Overexpression of MDM2 oncoprotein has been detected in a large number of diverse human malignancies and has been shown to play both p53-dependent and p53-independent roles in oncogenesis. Our study was designed to explore the impact of MDM2 overexpression on the levels of various cell cycle regulatory proteins including Aurora kinase-B (AURK-B), CDC25C and CDK1, which are known to promote tumor progression and increase metastatic potential. Our data from human cell cycle RT2 profiler PCR array experiments revealed significant changes in the expression profile of genes that are involved in different phases of cell cycle regulation in LNCaP-MST (MDM2 transfected) prostate cancer cells. Our current study has demonstrated a significant increase in the expression level of AURK-B, CDC25C, Cyclin A2, Cyclin B and CDK1 in LNCaP-MST cells as compared with wild type LNCaP cells that were modulated by MDM2 specific inhibitor Nutlin-3. In fact, the expression levels of the above- mentioned proteins were significantly altered at both mRNA and protein levels after treating the cells with 20 μM Nutlin-3 for 24h. Additionally, the pro-apoptotic proteins including p53, p21, and Bax were elevated with the concomitant decrease in the key anti-apoptotic proteins following MDM2 inhibitor treatment. Also, Nutlin-3 treated cells demonstrated caspase-3 activation was observed with an in-vitro caspase-3 fluorescent assay performed with caspase 3/7 specific DEVD-amc substrate. Our results offer significant evidence towards the effectiveness of MDM2 inhibition in causing cell cycle arrest via blocking the transmission of signals through AURKB-CDK1 axis and inducing apoptosis in LNCaP-MST cancer cells. It is evident from our data that MDM2 overexpression probably is the primary cause for CDK1 up-regulation in the LNCaP-MST cells, which might have occurred possibly through activation of AURK-B. However, further studies in this direction should shed more light on the intracellular mechanisms involved in the regulation of Aurora kinase-B and CDK1 axis in MDM2 positive cancers.

中文翻译：

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MDM2通过Aurora Kinase-B和p21WAF1 / CIP1介导的途径调节前列腺癌细胞的细胞周期。

在许多不同的人类恶性肿瘤中都检测到了MDM2癌蛋白的过表达，并已显示其在肿瘤发生中既依赖于p53又依赖于p53。我们的研究旨在探讨MDM2过表达对各种细胞周期调节蛋白（包括Aurora激酶B（AURK-B），CDC25C和CDK1）水平的影响，已知这些蛋白可促进肿瘤进展并增加转移潜力。我们从人类细胞周期RT2分析器PCR阵列实验获得的数据揭示了LNCaP-MST（转染MDM2）前列腺癌细胞中参与细胞周期调节不同阶段的基因表达谱的显着变化。我们目前的研究表明AURK-B，CDC25C，Cyclin A2，与受MDM2特异性抑制剂Nutlin-3调节的野生型LNCaP细胞相比，LNCaP-MST细胞中的细胞周期蛋白B和CDK1。实际上，在用20μMNutlin-3处理细胞24小时后，上述蛋白的表达水平在mRNA和蛋白水平上均显着改变。此外，在MDM2抑制剂处理后，包括p53，p21和Bax在内的促凋亡蛋白升高，同时主要的抗凋亡蛋白降低。同样，用Nutlin-3处理的细胞证明了用caspase 3/7特异DEVD-amc底物进行的体外caspase-3荧光检测观察到caspase-3活化。我们的结果为通过阻止信号通过AURKB-CDK1轴的传递并诱导LNCaP-MST癌细胞凋亡而导致MDM2抑制在引起细胞周期停滞中的有效性提供了重要证据。从我们的数据中可以明显看出，MDM2过表达可能是LNCaP-MST细胞中CDK1上调的主要原因，这可能是通过激活AURK-B引起的。然而，在这个方向上的进一步研究应该更多地揭示参与MDM2阳性癌症中Aurora激酶B和CDK1轴调控的细胞内机制。