Model Of High-grade Serous Ovarian Cancer Research Articles

The expression level of VEGFR2 regulates mechanotransduction, tumor growth and metastasis of high grade serous ovarian cancer cells

Recent data shows that alterations in the expression and/or activation of the vascular endothelial growth factor receptor 2 (VEGFR2) in high grade serous ovarian cancer (HGSOC) modulate tumor progression. However, controversial results have been obtained, showing that in some cases VEGFR2 inhibition can promote tumorigenesis and metastasis. Thus, it is urgent to better define the role of the VEGF/VEGFR2 system to understand/predict the effects of its inhibitors administered as anti-angiogenic in HGSOC. Here, we modulated the expression levels of VEGFR2 and analyzed the effects in two cellular models of HGSOC. VEGFR2 silencing (or its pharmacological inhibition) promote the growth and invasive potential of OVCAR3 cells in vitro and in vivo. Consistent with this, the low levels of VEGFR2 in OV7 cells are associated with more pronounced proliferative and motile phenotypes when compared to OVCAR3 cells, and VEGFR2 overexpression in OV7 cells inhibits cell growth. In vitro data confirmed that VEGFR2 silencing in OVCAR3 cells favors the acquisition of an invasive phenotype by loosening cell-ECM contacts, reducing the size and the signaling of focal adhesion contacts (FAs). This is translated into a reduced FAK activity at FAs, ECM-dependent alterations of mechanical forces through FAs and YAP nuclear translocation. Together, the data show that low expression, silencing or inhibition of VEGFR2 in HGSOC cells alter mechanotransduction and lead to the acquisition of a pro-proliferative/invasive phenotype which explains the need for a more cautious use of anti-VEGFR2 drugs in ovarian cancer.

Oncolytic adenovirus MEM-288 encoding membrane-stable CD40L and IFNβ induces an anti-tumor immune response in high grade serous ovarian cancer

Single agent immune checkpoint inhibitors have been ineffective for patients with advanced stage and recurrent high grade serous ovarian cancer (HGSOC). Using pre-clinical models of HGSOC, we evaluated the anti-tumor and immune stimulatory effects of an oncolytic adenovirus, MEM-288. This conditionally replicative virus encodes a modified membrane stable CD40L and IFNβ. We demonstrated this virus successfully infects HGSOC cell lines and primary human ascites samples in vitro. We evaluated the anti-tumor and immunostimulatory activity in vivo in immune competent mouse models. Intraperitoneal delivery of MEM-288 decreased ascites and solid tumor burden compared to controls, and treatment generated a systemic anti-tumor immune response. The tumor microenvironment had a higher proportion of anti-tumor macrophages and decreased markers of angiogenesis. MEM-288 is a promising immunotherapy agent in HGSOC, with further pre-clinical studies required to understand the mechanism of action in the peritoneal microenvironment and clinical activity in combination with other therapies.

Palladium(II)-Indenyl Complexes Bearing N-Heterocyclic Carbene (NHC) Ligands as Potent and Selective Metallodrugs toward High-Grade Serous Ovarian Cancer Models.

In this study, we synthesized novel Pd(II)-indenyl complexes using various N-heterocyclic carbene (NHC) ligands, including chelating NHC-picolyl, NHC-thioether, and diNHC ligands, and two monodentate NHCs. Transmetalation reactions between a Pd(II)-indenyl precursor and silver-NHC complexes were generally employed, except for chelating diNHC derivatives, which required direct reaction with bisimidazolium salts and potassium carbonate. Characterization included NMR, HRMS analysis, and single-crystal X-ray diffraction. In vitro on five ovarian cancer cell lines showed notable cytotoxicity, with IC50 values in the micro- and submicromolar range. Some compounds exhibited intriguing selectivity for cancer cells due to higher tumor cell uptake. Mechanistic studies revealed that monodentate NHCs induced mitochondrial damage while chelating ligands caused DNA damage. One chelating NHC-picolyl ligand showed promising cytotoxicity and selectivity in high-grade serous ovarian cancer models, supporting its consideration for preclinical study.

