Development Of High-grade Serous Ovarian Cancer Research Articles

High-grade serous ovarian cancer development and anti-PD-1 resistance is driven by IRE1α activity in neutrophils.

High-grade serous ovarian cancer (HGSOC) is an aggressive malignancy that remains refractory to current immunotherapies. While advanced stage disease has been extensively studied, the cellular and molecular mechanisms that promote early immune escape in HGSOC remain largely unexplored. Here we report that primary HGSO tumors program neutrophils to inhibit T cell anti-tumor function by activating the endoplasmic reticulum (ER) stress sensor IRE1α. We found that intratumoral neutrophils exhibited overactivation of ER stress response markers compared with their counterparts at non-tumor sites. Selective deletion of IRE1α in neutrophils delayed primary ovarian tumor growth and extended the survival of mice with HGSOC by enabling early T cell-mediated tumor control. Notably, loss of IRE1α in neutrophils sensitized tumor-bearing mice to PD-1 blockade, inducing HGSOC regression and long-term survival in ∼50% of treated hosts. Hence, neutrophil-intrinsic IRE1α facilitates early adaptive immune escape in HGSOC and targeting this ER stress sensor might be used to unleash endogenous and immunotherapy-elicited immunity that controls metastatic disease.

BBOX1 mediates metabolic reprogramming driven by hypoxia and participates in the malignant progress of high-grade serous ovarian cancer

High-grade serous ovarian cancer (HGSOC) is the most aggressive type of ovarian cancer that causes great threats to women's health. Therefore, we performed RNA-sequencing technology in clinical samples to explore the molecular mechanisms underlying the progression of HGSOC. We then noticed BBOX1, a kind of 2-oxoglutarate-dependent enzyme that is highly expressed in HGSOC tumor tissues. Functional studies showed that BBOX1 promotes cell survival and growth of HGSOC cells in vitro and in vivo. Overexpression of the wild-type BBOX1 promoted cell proliferation, but the Asn191 and Asn292 mutation (key amino acid for the enzymatic activity of BBOX1) counteracted this effect (P < 0.05), which indicated that the promotion effect of BBOX1 on HGSOC cell proliferation was related to its catalytic activity. Downregulation of BBOX1 reduced the activity of the mTORC1 pathway, and decreased protein expression of IP3R3 and phosphorylation level of S6KThr389. Metabolomics analysis revealed that BBOX1 is implicated in the glucose metabolism, amino acid metabolism, and nucleotide metabolism of HGSOC cells. In addition, inhibition of BBOX1 suppressed HGSOC cell glycolysis and decreased glucose consumption, lactate production, and the expression of key factors in glycolysis. Finally, we found hypoxia induced the expression of BBOX1 in HGSOC cells and confirmed that BBOX1 could be transcriptionally activated by hypoxia-inducible factor-1α, which could directly bind to the BBOX1 promoter. In summary, BBOX1 mediated the metabolic reprogramming driven by hypoxia, and affected cell metabolism through the mTORC1 pathway, thus acting as an oncogene during HGSOC development.

Abstract LB311: Multimodal spatial profiling reveals the emergence of an immune suppressive microenvironment at the initial stages of high-grade serous ovarian cancer development

