Resistance of chronic myeloid leukemia (CML) to tyrosine kinase inhibitor imatinib mesylate (IM) is most often due to point mutations in the Bcr-Abl fusion gene. T315I mutation (resulting in substitution of Ile for a Thr residue at the “gatekeeper” position 315) raises particular concern, because it also provides resistance to second-generation kinase inhibitors already approved for clinical use (nilotinib and dasatinib). Much effort is therefore focused on alternative molecular-based strategies. Previous studies proved that binding to 14-3-3 scaffolding proteins leads to cytoplasmic compartmentalization and suppression of proapoptotic and antiproliferative signals associated with Bcr-Abl protein kinase, hence contributing to leukemic clone expansion. Here we investigated the effect of 14-3-3 inhibition disruption on hematopoietic cells expressing the IM-sensitive wild type Bcr-Abl and the IM-resistant T315I mutation. Using a virtual screening protocol and docking simulations, we identified a nonpeptidic inhibitor of 14-3-3, named BV02, that exhibits a remarkable cytotoxicity against both cell types. c-Abl release from 14-3-3σ, promoting its relocation to nuclear compartment (where it triggers transcription of p73-dependent proapoptotic genes) and to mitochondrial membranes (where it induces the loss of mitochondrial transmembrane potential) combined with c-Abl enhanced association with caspase 9 (a critical step of sequential caspase activation further contributing to c-Abl pro-apoptotic function) has a prominent role in the effect of BV02 on Bcr-Abl-expressing cells. In conclusion, BV02 may be considered as a treatment option for CML and, in particular, for more advanced phases of the disease that developed IM resistance as a consequence of Bcr-Abl point mutations.
慢性髓性白血病(CML)对
酪氨酸激酶
抑制剂甲磺酸伊马替尼(IM)的耐药性最常见于Bcr-Abl融合
基因的点突变。T315I突变(导致 "守门员 "315位上的Ile取代Thr残基)尤其令人担忧,因为它也会对已批准临床使用的第二代激酶
抑制剂(
尼洛替尼和
达沙替尼)产生耐药性。因此,人们将大量精力集中在基于分子的替代策略上。以前的研究证明,与 14-3-3 蛋白支架的结合会导致细胞质分区,抑制与 Bcr-Abl 蛋白激酶相关的促凋亡和抗增殖信号,从而导致白血病克隆扩增。在这里,我们研究了 14-3-3 抑制干扰对表达 IM 敏感野生型 Bcr-Abl 和 IM 抗性 T315I 突变的造血细胞的影响。通过虚拟筛选方案和对接模拟,我们发现了一种名为 BV02 的 14-3-3 非肽
抑制剂,它对这两种细胞类型都有显著的细胞毒性。BV02对Bcr-Abl表达细胞的作用中,c-Abl从14-3-3σ中释放出来,促进其迁移到核区(在核区它能触发依赖p73的促凋亡
基因的转录)和线粒体膜(在线粒体膜它能诱导线粒体跨膜电位的丧失),再加上c-Abl与caspase 9的关联增强(caspase顺序激活的关键步骤,进一步促进了c-Abl的促凋亡功能)。总之,BV02 可被视为治疗 CML 的一种选择,尤其是治疗因 Bcr-Abl 点突变而产生 IM 抗性的晚期 CML。