Ewing Sarcoma of the Female Genital Tract: Clinicopathologic Analysis of 21 Cases With an Emphasis on the Differential Diagnosis of Gynecologic Round Cell, Spindle, and Epithelioid Neoplasms

Ewing sarcoma is an uncommon neoplasm considered in the differential diagnosis of tumors with "small round cell" morphology, but its occurrence in the gynecologic tract has only been sporadically documented. Herein, we describe the largest cohort of Ewing sarcoma localized to the female genital tract to date, and emphasize their clinicopathologic resemblance to more common gynecologic neoplasms. Ewing sarcoma (n=21) was retrospectively identified from 5 institutions. The average patient age was 35 (range 6-61) years. Tumor sites included uterus (n=8), cervix (n=4), vulva (n=5), vagina (n=1), broad ligament (n=1), inguinal area (n=1), and pelvis (n=1). Nine of 18 cases in which slides were available for review demonstrated only classic round cell morphology, with the remainder showing a variable combination and prominence of variant ovoid/spindle or epithelioid appearance. Tumors showed diffuse membranous reactivity for CD99 (20/20) and were positive for NKX2.2 (8/8, diffuse) and cyclin D1 (7/7, of which 3/7 were patchy/multifocal and 4/7 were diffuse). They were negative for ER (0/6) and CD10 (0/6). Three cases were initially diagnosed as endometrial stromal sarcomas. EWSR1 rearrangement was confirmed in 20/21 by fluorescence in situ hybridization (n=15) and/or sequencing (n=8). Of the eight tumors that underwent sequencing, 6 harbored FLI1, 1 ERG, and 1 FEV as the fusion partner. Of 11 patients with available follow-up, 5 died of disease, 1 developed lung metastases and 5 are alive with no evidence of disease. Ewing sarcoma of the gynecologic tract is a rare, aggressive entity that shares some morphologic and immunohistochemical features with other more common gynecologic neoplasms. In addition to the typical round cell appearance, variant spindled/ovoid to epithelioid morphology may also be observed and should prompt consideration of this entity with appropriate immunohistochemical and/or molecular studies.

Genomic Catastrophe (Chromothripsis and Polyploidy) Correlates With Tumor Distribution in Extrauterine High-grade Serous Carcinoma

Most extrauterine high-grade serous carcinomas (HGSCs) are thought to develop first in the distal fallopian tube. Most models of HGSC assume origin from relatively stable, noninvasive serous tubal intraepithelial carcinomas. However, widespread tumor involvement in the absence of a serous tubal intraepithelial carcinoma could occur after catastrophic genomic events (CGEs; such as chromothripsis or polyploidy). Twenty-six HGSCs assigned to fallopian tube (n = 9, group 1) and/or ovary (n = 9, group 2), and primary peritoneal (n = 8, group 3) were assessed by microarray (Oncoscan). CGEs were identified in 15/26 (57.7%); chromothripsis-like pattern in 13/26 (50.0%) and polyploidy in 6/26 (23.1%). CGE was seen in 4/9 (44.4%), 9/9 (100%), and 2/8 (25%) cases in groups 1. 2, and 3, respectively. Overall, CGEs were seen in 9/9 (100%) cases with grossly evident ovarian parenchymal involvement versus 6/17 (35.3%) without (P = 0.0024). Ovarian size (measured on the long axis) correlated with CGE positivity (P = 0.016). CGEs are significantly more common in HGSCs with ovarian parenchymal involvement compared with those limited to the fallopian tube and/or extraovarian tissues. These associations suggest geographically different tumor growth patterns and support the subdivision of HGSCs according to not only the stage but also tumor distribution. They have implications for clinical and pathologic presentation, trajectory of tumor evolution, and in the case of primary peritoneal HGSCs, potentially unique precursors to tumor transitions that could inform or influence cancer prevention efforts.

Inflammatory Activity of Epithelial Stem Cell Variants from Cystic Fibrosis Lungs Is Not Resolved by CFTR Modulators

Rationale: CFTR (cystic fibrosis transmembrane conductance regulator) modulator drugs restore function to mutant channels in patients with cystic fibrosis (CF) and lead to improvements in body mass index and lung function. Although it is anticipated that early childhood treatment with CFTR modulators will significantly delay or even prevent the onset of advanced lung disease, lung neutrophils and inflammatory cytokines remain high in patients with CF with established lung disease despite modulator therapy, underscoring the need to identify and ultimately target the sources of this inflammation in CF lungs. Objectives: To determine whether CF lungs, like chronic obstructive pulmonary disease (COPD) lungs, harbor potentially pathogenic stem cell "variants" distinct from the normal p63/Krt5 lung stem cells devoted to alveolar fates, to identify specific variants that might contribute to the inflammatory state of CF lungs, and to assess the impact of CFTR genetic complementation or CFTR modulators on the inflammatory variants identified herein. Methods: Stem cell cloning technology developed to resolve pathogenic stem cell heterogeneity in COPD and idiopathic pulmonary fibrosis lungs was applied to end-stage lungs of patients with CF (three homozygous CFTR:F508D, one CFTR F508D/L1254X; FEV1, 14-30%) undergoing therapeutic lung transplantation. Single-cell-derived clones corresponding to the six stem cell clusters resolved by single-cell RNA sequencing of these libraries were assessed by RNA sequencing and xenografting to monitor inflammation, fibrosis, and mucin secretion. The impact of CFTR activity on these variants after CFTR gene complementation or exposure to CFTR modulators was assessed by molecular and functional studies. Measurements and Main Results: End-stage CF lungs display a stem cell heterogeneity marked by five predominant variants in addition to the normal lung stem cell, of which three are proinflammatory both at the level of gene expression and their ability to drive neutrophilic inflammation in xenografts in immunodeficient mice. The proinflammatory functions of these three variants were unallayed by genetic or pharmacological restoration of CFTR activity. Conclusions: The emergence of three proinflammatory stem cell variants in CF lungs may contribute to the persistence of lung inflammation in patients with CF with advanced disease undergoing CFTR modulator therapy.

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

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

Prevalence and genotype distribution of human papillomavirus in cervical adenocarcinoma (usual type and variants): A systematic review and meta-analysis

Cervical glandular neoplasms represent a heterogeneous group of tumors for which a comprehensive overview of the involvement of high-risk human papillomaviruses (HPV) in pathogenesis is still lacking. We first searched MEDLINE (PubMed), Embase, and Scopus databases (until October 2022), and systematically reviewed available literature. We then quantitatively estimated both pooled and genotype-specific prevalence of HPV DNA as well as the influence of various factors (e.g., geographical region, histological subtype, tissue/sample type) on computed effect size by means of random effects meta-analysis. In total, 379 studies comprising 17 129 cases of cervical adenocarcinoma were identified. The pooled HPV prevalence was 78.4% (95% confidence interval [95% CI]: 76.2-80.3) with a significant between-study heterogeneity (I2  = 79.4%, Q test p < 0.0001). Subgroup analyses indicated that the effect size differed substantially by geographical region (from 72.5% [95% CI: 68.7-76.1] in Asia to 86.8% [95% CI: 82.2-90.3] in Oceania) (p < 0.0001) and histological subtype of cancer (from 9.8% [95% CI: 5.5-17] in gastric-type to 85% [95% CI: 79.6-89.2] in usual-type cervical adenocarcinoma) (p < 0.0001). HPV16 and HPV18 were by far the most frequently detected viral strains with specific prevalence of 49.8% (95% CI: 46.9-52.6) and 45.3% (95% CI: 42.8-47.8), respectively. When stratified by continent or histologic variant, these genotype-specific results varied in a relatively limited manner. Altogether, these findings support that all histological subtypes of cervical adenocarcinoma are etiologically linked to high-risk HPV but to varying degrees. Therefore, a dual-criteria classification taking into account accurately both morphological and virological aspects could be an interesting evolution of the current binary World Health Organization classification, better reflecting the pathogenic diversity of the disease.

Inaugurating High-Throughput Profiling of Extracellular Vesicles for Earlier Ovarian Cancer Detection

Detecting early cancer through liquid biopsy is challenging due to the lack of specific biomarkers for early lesions and potentially low levels of these markers. The current study systematically develops an extracellular-vesicle (EV)-based test for early detection, specifically focusing on high-grade serous ovarian carcinoma (HGSOC). The marker selection is based on emerging insights into HGSOC pathogenesis, notably that it arises from precursor lesions within the fallopian tube. This work thus establishes murine fallopian tube (mFT) cells with oncogenic mutations and performs proteomic analyses on mFT-derived EVs. The identified markers are then evaluated with an orthotopic HGSOC animal model. In serially-drawn blood of tumor-bearing mice, mFT-EV markers increase with tumor initiation, supporting their potential use in early cancer detection. A pilot clinical study (n = 51) further narrows EV markers to five candidates, EpCAM, CD24, VCAN, HE4, and TNC. The combined expression of these markers distinguishes HGSOC from non-cancer with 89% sensitivity and 93% specificity. The same markers are also effective in classifying three groups (non-cancer, early-stage HGSOC, and late-stage HGSOC). The developed approach, for the first time inaugurated in fallopian tube-derived EVs, could be a minimally invasive tool to monitor women at high risk of ovarian cancer for timely intervention.

Cloning a profibrotic stem cell variant in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive, irreversible, and rapidly fatal interstitial lung disease marked by the replacement of lung alveoli with dense fibrotic matrices. Although the mechanisms initiating IPF remain unclear, rare and common alleles of genes expressed in lung epithelia, combined with aging, contribute to the risk for this condition. Consistently, single-cell RNA sequencing (scRNA-seq) studies have identified lung basal cell heterogeneity in IPF that might be pathogenic. We used single-cell cloning technologies to generate "libraries" of basal stem cells from the distal lungs of 16 patients with IPF and 10 controls. We identified a major stem cell variant that was distinguished from normal stem cells by its ability to transform normal lung fibroblasts into pathogenic myofibroblasts in vitro and to activate and recruit myofibroblasts in clonal xenografts. This profibrotic stem cell variant, which was shown to preexist in low quantities in normal and even fetal lungs, expressed a broad network of genes implicated in organ fibrosis and showed overlap in gene expression with abnormal epithelial signatures identified in previously published scRNA-seq studies of IPF. Drug screens highlighted specific vulnerabilities of this profibrotic variant to inhibitors of epidermal growth factor and mammalian target of rapamycin signaling as prospective therapeutic targets. This profibrotic stem cell variant in IPF was distinct from recently identified profibrotic stem cell variants in chronic obstructive pulmonary disease and may extend the notion that inappropriate accrual of minor and preexisting stem cell variants contributes to chronic lung conditions.