Abstract 5909: Sulindac exhibits anti-proliferative effects in pre-clinical models of ovarian cancer

Abstract Objectives: Given the intricate relationship between inflammation and ovarian cancer (OC) development and progression, anti-inflammatory drugs may have potential in the prevention and treatment of OC. Sulindac exhibits potent anti-inflammatory effects through inhibition of COX1/COX2 pathways and promising anti-tumor activity in pre-clinical models of colorectal and endometrial cancer. Thus, we investigated the efficacy of sulindac as an anti-tumorigenic agent in OC pre-clinical cell and mouse models. Methods: The human OC cell lines, MES and OVCAR5, and the K18-gT121+/-;p53fl/fl;Brca1fl/fl (KpB) mouse model of high-grade serous OC were used. Cellular proliferation was assessed by MTT and colony count assays. Apoptosis was assessed using cleaved caspase 3, 8, and 9 assays. To measure cellular stress, production of reactive oxygen species was measured by DCFH-DA assay, and the JC1 assay was used to assess changes in mitochondrial membrane potential. Cellular adhesion was evaluated by laminin assay, and cellular migration was determined by wound healing assay. Western immunoblotting was used to assess the effects of sulindac on downstream targets related to cellular stress, apoptosis, cellular invasion potential, cell cycle control, and inflammation. The KpB mice were treated with sulindac (7.5 mg/kg, oral gavage, daily) or placebo for four weeks. Results: Sulindac inhibited cellular proliferation in a dose-dependent manner in the MES and OVCAR5 cells, with IC50s of 75.3 and 75.69 μM, respectively. Sulindac (100 μM) reduced colony formation by 81% in the MES cells and by 49% in the OVCAR5 cells (p<0.01). Treatment of MES and OVCAR5 cells with sulindac increased ROS production and decreased mitochondrial membrane potential, in a dose-dependent manner (p<0.01). Sulindac induced activity of cleaved caspase 3, 8, and 9, in MES and OVCAR5 cells (p<0.01). In addition, sulindac (100 μM) effectively decreased cellular adhesion by 31% in MES cells and by 23% in OVCAR5 cells (p<0.01). These results were confirmed by Western immunoblotting demonstrating that sulindac downregulated the anti-apoptotic proteins Bcl-xl and Mcl-1 and upregulated the pro-apoptotic proteins Bax and cellular stress proteins Bip, ATF-4, and PDI, in both cell lines. Sulindac downregulated expression of several epithelial-mesenchymal transition proteins in both cell lines, including beta-catenin, snail, and slug. Sulindac also downregulated expression of cell cycle proteins CDK4, CDK5, and Cyclin D1 and inflammatory protein COX-2 in both cell lines. After 4 wks of treatment, sulindac significantly inhibited tumor growth by 71% (1.89 g vs 0.54 g, p<0.01) in KpB mice. Conclusions: Our results find that sulindac exhibited anti-tumorigenic effects in OC cell lines and the KpB OC mouse model. Given these promising pre-clinical results, further studies on the repurposing of sulindac for the prevention and treatment of OC is warranted. Citation Format: Nikita Sinha, Shuning Chen, Jennifer Haag, Xiaochang Shen, Boer Deng, Ziyi Zhao, Chunxiao Zhou, Victoria Bae-Jump. Sulindac exhibits anti-proliferative effects in pre-clinical models of ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5909.

Abstract 231: Live cell painting of drug responses in high grade serous cancer organoids

Abstract While most patients with high grade serous ovarian cancer (HGSC) respond to platinum-based chemotherapy, the response is rarely durable and recurrence almost inevitable. A characteristic of HGSC is defective DNA repair. A class of drugs called PARP inhibitors (PARPi) exploit this vulnerability and have proven useful in delaying recurrence. However, resistance is inevitable. In models of HGSC a protein that frequently confers resistance is called Bcl-xL, a member of the Bcl-2 family of proteins that prevent apoptosis. If treating the patients with a PARPi makes cancer cells dependent on Bcl-xL then adding an inhibitor of Bcl-xL to their treatment would be sufficient to cause the cancer cells to die. To test this, we have initiated companion studies for a clinical trial in which patients that have had a recurrence after receiving platinum-based therapy will first be treated with the PARPi Olaparib and then, an inhibitor of Bcl-xL, Navitoclax, will be added to their course of treatment. The idea is that for some women this will provide the one-two-punch needed to eliminate the cancer or at least dramatically prolong response. However, Bcl-xL is only one of the five known inhibitors of apoptosis. To identify which women will benefit most from adding Navitoclax to their treatment we need a biomarker(s). An ideal biomarker would also let us determine for other women which inhibitor of Bcl-2 proteins would be best combined with a PARPi. Our hypothesis is that patient derived organoids can be used as a pragmatic way to identify for individual patients which Bcl-2 protein inhibitor will synergize with a PARPi to optimize treatment. We are using organoids to develop biomarkers for High Grade Serous Cancer (HGSC) treatment response. Organoids generated from biopsy samples acquired prior to treatment for HGSC promise to be efficient and reliable experimental models that recapitulate in vitro patient tumors faithfully enough to facilitate translation to therapeutic decisions for patients. By adapting the relatively new technique of conditional reprogramming and combining it with novel methods for cell aggregation and hydrogel based synthetic ECM supports we can reproducibly generate HGSC patient-specific tumor organoids models in weeks with greater than 90% success. Organoids grown 384 well format are stained with novel non-toxic dyes enabling live cell painting of chemoresponses to drugs alone and in combination with drugs targeting anti-apoptotic proteins. Our data suggest that this approach captures the inherent heterogeneity of the disease, albeit local to the sampled site. We are now employing deep learning AI algorithms to enable automated analyses of 3D confocal image stacks of organoids to infer drug responses that will be compared to patient responses in ongoing clinical trials. Citation Format: David W. Andrews, Betty Li, Wiebke Schormann, Alla Buzina, Lilian Gien, Helen MacKay. Live cell painting of drug responses in high grade serous cancer organoids [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 231.

