1. Cathepsin K cleavage of SDF-1α inhibits its chemotactic activity towards glioblastoma stem-like cells.
- Author
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Hira VV, Verbovšek U, Breznik B, Srdič M, Novinec M, Kakar H, Wormer J, der Swaan BV, Lenarčič B, Juliano L, Mehta S, Van Noorden CJ, and Lah TT
- Subjects
- Amino Acid Sequence, Benzylamines, Cathepsin K genetics, Cell Line, Tumor, Chemokine CXCL12 chemistry, Chemokine CXCL12 genetics, Chemotaxis, Cyclams, Gene Expression, Heterocyclic Compounds pharmacology, Humans, Neoplastic Stem Cells pathology, Neuroglia pathology, Protein Binding, Protein Conformation, alpha-Helical, Protein Conformation, beta-Strand, Proteolysis, Receptors, CXCR genetics, Receptors, CXCR metabolism, Receptors, CXCR4 antagonists & inhibitors, Receptors, CXCR4 genetics, Stem Cell Niche genetics, Cathepsin K metabolism, Chemokine CXCL12 metabolism, Neoplastic Stem Cells metabolism, Neuroglia metabolism, Receptors, CXCR4 metabolism
- Abstract
Glioblastoma (GBM) is the most aggressive primary brain tumor with poor patient survival that is at least partly caused by malignant and therapy-resistant glioma stem-like cells (GSLCs) that are protected in GSLC niches. Previously, we have shown that the chemo-attractant stromal-derived factor-1α (SDF-1α), its C-X-C receptor type 4 (CXCR4) and the cysteine protease cathepsin K (CatK) are localized in GSLC niches in glioblastoma. Here, we investigated whether SDF-1α is a niche factor that through its interactions with CXCR4 and/or its second receptor CXCR7 on GSLCs facilitates their homing to niches. Furthermore, we aimed to prove that SDF-1α cleavage by CatK inactivates SDF-1α and inhibits the invasion of GSLCs. We performed mass spectrometric analysis of cleavage products of SDF-1α after proteolysis by CatK. We demonstrated that CatK cleaves SDF-1α at 3 sites in the N-terminus, which is the region of SDF-1α that binds to its receptors. Confocal imaging of human GBM tissue sections confirmed co-localization of SDF-1α and CatK in GSLC niches. In accordance, 2D and 3D invasion experiments using CXCR4/CXCR7-expressing GSLCs and GBM cells showed that SDF-1α had chemotactic activity whereas CatK cleavage products of SDF-1α did not. Besides, CXCR4 inhibitor plerixafor inhibited invasion of CXCR4/CXCR7-expressing GSLCs. In conclusion, CatK can cleave and inactivate SDF-1α. This implies that CatK activity facilitates migration of GSLCs out of niches. We propose that activation of CatK may be a promising strategy to prevent homing of GSLCs in niches and thus render these cells sensitive to chemotherapy and radiation., (Copyright © 2016 Elsevier B.V. All rights reserved.)
- Published
- 2017
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