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Immune checkpoint inhibitors have demonstrated limited efficacy in overcoming immunosuppression in patients with epithelial ovarian cancer (EOC). Although certain patients experience long‐term treatment benefit, reliable biomarkers for responder pre‐selection and the distinction of dominant immunosuppressive mechanisms have yet to be identified. Here, we used a 40‐marker suspension mass cytometry panel to comprehensively phenotype peripheral blood leukocytes sampled over time from patients with relapsed EOC who underwent combination oleclumab (anti‐CD73) and durvalumab (anti‐PD‐L1) immunotherapy in the NSGO‐OV‐UMB1/ENGOT‐OV30 trial. We found that survival duration was impacted by baseline abundances of total peripheral blood mononuclear cells. Longitudinal analyses revealed a significant increase in CD14+CD16− myeloid cells during treatment, with significant expansion of monocytic myeloid‐derived suppressor cells occurring in patients with shorter progression‐free survival, who additionally showed a continuous decrease in central memory T‐cell abundances. All patients demonstrated significant PD‐L1 upregulation over time on most T‐cell subsets. Higher CD73 and IDO1 expression on certain leukocytes at baseline significantly positively correlated with longer progression‐free survival. Overall, our study proposes potential biomarkers for EOC immunotherapy personalization and response monitoring; however, further validation in larger studies is needed. Using mass cytometry, we analyzed serial blood samples from patients with relapsed epithelial ovarian cancer (EOC) treated with oleclumab–durvalumab combination immunotherapy in the NSGO‐OV‐UMB1/ENGOT‐OV30 trial. Our analysis identified potential predictive, monitoring, and response biomarkers detectable through liquid biopsy. These findings facilitate the advancement of strategies for patient pre‐selection and treatment personalization to address the limited efficacy of immunotherapy in EOC.

Despite advances in surgical and therapeutic approaches, high-grade serous ovarian carcinoma (HGSOC) prognosis remains poor. Surgery is an indispensable component of therapeutic protocols, as removal of all visible tumor lesions (cytoreduction) profoundly improves the overall survival. Enhanced predictive tools for assessing cytoreduction are essential to optimize therapeutic precision. Patients’ immune status broadly reflects the tumor cell biological behavior and the patient responses to disease and treatment. Serum cytokine profiling is a sensitive measure of immune adaption and deviation, yet its integration into treatment paradigms is underexplored. This study is part of the IMPACT trial (NCT03378297) and aimed to characterize immune responses before and during primary treatment for HGSOC to identify biomarkers for treatment selection and prognosis. Longitudinal serum samples from 22 patients were collected from diagnosis until response evaluation. Patients underwent primary cytoreductive surgery or neoadjuvant chemotherapy (NACT) based on laparoscopy scoring. Twenty-seven serum cytokines analyzed by Bio-Plex 200, revealed two immune phenotypes at diagnosis: Immune High with marked higher serum cytokine levels than Immune Low. The immune phenotypes reflected the laparoscopy scoring and allocation to surgical treatment. The five Immune High patients undergoing primary cytoreductive surgery exhibited immune mobilization and extended progression-free survival, compared to the Immune Low patients undergoing the same treatment. Both laparoscopy and cytoreductive surgery induced substantial and transient changes in serum cytokines, with upregulation of the inflammatory cytokine IL-6 and downregulation of the multifunctional cytokines IP-10, Eotaxin, IL-4, and IL-7. Over the study period, cytokine levels uniformly decreased in all patients, leading to the elimination of the initial immune phenotypes regardless of treatment choice. This study reveals distinct pre-treatment immune phenotypes in HGSOC patients that might be informative for treatment stratification and prognosis. This potential novel biomarker holds promise as a foundation for improved assessment of treatment responses in patients with HGSOC. ClinicalTrials.gov Identifier: NCT03378297.

