MicroRNAs Associated with Epithelial-Mesenchymal Transition Can Be Targeted to Inhibit Peritoneal Dissemination of Human Scirrhous Gastric Cancers.

Scirrhous gastric cancers grow rapidly, and frequently invade the peritoneum. Such peritoneal dissemination properties markedly reduce patient survival. Thus, an effective means for inhibiting peritoneal dissemination is urgently required. We previously established a cell line, HSC-58, from a scirrhous gastric cancer patient, and further successfully isolated a metastatic line, 58As9, in nude mice upon orthotopic inoculation. Using the lines, we examined the mechanism underlying peritoneal dissemination from the viewpoint of microRNA (miRNA) expression. miRNA array and qRT-PCR analysis showed that the expressions of epithelial-mesenchymal transition (EMT)-associated miRNAs such as miR-200c and miR-141 were significantly low in 58As9. Using 58As9 with stably overexpressing miR-200c, miR-141, or both, together with a luciferase reporter assay, we found that miR-200c targeted zinc finger E-box-binding homeobox 1 (ZEB1) and miR-141 targeted ZEB2. The overexpressed lines reversed the EMT status from mesenchymal to epithelial in 58As9, and significantly reduced the invasion activity and peritoneal dissemination for a significant prolongation of survival in the orthotopic tumor models in nude mice. EMT-associated miRNAs such as miR-200c and miR-141 and their target genes ZEB1/ZEB2 have good potential for antiperitoneal dissemination therapy in patients with scirrhous gastric cancers.

Takei Y ，Shen G ，Morita-Kondo A ，Hara T ，Mihara K ，Yanagihara K ... -  《-》

Long Noncoding RNA HOTAIR Promotes Epithelial-Mesenchymal Transition and Is a Suitable Target to Inhibit Peritoneal Dissemination in Human Scirrhous Gastric Cancers.

Scirrhous gastric cancer, which accounts for approximately 10% of all gastric cancers, often disseminates to the peritoneum, leading to intractable cases with poor prognosis. There is an urgent need for new treatment approaches for this difficult cancer. We previously established an original cell line, HSC-60, from a scirrhous gastric cancer patient and isolated a peritoneal-metastatic cell line, 60As6, in nude mice following orthotopic inoculations. In the present study, we focused on the expression of long noncoding ribonucleic acid (RNA) (lncRNA) in the cell lines and investigated the mechanism on peritoneal dissemination. We demonstrated that an lncRNA, HOX transcript antisense RNA (HOTAIR), is expressed significantly more highly in 60As6 than HSC-60 cells. Then, using both HOTAIR knockdown and overexpression experiments, we showed that high-level expression of HOTAIR promotes epithelial-mesenchymal transition (EMT) in 60As6 cells. By luciferase assay, we found that HOTAIR directly targets and binds to miR-217, and that miR-217 directly binds to Zinc finger E-box-binding homeobox 1 (ZEB1). The knockdown of HOTAIR in 60As6 cells significantly reduced the invasion activity and peritoneal dissemination - and significantly prolonged the survival - in the orthotopic tumor mouse model. An EMT-associated pathway (the HOTAIR-miR-217-ZEB1 axis) appears to inhibit peritoneal dissemination and could lead to a novel therapeutic strategy against scirrhous gastric cancer in humans.

Takei Y ，Hara T ，Suzuki A ，Mihara K ，Yanagihara K ... -  《-》

Expression level of microRNA-200c is associated with cell morphology in vitro and histological differentiation through regulation of ZEB1/2 and E-cadherin in gastric carcinoma.

Kurata A ，Yamada M ，Ohno SI ，Inoue S ，Hashimoto H ，Fujita K ，Takanashi M ，Kuroda M ... -  《-》

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.

Takei Y ，Takigahira M ，Mihara K ，Tarumi Y ，Yanagihara K ... -  《-》

Epigenetic modulation and repression of miR-200b by cancer-associated fibroblasts contribute to cancer invasion and peritoneal dissemination in gastric cancer.

Cancer-associated fibroblasts (CAFs) have recently been linked to the invasion and metastasis of gastric cancer. In addition, the microRNA (miR)-200 family plays a central role in the regulation of the epithelial-mesenchymal transition process during cancer metastasis, and aberrant DNA methylation is one of the key mechanisms underlying regulation of the miR-200 family. In this study, we clarified whether epigenetic changes of miR-200b by CAFs stimulate cancer invasion and peritoneal dissemination in gastric cancer. We evaluated the relationship between miR-200b and CAFs using a coculture model. In addition, we established a peritoneal metastasis mouse model and investigated the expression and methylation status of miR-200b. We also investigated the expression and methylation status of miR-200b and CAFs expression in primary gastric cancer samples. CAFs (CAF-37 and CAF-50) contributed to epigenetic changes of miR-200b, reduced miR-200b expression and promoted tumor invasion and migration in NUGC3 and OCUM-2M cells in coculture. In the model mice, epigenetic changes of miR-200b were observed in the inoculated high-frequency peritoneal dissemination cells. In the 173 gastric cancer samples, the low miR-200b expression group demonstrated a significantly poorer prognosis compared with the high miR-200b expression group and was associated with peritoneal metastasis. In addition, downregulation of miR-200b in cancer cells was significantly correlated with alpha-smooth muscle actin expression. Our data provide evidence that CAFs reduce miR-200b expression and promote tumor invasion through epigenetic changes of miR-200b in gastric cancer. Thus, CAFs might be a therapeutic target for inhibition of gastric cancer.

Kurashige J ，Mima K ，Sawada G ，Takahashi Y ，Eguchi H ，Sugimachi K ，Mori M ，Yanagihara K ，Yashiro M ，Hirakawa K ，Baba H ，Mimori K ... -  《-》