Mizuho Nakayama

A Novel Prostacyclin Agonist Protects against Airway Hyperresponsiveness and Remodeling in Mice

Airway remodeling in bronchial asthma results from chronic, persistent airway inflammation. The effects of the reversal of airway remodeling by drug interventions remain to be elucidated. We investigated the effects of ONO-1301, a novel prostacyclin agonist with thromboxane inhibitory activity, on the prevention and reversibility of airway remodeling in an experimental chronic asthma model. Mice sensitized and challenged to ovalbumin (OVA) three times a week for 5 consecutive weeks were administered ONO-1301 or vehicle twice a day from the fourth week of OVA challenges. Twenty-four hours after the final OVA challenge, airway hyperresponsiveness (AHR) was assessed, and bronchoalveolar lavage was performed. Lung specimens were excised for staining to detect goblet-cell metaplasia, airway smooth muscle, and submucosal fibrosis. Mice administered ONO-1301 showed limited increases in AHR compared with mice administered the vehicle. The histological findings of airway remodeling were improved in ONO-1301-treated mice compared with vehicle-treated mice. Presumably, these therapeutic effects of ONO-1301 are attributable to the up-regulation of production of hepatocyte growth factor (HGF) in lung tissue, because the neutralization of HGF by antibodies prevented the effects of ONO-1301 on AHR and airway remodeling. Mice administered ONO-1301 showed similar levels of AHR and airway remodeling as mice administered montelukast, a cysteinyl-leukotriene-1 receptor antagonist, and lower levels were observed in mice administered dexamethasone. These data suggest that ONO-1301 exerts the effect of reversing airway remodeling, at least in part through an elevation of HGF in the lungs, and may be effective as an anti-remodeling drug in the treatment of asthma.

Suppression of acute hepatic injury by a synthetic prostacyclin agonist through hepatocyte growth factor expression

Previous studies have demonstrated that mice disrupted with the cyclooxygenase-2 gene showed much more severe liver damage compared with wild-type mice after liver injury, and prostaglandins (PGs) such as PGE(1/2) and PGI(2) have decreased hepatic injury, but the mechanisms by which prostaglandins exhibit protective action on the liver have yet to be addressed. In the present study, we investigated the mechanism of the protective action of PGI(2) using the synthetic IP receptor agonist ONO-1301. In primary cultures of hepatocytes and nonparenchymal liver cells, ONO-1301 did not show protective action directly on hepatocytes, whereas it stimulated expression of hepatocyte growth factor (HGF) in nonparenchymal liver cells. In mice, peroral administration of ONO-1301 increased hepatic gene expression and protein levels of HGF. Injections of CCl4 induced acute liver injury in mice, but the onset of acute liver injury was strongly suppressed by administration of ONO-1301. The increases in serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) by CCl4 were suppressed by 10 mg/kg ONO-1301 to 39.4 and 33.6%, respectively. When neutralizing antibody against HGF was administered with ONO-1301 and CCl4, the decreases by ONO-1301 in serum ALT and AST, apoptotic liver cells, and expansion of necrotic areas in liver tissue were strongly reversed by neutralization of endogenous HGF. These results indicate that ONO-1301 increases expression of HGF and that hepatoprotective action of ONO-1301 in CCl4-induced liver injury may be attributable to its activity to induce expression of HGF, at least in part. The potential for involvement of HGF-Met-mediated signaling in the hepatotrophic action of endogenous prostaglandins generated by injury-dependent cyclooxygenase-2 induction is considerable.

Met/HGF receptor activation is regulated by juxtamembrane Ser985 phosphorylation in hepatocytes

Met/hepatocyte growth factor (HGF) receptor plays a definitive role in hepatocyte proliferation and liver regeneration. Phosphorylation of Ser985 in Met (Met-Ser985) down regulate tyrosine phosphorylation and activation of Met. However, mechanism of Met inactivation by Met-Ser985 phosphorylation and its biological significance on hepatocyte proliferation and liver regeneration are not well known. Here, we investigated biological role of Met-Ser985 phosphorylation in hepatocytes and liver. In primary cultured hepatocytes, HGF-dependent Met activation and mitogenesis were suppressed when Met-Ser985 was phosphorylated. Cell surface Met was decreased upon Met-Ser985 phosphorylation through endocytosis, suggesting a mechanism by which Met activation could be suppressed. In mice, HGF induced proliferation of hepatocyte in injured livers, but not in non-injured livers. Met-Ser985 phosphorylation was decreased after liver injury and associated with Met tyrosine phosphorylation/activation during liver regeneration. These results indicate that Met activation is regulated reciprocally to Met-Ser985 phosphorylation in the primary cultured hepatocytes and the liver following injury. Our study suggests that the phosphorylation of Met-Ser985 in hepatocytes plays a regulatory role in Met activation in response to quiescence, injury, and regeneration.

