Transforming growth factor-beta1 signaling blockade attenuates gastric cancer cell-induced peritoneal mesothelial cell fibrosis and alleviates peritoneal dissemination both in vitro and in vivo

Regional Immunotherapy for Peritoneal Carcinomatosis in Gastroesophageal Cancer: Emerging Strategies to Re-Condition a Maladaptive Tumor Environment

Peritoneal carcinomatosis originating from gastric/gastroesophageal junction cancer (GC-PC) occurs in a defined subset of gastric cancer patients with unique clinical, pathologic, molecular and immunologic characteristics that create significant obstacles to effective treatment with modern therapy. Although systemic chemo- and immuno- therapy have yielded disappointing results in GC-PC, recent advances in the characterization of GC-PC and peritoneal immune biology present new opportunities for targeted therapeutics. In this review article, we discuss the distinct properties of GC-PC and the peritoneal immune environment as they pertain to current and investigative treatment strategies. We discuss pre-clinical studies and clinical trials relevant to the modulation of the peritoneal environment as a therapeutic intervention in GC-PC. Finally, we present a road map for future combinatorial strategies based on the conception of the peritoneal cavity as a bioreactor. Within this isolated compartment, prevailing immunosuppressive conditions can be altered through regional interventions toward an adaptive phenotype that would support the effectiveness of regionally delivered cellular therapy products. It is hoped that novel combination strategies would promote efficacy not only in the sequestered peritoneal environment, but also via migration into the circulation of tumor-reactive lymphocytes to produce durable systemic disease control, thereby improving oncologic outcome and quality of life in patients with GC-PC.

Intraperitoneal transfer of microRNA-29b-containing small extracellular vesicles can suppress peritoneal metastases of gastric cancer

Small extracellular vesicles (sEV) contain various microRNAs (miRNAs) and play crucial roles in the tumor metastatic process. Although miR-29b levels in peritoneal exosomes were markedly reduced in patients with peritoneal metastases (PM), their role has not been fully clarified. In this study, we asked whether the replacement of miR-29b can affect the development of PM in a murine model. UE6E7T-12, human bone marrow-derived mesenchymal stem cells (BMSCs), were transfected with miR-29b-integrating recombinant lentiviral vector and sEV were isolated from culture supernatants using ultracentrifugation. The sEV contained markedly increased amounts of miR-29b compared with negative controls. Treatment with transforming growth factor-β1 decreased the expression of E-cadherin and calretinin with increased expression of vimentin and fibronectin on human omental tissue-derived mesothelial cells (HPMCs). However, the effects were totally abrogated by adding miR-29b-rich sEV. The sEV inhibited proliferation and migration of HPMCs by 15% (p < 0.005, n = 6) and 70% (p < 0.005, n = 6), respectively, and inhibited adhesion of NUGC-4 and MKN45 to HPMCs by 90% (p < 0.0001, n = 5) and 77% (p < 0.0001, n = 5), respectively. MicroRNA-29b-rich murine sEV were similarly obtained using mouse BMSCs and examined for in vivo effects with a syngeneic murine model using YTN16P, a highly metastatic clone of gastric cancer cell. Intraperitoneal (IP) transfer of the sEV every 3 days markedly reduced the number of PM from YTN16P in the mesentery (p < 0.05, n = 6) and the omentum (p < 0.05, n = 6). Bone marrow mesenchymal stem cell-derived sEV are a useful carrier for IP administration of miR-29b, which can suppress the development of PM of gastric cancer.

Investigating the mechanisms of peritoneal metastasis in gastric adenocarcinoma using a novel ex vivo peritoneal explant model

