SMYD3 promotes implant metastasis of ovarian cancer via H3K4 trimethylation of integrin promoters

Detachment of cancer cells from the primary tumor and formation of spheroids in ascites is required for implantation metastasis in epithelial ovarian cancer (EOC), but the underlying mechanism of this process has not been thoroughly elucidated. To mimic this process, ovarian cancer cells were grown in 3D and 2D culture. Hey and OVCA433 spheroids exhibited decreased cell proliferation and enhanced adhesion and invasion. SMYD3 expression was elevated in ovarian carcinoma spheroids in association with increased H3K4 methylation. Depletion of SMYD3 by transient siRNA, stable shRNA knockdown and the SMYD3 inhibitor BCI-121 all decreased spheroid invasion and adhesion. Gene expression arrays revealed downregulation of integrin family members. Inhibition assays confirmed that invasion and adhesion of spheroids are mediated by ITGB6 and ITGAM. SMYD3-deficient cells regained the ability to invade and adhere after forced overexpression of SMYD3, ITGB6 and ITGAM. However, this biological ability was not restored by forced overexpression of SMYD3 in ITGB6- and/or ITGAM-deficient cancer cells. SMYD3 and H3K4me3 binding at the ITGB6 and ITGAM promoters was increased in spheroids compared to that in monolayer cells, and the binding was decreased when SMYD3 expression was inhibited, consistent with the expression changes in integrins. SMYD3 expression and integrin-mediated adhesion were also activated in an intraperitoneal xenograft model and in EOC patient spheroids. In vivo, SMYD3 knockdown inhibited tumor metastasis and reduced ascites volume in both the intraperitoneal xenograft model and a PDX model. Overall, our results suggest that the SMYD3-H3K4me3-integrin pathway plays a crucial role in ovarian cancer metastasis to the peritoneal surface.     

Fibroblasts in omentum activated by tumor cells promote ovarian cancer growth, adhesion and invasiveness

Omentum metastasis is a common occurrence in epithelial ovarian cancer (EOC), which is often accompanied by ascites that facilitates the spread of EOC cells. A subpopulation of fibroblasts-the cancer-associated fibroblasts (CAFs) are important promoters of tumor progression. We have shown previously that CAFs exist not only in omentum with EOC metastasis but also in omentum without metastasis. In the present study, using primary human fibroblasts isolated from normal omentum (NFs) and omentum with ovarian cancer metastasis (CAFs), we established in vitro coculture models and a 3D culture model mimicking human omentum structure for investigation of interactions between fibroblasts and cancer cells. We demonstrate that EOC cells activate NFs and promote their proliferation via transforming growth factor-β1 (TGF-β1) signaling, and the activated fibroblasts contribute to the invasion and adhesion of EOC cells. Moreover, EOC cells and NFs coculture led to overexpression of hepatocyte growth factor (HGF) and matrix metalloproteinase-2 (MMP-2) and adhesion and invasion of EOC cells could be partially suppressed by blocking the function of HGF or MMP-2. Additionally, mouse peritoneal dissemination models of EOC confirmed the activation of fibroblasts by cancer cells and the tumor growth- and metastasis-promoting effects of activated fibroblasts in vivo. Our findings indicate that activated fibroblasts in omentum form a congenial environment to promote EOC cells implantation. It is an intriguing concept that targeting the activation of omentum fibroblast through the inhibition of TGF-β1 signaling can be used as a new therapeutic strategy against ovarian cancer omentum metastases, which needs further study.     

Intact LKB1 activity is required for survival of dormant ovarian cancer spheroids

