Furthermore, it was observed that bortezomib treatment in CML cell lines led to reduced expression of inhibitory apoptotic proteins such as XIAP, cIAP1, and survivin implicating the role of IAPs in the activation of caspase-9 and caspase-3 in bortezomib-induced apoptosis. This evidence concerns the gene BIRC2 and chronic myelogenous leukemia, BCR-ABL1 positive.