The PAX2-null immunophenotype defines multiple lineages with common expression signatures in benign and neoplastic oviductal epithelium

The oviducts contain high-grade serous cancer (HGSC) precursors (serous tubal intraepithelial neoplasia or STINs), which are γ-H2AX(p) - and TP53 mutation-positive. Although they express wild-type p53, secretory cell outgrowths (SCOUTs) are associated with older age and serous cancer; moreover, both STINs and SCOUTs share a loss of PAX2 expression (PAX2(n) ). We evaluated PAX2 expression in proliferating adult and embryonic oviductal cells, normal mucosa, SCOUTs, Walthard cell nests (WCNs), STINs, and HGSCs, and the expression of genes chosen empirically or from SCOUT expression arrays. Clones generated in vitro from embryonic gynaecological tract and adult Fallopian tube were Krt7(p) /PAX2(n) /EZH2(p) and underwent ciliated (PAX2(n) /EZH2(n) /FOXJ1(p) ) and basal (Krt7(n) /EZH2(n) /Krt5(p) ) differentiation. Similarly, non-ciliated cells in normal mucosa were PAX2(p) but became PAX2(n) in multi-layered epithelium undergoing ciliated or basal (WCN) cell differentiation. PAX2(n) SCOUTs fell into two groups: type 1 were secretory or secretory/ciliated with a 'tubal' phenotype and were ALDH1(n) and β-catenin(mem) (membraneous only). Type 2 displayed a columnar to pseudostratified (endometrioid) phenotype, with an EZH2(p) , ALDH1(p) , β-catenin(nc) (nuclear and cytoplasmic), stathmin(p) , LEF1(p) , RCN1(p) , and RUNX2(p) expression signature. STINs and HGSCs shared the type 1 immunophenotype of PAX2(n) , ALDH1(n) , β-catenin(mem) , but highly expressed EZH2(p) , LEF1(p) , RCN1(p) , and stathmin(p) . This study, for the first time, links PAX2(n) with proliferating fetal and adult oviductal cells undergoing basal and ciliated differentiation and shows that this expression state is maintained in SCOUTs, STINs, and HGSCs. All three entities can demonstrate a consistent perturbation of genes involved in potential tumour suppressor gene silencing (EZH2), transcriptional regulation (LEF1), regulation of differentiation (RUNX2), calcium binding (RCN1), and oncogenesis (stathmin). This shared expression signature between benign and neoplastic entities links normal progenitor cell expansion to abnormal and neoplastic outgrowth in the oviduct and exposes a common pathway that could be a target for early prevention.

Transformation of the fallopian tube secretory epithelium leads to high-grade serous ovarian cancer in Brca;Tp53;Pten models

High-grade serous ovarian carcinoma presents significant clinical and therapeutic challenges. Although the traditional model of carcinogenesis has focused on the ovary as a tumor initiation site, recent studies suggest that there may be additional sites of origin outside the ovary, namely the secretory cells of the fallopian tube. Our study demonstrates that high-grade serous tumors can originate in fallopian tubal secretory epithelial cells and also establishes serous tubal intraepithelial carcinoma as the precursor lesion to high-grade serous ovarian and peritoneal carcinomas in animal models targeting the Brca, Tp53, and Pten genes. These findings offer an avenue to address clinically important questions that are critical for cancer prevention and early detection in women carrying BRCA1 and BRCA2 mutations.

Through the glass darkly: intraepithelial neoplasia, top-down differentiation, and the road to ovarian cancer

It is currently hoped that deaths from extra-uterine high-grade serous cancer (HGSC) will be reduced via opportunistic salpingectomy in healthy women. Accumulated data implicate the fimbria as a site of origin and descriptive molecular pathology and experimental evidence strongly support a serous carcinogenic sequence in the Fallopian tube. Both direct and indirect ('surrogate') precursors suggest that the benign tube undergoes important biological changes after menopause, acquiring abnormalities in gene expression that are often shared with malignancy, including PAX2, ALDH1, LEF1, RCN1, RUNX2, beta-catenin, EZH2, and others. However, the tube can be linked to only some HGSCs, recharging arguments that nearby peritoneum/ovarian surface epithelium (POSE) also hosts progenitors to this malignancy. A major sticking point is the difference in immunophenotype between POSE and Müllerian epithelium, essentially requiring mesothelial to Müllerian differentiation prior to or during malignant transformation to HGSC. However, emerging evidence implicates an embryonic or progenitor phenotype in the adult female genital tract with the capacity to differentiate, normally or during neoplastic transformation. Recently, a putative cell of origin for cervical cancer has been identified in the squamo-columnar (SC) junction, projecting a model whereby Krt7+ embryonic progenitors give rise to immunophenotypically distinct progeny under stromal influences via 'top down' differentiation. Similar differentiation can be seen in the endometrium with a parallel in juxtaposed mesothelial and Müllerian differentiation in the ovary. Abrupt mesothelial-Müllerian transitions remain to be proven, but would explain the rapid evolution, short asymptomatic interval, and absence of a defined epithelial starting point in many HGSCs. Resolving this question will require accurately distinguishing progenitor from progeny tumour cells in HGSC and pinpointing where initial transformation and trans-differentiation occur, whether in the tube or POSE. Both will be critical to expectations from prophylactic salpingectomy and future approaches to pelvic serous cancer prevention.

