circ_0080145 Enhances Imatinib Resistance of Chronic Myeloid Leukemia by Regulating miR-326/PPFIA1 Axis.

Background: Acquired multidrug resistance is often blamed for the failure of chemotherapy in patients with malignant tumors, including chronic myeloid leukemia (CML). In this study, the authors investigated the role of circular RNA 0080145 (circ_0080145) in imatinib (IM) resistance of CML. Materials and Methods: Quantitative real-time polymerase chain reaction was applied to measure the expression of circ_0080145, microRNA-326 (miR-326), and PTPRF interacting protein alpha 1 (PPFIA1) mRNA. 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay was used to determine the half maximal inhibitory concentration (IC50) of IM and cell proliferation. Flow cytometry analysis was utilized to assess cell apoptosis. The levels of glucose uptake and lactate production were examined using specific kits. Protein levels were detected through Western blot assay. The targeting relationship between miR-326 and circ_0080145 or PPFIA1 was verified by dual-luciferase reporter assay. The murine xenograft model was constructed to investigate the effect of circ_0080145 in vivo. Results: circ_0080145 was upregulated in IM-resistant CML patients and cells. circ_0080145 silencing suppressed IM resistance, cell growth, and glycolysis and induced apoptosis in IM-resistant CML cells in vitro. Moreover, circ_0080145 knockdown blocked tumor growth and IM resistance in vivo. miR-326 was a target of circ_0080145, and miR-326 inhibition restored the effects of circ_0080145 silencing on cell progression and IM resistance. In addition, PPFIA1 was a target gene of miR-326. The suppressive roles in IM resistance, cell growth and glycolysis, and the promotional role in apoptosis mediated by miR-326 were abolished by PPFIA1 overexpression in IM-resistant CML cells. Conclusion: circ_0080145 contributes to IM resistance via modulating miR-326/PPFIA1 axis, which might provide a novel avenue for CML therapy.