In most patients with chronic myeloid leukemia (CML) clonal cells can be kept under control by BCR::ABL1 tyrosine kinase inhibitors (TKI). However, overt resistance or intolerance against these TKI may occur. We identified the epigenetic reader BRD4 and its downstream-effector MYC as growth regulators and therapeutic targets in CML cells. BRD4 and MYC were found to be expressed in primary CML cells, CD34+ /CD38- leukemic stem cells (LSC), and in the CML cell lines KU812, K562, KCL22, and KCL22T315I . The BRD4-targeting drug JQ1 was found to suppress proliferation in KU812 cells and primary leukemic cells in the majority of patients with chronic phase CML. In the blast phase of CML, JQ1 was less effective. However, the BRD4 degrader dBET6 was found to block proliferation and/or survival of primary CML cells in all patients tested, including blast phase CML and CML cells exhibiting the T315I variant of BCR::ABL1. Moreover, dBET6 was found to block MYC expression and to synergize with BCR::ABL1 TKI in inhibiting the proliferation in the JQ1-resistant cell line K562. Furthermore, BRD4 degradation was found to overcome osteoblast-induced TKI resistance of CML LSC in a co-culture system and to block interferon-gamma-induced upregulation of the checkpoint antigen PD-L1 in LSC. Finally, dBET6 was found to suppress the in vitro survival of CML LSC and their engraftment in NSG mice. Together, targeting of BRD4 and MYC through BET degradation sensitizes CML cells against BCR::ABL1 TKI and is a potent approach to overcome multiple forms of drug resistance in CML LSC.

• MeSH
• bcr-abl fúzové proteiny MeSH
• blastická krize farmakoterapie   MeSH
• chemorezistence MeSH
• chronická myeloidní leukemie * farmakoterapie   genetika   metabolismus   MeSH
• inhibitory proteinkinas farmakologie   terapeutické užití   MeSH
• jaderné proteiny * genetika   MeSH
• kmenové buňky MeSH
• lidé MeSH
• myši MeSH
• nádorové buněčné linie MeSH
• proteiny buněčného cyklu MeSH
• protoonkogenní proteiny c-myc MeSH
• transkripční faktory genetika   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• bcr-abl fúzové proteiny MeSH
• BRD4 protein, human MeSH Prohlížeč
• inhibitory proteinkinas MeSH
• jaderné proteiny * MeSH
• MYC protein, human MeSH Prohlížeč
• proteiny buněčného cyklu MeSH
• protoonkogenní proteiny c-myc MeSH
• transkripční faktory MeSH

Ponatinib is a tyrosine kinase inhibitor (TKI) directed against BCR-ABL1 which is successfully used in patients with BCR-ABL1 T315I+ chronic myeloid leukemia (CML). However, BCR-ABL1 compound mutations may develop during therapy in these patients and may lead to drug resistance. Asciminib is a novel drug capable of targeting most BCR-ABL1 mutant-forms, including BCR-ABL1T315I, but remains ineffective against most BCR-ABL1T315I+ compound mutation-bearing sub-clones. We demonstrate that asciminib synergizes with ponatinib in inducing growth-arrest and apoptosis in patient-derived CML cell lines and murine Ba/F3 cells harboring BCR-ABL1 T315I or T315I-including compound mutations. Asciminib and ponatinib also produced cooperative effects on CRKL phosphorylation in BCR-ABL1-transformed cells. The growth-inhibitory effects of the drug combination 'asciminib+ponatinib' was further enhanced by hydroxyurea (HU), a drug which has lately been described to suppresses the proliferation of BCR-ABL1 T315I+ CML cells. Cooperative drug effects were also observed in patient-derived CML cells. Most importantly, we were able to show that the combinations 'asciminib+ponatinib' and 'asciminib+ponatinib+HU' produce synergistic apoptosis-inducing effects in CD34+/CD38- CML stem cells obtained from patients with chronic phase CML or BCR-ABL1 T315I+ CML blast phase. Together, asciminib, ponatinib and HU synergize in producing anti-leukemic effects in multi-resistant CML cells, including cells harboring T315I+ BCR-ABL1 compound mutations and CML stem cells. The clinical efficacy of this TKI combination needs to be evaluated within the frame of upcoming clinical trials.

• Klíčová slova
• BCR-ABL1 compound mutations, BCR-ABL1T315I, CML, asciminib, drug combinations, hydroxyurea, leukemic stem cells, ponatinib,
• Publikační typ
• časopisecké články MeSH