Profiling extracellular vesicles in circulation enables the early detection of ovarian cancer

Ovarian cancer is a heterogeneous group of tumors in both cell type and natural history. While outcomes are generally favorable when detected early, the most common subtype, high-grade serous carcinoma (HGSOC), typically presents at an advanced stage and portends less favorable prognoses. Its aggressive nature has thwarted early detection efforts through conventional detection methods such as serum CA125 and ultrasound screening and thus inspired the investigation of novel biomarkers. Here, we report the systematic development of an extracellular-vesicle (EV)-based test to detect early-stage HGSOC. Our study is based on emerging insights into HGSOC biology, notably that it arises from precursor lesions within the fallopian tube before traveling to ovarian and/or peritoneal surfaces. To identify HGSOC marker candidates, we established murine fallopian tube (mFT) cells with oncogenic mutations in Brca1/2, Tp53 , and Pten genes, and performed proteomic analyses on mFT EVs. The identified markers were then evaluated with an orthotopic HGSOC animal model. In serially-drawn blood samples of tumor-bearing mice, mFT-EV markers increased with tumor initiation, supporting their potential use in early cancer detection. A pilot human clinical study ( n = 51) further narrowed EV markers to five candidates, EpCAM, CD24, VCAN, HE4, and TNC. Combined expression of these markers achieved high OvCa diagnostic accuracy (cancer vs. non-cancer) with a sensitivity of 0.89 and specificity of 0.93. The same five markers were also effective in a three-group classification: non-cancer, early-stage (I & II) HGSOC, and late-stage (III & IV) HGSOC. In particular, they differentiated early-stage HGSOC from the rest with a specificity of 0.91. Minimally invasive and repeatable, this EV-based testing could be a versatile and serial tool for informing patient care and monitoring women at high risk for ovarian cancer.

Molecular catastrophe, the peritoneal cavity and ovarian cancer prevention

The current theory of carcinogenesis for the deadliest of "ovarian" cancers - high-grade serous carcinoma (HGSC) - holds that the malignancy develops first in the fallopian tube and spreads to the ovaries, peritoneum and/or regional lymph nodes. This is based primarily on the observation of early forms of serous neoplasia (serous tubular intraepithelial lesions (STILs), and serous tubular intraepithelial carcinomas (STICS)) in the fimbria of women undergoing risk reduction surgery. However, these lesions are uncommon in the general population, confer a low risk (5%) of HGSC following their removal in at-risk women with germ-line BRCA1/2 mutations and require 4 or more years to recur as intraperitoneal HGSC. These features suggest that isolated STILs and STICs behave as precursors with uncertain cancer risk rather than carcinomas. Their evolution to HGSC after escape from the tube could proceed step-wise with multiple biologic events; however, it is unclear whether immediately adjacent HGSCs in the setting of advanced disease evolved in the same fashion. The latter scenario could also be explained by a "catastrophic" model in which STICs suddenly develop with invasive and metastatic potential, overwhelming or obscuring the site of origin. Moreover, a similar model might explain the sudden emergence of HGSC in the peritoneal cavity following escape of precursor cells years before. Long term follow-up data from opportunistic or prophylactic salpingectomy should shed light on where malignant transformation occurs, as well as the time-line from precursor to metastatic HGSC. This article is protected by copyright. All rights reserved.

Interobserver reproducibility of the diagnosis of differentiated exophytic vulvar intraepithelial lesion (DEVIL) and the distinction from its mimics

AIMS

Most vulvar squamous cell carcinomas are human papillomavirus (HPV)-associated or TP53-mutant. A third category of HPV-independent TP53-wild-type lesions is uncommon and not fully understood. Differentiated exophytic vulvar intraepithelial lesion (DEVIL) has been characterised as a precursor of this latter category. The reproducibility of the diagnosis of DEVIL and its distinction from lesions with overlapping morphology has not been studied. Our aim was to establish the interobserver agreement in the diagnosis of DEVIL and its distinction from neoplastic and reactive conditions of the vulva on haematoxylin and eosin evaluation.

METHODS AND RESULTS

A set of 35 slides was evaluated by eight reviewers (two trainees and six practising gynaecological pathologists). The set included DEVIL, condyloma, established vulvar precursors [high-grade squamous intraepithelial lesion (HSIL) and differentiated vulvar intraepithelial neoplasia (dVIN)] with superimposed acanthosis or verruciform growth, lichen simplex chronicus (LSC), and psoriasis. Kappa (κ) values were calculated. Overall, interobserver agreement was moderate (κ = 0.56), improving to substantial (κ = 0.7) when evaluation was performed by practising pathologists. Agreement was strong for the diagnosis of HSIL (κ = 0.88), and substantial for the diagnosis of DEVIL (κ = 0.61), condyloma (κ = 0.79), and LSC (κ = 0.72). Agreement was moderate for the diagnosis of dVIN (κ = 0.59) and psoriasis (κ = 0.53). Perfect agreement (6/6) among practising pathologists was observed in 43% of cases, and majority agreement (5/6 or 4/6) was observed in 48% of cases.

CONCLUSIONS

Reproducibility in the diagnosis of verruciform vulvar lesions, including the novel DEVIL, is acceptable overall. Reproducibility is higher for well-known lesions such as HSIL and condyloma than for more challenging diagnoses such as DEVIL, dVIN, and psoriasis. Agreement is higher among practising gynaecological pathologists, suggesting that training and experience improve reproducibility. Our findings support the inclusion of DEVIL as a diagnostic entity in the classification of vulvar squamous lesions.

Dissection of PIK3CA Aberration for Cervical Adenocarcinoma Outcomes

Simple Summary

There is limited information about genomic markers, especially for cervical adenocarcinoma treatment decisions. In this prospective study, it was found that nonsynonymous PIK3CA mutation detected in the patient’s circulating DNA collected before treatment or during follow-up was significantly associated with decreased progression-free survival or overall survival. It is the first indication of the predictive power of PIK3CA aberration in cervical adenocarcinoma. The work contributes to the development of liquid biopsies for the prolonged strategy of surveillance and indicates the possibility of tailoring management of this particular women’s cancer.

Abstract

Personalized treatment of genetically stratified subgroups has the potential to improve outcomes in many malignant tumors. This study distills clinically meaningful prognostic/predictive genomic marker for cervical adenocarcinoma using signature genomic aberrations and single-point nonsynonymous mutation-specific droplet digital PCR (ddPCR). Mutations in PIK3CA E542K, E545K, or H1047R were detected in 41.7% of tumors. PIK3CA mutation detected in the patient’s circulating DNA collected before treatment or during follow-up was significantly associated with decreased progression-free survival or overall survival. PIK3CA mutation in the circulating DNA during follow-up after treatment predicted recurrence with 100% sensitivity and 64.29% specificity. It is the first indication of the predictive power of PIK3CA mutations in cervical adenocarcinoma. The work contributes to the development of liquid biopsies for follow up surveillance and a possibility of tailoring management of this particular women’s cancer.

Enhanced Efficacy of Aurora Kinase Inhibitors in G2/M Checkpoint Deficient TP53 Mutant Uterine Carcinomas Is Linked to the Summation of LKB1-AKT-p53 Interactions

Simple Summary

Cancers arising from the lining of the uterus, endometrial cancers, are the most common gynecologic malignancy in the United States. Once endometrial cancer escapes the uterus and grows in distant locations, there are limited therapeutic options. The most aggressive and lethal endometrial cancers carry alterations in the protein p53, which is a critical guardian of many cellular functions. The role of these p53 alterations in endometrial cancer is not well understood. The goal of this work was to use p53 altered models of endometrial cancer to understand which, if any, therapeutically targetable vulnerabilities these p53 alterations may confer in endometrial cancer. Here we show that many of these p53 altered cells have problems with cell division which can be targeted with novel single and combination therapies. These discoveries may lead to relevant new therapies for difficult to treat advanced stage endometrial cancers.

Abstract

Uterine carcinoma (UC) is the most common gynecologic malignancy in the United States. TP53 mutant UCs cause a disproportionate number of deaths due to limited therapies for these tumors and the lack of mechanistic understanding of their fundamental vulnerabilities. Here we sought to understand the functional and therapeutic relevance of TP53 mutations in UC. We functionally profiled targetable TP53 dependent DNA damage repair and cell cycle control pathways in a panel of TP53 mutant UC cell lines and patient-derived organoids. There were no consistent defects in DNA damage repair pathways. Rather, most models demonstrated dependence on defective G2/M cell cycle checkpoints and subsequent upregulation of Aurora kinase-LKB1-p53-AKT signaling in the setting of baseline mitotic defects. This combination makes them sensitive to Aurora kinase inhibition. Resistant lines demonstrated an intact G2/M checkpoint, and combining Aurora kinase and WEE1 inhibitors, which then push these cells through mitosis with Aurora kinase inhibitor-induced spindle defects, led to apoptosis in these cases. Overall, this work presents Aurora kinase inhibitors alone or in combination with WEE1 inhibitors as relevant mechanism driven therapies for TP53 mutant UCs. Context specific functional assessment of the G2/M checkpoint may serve as a biomarker in identifying Aurora kinase inhibitor sensitive tumors.