Abstract Introduction: Despite the clear genetic evidence linking serous tubal intraepithelial carcinoma (STIC) and high-grade serous ovarian carcinoma (HGSOC), the specific conditions and events that promote the progression of STIC lesions into invasive disease remain poorly understood. Method: As a critical initial step, we have assembled a cohort of incidental p53 signatures, STIC lesions, and STIC with concurrent HGSOC. We have performed extensive multi-modal analysis using multiplexed tissue imaging and spatial transcriptomics that identify features of the immune system that play a vital role in the early steps of HGSOC development. We have processed 43 specimens using highly multiplexed tissue imaging at single-cell resolution (cyclic immunofluorescence, CyCIF), and 35 specimens for micro-regional spatial transcriptomics using the GeoMx (Whole Transcriptome, Nanostring) on over 450 pathologist-annotated regions of interest. Results: Our data suggests an immune-cold environment and T-cell dysfunction in STIC lesions, including incidental STIC. One of the significant immune populations identified was CD103+ tissue-resident memory T cells (TRM). In incidental p53 signatures, activation of TRM was rare, similar to FT, which may indicate the absence of sensing “tumor antigen” by these TRM. CyCIF analysis also revealed that most incidental STIC lesions (7/9 cases) overexpress major histocompatibility complex (MHC) class I compared to the normal epithelium, especially both HLA complex, HLA-A and HLA-E. Most STICs showed extensive intra-lesion heterogeneity, with some STICs remaining HLA-A and HLA-E negative. Incidental p53 signatures, on the other hand, were mostly HLA-A and HLA-E negative and, when positive, had only a few cells expressing HLA. We hypothesized that there might be a natural selection of HLA-E-positive clones as STICs progress to HGSOC. Consistent with this, HGSOC showed further overexpression of HLA-E. However, HLA-E heterogeneity was still observed in the invasive tumor, with both positive and negative clones co-existing. Geomx data suggested that the interferon signaling pathway is upregulated in the epithelial of HLA-E positive STIC and cancer clones compared to HLA-E negative clones. In turn, both HLA-A and HLA-E might be overexpressed in the epithelial of HLA-E-positive STICs. Overall, we showed that the response in interferon (IFN) α and γ, NF-KB, and IL-6-induced STAT-3 pathways were upregulated in both STIC lesions and carcinoma. The role of these pathways, especially STAT-3 pathway, has been shown in other aneuploid cancers in promoting immune escape, cell proliferation and migration, chemoresistance and inhibiting apoptosis. We have shown the co-localization of cGAS and BAF, a marker for micronuclei rupture, by super-resolution 3D imaging to confirm one of the mechanisms of IFN activation. Conclusion: Taken together, these data may indicate chromosomal instability is one of the mechanisms that is driving the IFN-signaling pathway and, hence, a potential selective advantage for HLA-E-positive clones in tumorigenesis, leading to inhibiting NK cell surveillance followed by reducing T cell infiltration. Citation Format: Tanjina Kader, Jia-Ren Lin, Shannon Coy, Clemens Hug, Yu-An Chen, Roxanne J. Pelletier, Mariana Leon, John Lee, Yi-Lin Xu, Clarence Yapp, Natalie Shih, Gabriel Mingo, Euihye Jung, Srishti Rathore, Judith Agudo, Charles Drescher, Peter K. Sorger, Ronny Drapkin, Sandro Santagata. Multimodal spatial profiling reveals the emergence of an immune suppressive microenvironment at the initial stages of high-grade serous ovarian cancer development [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB311.

MiR-451a suppresses the proliferation and migration of high-grade serous ovarian cancer by targeting RAB5A through the Ras/Raf/MEK/ERK pathway.

Ovarian cancer is one of the most common cancers in women. Profiles changes of microRNAs (miRNAs) are closely linked to malignant tumors. In the present study, we investigated expression of miR-451a in high-grade serous ovarian cancer (HGSOC). We also investigated the potential pathological roles and the likely mechanism of miR-451a in the development of HGSOC using animal models and cell lines. Using bioinformatics techniques and a real-time PCR, we analyzed differently expressed miRNAs in HGSOC compared to normal tissue. MTT (i.e. 3-[4, 5-dimethyl thiazol-2-yl]-2,5-diphenyl tetrazolium bromide), EDU (i.e. 5-ethynyl-2'-deoxyuridine) and transwell assays were performed to investigate the effect of miR-451a on the proliferation and migration of HGSOC SKOV-3 cells. A dual luciferase reporter assay was performed to verify the targeting relationship of miR-451 and RAB5A (one of the Rab GTPase proteins that regulates endocytosis and vesicle transport). Also, we analyzed levels of the RAB5A mRNA and protein by real-time PCR, western blotting and immunohistochemistry assays in HGSOC cells and tissues. Finally, we performed in vivo experiments using HGSOC mice. miR-451a was substantially upregulated in HGSOC and associated with favorable clinical characteristics. miR-451a knockdown significantly increased growth and metastasis of HGSOC cell line SKOV-3 through Ras/Raf/mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling. In addition, RAB5A, an early endosome marker, was shown to be a direct target of miR-451a. Moreover, RAB5A is correlated with unfavorable clinical features and shows independent prognostic significance in HGSOC. We found that the miR-451a/RAB5A axis is associated with tumorigenesis and progression through the Ras/Raf/MEK/ERK pathway, providing prognostic indicators and therapeutic targets for patients with HGSOC.

Potential Contribution of Ovarian Granulosa Cells to High-Grade Serous Ovarian Cancer Development

Potential Contribution of Ovarian Granulosa Cells to High-Grade Serous Ovarian Cancer Development

RUNX1 knockdown induced apoptosis and impaired EMT in high-grade serous ovarian cancer cells

Ovarian cancer is the leading cause of death from gynecologic illnesses worldwide. High-grade serous ovarian cancer (HGSOC) is a gynecological tumor that accounts for roughly 70% of ovarian cancer deaths in women. Runt-related transcription factor 1(RUNX1) proteins were identified with overexpression in the HGSOC. However, the roles of RUNX1 in the development of HGSOC are poorly understood. In this study, combined with whole-transcriptome analysis and multiple research methods, RUNX1 was identified as vital in developing HGSOC. RUNX1 knockdown inhibits the physiological function of ovarian cancer cells and regulates apoptosis through the FOXO1-Bcl2 axis. Down-regulated RUNX1 impairs EMT function through the EGFR-AKT-STAT3 axis signaling. In addition, RUNX1 knockdown can significantly increase the sensitivity to clinical drug therapy for ovarian cancer. It is strongly suggested that RUNX1 work as a potential diagnostic and therapeutic target for HGSOC patients with better prognoses and treatment options. It is possible to generate novel potential targeted therapy strategies and translational applications for serous ovarian carcinoma patients with better clinical outcomes.

