Canine osteosarcoma (OSA) is the most common primary malignant bone tumour in dogs, and it has a high metastatic rate and poor prognosis. Toceranib phosphate (TOC; Palladia, Zoetis) is a veterinary tyrosine kinase inhibitor that selectively inhibits VEGFR‐2, PDGFRs and c‐Kit, but its efficacy is not yet fully understood in the treatment of canine OSA. Here, we evaluated the functional effects of TOC on six OSA cell lines by transwell, wound healing and colony formation assays. Subsequently, two cell lines (Wall and Penny) were selected and were inoculated in mice by intrafemoral injection to develop an orthotopic xenograft model of canine OSA. For each cell line, 30 mice were xenografted; half of them were used as controls, and the other half were treated with TOC at 40 mg/kg body weight for 20 days. TOC inhibited cell growth of all cell lines, but reduced invasion and migration was only observed in Penny and Wall cell lines. In mice engrafted with Penny cells and subjected to TOC treatment, decreased tumour growth was observed, and PDGFRs and c‐Kit mRNA were downregulated. Immunohistochemical analyses demonstrated a significant reduction of Ki67 staining in treated mice when compared to controls. The results obtained here demonstrate that TOC is able to slightly inhibit cell growth in vitro, while its effect is evident only in a Penny cell xenograft model, in which TOC significantly reduced tumour size and the Ki67 index without modifying apoptosis markers.

中文翻译：

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磷酸妥拉尼布对犬骨肉瘤细胞系和异种移植原位模型的体外和体内作用

犬骨肉瘤（OSA）是犬中最常见的原发性恶性骨肿瘤，其转移率高且预后差。磷酸Toceranib（TOC; Palladia，Zoetis）是一种兽用酪氨酸激酶抑制剂，可选择性抑制VEGFR-2，PDGFR和c-Kit，但在犬OSA的治疗中尚未完全了解其功效。在这里，我们通过transwell，伤口愈合和集落形成分析评估了TOC对6种OSA细胞系的功能作用。随后，选择两种细胞系（Wall和Penny），并通过股内注射在小鼠中接种以建立犬OSA的原位异种移植模型。对于每种细胞系，将30只小鼠异种移植。其中一半用作对照，另一半以40 mg / kg体重的TOC处理20天。TOC抑制所有细胞系的细胞生长，但仅在Penny和Wall细胞系中观察到侵袭和迁移减少。在移植了Penny细胞并经过TOC处理的小鼠中，观察到肿瘤生长下降，并且PDGFR和c-Kit mRNA下调。免疫组织化学分析显示，与对照组相比，治疗小鼠的Ki67染色明显降低。此处获得的结果表明，TOC能够在体外略微抑制细胞生长，而其作用仅在Penny细胞异种移植模型中可见，其中TOC显着减小了肿瘤大小和Ki67指数，而没有改变细胞凋亡标记。免疫组织化学分析显示，与对照组相比，治疗小鼠的Ki67染色明显降低。此处获得的结果表明，TOC能够在体外略微抑制细胞生长，而其作用仅在Penny细胞异种移植模型中可见，其中TOC显着减小了肿瘤大小和Ki67指数，而没有改变细胞凋亡标记。免疫组织化学分析表明，与对照组相比，治疗小鼠的Ki67染色明显降低。此处获得的结果表明，TOC能够在体外略微抑制细胞生长，而其作用仅在Penny细胞异种移植模型中可见，其中TOC显着减小了肿瘤大小和Ki67指数，而没有改变细胞凋亡标记。