Mural nodules in mucinous ovarian tumors represent a morphologic spectrum of clonal neoplasms: a morphologic, immunohistochemical, and molecular analysis of 13 cases

Mucinous ovarian tumors rarely harbor mural nodules, which have historically been classified as sarcoma-like, anaplastic carcinomatous, or sarcomatous on the basis of predominant morphologic features. The molecular relationship between mural nodules and associated mucinous ovarian tumors remains poorly characterized, as does the molecular pathogenesis of these mural nodules. Thus, we analyzed the morphological, immunohistochemical, and genetic features of 13 mucinous ovarian tumors and associated mural nodule(s). Three harbored sarcoma-like mural nodules and ten contained anaplastic carcinomatous nodules, including 1 tumor with spatially discrete anaplastic carcinomatous and sarcomatous nodules. Twelve of 13 cases showed genetic evidence of clonality between the mural nodule(s) and associated mucinous ovarian tumor, including all three tumors with sarcoma-like morphology. Mural nodules were genetically identical in the five cases in which there were multiple discrete mural nodules that were sequenced separately. MTAP and p53 immunohistochemistry confirmed the distribution of neoplastic cells in a subset of sarcoma-like and anaplastic carcinomatous nodules. No single recurrent genetic alteration was associated with mural nodule development. No recurrent genetic differences were identified between mural nodules with sarcoma-like, anaplastic carcinomatous, and sarcomatous morphology. Of 11 patients with clinical follow-up, three died of disease 3, 8, and 9 months after diagnosis, but no recurrent genetic events were associated with poor outcome. These molecular data suggest that sarcoma-like, anaplastic carcinomatous, and sarcomatous nodules represent a morphologic spectrum of clonal neoplasms arising in mucinous ovarian tumors rather than three discrete biological entities.

Enhanced Efficacy of Simultaneous PD-1 and PD-L1 Immune Checkpoint Blockade in High-Grade Serous Ovarian Cancer

Immune therapies have had limited efficacy in high-grade serous ovarian cancer (HGSC), as the cellular targets and mechanism(s) of action of these agents in HGSC are unknown. Here we performed immune functional and single-cell RNA sequencing transcriptional profiling on novel HGSC organoid/immune cell co-cultures treated with a unique bispecific anti-programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) antibody compared with monospecific anti-PD-1 or anti-PD-L1 controls. Comparing the functions of these agents across all immune cell types in real time identified key immune checkpoint blockade (ICB) targets that have eluded currently available monospecific therapies. The bispecific antibody induced superior cellular state changes in both T and natural killer (NK) cells. It uniquely induced NK cells to transition from inert to more active and cytotoxic phenotypes, implicating NK cells as a key missing component of the current ICB-induced immune response in HGSC. It also induced a subset of CD8 T cells to transition from naïve to more active and cytotoxic progenitor-exhausted phenotypes post-treatment, revealing the small, previously uncharacterized population of CD8 T cells responding to ICB in HGSC. These state changes were driven partially through bispecific antibody-induced downregulation of the bromodomain-containing protein BRD1. Small-molecule inhibition of BRD1 induced similar state changes in vitro and demonstrated efficacy in vivo, validating the co-culture results. Our results demonstrate that state changes in both NK and a subset of T cells may be critical in inducing an effective anti-tumor immune response and suggest that immune therapies able to induce such cellular state changes, such as BRD1 inhibitors, may have increased efficacy in HGSC. SIGNIFICANCE: This study indicates that increased efficacy of immune therapies in ovarian cancer is driven by state changes of NK and small subsets of CD8 T cells into active and cytotoxic states.

Molecular characterization of diffuse malignant peritoneal mesothelioma

Malignant peritoneal mesothelioma is a rare aggressive tumor that arises from the peritoneal lining. While recurrent BAP1 mutations have been identified in a subset of mesotheliomas, molecular characteristics of peritoneal mesotheliomas, including those lacking BAP1 alterations, remain poorly understood. Using targeted next-generation sequencing, we examined the molecular features of 26 diffuse malignant peritoneal mesotheliomas. As part of an exploratory analysis, we analyzed an additional localized peritoneal mesothelioma and one well-differentiated papillary mesothelioma with invasive foci. Genomic characterization identified categories of diffuse malignant peritoneal mesotheliomas: The first group included 18 (69%) tumors with recurrent BAP1 alterations, with eight (31%) having more than one BAP1 alterations, and concomitant alterations in PBRM1 (46%) and SETD2 (35%). All tumors with complete loss of BAP1 expression by immunohistochemistry harbored BAP1 molecular alterations. PBRM1 alterations were significantly enriched in the BAP1-altered cohort. Frequent copy number loss of BAP1, ARID1B, PRDM1, PBRM1, SETD2, NF2, and CDKN2A was noted. The second group included eight (31%) BAP1-wild-type tumors: two with TP53 mutations, one with a TRAF7 activating mutation, one with a SUZ12 inactivating mutation, and three with ALK rearrangements that we previously published. One TP53-mutant biphasic mesothelioma showed evidence of genomic near-haploidization showing loss of heterozygosity of all chromosomes except 5, 7, 16, and 20. The localized peritoneal mesothelioma harbored a nonsense CHEK2 mutation, and the well-differentiated papillary mesothelioma with invasive foci harbored no reportable variants. In conclusion, we described the genetic categories of diffuse malignant peritoneal mesotheliomas, with BAP1-mutant and BAP1-wild-type groups. Our findings implicated DNA repair, epigenetics, and cell cycle regulation in the pathogenesis of peritoneal mesotheliomas, with identification of potential therapeutic targets.

Abstract PR06: Dissecting mechanisms of replication fork stabilization in patient-derived high-grade serous organoid cultures and their impact on therapeutic sensitivity and the immune-tumor interaction

Genomic analyses indicate that 50% of high-grade serous ovarian cancers (HGSC) harbor a genomic alteration in a DNA damage repair gene that may lead to functional defects. Using functional assays on patient-derived HGSC organoid cultures to test the capacity of the tumor cells to repair double-strand DNA breaks and to protect stalled replication forks, we have found that many HGSCs have stalled fork protection defects regardless of the genomic background of the tumor and that these defects correlate with sensitivity to replication stress inducing therapeutic agents. We hypothesized that gaining a better understanding of the mechanisms of replication fork instability and stability in HGSC organoid cultures would help to better understand the mechanisms of therapeutic sensitivity of the tumor cells. The purpose of this work is to understand how replication fork stabilization either in the primary tumor or through selection post-treatment leads to alterations in tumor cell biology, including therapeutic sensitivity and interaction of the tumor cells with the surrounding microenvironment. We utilized bulk RNA sequencing analysis of HGSC organoid cultures with varied replication fork protection capacity, some matched pairs of untreated and post-neoadjuvant tumors, to stratify differences in functional profiles in fork stable versus unstable tumors; we then used basic molecular biology techniques to understand the mechanisms of fork stabilization and how this stabilization affects the therapeutic sensitivity of the cells. We also developed and utilized multiple functional assays to assess the interaction of HGSC organoids of varying fork protection capacity with their immune microenvironment in different drug exposure settings. We identified multiple proteins that through either up- or downregulation lead to stabilization of replication forks in the tumor cells and found that the mechanisms of stabilization can occur at both the level of the replication fork and the overall transcriptional level of the cell and can alter the therapeutic sensitivity of the cells. We have determined that replication fork stability leads to increased mesenchymal characteristics in tumors and to decreased activation of the antitumor immune response within the cultures after treatment with DNA damage repair and immuno-oncologic (IO) agents. Overall, these results indicate that replication fork stabilization in HGSC through multiple different mechanisms can lead to altered interactions of the tumor cells with their microenvironment and altered therapeutic sensitivity.

This abstract is also being presented as Poster B10.

Citation Format: Sarah J. Hill, Patrick Lizotte, Nikolas Kesten, Neil S. Horowitz, Michael G. Muto, Michael J. Worley, Colleen M. Feltmate, Ross S. Berkowitz, Henry Long, Ursula A. Matulonis, Christopher P. Crum, Myles Brown, Alan D. D'Andrea. Dissecting mechanisms of replication fork stabilization in patient-derived high-grade serous organoid cultures and their impact on therapeutic sensitivity and the immune-tumor interaction [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research; 2019 Sep 13-16, 2019; Atlanta, GA. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(13_Suppl):Abstract nr PR06.

Regenerative Metaplastic Clones in COPD Lung Drive Inflammation and Fibrosis

Chronic obstructive pulmonary disease (COPD) is a progressive condition of chronic bronchitis, small airway obstruction, and emphysema that represents a leading cause of death worldwide. While inflammation, fibrosis, mucus hypersecretion, and metaplastic epithelial lesions are hallmarks of this disease, their origins and dependent relationships remain unclear. Here we apply single-cell cloning technologies to lung tissue of patients with and without COPD. Unlike control lungs, which were dominated by normal distal airway progenitor cells, COPD lungs were inundated by three variant progenitors epigenetically committed to distinct metaplastic lesions. When transplanted to immunodeficient mice, these variant clones induced pathology akin to the mucous and squamous metaplasia, neutrophilic inflammation, and fibrosis seen in COPD. Remarkably, similar variants pre-exist as minor constituents of control and fetal lung and conceivably act in normal processes of immune surveillance. However, these same variants likely catalyze the pathologic and progressive features of COPD when expanded to high numbers.

Cloning of ground-state intestinal stem cells from endoscopic biopsy samples

'Adult' or 'somatic' stem cells harbor an intrinsic ability to regenerate tissues. Heterogeneity of such stem cells along the gastrointestinal tract yields the known segmental specificity of this organ and may contribute to the pathology of certain enteric conditions. Here we detail technology for the generation of 'libraries' of clonogenic cells from 1-mm-diamter endoscopic biopsy samples from the human gastrointestinal tract. Each of the 150-300 independent clones in a typical stem cell library can be clonally expanded to billions of cells in a few weeks while maintaining genomic stability and the ability to undergo multipotent differentiation to the specific epithelia from which the sample originated. The key to this methodology is the intrinsic immortality of normal intestinal stem cells (ISCs) and culture systems that maintain them as highly immature, ground-state ISCs marked by a single-cell clonogenicity of 70% and a corresponding 250-fold proliferative advantage over spheroid technologies. Clonal approaches such as this enhance the resolution of molecular genetics, make genome editing easier, and may be useful in regenerative medicine, unravelling heterogeneity in disease, and facilitating drug discovery.

