Scirrhous Gastric Carcinoma Cells Research Articles

Abstract 5160: Extracellular vesicles from scirrhous gastric cancer cells induce premetastatic niche formation for peritoneal metastasis

Abstract Background: Human scirrhous gastric carcinoma (SGC) is also known as diffusely infiltrating carcinoma, type 4 on Borrmann’s criteria, and linitis plastica-type carcinoma. SGC is characterized by frequent peritoneal metastasis, high proliferation and infiltration activity with extensive fibrosis in the tumor stroma. We previously reported that a soluble factor(s) from SGC cells changed the peritoneum to pre-metastatic niche such as round shape of mesothelial cells and peritoneal fibrosis, which is a favorable environment for cancer cells to metastasize. Extracellular vesicles (EVs; Exosomes) might be one of soluble factor(s) which might change the peritoneal component to pre-metastatic niche. In this study, we investigated the effect of EVs from SGC cells on the pre-metastatic niche formation of the peritoneum. Methods: Four SGC cell lines, OCUM-2M, OCUM-2MD3, OCUM-12, KATO-III, 2 non-SGC cell lines, MKN74, MKN45, and peritoneal mesothelial cells (PM cells) were used. The effect of EVs from gastric cancer cells on the peritoneum was examined in vitro and in vivo, as follows. PKH26-labeled EVs from OCUM-2MD3 cells were intravenously injected into nude mice for 3 weeks, then we examined the distribution of PKH26-labeled EVs by a fluorescence microscope. Next, we injected EVs intraperitoneally into nude mice, and investigated the morphology of peritoneum. Effect of EVs on the gene expression of PM cells was examined by RT-PCR. Clinical significance of EVs markers, CD9 and CD63, was evaluated by immunohistochemistry using 63 human gastric cancer specimens. Results: PKH26-labeled EVs frequently distributed to peritoneum and the liver. The morphology of PM cells changed from round shape to spindle shape by EVs addiction in vitro and in vivo. mRNA expression level of ZEB and N-cadherin of PM cells was significantly increased following the addiction of EVs. The high expression of EVs markers, CD9 and CD63, was significantly correlated with frequent peritoneal metastasis. Conclusion: EVs from SGC cells might frequently distribute to mesothelial cells of peritoneum. EVs from SGC cells might play an important role for the formation of a pre-metastatic niche on peritoneum by the morphologic change of peritoneal mesothelial cells. Citation Format: Tomohisa Okuno, Masakazu Yashiro, Shuhei Kushiyama, Sadaaki Nishimura, Shingo Togano, Kenji Kuroda, Tatsuro Tamura, Takahiro Toyokawa, Hiroaki Tanaka, Kazuya Muguruma, Kosei Hirakawa, Masaichi Ohira. Extracellular vesicles from scirrhous gastric cancer cells induce premetastatic niche formation for peritoneal metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5160.

Abstract 5219: Effect of extracellular vesicles from gastric cancer cells on the morphologic and genetic changes of peritoneal mesothelial cells

Abstract Background: Gastric cancer is a major cause of cancer death, particularly on the basis of peritoneal metastasis. Human scirrhous gastric carcinoma (SGC), diffusely infiltrating carcinoma, or Borrman type 4 also known as linitis plastica-type carcinoma is characterized by rapid cancer cell infiltration and proliferation accompanied by extensive stromal fibrosis. SGC account for about 10% of all gastric carcinomas, and carry an extremely worse prognosis than other types of gastric carcinoma, reflecting their frequent peritoneal metastasis. We previously reported that SGC cells (“seed”) might change the peritoneum to favorable environment, so-called pre-metastatic niche (“soil”), (Cancer 77:1668-75, 1996). Recently, it has been clarified that extracellular vesicles (EVs) play an important role for cell-cell interactions. In this study, we investigated the effect of EVs from SGC cells on the pre-metastatic niche formation of the peritoneum. Methods: A SGC cell line, OCUM-2MD3, OCUM-12, KATO-III, gastric cancer cell line, MKN74, MKN45, and peritoneal mesothelial cells (PM cells) were used. PKH26-labeled EVs from OCUM-2MD3 cells were intravenously injected into nude mice, and the distribution of EVs was examined by a fluorescence microscope. The morphology of PM cells was investigated in the addiction of EVs from various gastric cancer cell lines using a phase-contrast microscope. And gene expression was examined by RT-PCR in the presence or absence of EVs from OCUM-2MD3. Clinical significance of EVs markers CD9 and CD63 was immunohistochemically evaluated using 63 human gastric cancer specimens. Results: PKH26-labeled EVs were frequently found in the peritoneum, stomach and liver, but rare in lung and brain of mice. Peritoneal mesothelial cells uptake EVs of gastric cancer cells and change morphology from cobblestone shape to spindle shape in vitro. mRNA expression level of MMPs and integrins in PM cells was increased following the addiction of EVs, in compared with the control. The high expression of CD9 and CD63 was significantly correlated with distant metastasis. Conclusion: EVs from gastric cancer cells might induce a pre-metastatic niche at peritoneum by the morphologic and genetic changes of mesothelial cells. Citation Format: Tomohisa Okuno, Masakazu Yashiro, Shingo Togano, Kenji Kuroda, Yuichiro Miki, Hiroaki Kasashima, Kosei Hirakawa, Masaichi Ohira. Effect of extracellular vesicles from gastric cancer cells on the morphologic and genetic changes of peritoneal mesothelial cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5219.

