Isolation and Characterization of Putative Cancer Stem Cells from Oral Squamous Cell Carcinoma Cells

Oral squamous cell carcinoma is the most common oral malignancy, and still, despite the recent therapeutic advances, has rather poor prognosis with low 5-year survival rates. One possible cause for the treatment failures are cancer stem cells, which may participate in the resistance to chemo- and radiotherapies. The aim of our study was to isolate cancer stem cell subpopulations from an oral squamous cell carcinoma cell line based on CD44 and CD326 CSC markers, and to investigate their phenotypic characteristics.

Cell subpopulations with distinct staining intensities for CD44 and CD326 were isolated from the SCC-9 ZsGreen parental cell line by using fluorescence-activated cell sorting: CD44⁺/CD326^- (SCC-9 CSC-M) and CD44^Low/CD326^High (SCC-9 CSC-E). Their proliferative capacities, clonogenic potential, adhesion and migration, and production of epithelial-mesenchymal transition markers were evaluated. Sensitivities to cisplatin and TVB-3166 were assessed using MTT assays.

The SCC-9 CSC-M phenotype cells had the highest proliferation and migratory potential of all the three cell lines, and IC₅₀ for cisplatin was similar to the parental cells, but they were more resistant than the parental cells to TVB-3166. SCC-9 CSC-E phenotype cells showed a tendency for an epithelial trait, and they were resistant to both drugs.

The putative cancer stem cell subpopulations, isolated by their CD44/CD326 expression patterns, exhibited distinct cancer properties compared to the parental oral squamous cell carcinoma cell line, and might be useful for developing novel therapies.