[CRISPR/Cas9-mediated microRNA-21 knockout increased imatinib sensitivity in chronic myeloid leukemia cells]

Objective: To observe the effects of miR-21 knockout on proliferation and drug resistance in K562/G01 cells, and to preliminarily explore the mechanism of imatinib sensitivity by knocking out miR-21 in K562/G01 cells. Methods: Using CRISPR/Cas9 to knock out the miR-21 gene in K562/G01 cells, and single-cell-derived clones of miR-21 knockout were obtained by genomic DNA PCR screening, Sanger sequencing, and real-time PCR. We used MTT and cell colony formation assays to assess the cell proliferation, and determined imatinib sensitivity by MTT assay and Annexin-Ⅴ-APC/7-AAD double staining flow cytometry. Using western blot, we examined the potential mechanisms affecting imatinib sensitivity by knocking out miR-21 in K562/G01 cells. Results: Three miR-21 knockout K562/G01 single-cell-derived clones were successfully constructed. The mutation efficiency mediated by CRISPR/Cas9 was 7.12%-8.11%. MiR-21 knockout inhibited the proliferation of K562/G01 cells; the clone formation rates of WT and 1#, 2#, 6# K562/G01 single-cell clones were (57.67±8.25) %, (26.94± 5.36) %, (7.17±2.11) %, (31.50±3.65) %, respectively. MiR-21 knockout increased the sensitivity of K562/G01 cells to imatinib, IC(50) of imatinib in WT, and 1#, 2#, 6# K562/G01 single-cell clones were (21.92±1.36) µmol/ml, (3.98±0.39) µmol/ml, (5.38±1.01) µmol/ml, (9.24±1.36) µmol/ml. After the knockout of miR-21, the activation of PI3K/Akt signaling molecules was inhibited, while the expression of P210(B)CR-ABL and p-P210(BCR-ABL) was downregulated; however, the expression of PTEN was not affected. Conclusion: The knockout of miR-21 can suppress cell proliferation and improve sensitivity to imatinib in K562/G01 cells, which may be achieved by inhibiting the PI3K/AKT signaling pathway and BCR-ABL expression.