Direct Interaction between Carcinoma Cells and Cancer Associated Fibroblasts for the Regulation of Cancer Invasion.

The tumor stroma acts as an essential microenvironment of the cancer cells, which includes many different types of non-cancerous cells and the extracellular matrix (ECM). Stromal fibroblasts (SFs) are the major cellular constituents of the tumor stroma and are often called cancer-associated fibroblasts (CAFs). They are often characterized by α-smooth muscle actin (αSMA) expression, which is indicative of the myofibroblast phenotype and strong contractility. These characteristics contribute to the remodeling and stiffening of the stromal ECM, thereby offering an appropriate field for cancer cell invasion. Importance of the tumor stroma in cancer progression has recently been highlighted. Moreover, several reports suggest that stromal fibroblasts interact with adjacent cancer cells through soluble factors, exosomes, or direct cell-cell adhesion to promote cancer cell invasion. In this review, current models of the regulation of cancer cell invasion by surrounding fibroblasts are summarized, including our recent work on the interaction between stromal fibroblasts and scirrhous gastric carcinoma (SGC) cells by using a three-dimensional (3D) culture system. Further mechanistic insights into the roles of the interaction between cancer cells and stromal fibroblasts in cancer invasion will be required to identify novel molecular targets for preventing cancer cell invasion.

Abstract 3601: Stromal fibroblasts mediate extracellular matrix remodeling and invasion of scirrhous gastric carcinoma cells

Abstract Scirrhous gastric carcinoma (SGC; also called diffusely infiltrative carcinoma, Borrmann's type-IV carcinoma, or the linitis plastica-type carcinoma) has the worst prognosis of all gastric cancers, owing to its rapid expansion by invasion and frequent peritoneal dissemination. Due to the increased proliferation of stromal fibroblasts (SFs) that occurs within SGC lesions and the peritoneal metastatic sites, SFs have been proposed to support the progression of this disease. However, the biological and molecular basis and the pathological role of the intercellular interaction between SGC cells and SFs remain largely unknown. In this study, we investigated the role of SFs in the invasion of the extracellular matrix (ECM) by SGC cells. When SGC cells were cocultured with SFs derived from SGC tissue on three-dimensional (3D) Matrigel, they were attracted together to form large cellular aggregates that invaded within the Matrigel. Time-lapse imaging revealed that this process was associated with extensive contraction and remodeling of the ECM. Immunofluorescence and biochemical analysis showed that SGC cells stimulate phosphorylation of myosin light chain and actomyosin-mediated mechanical remodeling of the ECM by SFs. By utilizing this assay system for inhibitor library screening, we have identified several inhibitors that potently suppress the cooperation between SGC cells and SFs to form the invasive structures. Among them, a Src inhibitor dasatinib impaired the interaction between SGC cells and SFs both in vitro and in vivo and effectively blocked peritoneal dissemination of SGC cells. These results indicate that SFs mediate mechanical remodeling of the ECM by SGC cells, thereby promoting invasion and peritoneal dissemination of SGC. Citation Format: Hideki Yamaguchi, Kazuyoshi Yanagihara, Masakazu Yashiro, Ryuichi Sakai. Stromal fibroblasts mediate extracellular matrix remodeling and invasion of scirrhous gastric carcinoma cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3601. doi:10.1158/1538-7445.AM2014-3601

Stromal Fibroblasts Mediate Extracellular Matrix Remodeling and Invasion of Scirrhous Gastric Carcinoma Cells

