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Background Regulatory T cells (Tregs) play an important role in the antitumor immune response in epithelial ovarian cancer (EOC). To understand the immune-inhibitory networks of EOC, we addressed the association between Tregs and immune checkpoint expression on T cells in the tumor microenvironment of EOC. Methods A total of 41 patients with stage IIIC and IV EOC were included in the analysis. We harvested cells from malignant ascites and investigated them using multi-color flow cytometry. We categorized the Tregs into 3 groups: effector-type Tregs, naïve Tregs and non-Tregs, based on the expression patterns of CD45RA and Foxp3 in CD4 + T cells. Furthermore, the relationships between the expression of various immune checkpoint molecules, such as PD-1, on CD8 + T cells and each of the Treg subtypes was also evaluated. Results The median frequency of naïve Tregs, effector-type Tregs and non-Tregs were 0.2% (0–0.8), 2.0% (0–11.4) and 1.5% (0.1–6.3) in CD4 + T cells of malignant ascites from EOC patients, respectively. A high frequency of effector-type Tregs was associated with high-grade serous carcinoma compared with the other histotypes. Patients with higher proportions of effector-type Tregs showed a trend towards increased progression-free survival. We also demonstrated a correlation between a higher proportion of effector-type Tregs and increased PD-1 expression on CD8 + T cells. In addition, C–C chemokine receptor 4 expression was also observed in effector-type Tregs. Conclusion These data suggest that multiple immune-inhibitory networks exist in malignant ascites from EOC patients, suggesting an approach towards combinational immunotherapies for advanced EOC patients.

Malignant abdominal fluid (ascites) frequently develops in women with advanced high-grade serous ovarian cancer (HGSOC) and is associated with drug resistance and a poor prognosis 1 . To comprehensively characterize the HGSOC ascites ecosystem, we used single-cell RNA sequencing to profile ~11,000 cells from 22 ascites specimens from 11 patients with HGSOC. We found significant inter-patient variability in the composition and functional programs of ascites cells, including immunomodulatory fibroblast sub-populations and dichotomous macrophage populations. We found that the previously described immunoreactive and mesenchymal subtypes of HGSOC, which have prognostic implications, reflect the abundance of immune infiltrates and fibroblasts rather than distinct subsets of malignant cells 2 . Malignant cell variability was partly explained by heterogeneous copy number alteration patterns or expression of a stemness program. Malignant cells shared expression of inflammatory programs that were largely recapitulated in single-cell RNA sequencing of ~35,000 cells from additionally collected samples, including three ascites, two primary HGSOC tumors and three patient ascites-derived xenograft models. Inhibition of the JAK/STAT pathway, which was expressed in both malignant cells and cancer-associated fibroblasts, had potent anti-tumor activity in primary short-term cultures and patient-derived xenograft models. Our work contributes to resolving the HSGOC landscape 3 – 5 and provides a resource for the development of novel therapeutic approaches. Single-cell transcriptomics analysis of malignant ascites samples from patients with high-grade serous ovarian cancer reveals inter- and intra-patient heterogeneity in malignant cells, cancer-associated fibroblasts and macrophages.

This two-arm, randomised, multicentre, open-label, phase IIIb study investigated the safety and efficacy of a 3-h catumaxomab infusion with/without prednisolone premedication to reduce catumaxomab-related adverse events. Patients with malignant ascites due to epithelial cancer received four 3-h intraperitoneal catumaxomab infusions with/without intravenous prednisolone (25 mg) premedication before each infusion. The primary safety endpoint was a composite safety score calculated from the incidence and intensity of the most frequent catumaxomab-related adverse events (pyrexia, nausea, vomiting and abdominal pain). Puncture-free survival (PuFS) was a co-primary endpoint. Time to next puncture (TTPu) and overall survival (OS) were secondary endpoints. Prednisolone premedication did not result in a significant reduction in the main catumaxomab-related adverse events. The mean composite safety score was comparable in both arms (catumaxomab plus prednisolone, 4.1; catumaxomab, 3.8; p  = 0.383). Median PuFS (30 vs. 37 days) and TTPu (78 vs. 102 days) were shorter in the catumaxomab plus prednisolone arm than in the catumaxomab arm, but the differences were not statistically significant ( p  = 0.402 and 0.599, respectively). Median OS was longer in the catumaxomab plus prednisolone arm than in the catumaxomab arm (124 vs. 86 days), but the difference was not statistically significant ( p  = 0.186). The superiority of catumaxomab plus prednisolone versus catumaxomab alone could not be proven for the primary endpoint. Prednisolone did not result in a significant reduction in the main catumaxomab-related adverse events. The study confirms the safety and efficacy of catumaxomab administered as four 3-h intraperitoneal infusions for the treatment of malignant ascites.