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

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

Abstract NT-115: PRE-EXISTENCE OF POLY-RESISTANT CANCER STEM CELLS IN HIGH-GRADE OVARIAN CANCER

INTRODUCTION: High-grade ovarian cancer (HGOC) shows excellent responses to standard-of-care surgery and paclitaxel/carboplatin therapy only to relapse 6-24 months later with typically resistant disease. While the origin of this recurrent, resistant disease is unclear, most believe it is acquired by the action of chemotherapeutics. Using novel stem cell technology that enables the cloning of cancer stem cells (CSCs) from epithelial cancers, we have generated large libraries of CSCs from multiple cases of HGOC. And while the vast majority of these CSC clones are killed by standard-of-care chemotherapeutic drugs, a minor fraction shows profound resistance not only to paclitaxel/carboplatin but to a wide range of structurally unrelated chemotherapeutic drugs to which these cells had no prior exposure. We describe screens for drugs that selectively target this resistant CSC population.

METHODS: Libraries of 10- to 100,000 CSC clones were generated from individual, therapy naïve, HGOC resections using technology we developed for cloning so-called “adult” stem cells from normal columnar epithelia (Wang et al., 2015, Nature, 522, 173).

RESULTS: Paclitaxel/carboplatin resistant CSCs were identified in CSC libraries derived from therapy naïve tumors at ratios of 1:50 to 1:300. By copy number variation, these resistant variant clones proved distinct from the bulk of CSCs, and by gene expression analysis varied from sensitive clones by more than 700 differentially expressed genes. Independent resistant clones from the same library clustered with other resistant clones by both copy number variation and gene expression profiles, suggesting the possibility that resistance within a single tumor is dominated by a single type of resistant CSCs. Clones resistant to paclitaxel/carboplatin were screened in a 384-well format against a wide range of experimental drug-like molecules. These pre-existing resistant clones also proved to be profoundly resistant to a large number of structurally unrelated chemotherapeutic drugs. This same screening program identified drugs that act alone or in combination with paclitaxel to eliminate these resistant clones, suggesting a route to personalized medicine for addressing the problem of recurrent disease in HGOC.

CONCLUSIONS: Tumors from patients with HGOC possess clonogenic CSCs including variants that are resistant to a broad spectrum of chemotherapeutics to which they have not been exposed. It is likely that such CSCs would survive standard-of-care chemotherapy and contribute to the recurrent disease seen in HGOC. We have identified known and experimental drugs that specifically eliminate these resistant variants and the overall platform represents a potential strategy to addressing the problem of recurrent disease in these patients.

Citation Format: Jingzhong Xie, Yusuke Yamamoto, Marcin Duleba, Bailiang Wang, Rajasekaran Mahalingam, Shan Wang, Wei Rao, Suchan Niroula, Clifford Stephan, Peter Davies, Amir Jazaeri, Giulio Draetta, Molly Brewer, Matt L. Anderson, Christopher P. Crum, Frank McKeon, and Wa Xian. PRE-EXISTENCE OF POLY-RESISTANT CANCER STEM CELLS IN HIGH-GRADE OVARIAN CANCER [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr NT-115.

Abstract AP10: REAL-TIME ASSESSMENT OF HGSC DNA DAMAGE REPAIR DEFECTS AND DEFECT-INDUCED RESPONSE TO THERAPY IN OVARIAN CANCER ORGANOIDS

Patients with High Grade Serous Ovarian Cancer (HGSC) have limited therapeutic options. Immuno-oncologic (IO) agents have had limited effect. DNA damage repair gene mutations that may confer repair defects have been identified in up to 50% of HGSCs, making therapies that target repair defects, like PARP, CHK1, and ATR inhibitors, additional options. We have no means of predicting which patients will respond to any of these therapies.

A model system that allows for functional assays to assess for DNA damage repair defects, prediction of response to therapies targeting such defects, and assessment of the functionality of the tumor immune infiltrate and its response to IO agents is needed. Organoids are three-dimensional structures derived from human normal or tumor tissue cells that anatomically and functionally mimic the developed human organ. Organoids mimicking the parent tumor from which they were derived have aided in the study of multiple tumor types. They are inexpensive and easily manipulated and may be an ideal model system for studying ovarian cancer.

We have devised a functional assay platform to profile the DNA damage repair capacity and immune targetability of short-term patient-derived HGSC organoids. The organoids mimic the tumors from which they were derived morphologically, molecularly, and genetically.

We have tested 33 organoid cultures derived from 21 HGSC patients for homologous recombination (HR) and replication fork protection capacity and compared the functional results to the tumor genomic profile. Regardless of repair gene mutational status, an HR functional defect in the organoids correlated with PARP inhibitor sensitivity. A fork protection functional defect correlated with carboplatin, and ATR and CHK1 inhibitor sensitivity. Importantly, this work has led to the discovery of potential therapeutic combinations, such as a CHK1 inhibitor plus carboplatin or gemcitabine that may be useful in treating tumors otherwise resistant to most therapies. Drugs such as carboplatin or gemcitabine can synergize with a CHK1 inhibitor by enhancing replication stress and fork deprotection.

In parallel, we have immune phenotyped the parent tumors and organoid cultures from 15 patients, and shown that the organoid cultures retain lymphocytes expressing relevant IO receptors in the short term. Upon treatment with carboplatin, olaparib, and pembrolizumab as single agents or in combination, we detect changes in IO receptor expression and production of different cytokines in the cultures, suggesting an immune response induced by these agents. We have detected receptor and cytokine alterations that would create an immune suppressive environment with specific drug combinations in tumors with specific repair defects, suggesting that these may be inappropriate combinations for harnessing the immune system in tumors with specific repair capacities.

Continued combined immune and DNA damage repair phenotyping analyses of the organoids will lead to a better understanding of which mechanistic defects are needed to confer sensitivity to DNA damage repair agents, what functional properties and immune milieu lead to sensitivity to IO agents, and how best to combine such therapies. In addition, through further correlation with patient responses over time, HGSC organoids may become a useful tool for rapidly predicting patient response to therapeutic agents.

Citation Format: Sarah J. Hill, Brennan Decker, Emma A. Roberts, Chunyu Yang, Neil S. Horowitz, Michael G. Muto, Michael J. Worley Jr., Colleen M. Feltmate, Marisa R. Nucci, Elizabeth M. Swisher, Ryuji Morizane, Bose Kochupurakkal, Khanh T. Do, Panagiotis Konstantinopoulos, Joyce F. Liu, Joseph V. Bonventre, Ursula A. Matulonis, Geoffrey I. Shapiro, Ross S. Berkowitz, Christopher P. Crum, and Alan D. D'Andrea. REAL-TIME ASSESSMENT OF HGSC DNA DAMAGE REPAIR DEFECTS AND DEFECT-INDUCED RESPONSE TO THERAPY IN OVARIAN CANCER ORGANOIDS [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr AP10.

Identification of ALK Rearrangements in Malignant Peritoneal Mesothelioma

Importance

Malignant peritoneal mesothelioma is a rare, aggressive tumor arising from the peritoneal lining, induced by asbestos, therapeutic radiation, or germline mutations. Nevertheless, the molecular features remain largely unknown.

Objective

To investigate anaplastic lymphoma kinase (ALK) rearrangements in a large series of peritoneal mesothelioma and characterize the mutational landscape of these tumors.

Design, Setting, and Participants

We studied 88 consecutive patients (39 men, 49 women; median age 61, range 17-84 years) with peritoneal mesotheliomas diagnosed at a single institution between 2005 and 2015. We identified ALK-positive mesotheliomas by immunohistochemistry and confirmed ALK rearrangement by fluorescence in situ hybridization (FISH). In ALK-rearranged cases, we characterized the fusion partners using targeted next-generation sequencing of both tumor DNA and RNA. In select cases, we quantified asbestos fibers by combined scanning electron microscopy and x-ray spectroscopy. We also explored ALK rearrangement in a separate series of 205 patients with pleural mesothelioma.

Main Outcomes and Measures

Identification and characterization of novel ALK rearrangements and correlations with clinicopathologic characteristics.

Results

Anaplastic lymphoma kinase was positive by immunohistochemistry in 11 (13%) peritoneal mesotheliomas (focal weak in 8, diffuse strong in 3). In focal weak ALK-positive cases, no ALK rearrangement was detected by FISH or next-generation sequencing. In strong diffuse ALK-positive cases, FISH confirmed ALK rearrangements, and next-generation sequencing identified novel fusion partners ATG16L1, STRN, and TPM1. Patients with ALK-rearranged peritoneal mesotheliomas were women and younger than patients without ALK rearrangement (median age 36 vs 62; Mann-Whitney test, P = .02), but all other clinicopathologic characteristics (size of tumor nodules, histology, treatment, and survival) were not different. No asbestos fibers were detected in ALK-rearranged cases. Furthermore, loss of chromosomal region 9p or 22q or genetic alterations in BAP1, SETD2, or NF2 typically present in peritoneal mesothelioma were absent in the ALK-rearranged cases. All pleural mesotheliomas were ALK-negative by immunohistochemistry.

Conclusions and Relevance

We identified unique ALK rearrangements in a subset of patients with peritoneal mesothelioma, each lacking asbestos fibers, therapeutic radiation, and cytogenetic and molecular alterations typically found in these tumors. Identification of clinically actionable ALK rearrangements may represent a novel pathogenetic mechanism of malignant peritoneal mesothelioma with promise for targeted therapy.

