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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 α4 β1 and α9 β1 integrins. Thrombin cleavage-resistant OPNR153A 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. © 2022 International Society on Thrombosis and Haemostasis.


Sameera Peraramelli, Qi Zhou, Qin Zhou, Bettina Wanko, Lei Zhao, Toshihiko Nishimura, Thomas H Leung, Seiya Mizuno, Mamoru Ito, Timothy Myles, Thomas M Stulnig, John Morser, Lawrence L K Leung. Thrombin cleavage of osteopontin initiates osteopontin's tumor-promoting activity. Journal of thrombosis and haemostasis : JTH. 2022 May;20(5):1256-1270

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PMID: 35108449

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