AimTo investigate the expression of cathepsins B, D, and G, in relation to the cancer stem cell (CSC) subpopulations, we have previously characterized within isocitrate dehydogenase (IDH)-wildtype glioblastoma (IDHWGB).Methods3,3-Diaminobezidine (DAB) immunohistochemical (IHC) staining for cathepsins B, D, and G, was performed on 4μm-thick formalin-fixed paraffin-embedded IDHWGB samples obtained from six patients. Two representative DHWGB samples from the original cohort of patients were selected for immunofluorescent (IF) IHC staining, to identify the localization of the cathepsins in relation to the CSC subpopulations. NanoString gene expression analysis and colorimetric in situ hybridization (CISH) were conducted to investigate the transcriptional activation of genes encoding for cathepsins B, D, and G. Data obtained from cell counting of DAB IHC-stained slides and from NanoString analysis were subjected to statistical analyses to determine significance.ResultsCathepsin B and cathepsin D were detected in IDHWGB by DAB IHC staining. IF IHC staining demonstrated the expression of both cathepsin B and cathepsin D by the OCT4+ and SALL4+ CSC subpopulations. NanoString gene analysis and CISH confirmed the abundant transcript expression of these cathepsins. The transcriptional and translational expressions of cathepsin G were minimal and were confined to cells within the microvasculature.ConclusionThis study demonstrated the expression of cathepsin B and cathepsin D but not cathepsin G within the CSC subpopulations of IDHWGB at both the transcriptional and translational level. Cathepsin G was expressed at low levels and was not localized to the CSC population of IDHWGB. The novel finding of cathepsin B and cathepsin D in IDHWGB suggests the presence of bypass loops for the renin-angiotensin system, which may facilitate the production of angiotensin peptides. Elucidating the precise role of these cathepsins may lead to better understanding and more effective treatment of this aggressive tumor.

Cancer stem cells (CSC), the putative origin of cancer, account for local recurrence and metastasis. We aimed to identify and characterize CSCs within moderately differentiated head and neck cutaneous squamous cell carcinoma (MDHNCSCC). Formalin-fixed paraffin-embedded MDHNCSCC sections of ten patients underwent 3,3-diaminobenzidine (DAB) immunohistochemical (IHC) staining for induced pluripotent stem cell (iPSC) markers OCT4, NANOG, SOX2, KLF4 and c-MYC. Localization of these markers was investigated using immunofluorescence (IF) IHC staining of three of these MDHNCSCC samples. mRNA expression of these iPSC markers in the MDHNCSCC tissue samples was determined by colorimetric in-situ hybridization (CISH, n = 6), and reverse-transcription quantitative polymerase chain reaction (RT-qPCR, n = 4). RT-qPCR was also performed on four MDHNCSCC-derived primary cell lines. DAB IHC staining demonstrated expression of all five iPSC markers within all ten MDHNCSCC tissues samples. CISH and RT-qPCR confirmed mRNA expression of all five iPSC markers within all MDHNCSCC tissues samples examined. RT-PCR demonstrated mRNA transcripts of all five iPSC markers in all four MDHNCSCC-derived primary cell lines. IF IHC staining showed co-expression of OCT4 with SOX2 and KLF4 throughout the tumor nests (TNs) and peri-tumoral stroma (PTS). There was an OCT4 + /NANOG + subpopulation within the TNs, and an OCT4 + /NANOG − subpopulation and an OCT4 + /NANOG + subpopulation within the PTS. All iPSC markers were expressed by the endothelium of microvessels within the PTS. Our findings suggest the presence of an OCT4 + /NANOG + /SOX2 + /KLF4 + /c-MYC + CSC subpopulation within the TNs, PTS and endothelium of microvessels within the PTS; and an OCT4 + /NANOG − /SOX2 + /KLF4 + /c-MYC + subpopulation exclusively within the PTS in MDHNCSCC. These CSC subpopulations could be a potential novel therapeutic target for treatment of MDHNCSCC.

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