Dose-response transition from cell cycle arrest to apoptosis with selective degradation of Mdm2 and p21WAF1/CIP1 in response to the novel anticancer agent, aminoflone (NSC 686288)
Dose-response transition from cell cycle arrest to apoptosis with selective degradation of Mdm2 and p21WAF1/CIP1 in response to the novel anticancer agent, aminoflone (NSC 686288)
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DOI：
10.1038/sj.onc.1210283
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发表时间：
2007-07-19
期刊：
影响因子：
8
通讯作者：
Pommier, Y.
中科院分区：
文献类型：
--
作者：
Meng, L-H;Kohn, K. W.;Pommier, Y.
氨基黄酮（AF，NSC 686288）正在开始临床试验。它诱导复制介导的组蛋白 H2AX 磷酸化、DNA-蛋白质交联并激活 p53。在这里，我们研究了 p21(CIP1/WAF1) 和 Mdm2 对 AF 的反应。尽管 p53 的稳定性和丝氨酸 15 的磷酸化随着剂量和暴露时间的增加而增加，但 Mdm2 和 p21(CIP1/WAF1) 蛋白水平表现出双相反应，因为它们在亚微摩尔剂量下积累，然后随着 AF 的增加而下降。由于 Mdm2 和 p21(CIP1/WAF1) mRNA 水平随着 AF 浓度的增加而增加，而在较高浓度下却没有降低，因此我们测量了 Mdm2 和 p21(CIP1/WAF1) 蛋白质的半衰期。 Mdm2 和 p21(CIP1/WAF1) 半衰期随着 AF 浓度的增加而缩短。蛋白酶体降解似乎是 Mdm2 和 p21(CIP1/WAF1) 减少的原因，因为 MG-132 阻止了它们的降解并揭示了 AF 诱导的 Mdm2 多泛素化。 AF 还诱导蛋白激酶 B (Akt) 激活，该激活随着 AF 浓度的增加而减弱。小干扰 RNA 对 Akt 的抑制与 Mdm2 和 p21 (CIP1/WAF1) 的下调以及细胞凋亡的增强有关。这些结果表明，细胞对 AF 的反应至少部分取决于 Mdm2 和 p21(CIP1/WAF1) 蛋白水平以及 Akt 活性，当 Mdm2 和 p21(CIP1/WAF1) 升高时导致细胞周期停滞，或者当 Mdm2 和 p21(CIP1/WAF1) 被蛋白酶体降解且 Akt 未充分激活以防止细胞凋亡时导致细胞凋亡。
Aminoflavone (AF, NSC 686288) is beginning clinical trials. It induces replication-mediated histone H2AX phosphorylation, DNA-protein crosslinks and activates p53. Here, we studied p21(CIP1/WAF1) and Mdm2 responses to AF. Although p53 stabilization and phosphorylation at serine 15 increased with dose and time of exposure, Mdm2 and p21(CIP1/WAF1) protein levels displayed a biphasic response, as they accumulated at submicromolar doses and then decreased with increasing AF. As both Mdm2 and p21(CIP1/WAF1) mRNA levels increased with AF concentration without reduction at higher concentrations, we measured the half- lives of Mdm2 and p21(CIP1/WAF1) proteins. Mdm2 and p21(CIP1/WAF1) half-lives were shortened with increasing AF concentrations. Proteasomal degradation appears responsible for the decrease of both Mdm2 and p21(CIP1/WAF1), as MG-132 prevented their degradation and revealed AF-induced Mdm2 polyubiquitylation. AF also induced protein kinase B (Akt) activation, which was reduced with increasing AF concentrations. Suppression of Akt by small interfering RNA was associated with downregulation of Mdm2 and p21(CIP1/WAF1) and with enhanced apoptosis. These results suggest that the cellular responses to AF are determined at least in part by Mdm2 and p21(CIP1/WAF1) protein levels, as well as by Akt activity, leading either to cell cycle arrest when Mdm2 and p21(CIP1/WAF1) are elevated, or to apoptosis when Mdm2 and p21(CIP1/WAF1) are degraded by the proteasome and Akt insufficiently activated to protect against apoptosis.