A synthetic prostacyclin agonist with thromboxane synthase inhibitory activity, ONO-1301, protects myocardium from ischemia/reperfusion injury☆

ONO-1301, a synthetic prostacyclin agonist with thromboxane synthase inhibitory activity, promotes the production of hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF) by various cell types. Here, we evaluated the therapeutic efficacy of ONO-1301 in rats with ischemia/reperfusion injury. Ligation of the left anterior descending arteries was performed in 10-week-old Wistar rats, and released 30 min later. A slow-release form of ONO-1301 was administered subcutaneously at 3h and 3 weeks after reperfusion injury. Hemodynamic parameters were significantly improved in the ONO-1301 group. Histological analysis revealed that ONO-1301 suppressed ischemic and fibrotic changes in the myocardium (ischemic area, control group: 58.6 ± 8.7% vs. ONO-1301 group: 44.4 ± 5.8%, fibrotic area, 33.5 ± 5.9% vs. 22.3 ± 6.2%, P<0.05, respectively), and enhanced neovascularization in the border zone. HGF expression was up-regulated by ONO-1301. Double-immunostaining revealed that myofibroblasts in the border zone of ischemic myocardium mainly expressed HGF. Our findings suggest that ONO-1301 might have therapeutic potential in treating ischemic heart disease.

Beneficial effect of a synthetic prostacyclin agonist, ONO-1301, in rat autoimmune myocarditis model.

Injury to the heart can result in cardiomyocyte hypertrophy, fibrosis, and cell death. Myocarditis sometimes progresses to dilated cardiomyopathy. We previously reported that ONO-1301, a synthetic prostacyclin agonist with thromboxane-synthase inhibitory activity, promotes production of hepatocyte growth factor (HGF) from various cell types and ameliorates ischemia-induced left ventricle dysfunction in the mouse, rat and pig. Here, we investigated the therapeutic efficacy of ONO-1301 in a rat model of myosin-induced experimental autoimmune myocarditis, in which the heart transits from an acute inflammatory phase to a chronic dilated cardiomyopathy phase. Four weeks after myosin injection to Lewis rats, ONO-1301 (6 mg/kg/day) was orally administered for 4 weeks (ONO-1301 group). Hemodynamic parameters and plasma brain natriuretic peptide (BNP) level were significantly improved by ONO-1301. Histological analysis revealed that capillary density in the myocardium was significantly increased by ONO-1301. ONO-1301 increased circulating endothelial progenitor cells (EPC) as determined by FACS analysis. These beneficial effects of ONO-1301 were partially abrogated by a neutralizing anti-HGF antibody (8 mg/kg/dose). These findings indicate beneficial effects of ONO-1301 in a rat experimental autoimmune myocarditis model.

Intestinal cancer progression by mutant p53 through the acquisition of invasiveness associated with complex glandular formation

Tumor suppressor TP53 is frequently mutated in colorectal cancer (CRC), and most mutations are missense type. Although gain-of-functions by mutant p53 have been demonstrated experimentally, the precise mechanism for malignant progression in in vivo tumors remains unsolved. We generated ApcΔ716 Trp53LSL•R270H villin-CreER compound mice, in which mutant p53R270H was expressed in the intestinal epithelia upon tamoxifen treatment, and examined the intestinal tumor phenotypes and tumor-derived organoids. Mutant Trp53R270H, but not Trp53-null mutation accelerated submucosal invasion with generation of desmoplastic microenvironment. The nuclear accumulation of p53 was evident in ApcΔ716 Trp53R270H/R270H homozygous tumors like human CRC. Although p53 was distributed to the cytoplasm in ApcΔ716 Trp53+/R270H heterozygous tumors, it accumulated in the nuclei at the invasion front, suggesting a regulation mechanism for p53 localization by the microenvironment. Importantly, mutant p53 induced drastic morphological changes in the tumor organoids to complex glandular structures, which was associated with the acquisition of invasiveness. Consistently, the branching scores of human CRC that carry TP53 mutations at codon 273 significantly increased in comparison with those of TP53 wild-type tumors. Moreover, allografted ApcΔ716 Trp53R270H/R270H organoid tumors showed a malignant histology with an increased number of myofibroblasts in the stroma. These results indicate that nuclear-accumulated mutant p53R270H induces malignant progression of intestinal tumors through complex tumor gland formation and acquisition of invasiveness. Furthermore, RNA sequencing analyses revealed global gene upregulation by mutant p53R270H, which was associated with the activation of inflammatory and innate immune pathways. Accordingly, it is possible that mutant p53R270H induces CRC progression, not only by a cell intrinsic mechanism, but also by the generation or activation of the microenvironment, which may synergistically contribute to the acceleration of submucosal invasion. Therefore, the present study indicates that nuclear-accumulated mutant p53R270H is a potential therapeutic target for the treatment of advanced CRCs.