Inhibition of palmitoyltransferase ZDHHC12 sensitizes ovarian cancer cells to cisplatin through ROS-mediated mechanisms.

Platinum-based therapies have revolutionized the treatment of high-grade serous ovarian cancer (HGSOC). However, high rates of disease recurrence and progression remain a major clinical concern. Impaired mitochondrial function and dysregulated reactive oxygen species (ROS), hallmarks of cancer, hold potential as therapeutic targets for selectively sensitizing cisplatin treatment. Here, we uncover an oncogenic role of the palmitoyltransferase ZDHHC12 in regulating mitochondrial function and ROS homeostasis in HGSOC cells. Analysis of The Cancer Genome Atlas (TCGA) ovarian cancer data revealed significantly elevated ZDHHC12 expression, demonstrating the strongest positive association with ROS pathways among all ZDHHC enzymes. Transcriptomic analysis of independent ovarian cancer datasets and the SNU119 cell model corroborated this association, highlighting a strong link between ZDHHC12 expression and signature pathways involving mitochondrial oxidative metabolism and ROS regulation. Knockdown of ZDHHC12 disrupted this association, leading to increased cellular complexity, ATP levels, mitochondrial activity, and both mitochondrial and cellular ROS. This dysregulation, achieved by the siRNA knockdown of ZDHHC12 or treatment with the general palmitoylation inhibitor 2BP or the fatty acid synthase inhibitor C75, significantly enhanced cisplatin cytotoxicity in 2D and 3D spheroid models of HGSOC through ROS-mediated mechanisms. Markedly, ZDHHC12 inhibition significantly augmented the anti-tumor activity of cisplatin in an ovarian cancer xenograft tumor model, as well as in an ascites-derived organoid line of platinum-resistant ovarian cancer. Our data suggest the potential of ZDHHC12 as a promising target to improve the outcome of HGSOCs in response to platinum-based chemotherapy.

Comparative analysis of syngeneic mouse models of high-grade serous ovarian cancer.

Ovarian cancers exhibit high rates of recurrence and poor treatment response. Preclinical models that recapitulate human disease are critical to develop new therapeutic approaches. Syngeneic mouse models allow for the generation of tumours comprising the full repertoire of non-malignant cell types but have expanded in number, varying in the cell type of origin, method for transformation, and ultimately, the properties of the tumours they produce. Here we have performed a comparative analysis of high-grade serous ovarian cancer models based on transcriptomic profiling of 22 cell line models, and intrabursal and intraperitoneal tumours from 12. Among cell lines, we identify distinct signalling activity, such as elevated inflammatory signalling in STOSE and OVE16 models, and MAPK/ERK signalling in ID8 and OVE4 models; metabolic differences, such as reduced glycolysis-associated expression in several engineered ID8 subclones; and relevant functional properties, including differences in EMT activation, PD-L1 and MHC class I expression, and predicted chemosensitivity. Among tumour samples, we observe increased variability and stromal content among intrabursal tumours. Finally, we predict differences in the microenvironment of ID8 models engineered with clinically relevant mutations. We anticipate that this work will serve as a valuable resource, providing new insight to help select models for specific experimental objectives.