Scirrhous gastric carcinoma (SGC) has the worst prognosis of all gastric cancers, owing to its rapid expansion by invasion and frequent peritoneal dissemination. Due to the increased proliferation of stromal fibroblasts (SFs) that occurs within SGC lesions and the peritoneal metastatic sites, SFs have been proposed to support the progression of this disease. However, the biological and molecular basis and the pathological role of the intercellular interaction between SGC cells and SFs remain largely unknown. In this study, we investigated the role of SFs in the invasion of the extracellular matrix (ECM) by SGC cells. When SGC cells were cocultured with SFs derived from SGC tissue on three-dimensional (3D) Matrigel, they were attracted together to form large cellular aggregates that invaded within the Matrigel. Time-lapse imaging revealed that this process was associated with extensive contraction and remodeling of the ECM. Immunofluorescence and biochemical analysis showed that SGC cells stimulate phosphorylation of myosin light chain and actomyosin-mediated mechanical remodeling of the ECM by SFs. By utilizing this assay system for inhibitor library screening, we have identified several inhibitors that potently suppress the cooperation between SGC cells and SFs to form the invasive structures. Among them, a Src inhibitor dasatinib impaired the interaction between SGC cells and SFs both in vitro and in vivo and effectively blocked peritoneal dissemination of SGC cells. These results indicate that SFs mediate mechanical remodeling of the ECM by SGC cells, thereby promoting invasion and peritoneal dissemination of SGC.

Abstract 1244: Differential requirements for the receptor tyrosine kinase c-Met in scirrhous gastric carcinoma cell lines

Abstract The prognosis of patients with scirrhous gastric carcinoma (SGC) has been very poor. SGC cells do not form obvious tumor mass, but cause diffuse infiltration and eventually rigid thickening of the gastric wall. Furthermore, SGC cells frequently infiltrate through gastric serosa and cause peritoneal dissemination. However, the mechanisms underlying the progression of SGC have not yet been fully elucidated. In the present study, we performed immunoblotting and proteomic analyses of tyrosine-phosphorylated proteins in differentiated non-SGC cell lines (MKN7, MKN1, and MKN74) and poorly differentiated or SGC cell lines (MKN45, NUGC-4, KATO III, HSC59, 58As9, HSC44-PE, and 44As3) to identify signaling pathways and molecules that are characteristics of SGC. We found that the tyrosine kinase receptor c-Met is overexpressed and highly phosphorylated in SGC cell lines. c-Met is a cell surface receptor for HGF and implicated in the growth, survival, invasion, and metastasis of various human cancers. Amplification of c-Met gene in SGC was also previously reported. We analyzed the downstream signaling pathways of c-Met in SGC cells by using two c-Met inhibitors PHA-665752 and JNJ-38877605. Treatment of 58As9 cells with the c-Met inhibitors markedly inhibited phosphorylation of Erk, Akt, and Stat3, but promoted phosphorylation of Src. In contrast, 44As3 cells treated with the c-Met inhibitors showed no significant changes in phosphorylation of these molecules, in spite of successful inhibition of c-Met phosphorylation. Reflecting these observations, c-Met inhibitors blocked cell proliferation and caused morphological alterations in 58As9 cells but not in 44As3 cells. Similar results were obtained when MKN45 and NUGC-4 cells were analyzed in the same manner: MKN45 cells but not NUGC-4 cells were sensitive to c-Met inhibition. These results suggest that SGC can be classified into two subtypes according to their dependencies on the c-Met signaling pathway. Further studies are now conducted to identify therapeutic targets in c-Met-independent SGC cell lines. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1244. doi:1538-7445.AM2012-1244

Abstract 47: Cancer-associated fibroblasts mediate extracellular matrix remodeling and three-dimensional invasion of scirrhous gastric carcinoma cells

