovarian carcinoma (HGSOC) is the fifth leading cause of cancer-related deaths of women in the United States. Disease-associated mutations have been identified by the Cancer Genome Atlas Research Network. However, aside from mutations in TP53 or the RB1 pathway that are common in HGSOC, the contributions of mutation combinations are unclear. Here, we report CRISPR mutagenesis of 20 putative HGSOC driver genes to identify combinatorial disruptions of genes that transform either ovarian surface epithelium stem cells (OSE-SCs) or non-stem cells (OSE-NSs). Our results support the OSE-SC theory of HGSOC initiation and suggest that most commonly mutated genes in HGSOC have no effect on OSE-SC transformation initiation. Our results indicate that disruption of TP53 and PTEN, combined with RB1 disruption, constitutes a core set of mutations driving efficient transformation in vitro. The combined data may contribute to more accurate modeling of HGSOC development.

Mechanisms of High-Grade Serous Carcinogenesis in the Fallopian Tube and Ovary: Current Hypotheses, Etiologic Factors, and Molecular Alterations

Ovarian high-grade serous carcinomas (HGSCs) are a heterogeneous group of diseases. They include fallopian-tube-epithelium (FTE)-derived and ovarian-surface-epithelium (OSE)-derived tumors. The risk/protective factors suggest that the etiology of HGSCs is multifactorial. Inflammation caused by ovulation and retrograde bleeding may play a major role. HGSCs are among the most genetically altered cancers, and TP53 mutations are ubiquitous. Key driving events other than TP53 mutations include homologous recombination (HR) deficiency, such as BRCA 1/2 dysfunction, and activation of the CCNE1 pathway. HR deficiency and the CCNE1 amplification appear to be mutually exclusive. Intratumor heterogeneity resulting from genomic instability can be observed at the early stage of tumorigenesis. In this review, I discuss current carcinogenic hypotheses, sites of origin, etiologic factors, and molecular alterations of HGSCs.

Morphological basics of ovarian tumor histogenesis

Researches about the origin of epithelial ovarian tumors (EOT) tell about its conception. In particular, the origin of cells from the secondary mullerian system. Also, in the article we examine a new hypothesis that the EOT originates in the epithelium of the fallopian tube (FT) – their contradictoriness and new conception of “precursor escape” which tries to explain the phenomenon of injuries absence of FT by high-grade serous ovarian carcinoma. Carcinogenesis from the FT represents great opportunities for reassessment of clinical data. Also, the article represents the role of stem cells of the surface epithelium of ovaries and FT in EOT carcinogenesis.

Proportional vascularization along the fallopian tubes and ovarian fimbria: assessment by confocal microtomography

Objective

To evaluate and reconstruct three-dimensional images of vascularization along the fallopian tube (FT), as well as to determine its relationship with the ovary and ovarian fimbria, and to quantify the blood vessels along the FT according to its anatomical segments, using confocal microtomography (micro-CT).

Materials and Methods

Nine specimens (six FTs and three FTs with ovaries) were fixed in a solution of 10% formalin for > 24 h at room temperature. Iodine staining was performed by soaking the specimens in 10% Lugol’s solution for 24 h. All specimens were evaluated using micro-CT. A morphometric analysis was performed on the reconstructed images to quantify the vascular distribution along the FT.

Results

In the FTs evaluated, the density of blood vessels was significantly greater in the fimbrial segments than in the isthmic segments (p < 0.05). The ovarian fimbria was clearly identified, demonstrating the important relationship between these vessels and the FT fimbriae.

Conclusion

We believe that the vascularization in the fimbriae is greater than and disproportional that in the other segments of FT, and that the ovarian fimbria plays an important role in the development of that difference.

Both fallopian tube and ovarian surface epithelium are cells-of-origin for high-grade serous ovarian carcinoma

The cell-of-origin of high grade serous ovarian carcinoma (HGSOC) remains controversial, with fallopian tube epithelium (FTE) and ovarian surface epithelium (OSE) both considered candidates. Here, by using genetically engineered mouse models and organoids, we assessed the tumor-forming properties of FTE and OSE harboring the same oncogenic abnormalities. Combined RB family inactivation and Tp53 mutation in Pax8 + FTE caused Serous Tubal Intraepithelial Carcinoma (STIC), which metastasized rapidly to the ovarian surface. These events were recapitulated by orthotopic injection of mutant FTE organoids. Engineering the same genetic lesions into Lgr5 + OSE or OSE-derived organoids also caused metastatic HGSOC, although with longer latency and lower penetrance. FTE- and OSE-derived tumors had distinct transcriptomes, and comparative transcriptomics and genomics suggest that human HGSOC arises from both cell types. Finally, FTE- and OSE-derived organoids exhibited differential chemosensitivity. Our results comport with a dualistic origin for HGSOC and suggest that the cell-of-origin might influence therapeutic response.

Risk of epithelial ovarian cancer among women with benign ovarian tumors: a follow-up study

PURPOSE

The importance of benign ovarian tumors as precursors or risk markers for ovarian cancer is not fully understood. Studies on the association between benign ovarian tumors and ovarian cancer have provided inconclusive results. We examined the overall and histological type-specific risk of ovarian cancer among 158,221 Danish women diagnosed with a benign ovarian tumor during 1978-2016.

METHODS

The study cohort was linked to the Danish Cancer Register to identify all cases of epithelial ovarian cancer, and standardized incidence ratios (SIR) with 95% confidence intervals (CI) were calculated.

RESULTS

After excluding the first year of follow-up, women with benign ovarian tumors did not have an increased risk for overall epithelial ovarian cancer (SIR 1.02; 95% CI 0.93-1.11), as compared with women in the general population. However, we found an increased risk for mucinous ovarian cancer (SIR 2.06; 95% CI 1.67-2.52); both solid and cystic benign ovarian tumors were associated with an increased risk. The risk for mucinous ovarian cancer was increased irrespective of the age at benign ovarian tumors diagnosis and persisted for up to 20 years after the benign ovarian tumor diagnosis. No clear associations for other histological types of ovarian cancer were observed, except for an increased risk for serous ovarian cancer among women diagnosed with benign ovarian tumors at an young age.

