Bucur, OctavianStancu, Andreea LuciaGoganau, IoanaPetrescu, Stefana MariaPennarun, BodvaelBertomeu, ThierryDewar, RajanKhosravi-Far, Roya2014-03-102013Bucur, Octavian, Andreea Lucia Stancu, Ioana Goganau, Stefana Maria Petrescu, Bodvael Pennarun, Thierry Bertomeu, Rajan Dewar, and Roya Khosravi-Far. 2013. “Combination of Bortezomib and Mitotic Inhibitors Down-Modulate Bcr-Abl and Efficiently Eliminates Tyrosine-Kinase Inhibitor Sensitive and Resistant Bcr-Abl-Positive Leukemic Cells.” PLoS ONE 8 (10): e77390. doi:10.1371/journal.pone.0077390. http://dx.doi.org/10.1371/journal.pone.0077390.1932-6203http://nrs.harvard.edu/urn-3:HUL.InstRepos:11878833Emergence of resistance to Tyrosine-Kinase Inhibitors (TKIs), such as imatinib, dasatinib and nilotinib, in Chronic Myelogenous Leukemia (CML) demands new therapeutic strategies. We and others have previously established bortezomib, a selective proteasome inhibitor, as an important potential treatment in CML. Here we show that the combined regimens of bortezomib with mitotic inhibitors, such as the microtubule-stabilizing agent Paclitaxel and the PLK1 inhibitor BI2536, efficiently kill TKIs-resistant and -sensitive Bcr-Abl-positive leukemic cells. Combined treatment activates caspases 8, 9 and 3, which correlate with caspase-induced PARP cleavage. These effects are associated with a marked increase in activation of the stress-related MAP kinases p38MAPK and JNK. Interestingly, combined treatment induces a marked decrease in the total and phosphorylated Bcr-Abl protein levels, and inhibits signaling pathways downstream of Bcr-Abl: downregulation of STAT3 and STAT5 phosphorylation and/or total levels and a decrease in phosphorylation of the Bcr-Abl-associated proteins CrkL and Lyn. Moreover, we found that other mitotic inhibitors (Vincristine and Docetaxel), in combination with bortezomib, also suppress the Bcr-Abl-induced pro-survival signals and result in caspase 3 activation. These results open novel possibilities for the treatment of Bcr-Abl-positive leukemias, especially in the imatinib, dasatinib and nilotinib-resistant CML cases.en-USJournal Article2014-03-1010.1371/journal.pone.0077390