BCR and chronic myelogenous leukemia, BCR-ABL1 positive: CML treatment with Bortezomib (BZ), a specific and reversible inhibitor of proteasome activity which is licensed for clinical use in mantle cell lymphoma and multiple myeloma, is being proposed to target LSC [8], on the basis of data indicating that BCR/Abl expression results in increased proteasome activity and that proteasome inhibition is cytotoxic against CML cell lines [9].