CONCLUSIONS

Benign ovarian tumors may be associated with long-term increased risk for mucinous ovarian cancer.

Observations on the origin of ovarian cortical inclusion cysts in women undergoing risk-reducing salpingo-oophorectomy

AIMS

Evidence suggests that up to 70% of high-grade serous ovarian carcinomas (HGSCs) arise potentially from fallopian tube fimbriae, and that many of the remaining cases arise from within the ovary in cortical inclusion cysts (CICs) with a Müllerian phenotype (Müllerian-CICs). It has been proposed that Müllerian-CICs arise either from metaplasia of mesothelial ovarian surface epithelium (OSE) entrapped within the ovary after ovulation or from normal tubal cells entrapped postovulation. However, this proposal is controversial. We therefore conducted a study of CICs in women, most of them BRCA1/2 mutation carriers, undergoing risk-reducing salpingo-oophorectomy at our institution from 2000 to 2014.

METHODS AND RESULTS

We used immunohistochemistry for PAX8, a Müllerian marker, and calretinin, a mesothelial marker to classify CIC cells. In 499 CICs from 59 women, 72.3% were positive for PAX8 (PAX8⁺ ): ≥10% of CIC cells positive; 43.5% positive for calretinin (calretinin⁺ ). The proportion of PAX8⁺ CICs increased from 62.9% in premenopausal to 80.5% in postmenopausal patients. The proportion of calretinin⁺ CICs decreased from 52.6% to 35.6%, respectively. There was significant overlap of PAX8 and calretinin positivity: 82 (16.4%) CICs were PAX8⁺ /calretinin⁺ ; 43 (40.2%) of these 82 demonstrated PAX8⁺ /calretinin⁺ in the same cells.

CONCLUSIONS

These results, and the increased ratio of PAX8⁺ to calretinin⁺ CICs from premenopausal to postmenopausal, show that many PAX8⁺ CICs probably arise from metaplasia of OSE-derived CICs. The proportion of PAX⁺ /calretinin^- CICs arising from OSE-derived CICs is unclear, but our results strongly support the proposal that many Müllerian-CICs arise from OSE via metaplasia.

Cytidine deaminase Apobec3a induction in fallopian epithelium after exposure to follicular fluid

OBJECTIVE

Ovarian carcinomas that originate from fallopian epithelial cells are suggested to arise due to repeated exposure to ovulatory follicular fluid (FF). Mechanistic explanation(s) for how this occurs are unknown. Here, we sought to understand if FF exposure to fallopian epithelial cells could induce DNA damage and expression of a known family of DNA mutators, apolipoprotein B mRNA editing enzyme, catalytic polypeptide (APOBEC) cytidine deaminases.

METHODS

Follicular fluid and matched patient plasma samples were obtained from donors. Fallopian epithelial cells (FT33-TAg, FT189, FT190, and FT194) were cultured with FF or plasma for 24h, and cell proliferation and DNA damage were assessed. Effects of FF on Apobec gene expression were determined by qRT-PCR and western blot analyses. Fallopian epithelial cells were transfected with an APOBEC3A expression vector and DNA damage was assessed.

RESULTS

Follicular fluid exposure increased epithelial cell proliferation as measured by three independent methods, and DNA damage accumulation as assessed using three independent measures. This effect was specific to FF, as matched patient plasma did not have the same effects. Increased expression of Apobec3a was observed in fallopian epithelial cells following exposure to 5 of 8 patient FF samples, and transient overexpression of APOBEC3A was sufficient to induce double strand DNA breaks.

CONCLUSIONS

Follicular fluid can induce cell proliferation and DNA damage accumulation in cultured fallopian epithelial cells. Increased expression of APOBEC3A, a known DNA mutator, may explain the high incidence of DNA damage after FF exposure. The role of Apobec3a in ovulation-induced inflammation warrants further investigation.

Integrative proteomic profiling of ovarian cancer cell lines reveals precursor cell associated proteins and functional status

A cell line representative of human high-grade serous ovarian cancer (HGSOC) should not only resemble its tumour of origin at the molecular level, but also demonstrate functional utility in pre-clinical investigations. Here, we report the integrated proteomic analysis of 26 ovarian cancer cell lines, HGSOC tumours, immortalized ovarian surface epithelial cells and fallopian tube epithelial cells via a single-run mass spectrometric workflow. The in-depth quantification of >10,000 proteins results in three distinct cell line categories: epithelial (group I), clear cell (group II) and mesenchymal (group III). We identify a 67-protein cell line signature, which separates our entire proteomic data set, as well as a confirmatory publicly available CPTAC/TCGA tumour proteome data set, into a predominantly epithelial and mesenchymal HGSOC tumour cluster. This proteomics-based epithelial/mesenchymal stratification of cell lines and human tumours indicates a possible origin of HGSOC either from the fallopian tube or from the ovarian surface epithelium.

High-grade serous ovarian cancer is the most common and aggressive ovarian cancer, with uncertain cell of origin. Here, the authors undertake a mass spectrometric analysis of 26 cancer cell lines and identify a protein signature that classifies ovarian cancer tissues into epithelial and mesenchymal groups.

Ovary and fimbrial stem cells: biology, niche and cancer origins

The mammalian ovary is covered by a single-layered epithelium that undergoes rupture and remodelling following each ovulation. Although resident stem cells are presumed to be crucial for this cyclic regeneration, their identity and mode of action have been elusive. Surrogate stemness assays and in vivo fate-mapping studies using recently discovered stem cell markers have identified stem cell pools in the ovary and fimbria that ensure epithelial homeostasis. Recent findings provide insights into intrinsic mechanisms and local extrinsic cues that govern the function of ovarian and fimbrial stem cells. These discoveries have advanced our understanding of stem cell biology in the ovary and fimbria, and lay the foundations for evaluating the contribution of resident stem cells to the initiation and progression of human epithelial ovarian cancer.