Abstract 368A: Functional assessment of DNA damage repair defects and the anti-tumor immune response in high grade serous ovarian cancers using patient-derived organoids

Patients with high grade serous ovarian cancer (HGSC) have limited additional therapeutic options beyond traditional carboplatin and paclitaxel. Immuno-oncologic (IO) agents have had limited effect, and despite the fact that 50% of HGSCs have genomic alterations in DNA damage repair genes, we still have no means of predicting which of these tumors actually harbor repair defects and will respond to these agents. Using patient-derived organoids which contain patient immune cells, we have developed functional assays to test the DNA damage repair capacity, anti-tumor immune response, and therapeutic vulnerability of HGSCs. These assays include testing for defects in the two key DNA damage repair pathways, homologous recombination (HR) and stalled replication fork protection, testing for activity and specificity of the immune cells in the cultures against the tumor cells when exacerbated by specific therapeutic combinations, and testing for therapeutic sensitivity to targeted and traditional chemotherapy agents and IO agents either alone or in rational combinations. In parallel, many of the tumors and organoids have undergone genomic and RNA sequencing, searching for relevant alterations to explain detected defects. Flow cytometry analysis of the parent tumors and short term (7-10 day) organoids reveal that organoids contain an immune milieu with IO receptor expression levels similar to the parent tumors. Upon treatment with IO agents alone or in combination with chemotherapeutic agents, we have found that specific IO receptor expression is altered, certain combinations lead to induction of cytokine expression that may repress an anti-tumor response, and that some combinations do not induce the expected cytotoxicity. The DNA damage repair functional assays have revealed that in HGSC, stalled fork protection defects are more common than HR defects, regardless of the repair gene mutational status of the tumors. Importantly, there is a wider array of therapies available to target these defects. For instance, organoids with unstable replication forks are more sensitive to ATR and CHK1 inhibitors. Organoids with stable forks are more sensitive to combinations of drugs which confer replication stress, such as the combination of a CHK1 inhibitor plus gemcitabine. Overall, the repair assays will allow for a better understanding of the types and mechanisms of repair defects present in tumors and a more accurate prediction of sensitivity to targeted agents. The immune functional assays will allow for a better mechanistic understanding of what response specific agents actually induce in immune and tumor cells and allow for better rational therapeutic pairings. Through assessment of a larger number of patients, we hope to demonstrate that these functional assays can have a clinical impact in rapidly predicting patient response.

Citation Format: Sarah J. Hill, Patrick Lizotte, Neil S. Horowitz, Michael G. Muto, Michael J. Worley, Colleen M. Feltmate, Bose Kochupurakkal, Khanh T. Do, Panagiotis Konstantinopoulos, Marisa R. Nucci, Joyce F. Liu, Ursula A. Matulonis, Geoffrey I. Shapiro, Ross S. Berkowitz, Christopher P. Crum, Alan D. D'Andrea. Functional assessment of DNA damage repair defects and the anti-tumor immune response in high grade serous ovarian cancers using patient-derived organoids [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 368A.

Classic Vulvar Intraepithelial Neoplasia With Superimposed Lichen Simplex Chronicus: A Unique Variant Mimicking Differentiated Vulvar Intraepithelial Neoplasia

High-grade vulvar intraepithelial neoplasia, a precursor lesion to vulvar squamous cell carcinoma, is subdivided into 2 types, classic or usual vulvar intraepithelial neoplasia (CVIN) and differentiated vulvar intraepithelial neoplasia (DVIN). CVIN, which is a human papilloma virus (HPV)-dependent lesion, is typically distinguished from DVIN, a p53 mutation-dependent process, by its distinct histomorphologic and immunohistochemical characteristics. However, distinguishing between the 2 entities becomes challenging in cases of CVIN with superimposed inflammatory changes, especially lichen simplex chronicus (LSC). Twelve cases of DVIN, 9 cases of LSC, and 9 cases of CVIN with superimposed LSC were assessed for a number of morphologic features, including hyperkeratosis, hypergranulosis, acanthosis, hypercellularity, abnormal maturation (i.e. abnormal keratinization close to the base and/or dyskeratosis), hyperchromasia, and basal atypia. Immunohistochemistry for p53, p16, and MIB-1 was performed for all cases. When sufficient tissue was available, HPV genotyping was performed for cases of CVIN with superimposed LSC. DVIN uniformly demonstrated abnormal maturation, and atypia involving the basal cell layer; they were all p16 negative and demonstrated p53 positivity of moderate to strong intensity in a basal and parabasal distribution. CVIN with superimposed LSC frequently displayed hyperchromasia involving the basal 3 to 4 cell layers, basal to full-thickness atypia, and apoptosis. CVIN with superimposed LSC demonstrated intense p16 positivity extending from the basal cells to the mid-epithelium and a reduction or loss of staining in maturing keratinocytes. P53 staining revealed a unique pattern of parabasal and mid-epithelial weak to moderate staining with sparing of the basal layer. Cases of LSC demonstrated heterogenous p53 positivity and were negative for p16. MIB-1 staining showed a similar range of positivity for all diagnoses. HPV genotyping revealed HPV 16 in all 5 cases of CVIN with LSC that underwent testing. We conclude that, although CVIN with superimposed LSC can closely resemble DVIN, morphologic features such as nuclear hyperchromasia uniformly involving the basal 3 to 4 cell layers, apoptosis, and absent or less pronounced cytoplasmic maturation are more suggestive of CVIN with superimposed LSC. In cases where the morphology remains ambiguous, immunohistochemistry for both p16 and p53 can be helpful. In particular, p53 parabasal and mid-epithelial staining without involvement of the basal layer appears to be a characteristic finding in CVIN with superimposed LSC. MIB-1 staining is of little utility in distinguishing between these entities and should not be routinely performed.

Frontiers in the Pathology and Pathogenesis of Ovarian Cancer: Cancer Precursors and "Precursor Escape"

This article summarizes the pathogenesis of ovarian carcinoma, focusing on the paradox of high-grade serous carcinogenesis. The fallopian tube is the prime site of origin in early serous cancers. Because a subset of serous cancers is associated with early serous proliferations absent intramucosal carcinomas, "precursor escape" is emerging, whereby some advanced cancers trace their roots to early serous proliferations. This has parallels in the endometriosis model and opens up a novel mechanism by which advanced malignancy could emerge without an obvious tubal carcinoma. The impact of this concept on classification of serous cancer and expectations from preventive strategies are discussed.

Guidelines to Aid in the Distinction of Endometrial and Endocervical Carcinomas, and the Distinction of Independent Primary Carcinomas of the Endometrium and Adnexa From Metastatic Spread Between These and Other Sites

In most cases of suspected endometrial neoplasia tumor origin can be correctly assigned according to a combination of clinical, radiologic, and pathologic features, even when the latter are based upon the examination of relatively small biopsy samples. However there are well-recognized exceptions to this rule which continue to create diagnostic difficulty, and sometimes difficulties persist even after the detailed examination of resection specimens. Among the most common problems encountered in practice are the distinction of primary endometrial and primary endocervical adenocarcinomas, and the determination of tumor origin when there is synchronous, multifocal involvement of gynecologic tract sites, for example the endometrium and the ovary. However, accurate diagnosis in these cases is important because this has significant staging, management and prognostic implications. In this review we discuss the value and limitations of key morphologic, immunophenotypic and molecular findings in these diagnostic scenarios.

The fallopian tube, "precursor escape" and narrowing the knowledge gap to the origins of high-grade serous carcinoma

Most ovarian carcinomas are high-grade serous carcinomas (HGSC) that contain TP53 mutations, present at advanced stage, and eventually become resistant to chemotherapy. The rapid evolution of this disease has been attributed to an origin in the distal fallopian tube, in the form of serous tubal intraepithelial carcinomas (STICs). This has led to a disease model where malignancy develops first in the tube and spreads to the peritoneum or regional lymph nodes. However, although most early or incidentally discovered HGSCs manifest in the tube with STICs, many advanced HGSCs are not accompanied by a malignancy in the fimbria. To resolve this paradox, the focus has shifted to earlier, premalignant serous proliferations (ESPs) in the tubes, which lack the cytomorphologic features of malignancy but contain TP53 mutations. These have been termed p53 signatures or serous tubal intraepithelial lesions (STILs). Although they have not been presumed to have cancer-causing potential by themselves, some ESPs have recently been shown to share identical TP53 mutations with concurrent HGSCs, indicating a shared lineage between these early mucosal changes and metastatic malignancy. This discovery supports a paradigm by which HGSCs can emerge not only from STICs but also from exfoliated precursor cells (precursor escape) that eventually undergo malignant transformation within the peritoneal cavity. This paradigm unifies both localized and widespread HGSCs to a visible pre-existing cellular alteration in the tubal epithelium, and highlights a consistent and necessary biologic event (TP53 mutation) rarely encountered in the ovary or secondary Mullerian system. This dual pathway to HGSCs underscores the subtle nature of many serous cancer origins in the tube, explains contrasting clinico-pathologic presentations, and explains why, until recently, the fallopian tube was unappreciated as the principal origin of HGSCs. Moreover, it highlights additional challenges faced in preventing or intercepting HGSCs at a curable stage.

Back to the Future? The Fallopian Tube, Precursor Escape and a Dualistic Model of High-Grade Serous Carcinogenesis

Beginning with the discovery of the BRCA-associated ovarian cancer susceptibility genes and subsequent detailed examination of risk-reducing salpingo-oophorectomy (RRSO) specimens, a new paradigm of ovarian carcinogenesis has unfolded with attention to the distal fallopian tube. The primary focus has been an early cancer or neoplasm in the fallopian tube which is seen in virtually all incidentally discovered high-grade serous cancers in asymptomatic women. This high-frequency of tubal involvement in early serous neoplasm (usually in the form of serous tubal intraepithelial carcinoma—STIC) has galvanized attention to this organ as a primary source of this disease. However, an enduring mystery has been the relatively low frequency of STIC in the fallopian tubes of women with advanced malignancy. This paradox, a high frequency of tubal involvement early on and a low frequency of involvement later in the disease process, has spurred interest in other potential sources, such as the ovarian surface epithelium or cortical inclusions and the secondary Mullerian system. However, because essentially all high-grade serous carcinomas are linked by TP53 mutations, and because fallopian tubes frequently contain early serous proliferations (ESPs) with these mutations, attention has turned to the possibility that the nonmalignant but TP53 mutated tubal epithelium could be responsible for an eventual malignancy. Recent data have shown evidence of a lineage continuity between ESPs and concurrent serous carcinomas prompting the concept of “precursor escape”. This creates a second component of the paradigm by which cells from early precursors are shed from the tube and undergo subsequent malignant transformation, emerging suddenly as widespread intraperitoneal malignancy. This dualistic model thus provides a unique pathway by which the future outcome (wide spread high-grade serous carcinomas—HGSC) is ultimately explained by going back in time to an early serous proliferation. This paradigm also brings the peritoneal cavity into focus, raising new questions about the potential co-variables or exposures that might facilitate the occasional malignant transformation of an ESP in the peritoneal cavity or on the peritoneal surface.

