Flow cytometric techniques for detection of candidate cancer stem cell subpopulations in canine tumour models.
ABSTRACT The cancer stem cell (CSC) hypothesis proposes that tumour growth is maintained by a distinct subpopulation of 'CSC'. This study applied flow cytometric methods, reported to detect CSC in both primary and cultured cancer cells of other species, to identify candidate canine subpopulations. Cell lines representing diverse canine malignancies, and cells derived from spontaneous canine tumours, were evaluated for expression of stem cell-associated surface markers (CD34, CD44, CD117 and CD133) and functional properties [Hoecsht 33342 efflux, aldehyde dehydrogenase (ALDH) activity]. No discrete marker-defined subsets were identified within established cell lines; cells derived directly from spontaneous tumours demonstrated more heterogeneity, although this diminished upon in vitro culture. Functional assays produced variable results, suggesting context-dependency. Flow cytometric methods may be adopted to identify putative canine CSC. Whilst cell lines are valuable in assay development, primary cells may provide a more rewarding model for studying tumour heterogeneity in the context of CSC. However, it will be essential to fully characterize any candidate subpopulations to ensure that they meet CSC criteria.
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ABSTRACT: Cancer stem-like cells (CSCs)/cancer-initiating cells (CICs) are a small subpopulation of cancer cells that are responsible for the initiation, recurrence and metastasis of cancer. We previously demonstrated that, using the Hoechst 33342 dye-based side population technique, CSCs/CICs in canine lung adenocarcinoma cell line exist. In this study, as CSCs/CICs are known to form spheres in anchorage-independent environment in vitro, we evaluated the stemness of spheroid cells derived from canine lung adenocarcinoma and osteosarcoma cells by expression of stemness markers, and investigated radioresistance. Spheroid cells showed greater expression of stemness markers Oct-4 and CD133 gene than those of adherent-cultured cells. In nude mouse xenograft models, spheroid cells showed higher tumourigenic ability than adherent-cultured cells. In addition, spheroid cells showed significantly resistant against radioactivity as compared with adherent-cultured cells. These results suggest that spheroid cells could possess stemness and provide a CSCs/CICs research tool to investigate CSCs/CICs of canine tumour cells.Veterinary and Comparative Oncology 07/2014; · 1.45 Impact Factor
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ABSTRACT: Cancer stem cells (CSCs) represent a small subpopulation of tumor cells that play a critical role in initiating and sustaining tumor growth. However, we currently have an incomplete understanding of the expression patterns of CSC antigens in tumors of dogs, nor do we understand how expression of these antigens vary between tumor cell lines and tumor biopsy specimens. Therefore, we used flow cytometry and commonly reported CSC surface and intracellular markers to evaluate the phenotype and overall frequency of CSC subpopulations in tumor cell lines and primary tumor biopsy samples from dogs with melanoma and osteosarcoma. We found that cells expressing common CSC antigens were rare in tumor cell lines, with the exception of tumor cells expressing CD44 and CD90. In contrast, tumor cells expressing conventional CSC antigens such as CD133, CD34, CD44, CD24 and Oct3/4 were much more common in tumor biopsy samples. Notably, the frequency and types of putative CSC subpopulations were very similar in biopsy samples from dogs with either melanoma or osteosarcoma. Our results suggest that the tumor microenvironment significantly influences CSC subpopulations within tumors and that tumor cell lines may not accurately reflect the actual frequency or types of CSC subpopulations present in tumor tissues in vivo.Veterinary Immunology and Immunopathology 01/2014; · 1.75 Impact Factor