Gastric adenocarcinoma, commonly known as stomach cancer, has a predilection for metastasis to the peritoneum, which portends limited survival. The peritoneal metastatic cascade remains poorly understood, and existing models fail to recapitulate key elements of the interaction between cancer cells and the peritoneal layer. To explore the underlying cellular and molecular mechanisms of peritoneal metastasis, we developed an ex vivo human peritoneal explant model. Fresh peritoneal tissue samples were suspended, mesothelial layer down but without direct contact, above a monolayer of red-fluorescent dye stained AGS human gastric adenocarcinoma cells for 24 h, then washed thoroughly. Implantation of AGS cells within the explanted peritoneum and invasion beyond the mesothelial layer were examined serially using real-time confocal fluorescence microscopy. Histoarchitecture of the explanted peritoneum was preserved over 5 days ex vivo. Both implantation and invasion were suppressed by restoration of functional E-cadherin through stable transfection of AGS cells, demonstrating sensitivity of the model to molecular manipulation. Thus, our ex vivo human peritoneal explant model permits meaningful investigation of the pathways and mechanism that contribute to peritoneal metastasis. The model will facilitate screening of new therapies that target peritoneal dissemination of gastric, ovarian and colorectal cancer.

LncRNA MSC-AS1 Is a Diagnostic Biomarker and Predicts Poor Prognosis in Patients With Gastric Cancer by Integrated Bioinformatics Analysis

Numerous studies have shown that long uncoded RNA (lncRNA) MSC-AS1 may play an important role in the occurrence and development of some types of cancer. However, its role in gastric cancer has rarely been discussed. This study aimed to clarify the association between lncRNA MSC-AS1 and gastric cancer using The Cancer Genome Atlas (TCGA) database. We determined the expression of MSC-AS1 using the Wilcoxon rank sum test; in addition, logistic regression was applied to evaluate the association between MSC-AS1 and clinicopathological characteristics. Also, Kaplan-Meier and Cox regression were used to evaluate the relationship between MSC-AS1 and survival. A nomogram was conducted to predict the impact of MSC-AS1 on prognosis. Moreover, Gene Set enrichment analysis (GSEA) was performed to annotate the biological function of MSC-AS1. Quantitative analysis of immune infiltration was carried out by single-set GSEA (ssGSEA). The MSC-AS1 level was elevated in gastric cancer tissues. An increased MSC-AS1 level was significantly correlated with T stage (odds ratio [OR] = 2.55 for T3 and T4 vs. T1 and T2), histological type (OR = 5.28 for diffuse type vs. tubular type), histological grade (OR = 3.09 for grade 3 vs. grades 1 and 2), TP53 status (OR = 0.55 for mutated vs. wild type), and PIK3CA status (OR = 0.55 for mutated vs. wild type) (all p < 0.05) by univariate logistic regression. Kaplan-Meier survival analysis showed high MSC-AS1 expression had a poor overall survival [hazard ratio (HR) = 1.75; 95% confidence interval (CI): 1.25-2.45; p = 0.001] and progression-free interval (HR = 1.47; 95% CI: 1.03-2.10; p = 0.034). Multivariate survival analysis revealed that MSC-AS1 expression (HR = 1.681; 95% CI: 1.057-2.673; p = 0.028) was independently correlated with overall survival. GSEA demonstrated that the P38/MAPK pathway, the VEGF pathway, the cell adhesion molecules cams, the NOD-like receptor signaling pathway were differentially enriched in the high MSC-AS1 expression phenotype. SsGSEA and Spearman correlation revealed the relationships between MSC-AS1 and macrophages, NK cells, and Tems were the strongest. Coregulatory proteins were included in the PPI network. Upregulated lncRNA MSC-AS1 might be a potential biomarker for the diagnosis and prognosis of gastric cancer.

Decreased exosome-delivered miR-486-5p is responsible for the peritoneal metastasis of gastric cancer cells by promoting EMT progress

Background

The present study aims to investigate the preliminary mechanism underlying the peritoneal metastasis of gastric cancer cells.

Methods

Exosomes from GC9811 cells (Con-Exo) and from GC9811-P cells (PM-Exo) were extracted by ultracentrifugation, which were identified with transmission electron microscopy (TEM) and nanoparticle trafficking analysis, as well as the expression of CD9, CD63, and CD81 detected by Western blot assay. α-SMA expression was determined by immunofluorescence assay and Western blot assay. The levels of Snail1, E-cadherin, and Actin-related protein 3 (ACTR3) were evaluated by Western blot assay. MiRNA array was performed on exosomes to screen the differentially expressed miRNAs. The expressions of miRNAs, SMAD2, CDK4, and ACTR3 were determined by QRT-PCR. The delivery of miR-486-5p was confirmed by laser confocal detection.

