Study on the mechanism of circular permuted tumor necrosis factor-related apoptosis-inducing ligand reversing the resistance to imatinib in chronic myeloid leukemia cells / 白血病·淋巴瘤

ABSTRACT

Objective:To explore the mechanism of circular permuted tumor necrosis factor-related apoptosis-inducing ligand (CPT) reversing the resistance to imatinib in chronic myeloid leukemia (CML) cells.Methods:Five patients with CML in the Affiliated Hospital of Inner Mongolia Medical University from 2016 to 2020 were selected, and heparinized bone marrow blood samples were collected at the first diagnosis and imatinib resistance phase, and mononuclear cells were isolated. The mononuclear cells collected at the first diagnosis were named A1-E1, and the mononuclear cells collected after imatinib resistance were named A2-E2. Human CML wild-type K562 cell line (K562-W) was given gradually increasing small doses of low-concentration imatinib to obtain imatinib-resistant K562 cells (K562-R). K562-R cells were cultured with 20 μg/L CPT and these cells were set as CPT-K562-R group. The CCK-8 method was used to detect the half inhibitory concentration ( IC50) of cells for imatinib. K562-W and K562-R cells were used to establish CML xenografts nude mice models, then the nude mice were divided into K562-W, K562-R and CPT-K562-R xenograft groups. Imatinib was perfused orally in all three groups, and CPT was injected subcutaneously in the CPT-K562-R group at the same time. The tumor volume of the three groups of nude mice before and 4 weeks after treatment with imatinib, and the survival time of the three groups of nude mice were compared. Western blot was used to detect the changes of tyrosine protein kinase receptor B4 (EphB4) and myeloid cell leukemia protein 1 (Mcl-1) protein levels in bone marrow mononuclear cells, K562 cell line and transplanted tumor tissues of CML patients. Results:The expressions of EphB4 protein in A2-E2 cells of 5 patients with CML were higher than those in A1-E1 cells (all P < 0.01). The IC50 of K562-W, K562-R and CPT-K562-R cells for imatinib were (0.160±0.015) mg/L, (5.450±0.460) mg/L, (0.300±0.035) mg/L, and the difference was statistically significant ( F = 390.65, P < 0.01). In cells of K562-W group, EphB4 and Mcl-1 proteins were expressed at low levels (0.54±0.02 and 0.70±0.08); in cells of K562-R group, the expressions of EphB4 and Mcl-1 proteins were enhanced (3.04±0.11 and 2.88±0.04); in cells of CPT-K562-R group, the expressions of EphB4 and Mcl-1 proteins decreased (0.57±0.03 and 0.38±0.04). Before imatinib treatment, there was no statistically significant difference in the tumor volumes of nude mice among the K562-W, K562-R and CPT-K562-R xenograft groups ( F = 0.39, P = 0.68), suggesting the transplanted tumors formed in nude mice were balanced; after imatinib treatment, the difference in the tumor volumes among the three groups were statistically significant ( F = 26.16, P < 0.01). The survival time of nude mice in the K562-W, K562-R and CPT-K562-R xenograft groups was (18.5±3.3) d, (10.0±2.4) d and (17.5±1.6) d, and the difference was statistically significant ( F = 20.45, P < 0.01). In K562-W xenograft group, both EphB4 and Mcl-1 proteins were expressed at low levels (0.55±0.06 and 0.67±0.06); in K562-R xenograft group, the expressions of EphB4 and Mcl-1 proteins were enhanced (1.95±0.08 and 6.21±0.53); the expressions of EphB4 and Mcl-1 in CPT-K562-R xenograft group decreased (0.59±0.04 and 0.37±0.04) and were close to their expressions in K562-W xenograft group. Conclusion:CPT may enhance the sensitivity of CML to imatinib by inhibiting the expressions of EphB4 and Mcl-1, and this may be a targeted pathway for imatinib therapy.