Abstract Scirrhous gastric carcinoma (SGC; also called diffusely infiltrative carcinoma, Borrmann's type-IV carcinoma, or the linitis plastica-type carcinoma) have the worst prognosis among various types of gastric cancer, owing to highly progressive invasion, frequent metastasis to lymph nodes, and high incidence of peritoneal dissemination. SGC cells rapidly and diffusively infiltrate through the submucosa without forming obvious tumor mass and induce extensive stromal fibrosis, resulting in thickening and stiffening of the gastric wall. Because histophathological analyses have shown that massive proliferation of stromal fibroblasts occur within lesions of SGC, cancer-associated fibroblasts (CAFs) have been proposed to support the progression of SGC. However, biological and molecular basis of the interaction between SGC cells and CAFs remains largely unknown. In this study, we investigated the roles of CAFs in invasion and extracellular matrix (ECM) remodeling by SGC cells. When 44As3 SGC cells were co-cultured with CaF37 SGC-derived fibroblasts on 3D Matrigel, they formed large cell aggregates that invade into the Matrigel. Other SGC cell lines, HSC59 and HSC44PE, but not differentiated non-SGC gastric caner cell lines, MKN7, MKN1, and MKN74, formed invasive cell aggregate with CaF37 cells. Time-lapse imaging of SGC and CaF37 cells, and of fluorescent microsphere embedded in the Matrigel revealed that this process is associated with extensive contraction and remodeling of ECM. In order to further characterize the ECM remodeling activity of CAFs, we cultured 44As3 and CaF37 cells on fluorescent gelatin-coated coverslips. CaF37 cells caused disruption of the gelatin matrix and this activity was further promoted by co-culturing them with 44As3 cells. Immunoblotting and immnofluorescence analyses revealed that phosphorylation of myosin light chain was significantly increased in CaF37 cells co-cultured with 44As3 cells. Finally, a myosin II inhibitor blebbistatin blocked the three-dimensional invasion and ECM remodeling by 44As3 and CaF37 cells. These results indicate that SGC cells promote actomyosin-mediated contractility of stromal fibroblasts to remodel ECM during invasion. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 47. doi:1538-7445.AM2012-47

PI3K/Akt signalling is required for the attachment and spreading, and growth in vivo of metastatic scirrhous gastric carcinoma

Background:PI3K/Akt (PKB) pathway has been shown in several cell types to be activated by ligands to cell surface integrins, leading to the metastasis of tumour cells. The signalling pathways involved in the metastatic spread of human scirrhous gastric carcinoma cells have not been defined.Methods:The role of the PI3K/Akt pathway in an extensive peritoneal-seeding cell line, OCUM-2MD3 and a parental cell line, OCUM-2M, was investigated by assessing in vitro adhesion and spreading assay, and in vivo peritoneal metastatic model. We also examined the correlation of PI3K/Akt pathway with integrin signals by immunoprecipitations, using cells by transfection with mutant p85 (Δp85).Results:Adhesiveness and spreading of OCUM-2MD3 cells on collagen type IV was significantly decreased by PI3K inhibitors and expression of mutant p85, but not by inhibitors of protein kinase C (PKC) or extracellular signal-regulated kinase (ERK). Immunoprecipitation studies indicated that the PI3K/Akt pathway was associated with integrin signalling through Src and vinculin. In an in vivo experimental metastasis model, p85 inhibition reduced peritoneal metastasis of OCUM-2MD3 cells.Conclusion:PI3K/Akt signalling may be required for integrin-dependent attachment and spreading of scirrhous gastric carcinoma cells, and would be translated into generating better strategies to optimise their use in cancer clinical trials.

Upregulation of cancer-associated myofibroblasts by TGF-β from scirrhous gastric carcinoma cells

Background:Myofibroblasts in the cancer microenvironment have recently been implicated in tumour growth and metastasis of gastric cancer. However, the mechanisms responsible for the regulation of myofibroblasts in cancer-associated fibroblasts (CAFs) remain unclear. This study was performed to clarify the mechanisms for regulation of myofibroblasts in gastric cancer microenvironment.Methods:Two CAFs (CaF-29 and CaF-33) from the tumoural gastric wall and a normal fibroblast (NF-29) from the nontumoural gastric wall, 4 human gastric cancer cell lines from scirrhous gastric cancer (OCUM-2MD3 and OCUM-12), and non-scirrhous gastric cancer (MKN-45 and MKN-74) were used. Immunofluorescence microscopy by triple-immunofluorescence labelling (α-SMA, vimentin, and DAPI) was performed to determine the presence of α-SMA-positive myofibroblasts. Real-time RT–PCR was performed to examine α-SMA mRNA expression.Results:Immunofluorescence microscopy showed that the frequency of myofibroblasts in CaF-29 was greater than that in NF-29. The number of myofibroblasts in gastric fibroblasts gradually decreased with serial passages. Transforming growth factor-β (TGF-β) significantly increased the α-SMA expression level of CAFs. Conditioned medium from OCUM-2MD3 or OCUM-12 cells upregulated the α-SMA expression level of CAFs, but that from MKN-45 or MKN-74 cells did not. The α-SMA upregulation effect of conditioned medium from OCUM-2MD3 or OCUM-12 cells was significantly decreased by an anti-TGF-β antibody or Smad2 siRNA.Conclusion:Transforming growth factor-β from scirrhous gastric carcinoma cells upregulates the number of myofibroblasts in CAFs.