Prediction of DNA Repair Inhibitor Response in Short-Term Patient-Derived Ovarian Cancer Organoids

Based on genomic analysis, 50% of high-grade serous ovarian cancers (HGSC) are predicted to have DNA repair defects. Whether this substantial subset of HGSCs actually have functional repair defects remains unknown. Here, we devise a platform for functional profiling of DNA repair in short-term patient-derived HGSC organoids. We tested 33 organoid cultures derived from 22 patients with HGSC for defects in homologous recombination (HR) and replication fork protection. Regardless of DNA repair gene mutational status, a functional defect in HR in the organoids correlated with PARP inhibitor sensitivity. A functional defect in replication fork protection correlated with carboplatin and CHK1 and ATR inhibitor sensitivity. Our results indicate that a combination of genomic analysis and functional testing of organoids allows for the identification of targetable DNA damage repair defects. Larger numbers of patient-derived organoids must be analyzed to determine whether these assays can reproducibly predict patient response in the clinic.Significance: Patient-derived ovarian tumor organoids grow rapidly and match the tumors from which they are derived, both genetically and functionally. These organoids can be used for DNA repair profiling and therapeutic sensitivity testing and provide a rapid means of assessing targetable defects in the parent tumor, offering more suitable treatment options. Cancer Discov; 8(11); 1404-21. ©2018 AACR. This article is highlighted in the In This Issue feature, p. 1333.

Evidence for lineage continuity between early serous proliferations (ESPs) in the Fallopian tube and disseminated high-grade serous carcinomas

The distal Fallopian tube is a site of origin for many 'ovarian' high-grade serous carcinomas (HGSCs) with intraepithelial carcinomas (STICs) that share identical TP53 mutations with metastatic tumors. TP53 mutation-positive early serous proliferations (ESPs) comprise a spectrum including p53 signatures and serous tubal intraepithelial lesions (STILs) and are not considered malignant; however, ESPs are often the only abnormality found in Fallopian tubes of women with metastatic HGSC. The purpose of this study was to determine if a relationship exists between isolated ESPs and concurrent metastatic HGSCs in the absence of STIC. Fallopian tubes from 32 HGSCs without a co-existing STIC/HGSC in the endosalpinx were exhaustively sectioned. The presence of either STIC/HGSC or ESP in the endosalpinx was documented and DNA from tissues containing ESPs, concurrent HGSC, and control epithelia were interrogated for TP53 mutations by targeted amplicon-based sequencing with average coverage reads >4000 across DNA replicate samples. Serial sectioning revealed a previously unrecognized STIC/HGSC in 3 of 32 (9.3%) and ESPs in 13 (40.6%). Twelve contained TP53 mutations. Nine (75%) shared identical TP53 mutations with concurrent HGSCs, four at high (≥ 5%) and five at low (< 5%) allele frequency. All control epithelia were TP53 mutation-negative. This study, for the first time, indicates lineage identity between ESPs in the distal tube and some metastatic HGSCs via a shared site-specific TP53 mutation. It supports a novel serous carcinogenic sequence in which an ESP could eventually culminate in a metastatic serous cancer via 'precursor escape' and would explain the apparent sudden onset of cancers without co-existing STICs. This paradigm for serous cancer development underscores the likelihood that multiple precursor types in the Fallopian tube contribute to serous cancer development with implications for the evolution, pathologic classification, and prevention of this lethal malignancy. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

SMARCA4-deficient undifferentiated uterine sarcoma (malignant rhabdoid tumor of the uterus): a clinicopathologic entity distinct from undifferentiated carcinoma

Small cell carcinoma of the ovary, hypercalcemic type is a rare, aggressive malignancy which usually occurs in young women and is characterized by mutations in SMARCA4, with few other alterations. We recently encountered uterine tumors with morphologic, immunohistochemical, and genetic similarities to small cell carcinoma of the ovary, hypercalcemic type. Herein we report the clinicopathologic and molecular features (using a targeted massively parallel sequencing [MPS] assay) of these tumors. The cases were diagnosed on cervical and endometrial biopsies (n = 2, 34, and 29 years) or hysterectomy and bilateral salpingo-oophorectomy (n = 3, 25, 33, and 58 years). The tumors were composed of sheets of large atypical epithelioid cells with prominent rhabdoid morphology, indistinguishable from the "large cell" variant of small cell carcinoma of the ovary, hypercalcemic type. In three cases, the ovaries were pathologically examined to exclude a primary ovarian malignancy. Immunohistochemically, four of four cases showed SMARCA4 loss, and were negative or only focally positive for keratins, EMA, and claudin-4. One of three cases was positive for WT-1. Targeted MPS was successfully performed on 4 of 5 tumors, and showed recurrent mutations in SMARCA4, with few other alterations. Of the cases diagnosed on hysterectomy, all had extensive lymphovascular invasion, extra-uterine spread, and marked infiltrative growth. These tumors were uniformly aggressive; all patients died of disease (median survival 7 months, range 1-43 months). We propose this entity be called "SMARCA4-deficient undifferentiated uterine sarcoma (malignant rhabdoid tumor of the uterus)", a term which describes both the tumor's underlying molecular abnormality and its morphology. Its unique clinicopathologic and molecular features differentiate it from other related malignancies, including undifferentiated endometrial carcinoma, small cell carcinoma of the ovary (hypercalcemic type), and epithelioid sarcoma. We review and discuss previously reported "rhabdoid tumors of the uterus;" while they are a heterogenous group of tumors, some of them are likely examples of this entity. Correctly identifying cases of SMARCA4-deficient uterine sarcoma from histologic mimics is important as it may have prognostic, predictive, and germline implications.

Surgical prevention strategies in ovarian cancer

Given the current lack of effective screening for ovarian cancer, surgical removal of at-risk tissue is the most successful strategy to decrease risk of cancer development. However, the optimal timing of surgery and tissues to remove, as well as the appropriate patients to undergo preventive procedures are poorly understood. In this review, we first discuss the origin and precursors of ovarian epithelial carcinomas, focusing on high-grade serous carcinomas and endometriosis-associated carcinomas, which cause the majority of the mortality and incidence of ovarian cancer. In addition, we summarize the implications of current understanding of specific pathogenic origins for surgical prevention and remaining gaps in knowledge. Secondly, we review evidence from the epidemiologic literature on the associations of various surgical prevention strategies, including endometriosis excision, tubal procedures, and bilateral salpingo-oophorectomy, with risk of future ovarian cancer development, as well as the short- and long-term consequences of these strategies on women's health and quality and life. We conclude with recommendations for surgical prevention in women with high-risk genetic mutations and average-risk women, and a brief discussion of ongoing research that will help clarify optimal surgical approaches that balance risk-reduction with maintenance of women's quality of life.

Origin of clear cell carcinoma: nature or nurture?

A rare but serious complication of endometriosis is the development of carcinoma, and clear cell and endometrioid carcinomas of the ovary are the two most common malignancies which arise from endometriosis. They are distinct diseases, characterized by unique morphologies, immunohistochemical profiles, and responses to treatment. However, both arise in endometriosis and can share common mutations. The overlapping mutational profiles of clear cell and endometrioid carcinomas suggest that their varied histologies may be due to a different cell of origin which gives rise to each type of cancer. Cochrane and colleagues address this question in a recent article in this journal. They show that a marker of ovarian clear cell carcinoma, cystathionine gamma lyase, is expressed in ciliated cells. Similarly, they show that markers of secretory cells (estrogen receptor and methylenetetrahydrofolate dehydrogenase 1) are expressed in ovarian endometrioid carcinoma. Taken together, they suggest that endometrioid and clear cell carcinomas arise from cells related to secretory and ciliated cells, respectively. We discuss Cochrane et al's work in the context of other efforts to determine the cell of origin of gynecological malignancies, with an emphasis on recent developments and challenges unique to the area. These limitations complicate our interpretation of tumor differentiation; does it reflect nature imposed by a specific cell of origin or nurture, by either mutation(s) or environment? Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Diagnostic potential for a serum miRNA neural network for detection of ovarian cancer

Recent studies posit a role for non-coding RNAs in epithelial ovarian cancer (EOC). Combining small RNA sequencing from 179 human serum samples with a neural network analysis produced a miRNA algorithm for diagnosis of EOC (AUC 0.90; 95% CI: 0.81–0.99). The model significantly outperformed CA125 and functioned well regardless of patient age, histology, or stage. Among 454 patients with various diagnoses, the miRNA neural network had 100% specificity for ovarian cancer. After using 325 samples to adapt the neural network to qPCR measurements, the model was validated using 51 independent clinical samples, with a positive predictive value of 91.3% (95% CI: 73.3–97.6%) and negative predictive value of 78.6% (95% CI: 64.2–88.2%). Finally, biologic relevance was tested using in situ hybridization on 30 pre-metastatic lesions, showing intratumoral concentration of relevant miRNAs. These data suggest circulating miRNAs have potential to develop a non-invasive diagnostic test for ovarian cancer.

Ovarian cancer is a major cause of cancer death among women. A woman’s survival often hinges on doctors detecting the tumor before it has spread beyond the ovary. Unfortunately, most women with ovarian cancer are not diagnosed until they have symptoms – such as pelvic pain, bloating, swelling of the abdomen or appetite loss. By then, the disease has usually spread and is difficult to treat. There is currently no reliable test to diagnose ovarian cancer before symptoms emerge. Some tests measure proteins in the blood or use ultrasound images to identify ovary tumors. These tests usually still identify the disease too late. Sometimes they produce “false positive” results, which may cause women without cancer to undergo unnecessary surgery.

Many ovarian cancers have defects in small pieces of genetic information called microRNAs. These microRNAs impact the tumor in multiple ways, and cells release microRNAs into the blood. Testing a seemingly healthy women’s blood for the same pattern of altered microRNAs found in women with ovarian cancer might be one way to detect the disease earlier.

Now, Elias et al. have identified a pattern of seven microRNAs in the blood that appears to predict ovarian cancer. In the experiments, a computer program searched for microRNA patterns in women with ovarian cancer. The program sifted through the microRNAs in blood from women with and without ovarian cancer. Over time, the computer program “learned” to identify a pattern of microRNAs found only in women with ovarian cancer. It then created a formula for identifying ovarian cancer based on seven of the microRNAs.