Ovarian cancer relies on the PDGFRβ-fibronectin axis for tumorsphere formation and metastatic spread.

High-grade serous ovarian cancer (HGSOC) is the deadliest gynecological malignancy. The most common form of metastatic spread of HGSOC is transcoelomic dissemination. In this process, detached cells from the primary tumor aggregate as tumorspheres and promote the accumulation of peritoneal ascites. This represents an early event in HGSOC development and is indicative of poor prognosis. In this study, based on tumorspheres isolated from ascitic liquid samples from HGSOC patients, ovarian cancer spheroid 3D cultures, and in vivo models, we describe a key signal for tumorsphere formation in HGSOC. We report that platelet-derived growth factor receptor beta (PDGFRβ) is essential for fibronectin-mediated cell clustering of ovarian cancer cells into tumorspheres. This effect is mediated by the kinase NUAK family SNF1-like kinase 1 (NUAK1) and blocked by PDGFRβ pharmacological or genetic inhibition. In the absence of PDGFRβ, ovarian cancer cells can be provided with fibronectin by cancer-associated fibroblasts to generate chimeric spheroids. This work provides new insights that uncover potential targets to prevent peritoneal dissemination, the main cause of advanced disease in HGSOC patients.

Extracellular matrix in high-grade serous ovarian cancer: Advances in understanding of carcinogenesis and cancer biology.

High-grade serous ovarian cancer (HGSOC) is notoriously known as the "silent killer" of post-menopausal women as it has an insidious progression and is the deadliest gynaecological cancer. Although a dual origin of HGSOC is now widely accepted, there is growing evidence that most cases of HGSOC originate from the fallopian tube epithelium. In this review, we will address the fallopian tube origin and involvement of the extracellular matrix (ECM) in HGSOC development. There is limited research on the role of ECM at the earliest stages of HGSOC carcinogenesis. Here we aim to synthesise current understanding of the contribution of ECM to each stage of HGSOC development and progression, beginning at serous tubal intraepithelial carcinoma (STIC) precursor lesions and proceeding across key events including dissemination of tumourigenic fallopian tube epithelial cells to the ovary, survival of these cells in peritoneal fluid as multicellular aggregates, and colonisation of the ovary. Likewise, as part of the metastatic series of events, serous ovarian cancer cells survive travel in peritoneal fluid, attach to, migrate across the mesothelium and invade into the sub-mesothelial matrix of secondary sites in the peritoneal cavity. Halting cancer at the pre-metastatic stage and finding ways to stop the dissemination of ovarian cancer cells from the primary site is critical for improving patient survival. The development of drug resistance also contributes to poor survival statistics in HGSOC. In this review, we provide an update on the involvement of the ECM in metastasis and drug resistance in HGSOC. Interplay between different cell-types, growth factor gradients as well as evolving ECM composition and organisation, creates microenvironment conditions that promote metastatic progression and drug resistance of ovarian cancer cells. By understanding ECM involvement in the carcinogenesis and chemoresistance of HGSOC, this may prompt ideas for further research for developing new early diagnostic tests and therapeutic strategies for HGSOC with the end goal of improving patient health outcomes.

Abstract PR005: TP53 field defects in uterine fluid are associated with ovarian cancer risk

