Potential role of Wnt/β-catenin signaling in blastic transformation of chronic myeloid leukemia: cross talk between β-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/beta-catenin signaling contributes to the self-renewal capacity and proliferation of LSCs in CML. However, the role of Wnt/beta-catenin signaling in blastic transformation of CML is still obscure. Here, we explored the relationship between BCR-ABL and beta-catenin signaling in vitro and in vivo. We found that BCR-ABL stimulated beta-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 beta-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 beta-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 tumorinitiating 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 beta-catenin and BCR-ABL/PI3K/AKT in blastic phase CML. beta-Catenin inhibition may be of therapeutic value by targeting LSCs in combination with a tyrosine kinase inhibitor, which may delay blastic transformation of CML.