CD133+ Human Colorectal Adenocarcinoma Cells Are Resistant to Staining with Fluorescent Dyes Used for Analysis of ABC Transporter Activities

Flow cytometry measurement of the expression of surface marker CD133 simultaneously with the analysis of fluorescent dye exclusion was performed in order to develop new methods for detection of cancer stem cell populations in tumor tissue samples from patients with colorectal adenocarcinoma. No correlation was found between the count of CD133+ cancer cells and the volume of the “population” formed from cells actively pumping off the fluorescent dye. On the other hand, the fluorescence distribution plot showed predominant location of CD133+ cancer cells among cells stained with neither DyeCycle Violet DNA-binding dye, nor rhodamine 123 mitochondrial dye. These cells did not show the properties of the classical “side population”, because they did not shift to the area of stained cell after treatment with ionic channel blocker verapamil.