RhoA/ROCK signaling mediates plasticity of scirrhous gastric carcinoma motility

The small guanosine triphosphatase (GTPase) Rho and its downstream effector Rho-associated kinase (ROCK) is one of a key mediator involved in controlling focal adhesions and the dynamics of actin stress fibers. The molecular mechanisms for the function of Rho/ROCK pathway leading to the progression in scirrhous gastric carcinoma cells have not been defined. The activation of RhoA in several gastric carcinoma cells was examined. The role of RhoA/ROCK pathway in the metastatic processes of gastric carcinoma cells, using a human scirrhous gastric cancer cell line, OCUM-2MD3 was investigated by in vitro adhesion and invasion assay. The effect of ROCK inhibitor, Y-27632 on the mRNA expression of the integrin family and MMP in gastric carcinoma cells was subsequently examined by Reverse transcriptional (RT)-PCR analysis. Finally, Random OCUM-2MD3 cell motility was evaluated using Time-lapse microscopy. ROCK inhibitor significantly increased the adhesion of OCUM-2MD3 cells to the extracellular matrix (ECM) protein matrigel. Further examination using ECM components showed enhanced binding ability was obtained only in laminin and Integrin subunits α3-integrin was clearly up-regulated by treatment with Y-27632 in OCUM-2MD3 cells. ROCK inhibitor also enhanced the invasion of OCUM-2MD3 cells through matrigel and the expression of membrane-type 1 matrix metalloproteinase (MT1-MMP). Time-lapse microscopy showed conversion of OCUM-2MD3 cells from round to more elongated morphology in the presence of Y-27632, suggesting that inhibition of RhoA/ROCK pathway undergo a so-called 'amoeboid to mesenchymal' transition. The fact that Rac1 inhibitor decreased the facilitated invasion by ROCK inhibitor suggested the possibility that increased invasion ability of OCUM-2MD3 cells was related to Rac activity. These data may suggest that RhoA/ROCK regulate plasticity of metastatic gastric carcinoma via mesenchymal-amoeboid transition, leading to provide new insights for designing a new and effective treatment for this type of refractory carcinoma.

The Metastasis-Associated microRNA miR-516a-3p Is a Novel Therapeutic Target for Inhibiting Peritoneal Dissemination of Human Scirrhous Gastric Cancer

Although aberrant microRNA (miRNA) is expressed in different types of human cancer tissues, its pathophysiologic role and the relevance of tumorigenesis and metastasis are still largely unknown. Here, we defined miRNAs involved in cancer metastasis (metastamirs) using an established mouse model for peritoneal dissemination of human scirrhous gastric carcinoma cells. Highly metastatic derivatives (44As3 cells) were derived from the parental cells originally isolated from patients (HSC-44PE cells). Using microarray analysis to identify differentially expressed miRNAs in 44As3 and HSC-44PE cells, we focused on miR-516a-3p as a candidate antimetastatic miRNA (antimetastamir) whose functions in cancer had not been studied. We confirmed attenuated expression of miR-516a-3p in 44As3 cells compared with HSC-44PE cells by Northern blot analysis and quantitative reverse transcriptase PCR. Stable ectopic overexpression in 44As3-miR-516a-3p cells permitted identification of sulfatase 1 as a direct target of the miRNA, through use of the isobaric tagging reagent iTRAQ and the QSTAR Elite Hybrid LC-MS/MS system. Sulfatase 1 is known to remove 6-O-sulfates from heparan sulfate proteoglycans on the cell surface, causing release of membrane-bound Wnt ligands from cells. Consistent with this function, Western blot analyses revealed high levels of Wnt3a, Wnt5a, and nuclear β-catenin accumulation in 44As3 cells but relatively reduced levels in 44As3-miR-516a-3p cells. Notably, orthotopic inoculation of nude mice with 44As3-miR-516a-3p cells yielded significantly longer survival periods compared with mice inoculated with control 44As3 cells. Through atelocollagen-mediated delivery of an miR-516a-3p expression vector into orthotopic 44As3 tumors, we documented its feasibility as a treatment agent. Our findings define the miRNA miR-516-3p as an antimetastamir with potential therapeutic applications in blocking metastatic dissemination of gastric cancers.