Metastatic epithelial ovarian cancer (EOC) cells can form multicellular spheroids while in suspension and disperse directly throughout the peritoneum to seed secondary lesions. There is growing evidence that EOC spheroids are key mediators of metastasis, and they use specific intracellular signalling pathways to control cancer cell growth and metabolism for increased survival. Our laboratory discovered that AKT signalling is reduced during spheroid formation leading to cellular quiescence and autophagy, and these may be defining features of tumour cell dormancy. To further define the phenotype of EOC spheroids, we have initiated studies of the Liver kinase B1 (LKB1)-5′-AMP-activated protein kinase (AMPK) pathway as a master controller of the metabolic stress response. We demonstrate that activity of AMPK and its upstream kinase LKB1 are increased in quiescent EOC spheroids as compared with proliferating adherent EOC cells. We also show elevated AMPK activity in spheroids isolated directly from patient ascites. Functional studies reveal that treatment with the AMP mimetic AICAR or allosteric AMPK activator A-769662 led to a cytostatic response in proliferative adherent ovarian cancer cells, but they fail to elicit an effect in spheroids. Targeted knockdown of STK11 by RNAi to reduce LKB1 expression led to reduced viability and increased sensitivity to carboplatin treatment in spheroids only, a phenomenon which was AMPK-independent. Thus, our results demonstrate a direct impact of altered LKB1-AMPK signalling function in EOC. In addition, this is the first evidence in cancer cells demonstrating a pro-survival function for LKB1, a kinase traditionally thought to act as a tumour suppressor.     

Involvement of SDF-1alpha/CXCR4 axis in the enhanced peritoneal metastasis of epithelial ovarian carcinoma

Epithelial ovarian carcinoma (EOC) spreads by implantation of tumor cells onto the human peritoneal mesothelial cells (HPMCs) lining the peritoneal cavity. The aim of this study was to determine whether the stromal cell-derived factor-1alpha (SDF-1alpha)/CXCR4 axis is involved in the interaction of EOC cells with HPMCs in peritoneal metastasis. Clinically, we first evaluated CXCR4 expression in sections from 36 primary EOCs using immunohistochemistry. We next examined whether SDF-1alpha played roles in EOC progression, including in proliferation, cell motility, attachment to HPMCs, and the in vivo development of peritoneal metastasis through CXCR4. Of the 36 carcinomas, 16 cases (44.4%) were positive for CXCR4 immunoexpression. Positive CXCR4 expression significantly predicted poorer overall survival compared with negative expression (p = 0.0069). We found CXCR4 expression in both EOC cells and HPMCs. In contrast, the level of production of SDF-1alpha by HPMCs was higher than that by various EOC cells. Functionally, SDF-1alpha induced enhanced attachment between ES-2 cells and HPMCs or extracellular matrix components. The enhancement of adhesion potential by SDF-1alpha was inhibited by AMD3100, a CXCR4 antagonist, and by phosphatidylinositol 3 kinase and p44/42 inhibitors. Furthermore, intraperitoneal treatment with AMD3100 resulted in reduced dissemination in nude mice inoculated with ES-2 cells. The present results suggest that there may be a link between the SDF-1alpha/CXCR4 axis and enhanced intraperitoneal dissemination of EOC and that CXCR4 may be a novel target for the treatment of EOC.     

PDGF BB induces VEGF secretion in ovarian cancer

We identified the platelet derived growth factor receptor (PDGFR) as a potential target in epithelial ovarian carcinoma (EOC). This led us to test whether inhibition of the PDGFR affects ovarian cancer cell proliferation and survival and regulates other processes critical to tumor growth and metastasis. We postulated that there is a correlation between the PDGF-PDGFR axis and the secretion of VEGF in EOC. VEGF secretion in ovarian tumors, cancer cells, serum and ascites fluid was measured by IHC, Western Blot and ELISA. We found increased VEGF expression and secretion in most ovarian tumors (by IHC), in EOC malignant ascites and in the conditioned media of primary ovarian cancer cells (quantified by ELISA). In malignant ascites, the levels of secreted PDGF BB and VEGF were strongly correlated (Pearson coefficient of correlation R = 0.728), suggesting that the two pathways interconnect. In PDGFR expressing immortalized ovarian cancer cells, PDGF potently induced VEGF secretion, while imatinib mesylate (Gleevec), a partially selective PDGFR inhibitor, reduced PDGF stimulated VEGF production to basal state. In ovarian cancer cells overexpressing constitutively active Akt, imatinib inhibited partially VEGF secretion, suggesting that the PI3K/Akt pathway is implicated in PDGF-stimulated VEGF secretion. In summary, these results suggest a correlation between the PDGF and VEGF networks in ovarian cancer cells and tumors. The effects of imatinib on VEGF secretion in tumor cells may affect the tumor microenvironment in a manner detrimental to tumor progression.     

