Characterization Of Side Population Of Stem-Like Cancer Cells In Bladder Cancer Cell Line

Objective: To find out a feasible way to detect the tumor stem-like cells in bladder cancer cells, and to analyze the properties of the side population (SP) being sorted.Methods: Among 5 bladder cancer cell lines, including bladder squamous cancer cell line SCaBER and bladder transitional cancer cell line T24,5637,Biu-87,EJ, stem-like cancer cells were identified by using the flow cytometry based side population technique. The side population sorted by this method was observed by electron fluorescence microscope and re-analyze by flow cytometry. The oncogenicity of SP and non-SP cells was observed by implanting NOD/SC1D mice model. SP cells and non-SP cells were isolated separately and injected into the subcutaneous space of NOD/SCID mice by 1×104 and 1×105 respectively. The drug resistance to mitomycin C (0.05 mg/ ml, 0.1 mg/ml, 0.5 mg/ml) of SP, non-SP cells and unsorted cells was measured with MTT color-metric assay.Results: Side population was characterized only in bladder squamous cancer cell line SCaBER, and this population accounted for about 0.6% in the total cells. SP cells were smaller than non-SP cells observed by fluorescence microscope; meanwhile their blue fluorescence was weak or disappeared. After culture, SP cells could divide into SP cells and non-SP cells detected by flow cytometry. Sorted SP was more tumorigenic than the corresponding non-side population. All kinds of 104 cells injection consistently failed to form tumors in all mice. 105 SP cells injection could initiate tumors in two of three mice (67%), however, tumors in the mice injected of non-SP cells were not observed. The SP also had the ability to discard fluorchrome which may lower the inhibition ratio of SP (56.61±4.16) % than non-SP(60.25±2.52) % and unsorted SCaBER (61.42±2.33) % in 0. 05 mg/ml mitomycin C (P <0.05).Conclusion: The side population sorted from SCaBER cell line may have more tumorigenicity than the regular bladder cancer cells and some drug resistance ability. And the SP cancer cells may exhibit some drug resistance properties.