Cross talk between Wnt/β-catenin and Irf8 in leukemia progression and drug resistance.

Progression and disease relapse of chronic myeloid leukemia (CML) depends on leukemia-initiating cells (LIC) that resist treatment. Using mouse genetics and a BCR-ABL model of CML, we observed cross talk between Wnt/β-catenin signaling and the interferon-regulatory factor 8 (Irf8). In normal hematopoiesis, activation of β-catenin results in up-regulation of Irf8, which in turn limits oncogenic β-catenin functions. Self-renewal and myeloproliferation become dependent on β-catenin in Irf8-deficient animals that develop a CML-like disease. Combined Irf8 deletion and constitutive β-catenin activation result in progression of CML into fatal blast crisis, elevated leukemic potential of BCR-ABL-induced LICs, and Imatinib resistance. Interestingly, activated β-catenin enhances a preexisting Irf8-deficient gene signature, identifying β-catenin as an amplifier of progression-specific gene regulation in the shift of CML to blast crisis. Collectively, our data uncover Irf8 as a roadblock for β-catenin-driven leukemia and imply both factors as targets in combinatorial therapy.