MiR-146a inhibits ovarian tumor growth in vivo via targeting immunosuppressive neutrophils and enhancing CD8+ T cell infiltration

Immunotherapies have emerged as promising strategies for cancer treatment. However, existing immunotherapies have poor activity in high-grade serous ovarian cancer (HGSC) due to the immunosuppressive tumor microenvironment and the associated low tumoral CD8+ Tcell (CTL) infiltration. Through multiple lines of evidence, including integrative analyses of human HGSC tumors, we have identified miR-146a as a master regulator of CTL infiltration in HGSC. Tumoral miR-146a expression is positively correlated with anti-cancer immune signatures in human HGSC tumors, and delivery of miR-146a to tumors resulted in significant reduction in tumor growth in both ID8-p53-/- and IG10 murine HGSC models. Increasing miR-146a expression in tumors improved anti-tumor immune responses by decreasing immune suppressive neutrophils and increasing CTL infiltration. Mechanistically, miR-146a targets IL-1 receptor-associated kinase 1 and tumor necrosis factor receptor-associated factor 6 adaptor molecules of the transcription factor nuclear factor κB signaling pathway in ID8-p53-/- cells and decreases production of the downstream neutrophil chemoattractant, C-X-C motif chemokine ligand 1. In addition to HGSC, tumoral miR-146a expression also correlates strongly with CTL infiltration in other cancer types including thyroid, prostate, breast, and adrenocortical cancers. Altogether, our findings highlight the ability of miR-146a to overcome immune suppression and improve CTL infiltration in tumors.

Exactis-03: A phase I trial of the combination of olaparib and navitoclax in women with high grade serous ovarian cancer and triple negative breast cancer.

TPS5623 Background: Identifying new therapeutic options for patients (pts) with high grade serous ovarian cancer (HGSC) and triple negative breast cancer (TNBC) is a priority. For pts with pathogenic variants in BRCA, the PARP inhibitor (PARPi) olaparib is used to treat TNBC and as maintenance for HGSC. PARPi can induce a senescence-like phenotype in cancer cells with cell survival dependent on anti-apoptotic proteins. The intrinsic apoptotic pathway is regulated by the Bcl-2 family composed of anti-apoptotic proteins (including Bcl-2, Bcl-xL), pro-apoptotic effectors and the pro-apoptotic BH3-only proteins. Increased expression of Bcl-xL occurs in 88% of HGSC. Olaparib and navitoclax, a Bcl-2/Bcl-xL inhibitor, are synergistic in pre clinical models of HGSC and TNBC. Exactis- 03 investigates targeting, olaparib-induced sensecence as a treatment strategy for pts with HGSC and TNBC. Methods: Exactis-03 is a multi-centre phase I trial determining if olaparib can be safely combined with navitoclax in pts with TNBC who have somatic or germline mutations in BRCA1/2 or PALB2 and pts with recurrent HGSC who have progressed ≥ 6 months since their last platinum based chemotherapy. Additional eligibility criteria include : ≥3 prior lines of treatment for TNBC (no limit for HGSC); for pts with HGSC prior PARPi is allowed provided there was no progression on or ≤6 months since discontinuation of the PARPi; ECOG PS ≤2; ability to absorb study medication and pts must be willing and able to undergo study related procedures. The primary endpoint is identification of the recommended phase II dose (RP2D) of olaparib combined with navitoclax. Olaparib 200mg bid is administered alone for the first 2 weeks. Tumor biopsies will be performed at baseline and on day 7-12 (prior to navitoclax) to evaluate senescence and apoptosis biomarkers and to create 3D organoids and ex vivo microdissected tumor (MDT) models for functional assessment of drug response. Navitoclax is dose escalated with a fixed dose of olaparib in 28-day cycles with 3 pts initially treated at each dose level. If no dose limiting toxicity (DLT) is observed, the dose level will be escalated until ≥ 1/3 or ≥ 2/6 patients experience DLT. The RP2D will be defined as the dose level below the one where ≥ 1/3 or ≥ 2/6 patients experience DLT. The 2-week lead-in with olaparib alone and one full cycle of the combination (navitoclax/olaparib) must be completed before dose escalation is permitted. Blood samples are collected for pharmacokinetics and serial evaluation of plasma biomarkers. There is an optional tumor biopsy on progression. Exploratory objectives include determining levels of pro- and anti- apoptotic proteins in biopsy samples and evaluation of cell fate decision biomarkers in biopsy tissue and blood (senescence secretome). Patient-derived organoids and ex vivo MDT will be used to explore drug response and sequencing (NCT05358639). Clinical trial information: NCT05358639 .

