De-regulated STAT5A/miR-202-5p/USP15/Caspase-6 regulatory axis suppresses CML cell apoptosis and contributes to Imatinib resistance

Abstract

Background: STAT5 plays an important role in the transformation of hematopoietic cells by BCR-ABL. However, the downstream target genes activated by STAT5 in chronic myeloid leukemia (CML) cells remain largely unclear. Here, we investigated the mechanistic functional relationship between STAT5A-regulated microRNA and CML cell apoptosis. Methods: The expression of USP15, Caspase-6, STAT5A-regulated miR-202-5p and STAT5A was detected by qRT-PCR and Western blotting in CML cell lines and PBMCs of CML patients. Cell apoptosis was evaluated by flow cytometry. Both gain-and loss-of-function experiments were used to investigate the roles of USP15, miR-202-5p and STAT5A in CML. Luciferase reporter assay detected the effect of miR-202-5p on USP15 expression. Xenograft animal model was used to test the effect of anti-miR-202-5p and pimozide on K562 cell xenograft growth. Results: USP15 expression was significantly downregulated in CML cell lines and PBMCs of CML patients. Depletion of USP15 increased, whereas overexpression of USP15 reduced the resistance of CML cells to Imatinib. Further, decreased deubiquitinating activity of USP15 by USP15 downregulation led to reduced caspase-6 level, thus attenuating CML cell apoptosis. Mechanistically, miR-202-5p was upregulated in K562G cells and negatively regulated USP15 expression by directly targeting USP15 3′-UTR. Correspondingly, upregulation of miR-202-5p enhanced the resistance of CML cells to Imatinib by inhibiting cell apoptosis. Importantly, STAT5A was upregulated in CML cells and directly activated miR-202-5p transcription by binding to the pre-miR-202 promoter. Pimozide induced CML cell apoptosis and significantly reduced K562 cell xenograft growth in vivo by blocking STAT5A/miR-202-5p/USP15/Caspase-6 regulatory axis. Conclusions: we provide the first evidence that de-regulated STAT5A/miR-202-5p/USP15/Caspase-6 regulatory axis suppresses the apoptosis of CML cells, targeting this pathway might be a promising therapeutic approach for the treatment of CML.

HNRNPH1 Is a Novel Regulator Of Cellular Proliferation and Disease Progression in Chronic Myeloid Leukemia

“…The Long Noncoding RNA MEG3 which could sponge to miRNA inhibit the CML cell proliferation in CML cells and contributes to CML progression ( 25 , 26 ). Moreover, the deubiquitinating enzyme ubiquitin-specific peptidase 15 expression level was significantly downregulated in CML patients by blocking JAK/STAT5 pathway and involved in imatinib resistance ( 27 ). However, the specific mechanisms of CML development and progression remain exclusive.…”

Expression profile of SYNE3 and bioinformatic analysis of its prognostic value and functions in tumors

“…Moreover, apoptosis, a pathway closely to P53, also enriched 5 SYNE3 interacting genes, involving CASP8 again, LMNA, CASP6, LMNB1 and LMNB2. Among them, downregulation of CASP6 induced suppression of the apoptosis of chronic myeloid leukemia cells [32]. LMNB1 and LMNB2 are coding genes for lamin B1 and lamin B2 respectively, which are nucleoskeleton components associated with cancer and aging [33].…”

Expression profile of SYNE3 and bioinformatic analysis of its prognostic value and functions in tumors

“…Moreover, apoptosis, a pathway closely to P53, also enriched 5 SYNE3 interacting genes, involving CASP8 again, LMNA, CASP6, LMNB1 and LMNB2. Among them, downregulation of CASP6 induced suppression of the apoptosis of chronic myeloid leukemia cells [ 42 ]. LMNB1 and LMNB2 are coding genes for lamin B1 and lamin B2, respectively, which are nucleoskeleton components associated with cancer and aging [ 43 ].…”