Abstract Background: High grade serous ovarian cancer (HGSC), the most common and aggressive type of ovarian cancer, is nearly always driven by TP53 mutations, which can be detected in uterine lavages using ultra-deep duplex sequencing. While this finding supports the development of a uterine lavage assay for early HGSC detection, age-related TP53 mutations compromise specificity. The goal of this study was to thoroughly characterize the nature of TP53 mutations identified in uterine lavage of women with and without HGSC to better understand TP53 clonal evolution during aging and to determine its association to HGSC. Methods: Uterine lavages were collected preoperatively in 54 “average-risk” women undergoing gynecological surgery for suspicious masses (34 women ultimately had HGSC, 20 were cancer free) and in 98 “high-risk” women undergoing risk-reducing salpingo-oopherectomy (17 were found to have HGSC or serous tubal intraepithelial carcinomas (STICs), 81 were cancer-free). Ultra-deep (&amp;gt;10,000x), ultra-accurate sequencing of TP53 was performed on uterine lavage DNA using duplex sequencing. Tumors and STICs were also duplex sequenced to determine TP53 tumor-driving mutations. The frequency of TP53 mutations and large TP53 mutant clones (those found in &amp;gt;2 duplex reads) was compared between women with and without HGSC. Results: The tumor-specific TP53 mutation was detected in 53% of lavages from average-risk women with HGSC and in 22% of lavages from high-risk women with HGSC/STICs. As in prior studies, TP53 biological background mutations were identified in nearly all women and their frequency was age-related. TP53 background mutations, however, were more abundant in women with prior chemotherapy, regardless of their cancer status or age. In women without prior chemotherapy and without high-risk of HGSC, having HGSC was associated with a significantly higher frequency of large TP53 mutant clones (p=0.007) and large TP53 mutant clones containing pathogenic mutations (p=0.007) or TP53 mutations commonly found in cancer (p=0.001). Interestingly, women at high risk of HGSC also carried high frequency of large and pathogenic TP53 mutant clones in lavage, even in those cases in which cancer or STICs were not identified. Conclusions: Ultra-sensitive duplex sequencing enabled detection of a patient’s HGSC or STIC driver mutations, respectively, in about half and a quarter of uterine lavages. However, of even greater interest, we observed a significant excess of large and pathogenic TP53 mutant clones in lavages of women with HGSC that were not present in the tumor. These results indicate that TP53 somatic evolution is associated with HGSC development and suggest that the measurement of TP53 mutant clones in uterine lavages harbors value as a predictor of ovarian cancer risk. Citation Format: Rosana Risques, Thomas H. Smith, Zachary K. Norgaard, Roniz Katz, Fang Yin Lo, Elizabeth K. Schmidt, Jacob E. Higgins, Martin Filipits, Intidhar Labidi-Galy, David Cibula, Lukáš Dostálek, Gabriel Jelenek, Magdalena Plch, Jiří Bouda, Alexander Mustea, Mateja Condic, Sabine Grill, Noreen Gleeson, Peter Oppelt, Gunda Pristauz-Telsnigg, Adriaan Vanderstichele, Siel Obrecht, Adam Rosenthal, Paul Speiser, Jesse Salk. TP53 field defects in uterine fluid are associated with ovarian cancer risk [abstract]. In: Proceedings of the AACR Special Conference on the Evolutionary Dynamics in Carcinogenesis and Response to Therapy; 2022 Mar 14-17. Philadelphia (PA): AACR; Cancer Res 2022;82(10 Suppl):Abstract nr PR005.

Single-cell myeloid diversity in human fallopian tube and its implications for early high grade serous ovarian cancer

Abstract The 5-year survival rate of high grade serous ovarian cancer (HGSOC) has remained below 40% for decades. This rises significantly to 90% when detected early. Increasing evidence suggests that HGSOC tumors originate in the fallopian tube (FT). However, little is known about FT’s immune cell heterogeneity and how it contributes to HGSOC development. Here we show a single-cell transcriptome analysis of non-malignant FT samples, revealing high monocyte diversity that is lost in HGSOC. FT monocyte subsets display distinct inflammatory gene signatures such as IL1A, CCL3/4 and others. Trajectory inference showed potential monocyte maturation steps that started with early cytokine/chemokine secreting monocytes that gain MHCII expression and develop into macrophages or dendritic cells. We found the macrophage-to-monocyte ratio is remarkably elevated in tumors compared to adjacent normal ovary and non-cancerous FT tissues in ours and publicly available scRNA-Seq. Intriguingly, analysis of FT of patients with BRCA1/2 germline mutations revealed half of these high-risk individuals are more like those found in HGSOC tumors than in normal FT. They also showed distinct T cell phenotypes in their FTs. Our data suggested that myeloid diversity, and their interactions with T cells in the FT, might contribute to early HGSOC development. Understanding tissue-of-origins immune microenvironment has a potential contribution to early cancer detection. We anticipate this work provides evidence of how myeloid cell plasticity induces tumorigenesis and can shape different tumor microenvironments. Supported by startup grants from UW-Madison School of Medicine and Public Health and UW-Madison Cellular and Molecular Pathology Graduate Training Program travel awards

TTK inhibition increases cisplatin sensitivity in high-grade serous ovarian carcinoma through the mTOR/autophagy pathway

