Division of Hematology, Stanford University School of Medicine, Stanford, California, USA.
Veterans Affairs Palo Alto Health Care System, Palo Alto, California, USA.
J Thromb Haemost. 2022 May;20(5):1256-1270. doi: 10.1111/jth.15663. Epub 2022 Feb 16.
Osteopontin (OPN) is a multifunctional proinflammatory matricellular protein overexpressed in multiple human cancers and associated with tumor progression and metastases. Thrombin cleavage of OPN reveals a cryptic binding site for α β and α β integrins.
Thrombin cleavage-resistant OPN knock-in (OPN-KI) mice were generated and compared to OPN deficient mice (OPN-KO) and wild type (WT) mice in their ability to support growth of melanoma cells. Flow cytometry was used to analyze tumor infiltrating leukocytes.
OPN-KI mice engineered with a thrombin cleavage-resistant OPN had reduced B16 melanoma growth and fewer pulmonary metastases than WT mice. The tumor suppression phenotype of the OPN-KI mouse was identical to that observed in OPN-KO mice and was replicated in WT mice by pharmacologic inhibition of thrombin with dabigatran. Tumors isolated from OPN-KI mice had increased tumor-associated macrophages with an altered activation phenotype. Immunodeficient OPN-KI mice (NOG-OPN-KI) or macrophage-depleted OPN-KI mice did not exhibit the tumor suppression phenotype. As B16 cells do not express OPN, thrombin-cleaved fragments of host OPN suppress host antitumor immune response by functionally modulating the tumor-associated macrophages. YUMM3.1 cells, which express OPN, showed less tumor suppression in the OPN-KI and OPN-KO mice than B16 cells, but its growth was suppressed by dabigatran similar to B16 cells.
Thrombin cleavage of OPN, derived from the host and the tumor, initiates OPN's tumor-promoting activity in vivo.
骨桥蛋白（OPN）是一种多功能的促炎细胞外基质蛋白，在多种人类癌症中过度表达，与肿瘤进展和转移有关。凝血酶切割 OPN 揭示了一个隐藏的结合位点，用于 αβ 和 αβ 整合素。
生成了对凝血酶切割具有抗性的 OPN 敲入（OPN-KI）小鼠，并将其与 OPN 缺陷型（OPN-KO）小鼠和野生型（WT）小鼠进行比较，以研究它们支持黑色素瘤细胞生长的能力。使用流式细胞术分析肿瘤浸润的白细胞。
用对凝血酶切割具有抗性的 OPN 工程化的 OPN-KI 小鼠具有降低的 B16 黑色素瘤生长和更少的肺转移。与 WT 小鼠相比，OPN-KI 小鼠的肿瘤抑制表型与 OPN-KO 小鼠观察到的表型相同，并且通过用达比加群抑制凝血酶在 WT 小鼠中复制了该表型。从 OPN-KI 小鼠分离的肿瘤具有更多的肿瘤相关巨噬细胞，其激活表型发生改变。免疫缺陷型 OPN-KI 小鼠（NOG-OPN-KI）或巨噬细胞耗竭型 OPN-KI 小鼠未表现出肿瘤抑制表型。由于 B16 细胞不表达 OPN，凝血酶切割的宿主 OPN 片段通过功能调节肿瘤相关巨噬细胞来抑制宿主抗肿瘤免疫反应。表达 OPN 的 YUMM3.1 细胞在 OPN-KI 和 OPN-KO 小鼠中的肿瘤抑制作用低于 B16 细胞，但与 B16 细胞相似，其生长被达比加群抑制。
来自宿主和肿瘤的凝血酶切割 OPN 启动了 OPN 在体内的促肿瘤活性。