Enhanced peritoneal ovarian tumor dissemination by tissue transglutaminase

Tissue transglutaminase (TG2) is involved in Ca(2+)-dependent aggregation and polymerization of proteins. We previously reported that TG2 mRNA is up-regulated in epithelial ovarian cancer (EOC) cells compared with normal ovarian epithelium. Here, we show overexpression of the TG2 protein in ovarian cancer cells and tumors and its secretion in ascites fluid and define its role in EOC. By stable knockdown and overexpression, we show that TG2 enhances EOC cell adhesion to fibronectin and directional cell migration. This phenotype is preserved in vivo, where the pattern of tumor dissemination in the peritoneal space is dependent on TG2 expression levels. TG2 knockdown diminishes dissemination of tumors on the peritoneal surface and mesentery in an i.p. ovarian xenograft model. This phenotype is associated with deficient beta(1) integrin-fibronectin interaction, leading to weaker anchorage of cancer cells to the peritoneal matrix. Highly expressed in ovarian tumors, TG2 facilitates i.p. tumor dissemination by enhancing cell adhesion to the extracellular matrix and modulating beta(1) integrin subunit expression.     

Cytokine analysis as a tool to understand tumour-host interaction in ovarian cancer

Epithelial ovarian cancer (EOC) is an immunogenic tumour and exploits many suppressive ways to escape immune eradication. EOC is known to spread primarily by tumour cell implantations in peritoneal cavity. Therefore, ascites may be an ideal fluid compartment to unravel the immune status of the peritoneal cavity.We analysed the expression of IL-1β, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12p70, IFN-γ, TNF-α, TNF-β, TGF-β and CCL22 in ovarian cancer ascites, representing immune activating and suppressing cytokines.We observed high expression of pro-inflammatory cytokines IL-6, IL-8 and immune suppressive cytokines IL-10, CCL22 and TGF-β in most samples whereas Th1 (IL-12p70, IFN-γ) and Th2 (IL-4, IL-5) cytokines were only detectable in 13% of the samples. TGF-β was only detected in latent form, questioning its immune suppressive role. CCL22 was in similar levels present in early stage compared to advanced stage tumours. At advanced stage, we observed a negative correlation with CCL22 levels and Th1/2 cytokine expression. We found a positive correlation between IL-6 concentration in ascites and residual disease after debulking. Additionally, IL-6 levels were remarkably higher at recurrence compared to primary advanced disease, which opens an opportunity for inhibition of IL-6 expression in the prevention of recurrence. Despite the heterogeneity of EOC and the complexity of cytokine functions, our results show that cytokine analysis in ascites may aid in understanding tumour-host interaction in EOC.     

Macrophages mediate inflammation-enhanced metastasis of ovarian tumors in mice

The tumor microenvironment is known to have a profound effect on tumor progression in a highly context-specific manner. We have investigated whether peritoneal inflammation plays a causative role in ovarian tumor metastasis, a poorly understood process. Implantation of human ovarian tumor cells into the ovaries of severe combined immunodeficient mice resulted in peritoneal inflammation that corresponds temporally with tumor cell dissemination from the ovaries. Enhancement of the inflammatory response with thioglycolate accelerated the development of ascites and metastases. Suppression of inflammation with acetyl salicylic acid delayed ascites development and reduced tumor implant formation. A similar prometastatic effect for inflammation was observed when tumor cells were injected directly into the peritoneum of severe combined immunodeficient mice, and in a syngeneic immunocompetent mouse model. Inflammation-modulating treatments did not affect primary tumor development or in vitro tumor cell growth. Depletion of peritoneal macrophages, but not neutrophils or natural killer cells, reduced tumor progression, as assessed by ascites formation and peritoneal metastasis. We conclude that inflammation facilitates ovarian tumor metastasis by a mechanism largely mediated by macrophages, and which may involve stromal vascular endothelial growth factor production. The confirmation of these findings in immunocompetent mice suggests relevance to human disease. Identifying the mechanisms by which macrophages contribute to tumor metastasis may facilitate the development of new therapies specifically targeting immune cell products in the tumor microenvironment.     

