Establishment of surface marker expression profiles for colorectal cancer stem cells under different conditions

Background: Positive expression of CD44 and CD133 and high expression levels of an epithelial cell adhesion molecule are reliable markers for colorectal cancer stem cells in tumors or among circulating tumor cells. However, the heterogeneity of circulating tumor cells makes it very difficult to detect these stem cells. In this study, we investigated the expression of CD44 and CD133 of colorectal cancer stem cells under different treatments in order to understand the expression profile of these markers when cancer cells grow in different conditions. Methods: Cells from a colorectal cancer stem cell line, Caco-2, were seeded at four different initial concentrations and cultured for 3 days. We observed for changes in cell morphology and analyzed the expression of CD44 and CD133 by flow cytometry. In addition, Caco-2 cells were treated with eicosapentaenoic acid (EPA), dimethyl sulfoxide (DMSO), and ethylenediaminetetraacetic acid (EDTA) for 3 days followed by flow cytometry analysis. Results: We demonstrated that the single and combined expression of CD44 and CD133 decreased when the initial seeding concentration was reduced. The expression of both CD44 and CD133 was reduced dramatically when Caco-2 cells were treated with EPA, DMSO, or EDTA. The single expression of CD44 or CD133 was not affected dramatically when cells were treated with DMSO or EDTA, but there was no expression of either markers when treated with EPA. Conclusions: Both single and combined expressions of CD44 and CD133 were critical for establishing the profiles of colorectal cancer stem cells under different conditions.