Study of Ras-Mediated Apoptosis

描述（由申请人提供）：抗癌治疗的一个长期教条是，此类治疗选择性地靶向快速分裂的细胞。然而，这一基本原理并不令人满意，因为一些可治愈的癌症可能生长相对缓慢，许多快速分裂的癌细胞对化疗有抗性。近年来，已经研究了调节细胞凋亡的分子机制，并且已经出现的证据表明，作为肿瘤发展的结果，调节细胞凋亡的信号级联的扰动调节癌细胞对促细胞凋亡治疗的敏感性。因此，定义和操纵肿瘤细胞的凋亡阈值将进一步加深我们对人类癌症的病因和发病机制的理解，从而允许开发更有效的治疗方法。 我们已经证明，Ras，作为一个信号转导，调节两个不同的和相反的生物过程：细胞增殖和凋亡。在正常生长条件下，Ras传递促有丝分裂信号以促进细胞分化/增殖。在内源性PKC被抑制的条件下，相同的Ras被重新定向以参与凋亡过程。我们还证明了Ras从各种凋亡途径募集信号。Bcl-2保护细胞免受Ras介导的细胞死亡。 在本研究中，我们设计了一系列关键性的实验来研究Ras介导的细胞凋亡的机制。例如，使用反义寡核苷酸技术或siRNA系统，我们将确定哪些PKC亚型参与这一过程。采用ras突变体，优先激活Ras途径之一，我们能够剖析Ras信号转导和识别下游凋亡效应。此外，使用各种bcl-2突变体，我们能够确定Bcl-2如何干扰Ras介导的细胞凋亡。 我们的研究，使用分子和细胞技术，将针对三个特定的目标：（1）确定Ras介导的细胞凋亡的调节信号;（2）确定Ras介导的细胞凋亡过程的下游效应物;（3）确定Bcl-2在Ras启动的细胞凋亡中的抗凋亡功能。总之，这些实验将有助于我们进一步了解Ras介导的细胞凋亡是如何调节的。这种理解旨在转化为针对含有致癌ras的肿瘤的癌症治疗的新策略。

DESCRIPTION (provided by applicant): One long-standing dogma of anticancer therapies has been that such treatments selectively target rapidly-dividing cells. However, this rationale is not satisfactory, as some curable cancers may grow relatively slowly and many rapidly dividing cancer cells are resistant to antineoplastic therapies. In recent years, the molecular mechanisms regulating apoptosis have been investigated, and evidence has emerged indicating that perturbation of the signaling cascades regulating apoptosis, as a result of tumor development, regulates the sensitivity of cancer cells to pro-apoptotic treatments. Therefore, defining and manipulating the apoptotic thresholds of neoplastic cells will further our understanding of the etiology and pathogenesis of human cancer and accordingly permit the development of more efficient treatments. We have demonstrated that Ras, as a signal transducer, regulates two distinct and opposite biological processes: cell proliferation and apoptosis. Under normal growth conditions, Ras transmits mitogenic signals to promote cell differentiation/proliferation. Under the conditions in which endogenous PKC is suppressed, the same Ras is re-directed to participate in the apoptotic process. We also demonstrated that Ras recruits signals from various apoptotic pathways. Bcl-2 protects cells against Ras-mediated cell death. In this proposal, we design a number of critical experiments to study the mechanisms of Ras- mediated apoptosis. For example, using antisense oligo technique or siRNA system, we will determine which PKC isoforms are involved in this process. Employing ras mutants that preferentially activate one of Ras pathways, we are able to dissect Ras signaling and identify the downstream apoptotic effectors. Also, using various bcl-2 mutants, we are able to determine how Bcl-2 interferes with Ras-mediated apoptosis. Our studies, using molecular and cellular techniques, will be directed at three specific aims: (1) to determine the signals in the regulation of Ras-mediated apoptosis; (2) to define the downstream effectors of Ras which mediate the apoptotic process; and (3) to determine the anti-apoptotic function of Bcl-2 in Ras-initiated apoptosis. Overall, the experiments will help us to further understand how Ras-mediated apoptosis is regulated. Such understanding is aimed to translate into new strategy for cancer therapy targeting tumors containing oncogenic ras.