ABSTRACT
BACKGROUND:Imatinib resistance is a key issue in treatment of chronic myeloid leukemia. It is confirmed that the leukemia cels can obtain drug resistance phenotype mediated by adhesion to the bone marrow stromal cels (BMSCs). But, the role of BMSCs in imatinib resistance is unclear because chronic myeloid leukemia is deficient in adhesion function. OBJECTIVE: To in vitro simulate the bone marrow microenvironment of patients with chronic myeloid leukemia and to explore its influences on imatinib sensitivity as wel as possible mechanisms. METHODS:BMSCs isolated from patients with chronic myeloid leukemia but not undergoing treatment were co-cultured with K562 cels to construct the BMSCs-K562 cel co-culture model in chronic myeloid leukemia patients, then exposed to 0.2-3.2 μmol/L imatinib for 48 hours, and the proliferation inhibition rate of K562 cels was studied by MTT assay. The apoptosis rate of K562 cels and the expression of the CXCR4 in K562 cels exposed to 0.5 μmol/L imatinib for 72 hours were detected by flow cytometry. The K562 cels were exposed to 0.5 μmol/L imatinib for 4 hours and labeled by Calcein-AM fluorescent labeling sytem, and then, the adhesion rate of the K562 cels was calculated based on fluorescence intensity. RESULTS AND CONCLUSION: The suppressing effect of imatinib (0.2-3.2μmol/L) on the proliferation of K562 cels was weakened significantly by co-culture with the bone marrow stromal cels from patients with chronic myeloid leukemia. The apoptosis rate of K562 cels exposed to 0.5 μmol/L imatinib for 72 hours in co-culture group was significantly lower than that in the suspension culture group (P=0.020). The positive rates of CXCR4 in the co-culture group and suspension culture groups were both increased after exposure to 0.5 μmol/L imatinib for 72 hours (P=0.001). The adhesion rate of the K562 cels to the BMSCs was elevated from (32.18±6.17)% to (68.97±11.08)% when the K562 cels were exposed to 0.5 μmol/L imatinib for 4 hours, and the difference had statistical significance (P=0.022). These findings indicate that the co-culture with the BMSCs from patients with chronic myeloid leukemia can mediate K562 cels resistance to imatinib, which may be related to that the co-culture with BMSCs and exposure to imatinib can induce the K562 cels to express CXCR4. But the mechanism needs in-depth studies.