RESUMEN
BACKGROUND:Studies have shown that tumor stem ceils are the basis and the main cause of tumor recurrence and chemotherapy failure.Therefore,the research on the drug resistance of tumor stem cells has become a hotspot in the field of stem cell research.OBJECTIVE:To analyze the biological characteristics of side population (SP) cells in the U266 cell lines in relation to drug resistance.METHODS:Flow cytometry was used to monitor the percentage of SP cells in the U266 cell lines.Fluorescence-activated cell sorter (FACS) analysis was used to isolate SP and non-SP (NSP) cells from the U266 cell lines.Further analyses of the cell cycle,multidrug resistant protein,methyl cellulose cloning assay of SP cells and NSP cells were performed.Real-time quantitative PCR was used to determine the expression of ABCG2 and MDR1 genes.RESULTS AND CONCLUSION:There were (2.46±0.35)％ SP cells in U266 cells,which were most in the G0 phase.The ratio of G0/G1 in SP cells was (81.50±5.42)％,which was significantly higher than that in NSP cells [(39.85±3.21)％;P ＜0.05].The positive expression rates of P-gp and ABCG2 in SP cells were signficantly higher than those in NSP cells (P ＜0.05).The cloning efficiency of SP cells was significantly higher than that of NSP cells (P ＜ 0.05).The mRNA expression of ABCG2 and MDR1 was also significantly higher in SP cells than in NSP cells (P ＜ 0.05).To conclude,a small subpopulation of the isolates of U266 cell lines belong to tumor stem cell-like SP cell subset,most of which are at the G0 phase.ABCG2 and MDR1 genes are highly expressed in SP cells,which particularly plays a important role in the multidrug resistance of multiple myeloma stem cell lines.