Complete cytoreductive surgery is the cornerstone of the treatment of epithelial ovarian cancer (EOC). The application of fluorescence image-guided surgery (FIGS) allows for the increased intraoperative visualization and delineation of malignant lesions by using fluorescently labeled targeting biomarkers, thereby improving intraoperative guidance. CD24, a small glycophosphatidylinositol-anchored cell surface receptor, is overexpressed in approximately 70% of solid cancers, and has been proposed as a prognostic and therapeutic tumor-specific biomarker for EOC. Recently, preclinical studies have demonstrated the benefit of CD24-targeted contrast agents for non-invasive fluorescence imaging, as well as improved tumor resection by employing CD24-targeted FIGS in orthotopic patient-derived xenograft models of EOC. The successful detection of miniscule metastases denotes CD24 as a promising biomarker for the application of fluorescence-guided surgery in EOC patients. The aim of this review is to present the clinical and preclinically evaluated biomarkers for ovarian cancer FIGS, highlight the strengths of CD24, and propose a future bimodal approach combining CD24-targeted fluorescence imaging with radionuclide detection and targeted therapy.

The identification and removal of all gross and microscopic tumor to render the patient disease free represents a huge challenge in ovarian cancer treatment. The presence of residual disease is an independent negative prognostic factor. Herein, we describe the synthesis and the “in vitro” evaluation of compounds as cyclooxygenase (COX)-1 inhibitors, the COX-1 isoform being an ovarian cancer biomarker, each bearing fluorochromes with different fluorescence features. Two of these compounds N-[4-(9-dimethylimino-9H-benzo[a]phenoxazin-5-ylamino) butyl]-2-(3,4-bis(4-methoxyphenyl)isoxazol-5-yl)acetamide chloride (RR11) and 3-(6-(4-(2-(3,4-bis(4-methoxyphenyl)isoxazole-5-yl)acetamido)butyl)amino-6-oxohexyl)-2-[7-(1,3-dihydro-1,1-dimethyl-3-ethyl 2H-benz[e]indolin-2-yl-idene)-1,3,5-heptatrienyl]-1,1-dimethyl-3-(6-carboxilato-hexyl)-1H-benz[e]indolium chloride, 23 (MSA14) were found to be potent and selective inhibitors of cyclooxygenase (COX)-1 “in vitro”, and thus were further investigated “in vivo”. The IC50 values were 0.032 and 0.087 µM for RR11 and 23 (MSA 14), respectively, whereas the COX-2 IC50 for RR11 is 2.4 µM while 23 (MSA14) did not inhibit COX-2 even at a 50 µM concentration. Together, this represented selectivity index = 75 and 874, respectively. Structure-based virtual screening (SBVS) performed with the Fingerprints for Ligands and Proteins (FLAP) software allowed both to differentiate highly active compounds from less active and inactive structures and to define their interactions inside the substrate-binding cavity of hCOX1. Fluorescent probes RR11 and 23 (MSA14), were used for preliminary near-infrared (NIR) fluorescent imaging (FLI) in human ovarian cancer (OVCAR-3 and SKOV-3) xenograft models. Surprisingly, a tumor-specific signal was observed for both tested fluorescent probes, even though this signal is not linked to the presence of COX-1.