ARAP3 inhibits peritoneal dissemination of scirrhous gastric carcinoma cells by regulating cell adhesion and invasion

During the analysis of phosphotyrosine-containing proteins in scirrhous gastric carcinoma cell lines, we observed an unusual expression of Arf-GAP with Rho-GAP domain, ankyrin repeat and PH domain 3 (ARAP3), a multimodular signaling protein that is a substrate of Src family kinases. Unlike other phosphotyrosine proteins, such as CUB domain-containing protein 1 (CDCP1) and Homo sapiens chromosome 9 open reading frame 10/oxidative stress-associated Src activator (C9orf10/Ossa), which are overexpressed and hyperphosphorylated in scirrhous gastric carcinoma cell lines, ARAP3 was underexpressed in cancerous human gastric tissues. In this study, we found that overexpression of ARAP3 in the scirrhous gastric carcinoma cell lines significantly reduced peritoneal dissemination. In vitro studies also showed that ARAP3 regulated cell attachment to the extracellular matrix, as well as invasive activities. These effects were suppressed by mutations in the Rho-GTPase-activating protein (GAP) domain or in the C-terminal two tyrosine residues that are phosphorylated by Src. Thus, the expression and phosphorylation state of ARAP3 may affect the invasiveness of cancer by modulating cell adhesion and motility. Our results suggest that ARAP3 is a unique Src substrate that suppresses peritoneal dissemination of scirrhous gastric carcinoma cells.

Elevated dietary linoleic acid increases gastric carcinoma cell invasion and metastasis in mice

Background:Dietary (n-6)-polyunsaturated fatty acids influence cancer development, but the mechanisms have not been well characterised in gastric carcinoma.Methods:We used two in vivo models to investigate the effects of these common dietary components on tumour metastasis. In a model of experimental metastasis, immunocompromised mice were fed diets containing linoleic acid (LA) at 2% (LLA), 8% (HLA) or 12% (VHLA) by weight and inoculated intraperitoneally (i.p.) with human gastric carcinoma cells (OCUM-2MD3). To model spontaneous metastasis, OCUM-2MD3 tumours were grafted onto the stomach walls of mice fed with the different diets. In in vitro assays, we investigated invasion and ERK phosphorylation of OCUM-2MD3 cells in the presence or absence of LA. Finally, we tested whether a cyclooxygenase (COX) inhibitor, indomethacin, could block peritoneal metastasis in vivo.Results:Both the HLA and VHLA groups showed increased incidence of tumour nodules (LA: 53% HLA: 89% VHLA: 100% P<0.03); the VHLA group also displayed increased numbers of tumour nodules and higher total volume relative to LLA group in experimental metastasis model. Both liver invasion (78%) and metastasis to the peritoneal cavity (67%) were more frequent in VHLA group compared with the LLA group (22% and 11%, respectively; P<0.03) in spontaneous metastasis model. We also found that the invasive ability of these cells is greatly enhanced when exposed to LA in vitro. Linoleic acid also increased invasion of other scirrhous gastric carcinoma cells, OCUM-12, NUGC3 and MKN-45. Linoleic acid effect on OCUM-2MD3 cells seems to be dependent on phosphorylation of ERK. The data suggest that invasion and phosphorylation of ERK were dependent on COX. Indomethacin decreased the number of tumours and total tumour volume in both LLA and VHLA groups. Finally, COX-1, which is known to be an important enzyme in the generation of bioactive metabolites from dietary fatty acids, appears to be responsible for the increased metastatic behaviour of OCUM-2MD3 cells in the mouse model.Conclusion:Dietary LA stimulates invasion and peritoneal metastasis of gastric carcinoma cells through COX-catalysed metabolism and activation of ERK, steps that compose pathway potentially amenable to therapeutic intervention.

Abstract 5118: Rho/ROCK pathway mediates plasticity of scirrhous gastric carcinoma cell motility

Abstract The small guanosine triphosphatase (GTPase) Rho and its downstream effector Rho-associated kinase (ROCK) is one of a key mediator involved in controlling focal adhesions and the dynamics of actin stress fibers. This pathway has been shown to play important roles in the regulation of various cellular processes, such as cell shape changes and adhesion dynamics that drive migration. The underlying molecular mechanisms for the function of Rho/ROCK pathway leading to the development and progression in scirrhous gastric carcinoma cells have not been defined. We investigated the role of the Rho/ROCK pathway in the adhesion and invasion of gastric carcinoma cells, using a human scirrhous gastric cancer cell line, OCUM-2MD3. ROCK inhibitor, Y27632 significantly increased the adhesion of OCUM-2MD3 cells to the extracellular metrix (ECM) protein matrigel, but had no effect on attachment to polylysine. Further examination using ECM components showed enhanced binding ability was obtained only in laminin, but not in fibronectin, Type I collagen, and Type IV collagen. Reverse transcriptional (RT)-PCR analysis revealed that integrin subunits α3-integrin was clearly up-regulated by treatment with Y-27632 in OCUM-2MD3 cells, reflecting the specificity of ECM protein showing high adhesiveness property of gastric carcinoma cells. ROCK inhibitor also enhanced the invasion of OCUM-2MD3 cells through matrigel. The fact that Y27632 up-regulated the expression of membrane-type 1 matrix metalloproteinase by RT-PCR suggested the possibility that increased invasion ability of OCUM-2MD3 cells was related to proteolytic activity of extracellular matrices. Time-lapse microscopy showed conversion of OCUM-2MD3 cells from elongated to more round morphology with bleb in the presence of Y27632, suggesting that inhibition of Rho/ROCK pathway undergo a so-called ‘amoeboid to mesenchymal’ transition. Taken together, these data suggests that Rho/ROCK regulate plasticity of metastatic gastric carcinoma via mesenchymal-amoeboid transition, leading to clarify the specific progression of scirrhous gastric carcinoma. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5118.

