Russo Angelo J, Magro Pellegrino G, Hu Zhen, Li Wei-Wei, Peters Rowayda, Mandola Jennifer, Banerjee Debabrata, Bertino Joseph R
The Cancer Institute of New Jersey, Robert Wood Johnson School of Medicine, University of Medicine and Dentistry of New Jersey, New Brunswick, New Jersey 08903, USA.
Cancer Res. 2006 Jul 15;66(14):7253-60. doi: 10.1158/0008-5472.CAN-05-3725.
The E2F transcription factors play a critical role in coordinating transcription of specific genes essential for G1-S transition. In early G1, the retinoblastoma protein (pRB) becomes phosphorylated by cyclin-dependent kinases, disrupting pRB binding to E2F-1-3, allowing "free" E2F to regulate genes involved in proliferation. In the present study, we used a tetracycline E2F-1 inducible U2OS osteosarcoma cell line to investigate the effect of increasing levels of E2F-1 on the cytotoxicity of various chemotherapeutic drugs. Upon overexpression of E2F-1, there was no detectable change in cytotoxicity to doxorubicin, cisplatin, 5-fluorouracil, or etoposide. In contrast, overexpression of E2F-1 resulted in a marked increase in sensitivity to vinblastine and paclitaxel, drugs that are known to be more effective against cells in M phase. Therefore, we investigated the effect of E2F-1 overexpression on proteins regulating the G2-M transition and M phase, in particular cyclin B1 and cdc2 kinase. Cyclin B1 mRNA and protein levels increased within 24 hours of E2F1 induction together with an increase in associated cdc2 kinase activity. Overexpression of cyclin B1 also resulted in a specific increase in sensitivity to paclitaxel and an increase in the cellular growth rate. Knockdown of cyclin B1 using an RNA interference oligo resulted in a slower cellular growth rate and an increase in resistance to paclitaxel. These studies add support to recent reports that show E2F regulates genes involved in mitotic entry and exit and allow the suggestion that mitotic inhibitors may have selective effects in tumors that overexpress E2F-1.
E2F转录因子在协调对G1-S期转换至关重要的特定基因的转录过程中发挥着关键作用。在G1早期，视网膜母细胞瘤蛋白（pRB）被细胞周期蛋白依赖性激酶磷酸化，破坏pRB与E2F-1-3的结合，使“游离”的E2F能够调控参与增殖的基因。在本研究中，我们使用四环素诱导型E2F-1的U2OS骨肉瘤细胞系来研究E2F-1水平升高对各种化疗药物细胞毒性的影响。E2F-1过表达后，对阿霉素、顺铂、5-氟尿嘧啶或依托泊苷的细胞毒性没有可检测到的变化。相比之下،E2F-1过表达导致对长春碱和紫杉醇的敏感性显著增加，这两种药物已知对M期细胞更有效。因此，我们研究了E2F-1过表达对调控G2-M期转换和M期的蛋白质的影响，特别是细胞周期蛋白B1和cdc2激酶。在E2F1诱导后24小时内，细胞周期蛋白B1的mRNA和蛋白水平增加，同时相关的cdc2激酶活性也增加。细胞周期蛋白B1的过表达还导致对紫杉醇的敏感性特异性增加以及细胞生长速率提高。使用RNA干扰寡核苷酸敲低细胞周期蛋白B1导致细胞生长速率减慢和对紫杉醇的抗性增加。这些研究为最近的报道提供了支持，这些报道表明E2F调控参与有丝分裂进出的基因，并提示有丝分裂抑制剂可能对过表达E2F-1的肿瘤具有选择性作用。