Matrix metalloproteinase inhibition prevents colon cancer peritoneal carcinomatosis development and prolongs survival in rats.

Matrix metalloproteinases (MMP) are enzymes responsible for extracellular matrix degradation which play a role in cancer progression and metastatic spreading. We investigated the effects of the MMP inhibitor, batimastat, in vitro on the proliferation and invasiveness of the rat colon cancer cell line DHD/K12, and in vivo on the growth of an aggressive model of peritoneal carcinomatosis producing haemorrhagic ascites and metastases, obtained in the rat by i.p. injection of DHD/K12 cells. MMP production was studied in conditioned culture media, solid tumors and ascitic fluid. In vivo, after injection of tumor cells on day 0, rats received i.p. daily either batimastat (30 mg/kg) or equal volume of vehicle from day 2 until killing on day 43 (series I) or from day 13 until death (series II). The grade of peritoneal carcinomatosis, ascite volume, number and size of liver metastases were evaluated in both series, and survival in series II. MMPs-1, -2 and -9 were identified in culture media, tumors and ascites. In vitro, batimastat did not modify DHD/K12 cell proliferation and slightly reduced cell invasion. In vivo, in series I, batimastat treatment totally prevented peritoneal carcinomatosis and liver metastasis development. In series II, it significantly prolonged survival (P < 0.0002) and reduced peritoneal carcinomatosis (P < 0.001) and hepatic metastases number as compared with controls. However, batimastat-treated rats of the two series had peritoneal inflammation with marked ascites. Nevertheless, inhibition of MMP is a new therapeutic approach which may be promising in treatment of microtumors as in more advanced cancer stages.     

Autocrine VEGF‐A/KDR loop protects epithelial ovarian carcinoma cells from anoikis

Epithelial ovarian carcinoma (EOC) patients are usually diagnosed at an advanced stage, characterized by interperitoneal carcinomatosis and production of large volumes of ascites. Vascular endothelial growth factor‐A (VEGF‐A) and its main signaling receptor VEGFR2 (KDR) are coexpressed in primary ovarian tumors, ascitic cells and metastases, suggesting the existence of an autocrine VEGF‐A/KDR loop in EOC cells. In the present study, we examined this possibility and explored the role of this autocrine loop in protecting EOC cells from apoptosis under anchorage free growth conditions (anoikis). We found that 3 different EOC cell lines (Caov3, OVCAR3, SKOV3) express both VEGF‐A and its receptors, including KDR. In these cells, KDR is constitutively phosphorylated and is detected both in the cell plasma membrane and in the nucleus. Treating EOC cells with specific internal inhibitors of KDR kinase activity or a VEGF‐A neutralizing antibody abolished KDR autophosphorylation and resulted in significant increase in apoptosis when cells were grown in single‐cell, anchorage‐free conditions. By contrast, these blocking reagents had no effect on cell viability when EOC cells were grown in adhesive monolayers. In summary, our results indicate that an autocrine VEGF‐A/KDR loop exists in EOC cells and that it plays a role in protecting the cells from anoikis. Our results imply that treating EOC patients with VEGF blocking agents may potentially reduce peritoneal dissemination by decreasing vascular permeability as well as inducing apoptosis of shed ovarian cancer cells in ascites. © 2008 Wiley‐Liss, Inc.     

Cell–cell and cell–matrix dynamics in intraperitoneal cancer metastasis

The peritoneal metastatic route of cancer dissemination is shared by cancers of the ovary and gastrointestinal tract. Once initiated, peritoneal metastasis typically proceeds rapidly in a feed-forward manner. Several factors contribute to this efficient progression. In peritoneal metastasis, cancer cells exfoliate into the peritoneal fluid and spread locally, transported by peritoneal fluid. Inflammatory cytokines released by tumor and immune cells compromise the protective, anti-adhesive mesothelial cell layer that lines the peritoneal cavity, exposing the underlying extracellular matrix to which cancer cells readily attach. The peritoneum is further rendered receptive to metastatic implantation and growth by myofibroblastic cell behaviors also stimulated by inflammatory cytokines. Individual cancer cells suspended in peritoneal fluid can aggregate to form multicellular spheroids. This cellular arrangement imparts resistance to anoikis, apoptosis, and chemotherapeutics. Emerging evidence indicates that compact spheroid formation is preferentially accomplished by cancer cells with high invasive capacity and contractile behaviors. This review focuses on the pathological alterations to the peritoneum and the properties of cancer cells that in combination drive peritoneal metastasis.     