Synergistic antitumor effects of FGFR2 inhibitor with 5‐fluorouracil on scirrhous gastric carcinoma

Scirrhous gastric carcinoma (SGC) carries the highest mortality because of a frequent metastasis to lymph node (LN). S1, a 5-fluorouracil (5-FU) analog, is clinically available for gastric cancer at an advanced stage. Fibroblast growth factor receptor 2 (FGFR2) is required for the proliferation of SGC. The objective of this study is to clarify the benefit of a combination of S1 and kinase inhibitors including FGFR2 inhibitor Ki23057 in gastric cancer. OCUM-2MLN and KATO-III were derived from SGC. MKN-7 and MKN-74 were derived from non-SGC. MTT assay was used to examine the growth-inhibitory activity of 5 small-synthetic molecules including Ki23057, Sunitinib, Glivec, Lapatinib or SU11274, in cells cultured with 5-FU. Combination effects of 5-FU with Ki23057 on proliferation, apoptosis and mRNA expression were examined. S1 and/or Ki23057 were administered to murine models of SGC created by the orthotopic inoculation of OCUM-2MLN cells. Ki23057 at 100 nM significantly (p < 0.01) inhibited the proliferation and decreased the phosphorylation of FGFR2 in SGC cells, but not in non-SGC. Ki23057 showed synergistic antitumor effects for SGC cells in combination with 5-FU using CalcuSyn analysis, but Sunitinib, Glivec, Lapatinib and SU11274 did not. The combination of Ki23057 and 5-FU decreased DPD expression and increased apoptosis rates and p21 expression level of SGC cells. The combined administration of S1 and Ki23057 significantly (p < 0.05) decreased orthotopic tumors as well as LN metastasis more effectively than S1 alone. These findings suggested that the combined treatment with 5-FU and Ki23057 produced synergistic antitumor effects and is therapeutically promising for SGC treatment.

A novel K-samII/FGF-R2 autophosphorylation inhibitor is therapeutically useful for scirrhous gastric carcinoma with K-samII amplification

14070 Background: Scirrhous gastric carcinoma, a diffusely infiltrating also known as linitis plastica-type carcinoma, carries the highest mortality of all gastric cancers. Scirrhous carcinoma cells with amplification of the activated K-samII gene, which encodes fibroblast growth factor receptor type 2 (FGF-R2), have a growth advantage during tumor progression The poor prognosis carried by scirrhous gastric cancer is closely associated with amplification of the K-samII/FGF-R2, a tyrosine kinase growth factor receptor. Ki23057, a newly developed small molecule acting K-samII/FGF-R2 inhibitor, is a kinase inhibitor that competes with ATP for the binding site in the kinase, thus strongly blocking phosphorylation of FGF-R2. The aim of the current study is to clarify the possibility of molecular target therapy with Ki23057 for treating scirrhous gastric cancer. Methods: Five human gastric cancer cell lines were used. OCUM-2MD3 and OCUM-8 were derived from scirrhous carcinomas. MKN-7, MKN-45 and MKN-74 cells were derived from non-scirrhous carcinomas. In vitro effects of Ki23057 on cell growth were determined by calculating the number of cancer cells. The influences of Ki23057 on the MAP kinase and PI3 kinase signaling pathways and the apoptosis pathway in the gastric cancer cells were also examined. For in vivo experiments, the Ki23057 was administered orally to mouse models of peritoneal dissemination. Results: K-samII amplification was found in OCUM-2MD3 and OCUM-8 cells, but not in MKN-7, MKN-45, or MKN-74 cells. Ki23057 significantly inhibited the proliferation of scirrhous cancer cells, but not non- scirrhous gastric carcinoma cells. Ki23057 decreased phosphorylation of K-samII/FGF-R2, ERK and Akt, and increased apoptosis in scirrhous cancer lines. The oral Ki23057 administration significantly (p&lt;0.001) prolonged survival of mice with peritoneal dissemination following injection of OCUM-2MD3 scirrhous cancer cells. Conclusions: A novel K-samII/FGF-R2 phosphorylation inhibitor, Ki23057, appears therapeutically promising in scirrhous gastric carcinoma with K-samII amplification. No significant financial relationships to disclose.