Elias et al. then verified that the formula accurately detected ovarian cancer by testing it on blood samples from more women with and without cancer. They also found the seven microRNAs in tiny ovarian cancer tumors collected from women. This suggests the formula might be able to detect even the smallest tumors. More studies are needed to determine when this cancer-linked pattern first emerges and confirm that this ovarian cancer-detection formula works. If the test is validated, it might be used to screen women who are at high risk for ovarian cancer because of mutations in the BRCA1 and BRCA2 genes.

Abstract MIP-052: THE ROLES OF CD24 IN OVARIAN CANCER DEVELOPMENT

OBJECTIVES: CD24 is recently reported as ovarian cancer stem cell markers, and the expression of CD24 is increased from borderline tumors to invasive ovarian carcinomas. However, the underlying pathways controlled by CD24 in ovarian pathogenesis were poorly understood. We investigated the potential roles of CD24 in normal fallopian tube epithelial (FTE) cells and ovarian cancer development.

METHODS: Lentiviral particles harboring CD24 shRNAs targeting CD24 expression were used to establish FTE cell lines and ovarian cancer cell lines with CD24 knockdown. The resulting cell lines were compared with the correspondent cells with non target shRNA control in colony formation assay, BrdU incorporation, cell growth and drug resistance. Western blot was used for analyzing downstream pathways affected by the knockdown of CD24. Expression of CD24 and its downstream effectors identified from western blot, including Pax 2 and Gli1 were studied in normal FTE, non–serous and serous tumor tissues by immunohistochemistry (IHC) to confirm whether the in vitro study is clinically relevant.

RESULTS: Western blot analysis showed that CD24 expression was absent in normal ovarian surface epithelial (OSE) cells but was relatively high in normal FTE cells. In addition, serous cancer cell lines have a lower CD24 expression when compared to non–serous cancer cell lines. Knockdown of CD24 in FTE cells caused slower growth, lower ability in colony formation, reduced percentage of cells in S phase and decrease in expression of p–stat3 in JAK pathway and the JAK downstream targets Nanog and OCT3/4; and Pax2, which is normally expressed in FTE but lost in FTE secretory cell outgrowth (SCOUT). The loss of Pax2 in SCOUT is associated with serous carcinoma. IHC showed cytoplasmic co–localized expression of CD24 and Pax2 in the normal FTE tissue, suggesting the possibility of interaction between these two proteins in vivo. In contrast, knockdown of CD24 in ovarian cancer cells caused faster growth, higher ability in colony formation, increased percentage of cells in S phase, more resistant to carboplatin and higher expression of Shh and Gli1 in Sonic hedgehog (SHH) pathway. The above effects were more obvious in the non–serous cancer cell line. Activation of SHH pathway requires translocation of Gli1 into the nucleus. Concurrent with the in vitro results, IHC showed that the expression of Gli1 was found inside the nucleus in the non–serous tumor tissues but in the cytoplasm in serous–tissue, suggesting that the effect brought by SHH pathway is more prominent in the non–serous cancer cells.

CONCLUSION: Our study is the first study revealing the linkage between CD24 and PAX2, and suggesting normal FTE cells depends on CD24/JAK pathway for growth and the loss of CD24 expression and hence, the loss of PAX2 may be associated with serous type tumor development, basing on other studies that SCOUTs were significantly associated with serous carcinoma. Moreover, the study also suggests CD24 pathway affects Type I and Type II (HGSOC) tumors differently. The CD24/SHH pathways may be responsible in controlling cell growth and drug resistance in ovarian cancer cells, hence, warrant further studies.

Citation Format: Pui–Wah Choi, Brooke E. Howitt, Christopher P. Crum, Ross S. Berkowitz, and Shu–Wing Ng. THE ROLES OF CD24 IN OVARIAN CANCER DEVELOPMENT [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr MIP-052.

Comprehensive Human Papillomavirus Genotyping in Cervical Squamous Cell Carcinomas and Its Relevance to Cervical Cancer Prevention in Malawian Women

PURPOSE

Cervical squamous cell carcinoma (SCC) continues to be a significant cause of cancer morbidity and is the third leading cause of cancer-related death in women worldwide. In sub-Saharan Africa, cervical cancer is not only the most common female cancer but also the leading cause of cancer-related deaths in women. Malawi, in particular, has the highest burden of cervical cancer. With the increasing use of human papillomavirus (HPV) vaccination, documenting the prevalent HPV types in those high-risk populations is necessary to both manage expectations of HPV vaccination and guide future vaccine development.

MATERIALS AND METHODS

In this study, we performed HPV typing on 474 cervical SCC samples and analyzed the potential impact of HPV vaccination in this population.

RESULTS

Ninety-seven percent of tumors were positive for at least one HPV type, and 54% harbored more than one HPV type. HPV 16 was the most common type (82%), followed by HPV 18 (34%), HPV 35 (24%), and HPV 31 (12%). A vaccine against HPV 16 and 18 would ideally prevent 53% of cervical SCC, and the nonavalent HPV vaccine (covering HPV 16, 18, 31, 33, 45, 52, and 58) would prevent 71% of cervical SCC in Malawi (assuming 100% vaccine efficacy). The main reason for a lack of coverage was high prevalence of HPV 35, which was also present as a single infection in a small subset of patients.

CONCLUSION

Although any HPV vaccination in this population would likely prevent a significant proportion of cervical cancer, the nonavalent vaccine would provide better coverage. Furthermore, investigation of the role of HPV 35 in this population, including possible cross-protection with other HPV types, should be pursued.

Serous tubal intraepithelial neoplasia: the concept and its application

In recent years it has become clear that many extra-uterine (pelvic) high-grade serous carcinomas (serous carcinomas) are preceded by a precursor lesion in the distal fallopian tube. Precursors range from small self-limited 'p53 signatures' to expansile serous tubal intraepithelial neoplasms that include both serous tubal epithelial proliferations (or lesions) of uncertain significance and serous tubal intraepithelial carcinomas. These precursors can be considered from three perspectives. The first is biologic underpinnings, which are multifactorial, and include the intersection of DNA damage with Tp53 mutations and disturbances in transcriptional regulation that increase with age. The second perspective is the morphologic discovery and classification of intraepithelial neoplasms that are intercepted early in their natural history, either incidentally or in risk-reduction surgeries for germline mutations. For the practicing pathologist, as well as the investigators, a distinction between a primary intraepithelial neoplasm and an intramucosal carcinoma must be made to avoid misinterpreting (or underestimating) the significance of these proliferations. The third perspective is the application of this information to intervention, devising strategies that will actually lower the ovarian cancer death rate by opportunistic salpingectomy, widespread comprehensive genetic screening and early detection. Central to this issue are the questions of (1) whether some STICs are metastatic, (2) whether lower-grade epithelial proliferations can invade prior to evolving into intraepithelial carcinoma, or (3) metastasize and become malignant elsewhere ('precursor escape'). An important caveat is the persistent and unsettling reality that many high-grade serous carcinomas are not associated with an obvious point of initiation in the fallopian tube. The pathologist sits squarely in the midst of all of these issues, and has a pivotal role in managing expectations for stemming the death rate from this lethal disease.

Deciphering the Multifactorial Susceptibility of Mucosal Junction Cells to HPV Infection and Related Carcinogenesis

Human papillomavirus (HPV)-induced neoplasms have long been considered to originate from viral infection of the basal cell layer of the squamous mucosa. However, this paradigm has been recently undermined by accumulating data supporting the critical role of a discrete population of squamo-columnar (SC) junction cells in the pathogenesis of cervical (pre)cancers. The present review summarizes the current knowledge on junctional cells, discusses their high vulnerability to HPV infection, and stresses the potential clinical/translational value of the novel dualistic model of HPV-related carcinogenesis.

Genetic Basis for PD-L1 Expression in Squamous Cell Carcinomas of the Cervix and Vulva

IMPORTANCE

Patients with squamous cell carcinoma (SCC) of the cervix or vulva have limited therapeutic options, and the potential for immunotherapy for this population has not been evaluated. Recent trials suggest that tumors with a genetic basis for PD-1 (programmed cell death protein 1) ligand expression are highly sensitive to therapeutic antibodies targeting PD-1.

OBJECTIVE

To determine the genetic status of CD274 (encoding PD-L1 [programmed cell death 1 ligand 1]) and PDCD1LG2 (encoding PD-L2 [programmed cell death 1 ligand 2]) in SCCs of the cervix and vulva and to correlate the findings with PD-L1 protein expression.

DESIGN, SETTING, AND PARTICIPANTS

We performed fluorescence in situ hybridization (FISH) using probes targeting CD274, PDCD1LG2, and the centromeric portion of chromosome 9, and immunohistochemistry (IHC) using an antibody recognizing PD-L1 on formalin-fixed, paraffin-embedded (FFPE) biopsy specimens from 48 cervical SCCs and 23 vulvar SCCs.

MAIN OUTCOMES AND MEASURES

Tumors were categorized according to the genetic abnormality in CD274 and PDCD1LG2 (coamplification > cogain > polysomy > disomy) as detected by FISH, and evaluated on a semiquantitative scale (modified H score, the product of the percentage of tumor cells with positive staining and the maximum intensity of positive staining) for PD-L1 protein expression as detected by IHC.

RESULTS

Overall, 71 samples of FFPE tissue from cases of cervical SCCs (n = 48) and vulvar SCCs (n = 23) were retrieved from the archives of Brigham and Women's Hospital and included in this study. We observed cogain or coamplification of CD274 and PDCD1LG2 in 32 of 48 cervical SCCs (67%) and 10 of 23 vulvar SCCs (43%). Median PD-L1 protein expression was highest among tumors with CD274 and PDCD1LG2 coamplification and lowest among tumors with disomy.

CONCLUSIONS AND RELEVANCE

Recurrent copy number gain of the genes encoding the PD-1 ligands provides a genetic basis for PD-L1 expression in a subset of cervical and vulvar SCCs and identifies a class of patients that are rational candidates for therapies targeting PD-1.