Abstract 206: Organoid models for predicting drug response in high grade serous and triple negative breast cancer

Abstract While most patients with high grade serous ovarian cancer (HGSC) respond to platinum-based chemotherapy, the response is rarely durable and recurrence almost inevitable. Women with triple negative breast cancer (TNBC) urgently require effective therapeutic options. In women with HGSC and TNBC (with mutations in BRCA1/2) treatment with a Poly-ADP-ribose inhibitor (PARPi) has emerged as a standard of care. In models of HGSC and TNBC senescence may play a role in PARPi resistance with i Bcl-xL, a member of the Bcl-2 family of proteins, preventing apoptosis. Therefore, we have initiated a clinical trial whereby a PARPi and then, an inhibitor of Bcl-xL, Navitoclax, will be added to their course of treatment [NCT05358639]. Bcl-xL is only one of the five known inhibitors of apoptosis, at present we do not know in vivo how these will impact the efficacy of the PARPi/Navitoclax combination or if they will provide other targets for effective therapy. Our hypothesis is that patient derived organoids can be used as a pragmatic way to assess the efficacy of new drugs and to identify for individual patients which drug(s) and drug combinations are likely to be most efficacious. In particular, with reference to the clinical trial, identify for individual patients which Bcl-2 protein inhibitor will synergize with a PARPi to optimize treatment. Currently we are using organoids to test novel drugs and drug combinations and to develop biomarkers for HGSC and TNBC treatment response. A limitation to the use of organoids generated from biopsy samples is the lack of efficient and reliable experimental models that recapitulate in vitro patient tumors faithfully enough to facilitate translation to therapeutic decisions for patients. By adapting the relatively new technique of conditional reprogramming and combining it with novel hydrogel based synthetic ECM supports we can reproducibly generate HGSC and TNBC patient-specific tumor organoids models in two weeks with greater than 90% success. Organoids grown in 384 or 1536 well format are stained with novel non-toxic dyes and chemoresponses to drugs are inferred from automatically acquired 3D confocal image stacks using deep learning AI algorithms that enable automated analyses. Our data suggest that this approach captures the inherent heterogeneity of the disease, albeit local to the sampled site. We are now employing deep learning AI algorithms to enable automated analyses of 3D confocal image stacks of organoids and infer drug responses that will be compared to patient responses in the clinical trial. Citation Format: Helen J. MacKay, Alla Buzina, Betty Li, Lilian Gien, David Andrews. Organoid models for predicting drug response in high grade serous and triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 206.

Abstract 2182: The evolution of high grade serous ovarian cancer under the pressure of non-cytotoxic and cytotoxic treatment

Abstract Introduction: High-grade serous ovarian cancer (HGSOC) is driven by loss of TP53 and genome instability . Despite the recent success of PARP inhibitors, advanced BRCA mutant and homologous recombination repair deficient (HRD) HGSOC, chemotherapy remains the first line treatment. Little is known about how chemotherapy exposure alters tumor heterogeneity and subsequent response to targeted therapies. Certain mutations may survive the exposure of chemotherapy better than others. The question of whether targeted therapies should be given before or after response to chemotherapy also remains unanswered. We use the principles of natural selection to investigate how HGSOC evolves over time and selection operates on clones in the context of cytotoxic/non-cytotoxic combination therapies, and what changes in genomes/transcriptomes at the single cell level drive tumor progression. Methods: Cell lines ID8 Trp53 −/−; Brca1 −/− and WT were used to represent defective/proficient homologous recombination were given intraperitoneally to C57B6 mice to develop HGSOC models. Transfected Luciferase expression in the cells used to monitor tumor response to olaparib (Ola)+/- Bevacizumab (BEV-various doses) +/- Atezolizumab (ATz) combinations by bioluminescence imaging (BLI). Ascitic fluid and mouse organs were harvested for the evidence of seeding and identification of biomarkers. In addition, 10 treatment naïve HGSOC PDX were developed in immunodeficient mice and treated with either cisplatin or olaparib. Single-cell whole-genome sequencing (scWGS) was performed using direct library preparation (DLP+). Hierarchical clustering and Sitka are used to identify the clonal structure of each condition following treatment. Phylogenetic tree was computed using copy number data. Results: In the BRCA WT HRp study group, the greatest response was seen in the triplet Ola+BEV+ATz combinations and interestingly no significant differences were observed using a lower dose of BEV. Furthermore, from scWGS data of PDX passages we captured initial clonal heterogeneity leading to emergent clones. We found evolving copy number changes on chromosome 19, 8, 3 and loss of heterozygosity of TP53. Conclusion: The triplet combination of low-dose-intensity bevacizumab with other non-cytotoxic drugs was an effective regimen for BRCA WT syngeneic mouse tumors. In HGSOC PDX, we are able to capture diversification between HGSOC PDX passages-specifically after drug exposures. Citation Format: Farhia Kabeer, Goldman Lam, Naila Adam, Maxwell Douglas, Amal El-Naggar, Forouh Kalantari, Mengke Han, Vinci Au, Michael Van Vliet, Cindy Shen, Sean Beaty, Daniel Lai, Andy Mungall, Richard Moore, Sam Aparicio, Andrew Roth, David Huntsman, Yvette Drew. The evolution of high grade serous ovarian cancer under the pressure of non-cytotoxic and cytotoxic treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2182.

