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.

Vestibular Mast Cell Density in Vulvodynia: A Case-Controlled Study

OBJECTIVES

To identify whether mast cell densities in vulvar biopsies from the vestibule are associated with vulvodynia.

METHODS

We enrolled 100 women aged 19 to 59 years with confirmed vulvodynia cases, 100 racially matched controls, and 100 black control women. All had vulvar biopsies performed at the 7 o'clock position of the vestibule, which were then immunostained to detect c-KIT protein. The numbers of c-KIT positive mast cells per ×400 magnification field were manually counted, and t tests and logistic regression were used to assess the association with case-control status.

RESULTS

Of the biopsies, 235 were adequate samples for c-KIT testing for mast cells. The mast cell density was substantially lower in black control women (13.9 ± 10.9) in comparison to white control women (22.5 ± 13.2 p < 0.001): hence the analysis was confined to white cases and racially matched control women. Compared with racially matched controls, cases were younger, more likely to be married, and reported a higher household income. The average number of mast cells per ×400 magnification field overall was 19.1 ± 13.2 (range, 0-62). There was no difference in the mast cell count between racially matched cases (22.4 ± 13.9 per ×400 field) and controls (22.5 ± 13.2) in either the univariate or multivariable analyses. Within the group of cases, there was no difference in mast cell density based on the presence or absence of a variety of urogenital symptoms.

CONCLUSIONS

No difference in mast cell density in biopsies of the vestibule was found between white cases and racially matched controls. Black control women have a lower mast cell density compared with white control women.

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.