Multi step tumorigenesis, control of cell cycle entry

癌变是由多种共同作用的遗传损伤引起的，导致细胞信号和细胞周期限制点控制的渐进性放松。这些突变会导致癌基因激活或肿瘤抑制基因功能丧失。然而，这些突变基因在恶性细胞转化中协同作用的机制在很大程度上尚不清楚。我们的实验室已经证明，致癌损伤的合作涉及多种信号的整合，这些信号集中在细胞周期依赖的激酶复合体的调节上。在这里，我们建议研究c-myc癌基因与激活的RAS/RAF信号协同作用的分子机制。C-myc癌基因在人类癌症中经常被激活，是一种有效的增殖和凋亡诱导剂。Myc诱导细胞增殖的一个重要步骤是激活Cyclin E依赖的激酶(Cyclin E/CDK2)。在组织培养中，我们利用遗传学和生物化学的方法，最近得到了一个令人惊讶的发现：c-myc激活细胞周期蛋白E/CDK2需要D细胞周期蛋白具有隔离G1细胞周期抑制因子p27Kip1和p21Cip1(Ckis)的能力。我们现在建议研究D细胞周期蛋白封闭CKI的能力是否在激活c-myc诱导完整生物体的细胞分裂中起重要作用。此外，我们计划支持这样的假设，即D细胞周期蛋白对CKI的隔离可能在器官发育和多步致癌过程中发挥重要作用。这项工作将为开发基于信号通路的人类癌症治疗策略提供洞察力。

Carcinogenesis is caused by multiple co-operating genetic lesions leading to a progressive deregulation of cellular signaling and cell cycle restriction point control. The mutations involved result in oncogene activation or loss of tumor-suppressor gene function. However, the mechanisms by which these mutant genes co-operate in malignant cell transformation are largely unknown. Our laboratory has shown that the co-operation of oncogenic lesions involves integration of multiple signals converging on the regulation of cell cycle-dependent kinase complexes. Here we propose to investigate the molecular mechanisms by which the c-myc oncogene co-operates with activated Ras/Raf signaling. The c-myc oncogene is frequently activated in human cancer and is a potent inducer of proliferation and apoptosis. One essential step in Myc-induced proliferation is the activation of Cyclin E-dependent kinase (Cyclin E/Cdk2). Using genetic and biochemical approaches in tissue culture, we recently made the surprising finding that activation of cyclin E/Cdk2 by c-myc requires the ability of D cyclins to sequester Gl cell cycle inhibitors p27Kip1 and p21Cip1 (Ckis). We now propose to investigate whether the capability of D cyclins to sequester Ckis plays an important role in the induction of cell division by activated c-myc in an intact organism. Moreover, we plan to tea the hypothesis that sequestration of Ckis by D cyclins may play a significant role in organ development and during multi-step carcinogenesis. This work will provide insight into developing signaling pathway-based strategies for cancer therapy in humans.