Lack of Rev7 function results in development of tubulostromal adenomas in mouse ovary

Rev7 is a subunit of Polζ, one of the translesion DNA synthesis (TLS) polymerases involved in DNA damage repair. We recently found that Rev7 is also essential for germ cell development in mouse. In the present study, we found the development of ovarian tumors in Rev7 mutant mouse, suggesting the involvement of TLS deficiency in the etiology of ovarian tumor. The Rev7 mutant mice showed complete lack of oocytes and follicles in the ovary. The lack of follicles causes a significant increase of gonadotropin level and an increase in the proliferation of ovarian cells. As a result, the weight of the ovaries of Rev7 mutant mice increased with age and they developed tubulostromal adenomas. However, the remarkable overgrowth of ovaries occurred after gonadotropin level decreases at older ages, suggesting gonadotropin-independent progression of the ovarian tumors. In addition, the Rev7 mutant fibroblasts and ovarian cells showed significant accumulation of DNA damage. These findings suggest that not only increased gonadotropin levels but also lack of DNA damage repair function could be responsible for the development of ovarian tumors in the Rev7 mutant mouse.

Ovarian carcinosarcoma associated with bilateral tubal intraepithelial carcinoma: a case report

Carcinosarcomas (malignant mixed müllerian tumors) of the ovary are rare tumors. This report describes a case of a 64 years old patient presenting with a large tumor in the true pelvis, intraoperatively originating from the right ovary, with peritoneal metastatic deposits. Histologically, a dominant sarcomatoid component consisted of short spindle and epithelioid round cells. The nuclei were round to oval, with pleomorphism, hyperchromasia and frequently conspicuous nucleoli. Mitotic activity was brisk. The cells were aligned in hypercellular to myxoid hypocellular arrangements. Large epithelioid cells displayed abundant deeply eosinophilic cytoplasm and mono- to multinucleation. Immunohistochemically, these cells displayed strong reactivities for desmin, WT1 in a cytoplasmic staining pattern, p16, and vimentin. A second and minor tumor component revealed epithelial differentiation with mixed serous- endometrioid and squamous features, and immunohistochemical staining for AE1/AE3 cytokeratin, focally for p16 and p53(ink4), for nuclear WT1 in varying quantities, and weakly for vimentin. The fallopian tubes were remarkable for circumscribed areas of serous tubal intraepithelial carcinoma (STIC), found at the fimbria of the right and in the tubal mucosa close to the fimbria of the left tube. The final diagnosis was carcinosarcoma of the right ovary (malignant müllerian mixed tumor, heterologous type), with rhabdomyosarcomatous differentiations, FIGO stage IIIC. The patient died of recurrent tumor seven month after primary presentation.

Role of the stem cell niche in the pathogenesis of epithelial ovarian cancers

Ovarian cancer is the fifth leading cause of cancer-related deaths among women in the United States. Recent extensive genomic analyses of epithelial ovarian cancer (EOC), particularly the most common and deadly form of high-grade serous ovarian carcinoma, have provided important insights into the repertoire of molecular aberrations that are characteristic for this malignancy. However, interpretation of the discovered aberrations is complicated because the origin and mechanisms of progression of EOC remain uncertain. Here, we summarize current views on the cell of origin of EOC and discuss recent findings of a cancer-prone stem cell niche for ovarian surface epithelium, one of the major likely sources of EOC. We also outline future directions and challenges in studying the role of stem cell niches in EOC pathogenesis.

Epithelial ovarian cancer stem cells: underlying complexity of a simple paradigm

The lack of significant progress in the treatment of epithelial ovarian cancer (EOC) underscores the need to gain a better understanding of the processes that lead to chemoresistance and recurrence. The cancer stem cell (CSC) hypothesis offers an attractive explanation of how a subpopulation of cells within a patient's tumour might remain refractory to treatment and subsequently form the basis of recurrent chemoresistant disease. This review examines the literature defining somatic stem cells of the ovary and fallopian tube, two tissues that give rise to EOC. In addition, considerable research has been reviewed, that has identified subpopulations of EOC cells, based on marker expression (CD133, CD44, CD117, CD24, epithelial cell adhesion molecule, LY6A, ALDH1 and side population (SP)), which are enriched for tumour initiating cells (TICs). While many studies identified either CD133 or CD44 as markers useful for enriching for TICs, there is little consensus. This suggests that EOC cells may have a phenotypic plasticity that may preclude the identification of universal markers defining a CSC. The assay that forms the basis of quantifying TICs is the xenograft assay. Considerable controversy surrounds the xenograft assay and it is essential that some of the potential limitations be examined in this review. Highlighting such limitations or weaknesses is required to properly evaluate data and broaden our interpretation of potential mechanisms that might be contributing to the pathogenesis of ovarian cancer.

Coming into focus: the nonovarian origins of ovarian cancer

BACKGROUND

The traditional view of epithelial ovarian cancer asserts that all tumor subtypes share a common origin in the ovarian surface epithelium (OSE) DESIGN: A literature review was carried out to summarize the emerging understanding of extraovarian sources of epithelial ovarian carcinomas.

RESULTS

Historically, there were no diagnostic criteria for documenting the origin of ovarian epithelial carcinomas. Moreover, there are no normal epithelial tissues in the ovary with morphologic similarities to these tumors. In fact, no precursor lesions have ever been reproducibly identified in the ovary. However, there is a strong correlation between extrauterine Müllerian tissue and the development of ovarian carcinomas, tumors of low malignant potential, and cystadenomas. The most recent support for this hypothesis comes from the careful analysis of risk-reducing bilateral salpingo-oopherectomy specimens from BRCA1 or BRCA2 mutation carriers. These studies showed that a significant majority of high-grade serous ovarian carcinomas, the most common subtype, arise from the fallopian tube fimbriae rather than the OSE.

