Thrombin cleavage of osteopontin initiates osteopontin's tumor-promoting activity

J Thromb Haemost. 2022 May;20(5):1256-1270. doi: 10.1111/jth.15663. Epub 2022 Feb 16.


Background: 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.

Methods: 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.

Results: 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.

Conclusions: Thrombin cleavage of OPN, derived from the host and the tumor, initiates OPN's tumor-promoting activity in vivo.

Keywords: B16 melanoma; metastasis; osteopontin; thrombin inhibitor; tumor-associated macrophages.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Adhesion / genetics
  • Dabigatran
  • Humans
  • Melanoma, Experimental*
  • Mice
  • Osteopontin / chemistry
  • Osteopontin / genetics
  • Thrombin* / metabolism


  • Osteopontin
  • Thrombin
  • Dabigatran