Several clinical studies have reported increased expression of osteopontin (OPN) in various types of human cancer, including gastric cancer. However, the precise mechanisms underlying tumor development remain unclear. In the present study, we investigated the pathogenic roles of OPN in Helicobacter pylori-induced gastric cancer development. Wild-type (WT) and OPN knockout (KO) mice were treated with N-methyl-N-nitrosourea (MNU) and infected with H.pylori. Mice were killed 50 weeks after treatment, and stomach tissues were assessed by histopathological examination, immunohistochemistry, quantitative real-time RT-PCR and western blotting. To clarify the carcinogenic effects of OPN, we also conducted an in vitro study using AGS human gastric cancer cell line and THP-1 human monocytic cell line. The overall incidence of gastric tumors was significantly decreased in OPN KO mice compared with WT mice. Apoptotic cell death was significantly enhanced in OPN KO mice and was accompanied by upregulation of signal transducer and activator of transcription 1 (STAT1) and inducible nitric oxide synthase (iNOS). In vitro study, OPN suppression also caused STAT1 upregulation and iNOS overexpression in AGS and THP-1 cells, which resulted in apoptosis of AGS cells. In addition, a negative correlation was clearly identified between expression of OPN and iNOS in human gastric cancer tissues. Our data demonstrate that loss of OPN decreases H.pylori-induced gastric carcinogenesis by suppressing proinflammatory immune response and augmenting STAT1 and iNOS-mediated apoptosis of gastric epithelial cells. An important implication of these findings is that OPN actually contributes to the development of gastric cancer.

The polymerase of avian influenza A virus (AIV) is a heterotrimer composed of PB2, PB1, and PA. PB2 plays a role in overcoming the host barrier; however, the genetic prerequisites for avian PB2 to acquire mammalian pathogenic mutations have not been well elucidated. Previously, we identified a prototypic avian PB2 that conferred non-replicative and non-pathogenic traits to a PR8-derived recombinant virus when it was used to infect mice. Here, we demonstrated that key amino acid mutations (I66M, I109V, and I133V, collectively referred to as MVV) of this prototypic avian PB2 increase the replication efficiency of recombinant PR8 virus carrying the mutated PB2 in both avian and mammalian hosts. The MVV mutations caused no weight loss in mice, but they did allow replication in infected lungs, and the viruses acquired fatal mammalian pathogenic mutations such as Q591R/K, E627K, or D701N in the infected lungs. The MVV mutations are located at the interfaces of the trimer and are predicted to increase the strength of this structure. Thus, gaining MVV mutations might be the first step for AIV to acquire mammalian pathogenicity. These results provide new insights into the evolution of AIV in birds and mammals.

Previous clinical reports have found elevated osteopontin (OPN) levels in tumor tissues to be indicative of greater malignancy in human hepatocellular carcinoma (HCC). However, the role of OPN on carcinogenesis and its underlying mechanism remain unclear. In the present study, we investigated the oncogenic role of OPN in diethylnitrosamine (DEN)-induced hepatic carcinogenesis in mice. The overall incidence of hepatic tumors at 36 weeks was significantly lower in OPN knockout (KO) mice than in wild-type (WT) mice. Apoptosis was significantly enhanced in OPN KO mice, and was accompanied by the downregulation of epidermal growth factor receptor (EGFR). In the in vitro study, OPN suppression also led to lower mRNA and protein levels of EGFR associated with the downregulation of c-Jun in Hep3B and Huh7 human HCC cells lines, which resulted in increased apoptotic cell death in both cell lines. Moreover, a positive correlation was clearly identified between the expression of OPN and EGFR in human HCC tissues. These data demonstrate that the OPN deficiency reduced the incidence of chemically induced HCC by suppressing EGFR-mediated anti-apoptotic signaling. An important implication of our findings is that OPN positively contributes to hepatic carcinogenesis.

Hepatocutaneous syndrome (HS) is an uncommon skin disorder that occurs in conjunction with liver disease and is diagnosed based on decreased plasma concentrations of amino acids and the histopathology of skin lesions. The survival period generally is <6 months. A 10‐year‐old castrated male Maltese dog was presented for evaluation of lethargy, polyuria, polydipsia, and skin lesions including alopecia, erythema, and crusts. Based on increased liver enzyme activity, low plasma amino acid concentrations, and findings from liver cytology and skin biopsy, the dog was diagnosed with HS. In addition to administration of antioxidants, hepatoprotective agents, and amino acids IV, allogenic adipose tissue‐derived mesenchymal stem cells were infused 46 times over a 30‐month period: 8 times directly into the liver parenchyma guided by ultrasonography and the remainder of the times into peripheral veins. After commencing stem cell therapy, the dog's hair re‐grew and the skin lesions disappeared or became smaller. During ongoing management, the patient suddenly presented with anorexia and uncontrolled vomiting, and severe azotemia was observed. The dog died despite intensive care. On necropsy, severe liver fibrosis and superficial necrolytic dermatitis were observed. The dog survived for 32 months after diagnosis. A combination of amino acid and stem cell therapy may be beneficial for patients with HS.

Our study showed that OPN is essential for maintaining the tight junction complex by allowing occludin to localize at tight junctions. This could constitute additional evidence that OPN plays a crucial role in intestinal mucosal protection.