CONCLUSIONS

Mounting evidence indicates that the vast majority of epithelial ovarian carcinomas are not ovarian in origin. Extrauterine Müllerian epithelium from various sites in the reproductive tract likely accounts for the diverse morphology and behavior of these tumors.

Dysregulated estrogen receptor signaling in the hypothalamic-pituitary-ovarian axis leads to ovarian epithelial tumorigenesis in mice

The etiology of ovarian epithelial cancer is poorly understood, mainly due to the lack of an appropriate experimental model for studying the onset and progression of this disease. We have created a mutant mouse model in which aberrant estrogen receptor alpha (ERα) signaling in the hypothalamic-pituitary-ovarian axis leads to ovarian epithelial tumorigenesis. In these mice, termed ERα^d/d, the ERα gene was conditionally deleted in the anterior pituitary, but remained intact in the hypothalamus and the ovary. The loss of negative-feedback regulation by estrogen (E) at the level of the pituitary led to increased production of luteinizing hormone (LH) by this tissue. Hyperstimulation of the ovarian cells by LH resulted in elevated steroidogenesis, producing high circulating levels of steroid hormones, including E. The ERα^d/d mice exhibited formation of palpable ovarian epithelial tumors starting at 5 months of age with 100% penetrance. By 15 months of age, 80% of ERα^d/d mice die. Besides proliferating epithelial cells, these tumors also contained an expanded population of luteinized stromal cells, which acquire the ability to express P450 aromatase and synthesize E locally. In response to the elevated levels of E, the ERα signaling was accentuated in the ovarian epithelial cells of ERα^d/d mice, triggering increased ERα-dependent gene expression, abnormal cell proliferation, and tumorigenesis. Consistent with these findings, treatment of ERα^d/d mice with letrozole, an aromatase inhibitor, markedly reduced circulating E and ovarian tumor volume. We have, therefore, developed a unique animal model, which serves as a useful tool for exploring the involvement of E-dependent signaling pathways in ovarian epithelial tumorigenesis.

Ovarian cancer is currently the most lethal gynecological cancer in the United States. Multiple epidemiological studies indicate that women who take hormone replacement therapy, estrogen or estrogen with progesterone, peri- or postmenopause will have an increased chance of developing ovarian cancer. Unfortunately, the five-year survival rate after diagnosis is very low indicating that better tools are needed to diagnose and treat ovarian cancer. The models that would allow investigation of this disease are severely limited. In this article we introduce a mouse model that develops epithelial ovarian tumors, and by employing inhibitors of estrogen synthesis, we show that ovarian tumorigenesis in this model is dependent on estrogen production within the ovarian tumor. These studies suggest that estrogen may play a role in promoting ovarian tumor growth.

Role of the interleukin 6 receptor family in epithelial ovarian cancer and its clinical implications

Ovarian cancer is the most lethal gynecological malignancy, with few effective treatment options in most cases. Therefore, understanding the biology of ovarian cancer remains an important area of research in order to improve clinical outcomes. Cytokine receptor signaling through the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway is an essential component of normal development and homeostasis. However, numerous studies have implicated perturbation of this pathway in a range of cancers. In particular, members of the IL-6R family acting via the downstream STAT3 transcription factor play an important role in a number of solid tumors - including ovarian cancer - by altering the expression of target genes that impact on key phenotypes. This has led to the development of specific inhibitors of this pathway which are being used in combination with standard chemotherapeutic agents. This review focuses on the role of IL-6R family members in the etiology of epithelial ovarian cancer, and the application of therapies specifically targeting IL-6R signaling in this disease setting.

In vivo and in vitro studies on apoptosis in OSE cells and inclusion cysts of pregnant heifers

Elevated progesterone concentration during pregnancy and use of progesterone-like contraceptives are known to reduce ovarian cancers. This study was undertaken to decipher whether or not there is any relationship between progesterone (also oestrogen)-mediated ovarian surface epithelium (OSE) apoptosis and expression of p53, a cell-cycle arresting protein and potential tumour suppressor. Immunohistochemical staining with cytokeratin confirmed epithelial nature of the cells in the OSE layer and inclusion cysts that invaginate inside stroma after ovulation takes place. The in situ apoptosis index was determined during oestrus, and at mid and late-pregnancy stages in heifers. Epithelia of both tissues exhibited significantly high nuclear staining, suggesting that these cells are aiming to apoptotic destruction. To further establish a role of progesterone, the OSE cells were exposed in vitro to two concentrations of oestrogen and progesterone. It was revealed that progesterone at both concentrations and oestrogen only at high concentration converted a large proportion of these cells apoptotic. The stimulatory effect of progesterone (and to some extent oestrogen) was also seen on p53 expression in the same cultivated OSE cells. The steroid dosage dependence for apoptosis and p53 expression was also somewhat similar. Assuming that progesterone action is mediated through p53-caused apoptosis as a mechanism to evade malignant transformation of OSE cells, p53 expression at mRNA and protein level was investigated in the OSE layer in proximity to stroma, antrum and corpus luteum (CL). In cycling animals CL produces a large amount of progesterone and also oestrogen to maintain the post-ovulatory cycle and to suppress the gonadotropin production. Hence, cells undergoing re-epithelialization and which are in contact with CL were expected to undergo maximum apoptotic modification. Indeed we got the maximum p53/p53 gene expression in these cells. We conclude that progesterone during cycling and pregnancy may reduce the risk of developing ovarian cancer by ceasing cell cycle and diverting damaged and mutagenized OSE cells for apoptosis, and the process may be mediated through elevated p53 synthesis. However, it is also possible that progesterone and p53-induced apoptosis may be entirely different cancer suppressive actions but coincidently happening together.

