Verdinexor (KPT‐335) is a novel orally bioavailable selective inhibitor of nuclear export (SINE) compound that inhibits the function of the nuclear export protein Exportin 1 (XPO1/CRM1). In the present study, we sought to characterize the expression of XPO1 in primary canine osteosarcoma (OS) tumour samples, OS cell lines and normal osteoblasts and evaluate the in vitro activity of verdinexor alone or in combination with doxorubicin. Canine OS cell lines and a subset of primary OS tumours showed increased XPO1 transcript and protein expression as compared with normal canine osteoblast cells. All canine OS cell lines exhibited dose‐dependent growth inhibition and increased caspase 3,7 activity in response to low nanomolar concentrations of verdinexor (IC₅₀ concentrations ranging from 21 to 74 nM). Notably, growth inhibition of normal canine osteoblast cell lines treated with verdinexor was observed at high micromolar concentrations (IC₅₀ = 21 μM). The combination of verdinexor and doxorubicin resulted in potent inhibition of cell viability and demonstrated synergetic activity in three canine OS cell lines. Concordantly, OS cell lines showed increased γH2A.X foci following treatment with doxorubicin and recovery in verdinexor compared with cells treated with doxorubicin and recovered in normal media for 24 hours. These findings demonstrate that verdinexor has biologic activity against canine OS cell lines at physiologically relevant doses and suggest that XPO1 inhibition in combination with standard doxorubicin treatment offers promising potential for chemotherapeutic intervention in canine OS.

中文翻译：

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核输出选择性抑制剂 (SINE) verdinexor 对犬骨肉瘤细胞系表现出生物活性

Verdinexor (KPT-335) 是一种新型口服生物可利用的核输出选择性抑制剂 (SINE) 化合物，可抑制核输出蛋白 Exportin 1 (XPO1/CRM1) 的功能。在本研究中，我们试图表征 XPO1 在原发性犬骨肉瘤 (OS) 肿瘤样本、OS 细胞系和正常成骨细胞中的表达，并评估单独使用 verdinexor 或与多柔比星联合使用的体外活性。与正常犬成骨细胞相比，犬 OS 细胞系和一部分原发性 OS 肿瘤显示出增加的 XPO1 转录物和蛋白质表达。所有犬类 OS 细胞系均表现出剂量依赖性生长抑制和半胱天冬酶 3,7 活性增加，以响应低纳摩尔浓度的 verdinexor (IC ₅₀浓度范围为 21 至 74 nM）。值得注意的是，在高微摩尔浓度下观察到用 verdinexor 处理的正常犬成骨细胞系的生长抑制 (IC ₅₀ = 21微米）。verdinexor 和多柔比星的组合可有效抑制细胞活力，并在三种犬 OS 细胞系中表现出协同活性。一致地，与用阿霉素处理并在正常培养基中恢复 24 小时的细胞相比，在用阿霉素处理和在 verdinexor 中恢复后，OS 细胞系显示出增加的 γH2A.X 病灶。这些发现表明，verdinexor 在生理相关剂量下对犬 OS 细胞系具有生物活性，并表明 XPO1 抑制与标准阿霉素治疗相结合为犬 OS 的化学治疗干预提供了有希望的潜力。