The build-up of fluid in the peritoneal cavity—ascites—is a hallmark of ovarian cancer, the most lethal of all gynaecological malignancies. This remarkable fluid, which contains a variety of cellular and acellular components, is known to contribute to patient morbidity and mortality by facilitating metastasis and contributing to chemoresistance, but remains largely under-researched. In this review, we will critically analyse the evidence associating ascites with metastasis and chemoresistance in ovarian cancer and provide an update on research in the field. We will argue the case for ascites as a unique and accessible substrate for tracking tumour progression and for translational research that will enhance our understanding of this cancer and lead to improvements in patient outcomes.

Advanced ovarian cancers are highly metastatic due to frequent peritoneal dissemination, resulting in dismal prognosis. Here we report the functions of cancer-derived extracellular vesicles (EVs), which are emerging as important mediators of tumour metastasis. The EVs from highly metastatic cells strongly induce metastatic behaviour in moderately metastatic tumours. Notably, the cancer EVs efficiently induce apoptotic cell death in human mesothelial cells in vitro and in vivo , thus resulting in the destruction of the peritoneal mesothelium barrier. Whole transcriptome analysis shows that MMP1 is significantly elevated in mesothelial cells treated with highly metastatic cancer EVs and intact MMP1 mRNAs are selectively packaged in the EVs. Importantly, MMP1 expression in ovarian cancer is tightly correlated with a poor prognosis. Moreover, MMP1 mRNA-carrying EVs exist in the ascites of cancer patients and these EVs also induce apoptosis in mesothelial cells. Our findings elucidate a previously unknown mechanism of peritoneal dissemination via EVs. Ovarian cancer is particularly deadly because it is difficult to detect at the pre-metastatic stage; extracellular vesicles (EVs) on the other hand are involved in the pre-metastatic niche preparation. Here the authors show that EVs mediate ovarian cancer metastasis in the peritoneal area by targeting the mesothelium.

Background: Effective, non-invasive, palliative strategies for symptomatic malignant ascites are unavailable. This trial explored whether octreotide, an inhibitor of vascular endothelial growth factor, a putative mediator of ascites, prolongs the interval to next paracentesis. Methods: After a baseline paracentesis and a test of short-acting agent, patients with symptomatic ascites were randomly assigned to long-acting octreotide (Sandostatin LAR®) depot 30 mg intramuscularly every month versus 0.9% sodium chloride administered similarly. Patients were then monitored for recurrent, symptomatic ascites. Results: Thirty-three patients were enrolled: 16 assigned to the octreotide and 17 to the control arm. The median time to next paracentesis was 28 and 14 days in the octreotide and placebo arm, respectively (p = 0.17). After adjustment for extracted ascites volume and abdominal girth change, no statistically significant difference between the groups was observed (hazard ratio = 0.52, with a 95% confidence interval of 0.21–1.28; p = 0.15, per Cox model). Octreotide-treated patients described less of abdominal bloating (p = 0.01), abdominal discomfort (p = 0.02), and shortness of breath (p = 0.007) at one month, although other quality of life symptoms were comparable between the arms. Long-acting octreotide was reasonably well tolerated. Conclusion: As prescribed in this trial, octreotide did not seem effective in prolonging the time to next paracentesis, although improvements in symptoms suggest that vascular endothelial growth factor inhibition merits further investigation.

Purpose This study was designed to evaluate efficacy, toxicity, and adverse effects of combination of chemotherapy drugs and intraperitoneal perfusion of verapamil in the treatment of malignant ascites. Methods Seventy-two patients with malignant ascites were divided into two study groups. Patients in control group (31 cases) received conventional chemotherapy, whereas patients in the combined treatment group (41 cases) were given verapamil intraperitoneally in addition to chemotherapy drugs. Thirty days after the treatment, efficacy, toxicity, and adverse effects were assessed in both study groups. Results The treatment of control group led to 1 case of complete remission and 2 cases of partial remission, making the rate of efficacy (complete + partial remission) of 9.7 %. The combined treatment group demonstrated 13 cases of complete remission and 22 cases of partial remission. Thus, the rate of efficacy was significantly higher in the combined treatment group (85.36 %; p  < 0.05 vs. control group). Using KPS scores, changes in quality of life were compared before and after the treatment. The quality of life improved in control group by 13.7 %, while combined treatment group showed improvement of 83.5 % ( p  < 0.05 vs. control group). Further, cumulative survival rate was also significantly higher in the combined treatment group. Treatment toxicity and the rate of adverse effects and intestinal adhesion were not significantly different between study groups. Conclusions Intraperitoneal perfusion of verapamil enhances the efficacy of chemotherapy drugs, prolongs survival, and improves the quality of life. Intraperitoneal administration limits cardiotoxicity of verapamil.

