Mesothelial-to-mesenchymal transition as a possible therapeutic target in peritoneal metastasis of ovarian cancer.

Peritoneal dissemination is the primary metastatic route of ovarian cancer (OvCa), and is often accompanied by the accumulation of ascitic fluid. The peritoneal cavity is lined by mesothelial cells (MCs), which can be converted into carcinoma-associated fibroblasts (CAFs) through mesothelial-to-mesenchymal transition (MMT). Here, we demonstrate that MCs isolated from ascitic fluid (AFMCs) of OvCa patients with peritoneal implants also undergo MMT and promote subcutaneous tumour growth in mice. RNA sequencing of AFMCs revealed that MMT-related pathways - including transforming growth factor (TGF)-ß signalling - are differentially regulated, and a gene signature was verified in peritoneal implants from OvCa patients. In a mouse model, pre-induction of MMT resulted in increased peritoneal tumour growth, whereas interfering with the TGF-ß receptor reduced metastasis. MC-derived CAFs showed activation of Smad-dependent TGF-ß signalling, which was disrupted in OvCa cells, despite their elevated TGF-ß production. Accordingly, targeting Smad-dependent signalling in the peritoneal pre-metastatic niche in mice reduced tumour colonization, suggesting that Smad-dependent MMT could be crucial in peritoneal carcinomatosis. Together, these results indicate that bidirectional communication between OvCa cells and MC-derived CAFs, via TGF-ß-mediated MMT, seems to be crucial to form a suitable metastatic niche. We suggest MMT as a possible target for therapeutic intervention and a potential source of biomarkers for improving OvCa diagnosis and/or prognosis. © 2017 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Bevacizumab plus irinotecan in recurrent malignant glioma shows high overall survival in a multicenter retrospective pooled series of the Spanish Neuro-Oncology Research Group (GEINO).

There is no 'standard of care' for recurrent malignant glioma (MG). Our aim is to confirm the efficacy and safety of bevacizumab 10 mg/kg plus irinotecan 125 mg/m² (or 340 mg/m² if enzyme-inducing antiepileptic drugs) every 2 weeks for a maximum of 1 year in a retrospective pooled series of patients with recurrent MG. The inclusion criteria were as follows: age 18 years and above, histology of MG, progression after radiation and temozolomide, Karnofsky performance status (KPS) of at least 60, and signed informed consent for bevacizumab compassionate use. Response was assessed by MRI using the Macdonald criteria and evaluation of the FLAIR sequence every 8 weeks. A total of 130 patients were enrolled; 72% had glioblastoma (GBM). The median age of the patients was 53 years (20-78); the median KPS was 80%; the median number of prior chemotherapy lines was 2 (1-5); the median interval between the diagnosis of MG and inclusion was 14.6 months (2-166); and the median number of bevacizumab infusions was 8 (1-39). The median follow-up duration was 7.2 months (1-47). The median overall survival (OS) was 8.8 months for GBM and 11.2 months for anaplastic glioma (AG). The median progression-free survival was 5.1 months for GBM and 4.6 months for AG. The response rate was 56% for GBM and 68% for AG. Neurological and KPS improvements were observed in 49 and 45% of patients. Only KPS less than 80% was associated with a worse significant response rate (odds ratio, 0.57; 95% confidence interval, 0.22-0.96). The most frequent grades 3-4 toxicities were asthenia (7%), diarrhea (6%), and thromboembolic events (5%). There were five toxic deaths (4%). Bevacizumab plus irinotecan in recurrent MG improves responses, progression-free survival, and OS compared with historical data. KPS of at least 80% was a predictive factor for response and OS.

The Mesothelial Origin of Carcinoma Associated-Fibroblasts in Peritoneal Metastasis.

Solid tumors are complex and unstructured organs that, in addition to cancer cells, also contain other cell types. Carcinoma-associated fibroblasts (CAFs) represent an important population in the tumor microenviroment and participate in several stages of tumor progression, including cancer cell migration/invasion and metastasis. During peritoneal metastasis, cancer cells detach from the primary tumor, such as ovarian or gastrointestinal, disseminate through the peritoneal fluid and colonize the peritoneum. Tumor cells metastasize by attaching to and invading through the mesothelial cell (MC) monolayer that lines the peritoneal cavity, then colonizing the submesothelial compact zone where CAFs accumulate. CAFs may derive from different sources depending on the surrounding metastatic niche. In peritoneal metastasis, a sizeable subpopulation of CAFs originates from MCs through a mesothelial-to-mesenchymal transition (MMT), which promotes adhesion, invasion, vascularization and subsequent tumor growth. The bidirectional communication between cancer cells and MC-derived CAFs via secretion of a wide range of cytokines, growth factors and extracellular matrix components seems to be crucial for the establishment and progression of the metastasis in the peritoneum. This manuscript provides a comprehensive review of novel advances in understanding how peritoneal CAFs provide cancer cells with a supportive microenvironment, as well as the development of future therapeutic approaches by interfering with the MMT in the peritoneum.