Axl and Vascular Endothelial Growth Factor Receptors Exhibit Variations in Membrane Localization and Heterogeneity Across Monolayer and Spheroid High-Grade Serous Ovarian Cancer Models.

Vascular endothelial growth factor receptors (VEGFRs) and Axl are receptor tyrosine kinases (RTK) that are targeted in ovarian cancer therapy. Two-dimensional monolayer culture and three-dimensional spheroids are common models for RTK-targeted drug screening: monolayers are simple and economical while spheroids include several genetic and histological tumor features. RTK membrane localization dictates RTK signaling and drug response, however, it is not characterized in these models. We quantify plasma membrane RTK concentrations and show differential RTK abundance and heterogeneity in monolayers versus spheroids. We show VEGFR1 concentrations on the plasma membrane to be 10 times higher in OVCAR8 spheroids than in monolayers; OVCAR8 spheroids are more heterogeneous than monolayers, exhibiting a bimodal distribution of a low-Axl (6200/cell) and a high-Axl subpopulation (25,000/cell). In addition, plasma membrane Axl concentrations differ by 100 times between chemosensitive (OVCAR3) and chemoresistant (OVCAR8) cells and by 10 times between chemoresistant cell lines (OVCAR5 vs. OVCAR8). These systematic findings can guide ovarian cancer model selection for drug screening.

The microtubule inhibitor eribulin demonstrates efficacy in platinum-resistant and refractory high-grade serous ovarian cancer patient-derived xenograft models.

Despite initial response to platinum-based chemotherapy and PARP inhibitor therapy (PARPi), nearly all recurrent high-grade serous ovarian cancer (HGSC) will acquire lethal drug resistance; indeed, ~15% of individuals have de novo platinum-refractory disease. To determine the potential of anti-microtubule agent (AMA) therapy (paclitaxel, vinorelbine and eribulin) in platinum-resistant or refractory (PRR) HGSC by assessing response in patient-derived xenograft (PDX) models of HGSC. Of 13 PRR HGSC PDX, six were primary PRR, derived from chemotherapy-naïve samples (one was BRCA2 mutant) and seven were from samples obtained following chemotherapy treatment in the clinic (five were mutant for either BRCA1 or BRCA2 (BRCA1/2), four with prior PARPi exposure), recapitulating the population of individuals with aggressive treatment-resistant HGSC in the clinic. Molecular analyses and in vivo treatment studies were undertaken. Seven out of thirteen PRR PDX (54%) were sensitive to treatment with the AMA, eribulin (time to progressive disease (PD) ⩾100 days from the start of treatment) and 11 out of 13 PDX (85%) derived significant benefit from eribulin [time to harvest (TTH) for each PDX with p < 0.002]. In 5 out of 10 platinum-refractory HGSC PDX (50%) and one out of three platinum-resistant PDX (33%), eribulin was more efficacious than was cisplatin, with longer time to PD and significantly extended TTH (each PDX p < 0.02). Furthermore, four of these models were extremely sensitive to all three AMA tested, maintaining response until the end of the experiment (120d post-treatment start). Despite harbouring secondary BRCA2 mutations, two BRCA2-mutant PDX models derived from heavily pre-treated individuals were sensitive to AMA. PRR HGSC PDX models showing greater sensitivity to AMA had high proliferative indices and oncogene expression. Two PDX models, both with prior chemotherapy and/or PARPi exposure, were refractory to all AMA, one of which harboured the SLC25A40-ABCB1 fusion, known to upregulate drug efflux via MDR1. The efficacy observed for eribulin in PRR HGSC PDX was similar to that observed for paclitaxel, which transformed ovarian cancer clinical practice. Eribulin is therefore worthy of further consideration in clinical trials, particularly in ovarian carcinoma with early failure of carboplatin/paclitaxel chemotherapy.