Results

Firstly, TEM, nanoparticle trafficking analysis, and Western blot assays were used to confirm the successful extraction of Con-Exo and PM-Exo. The incubation of Con-Exo and PM-Exo could decrease E-cadherin expression and increase of α-SMA respectively in HMrSV5 cells, with the increased proportion of fusiform cells. More significant changes were observed in PM-Exo-treated HMrSV5 cells. Secondary, compared to Con-Exo, miR-486-5p and miR-132-3p were found downregulated, and miR-132-5p was found upregulated in PM-Exo. The transfection of miR-486-5p and miR-132-3p was observed to suppress EMT, and the transfection of miR-132-3p was observed to induce EMT. Laser confocal detection confirmed the delivery of miR-486-5p from gastric cancer cells to HMrSV5 cells through exosomes. Lastly, the expression of Mothers against decapentaplegic homolog 2 (SMAD2), cyclin-dependent kinase 4 (CDK4), and ACTR3 was found to be downregulated via miR-486-5p.

Conclusion

Decreased delivery of miR-486-5p via exosomes might be responsible for the peritoneal metastasis of gastric cancer cells by promoting epithelial-mesenchymal transition progress.

The role of transforming growth factor β in upper gastrointestinal cancers: A systematic review

Esophageal and gastric malignancies are associated with poor prognosis, in part due to development of recurrences or metastases after curative treatment. The transforming growth factor β (TGF-β) pathway might play a role in the development of treatment resistance. In this systematic review, we provide an overview of preclinical studies investigating the role of TGF-β in esophageal and gastric malignancies. We systematically searched MEDLINE/PubMed and EMBASE for eligible preclinical studies describing the effect of TGF-β or TGF-β inhibition on hallmarks of cancer, such as proliferation, migration, invasion, angiogenesis and immune evasion. In total, 2107 records were screened and 45 articles were included, using mouse models and 45 different cell lines. TGF-β failed to induce apoptosis in twelve of sixteen tested cell lines. TGF-β could either decrease (five cell lines) or increase proliferation (seven cell lines) in gastric cancer cells, but had no effect in esophageal cancer cells. In all esophageal and all but two gastric cancer cell lines, TGF-β increased migratory, adhesive and invasive capacities. In vivo studies showed increased metastasis in response to TGF-β treatment. Additionally, TGF-β was shown to induce vascular endothelial growth factor production and differentiation of cancer-associated fibroblasts and regulatory T-cells. In conclusion, we found that TGF-β enhances hallmarks of cancer in most gastric and esophageal cancer cell lines, but not in all. Therefore, targeting the TGF-β pathway could be an attractive strategy in patients with gastric or esophageal cancer, but additional clinical trials are needed to define patient groups who would benefit most.

The role of the peritoneal microenvironment in the pathogenesis of colorectal peritoneal carcinomatosis

Recent insights have implicated mesothelial-to-mesenchymal transition (MMT) as a mechanism by which mesothelial cells can transdifferentiate into cancer-associated fibroblasts (CAFs) in several cancers metastasizing to the peritoneum. However, this was not evaluated extensively in colorectal cancer. We examined the presumed mesothelial origin of CAFs in three types of colorectal carcinoma: conventional type adenocarcinoma, mucinous carcinoma and signet ring cell carcinoma. We evaluated the expression of mesothelial, mesenchymal, angiogenesis and colorectal cancer-related markers in peritoneal samples of twelve colorectal cancer patients with peritoneal carcinomatosis and four control patients by immunohistochemistry. We observed morphological and immunohistochemical changes in the vicinity of tumor implants in all studied colorectal cancer types. Mesothelial cells acquired a spindle-shaped myofibroblast-like morphology, lost expression of mesothelial markers, and gained expression of mesenchymal markers. Analysis of consecutive tissue sections and double staining for mesothelial and mesenchymal markers revealed overlap in expression of mesothelial and CAF markers. These findings are highly suggestive of a mesothelial origin of CAFs in peritoneal carcinomatosis in colorectal cancer. Interfering with the process of MMT might be a valuable approach in treating and preventing peritoneal carcinomatosis. Differences observed between colorectal cancer types suggest that one single strategy might not be applicable.