BackgroundOvarian cancer (OC) is a heterogeneous disease, often diagnosed at an advanced stage. After an initial encouraging response rate to first-line treatment, comprising cytoreductive surgery combined with platinum-based chemotherapy, most of such cancers recur. The use of advanced, clinically relevant mouse models allows us to study tumor pathogenesis and to evaluate response to new cancer drugs, which may ultimately prevent recurrence and prolong survival. Most preclinical models however do not fully recapitulate the tumor microenvironment as well as heterogeneity, and thus many drugs fail a successful implementation into clinical practice. We developed and characterized humanized patient-derived xenograft (PDX) murine models, comprising of a functional human immune system and an orthotopically implanted primary ovarian cancer tumor. These models were further used to test treatment response of immune checkpoint inhibitor PD-1, combinatorial immunotherapy targeting PD-L1 and CD73, and novel chimeric antigen receptor (CAR) constructs targeting unique biomarker of OC.MethodsHumanized PDX mice were generated by co-transplantation of CD34+ hematopoietic cells, isolated from the umbilical cord blood and primary ovarian cancer cell suspensions from treatment naïve OC patients. PDX models were characterized by whole exome sequencing (WES) and the developing human immune system in immunodeficient mice was followed longitudinally by flow cytometry. Bioluminescence and 18F-FDG PET-CT imaging of tumor burden, survival analysis, and characterization of tumor-infiltrating immune cells by a 34-surface mass cytometry were performed to assess the treatment responses.ResultsPhenotypic and genomic characterization of humanized PDX models was achieved. Mice treated with nivolumab showed a decrease in tumor burden, however no significant survival benefit when compared to untreated controls was identified, nor could a correlation between PD-L1 expression, CD8 T cell infiltration and response parameters been observed. Interestingly, the characterization of immune infiltrating cells identified predominantly myeloid cells as seen in ovarian cancer patients. In a CAR T cell treatment study of OC PDX mice, bioluminescence imaging showed a delayed onset of metastasis and smaller tumor burden, but also severe toxic side effects in CAR T cell treated PDX mice compared to untreated control mice. Results from combinatorial immunotherapy targeting PD-L1 and CD73 are awaited.ConclusionsHumanized orthotopic OC PDX models have been established. Together with the promising advances in new immunotherapeutic targets, clinically relevant mouse models facilitate the development of new immunotherapies targeting the ovarian tumor microenvironment.Ethics ApprovalPatient tumor samples were provided by the Gynecologic Cancer Biobank, Women’s Clinic, Haukeland University Hospital, Bergen, Norway (REK ID: 2014/1907, 2015/548, 2018/72). Animal experiments are performed in accordance with the procedures set by the Norwegian State Commission for Laboratory Animals, and the laboratory-animal experiments (FOTS 25412) have been approved by the Norwegian Food Safety Authority.ConsentWritten informed consent was obtained from all women before collection of fresh tumor tissues. A copy of the written consent and approval is available for review.

BackgroundOvarian cancer (OC) is the leading cause of death from gynecologic malignancies in the Western world. Contributing factors include a high frequency of late-stage diagnosis, the development of chemoresistance, and the evasion of host immune responses. Currently, debulking surgery and platinum-based chemotherapy are the treatment cornerstones, although recurrence is common. As the clinical efficacy of immune checkpoint blockade is low, new immunotherapeutic strategies are needed. Chimeric antigen receptor (CAR) T cell therapy empowers patients’ own T cells to fight and eradicate cancer, and has been tested against various targets in OC. A promising candidate is the MUC16 ectodomain. This ectodomain remains on the cell surface after cleavage of cancer antigen 125 (CA125), the domain distal from the membrane, which is currently used as a serum biomarker for OC. CA125 itself has not been tested as a possible CAR target. In this study, we examined the suitability of the CA125 as a target for CAR T cell therapy.MethodsWe tested a series of antibodies raised against the CA125 extracellular repeat domain of MUC16 and adapted them to the CAR format. Comparisons between these candidates, and against an existing CAR targeting the MUC16 ectodomain, identified K101 as having high potency and specificity. The K101CAR was subjected to further biochemical and functional tests, including examination of the effect of soluble CA125 on its activity. Finally, we used cell lines and advanced orthotopic patient-derived xenograft (PDX) models to validate, in vivo, the efficiency of our K101CAR construct.ResultsWe observed a high efficacy of K101CAR T cells against cell lines and patient-derived tumors, in vitro and in vivo. We also demonstrated that K101CAR functionality was not impaired by the soluble antigen. Finally, in direct comparisons, K101CAR, which targets the CA125 extracellular repeat domains, was shown to have similar efficacy to the previously validated 4H11CAR, which targets the MUC16 ectodomain.ConclusionsOur in vitro and in vivo results, including PDX studies, demonstrate that the CA125 domain of MUC16 represents an excellent target for treating MUC16-positive malignancies.

High-grade serous ovarian carcinoma is an aggressive and heterogeneous disease with a poor prognosis, and it is often diagnosed at an advanced stage. Genetic information on DNA repair is increasingly used in diagnosis, risk assessment, and treatment selection and will ostensibly translate to an overall survival benefit—at least for certain subgroups of patients. In this commentary, we outline the promise and challenges of precision oncology and discuss how the prospects depend not only on genomic data but also on deep-tissue immune profiling. The technological breakthroughs in antibody-based therapies have paved the way for the introduction of new therapeutics.

