Drakos Elias, Thomaides Athanasios, Medeiros L Jeffrey, Li Jiang, Leventaki Vasiliki, Konopleva Marina, Andreeff Michael, Rassidakis George Z
Department of Hematopathology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Clin Cancer Res. 2007 Jun 1;13(11):3380-7. doi: 10.1158/1078-0432.CCR-06-2581.
p53 is frequently expressed but rarely mutated in Hodgkin and Reed-Sternberg (HRS) cells of Hodgkin's lymphoma (HL). p53 protein levels are regulated by murine double minute 2 (MDM2) through a well-established autoregulatory feedback loop. In this study, we investigated the effects of nutlin-3A, a recently developed small molecule that antagonizes MDM2 and disrupts the p53-MDM2 interaction, on p53-dependent cell cycle arrest and apoptosis in cultured HRS cells.
HL cell lines carrying wild-type (wt) or mutated p53 gene were treated with the potent MDM2 inhibitor nutlin-3A or a 150-fold less active enantiomer, nutlin-3B.
We show that nutlin-3A, but not nutlin-3B, stabilizes p53 in cultured HRS cells carrying wt p53 gene resulting in p53-dependent cell cycle arrest and apoptosis. Cell cycle arrest was associated with up-regulation of the cyclin-dependent kinase inhibitor p21. Nutlin-3A-induced apoptotic cell death was accompanied by Bax and Puma up-regulation and caspase-3 cleavage and was abrogated, in part, by inhibition of caspase-9 and caspase-3 activity. By contrast, no effects on cell cycle or apoptosis were found in HL cell lines harboring mutated p53 gene. Furthermore, combined treatment with nutlin-3A and doxorubicin revealed enhanced cytotoxicity in HRS cells with wt p53 gene. Blocking of nuclear export by leptomycin B, or inhibition of proteasome by MG132, stabilized p53 at a level comparable with that of nutlin-3A treatment in HRS cells with wt p53.
These data suggest that nutlin-3A stabilized p53 by preventing MDM2-mediated p53 degradation in HRS cells. wt p53 stabilization and activation by nutlin-3A may be a novel therapeutic approach for patients with HL.
p53在霍奇金淋巴瘤（HL）的霍奇金和里德-斯腾伯格（HRS）细胞中经常表达，但很少发生突变。p53蛋白水平通过一个成熟的自动调节反馈环由鼠双微体2（MDM2）调控。在本研究中，我们调查了nutlin-3A（一种最近研发的拮抗MDM2并破坏p53-MDM2相互作用的小分子）对培养的HRS细胞中p53依赖的细胞周期阻滞和凋亡的影响。
用强效MDM2抑制剂nutlin-3A或活性低150倍的对映体nutlin-3B处理携带野生型（wt）或突变型p53基因的HL细胞系。
我们发现，nutlin-3A而非nutlin-3B可使携带wt p53基因的培养HRS细胞中的p53稳定，导致p53依赖的细胞周期阻滞和凋亡。细胞周期阻滞与细胞周期蛋白依赖性激酶抑制剂p21的上调相关。Nutlin-3A诱导的凋亡性细胞死亡伴随着Bax和Puma上调以及caspase-3裂解，并且部分被caspase-9和caspase-3活性抑制所消除。相比之下，在携带突变型p53基因的HL细胞系中未发现对细胞周期或凋亡有影响。此外，nutlin-3A与多柔比星联合处理显示在具有wt p53基因的HRS细胞中细胞毒性增强。通过雷帕霉素B阻断核输出或通过MG132抑制蛋白酶体，可使p53在具有wt p53的HRS细胞中稳定在与nutlin-3A处理相当的水平。
这些数据表明，nutlin-3A通过防止MDM2介导的HRS细胞中p53降解来稳定p53。Nutlin-3A对wt p53的稳定和激活可能是HL患者的一种新的治疗方法。
