Potential role of Wnt/ß-catenin signaling in blastic transformation of chronic myeloid leukemia: cross talk between ß-catenin and BCR-ABL.

Chronic myeloid leukemia (CML) results from malignant transformation of hematopoietic stem cells induced by the BCR-ABL oncogene. Transformation from chronic to blastic phase is the lethal step in CML. Leukemic stem cells (LSCs) are the basic reason for blastic transformation. It has been shown that Wnt/ß-catenin signaling contributes to the self-renewal capacity and proliferation of LSCs in CML. However, the role of Wnt/ß-catenin signaling in blastic transformation of CML is still obscure. Here, we explored the relationship between BCR-ABL and ß-catenin signaling in vitro and in vivo. We found that BCR-ABL stimulated ß-catenin via activation of PI3K/AKT signaling in blastic phase CML cells. Inhibition of the kinase activity of BCR-ABL, PI3K, or AKT decreased the level of ß-catenin in both K562 cells and a CML mouse model and suppressed the transcription of downstream target genes (c-myc and cyclin D1). In addition, inhibition of the BCR-ABL/PI3K/AKT pathway delayed the disease progression in the CML mouse model. To further explore the role of ß-catenin in the self-renewal and survival of CML LSCs, we established a secondary transplantation CML mouse model. Our data revealed that inhibition of the BCR-ABL/PI3K/AKT pathway reduced the tumor-initiating ability of K562 cells, decreased leukemia cell infiltration into peripheral blood and bone marrow, and prolonged the survival of mice. In conclusion, our data indicate a close relationship between ß-catenin and BCR-ABL/PI3K/AKT in blastic phase CML. ß-Catenin inhibition may be of therapeutic value by targeting LSCs in combination with a tyrosine kinase inhibitor, which may delay blastic transformation of CML.

[Indomethacin Significantly Enhances Inhibitory Effect of Imatinib on Proliferation of KCL22 and K562/G01 Cells].

OBJECTIVE: To investigate the inhibitory effect of indomethacin combined with imatinib on proliferation of KCL22 and K562/G01 cells, and to elucidate the molecular mechanism of antiproliferative effect by Wnt/ß-Catenin signaling way. METHODS: Indomethacin was used in KCL22 and K562/G01 cells. The cell growth was detected by MTT assay to explore the optimal concentration and time. The effect of drugs on proliferation capacity was assessed by MTT assay and colony-forming assay. Flow cytometry was used to identify the cell cycle and apoptosis changes. The protein expression of pß-catenin (S33/37/T41), pGSK-3ß (Ser9) and C-MYC were analyzed by Western blot. RESULTS: The optimal concentration and time of indomethacin on KCL22 and K562/G01 were 80 µmol/L for 48 h. The inhibitory effect of 80 µmol/L indomethacin combined 2 µmol/L imatinib on cell proliferation was significantly better than a single drug treatment. Flow cytometry results showed that cell cycle was arrested in the G0/G1 phase in both combined treatment groups. The number of apoptosis cells in combined treatment groups was significantly higher than that in single drug treatment groups. Compared with the control group or single drug treatment groups, the protein level of pß-catenin, ß-catenin, pGSK-3ß (Ser9) and C-MYC decreased significantly. CONCLUSION: Indomethacin significantly enhances inhibitory effect of imatinib on proliferation of KCL22 and K562/G01 cells and regulate cell proliferation through Wnt/ß-Catenin signaling way.