Immune checkpoint inhibitors have demonstrated limited efficacy in overcoming immunosuppression in patients with epithelial ovarian cancer (EOC). Although certain patients experience long‐term treatment benefit, reliable biomarkers for responder pre‐selection and the distinction of dominant immunosuppressive mechanisms have yet to be identified. Here, we used a 40‐marker suspension mass cytometry panel to comprehensively phenotype peripheral blood leukocytes sampled over time from patients with relapsed EOC who underwent combination oleclumab (anti‐CD73) and durvalumab (anti‐PD‐L1) immunotherapy in the NSGO‐OV‐UMB1/ENGOT‐OV30 trial. We found that survival duration was impacted by baseline abundances of total peripheral blood mononuclear cells. Longitudinal analyses revealed a significant increase in CD14 + CD16 − myeloid cells during treatment, with significant expansion of monocytic myeloid‐derived suppressor cells occurring in patients with shorter progression‐free survival, who additionally showed a continuous decrease in central memory T‐cell abundances. All patients demonstrated significant PD‐L1 upregulation over time on most T‐cell subsets. Higher CD73 and IDO1 expression on certain leukocytes at baseline significantly positively correlated with longer progression‐free survival. Overall, our study proposes potential biomarkers for EOC immunotherapy personalization and response monitoring; however, further validation in larger studies is needed.

The prognosis of high-grade serous ovarian carcinoma (HGSOC) is poor, and treatment selection is challenging. A heterogeneous tumor microenvironment (TME) characterizes HGSOC and influences tumor growth, progression, and therapy response. Better characterization with multidimensional approaches for simultaneous identification and categorization of the various cell populations is needed to map the TME complexity. While mass cytometry allows the simultaneous detection of around 40 proteins, the CyTOFmerge MATLAB algorithm integrates data sets and extends the phenotyping. This pilot study explored the potential of combining two datasets for improved TME phenotyping by profiling single-cell suspensions from ten chemo-naïve HGSOC tumors by mass cytometry. A 35-marker pan-tumor dataset and a 34-marker pan-immune dataset were analyzed separately and combined with the CyTOFmerge, merging 18 shared markers. While the merged analysis confirmed heterogeneity across patients, it also identified a main tumor cell subset, additionally to the nine identified by the pan-tumor panel. Furthermore, the expression of traditional immune cell markers on tumor and stromal cells was revealed, as were marker combinations that have rarely been examined on individual cells. This study demonstrates the potential of merging mass cytometry data to generate new hypotheses on tumor biology and predictive biomarker research in HGSOC that could improve treatment effectiveness.

High-grade serous ovarian cancer (HGSOC) has poor prognosis and new treatment modalities are needed. Immunotherapy, with checkpoint inhibitors, have demonstrated limited impact. To evaluate the suitability for immunotherapeutics, contextualized preclinical models are required to secure meaningful clinical translation. Therefore, we developed and characterized humanized patient-derived xenograft (hu PDX) murine models of HGSOC, which were established by orthotopic implantation of tumor cell suspensions and intravenous injection of CD34+ cells isolated from umbilical cord blood samples. The developing human immune system in NSG and NSGS mice was followed longitudinally by flow cytometry and characterized by mass cytometry with a panel of 34 surface markers. Molecular imaging of tumor burden, survival analysis, and characterization of tumor-infiltrating immune cells was performed to assess the treatment response to anti-PD-1 (nivolumab) monotherapy. Successful generation of hu PDX models was achieved. Mice treated with nivolumab showed a decrease in tumor burden, however no significant survival benefit was identified when compared to untreated controls. No correlation was seen between PD-L1 expression and CD8 T cell infiltration and response parameters. As the characterization showed an immune infiltration of predominantly myeloid cells, similar to what is observed in HGSOC patients, the models may have the potential to evaluate the importance of myeloid cell immunomodulation as well.