Proteomics of High-Grade Serous Ovarian Cancer Models Identifies Cancer-Associated Fibroblast Markers Associated with Clinical Outcomes.

The tumor microenvironment has recently emerged as a critical component of high-grade serous ovarian cancer (HGSC) disease progression. Specifically, cancer-associated fibroblasts (CAFs) have been recognized as key players in various pro-oncogenic processes. Here, we use mass-spectrometry (MS) to characterize the proteomes of HGSC patient-derived CAFs and compare them to those of the epithelial component of HGSC to gain a deeper understanding into their tumor-promoting phenotype. We integrate our data with primary tissue data to define a proteomic signature of HGSC CAFs and uncover multiple novel CAF proteins that are prognostic in an independent HGSC patient cohort. Our data represent the first MS-based global proteomic characterization of CAFs in HGSC and further highlights the clinical significance of HGSC CAFs.

PAX8 modulates the tumor microenvironment of high grade serous ovarian cancer through changes in the secretome

High grade serous ovarian cancer (HGSC) arises from the fimbriated end of the fallopian tube epithelium (FTE), and in some cases, the ovarian surface epithelium (OSE). PAX8 is a commonly used biomarker for HGSC and is expressed in ∼90% of HGSC. Although the OSE does not express PAX8, murine models of HGSC derived from the OSE acquire PAX8, suggesting that it is not only a marker of Müllerian origin, but also an essential part of cancer progression, potentially from both the OSE and FTE. Previously, we have shown that PAX8 loss in HGSC cells causes tumor cell death and reduces cell migration and invasion. Herein, secretome analysis was performed in PAX8 deleted cells and we identified a reduction of the extracellular matrix (ECM) components, collagen and fibronectin. Immunoblotting and immunofluorescence in PAX8 deleted HGSC cells further validated the results from the secretome analysis. PAX8 loss reduced the amount of secreted TGFbeta, a cytokine that plays a crucial role in remodelling the tumor microenvironment. Furthermore, PAX8 loss reduced the integrity of 3D spheroids and caused a reduction of ECM proteins fibronectin and collagen in 3D cultures. Due to the ubiquitous nature of PAX8 in HGSC, regardless of cell origin, and the association of its reduced expression with decreasing tumor burden, a PAX8 inhibitor could be a promising drug target against various types of HGSC. To accomplish this, we generated a murine oviductal epithelial (MOE) cell line stably expressing PAX8 promoter-luciferase. Using this cell line, we performed a screening assay with a library of FDA-approved drugs (Prestwick Library) and quantitatively assessed these compounds for their inhibition of PAX8. We identified two hits: losartan and captropril, both inhibitors of the renin-angiotensin pathway that inhibit PAX8 expression and function. Overall, this study validates PAX8 as a regulator of ECM deposition in the tumor microenvironment.

Synergistic combination therapy delivered via layer-by-layer nanoparticles induces solid tumor regression of ovarian cancer.

The majority of patients with high grade serous ovarian cancer (HGSOC) develop recurrent disease and chemotherapy resistance. To identify drug combinations that would be effective in treatment of chemotherapy resistant disease, we examined the efficacy of drug combinations that target the three antiapoptotic proteins most commonly expressed in HGSOC-BCL2, BCL-XL, and MCL1. Co-inhibition of BCL2 and BCL-XL (ABT-263) with inhibition of MCL1 (S63845) induces potent synergistic cytotoxicity in multiple HGSOC models. Since this drug combination is predicted to be toxic to patients due to the known clinical morbidities of each drug, we developed layer-by-layer nanoparticles (LbL NPs) that co-encapsulate these inhibitors in order to target HGSOC tumor cells and reduce systemic toxicities. We show that the LbL NPs can be designed to have high association with specific ovarian tumor cell types targeted in these studies, thus enabling a more selective uptake when delivered via intraperitoneal injection. Treatment with these LbL NPs displayed better potency than free drugs in vitro and resulted in near-complete elimination of solid tumor metastases of ovarian cancer xenografts. Thus, these results support the exploration of LbL NPs as a strategy to deliver potent drug combinations to recurrent HGSOC. While these findings are described for co-encapsulation of a BCL2/XL and a MCL1 inhibitor, the modular nature of LbL assembly provides flexibility in the range of therapies that can be incorporated, making LbL NPs an adaptable vehicle for delivery of additional combinations of pathway inhibitors and other oncology drugs.