High-grade serous ovarian cancer (HGSOC) is the most lethal gynecological malignancy. However, the molecular mechanisms underlying HGSOC development, progression, chemotherapy insensitivity and resistance remain unclear. Two independent GEO datasets, including the gene expression profile of primary ovarian carcinoma and normal controls, were analyzed to identify genes related to HGSOC development and progression. A KEGG pathway analysis of the differentially expressed genes (DEGs) revealed that the cell cycle pathway was the most enriched pathway, among which TTK protein kinase (TTK) was the only gene with a clinical-grade inhibitor that has been investigated in a clinical trial but had not been studied in HGSOC. TTK was also upregulated in cisplatin-resistant ovarian cancer cells from two other datasets. TTK is a regulator of spindle assembly checkpoint signaling, playing an important role in cell cycle control and tumorigenesis in various cancers. However, the function and regulatory mechanism of TTK in HGSOC remain to be determined. In this study, we observed TTK upregulation in patients with HGSOC. High TTK expression was related to a poor prognosis. Genetic and pharmacological inhibition of TTK impeded the proliferation of ovarian cancer cells by disturbing cell cycle progression and increasing apoptosis. TTK silencing increased cisplatin sensitivity by activating the mammalian target of rapamycin (mTOR) complex to further suppress cisplatin-induced autophagy in vitro. In addition, the enhanced sensitivity was partially diminished by rapamycin-mediated inhibition of mTOR in TTK knockdown cells. Furthermore, TTK knockdown increased the toxicity of cisplatin in vivo by decreasing autophagy. These findings suggest that the administration of TTK inhibitors in combination with cisplatin may lead to improved response rates to cisplatin in patients with HGSOC presenting high TTK expression. In summary, our study may provide a theoretical foundation for using the combination therapy of cisplatin and TTK inhibitors as a treatment for HGSOC in the future.

Progesterone Receptors Promote Quiescence and Ovarian Cancer Cell Phenotypes via DREAM in p53-Mutant Fallopian Tube Models.

The ability of ovarian steroids to modify ovarian cancer (OC) risk remains controversial. Progesterone is considered to be protective; recent studies indicate no effect or enhanced OC risk. Knowledge of progesterone receptor (PR) signaling during altered physiology that typifies OC development is limited. This study defines PR-driven oncogenic signaling mechanisms in p53-mutant human fallopian tube epithelia (hFTE), a precursor of the most aggressive OC subtype. PR expression in clinical samples of serous tubal intraepithelial carcinoma (STIC) lesions and high-grade serous OC (HGSC) tumors was analyzed. Novel PR-A and PR-B isoform-expressing hFTE models were characterized for gene expression and cell cycle progression, emboli formation, and invasion. PR regulation of the DREAM quiescence complex and DYRK1 kinases was established. STICs and HGSC express abundant activated phospho-PR. Progestin promoted reversible hFTE cell cycle arrest, spheroid formation, and invasion. RNAseq/biochemical studies revealed potent ligand-independent/-dependent PR actions, progestin-induced regulation of the DREAM quiescence complex, and cell cycle target genes through enhanced complex formation and chromatin recruitment. Disruption of DREAM/DYRK1s by pharmacological inhibition, HPV E6/E7 expression, or DYRK1A/B depletion blocked progestin-induced cell arrest and attenuated PR-driven gene expression and associated OC phenotypes. Activated PRs support quiescence and pro-survival/pro-dissemination cell behaviors that may contribute to early HGSC progression. Our data support an alternative perspective on the tenet that progesterone always confers protection against OC. STICs can reside undetected for decades prior to invasive disease; our studies reveal clinical opportunities to prevent the ultimate development of HGSC by targeting PRs, DREAM, and/or DYRKs.

Aberrant non-canonical WNT pathway as key-driver of high-grade serous ovarian cancer development

Aberrant non-canonical WNT pathway as key-driver of high-grade serous ovarian cancer development

Abstract GMM-039: BUILDING AN ORGANOID-BASED MODEL FOR OVARIAN CANCER

Abstract Over the last few years several studies led to a significant change in the field of ovarian cancer and it is currently believed that the fallopian tube and not the ovary surface epithelium (OSE) is the main origin of high-grade serous ovarian cancer (HG-SOC). Nevertheless, due to the lack of unique markers and adequate model systems the relative contribution of each tissue is not yet clear and the notion that OSE has a role in HG-SOC development was not cast aside altogether. In this work we have established novel organoid systems derived from both mouse OSE and oviduct (Ovi, the equivalent of human fallopian tube). These systems recapitulate their tissue of origin and demonstrate differences in medium requirements as well as gene expression. To establish comparable tumor progression models for both OSE and Ovi we used CRISPR-Cas9 technique and targeted commonly mutated genes in ovarian cancer (Trp53, Brca1, Nf1 and Pten). Thus, we were able to establish clones with different combinations of mutations. Histological, metaphase spread and gene expression analysis of the mutated organoid clones from both OSE and Ovi demonstrated different degrees of deviation from their wild type counterpart. This deviation became more evident as the amount of introduced mutations increased. Preliminary transplantation experiments showed that only triple mutants gave rise to tumors (Trp53, Brca1 and Pten or Trp53, Brca1 and Nf1). Moreover, Ovi mutant clones were more prone to grow into tumors in comparison to OSE as no tumors have been detected in mice transplanted with the OSE equivalent clones so far. Taken together, in this study we present the first comparable Ovi/OSE research platform that enables addressing questions related to origin and early stages of HG-SOC development. Citation Format: Kadi Lõhmussaar, Oded Kopper, Hans C. Clevers. BUILDING AN ORGANOID-BASED MODEL FOR 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 GMM-039.