Role of the CXCL12/CXCR4 axis in peritoneal carcinomatosis of gastric cancer

Peritoneal carcinomatosis is a frequent cause of death in patients with advanced gastric carcinoma. Because chemokines are now considered to play an important role in the metastasis of various malignancies, we hypothesized that they may be involved in the development of peritoneal carcinomatosis by gastric carcinoma. Human gastric carcinoma cell lines, which were all highly efficient in generating malignant ascites in nude mice upon i.p. inoculation, selectively expressed CXCR4 mRNA and protein. In particular, NUGC4 cells expressed CXCR4 mRNA at high levels and showed vigorous migratory responses to its ligand CXCL12. CXCL12 enhanced proliferation and rapid increases in phosphorylation of protein kinase B/Akt and extracellular signal-regulated kinase of NUGC4 cells. We also showed that AMD3100 (a specific CXCR4 antagonist) effectively reduced tumor growth and ascitic fluid formation in nude mice inoculated with NUGC4 cells. Additionally, we examined human clinical samples. Malignant ascitic fluids from patients with peritoneal carcinomatosis contained high concentrations of CXCL12 (4.67 ng/mL). Moreover, immunohistochemical analysis showed that 22 of 33 primary gastric tumors with peritoneal metastasis were positive for CXCR4 expression (67%), whereas only 4 of 16 with other distant metastasis were positive (25%). Notably, 22 of 26 CXCR4-expressing primary tumors developed peritoneal metastases (85%). CXCR4 positivity of primary gastric carcinomas significantly correlated with the development of peritoneal carcinomatosis (P < 0.001). Collectively, our results strongly suggest that the CXCR4/CXC12 axis plays an important role in the development of peritoneal carcinomatosis from gastric carcinoma. Thus, CXCR4 may be a potential therapeutic target for peritoneal carcinomatosis of gastric carcinoma.     

Replication of an integrin targeted conditionally replicating adenovirus on primary ovarian cancer spheroids

Replication competent viruses hold promise for treatment of advanced cancers resistant to available therapeutic modalities. Although preliminary clinical results have substantiated their efficacy, preclinical development of these novel approaches is limited by assay substrates. The evaluation of candidate agents could be confounded by differences between primary tumor cells and tumor cell lines, as discordance in the levels of surface receptors relevant for viral entry has been reported. Since primary tumor cells are difficult to analyze ex vivo for longitudinal observation of virus replication, we developed three-dimensional aggregates or spheroids of unpassaged and purified ovarian cancer cells as a means for prolonging primary tumor cell viability and as a three-dimensional in vitro model for replicative viral infection. Ovarian cancer cells purified from ascites samples were sustained for 30 days while retaining the infection profile with tropism modified and unmodified adenoviruses (Ads). Cell line and primary cell spheroids were used to quantitate the replication and oncolytic potency of replicative Ads in preclinical testing for human ovarian cancer trials. Therefore, spheroids provide a method to sustain purified unpassaged primary ovarian cancer cells for extended periods and to allow evaluation of replicative viruses in a three-dimensional model.     

