Oncogene-Induced Evasion from Apoptosis

描述（由申请人提供）：逃避细胞凋亡是癌症进展中研究较少的标志之一。Bcr-Abl癌基因促进造血细胞不依赖细胞因子的生长，从而促进造血细胞增殖和逃避凋亡。这一过程最终导致慢性髓性白血病（CML）。我们最近报道了Bcr-Abl表达促进体外细胞凋亡逃避的一种机制是通过抑制foxo3a依赖性的几种促凋亡因子的转录，包括TRAIL、Bim和Hrk。本研究的总体目标是阐明FOXO3a及其下游靶点TRAIL、Bim和Hrk在bcr - abl诱导的细胞凋亡逃避中的生理作用，以及它们在bcr - abl诱导的骨髓增生性疾病（MPD）中的参与作用。我们假设foxo3a依赖性、Bcr-Abl诱导的TRAIL、Bim和Hrk调控是体内调节Bcr-Abl致瘤活性的新机制。此外，我们假设TRAIL、Bim和Hrk的协同调节促进了bcr - abl诱导的白血病。最后，我们提出Bcr-Abl通过诱导FOXO3a的蛋白酶体降解来支持逃避细胞凋亡。因此，我们假设靶向FOXO3a可能是一种诱导Bcr-Abl转化细胞肿瘤选择性凋亡的治疗策略。本建议的具体目标是：1)确定FOXO3a转录因子活性及其对TRAIL表达的调控在促进Bcr-Abl诱导的造血细胞转化中的生物学意义；2)确定Bcr-Abl是否也以FOXO3a依赖的方式调控Bim和Hrk的表达，作为白血病造血细胞逃避凋亡的机制；3)确定蛋白酶体通路在Bcr-Abl介导的FOXO3a转录因子下调中的作用。我们将利用多种方法开展这些研究，包括分子生物学、细胞生物学、小鼠致瘤性模型和bcr - abl诱导白血病的小鼠模型。综上所述，这些研究将有助于更好地理解白血病发生的机制，并确定治疗CML的新分子靶点。考虑到对目前使用的STI-571疗法的耐药性正在成为一个普遍问题，寻找新的靶点尤为重要。

DESCRIPTION (provided by applicant): Evasion from apoptosis is one of the less investigated hallmarks of cancer progression. The Bcr-Abl oncogene facilitates cytokine-independent growth of hematopoietic cells, which results in their enhanced proliferation and evasion from apoptosis. This process ultimately leads to chronic myeloid leukemia (CML). We recently reported that one mechanism by which Bcr-Abl expression promotes evasion from apoptosis in vitro is through the inhibition of FOXO3a-dependent transcription of several pro-apoptotic factors including TRAIL, as well as Bim and Hrk. The overall objective of this proposal is to elucidate the physiological role of FOXO3a and its downstream targets, TRAIL, Bim and Hrk, in Bcr-Abl-induced evasion from apoptosis and their involvement in Bcr-Abl-induced myeloproliferative disorders (MPD) in vivo. As is detailed in this proposal, we hypothesize that FOXO3a-dependent, Bcr-Abl-induced regulation of TRAIL, Bim and Hrk is a novel mechanism for regulating the tumorigenic activity of Bcr-Abl in vivo. Additionally, we posit that coordinate regulation of TRAIL, Bim and Hrk promotes Bcr-Abl-induced leukemia. Finally, we propose that Bcr-Abl supports evasion from apoptosis by instigating the proteasomal degradation of FOXO3a. Therefore, we hypothesize that targeting FOXO3a may be a therapeutic strategy to induce tumor-selective apoptosis in Bcr-Abl transformed cells. The Specific Aims of this proposal are: 1) to determine the biological significance of FOXO3a transcription factor activity and consequent regulation of TRAIL expression in promoting Bcr-Abl-induced transformation of hematopoietic cells, 2) to determine whether Bcr-Abl also regulates Bim and Hrk expression in a FOXO3a dependent manner as a mechanism for apoptotic evasion in leukemic hematopoietic cells, 3) to determine the role of the proteasomal pathway in Bcr-Abl-mediated down-regulation of FOXO3a transcription factor. We will utilize diverse approaches to carry out these studies including molecular biology, cell biology, murine models for tumorigenicity and murine model for Bcr-Abl-induced leukemia. Taken together, these studies will lead to a better understanding of the mechanisms involved in leukemogenesis in general and to the characterization of novel molecular targets for treatment of CML. Finding a novel target is especially critical given that resistance to the currently used STI-571 therapy is emerging as a common problem.