Department of Medicine, Division of Hematology/Oncology, Northwestern University Feinberg School of Medicine and the Robert H. Lurie Comprehensive Cancer Center, Chicago, IL, USA.
Blood. 2011 Jul 28;118(4):1052-61. doi: 10.1182/blood-2011-03-340109. Epub 2011 May 31.
The RAS/RAF/MEK/ERK signaling pathway has been largely unexplored as a potential therapeutic target in lymphoma. The novel 2nd generation anti-MEK small molecule, AZD6244, down-regulated its direct downstream target, phospho-ERK (pERK) in germinal center and nongerminal center diffuse large B-cell lymphoma (DLBCL) cell lines and primary cells. Similar decreased pERK levels were noted despite constitutive activation (CA) of MEK. Consequently, several lymphoma-related ERK substrates were down-regulated by AZD6244 including MCT-1, c-Myc, Bcl-2, Mcl-1, and CDK1/2. AZD6244 induced time- and dose-dependent antiproliferation and apoptosis in all DLBCL cell lines and fresh/primary cells (IC(50) 100nM-300nM). Furthermore, AZD6244 resulted in significantly less tumor compared with control in an in vivo DLBCL SCID xenograft model. Cell death was associated with cleaved PARP, caspases-8, -9, and -3, and apoptosis was caspase-dependent. In addition, there was stabilization of FoxO3a, activation of BIM and PUMA, and a significant decrease in c-Myc transcripts. Moreover, siRNA knockdown of BIM abrogated AZD6244-related apoptosis, while shRNA knockdown of ERK minimally sensitized cells. Finally, manipulation of AKT with transfection of OCI-LY3 cells with CA-AKT or through chemical inhibition (LY294002) had minimal effect on AZD6244-induced cell death. Altogether, these findings show that the novel anti-MEK agent, AZD6244, induced apoptosis in DLBCL and that cell death was BIM-dependent.
RAS/RAF/MEK/ERK 信号通路作为淋巴瘤潜在治疗靶点的研究尚不多见。新型第二代抗 MEK 小分子 AZD6244 可下调生发中心和非生发中心弥漫性大 B 细胞淋巴瘤（DLBCL）细胞系和原代细胞中磷酸化 ERK（pERK）的直接下游靶点。尽管 MEK 持续激活（CA），但仍观察到 pERK 水平降低。因此，AZD6244 下调了几种与淋巴瘤相关的 ERK 底物，包括 MCT-1、c-Myc、Bcl-2、Mcl-1 和 CDK1/2。AZD6244 在所有 DLBCL 细胞系和新鲜/原代细胞中诱导时间和剂量依赖性增殖抑制和凋亡（IC50 为 100nM-300nM）。此外，与对照组相比，AZD6244 在体内 DLBCL SCID 异种移植模型中导致肿瘤明显减少。细胞死亡与 PARP 切割、半胱天冬酶-8、-9 和 -3 有关，凋亡依赖于半胱天冬酶。此外，FoxO3a 稳定，BIM 和 PUMA 激活，c-Myc 转录物显著减少。此外，BIM 的 siRNA 敲低可阻断 AZD6244 相关的凋亡，而 ERK 的 shRNA 敲低则使细胞最小化敏感。最后，通过转染 CA-AKT 或通过化学抑制（LY294002）用 OCI-LY3 细胞转染 AKT 对 AZD6244 诱导的细胞死亡的影响最小。总之，这些发现表明新型抗 MEK 剂 AZD6244 可诱导 DLBCL 细胞凋亡，且细胞死亡依赖于 BIM。