151 (PB031) - Combination therapy with decitabine and olaparib in poly(ADP-ribose) polymerase inhibitor (PARPi) resistant high grade serous ovarian cancer

Background: Recurrent high grade serous ovarian cancer (HGSOC) is incurable and lethal. Therefore, novel drug combinations are critically needed for this patient population. DNA methyltransferase inhibitors (DNMTi) can cause DNA damage, which activates poly(ADP-ribose) polymerase (PARP) and leads to PARP trapping. Additionally, DNMTi are incorporated into replicating DNA, which causes DNMT-DNA adducts that are then degraded. Therefore, the novel drug combination of DNMTi decitabine and PARP inhibitor (PARPi) olaparib were tested in preclinical HGSOC models.

Gold Nanoparticles Disrupt the IGFBP2/mTOR/PTEN Axis to Inhibit Ovarian Cancer Growth.

By exploiting the self-therapeutic properties of gold nanoparticles (GNPs) a molecular axis that promotes the growth of high-grade serous ovarian cancer (HGSOC), one of the deadliest gynecologic malignancies with poorly understood underlying molecular mechanisms, has been identified. The biodistribution and toxicity of GNPs administered by intravenous or intraperitoneal injection, both as a single dose or by repeated dosing over two weeks are first assessed; no biochemical or histological toxicity to vital organs is found. Using an orthotopic patient-derived xenograft (PDX) model of HGSOC, the authors then show that GNP treatment robustly inhibits tumor growth. Investigating the molecular mechanisms underlying the GNP efficacy reveals that GNPs downregulate insulin growth factor binding protein 2 (IGFBP2) by disrupting its autoregulation via the IGFBP2/mTOR/PTEN axis. This mechanism is validated by treating a cell line-based human xenograft tumor with GNPs and an mTOR dual-kinase inhibitor (PI-103), either individually or in combination with GNPs; GNP and PI-103 combination therapy inhibit ovarian tumor growth similarly to GNPs alone. This report illustrates how the self-therapeutic properties of GNPs can be exploited as a discovery tool to identify a critical signaling axis responsible for poor prognosis in ovarian cancer and provides an opportunity to interrogate the axis to improve patient outcomes.

1697P Drug-induced evolutionary dynamics in BRCA-mutant/non-mutant ovarian cancer models

High-grade serous ovarian cancer (HGSOC) is characterised by extensive intratumoral heterogeneity, which is associated with drug resistance. Our objective is to investigate the clonal dynamics effects of carboplatin (C), paclitaxel (P) and olaparib (O) in in-vivo and in-vitro HGSOC models.

A novel cell line panel reveals non-genetic mediators of platinum resistance and phenotypic diversity in high grade serous ovarian cancer

ObjectivesResistance to cancer therapy is an enduring challenge and accurate and reliable preclinical models are lacking. We interrogated this unmet need using high grade serous ovarian cancer (HGSC) as a disease model. MethodsWe created five in vitro and two in vivo platinum-resistant HGSC models and characterised the entire cell panel via whole genome sequencing, RNASeq and creation of intraperitoneal models. ResultsMutational signature analysis indicated that platinum-resistant cell lines evolved from a pre-existing ancestral clone but a unifying mutational cause for drug resistance was not identified. However, cisplatin-resistant and carboplatin-resistant cells evolved recurrent changes in gene expression that significantly overlapped with independent samples obtained from multiple patients with relapsed HGSC. Gene Ontology Biological Pathways (GOBP) related to the tumour microenvironment, particularly the extracellular matrix, were repeatedly enriched in cisplatin-resistant cells, carboplatin-resistant cells and also in human resistant/refractory samples. The majority of significantly over-represented GOBP however, evolved uniquely in either cisplatin- or carboplatin-resistant cell lines resulting in diverse intraperitoneal behaviours that reflect different clinical manifestations of relapsed human HGSC. ConclusionsOur clinically relevant and usable models reveal a key role for non-genetic factors in the evolution of chemotherapy resistance. Biological pathways relevant to the extracellular matrix were repeatedly expressed by resistant cancer cells in multiple settings. This suggests that recurrent gene expression changes provide a fitness advantage during platinum therapy and also that cancer cell-intrinsic mechanisms influence the tumour microenvironment during the evolution of drug resistance. Candidate genes and pathways identified here could reveal therapeutic opportunities in platinum-resistant HGSC.