Rationale for Developing a Specimen Bank to Study the Pathogenesis of High-Grade Serous Carcinoma: A Review of the Evidence

Women with clinically detected high-grade serous carcinomas (HGSC) generally present with advanced-stage disease, which portends a poor prognosis, despite extensive surgery and intensive chemotherapy. Historically, HGSCs were presumed to arise from the ovarian surface epithelium (OSE), but the inability to identify early-stage HGSCs and their putative precursors in the ovary dimmed prospects for advancing our knowledge of the pathogenesis of these tumors and translating these findings into effective prevention strategies. Over the last decade, increased BRCA1/2 mutation testing coupled with performance of risk-reducing surgeries has enabled studies that have provided strong evidence that many, but probably not all, HGSCs among BRCA1/2 mutation carriers appear to arise from the fallopian tubes, rather than from the ovaries. This shift in our understanding of the pathogenesis of HGSCs provides an important opportunity to achieve practice changing advances; however, the scarcity of clinically annotated tissues containing early lesions, particularly among women at average risk, poses challenges to progress. Accordingly, we review studies that have kindled our evolving understanding of the pathogenesis of HGSC and present the rationale for developing an epidemiologically annotated national specimen resource to support this research. Cancer Prev Res; 9(9); 713-20. ©2016 AACR.

Morphologic correlates of molecular alterations in extrauterine Müllerian carcinomas

Extrauterine high-grade serous carcinomas can exhibit various histologic patterns including (1) classic architecture that is papillary, micropapillary and infiltrative and (2) solid, endometrioid, and transitional (ie, SET) patterns. Although the SET pattern has been associated with germline BRCA mutations, potential molecular underpinnings have not been fully investigated. DNA was isolated from 174 carcinomas of the fallopian tube, ovary, or peritoneum. Targeted next-generation sequencing was performed and single-nucleotide and copy number variants were correlated with morphologic subtype. Overall, 79% of tumors were classified as high-grade serous carcinoma (n=138), and the most common mutations in high-grade serous carcinomas were TP53 (94%), BRCA1 (25%), BRCA2 (11%), and ATM (7%). Among chemotherapy-naive high-grade serous carcinomas, 40 cases exhibited classic morphology and 40 cases had non-classic morphology (SET or ambiguous features). Mutations in homologous recombination pathways were seen across all tumor histotypes. High-grade serous carcinomas with homologous recombination mutations were six times more likely to be associated with non-classic histology (P=0.002) and were significantly more likely to be platinum sensitive and have improved progression-free survival (PFS) (P=0.007 and P=0.004, respectively). In a multivariate analysis adjusted for age, homologous recombination mutation status and increased copy number variants were independently associated with improved PFS (P=0.008 and P=0.005, respectively). These findings underscore the potential significance of variant morphologic patterns and comprehensive genomic analysis in high-grade serous carcinomas with potential implications for pathogenesis, as well as response to targeted therapies.

In vitro and in vivo correlates of physiological and neoplastic human Fallopian tube stem cells

High-grade serous cancer (HGSC) progresses to advanced stages without symptoms and the 5-year survival rate is a dismal 30%. Recent studies of ovaries and Fallopian tubes in patients with BRCA1 or BRCA2 mutations have documented a pre-metastatic intramucosal neoplasm that is found almost exclusively in the Fallopian tube, termed 'serous tubal intraepithelial carcinoma' or STIC. Moreover, other proliferations, termed p53 signatures, secretory cell outgrowths (SCOUTs), and lower-grade serous tubal intraepithelial neoplasms (STINs) fall short of STIC but share similar alterations in expression, in keeping with an underpinning of genomic disturbances involved in, or occurring in parallel with, serous carcinogenesis. To gain insight into the cellular origins of this unique tubal pathway to high-grade serous cancer, we cloned and both immortalized and transformed Fallopian tube stem cells (FTSCs). We demonstrated that pedigrees of FTSCs were capable of multipotent differentiation and that the tumours derived from transformed FTSCs shared the histological and molecular features of HGSC. We also demonstrated that altered expression of some biomarkers seen in transformed FTSCs and HGSCs (stathmin, EZH2, CXCR4, CXCL12, and FOXM1) could be seen as well in immortalized cells and their in vivo counterparts SCOUTs and STINs. Thus, a whole-genome transcriptome analysis comparing FTSCs, immortalized FTSCs, and transformed FTSCs showed a clear molecular progression sequence that is recapitulated by the spectrum of accumulated perturbations characterizing the range of proliferations seen in vivo. Biomarkers unique to STIC relative to normal tubal epithelium provide a basis for novel detection approaches to early HGSC, but must be viewed critically given their potential expression in lesser proliferations. Perturbations shared by both immortalized and transformed FTSCs may provide unique early targets for prevention strategies. Central to these efforts has been the ability to clone and perpetuate multipotent FTSCs.

Abstract POSTER-CTRL-1208: A dualistic model for the origin of high-grade serous carcinoma: BRCA mutation status, histology and tubal intraepithelial carcinoma

Extra-uterine high-grade serous carcinoma (HGSC) is linked to the fimbria via serous tubal intraepithelial carcinoma or STIC. Women with deleterious BRCA1/2 germ-line mutations (BRCA+) are at high risk for HGSC and ~5% of risk reducing salpingo-oophorectomies harbor a STIC. However, STIC is found in only~40% of the HGSC population and less frequently in endometrioid variants of HGSC (Roh 2009). Consecutively tested women with untreated HGSC, with detailed fallopian tube examination (SEE-FIM protocol), who had germ-line BRCA testing were studied. STIC status was determined by histologic exam, and tumors were classified as predominately SET (&gt; 50% solid, endometrioid-like, or transitional, Soslow 2012) or classic histology. SET features trended towards a higher frequency in BRCA+ vs BRCA- women (50 vs 28%, p = .11). BRCA- subjects with SET morphology were significantly younger than those with classic HGSC (mean 56.2 vs 64.8 years; p=0.04), with a generally better clinical outcome. STIC was significantly more frequent in BRCA- tumors (66 vs 31%, p = 0.017) and more frequent in classic HGSCs in BRCA- (83 vs 22%, p = 0.003) women. Overall, several co-variables – histology, BRCA status, age, coexisting STIC, response to therapy - suggest two categories of HGSC with differences in speed of development, progression, outcome, histology, and possibly, precursor type. We introduce a dualistic HGSC model with a faster evolving tumor type that is not linked to a long-standing STIC. Resolving the nature of this second pathway is germane to both resolving the precursors and expectations from both screening and prevention of HGSC.

Citation Format: Brooke E Howitt MD, Suchanan Hanamornroongruang MD, Douglas Lin MD PhD, James E Conner MD PhD, Stephanie Schulte MD, Judy Garber MD, Christopher P Crum MD, Emily E Meserve MD MPH. A dualistic model for the origin of high-grade serous carcinoma: BRCA mutation status, histology and tubal intraepithelial carcinoma [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr POSTER-CTRL-1208.

Abstract POSTER-CTRL-1204: Novel strategies for targeting high-grade serous ovarian cancer

High-grade serous ovarian carcinoma (HGSC) presents significant clinical and therapeutic challenges. Emerging data from The Cancer Genome Atlas (TCGA) have identified a number of new genetic aberrations but their functional significance and the role they play in early tumorigenesis remains to be determined. In addition, identifying the key genetic lesions responsible for tumor initiation and the specific cell of origin is a priority for ovarian cancer research. Although the traditional model of carcinogenesis has focused on the ovary as a tumor initiation site, recent preclinical and clinical studies have suggested that there are additional sites of origin outside the ovary, namely fallopian tubal secretory epithelial cells (FTSECs). This new model of tumorigenesis has further identified novel entities in the fallopian tube epithelium that represent precursors to invasive carcinoma – the TP53 signature and serous tubal intraepithelial carcinoma (STIC).

Identifying and characterizing the events leading to the development of TP53 signatures and STICs, the critical steps in their transition to malignancy, and novel methods for detecting this transition prior to cancer development are critical for cancer prevention and development of personalized approaches to therapy. We have successfully developed genetic models of de novo HGSC that originate in FTSECs and mimic the key genetic alterations and precursor lesions characteristic of human invasive ovarian cancer. The murine tumors accurately recapitulate the histologic, immunophenotypic (CK-8, STMN1, PAX2, P53, Ki-67, WT1, and CA-125), and genomic alterations observed in human HGSC, thus providing a compelling argument for serous carcinogenesis originating in the FTSEC. Our models serve as a proof-of-concept that high-grade serous “ovarian” cancer can arise from the FTSEC and progress to metastatic disease via pre-invasive lesions, namely the STICs. We are currently using the Pax8-driven system to interrogate the role of TCGA genes that have been identified as being important for serous tumorigenesis. Successful completion of our studies will demonstrate that the fallopian tubal secretory epithelial cell is indeed a cell-of-origin for ovarian and pelvic serous carcinomas in vivo when using the most common key TCGA-based tumor drivers for BRCA and non-BRCA tumors, respectively.

The first goal of our research is be to produce valid models for HGSC tumors. The second is to identify unique characteristics of early serous carcinogenesis in the tube that can be exploited for early detection. The third is to determine the causes of the earliest events preceding malignancy, which will enable more efficient methods of diagnostic imaging and cancer prevention with a focus on the distal fallopian tube. Furthermore, by using a combination of murine model studies and epidemiological data from patients, it will be important to determine if premenopausal women with BRCA mutations can be offered risk-reduction surgery in a multi-step procedure without undergoing surgical menopause and loss of fertility in their younger years.

Citation Format: Ruth Perets, Gregory A Wyant, Anders W Ohman, Sunita R Setlur, Christopher P. Crum, Ronny Drapkin, Daniela M. Dinulescu. Novel strategies for targeting high-grade serous ovarian cancer [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr POSTER-CTRL-1204.

Characterization of twenty-five ovarian tumour cell lines that phenocopy primary tumours

Currently available human tumour cell line panels consist of a small number of lines in each lineage that generally fail to retain the phenotype of the original patient tumour. Here we develop a cell culture medium that enables us to routinely establish cell lines from diverse subtypes of human ovarian cancers with >95% efficiency. Importantly, the 25 new ovarian tumour cell lines described here retain the genomic landscape, histopathology and molecular features of the original tumours. Furthermore, the molecular profile and drug response of these cell lines correlate with distinct groups of primary tumours with different outcomes. Thus, tumour cell lines derived using this methodology represent a significantly improved platform to study human tumour pathophysiology and response to therapy.