Targeting myeloid cells in the tumor microenvironment enhances vaccine efficacy in murine epithelial ovarian cancer

Epithelial ovarian cancer (EOC) is typically diagnosed at advanced stages, and is associated with a high relapse rate. Patients in remission are ideal candidates for immunotherapy aimed at cure or prolonging disease-free periods. However, immunosuppressive pathways in the tumor microenvironment are obstacles to durable anti-tumor immunity. In a metastatic syngeneic mouse model of EOC, immunosuppressive macrophages and myeloid-derived suppressor cells (MDSCs) accumulate in the local tumor environment. In addition, resident peritoneal macrophages from non-tumor-bearing mice were highly immunosuppressive, abrogating stimulated T cell proliferation in a cell contact-dependent manner. Immunization with microparticles containing TLR9 and NOD-2 ligands (MIS416) significantly prolonged survival in tumor-bearing mice. The strategy of MIS416 immunization followed by anti-CD11b administration further delayed tumor progression, thereby establishing the proof of principle that myeloid depletion can enhance vaccine efficacy. In patients with advanced EOC, ascites analysis showed substantial heterogeneity in the relative proportions of myeloid subsets and their immunosuppressive properties. Together, these findings point to immunosuppressive myeloid cells in the EOC microenvironment as targets to enhance vaccination. Further studies of myeloid cell accumulation and functional phenotypes in the EOC microenvironment may identify patients who are likely to benefit from vaccination combined with approaches that deplete tumor-associated myeloid cells.     

Collagen type VI regulates the CDK4/6-p-Rb signaling pathway and promotes ovarian cancer invasiveness,stemness, and metastasis

The expression of collagen VI in primary ovarian tumors may correlate with tumor grade and response to chemotherapy. We have sought to elucidate the role of collagen VI in promoting ovarian cancer tumor growth and metastasis. Here we examined the effects of collagen VI on ovarian carcinoma stromal progenitor cells (OCSPCs). Epithelial-like OCSPCs (epi-OCSPCs) and mesenchymal-like OCSPCs (msc-OCSPCs) were analyzed by liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS). Differentially expressed genes were integrated with survival-related genes using The Cancer Genome Atlas (TCGA) data and confirmed in our samples. The roles of candidate genes and signaling pathways were further explored. We found that SKOV3/msc-OCSPCs possessed greater migration, invasion, and spheroid formation than SKOV3/epi-OCSPCs (P < 0.001). Expression of collagen alpha-3 (VI; COL6A3), which encodes collagen VI, was 90-fold higher in msc-OCSPCs than in epi-OCSPCs. Analysis of TCGA data and our samples indicated that high expression of COL6A3 was correlated with advanced-stage carcinoma (P < 0.01) and shorter overall survival (P < 0.01). In vitro, adding collagen VI, msc-OCSPCs, or knockdown collagen VI in msc-OCSPCs to epithelial ovarian carcinoma (EOC) cells augmented or decreased invasion and spheroid formation. Tumor dissemination to the peritoneal cavity and lung in mice following intraperitoneal coinjection with msc-OCSPCs and SKOV3-Luc cells and intravenous injection with COL6A3 and ES2 cells derived spheroids was significantly greater compare to coinjection with SKOV3-Luc cells alone or in combination with msc-OCSPCs/shCOL6A3 cells and msc-OCSPCs and ES2 derived spheroids. Knockdown of COL6A3 abolished the expression of DNMT1, CDK4, CDK6, and p-Rb in msc-OCSPCs and EOC spheroids. In contrast, overexpression of COL6A3 enhanced the expression of CDK4, CDK6, and p-Rb in SKOV3 cells. EOC spheroid formation, invasion, tumor growth, and metastasis were inhibited when COL6A3 downstream signaling pathway was blocked using CDK4/6 inhibitor LEE011. Our results suggested that collagen VI regulates the CDK4/6-p-Rb signaling pathway and promotes EOC invasiveness, stemness, and metastasis.     

钙黏素和整合素在卵巢上皮性癌中的研究进展

卵巢上皮性癌(EOC)是妇科癌症中最致命的恶性肿瘤。在过去的30年间,虽然诊断和治疗水平取得了进展,但是卵巢上皮性癌的发病率和死亡率却保持不变。卵巢上皮性癌腹膜转移癌晚期发病于附着的小簇癌细胞,这些癌细胞从初始部位脱落并经由腹水携带附着于腹部腹膜或网膜。这种行为表明细胞-细胞或细胞-基质黏附机制调节卵巢上皮性癌的生长和增殖。复杂的下游信号可能受黏附分子和共表达激活的信号蛋白之间的功能性串扰所影响,导致卵巢上皮性癌细胞的增殖/存活和迁移/侵袭。本文旨在阐述细胞与细胞机制的影响,该过程由钙黏素和细胞-细胞外基质黏附,由整合素对膜受体和细胞质蛋白质介导的信号级联放大,这些在卵巢上皮性癌细胞的增殖、迁移和侵袭中起着一定的作用。     