MicroRNAs and Recent Insights into Pediatric Ovarian Cancers

Ovarian cancer is the most common pediatric gynecologic malignancy. When diagnosed in children, ovarian cancers present unique challenges that differ dramatically from those faced by adults. Here, we review the spectrum of ovarian cancers found in young women and girls and discuss the biology of these diseases. A number of advances have recently shed significant new understanding on the potential causes of ovarian cancer in this unique population. Particular emphasis is placed on understanding how altered expression of non-coding RNA transcripts known as microRNAs play a key role in the etiology of ovarian germ cell and sex cord-stromal tumors. Emerging transgenic models for these diseases are also reviewed. Lastly, future challenges and opportunities for understanding pediatric ovarian cancers, delineating clinically useful biomarkers, and developing targeted therapies are discussed.

Tu-be or not tu-be: that is the question… about serous ovarian carcinogenesis

Our understanding of the early natural history of epithelial ovarian carcinoma is limited by the access to early lesions as the disease is very often diagnosed at advanced stages. The incessant ovulation theory from the last century that indicated the ovary as the site for the initiation of high-grade serous cancers is contrary to the newly emerging idea that ovarian cancer could arise from the distal fallopian tube. In view of the recent pathological and molecular studies, we propose to discuss the genesis of high-grade serous ovarian cancer.

Ovarian surface epithelium at the junction area contains a cancer-prone stem cell niche

Epithelial ovarian cancer (EOC) is the fifth leading cause of cancer deaths among women in the United States, but its pathogenesis is poorly understood. Some epithelial cancers are known to occur in transitional zones between two types of epithelium, whereas others have been shown to originate in epithelial tissue stem cells. The stem cell niche of the ovarian surface epithelium (OSE), which is ruptured and regenerates during ovulation, has not yet been defined unequivocally. Here we identify the hilum region of the mouse ovary, the transitional (or junction) area between the OSE, mesothelium and tubal (oviductal) epithelium, as a previously unrecognized stem cell niche of the OSE. We find that cells of the hilum OSE are cycling slowly and express stem and/or progenitor cell markers ALDH1, LGR5, LEF1, CD133 and CK6B. These cells display long-term stem cell properties ex vivo and in vivo, as shown by our serial sphere generation and long-term lineage-tracing assays. Importantly, the hilum cells show increased transformation potential after inactivation of tumour suppressor genes Trp53 and Rb1, whose pathways are altered frequently in the most aggressive and common type of human EOC, high-grade serous adenocarcinoma. Our study supports experimentally the idea that susceptibility of transitional zones to malignant transformation may be explained by the presence of stem cell niches in those areas. Identification of a stem cell niche for the OSE may have important implications for understanding EOC pathogenesis.

Gonadotropins activate oncogenic pathways to enhance proliferation in normal mouse ovarian surface epithelium

Ovarian cancer is the most lethal gynecological malignancy affecting American women. The gonadotropins, follicle stimulating hormone (FSH) and luteinizing hormone (LH), have been implicated as growth factors in ovarian cancer. In the present study, pathways activated by FSH and LH in normal ovarian surface epithelium (OSE) grown in their microenvironment were investigated. Gonadotropins increased proliferation in both three-dimensional (3D) ovarian organ culture and in a two-dimensional (2D) normal mouse cell line. A mouse cancer pathway qPCR array using mRNA collected from 3D organ cultures identified Akt as a transcriptionally upregulated target following stimulation with FSH, LH and the combination of FSH and LH. Activation of additional pathways, such as Birc5, Cdk2, Cdk4, and Cdkn2a identified in the 3D organ cultures, were validated by western blot using the 2D cell line. Akt and epidermal growth factor receptor (EGFR) inhibitors blocked gonadotropin-induced cell proliferation in 3D organ and 2D cell culture. OSE isolated from 3D organ cultures stimulated with LH or hydrogen peroxide initiated growth in soft agar. Hydrogen peroxide stimulated colonies were further enhanced when supplemented with FSH. LH colony formation and FSH promotion were blocked by Akt and EGFR inhibitors. These data suggest that the gonadotropins stimulate some of the same proliferative pathways in normal OSE that are activated in ovarian cancers.

Early transformative changes in normal ovarian surface epithelium induced by oxidative stress require Akt upregulation, DNA damage and epithelial-stromal interaction

Ovarian cancer is the deadliest gynecological malignancy due to detection of cancer at a late stage when the disease has metastasized. One likely progenitor cell type of ovarian cancer is the ovarian surface epithelium (OSE), which proliferates rapidly in the presence of inflammatory cytokines and oxidative stress following ovulation. To determine whether oxidative stress induces DNA damage leading to spontaneous transformative changes in normal OSE, an immortalized mouse OSE cell line (MOSE cells) or normal mouse ovarian organoids were treated with hydrogen peroxide (H2O2) and loss of contact inhibition was assessed by soft agar assay. In response to H2O2, OSE cells grown in 3D exhibited growth in soft agar but MOSE cells grown on 2D plastic did not, indicating a critical role for epithelial-stromal interactions in neoplastic initiation. Loss of contact inhibition in response to H2O2 correlated with an increase in proliferation, DNA damage and upregulation of the oncogene Akt1. Use of a reactive oxygen species scavenger or Akt inhibitor blocked H2O2-induced proliferation and growth in soft agar. Although parental MOSE cells did not undergo transformation by H2O2, MOSE cells stably overexpressing constitutively active myristoylated Akt or knockdown of phosphatase and tensin homolog (PTEN) exhibited loss of contact inhibition and increased proliferation. This study indicates that normal OSE undergo transformative changes induced by oxidative stress and that this process requires Akt upregulation and activation. A 3D model that retains tissue architecture is critical for studying this process and may lead to development of new intervention strategies directed at early stages of ovarian cancer.

