Cancer Stem Cells in Head and Neck Cutaneous Squamous Cell Carcinoma Express Cathepsins

Therese Featherston; Helen D Brasch; Sam D Siljee; Bede van Schaijik; Josie Patel; Jennifer de Jongh; Reginald W Marsh; Tinte Itinteang; Swee T Tan

doi:10.1097/GOX.0000000000003042

Cancer Stem Cells in Head and Neck Cutaneous Squamous Cell Carcinoma Express Cathepsins

Plast Reconstr Surg Glob Open. 2020 Aug 19;8(8):e3042. doi: 10.1097/GOX.0000000000003042. eCollection 2020 Aug.

Authors

Affiliations

¹ Gillies McIndoe Research Institute, Newtown, Wellington, New Zealand.
² Department of Medicine, University of Auckland, Auckland, New Zealand.
³ Wellington Regional Plastic, Maxillofacial & Burns Unit, Hutt Hospital, Wellington, New Zealand.
⁴ Department of Surgery, The University of Melbourne, Parkville, Victoria, Australia.

Abstract

Cancer stem cell (CSC) subpopulations within moderately differentiated head and neck cutaneous squamous cell carcinoma (MDHNcSCC) express the components of the renin-angiotensin system (RAS). This study investigated the expression of cathepsins B, D, and G, which constitute bypass loops of the RAS, by CSCs in MDHNcSCC.

Methods: Immunohistochemical staining was performed on MDHNcSCC tissue samples from 15 patients to determine the expression of cathepsins B, D, and G. Co-localization of these cathepsins with the embryonic stem cell markers Octamer-binding transcription factor 4 (OCT4) and c-MYC was investigated with immunofluorescence staining. Reverse transcription quantitative polymerase chain reaction was performed on 5 MDHNcSCC tissue samples to investigate transcript expression of cathepsins B, D and G. Western blotting and enzymatic activity assays were performed on 5 MDHNcSCC tissue samples and 6 MDHNcSCC-derived primary cell lines to confirm protein expression, transcript expression, and functional activity of these cathepsins, respectively.

Results: Immunohistochemical staining demonstrated the expression of cathepsins B, D, and G in all MDHNcSCC tissue samples. Immunofluorescence staining showed localization of cathepsins B and D to the c-MYC⁺ CSC subpopulations and the OCT4⁺ CSC subpopulations within the tumor nests and the peritumoral stroma. Cathepsin G was expressed on the tryptase⁺/c-MYC⁺ cells within the peritumoral stroma. Reverse transcription quantitative polymerase chain reaction demonstrated transcript expression of cathepsins B, D and G in the MDHNcSCC tissue samples. Western blotting and enzymatic activity assays confirmed protein expression and functional activity of cathepsins B and D in the MDHNcSCC tissue samples and MDHNcSCC-derived primary cell lines, respectively.

Conclusions: Cathepsins B, D, and G are expressed in MDHNcSCC with functionally active cathepsins B and D localizing to the CSC subpopulations, and cathepsin G is expressed by mast cells, suggesting the potential use of cathepsin inhibitors in addition to RAS blockade to target CSCs in MDHNcSCC.