Efficacy of oncolytic reovirus against human gastric cancer with peritoneal metastasis in experimental animal model

The prognosis of gastric cancer patients with peritoneal dissemination is extremely poor, and the development of an effective treatment is necessary. The aim of this study was to investigate the efficacy of oncolytic reovirus against peritoneal metastasis in human gastric cancer using an experimental animal model. Four human gastric cancer cell lines, including MKN45p, NUGC4, MKN7 and KatoIII, a normal NIH3T3 cell line as a control, and reovirus serotype 3, were used in this study. We evaluated the cytopathic effect of reovirus and the Ras activity in each gastric cancer cell line in vitro. To evaluate oncolytic efficacy in vivo, reovirus (1x10(8) PFU) was administered into the peritoneal cavity of nude mice on days 7, 8 and 9 after inoculation with MKN45p cells. Mean volume of ascites and the total number and weight of the peritoneal tumors were measured after sacrifice. After reovirus infection, cytopathic effect was observed in all four gastric cancer cell lines, but not in the control cells. Ras activation assay showed that Ras activity in all four gastric cancer cell lines increased to a higher level than that in the control cells. In the animal model experiments, mean volume of ascites and the total number and weight of the peritoneal tumors in the reovirus treatment group were significantly lower than those in the control group. In conclusions, intraperitoneal administration of reovirus could be useful as a new modality against peritoneal metastasis in gastric cancer.     

Vascular endothelial growth factor activating matrix metalloproteinase in ascitic fluid during peritoneal dissemination of ovarian cancer

The role of vascular endothelial growth factor (VEGF) during peritoneal dissemination of ovarian carcinoma and the association with tumor microvessel density (MVD) and matrix metalloproteinase (MMP) activity was investigated. To this end, MVD, tumor tissue and ascitic fluid levels of VEGF, and MMP activity of ascitic fluid were examined in patients with ovarian cancer and benign ovarian tumor. The effect of ascites on cell growth, cell invasion activity and angiogenesis was investigated in vitro. Ascitic fluid and tumor tissue samples were obtained from 15 patients with benign ovarian tumor and 24 patients with ovarian carcinoma. Tissue extract and ascitic fluid levels of VEGF were measured using enzyme immunoassay. Tumor microvessels were detected immunohistochemically. MMP activity was measured by gelatin zymography. For the in vitro experiment, the SKOV-3 human ovarian carcinoma cell line was utilized. Cell growth was examined using MTT-assay, cell invasion activity was measured by Matrigel in vitro invasion assay, and neovascularization was assessed using an angiogenesis kit. VEGF levels in tissue extract and ascitic fluid, MVD, expression of active form MMP-2 in ascitic fluid and ascites volume were higher in ovarian cancer patients than in benign ovarian tumor patients. In addition, these were elevated in stage III and IV diseases compared to stage I and II diseases in ovarian cancer patients. MVD and expression of active form MMP-2 in ascitic fluid were closely correlated with VEGF level in tissue extracts, and MVD and ascites volume were closely correlated with VEGF level in ascitic fluid. Cell invasive activity and angiogenesis activity increased when cells were exposed to ascites. These increases were apparent when exposed to ascites obtained from ovarian cancer patients and were related to VEGF concentrations of ascitic fluid and expression of active form MMP-2 in ascitic fluid. The increased VEGF secreted from tumor cells is suggested to enhance tumor growth through angiogenesis, to produce ascites and to elevate ascitic VEGF concentrations and expression of active form MMP-2. The progression of peritoneal involvement may be induced by elevated VEGF and expression of active form MMP-2, followed by increased VEGF in the primary tumor. Control of VEGF in the primary tumor may become an effective strategy against peritoneal dissemination of ovarian carcinoma.