Immunosuppressive tumor microenvironment (TME) and ascites-derived spheroids in ovarian cancer (OC) facilitate tumor growth and progression, and also pose major obstacles for cancer therapy. The molecular pathways involved in the OC-TME interactions, how the crosstalk impinges on OC aggression and chemoresistance are not well-characterized. Here, we demonstrate that tumor-derived UBR5, an E3 ligase overexpressed in human OC associated with poor prognosis, is essential for OC progression principally by promoting tumor-associated macrophage recruitment and activation via key chemokines and cytokines. UBR5 is also required to sustain cell-intrinsic β-catenin-mediated signaling to promote cellular adhesion/colonization and organoid formation by controlling the p53 protein level. OC-specific targeting of UBR5 strongly augments the survival benefit of conventional chemotherapy and immunotherapies. This work provides mechanistic insights into the novel oncogene-like functions of UBR5 in regulating the OC-TME crosstalk and suggests that UBR5 is a potential therapeutic target in OC treatment for modulating the TME and cancer stemness. Ovarian cancer cells often metastasize to the peritoneal cavity, forming spheroid-like structures and promoting a highly immunosuppressive tumor microenvironment. Here, the authors show that the ubiquitin ligase UBR5 is required for ovarian cancer growth and metastasis, sustaining spheroid formation and the infiltration of immunosuppressive tumor associated macrophages.

In ovarian cancer patients, tumor fibrosis and angiotensin-driven fibrogenic signaling have been shown to inversely correlate with survival. We sought to enhance drug delivery and therapeutic efficacy by remodeling the dense extracellular matrix in two orthotopic human ovarian carcinoma xenograft models. We hypothesized that targeting the angiotensin signaling axis with losartan, an approved angiotensin system inhibitor, could reduce extracellular matrix content and the associated “solid stress,” leading to better anticancer therapeutic effect. We report here four translatable findings: (i) losartan treatment enhances the efficacy of paclitaxel—a drug used for ovarian cancer treatment—via normalizing the tumor microenvironment, resulting in improved vessel perfusion and drug delivery; (ii) losartan depletes matrix via inducing antifibrotic miRNAs that should be tested as candidate biomarkers of response or resistance to chemotherapy; (iii) although losartan therapy alone does not reduce tumor burden, it reduces both the incidence and the amount of ascites formed; and (iv) our retrospective analysis revealed that patients receiving angiotensin system inhibitors concurrently with standard treatment for ovarian cancer exhibited 30 mo longer overall survival compared with patients on other antihypertensives. Our findings provide the rationale and supporting data for a clinical trial on combined losartan and chemotherapy in ovarian cancer patients.

Tumor-driven immune suppression is a major barrier to successful immunotherapy in ovarian carcinomas (OvCa). Among various mechanisms responsible for immune suppression, arginase-1 (ARG1)-carrying small extracellular vesicles (EVs) emerge as important contributors to tumor growth and tumor escape from the host immune system. Here, we report that small EVs found in the ascites and plasma of OvCa patients contain ARG1. EVs suppress proliferation of CD4 + and CD8 + T-cells in vitro and in vivo in OvCa mouse models. In mice, ARG1-containing EVs are transported to draining lymph nodes, taken up by dendritic cells and inhibit antigen-specific T-cell proliferation. Increased expression of ARG1 in mouse OvCa cells is associated with accelerated tumor progression that can be blocked by an arginase inhibitor. Altogether, our studies show that tumor cells use EVs as vehicles to carry over long distances and deliver to immune cells a metabolic checkpoint molecule – ARG1, mitigating anti-tumor immune responses. Cancer cells employ a variety of ways to escape the immune system. Here, the authors show that ovarian cancer cells produce small extracellular vescicles containing arginase 1 that are taken up by dendritic cells in the draining lymph nodes, resulting in inhibition of antigen-specific T-cell proliferation.