Inhibitory effect of a selective cyclooxygenase inhibitor on the invasion‐stimulating activity of orthotopic fibroblasts for scirrhous gastric cancer cells

The cyclooxygenase (COX)-2 inhibitor has been reported to impede the progression of gastric cancer, but underlying mechanisms remain unclear. We therefore investigated the effect of a COX-2 inhibitor, JTE-522, on the ability of orthotopic fibroblasts to stimulate invasion of scirrhous gastric carcinoma cells. The human scirrhous gastric cancer cell lines OCUM-2D or OCUM-2M, and human gastric fibroblasts (NF-21) were cultured in the absence or presence of JTE-522 at various concentrations. Cancer cells were then assayed for invasiveness in vitro by invasion assay. The effect of prostaglandins (PG) on growth factor production in NF-21 cells was examined by ELISA. Finally, the effects of orally administrated JTE-522 on orthotopically transplanted tumors were examined in nude mice. NF-21 cells stimulated invasion by OCUM-2D cells, an effect suppressed by JTE-522 at 5 x 10(-6) M. Hepatocyte growth factor (HGF) and PGE2 production by NF-21 cells were suppressed by JTE-522 (P < 0.01). PGE2 stimulated HGF production by NF-21 cells in a dose-dependent manner. JTE-522 significantly suppressed orthotopic tumor growth and lymph node metastasis, and also decreased HGF expression by fibroblasts within the gastric tumor. In conclusion, we found that gastric fibroblasts stimulated invasiveness in scirrhous gastric cancer cells, whereas a selective COX-2 inhibitor inhibited this paracrine effect by decreasing fibroblast PGE2 production, resulting in downregulation of HGF production.

Establishment of two cell lines from human gastric scirrhous carcinoma that possess the potential to metastasize spontaneously in nude mice.

Few experimental studies have been conducted to clarify the mechanism of development of metastasis in scirrhous carcinoma of the stomach. In the present study, we attempted to establish gastric carcinoma cell lines by incubation of cancer cells collected from the body fluids of patients with gastric cancer. At the same time, xenografting of these cells to nude mice was performed. It was found that, of the gastric carcinoma cell lines thus established, two cell lines, designated as HSC-44PE and HSC-58, formed s.c. tumors with a high infiltrative potential (often invading the lymphatics around the cancer tissue) when implanted. Metastasis to the lymph nodes and lungs was observed in 20-40% of all the animals, indicating that the two cell lines are also capable of metastasizing spontaneously. Through repeated selection, i.e., repeated cycles of removal, culture, and implantation of the HSC cancer cells from metastatic lesions, we obtained 5 subclones of HSC-44PE and HSC-58 (designated as m2509, m2615, m2792, m2917, and m2691), which, when implanted orthotopically, exhibited the following characteristics as compared to the parent cells: (1) a higher percentage take (survival), similar frequency of metastasis, shorter time to metastasis (less than 100 days), and consistent metastasizing potential; (2) a relatively high frequency of metastasis to lymph nodes, including distant metastasis to axillary lymph nodes; (3) the potential to cause occasional bloody ascites; (4) enhanced expression of dysadherin, CD44, and other molecules. This is the first report of cultured scirrhous gastric carcinoma cells showing the potential for spontaneous metastasis.

A Rapid Immunohistologic Method for Determining the Limit of Cancer Invasion at the Surgical Margin of Scirrhous Carcinoma of the Stomach During Surgery

The authors used the monoclonal antibody (MAb) S202 as an adjunct for detection of scirrhous gastric carcinoma cells in cytomorphologic preparations of the resected stomach. Twenty-six samples of scirrhous gastric cancer were stained by the avidin-biotin complex technique on fixed frozen sections. MAb S202 was strongly reactive on all sections. In 12 cases, samples obtained from surgical margins were examined by a rapid immunostaining method. In one case, conventional cytologic findings were equivocal, whereas by the rapid immunostaining method single cells were stained darkly, indicating malignancy. Thus, immunohistochemical analysis using MAb S202 should be carried out to determine the limit of invasive carcinoma at the time of surgery.