Technical challenges and limitations of current mouse models of ovarian cancer

The development of genetically engineered models (GEM) of epithelial ovarian cancer (EOC) has been very successful, with well validated models representing high grade and low grade serous adenocarcinomas and endometrioid carcinoma (EC). Most of these models were developed using technologies intended to target the ovarian surface epithelium (OSE), the cell type long believed to be the origin of EOC. More recent evidence has highlighted what is likely a more prevalent role of the secretory cell of the fallopian tube in the ontogeny of EOC, however none of the GEM of EOC have demonstrated successful targeting of this important cell type.

The precise technologies exploited to develop the existing GEM of EOC are varied and carry with them advantages and disadvantages. The use of tissue specific promoters to model disease has been very successful, but the lack of any truly specific OSE or oviductal secretory cell promoters makes the outcomes of these models quite unpredictable. Effecting genetic change by the administration of adenoviral vectors expressing Cre recombinase may alleviate the perceived need for tissue specific promoters, however the efficiencies of infection of different cell types is subject to numerous biological parameters that may lead to preferential targeting of certain cell populations.

One important future avenue of GEM of EOC is the evaluation of the role of genetic modifiers. We have found that genetic background can lead to contrasting phenotypes in one model of ovarian cancer, and data from other laboratories have also hinted that the exact genetic background of the model may influence the resulting phenotype. The different genetic backgrounds may modify the biology of the tumors in a manner that will be relevant to human disease, but they may also be modifying parameters which impact the response of the host to the technologies employed to develop the model.

Evaluating the progenitor cells of ovarian cancer: analysis of current animal models

Serous ovarian cancer is one of the most lethal gynecological malignancies. Progress on effective diagnostics and therapeutics for this disease are hampered by ambiguity as to the cellular origins of this histotype of ovarian cancer, as well as limited suitable animal models to analyze early stages of disease. In this report, we will review current animal models with respect to the two proposed progenitor cells for serous ovarian cancer, the ovarian surface epithelium and the fallopian tube epithelium.

The impact of ovulation on fallopian tube epithelial cells: evaluating three hypotheses connecting ovulation and serous ovarian cancer

Ovarian cancer is the most lethal gynecological malignancy affecting American women. Current hypotheses concerning the etiology of ovarian cancer propose that a reduction in the lifetime number of ovulations decreases ovarian cancer risk. Advanced serous carcinoma shares several biomarkers with fallopian tube epithelial cells, suggesting that some forms of ovarian carcinoma may originate in the fallopian tube. Currently, the impact of ovulation on the tubal epithelium is unknown. In CD1 mice, ovulation did not increase tubal epithelial cell (TEC) proliferation as measured by bromodeoxyuridine incorporation and proliferating cell nuclear antigen staining as compared to unstimulated animals. In superovulated mice, an increase in the number of pro-inflammatory macrophages was detected in the oviduct. Ovulation also increased levels of phospho-γH2A.X in TEC, indicating that these cells were susceptible to double-strand DNA breakage following ovulation. To determine which components of ovulation contributed to DNA damage in the fallopian tube, an immortalized baboon TEC cell line and a three-dimensional organ culture system for mouse oviduct and baboon fallopian tubes were developed. TEC did not proliferate or display increased DNA damage in response to the gonadotropins or estradiol alone in vitro. Oxidative stress generated by treatment with hydrogen peroxide or macrophage-conditioned medium increased DNA damage in TEC in culture. Ovulation may impact the fallopian tube epithelium by generating DNA damage and stimulating macrophage infiltration but does not increase proliferation through gonadotropin signaling.

Molecular and functional characteristics of ovarian surface epithelial cells transformed by KrasG12D and loss of Pten in a mouse model in vivo

Ovarian cancer is a complex and deadly disease that remains difficult to detect at an early curable stage. Furthermore, although some oncogenic (Kras, Pten/PI3K and Trp53) pathways that are frequently mutated, deleted or amplified in ovarian cancer are known, how these pathways initiate and drive specific morphological phenotypes and tumor outcomes remain unclear. We recently generated Pten(fl/fl); Kras(G12D); Amhr2-Cre mice to disrupt the Pten gene and express a stable mutant form of Kras(G12D) in ovarian surface epithelial (OSE) cells. On the basis of histopathologic criteria, the mutant mice developed low-grade ovarian serous papillary adenocarcinomas at an early age and with 100% penetrance. This highly reproducible phenotype provides the first mouse model in which to study this ovarian cancer subtype. OSE cells isolated from ovaries of mutant mice at 5 and 10 weeks of age exhibit temporal changes in the expression of specific Mullerian epithelial marker genes, grow in soft agar and develop ectopic invasive tumors in recipient mice, indicating that the cells are transformed. Gene profiling identified specific mRNAs and microRNAs differentially expressed in purified OSE cells derived from tumors of the mutant mice compared with wild-type OSE cells. Mapping of transcripts or genes between the mouse OSE mutant data sets, the Kras signature from human cancer cell lines and the human ovarian tumor array data sets, documented significant overlap, indicating that KRAS is a key driver of OSE transformation in this context. Two key hallmarks of the mutant OSE cells in these mice are the elevated expression of the tumor-suppressor Trp53 (p53) and its microRNA target, miR-34a-c. We propose that elevated TRP53 and miR-34a-c may exert negatively regulatory effects that reduce the proliferative potential of OSE cells leading to the low-grade serous adenocarcinoma phenotype.

Epithelial ovarian carcinoma types and the coexistence of ovarian tumor conditions

Objective. Ovarian carcinomas are presumed to arise within ovarian inclusion cysts or from a coexisting epithelial lesion in the ovary. Insight may be gained by relating different subtypes of ovarian cancer with the presence of coexisting tumor-like conditions. Methods. The Dutch nation-wide pathology database PALGA (Pathologisch Anatomisch Landelijk Geautomatiseerd Archief) identified the various histopathological subtypes of ovarian cancer in 824 patients diagnosed in 1996–2003, and recorded the presence of epithelial tumor conditions around the ovarian tumors. In addition, a PALGA database of all 153 consecutive patients referred to the Nijmegen University Medical Centre in 2007 for histopathological work-up was analyzed. Results. The prevalence of coexisting ovarian tumor conditions was 16.4% (135 out of 824 patients, (95% CI: 8.4%–24.4%)). The coexistence was highest for endometrioid, mucinous, clear cell, and borderline malignancies. The referral group revealed 35% (54 out of 153 patients, (95% CI: 28%–42%)) of coexisting epithelial ovarian tumor conditions. Conclusion. One in six patients with a malignant ovarian tumor has a coexisting epithelial tumor condition in the ovary, which is also rather frequently observed in the diagnostic work-up practice.

