Ovarian cancer has one of the poorest prognoses among carcinomas. Advanced ovarian cancer often develops ascites and peritoneal dissemination, which is one of the poor prognostic factors. From the perspective of the “seed and soil” hypothesis, the intra-abdominal environment is like the soil for the growth of ovarian cancer (OvCa) and mesothelial cells (MCs) line the top layer of this soil. In recent years, various functions of MCs have been reported, including supporting cancer in the OvCa microenvironment. We refer to OvCa-associated MCs (OCAMs) as MCs that are stimulated by OvCa and contribute to its progression. OCAMs promote OvCa cell adhesion to the peritoneum, invasion, and metastasis. Elucidation of these functions may lead to the identification of novel therapeutic targets that can delay OvCa progression, which is difficult to cure.

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Adipocyte-rich omentum offers "good soil" for disseminating ovarian cancer (OvCa), contributing to therapeutic difficulty. However, little is understood about the association between adipocytes and tumor growth at peritoneal dissemination site. Herein, we report the induction of adipocyte dedifferentiation by OvCa cells and protumorigenic effects of resulted adipocyte-derived fibroblasts. We confirmed that malignant ascites promoted the dedifferentiation of the primary human adipocytes obtained from surgical omental specimen into omental adipocyte-derived fibroblast (O-ADF) that possess both mesenchymal stem cell and myofibroblast-like features. This promotion of dedifferentiation by malignant ascites was blocked by addition of Wnt signaling inhibitor. The effects of dedifferentiated adipocytes in proliferation and migration of OvCa cells were analyzed with in vitro coculturing experimental models and in vivo mice model, and we demonstrated that OvCa cell lines showed enhanced proliferative characteristics, as well as increased migratory abilities upon coculturing with O-ADF. Additionally, exogenous transforming growth factor-β1 augmented desmoplastic morphological change of O-ADF, leading to higher proliferative ability. Our results suggest that OvCa cells promote dedifferentiation of peritoneal adipocytes by activating Wnt/β-catenin signaling, and generated O-ADFs exhibit pro-tumoral hallmarks.

Epithelial ovarian cancer (EOC) is the most lethal gynecologic malignancy and has a unique metastatic route using ascites, known as the transcoelomic root. However, studies on ascites and contained cellular components have not yet been sufficiently clarified. In this review, we focus on the significance of accumulating ascites, contained EOC cells in the form of spheroids, and interaction with non-malignant host cells. To become resistant against anoikis, EOC cells form spheroids in ascites, where epithelial-to-mesenchymal transition stimulated by transforming growth factor-β can be a key pathway. As spheroids form, EOC cells are also gaining the ability to attach and invade the peritoneum to induce intraperitoneal metastasis, as well as resistance to conventional chemotherapy. Recently, accumulating evidence suggests that EOC spheroids in ascites are composed of not only cancer cells, but also non-malignant cells existing with higher abundance than EOC cells in ascites, including macrophages, mesothelial cells, and lymphocytes. Moreover, hetero-cellular spheroids are demonstrated to form more aggregated spheroids and have higher adhesion ability for the mesothelial layer. To improve the poor prognosis, we need to elucidate the mechanisms of spheroid formation and interactions with non-malignant cells in ascites that are a unique tumor microenvironment for EOC.

Most patients with ovarian cancer experience recurrence and develop resistance to platinum-based agents. The diagnosis of platinum resistance based on the platinum-free interval is not always accurate and timely in clinical settings. Herein, we used laser ablation inductively coupled plasma mass spectrometry to visualize the platinum distribution in the ovarian cancer tissues at the time of interval debulking surgery after neoadjuvant chemotherapy in 27patients with advanced high-grade serous ovarian cancer. Two distinct patterns of platinum distribution were observed. Type A (n = 16): platinum accumulation at the adjacent stroma but little in the tumor; type B (n = 11): even distribution of platinum throughout the tumor and adjacent stroma. The type A patients treated post-surgery with platinum-based adjuvant chemotherapy showed significantly shorter periods of recurrence after the last platinum-based chemotherapy session (p = 0.020) and were diagnosed with “platinum-resistant recurrence”. Moreover, type A was significantly correlated with worse prognosis (p = 0.031). Post-surgery treatment with non-platinum-based chemotherapy could be effective for the patients classified as type A. Our findings indicate that the platinum resistance can be predicted prior to recurrence, based on the platinum distribution; this could contribute to the selection of more appropriate adjuvant chemotherapy, which may lead to improves prognoses.