Abstract 3557: miR-181a is a key driver of genomic instability and ovarian cancer tumorigenesis through the regulation of RB1

Abstract Epithelial ovarian cancer (EOC) is one of the deadliest gynecological cancers currently diagnosed in women with approximately 20,000 new cases and 15,000 deaths per year. Ovarian cancer can be stratified into distinct subtypes of which high-grade serous ovarian cancer (HGSOC) comprises 90% of all cases and has the highest mortality rate. Reducing the high mortality rate associated with HGSOC currently has two primary barriers: 1) most HGSOCs are diagnosed at a post-metastatic stage and 2) up to 70% of patients recur within 5 years. Both of these limitations are due to the fact that the drivers of tumor initiation are poorly understood. In order to change the status quo of the last 30 years, a new approach that focuses on understanding the origins of HGSOC is required. Our lab has recently discovered that miR-181a promotes key hallmarks of HGSOC progression in fallopian tube secretory epithelial cells (FTSECs) which are precursor cells of HGSOC. We show that enhanced expression of miR-181a in FTSECs results in increased proliferation, survival, and anchorage independent growth in vitro. Furthermore, FTSECs with miR-181a overexpression are able to form tumors in vivo whereas FTSECs that overexpress a control scramble miRNA cannot. Using cell cycle analysis, dynamic live-cell imaging, and SNP array analysis, we also found that miR-181a overexpression increases aneuploidy and genomic instability in FTSECs. We show that miR-181a promotes defects in nuclear structure, ruptures in the nuclear envelope, as well as mitotic and cytokinetic defects affecting proper chromosome segregation. A combination of global mRNA expression profiling and target prediction software identified the tumor suppressor retinoblastoma (RB1) as a target for miR-181a mediated FTSEC tumorigenesis. Using an RB1 3’UTR luciferase assay, along with stable expression of an shRNA against RB1 in FTSECs, we are able to show that miR-181a directly targets RB1 and that knockdown of RB1 phenocopies miR-181a mediated tumorigenesis. Taken together, our data shed light on a novel mechanism that promotes genomic instability and tumorigenesis in the early phases of HGSOC development. Our results suggest miR-181a as a promising early detection biomarker as well as a prognostic tool to guide patient treatment. Citation Format: Matthew Knarr, Lily Kwiatkowski, Anil Nagaraj, Ronny Drapkin, Analisa DiFeo. miR-181a is a key driver of genomic instability and ovarian cancer tumorigenesis through the regulation of RB1 [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 3557.

Downregulation of LINC00515 in high-grade serous ovarian cancer and its relationship with platinum resistance.

Aim: To investigate the expression of long intergenic noncoding RNA 00515 (LINC00515) in high-grade serous ovarian cancer (HGSOC) and its potential correlation with platinum resistance. Patients & methods: Expression of LINC00515 in HGSOC (n=115) and normal (n=19) tissues was detected via quantitative real-time PCR (qRT-PCR). We further explored the statistical significance of the relationship between LINC00515 expression and platinum resistance in HGSOC. Results: LINC00515 was gradually downregulated in the order of normal > platinum-sensitive > platinum-resistant tissue (p < 0.05). Results demonstrated that LINC00515 downregulation was correlated with platinum resistance and relapse-free survival (RFS) of HGSOC (p < 0.05). Conclusion: LINC00515 downregulation is correlated with HGSOC development, platinum resistance and RFS, supporting its utility as a potential biomarker to predict platinum resistance and prognosis of RFS.