Combined Mutation of Apc, Kras, and Tgfbr2 Effectively Drives Metastasis of Intestinal Cancer

Colorectal cancer is driven by the accumulation of driver mutations, but the contributions of specific mutations to different steps in malignant progression are not fully understood. In this study, we generated mouse models harboring different combinations of key colorectal cancer driver mutations (Apc, Kras, Tgfbr2, Trp53, Fbxw7) in intestinal epithelial cells to comprehensively investigate their roles in the development of primary tumors and metastases. ApcΔ716 mutation caused intestinal adenomas and combination with Trp53R270H mutation or Tgfbr2 deletion induced submucosal invasion. The addition of KrasG12D mutation yielded epithelial-mesenchymal transition (EMT)-like morphology and lymph vessel intravasation of the invasive tumors. In contrast, combinations of ApcΔ716 with KrasG12D and Fbxw7 mutation were insufficient for submucosal invasion, but still induced EMT-like histology. Studies using tumor-derived organoids showed that KrasG12D was critical for liver metastasis following splenic transplantation, when this mutation was combined with either ApcΔ716 plus Trp53R270H or Tgfbr2 deletion, with the highest incidence of metastasis displayed by tumors with a ApcΔ716 KrasG12D Tgfbr2-/- genotype. RNA sequencing analysis of tumor organoids defined distinct gene expression profiles characteristic for the respective combinations of driver mutations, with upregulated genes in ApcΔ716 KrasG12D Tgfbr2-/- tumors found to be similarly upregulated in specimens of human metastatic colorectal cancer. Our results show how activation of Wnt and Kras with suppression of TGFβ signaling in intestinal epithelial cells is sufficient for colorectal cancer metastasis, with possible implications for the development of metastasis prevention strategies.Significance: These findings illuminate how key driver mutations in colon cancer cooperate to drive the development of metastatic disease, with potential implications for the development of suitable prevention strategies. Cancer Res; 78(5); 1334-46. ©2017 AACR.

The Role of Inflammatory Responses in Mouse Gastric Tumorigenesis

It has been established that chronic inflammation plays an important role in cancer development. The expression of cyclooxygenase-2 (COX-2), a rate-limiting enzyme for prostaglandin biosynthesis, is induced in most cancer tissues and plays a key role in tumorigenesis. Helicobacter pylori infection causes atrophic gastritis, which is associated with the induction of COX-2 expression and its downstream product, prostaglandin E2 (PGE2), biosynthesis. Transgenic mice expressing COX-2 and microsomal prostaglandin E synthase-1 (mPGES-1) in the gastric mucosa show the generation of an inflammatory microenvironment via the activation of the COX-2/PGE2 pathway. Notably, simultaneous activation of canonical Wnt signaling and the COX-2/PGE2 pathway causes intestinal-type gastric tumor development, although Wnt activation alone is not sufficient for tumor formation. These results suggest that H. pylori infection-associated chronic inflammation contributes to gastric tumorigenesis through activation of the COX-2/PGE2 pathway. Using a gastric tumor mouse model (Gan mice), we found that the inflammatory microenvironment induces the activation of epidermal growth factor receptor (EGFR) signaling and promotes canonical Wnt signaling. Moreover, infiltrated macrophages express tumor necrosis factor-α (TNF-α) in gastric tumors, which plays an important role in tumor promotion through the induction of NADPH oxidase organizer 1 (NOXO1) expression. NOXO1 contributes to the production of reactive oxygen species (ROS) by the NOX1 complex, which is thought to be important for the maintenance of stem cell properties. These studies indicate that chronic inflammation promotes gastric tumorigenesis through a variety of mechanisms. Accordingly, targeting an inflammatory microenvironment should be an effective therapeutic or preventive strategy for gastric cancer.