Degradation of Extracellular Matrix Protein Tenascin-C by Cathepsin B: An Interaction Involved in the Progression of Gliomas

Abstract

Degradation of extracellular matrix proteins by proteases such as the cysteine protease cathepsin B is critical to malignant progression. We have established that procathepsin B presents on the surface of tumor cells through its interaction with the annexin II tetramer [Mai et al., J. Biol. Chem. 275 (2000), 12806 12812]. Cathepsin B activity can also be detected on the tumor cell surface and in their culture medium. Interestingly, the annexin II tetramer also interacts with extracellular matrix proteins, such as collagen I, fibrin and tenascinC. Both cathepsin B and tenascinC are expressed at high levels in malignant tumors, especially at the invasive edges of tumors, and are implicated in tumor angiogenesis. In this study, we report that tenascinC can be degraded by cathepsin B in vitro. We demonstrate by immunohistochemistry that both cathepsin B and tenascinC are expressed highly in malignant anaplastic astrocytomas and glioblastomas as compared to normal brain tissues. Interestingly, cathepsin B and tenascinC were also detected in association with tumor neovessels. We suggest that interactions between cathepsin B and tenascinC are involved in the progression of gliomas including the angiogenesis that is a hallmark of anaplastic astrocytomas.