Requisite role of vasohibin‐2 in spontaneous gastric cancer formation and accumulation of cancer‐associated fibroblasts

<jats:p>The vasohibin (<jats:styled-content style="fixed-case">VASH</jats:styled-content>) family consists of two genes, <jats:italic><jats:styled-content style="fixed-case">VASH</jats:styled-content>1</jats:italic> and <jats:italic><jats:styled-content style="fixed-case">VASH</jats:styled-content>2</jats:italic>. <jats:styled-content style="fixed-case">VASH</jats:styled-content>1 is mainly expressed in vascular endothelial cells and suppresses angiogenesis in an autocrine manner, whereas <jats:styled-content style="fixed-case">VASH</jats:styled-content>2 is mainly expressed in cancer cells and exhibits pro‐angiogenic activity. Employing adenomatous polyposis coli gene mutant mice, we recently reported on the role of Vash2 in the spontaneous formation of intestinal tumors. In this study, we used K19‐Wnt1/C2mE (<jats:italic>Gan</jats:italic>) mice and examined the role of Vash2 in spontaneous gastric cancer formation. <jats:italic>Gan</jats:italic> mice spontaneously develop gastric tumors by activation of Wnt and prostaglandin E2 signaling pathways in gastric mucosa after 30 weeks of age. Expression of <jats:italic>Vash2 </jats:italic><jats:styled-content style="fixed-case">mRNA</jats:styled-content> was significantly increased in gastric tumor tissues compared with normal stomach tissues. When <jats:italic>Gan</jats:italic> mice were crossed with the <jats:italic>Vash2</jats:italic>‐deficient (<jats:italic>Vash2</jats:italic><jats:sup><jats:italic>LacZ/LacZ</jats:italic></jats:sup>) strain, gastric cancer formation was significantly suppressed in <jats:italic>Vash2</jats:italic><jats:sup><jats:italic>LacZ/LacZ</jats:italic></jats:sup> <jats:italic>Gan</jats:italic> mice. Normal composition of gastric mucosa was partially maintained in <jats:italic>Vash2</jats:italic><jats:sup><jats:italic>LacZ/LacZ</jats:italic></jats:sup> <jats:italic>Gan</jats:italic> mice. Knockout of <jats:italic>Vash2</jats:italic> caused minimal reduction of tumor angiogenesis but a significant decrease in cancer‐associated fibroblasts (<jats:styled-content style="fixed-case">CAF</jats:styled-content>) in tumor stroma. <jats:styled-content style="fixed-case">DNA</jats:styled-content> microarray analysis and real‐time <jats:styled-content style="fixed-case">RT</jats:styled-content>‐<jats:styled-content style="fixed-case">PCR</jats:styled-content> showed that <jats:styled-content style="fixed-case">mRNA</jats:styled-content> levels of epiregulin (Ereg) and interleukin‐11 (Il11) were significantly downregulated in gastric tumors of <jats:italic>Vash2</jats:italic><jats:sup><jats:italic>L</jats:italic>acZ/LacZ</jats:sup> <jats:italic>Gan</jats:italic> mice. Furthermore, conditioned medium of gastric cancer cells stimulated migration of and α‐smooth muscle actin expression in fibroblasts, whereas conditioned medium of <jats:styled-content style="fixed-case">VASH</jats:styled-content>2 knockdown cells attenuated these effects <jats:italic>in vitro</jats:italic>. These results suggest that <jats:styled-content style="fixed-case">VASH</jats:styled-content>2 plays an important role in gastric tumor progression via the accumulation of <jats:styled-content style="fixed-case">CAF</jats:styled-content> accompanying upregulation of <jats:styled-content style="fixed-case">EREG</jats:styled-content> and <jats:styled-content style="fixed-case">IL</jats:styled-content>‐11 expression.</jats:p>