Increased incidence of endometrioid tumors caused by aberrations in E-cadherin promoter of mismatch repair-deficient mice

Loss of E-cadherin expression is a critical step in the development and progression of gynecological tumors. Study of the precise role of E-cadherin has been hampered by the lack of satisfactory mouse model for E-cadherin deficiency. Likewise, DNA mismatch repair (MMR) is implicated in gynecological tumorigenesis, but knockout of MMR in mice predominantly causes hematologic neoplasms. Here, we show that combined disruption of E-cadherin and DNA MMR pathways increases incidence of endometrioid tumors in mice. Twenty percent of mice knockout for Msh2 enzyme and hemizygous for E-cadherin [Msh2(-/-)/Cdh1(+/-)] developed endometrioid-like tumors in the ovary, uterus and genital area. Characteristic of these tumors was a complete loss of E-cadherin expression. Sequence analysis of E-cadherin promoter region demonstrated that the loss of E-cadherin expression is caused by inactivating mutations, implying that E-cadherin is a mutational target in Msh2-deficient mice. In addition, Msh2(-/-)/Cdh1(+/-) mice showed a reduction in overall survival as compared with their Msh2(-/-) counterparts due to the development of more aggressive lymphomas, suggesting a specific role of E-cadherin in lymphomagenesis. In conclusion, Msh2(-/-)/Cdh1(+/-) mice provide a good model of gynecological tumorigenesis and may be useful for testing molecular target-specific therapies.

Alginate hydrogels for three-dimensional organ culture of ovaries and oviducts

Ovarian cancer is the fifth leading cause of cancer deaths in women and has a 63% mortality rate in the United States(1). The cell type of origin for ovarian cancers is still in question and might be either the ovarian surface epithelium (OSE) or the distal epithelium of the fallopian tube fimbriae(2,3). Culturing the normal cells as a primary culture in vitro will enable scientists to model specific changes that might lead to ovarian cancer in the distinct epithelium, thereby definitively determining the cell type of origin. This will allow development of more accurate biomarkers, animal models with tissue-specific gene changes, and better prevention strategies targeted to this disease. Maintaining normal cells in alginate hydrogels promotes short term in vitro culture of cells in their three-dimensional context and permits introduction of plasmid DNA, siRNA, and small molecules. By culturing organs in pieces that are derived from strategic cuts using a scalpel, several cultures from a single organ can be generated, increasing the number of experiments from a single animal. These cuts model aspects of ovulation leading to proliferation of the OSE, which is associated with ovarian cancer formation. Cell types such as the OSE that do not grow well on plastic surfaces can be cultured using this method and facilitate investigation into normal cellular processes or the earliest events in cancer formation(4). Alginate hydrogels can be used to support the growth of many types of tissues(5). Alginate is a linear polysaccharide composed of repeating units of β-D-mannuronic acid and α-L-guluronic acid that can be crosslinked with calcium ions, resulting in a gentle gelling action that does not damage tissues(6,7). Like other three-dimensional cell culture matrices such as Matrigel, alginate provides mechanical support for tissues; however, proteins are not reactive with the alginate matrix, and therefore alginate functions as a synthetic extracellular matrix that does not initiate cell signaling(5). The alginate hydrogel floats in standard cell culture medium and supports the architecture of the tissue growth in vitro. A method is presented for the preparation, separation, and embedding of ovarian and oviductal organ pieces into alginate hydrogels, which can be maintained in culture for up to two weeks. The enzymatic release of cells for analysis of proteins and RNA samples from the organ culture is also described. Finally, the growth of primary cell types is possible without genetic immortalization from mice and permits investigators to use knockout and transgenic mice.

Dynamics of the primate ovarian surface epithelium during the ovulatory menstrual cycle

BACKGROUND

Epithelial ovarian cancer (EOC) risk correlates strongly with the number of ovulations that a woman experiences. The primary source of EOC in women is the ovarian surface epithelium (OSE). Mechanistic studies on the etiology of OSE transformation to EOC cannot be realistically performed in women. Selecting a suitable animal model to investigate the normal OSE in the context of ovulation should be guided by the model's reproductive similarities to women in natural features that are thought to contribute to EOC risk.

METHODS

We selected the non-human primate, rhesus macaque, as a surrogate to study the normal OSE during the natural menstrual cycle. We investigated OSE morphology and marker expression, plus cell proliferation and death in relation to menstrual cycle stage and ovulation.

RESULTS

OSE cells displayed a morphological range from squamous to columnar. Cycle-independent parameters and cycle-dependent changes were observed for OSE histology, steroid receptor expression, cell death, DNA repair and cell adhesion. Contrary to findings in non-primates, primate OSE cells were not manifestly cleared from the site of ovulation, nor were proliferation rates affected by ovulation or stage of the menstrual cycle. DNA repair proteins were more highly expressed in OSE than in other ovarian cells.

CONCLUSIONS

This study identifies significant differences between primate and non-primate OSE. In contrast to established views, ovulation-induced death and proliferation are not indicated as prominent contributors to EOC risk, but disruption of OSE cadherin-mediated adhesion may be, as could the loss of ovary-mediated chronic suppression of proliferation and elevation of DNA repair potential.

