Isolation and phenotypic characterization of cancer stem-like side population cells in colon cancer

Previous studies in cancer biology suggest that chemotherapeutic drug resistance and tumor relapse are driven by cells within a tumor termed 'cancer stem cells'. In the present study, a Hoechst 33342 dye exclusion technique was used to identify cancer stem-like side population (SP) cells in colon carcinoma, which accounted for 3.4% of the total cell population. Following treatment with verapamil, the population of SP cells was reduced to 0.6%. In addition, the sorted SP cells exhibited marked multidrug resistance and enhanced cell survival rates compared with non-SP cells. The SP cells were able to generate more tumor spheres and were CD133 positive. Subsequent biochemical analysis revealed that the levels of the adenosine triphosphate-binding cassette sub-family G member 2 transporter protein, B-cell lymphoma anti-apoptotic factor and autocrine production of interleukin-4 were significantly enhanced in the colon cancer SP cells, which contributed to drug resistance, protection of the cells from apoptosis and tumor recurrence. Therefore, the findings suggested that treatment failure and colon tumorigenesis is dictated by a small population of SP cells, which indicate a potential target in future therapies.