SPHK1-induced autophagy in peritoneal mesothelial cell enhances gastric cancer peritoneal dissemination

Gastric cancer peritoneal dissemination (GCPD) has been recognized as the most common form of metastasis in advanced gastric cancer (GC), and the survival is pessimistic. The injury of mesothelial cells plays an important role in GCPD. However, its molecular mechanism is not entirely clear. Here, we focused on the sphingosine kinase 1 (SPHK1) in human peritoneal mesothelial cells (HPMCs) which regulates HPMCs autophagy in GCPD progression. Initially, we analyzed SPHK1 expression immunohistochemically in 120 GC peritoneal tissues, and found high SPHK1 expression to be significantly associated with LC3B expression and peritoneal recurrence, leading to poor prognosis. Using a coculture system, we observed that GC cells promoted HPMCs autophagy and this process was inhibited by blocking TGF-β1 secreted from GC cells. Autophagic HPMCs induced adhesion and invasion of GC cells. We also confirmed that knockdown of SPHK1 expression in HPMCs inhibited TGF-β1-induced autophagy. In addition, SPHK1-driven autophagy of HPMCs accelerated GC cells occurrence of GCPD in vitro and in vivo. Moreover, we explored the relationship between autophagy and fibrosis in HPMCs, observing that overexpression of SPHK1 induced HPMCs fibrosis, while the inhibition of autophagy weakened HPMCs fibrosis. Taken together, our results provided new insights for understanding the mechanisms of GCPD and established SPHK1 as a novel target for GCPD.

MicroRNA-21 contributes to high glucose-induced fibrosis in peritoneal mesothelial cells in rat models by activation of the Ras-MAPK signaling pathway via Sprouty-1

Peritoneal fibrosis remains to be one of the most severe causes of failure in continuous peritoneal dialysis. The current study cultured peritoneal mesothelial cells in high glucose to stimulate the environment of peritoneal fibrosis model in rats, and investigate whether microRNA-21 (miR-21) targeting Sprouty-1 affects high glucose-induced fibrosis in peritoneal mesothelial cells via the rennin angiotensin system (Ras)-mitogen-activated protein kinase (MAPK) signaling pathway, as well as potential mechanisms. Peritoneal tissues in fibrosis rats were collected to extract peritoneal mesothelial cells, which, after in vitro culture, were transfected with a series of mimic or inhibitor of miR-21, or the small interfering RNA (siRNA) against Sprouty-1. Reverse-transcription quantitative polymerase chain reaction and western blot analyses were performed to determine the levels of related genes or proteins. MTT assay and flow cytometry were conducted to observe the cell viability and cell apoptosis of peritoneal mesothelial cells. Dual-luciferase reporter gene assay revealed that Sprouty-1 is the target gene of miR-21. Peritoneal fibrosis manifested with elevated miR-21, extracellular-signal-regulated kinase (ERK), c-Jun NH2-terminal protein kinase (JNK), RAS and p38MAPK but reduced Sprouty-1. Cells transfected with miR-21 mimic exhibited decreased Sprouty-1 expressions, but increased levels of ERK, JNK, RAS, and p38MAPK. As for cellular process, miR-21 mimic or siRNA against Sprouty-1 exposure reduced cell viability, which resulted in more cells arrested at the G1 stage, and induced apoptosis. In contrast, miR-21 inhibitor exposure was observed to have induced effects on peritoneal mesothelial cells. These key findings provide evidence that miR-21 inhibits Sprouty-1 to promote the progression of fibrosis in peritoneal mesothelial cells by activating the Ras-MAPK signaling pathway.