Abstract B36: FOXM1 induces DNA replication stress, and its bidirectional gene partner RHNO1 participates in the DNA replication stress response, in high-grade serous ovarian cancer

Abstract Purpose: FOXM1 is located at 12p13.33, which shows copy number gains in the majority of high-grade serous ovarian cancer (HGSC) cases. The 12p13.33 amplicon contains 33 genes, some of which may cooperate with FOXM1 to exert oncogenic function. Although FOXM1 overexpression is associated with genomic instability in cancer, whether FOXM1 contributes directly to this phenotype is unclear. We hypothesized that FOXM1 induces DNA replication stress (DRS), resulting in ATR-CHK1 activation. Intriguingly, we noted that RHNO1, a component of the 9-1-1 complex required for ATR-CHK1 activation, is contained within the 12p13.33 amplicon and is arranged in a head-to-head orientation with FOXM1. Here, we characterized the FOXM1/RHNO1 bidirectional promoter, FOXM1/RHNO1 expression, and determined the role of FOXM1/RHNO1 in DRS, the DRS response, and clonogenic growth of HGSC cells. Methods: We used reporter assays to characterize the FOXM1/RHNO1 bidirectional promoter and FOXM1 transcriptional activity. We analyzed copy number, mRNA, and protein expression datasets in TCGA, CCLE, and GTEX. We measured FOXM1/RHNO1 expression in HGSC cell lines and tumors. We overexpressed FOXM1 in human immortalized fallopian tube epithelial (FTE) cells to determine its contribution to DRS and DNA damage. We knocked down RHNO1 in HGSC cells to determine its contribution to the DRS response and clonogenic growth. We performed Western blot analyses to measure markers of DRS and DNA damage. We characterized FOXM1-induced DNA damage at single-cell resolution using Comet assays and flow cytometry measurement of γ-H2AX. Results: FOXM1/RHNO1 showed copy number gains or amplifications in 58% of TCGA HGSC tumors, and FOXM1/RHNO1 mRNA expression significantly correlated in TCGA HGSC tumors, CCLE HGSC lines, and GTEX normal tissues. The FOXM1/RHNO1 bidirectional promoter showed balanced activity in each direction in FTE and HGSC cells, and bidirectional promoter activity correlated with endogenous mRNA expression. TCGA HGSC data indicated that FOXM1 expression associates with markers of DNA replication, global copy number alterations, and CHK1-Ser345-P, a canonical marker of DRS. In agreement, FOXM1 overexpression in FTE cells induced phosphorylation of ATR-Thr1989, CHK1-Ser317/345, H2AX-Ser139, and the proportion of DNA in Comet tails. In contrast, a DNA-binding domain mutant of FOXM1 did not induce DRS or DNA damage. RHNO1 knockdown attenuated CHK1-Ser345-P in response to DRS and RHNO1 shRNA knockdown or CRISPR-Cas9 knockout severely reduced HGSC cell clonogenic growth. Importantly, the effects of RHNO1 disruption were rescued by WT RHNO1 expression, but not by a RHNO1 mutant defective for interaction with the 9-1-1 complex. Conclusion: Our data reveal that FOXM1/RHNO1 share a bidirectional promoter and that this may account for their frequent coexpression in HGSC. FOXM1 induces DRS, and this is dependent on its ability to bind DNA. Conversely, RHNO1 contributes to ATR-CHK1 signaling and promotes the clonogenic growth of HGSC cells. We hypothesize that balanced FOXM1/RHNO1 expression promotes HGSC development and progression. Ongoing studies are characterizing the impact of FOXM1/RHNO1 on DRS and genomic instability in model systems. Finally, our data suggest that the ATR-CHK1 pathway is a synthetic lethal vulnerability in HGSC tumors that overexpress FOXM1. Citation Format: Carter J. Barger, Linda Chee, Connor Branick, Kunle Odunsi, Ronny Drapkin, Adam R. Karpf. FOXM1 induces DNA replication stress, and its bidirectional gene partner RHNO1 participates in the DNA replication stress response, in high-grade serous ovarian cancer. [abstract]. In: Proceedings of the AACR Conference: Addressing Critical Questions in Ovarian Cancer Research and Treatment; Oct 1-4, 2017; Pittsburgh, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(15_Suppl):Abstract nr B36.

Directed Differentiation of Human Induced Pluripotent Stem Cells into Fallopian Tube Epithelium

The fallopian tube epithelium (FTE) has been recognized as a site of origin of high-grade serous ovarian cancer (HGSC). However, the absence of relevant in vitro human models that can recapitulate tissue-specific architecture has hindered our understanding of FTE transformation and initiation of HGSC. Here, induced pluripotent stem cells (iPSCs) were used to establish a novel 3-dimensional (3D) human FTE organoid in vitro model containing the relevant cell types of the human fallopian tube as well as a luminal architecture that closely reflects the organization of fallopian tissues in vivo. Modulation of Wnt and BMP signaling directed iPSC differentiation into Müllerian cells and subsequent use of pro-Müllerian growth factors promoted FTE precursors. The expression and localization of Müllerian markers verified correct cellular differentiation. An innovative 3D growth platform, which enabled the FTE organoid to self-organize into a convoluted luminal structure, permitted matured differentiation to a FTE lineage. This powerful human-derived FTE organoid model can be used to study the earliest stages of HGSC development and to identify novel and specific biomarkers of early fallopian tube epithelial cell transformation.

