Department of Orthopaedic Surgery, Faculty of Medicine, University of Yamanashi, Chuo, Japan.
Department of Orthopaedics, Vanderbilt University Medical Center, Nashville, TN, USA.
J Bone Miner Res. 2018 Nov;33(11):2048-2058. doi: 10.1002/jbmr.3537. Epub 2018 Jul 20.
Over the last three decades, the prognosis of osteosarcoma has remained unchanged; the prognosis for patients with lung metastasis is still poor, and the development of new treatments is urgently required. We previously showed that aggressive osteosarcoma cells express more tissue factor (TF) and demonstrate enhanced extrinsic pathway capacity. Furthermore, tumor growth can be suppressed with the anticoagulant low molecular weight heparin. However, the molecular mechanisms underlying TF regulation are still unclear. Here, we report that transforming growth factor-β (TGF-β) upregulates TF, which can occur via activated platelets. TF was found to be expressed on osteosarcoma cell surfaces, which mediated the production of Xa and thrombin. TF induction by TGF-β was observed in several osteosarcoma cells, and especially in MG 63 cells. Both TF expression by TGF-β and extrinsic pathway activity through TF were rapidly increased. This reaction was inhibited by a TGF-β type I receptor inhibitor and TGF-β neutralizing antibody. Although TGF-β was found to phosphorylate both Smad2 and Smad3, their roles were markedly disparate. Surprisingly, Smad2 knockdown resulted in no inhibitory effect, whereas Smad3 knockdown completely suppressed TGF-β-induced TF expression. Next, data suggested that platelets were the source of TGF-β. We confirmed that thrombin-activated platelets and osteosarcoma cells could release TGF-β, and that platelet-derived TGF-β could induce TF expression. These processes were also inhibited by a TGF-β type I receptor inhibitor and Smad3 knockdown. Moreover, CD42b, TF, TGF-β, Smad2/3, and p-Smad2/3 were also detected in a biopsy sample from an osteosarcoma patient. Collectively, these finding suggested that the interaction between osteosarcoma cells and platelets, via thrombin and TGF-β, results in a continuous cycle, and that anti-platelet or anti-TGF-β therapy could be a promising tool for disease treatment. © 2018 American Society for Bone and Mineral Research.
在过去的三十年中，骨肉瘤的预后一直没有改变；患有肺转移的患者的预后仍然很差，迫切需要开发新的治疗方法。我们之前表明，侵袭性骨肉瘤细胞表达更多的组织因子（TF），并表现出增强的外源性途径能力。此外，肿瘤生长可以用抗凝低分子量肝素抑制。然而，TF 调节的分子机制仍不清楚。在这里，我们报告转化生长因子-β（TGF-β）上调 TF，这可以通过激活的血小板发生。在骨肉瘤细胞表面发现 TF 表达，其介导 Xa 和凝血酶的产生。在几种骨肉瘤细胞中观察到 TGF-β诱导 TF，特别是在 MG63 细胞中。TGF-β诱导的 TF 表达和通过 TF 的外源性途径活性均迅速增加。该反应被 TGF-β 型 I 受体抑制剂和 TGF-β 中和抗体抑制。虽然发现 TGF-β磷酸化 Smad2 和 Smad3，但它们的作用明显不同。令人惊讶的是，Smad2 敲低没有抑制作用，而 Smad3 敲低完全抑制 TGF-β诱导的 TF 表达。接下来，数据表明血小板是 TGF-β的来源。我们证实，凝血酶激活的血小板和骨肉瘤细胞可以释放 TGF-β，血小板衍生的 TGF-β可以诱导 TF 表达。这些过程也被 TGF-β 型 I 受体抑制剂和 Smad3 敲低抑制。此外，在骨肉瘤患者的活检样本中还检测到 CD42b、TF、TGF-β、Smad2/3 和 p-Smad2/3。总之，这些发现表明，通过凝血酶和 TGF-β，骨肉瘤细胞与血小板之间的相互作用导致一个连续的循环，抗血小板或抗 TGF-β治疗可能是一种有前途的疾病治疗工具。
