AUTHOR=Featherston Therese , Marsh Reginald Walter , van Schaijik Bede , Brasch Helen D. , Tan Swee T. , Itinteang Tinte 

TITLE=Expression and Localization of Cathepsins B, D, and G in Two Cancer Stem Cell Subpopulations in Moderately Differentiated Oral Tongue Squamous Cell Carcinoma

JOURNAL=Frontiers in Medicine

VOLUME=Volume 4 - 2017

YEAR=2017

URL=https://www.frontiersin.org/journals/medicine/articles/10.3389/fmed.2017.00100

DOI=10.3389/fmed.2017.00100

ISSN=2296-858X

ABSTRACT=Aim We have previously demonstrated the putative presence of two cancer stem cell (CSC) subpopulations within moderately differentiated oral tongue squamous cell carcinoma (MDOTSCC), which express components of the renin-angiotensin system (RAS). In this study, we investigated the expression and localization of cathepsins B, D and G in relation to these cancer stem cell (CSC) subpopulations within MDOTSCC.

Methods 3,3-Diaminobenzidine (DAB) and immunofluorescent (IF) immunohistochemical (IHC) staining was performed on MDOTSCC samples to determine the expression and localization of cathepsins B, D and G in relation to the CSC subpopulations. NanoString analysis and colorimetric in-situ hybridization (CISH) were used to study their transcripts expression. Enzyme activity assays were performed to determine their activity in MDOTSCC. 

Results IHC staining demonstrated expression of cathepsin B, D and G in MDOTSCC. Cathepsins B and D were localized to CSCs within the tumor nests, while cathepsins B was localized to the CSCs within the peri-tumoral stroma, and cathepsin G was localized to the tryptase+ phenotypic mast cells within the peri-tumoral stroma. NanoString and CISH analyses confirmed transcription activation of cathepsins B, D and G. Enzyme activity assays confirmed active cathepsins B and D, but not cathepsin G.

Conclusions The presence of cathepsins B and D within CSCs and cathspsin G within phenotypic mast cells suggest bypass loops for the RAS as potential novel therapeutic targets for MDOTSCC.