Ovarian surface epitheliectomy in the non-human primate: continued cyclic ovarian function and limited epithelial replacement

BACKGROUND

The fifth leading cause of cancer deaths among women is ovarian cancer (OC), which originates primarily in the ovarian surface epithelium (OSE) that surrounds the ovary. Permanent removal of the OSE could provide a novel strategy to substantially reduce OC risk, while retaining the benefits of ovarian function, including gameto- and steroidogenesis. It must be determined whether ovarian surface epitheliectomy (OSEx) carries deleterious side effects, including loss of menstrual cyclicity, infertility or scarring (e.g. adhesions), prior to any clinical application of this strategy. To achieve this, we selected the non-human primate, rhesus macaque, for long-term (12 month) studies on the effects of OSEx.

METHODS

Rhesus macaque females underwent OSEx by detergent treatment and were then monitored for menstrual cyclicity (menstruation, steroidogenesis and follicle development) and adverse side effects (tissue scarring or adhesions). Ovaries were collected at 6 or 12 months and examined for evidence of tissue damage, follicle rupture and regression of the corpus luteum. The ovarian surface was examined immunohistologically for signs of epithelial replacement, using markers for OSE and fimbrial epithelium (FE), a possible alternative source of pelvic tumors diagnosed as OC.

RESULTS

After OSEx, menstrual cycle length, estrogen and progesterone production, follicle rupture and luteal regression appeared normal. No evidence of adhesions was seen. At 6 and 12 months post-OSEx, the ovarian surface was sparsely populated by cells expressing OSE and FE markers. Proliferative activity in this population was notably low.

CONCLUSIONS

OSEx may provide a novel method to reduce the risk of OC, without sacrificing ovarian function, although the effects on fertility remain to be tested. The absence of epithelial replacement via enhanced proliferation suggests OSEx does not increase malignant potential. Complete and permanent OSEx may be feasible.

Ovarian cancer development and metastasis

The biology of ovarian carcinoma differs from that of hematogenously metastasizing tumors because ovarian cancer cells primarily disseminate within the peritoneal cavity and are only superficially invasive. However, since the rapidly proliferating tumors compress visceral organs and are only temporarily chemosensitive, ovarian carcinoma is a deadly disease, with a cure rate of only 30%. There are a number of genetic and epigenetic changes that lead to ovarian carcinoma cell transformation. Ovarian carcinoma could originate from any of three potential sites: the surfaces of the ovary, the fallopian tube, or the mesothelium-lined peritoneal cavity. Ovarian cacinoma tumorigenesis then either progresses along a stepwise mutation process from a slow growing borderline tumor to a well-differentiated carcinoma (type I) or involves a genetically unstable high-grade serous carcinoma that metastasizes rapidly (type II). During initial tumorigenesis, ovarian carcinoma cells undergo an epithelial-to-mesenchymal transition, which involves a change in cadherin and integrin expression and up-regulation of proteolytic pathways. Carried by the peritoneal fluid, cancer cell spheroids overcome anoikis and attach preferentially on the abdominal peritoneum or omentum, where the cancer cells revert to their epithelial phenotype. The initial steps of metastasis are regulated by a controlled interaction of adhesion receptors and proteases, and late metastasis is characterized by the oncogene-driven fast growth of tumor nodules on mesothelium covered surfaces, causing ascites, bowel obstruction, and tumor cachexia.

Human ovarian cancer stem cells

The isolation and identification of stem-like cells in solid tumors or cancer stem cells (CSCs) have been exciting developments of the last decade, although these rare populations had been earlier identified in leukemia. CSC biology necessitates a detailed delineation of normal stem cell functioning and maintenance of homeostasis within the organ. Ovarian CSC biology has unfortunately not benefited from a pre-established knowledge of stem cell lineage demarcation and functioning in the normal organ. In the absence of such information, some of the classical parameters such as long-term culture-initiating assays to isolate stem cell clones from tumors, screening and evaluation of other epithelial stem cell surface markers, dye efflux, and label retention have been applied toward the putative isolation of CSCs from ovarian tumors. The present review presents an outline of the various approaches developed so far and the various perspectives revealed that are now required to be dealt with toward better disease management.

Chlamydia trachomatis, Mycoplasma genitalium, Neisseria gonorrhoeae, human papillomavirus, and polyomavirus are not detectable in human tissue with epithelial ovarian cancer, borderline tumor, or benign conditions

OBJECTIVE

We sought to analyze the presence of the microorganisms Chlamydia trachomatis, Mycoplasma genitalium, Neisseria gonorrhoeae, human papillomavirus (HPV), and the polyomaviruses BK virus (BKV) and JC virus (JCV) in ovarian tissues of women with ovarian carcinomas, borderline tumors, and benign conditions.

STUDY DESIGN

Ovarian tissue, snap-frozen and stored at -80 degrees C, from 186 women with benign conditions, borderline tumors, and epithelial ovarian cancer, as well as tissue from the contralateral ovary of 126 of these women, were analyzed regarding presence of C trachomatis and N gonorrhoeae (transcription mediated amplification), M genitalium (real-time polymerase chain reaction [PCR]), HPV (PCR), and BKV and JCV (PCR).

RESULTS

All the tissue samples studied were found negative for the microorganisms analyzed.

CONCLUSION

C trachomatis, M genitalium, N gonorrhoeae, HPV, and the polyomaviruses BKV and JCV are not detectable in ovarian tissues either from women with benign conditions and borderline tumors or from women with ovarian cancer.

The unique characteristics of ovarian carcinogenesis in the adolescent and young adult population

Ovarian cancer in the adolescent and young adult (AYA) population is a disease that is distinctly different with regard to risk factors, genetics, and pathology when compared to ovarian cancers occurring in older women. This article will review the theories behind ovarian carcinogenesis and attempt to elucidate why these tumors exhibit their unique biologic characteristics. Knowledge of these differences will allow us to begin to develop strategies for future research endeavors enabling improved survival in AYA women diagnosed with ovarian cancer.