Study on the Resistant Mechanisms of K562 Cells Induced by STI571.

STI571 is a highly effective drug for the therapy of CML, but there is still drug resistance, especially in blast crisis. To study the possible mechanisms of resistance to STI571, we established the BCR/ABL⁺ cell line with resistance to STI571 (K562-R) in vitro by culturing a wild-type K562 cells (K562-W) in gradually increased concentrations of STI571 over a period of months. Trypan blue staining, MTT assay and Hoechst 33342 staining confirmed that K562-R can live steadily at 0.5umol/L STI571. Furthermore MDR-1 expression assay, sequence analysis, fluorescence in situ hybridization(FISH) and cDNA array were used to study the potential mechanisms of acquired resistance. The MDR-1 expression percentages of K562-W and K562-R with FASC analysis were 2.68% and 1.39% respectively. No point mutant in the BCR/ABL ATP-binding site was detected and the copies of BCR/ABL fusion gene were found increased in K562-R by FISH analysis. By a expression profile of cDNA microarray, 327 genes’ expression were found down-regulating including one of homo sapiens protein tyrosine phosphatase genes(PTPRF) and 335 genes up-regulating including homo sapiens hematopoietic cell-specific Lyn substrate 1 gene(HCLS1). Our studies proved the possible mechanism of K562-R resistance involved amplification of BCR/ABL fusion gene and increase of phosphorylation activity in this cell line.