Enhanced circulating transforming growth factor beta 1 is causally associated with an increased risk of hepatocellular carcinoma: a mendelian randomization meta-analysis

The aim of this study was to test the causal association between circulating transforming growth factor beta 1 (protein: TGF-β1 and coding gene: TGFB1) and hepatocellular carcinoma by choosing TGFB1 gene C-509T polymorphism as an instrument in a Mendelian randomization (MR) meta-analysis. Ten English articles were identified for analysis. Two authors independently assessed each article and abstracted relevant data. Odds ratio (OR) and weighted mean difference (WMD) with 95% confidence interval (CI) were synthesized under a random-effects model. Overall, the association of C-509T polymorphism with hepatocellular carcinoma was negative, but its association with circulating TGF-β1 was statistically significant, with a higher concentration observed in carriers of the -509TT genotype (WMD, 95% CI, P: 1.72, 0.67–2.78, 0.001) and -509TT/-509TC genotypes (WMD, 95% CI, P: 0.98, 0.43–1.53, < 0.001). In subgroup analysis, C-509T polymorphism was significantly associated with hepatocellular carcinoma in population-based studies under homozygous-genotype (OR, 95% CI, P: 1.74, 1.08–2.80, 0.023) and dominant (OR, 95% CI, P: 1.48, 1.01–2.17, 0.047) models. Further MR analysis indicated that per unit increase in circulating TGF-β1 was significantly associated with a 38% (95% CI: 1.03–4.65) and 49% (95% CI: 1.01–6.06) increased risk of hepatocellular carcinoma under homozygous-genotype and dominant models, respectively. Conclusively, based on a MR meta-analysis, our findings suggest that enhanced circulating TGF-β1 is causally associated with an increased risk of hepatocellular carcinoma.

Gastric cancer-derived exosomes promote peritoneal metastasis by destroying the mesothelial barrier

An intact mesothelium serves as a protective barrier to inhibit peritoneal carcinomatosis. Cancer-derived exosomes can mediate directional tumor metastasis; however, little is known about whether gastric cancer-derived exosomes will destroy the mesothelial barrier and promote peritoneal dissemination. Here, we demonstrate that gastric cancer-derived exosomes facilitate peritoneal metastasis by causing mesothelial barrier disruption and peritoneal fibrosis. Injury of peritoneal mesothelial cells elicited by gastric cancer-derived exosomes is through concurrent apoptosis and mesothelial-to-mesenchymal transition (MMT). Additionally, upregulation of p-ERK in peritoneal mesothelial cells is primarily responsible for the MMT while contributing little to apoptosis. Together, these data support the concept that exosomes play a crucial role in remodeling the premetastatic microenvironment and identify a novel mechanism for peritoneal metastasis of gastric carcinoma.

An engineered transforming growth factor β (TGF-β) monomer that functions as a dominant negative to block TGF-β signaling

The transforming growth factor β isoforms, TGF-β1, -β2, and -β3, are small secreted homodimeric signaling proteins with essential roles in regulating the adaptive immune system and maintaining the extracellular matrix. However, dysregulation of the TGF-β pathway is responsible for promoting the progression of several human diseases, including cancer and fibrosis. Despite the known importance of TGF-βs in promoting disease progression, no inhibitors have been approved for use in humans. Herein, we describe an engineered TGF-β monomer, lacking the heel helix, a structural motif essential for binding the TGF-β type I receptor (TβRI) but dispensable for binding the other receptor required for TGF-β signaling, the TGF-β type II receptor (TβRII), as an alternative therapeutic modality for blocking TGF-β signaling in humans. As shown through binding studies and crystallography, the engineered monomer retained the same overall structure of native TGF-β monomers and bound TβRII in an identical manner. Cell-based luciferase assays showed that the engineered monomer functioned as a dominant negative to inhibit TGF-β signaling with a Ki of 20-70 nm Investigation of the mechanism showed that the high affinity of the engineered monomer for TβRII, coupled with its reduced ability to non-covalently dimerize and its inability to bind and recruit TβRI, enabled it to bind endogenous TβRII but prevented it from binding and recruiting TβRI to form a signaling complex. Such engineered monomers provide a new avenue to probe and manipulate TGF-β signaling and may inform similar modifications of other TGF-β family members.

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)‐β 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‐β receptor reduced metastasis. MC‐derived CAFs showed activation of Smad‐dependent TGF‐β signalling, which was disrupted in OvCa cells, despite their elevated TGF‐β 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‐β‐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.

