AUTHOR=Rahman Rosanna M. A. , van Schaijik Bede , Brasch Helen D. , Marsh Reginald W. , Wickremesekera Agadha C. , Johnson Reuben , Woon Kelvin , Tan Swee T. , Itinteang Tinte 

TITLE=Expression of Cathepsins B, D, and G in WHO Grade I Meningioma

JOURNAL=Frontiers in Surgery

VOLUME=6

YEAR=2019

URL=https://www.frontiersin.org/journals/surgery/articles/10.3389/fsurg.2019.00006

DOI=10.3389/fsurg.2019.00006

ISSN=2296-875X

ABSTRACT=<p><bold>Aim:</bold> We have recently demonstrated the presence of putative tumor stem cells (TSCs) in World Health Organization (WHO) grade I meningioma (MG) localized to the microvessels, which expresses components of the renin-angiotensin system (RAS). The RAS is known to be dysregulated and promotes tumorigenesis in many cancer types, including glioblastoma. Cathepsins B, D, and G are isoenzymes that catalyze the production of angiotensin peptides, hence providing bypass loops for the RAS. This study investigated the expression of cathepsins B, D, and G in WHO grade I MG in relation to the putative TSC population we have previously demonstrated.</p><p><bold>Methods:</bold> 3,3-Diaminobenzidine (DAB) immunohistochemical (IHC) staining with antibodies for cathepsins B, D, and G was performed on WHO grade I MG tissue samples from 10 patients. Three of the MG samples subjected to DAB IHC staining underwent immunofluorescence (IF) IHC staining to investigate co-expression of each of these cathepsins using combinations of smooth muscle actin (SMA) and embryonic stem cell marker OCT4. NanoString mRNA expression (<italic>n</italic> = 6) and Western blotting (WB; <italic>n</italic> = 5) analyses, and enzyme activity assays (EAAs; <italic>n</italic> = 3), were performed on snap-frozen WHO grade I MG tissue samples to confirm transcriptional activation, protein expression, and functional activity of these proteins, respectively.</p><p><bold>Results:</bold> DAB IHC staining demonstrated expression of cathepsins B, D, and G in all 10 MG samples. NanoString mRNA expression and WB analyses showed transcriptional activation and protein expression of all three cathepsins, although cathepsin G was expressed at low levels. EAAs demonstrated that cathepsin B and cathepsin D were functionally active. IF IHC staining illustrated localization of cathepsin B and cathepsin D to the endothelium and SMA<sup>+</sup> pericyte layer of the microvessels, while cathepsin G was localized to cells scattered within the interstitium, away from the microvessels.</p><p><bold>Conclusion:</bold> Cathepsin B and cathepsin D, and to a lesser extent cathepsin G, are expressed in WHO grade I MG. Cathepsin B and cathepsin D are enzymatically active and are localized to the putative TSC population on the microvessels, whereas cathepsin G was localized to cells scattered within the interstitium, These results suggest the presence of bypass loops for the RAS, within WHO grade I MG.</p>