Abstract MIP-044: FOXM1 INDUCED REPLICATION STRESS IS MITIGATED BY ITS BIDIRECTIONAL GENE PARTNER, RHNO1, IN HIGH GRADE SEROUS OVARIAN CANCER

Abstract PURPOSE: FOXM1 is located at 12p13.33, a significantly amplified locus in high-grade serous ovarian cancer (HGSC). The 12p13.33 amplicon contains ~33 genes, which may cooperate with FOXM1 to exert oncogenic function. Although FOXM1 expression is associated with cancer genomic instability, it is unclear whether FOXM1 causes this phenotype and, if so, by what mechanism. We hypothesized that FOXM1 induces replication stress, which is the slowing or stalling of replication forks. We further noted that RHNO1, a component of the 9-1-1 complex required for ATR-CHK1 signaling, is contained within the 12p13.33 amplicon, and arranged in a head-to-head orientation with FOXM1. Here, we characterized the FOXM1-RHNO1 bidirectional promoter, FOXM1 and RHNO1 expression patterns in HGSC, and determined the relationship between FOXM1 and RHNO1 in replication stress. METHODS: We used 5' RACE and a luciferase reporter construct to characterize the FOXM1-RHNO1 bidirectional promoter. We analyzed copy number, mRNA and protein expression datasets in TCGA HGSC and additional TCGA cancers. We measured FOXM1 and RHNO1 expression in HGSC cell lines and primary HGSC tissues. We overexpressed FOXM1 in human immortalized fallopian tube epithelial (FTE) cells to determine its contribution to replication stress. We used RHNO1 knockdown to dissect its functional contribution to ATR-CHK1 signaling in HGSC cells. RESULTS: FOXM1 and RHNO1 were co-amplified in ~12% of HGSC and their mRNA expressions were highly correlated. The FOXM1-RHNO1 bidirectional promoter showed similar activity in each direction in HGSC cells, and correlated with mRNA expression. Analysis of TCGA HGSC data revealed that FOXM1 associates with markers of DNA replication and CHK1-Ser345 phosphorylation, a canonical marker of replication stress. FOXM1 overexpression in immortalized FTE cells induced CHK1-Ser345 phosphorylation. RHNO1 knockdown attenuated CHK1-Ser345 phosphorylation in response to replication stress, and, importantly, reduced clonogenic growth in FOXM1 overexpressing HGSC cells. CONCLUSIONS: Our data reveal that FOXM1 and RHNO1 share a bidirectional promoter resulting in their frequent co-expression. FOXM1 induces replication stress whereas RHNO1 is necessary for efficient ATR-CHK1 signaling. We hypothesize that balanced FOXM1 and RHNO1 expression promotes HGSC development and progression. Ongoing studies are characterizing the impact of FOXM1 and RHNO1 on replication stress and genomic instability. Finally, our findings suggest ATR-CHK1 signaling as a potential therapeutic vulnerability in FOXM1 activated HGSC. Citation Format: Carter J Barger, Linda Chee, Ronny Drapkin, Kunle Odunsi, Adam R. Karpf. FOXM1 INDUCED REPLICATION STRESS IS MITIGATED BY ITS BIDIRECTIONAL GENE PARTNER, RHNO1, IN HIGH GRADE SEROUS OVARIAN CANCER [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-044.

The Molecular Fingerprint of High Grade Serous Ovarian Cancer Reflects Its Fallopian Tube Origin

High grade serous ovarian cancer (HGSC), the most lethal and frequent type of epithelial ovarian cancer (EOC), has poor long term prognosis due to a combination of factors: late detection, great metastatic potential and the capacity to develop resistance to available therapeutic drugs. Furthermore, there has been considerable controversy concerning the etiology of this malignancy. New studies, both clinical and molecular, strongly suggest that HGSC originates not from the surface of the ovary, but from the epithelial layer of the neighboring fallopian tube fimbriae. In this paper we summarize data supporting the central role of fallopian tube epithelium in the development of HGSC. Specifically, we address cellular pathways and regulatory mechanisms which are modulated in the process of transformation, but also genetic changes which accumulate during disease progression. Similarities between fallopian tube mucosa and the malignant tissue of HGSC warrant a closer analysis of homeostatic mechanisms in healthy epithelium in order to elucidate key steps in disease development. Finally, we highlight the importance of the cancer stem cell (CSC) identification and understanding of its niche regulation for improvement of therapeutic strategies.