Epigenetic biomarkers in the diagnosis of ovarian cancer

INTRODUCTION

Current diagnostic methods for ovarian cancer have limited performance. Recent advances within the field of epigenetics have shifted the clinical implementation of epigenetic biomarkers as a diagnostic approach from a dream for the future to a present-day consideration. Patients could potentially benefit greatly from this novel diagnostic approach.

AREAS COVERED

Epigenetic mechanisms in cancer are discussed, with a focus on potential diagnostic epigenetic biomarkers in ovarian cancer in tissue and body fluids. A literature search was undertaken (on 22-09-2011) for these subjects using the search syntax ((((((((((((((("ovarian") OR "ovary") OR "ovarian cancer") OR "ovarian cancers") OR "cancer of the ovary") OR "tumour of the ovary") OR "ovarian tumor") OR "ovarian tumors") OR "ovarian tumour") OR "ovarian tumours") OR "ovarian neoplasm") OR "ovarian neoplasms" OR "ovarian carcinoma") OR "ovarian carcinomas") OR "carcinoma of the ovary")) AND ((((((((("epigenetics") OR "epigenetic") OR "epigenome") OR "methylation") OR "hypermethylation") OR "chromatin modification") OR "histone") OR "histones") OR "acetylation")

EXPERT OPINION

To date no single epigenetic biomarker is able to accurately detect early ovarian cancer in either tissue or body fluids. A panel of epigenetic biomarkers based on aberrant DNA methylation in body fluids, especially blood, has the best chance of being implemented in clinical practice, as it is semi-invasive. However, progression toward clinical use is hampered by the lack of detection techniques combining high throughput and accuracy with low cost, by difficulties in establishing reliable reference values and by the heterogeneous nature of ovarian cancer. Until addressed, implementation as a diagnostic measure complimenting current techniques in select cases seems a far way to go, and implementation as a primary screening tool is yet even farther away.

Abstract 3292: A genetically engineered mouse model for high grade serous “ovarian” carcinoma arising in the fallopian tube

Ovarian cancer is the most lethal gynecologic malignancy because the vast majority of cases are detected in late stage, a finding that has thwarted attempts to understand the pathogenesis and cell-of-origin of this disease. The traditional view of epithelial ovarian pathogenesis asserts that all tumor subtypes share a common origin in the ovarian surface epithelium (OSE). There is robust data to support the OSE as the site of origin for many ovarian tumors, including low-grade carcinomas and borderline tumors. However, the pathogenesis of high-grade serous ovarian carcinoma, the most common type of ovarian cancer, continued to defy explanation by the OSE model. More recent studies suggested that the fallopian tube epithelium (FTE), rather than the OSE, may be the site-of-origin for a majority of pelvic serous carcinomas (PSC, defined as ovarian, peritoneal and tubal high grade serous carcinomas). We show here that the FTE can be site of origin for PSC by genetically engineering a mouse model that specifically targets the FT secretory cell with defined genetic alterations that are characteristic of human PSC. These mice develop tubal intraepithelial serous carcinomas, a precursor to PSC, that are morphologically and immunophenotypically similar to the lesions described in human patients. Furthermore, these intraepithelial lesions progress to widespread peritoneal disease that recapitulates the presentation of high-grade PSC in women. The tumors express common serous markers such as P53, αH2A.X, PAX8 and CA-125. Taken together our model is the first fully genetically engineered mouse model that truly recapitulates human serous carcinoma pathogenesis. Our model serves as proof-of-concept that the FTE can be site-of-origin to PSC.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3292. doi:1538-7445.AM2012-3292

Promoter hypermethylation patterns in fallopian tube epithelium of BRCA1 and BRCA2 germ line mutation carriers

BRCA1/2 germ line mutation carriers have a high risk of developing fallopian tube carcinoma (FTC), thought to occur through different early (p53 signatures) and later (dysplasia, intra-epithelial carcinoma) premalignant stages. Promoter hypermethylation of tumour suppressor genes is known to play a key role in (early) carcinogenesis. However, little is known about methylation in normal and (pre)malignant fallopian tube tissue. We identified 14 areas of p53 accumulation in the fallopian tubes of BRCA mutation carriers. Cells from these areas were harvested together with cells from adjacent benign appearing areas. An age-matched non-BRCA sporadic control group (n=13) and eight sporadic FTCs were included as negative and positive controls respectively. Methylation-specific multiplex ligation-dependent probe amplification was used to assess promoter methylation of 70 tumour suppressor genes in all samples. We observed a gradual increase in methylation from sporadic control tissue (median cumulative methylation index (CMI) 568.19) through normal tissue and from areas of p53 accumulation in BRCA carriers (median CMI 687.54 and 676.72) to FTC (median CMI 780.97). Furthermore, the methylation percentage of many individual tumour suppressor genes differed significantly between these groups, gradually increasing as for CMI. Between areas with and without p53 accumulation in BRCA mutation carriers no significant differences were found. In this paper, we have shown that BRCA mutation carriers display increased methylation of tumour suppressor genes in their non-malignant fallopian tube epithelium, closer to methylation levels in FTC than to normal sporadic tissue. Methylation could, therefore, play an important role in the increased risk of gynaecological malignancies in BRCA mutation carriers.