Blocking TGF-β1 by P17 peptides attenuates gastric cancer cell induced peritoneal fibrosis and prevents peritoneal dissemination in vitro and in vivo

Our previous study demonstrated that the peritoneal stroma environment favors proliferation of tumor cells by serving as a rich source of growth factors and chemokines known to be involved in tumor metastasis. In this study, we investigated the interaction between gastric cancer cells and peritoneal mesothelial cells, and determined the effects of TGF-β1 in this processing. Human peritoneal tissues and peritoneal wash fluid were obtained, which examined by hematoxylin and eosin staining or ELISA for measurements of TGF-β1 levels. The peritoneal mesothelial cells were co-incubated with the supernatants of gastric cancer, the expression of TGF-β1, collagen and fibronectin was observed by ELISA and western blot. We then investigated the effects of serum-free conditioned media from HSC-39 gastric cancer cells on the peritoneum of nude mice, and the effects of peritoneal fibrosis on the development of peritoneal metastasis in vivo. The peritoneum from gastric patients were thickened and contained extensive fibrosis. After co-culture both gastric tumor cells and mesothelial cells, we found that TGF-β1 expression was greatly increased in the co-culture system compared to individual culture condition. Serum-free Conditioned Media from HSC-39 was able to induce extracellular matrix expression in vitro and in vivo, and tumorigenicity in mice with peritoneal fibrosis was greater than in mice with normal peritoneum, while blocking TGF-β1 by peptide P17 can partially inhibit these effects. In conclusion, these results indicated that the interaction of gastric cancer with peritoneal fibrosis and determined that TGF-β1 plays a key role in induction of peritoneal fibrosis, which in turn affected dissemination of gastric cancer.

Significance of alpha smooth muscle actin expression in traumatic painful neuromas: a pilot study in rats

Treatment of painful neuromas remains a challenge and the mechanism of neuroma-associated pain is not yet fully understood. In this study, we aimed to observe the expression of alpha smooth muscle actin (α-SMA) in traumatic neuromas and to investigate its possible roles in the cause of neuropathic pain in a rat model. The rat sciatic nerve was used and the experiment was divided into two parts. In part I, our results showed significantly higher levels of α-SMA and the pain marker c-fos in the autotomy group than in the no-autotomy group. In part II, the expression of α-SMA in neuromas was down- and up-regulated using SB-431542 and GW9662, respectively. A significant correlation between autotomy scores and the expression level of α-SMA was found (R = 0.957; p < 0.001) and the expression level of α-SMA was positively related to the autotomy scores (R² = 0.915, p < 0.001). We concluded that the expression of α-SMA plays certain roles in the neuroma-associated pain, either as a direct cause of pain or as an indirect marker of existence of local mechanical stimuli. Our findings may provide new insights into the development of new treatment modalities for the management of intractable painful neuromas.

Endoglin overexpression mediates gastric cancer peritoneal dissemination by inducing mesothelial cell senescence

Peritoneal dissemination (PD), which is highly frequent in gastric cancer (GC) patients, is the main cause of death in advanced GC. Senescence of human peritoneal mesothelial cells (HPMC) may contribute to GC peritoneal dissemination (GCPD). In this study of 126 patients, we investigated the association between Endoglin expression in GC peritoneum and the clinicopathological features. The prognosis of patients was evaluated according to Endoglin and ID1 expression. In vitro, GC cell (GCC)-HPMC coculture was established. Endoglin and ID1 expression was evaluated by Western blot. Cell cycle and HPMC senescence were analyzed after harvesting HPMC from the coculture. GCC adhesion and invasion to HPMC were also assayed. Our results showed that positive staining of Endoglin (38%) was associated with a higher TNM stage and higher incidence of GCPD (both P < .05). Kaplan-Meier analysis showed that the patients who were Endoglin positive had a shorter survival time compared with Endoglin-negative patients (P = .02). Using the HPMC and GCC adherence and invasion assay, we demonstrated that transforming growth factor beta 1 (TGF-β)1-induced HPMC senescence was attenuated by silencing the Endoglin expression, which also prevented GCC attachment and invasion. Our study indicated a positive correlation between Endoglin overexpression and GCPD. Up-regulated Endoglin expression induced HPMC senescence via TGF-β1 pathway. The findings suggest that Endoglin-induced HPMC senescence may contribute to peritoneal dissemination of GCCs.

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.