Ovarian cancer (OvCa) is one of the leading causes of death due to its high metastasis rate to the peritoneum. Recurrent peritoneal tumors also develop despite the use of conventional platinum-based chemotherapies. Therefore, it is still important to explore the factors associated with peritoneal metastasis, as these predict the prognosis of patients with OvCa. In this study, we investigated the function of microphthalmia-associated transcription factor (MITF), which contributes to the development of melanoma, in epithelial ovarian cancer (OvCa). High MITF expression was significantly associated with a poor prognosis in OvCa. Notably, MITF contributed to the motility and invasion of OvCa cells, and specifically with their peri-mesothelial migration. In addition, MITF-positive cells expressed the melanoma cell adhesion molecule (MCAM/CD146), which was initially identified as a marker of melanoma progression and metastasis, and MCAM expression was regulated by MITF. MCAM was also identified as a significant prognostic factor for poor progression-free survival in patients with OvCa. Collectively, our results suggest that MITF is a novel therapeutic target that potentially promotes peritoneal metastasis of OvCa.

Objective The aim of the present study was to examine the effects of incomplete surgery and adjuvant chemotherapy on the prognosis of patients with intraoperative rupture of capsulated stage I epithelial ovarian cancer (OvCa). Methods A regional retrospective study was conducted between 1986 and 2019. Among 4,730 patients with malignant ovarian tumors, 534 women with International Federation of Gynecology and Obstetrics stage IA and IC1 epithelial OvCa were eligible. Differences in survival outcomes were examined between patients with stage IA and IC1 tumors and the effects of uterine preservation, complete-staging lymphadenectomy, and adjuvant chemotherapy were investigated by an in-depth subgroup analysis. To analyze therapeutic effects, baseline imbalances were adjusted using propensity score (PS). Results The prognosis of patients with stage IC1 tumors was worse than those with stage IA. Surgical spill did not affect the site of recurrence. In the PS-adjusted subgroup analysis, uterine preservation (hazard ratio [HR]=1.669; 95% confidence interval [CI]=1.052–2.744), incomplete-staging lymphadenectomy (HR=1.689; 95% CI=1.211–2.355), and the omission of adjuvant chemotherapy (HR=3.729; 95% CI=2.090–6.653) significantly increased the HR of recurrence for patients with stage IC1 tumors compared to those with stage IA tumors. Adjuvant chemotherapy decreased the impact of rupture with uterine preservation (HR=0.159; 95% CI=0.230–1.168) or incomplete-staging lymphadenectomy (HR=0.987; 95% CI=0.638–1.527). Conclusion The present results suggest intraoperative rupture of capsulated stage I epithelial OvCa is associated with a poor prognosis. When chemotherapy is given for patients receiving incomplete surgery, there is no longer an increased risk of recurrence observed with the rupture.

Positive ascites cytology is a strong prognostic factor in patients with early-stage ovarian cancer (OvCa). However, limited information is currently available on the impact of positive ascites cytology on patient prognoses under each clinical background. We herein investigated the comprehensive impact of positive ascites cytology on patients with epithelial OvCa and the effectiveness of additional therapeutic interventions, including complete staging surgery and chemotherapy. Among 4730 patients with malignant ovarian neoplasms, retrospectively identified in multiple institutions, 1906 with epithelial OvCa were included. In the investigation of its effects on clinical factors using a multivariate analysis, positive ascites cytology correlated with a poor prognosis. Positive ascites cytology had a significantly worse prognosis than those with negative cytology in all subgroups except for patients with stage IV tumors and a mucinous histology. Chemotherapy may be effective in reducing the negative impact of positive ascites cytology on the prognosis of patients in terms of progression-free and overall survivals, while complete staging surgery did not improve the prognosis of patients with positive ascites cytology. Collectively, our findings suggested that positive ascites cytology had a negative impact on the prognosis of patients with epithelial OvCa, but not those with stage IV tumors or a mucinous histology.