Rahmani Mohamed, Nguyen Tri K, Dent Paul, Grant Steven
Department of Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA.
Mol Pharmacol. 2007 Sep;72(3):788-95. doi: 10.1124/mol.106.033308. Epub 2007 Jun 26.
The effects of the multikinase inhibitor sorafenib (BAY 43-9006), an agent shown previously to induce apoptosis in human leukemia cells through inhibition of myeloid cell leukemia-1 (Mcl-1) translation, have been examined in Bcr/Abl(+) leukemia cells resistant to imatinib mesylate (IM). When administered at pharmacologically relevant concentrations (10-15 microM), sorafenib potently induced apoptosis in imatinib mesylate-resistant cells expressing high levels of Bcr/Abl, cells exhibiting a Bcr/Abl-independent, Lyn-dependent form of resistance, and CD34(+) cells obtained from imatinib-resistant patients. In addition, Ba/F3 cells expressing mutations rendering them resistant to IM (e.g., E255K, M351T) or to IM, dasatinib, and nilotinib (T315I) remained fully sensitive to sorafenib. Induction of apoptosis by sorafenib was associated with rapid and pronounced down-regulation of Mcl-1 and diminished signal transducer and activator of transcription (STAT) 5 phosphorylation and reporter activity but only very modest and delayed inactivation of the Bcr/Abl downstream target Crkl. Moreover, transfection with a constitutively active STAT5 construct partially but significantly protected cells from sorafenib lethality. Ba/F3 cells expressing Bcr/Abl mutations were as sensitive to sorafenib-induced Mcl-1 down-regulation and dephosphorylation of STAT5 and eukaryotic initiation factor 4E as wild-type cells. Finally, stable knockdown of Bcl-2-interacting mediator of cell death (Bim) with short hairpin RNA in K562 cells significantly diminished sorafenib lethality, arguing strongly for a functional role of this proapoptotic Bcl-2 family member in the lethality of this agent. Together, these findings suggest that sorafenib effectively induces apoptosis in highly imatinib-resistant chronic myelogenous leukemia cells, most likely by inhibiting or down-regulating targets (i.e., STAT5 and Mcl-1) downstream or independent of Bcr/Abl.
多激酶抑制剂索拉非尼（BAY 43 - 9006）先前已被证明可通过抑制髓样细胞白血病-1（Mcl-1）翻译诱导人白血病细胞凋亡，本研究检测了其对甲磺酸伊马替尼（IM）耐药的Bcr/Abl(+)白血病细胞的作用。当以药理学相关浓度（10 - 15 microM）给药时，索拉非尼能有效诱导高表达Bcr/Abl的甲磺酸伊马替尼耐药细胞、表现出Bcr/Abl非依赖性、Lyn依赖性耐药形式的细胞以及从伊马替尼耐药患者获得的CD34(+)细胞发生凋亡。此外，表达使其对IM耐药的突变（如E255K、M351T）或对IM、达沙替尼和尼罗替尼耐药的突变（T315I）的Ba/F3细胞对索拉非尼仍完全敏感。索拉非尼诱导凋亡与Mcl-1迅速且显著下调、信号转导及转录激活因子（STAT）5磷酸化和报告基因活性降低有关，但Bcr/Abl下游靶点Crkl的失活非常轻微且延迟。此外，用组成型活性STAT5构建体转染可部分但显著保护细胞免受索拉非尼致死作用。表达Bcr/Abl突变的Ba/F3细胞对索拉非尼诱导的Mcl-1下调、STAT5去磷酸化和真核起始因子4E的敏感性与野生型细胞相同。最后，在K562细胞中用短发夹RNA稳定敲低细胞死亡的Bcl-2相互作用介质（Bim）可显著降低索拉非尼的致死作用，有力地证明了这种促凋亡Bcl-2家族成员在该药物致死作用中的功能作用。总之，这些发现表明索拉非尼能有效诱导高度伊马替尼耐药的慢性粒细胞白血病细胞凋亡，最可能是通过抑制或下调Bcr/Abl下游或独立的靶点（即STAT5和Mcl-1）。
