Division of Hematology and Bone Marrow Transplantation, Chaim Sheba Medical Center, Tel-Hashomer, Ramat Gan, Tel Aviv University, Israel.
Goldyne Savad Institute of Gene Therapy, Hebrew University Hospital, Jerusalem, Israel.
Biochem Pharmacol. 2019 Oct;168:412-428. doi: 10.1016/j.bcp.2019.07.016. Epub 2019 Jul 17.
Although having promising anti-myeloma properties, the pan-histone deacetylase inhibitor (HDACi) panobinostat lacks therapeutic activity as a single agent. The aim of the current study was to elucidate the mechanisms underlying multiple myeloma (MM) resistance to panobinostat monotherapy and to define strategies to overcome it. Sensitivity of MM cell lines and primary CD138+ cells from MM patients to panobinostat correlated with reduced expression of the chemokine receptor CXCR4, whereas overexpression of CXCR4 in MM cell lines increased their resistance to panobinostat. Decreased sensitivity to HDACi was associated with reversible G0/G1 cell growth arrest while response was characterized by apoptotic cell death. Analysis of intra-cellular signaling mediators revealed the pro-survival mTOR pathway to be regulated by CXCR4 overexpression. Combining panobinostat with mTOR inhibitor everolimus abrogated the resistance to HDACi and induced synergistic cell death. The combination of panobinostat/everolimus resulted in sustained DNA damage and irreversible suppression of proliferation accompanied by robust apoptosis. Gene expression analysis revealed distinct genetic profiles of single versus combined agent exposure. Whereas panobinostat increased the expression of the cell cycle inhibitor p21, co-treatment with everolimus abrogated the increase in p21 and synergistically downregulated the expression of DNA repair genes and mitotic checkpoint regulators. Importantly, the combination of panobinostat with everolimus effectively targeted CXCR4-expressing resistant MM cells in vivo in the BM niche. In summary, our results uncover the mechanism responsible for the strong synergistic anti-MM activity of dual HDAC and mTOR inhibition and provide the rationale for a novel potential therapeutic approach to treat MM.
尽管具有有前景的抗骨髓瘤特性，但泛组蛋白去乙酰化酶抑制剂（HDACi）panobinostat 作为单一药物缺乏治疗活性。本研究旨在阐明多发性骨髓瘤（MM）对 panobinostat 单药治疗耐药的机制，并定义克服耐药的策略。MM 细胞系和 MM 患者 CD138+原代细胞对 panobinostat 的敏感性与趋化因子受体 CXCR4 的表达降低相关，而 MM 细胞系中 CXCR4 的过表达增加了它们对 panobinostat 的耐药性。对 HDACi 的敏感性降低与可逆的 G0/G1 细胞生长停滞相关，而反应的特征是细胞凋亡。对内细胞信号转导介质的分析表明，CXCR4 的过表达调节了促生存的 mTOR 途径。将 panobinostat 与 mTOR 抑制剂 everolimus 联合使用可消除对 HDACi 的耐药性并诱导协同细胞死亡。panobinostat/everolimus 的联合使用导致持续的 DNA 损伤和不可逆转的增殖抑制，伴随着强烈的凋亡。基因表达分析揭示了单一和联合药物暴露的不同遗传特征。panobinostat 增加了细胞周期抑制剂 p21 的表达，而 everolimus 的共同处理则消除了 p21 的增加，并协同地下调了 DNA 修复基因和有丝分裂检查点调节剂的表达。重要的是，panobinostat 与 everolimus 的联合使用有效地靶向了体内 BM 龛中表达 CXCR4 的耐药 MM 细胞。总之，我们的研究结果揭示了双重 HDAC 和 mTOR 抑制对 MM 具有强大协同抗活性的机制，并为治疗 MM 的新的潜在治疗方法提供了依据。
