Regulation of Myc-Mediated Tumorigenesis

描述(由申请人提供)：c-Myc转录因子是细胞周期进展所必需的，是包括淋巴瘤在内的人类癌症中最常见的过表达癌基因之一。由于Myc尚未被证明是一个合适的药物靶点，因此对识别和表征调节Myc功能的蛋白质非常有必要和兴趣。MDM2(二)结合蛋白(MTBP)在酵母双杂交中被鉴定为与MDM2结合的蛋白质，MDM2是肿瘤抑制基因P53的调节因子。在肿瘤细胞系中的过表达研究表明，MTBP影响MDM2 E3泛素连接酶的活性，从而影响p53的表达。然而，与p53缺失挽救的MDM2缺失的胚胎致死性不同，MTBP缺失的胚胎致死性并不因p53的缺失而挽救。这一点以及MTBP和MDM2缺陷小鼠之间的其他差异表明，MTBP可能不调节MDM2，我们的初步数据也不支持MTBP在MDM2调节中的作用。具体地说，MTBP缺陷小鼠的B细胞没有改变MDM2的表达或功能，但确实减少了Myc介导的增殖，并显著延迟了Myc介导的B细胞淋巴瘤的发展。此外，小鼠和人类淋巴瘤表达的MTBP水平增加。这些数据表明，MTBP可能参与了Myc诱导的淋巴肿大，并且这是独立于MDM2的。质谱学数据揭示了MTBP与据报道调节Myc转化和凋亡功能的蛋白质之间的新关联。总之，我们的数据为MTBP功能的新机制提供了洞察力，并揭示了Myc潜在的新调节因子。因此，本研究的目的是阐明MTBP的功能及其在Myc诱导的B细胞淋巴瘤发生发展中的作用。我们推测，MTBP调节Myc的促生长功能，从而参与Myc诱导的肿瘤发生。为了检验这一假设，我们提出了两个具体的目标，每个目标都将利用多种互补的方法。目标1中的实验将评估MTBP调节Myc的生化机制。目标2中的实验将确定MTBP是否具有致癌特性，以及MTBP在Myc诱导的增殖、凋亡、转化和淋巴瘤细胞生长和进展中的需求和贡献。我们提出的研究将为Myc诱导的淋巴瘤的发展提供重要的新见解，并显著增加我们对MTBP在肿瘤发生中的作用的理解。我们的研究结果最终将导致改进的治疗干预策略，用于治疗非霍奇金淋巴瘤和70%过度表达Myc的人类恶性肿瘤。 公共卫生相关性：MYC是人类癌症中最常见的过度表达的癌基因，与肿瘤的发生和发展有关。MYC在淋巴瘤中经常过度表达，这是美国女性和男性癌症死亡的主要原因之一。关于Myc潜在的新调节剂的研究结果最终将导致改善淋巴瘤以及70%过度表达Myc的人类恶性肿瘤的干预策略。

DESCRIPTION (provided by applicant): The c-Myc transcription factor that is necessary for cell cycle progression is one of the most frequently overexpressed oncogenes in human cancer, including lymphoma. Since Myc has of yet not proven to be a suitable drug target, there is great need and interest in identifying and characterizing proteins that regulate Myc functions. Mdm2 (Two) Binding Protein (MTBP) was identified in a yeast-two-hybrid as a protein that bound to Mdm2, a regulator of the tumor suppressor p53. Overexpression studies in tumor cell lines showed MTBP influenced Mdm2 E3 ubiquitin ligase activity and consequently p53 expression. However, in contrast to the embryonic lethality of Mdm2 deletion that is rescued with p53 deletion, MTBP-null embryonic lethality was not rescued with loss of p53. This and other differences between MTBP- and Mdm2-deficient mice suggest that MTBP may not regulate Mdm2, and our preliminary data also does not support a role for MTBP in Mdm2 regulation. Specifically, B cells from mice deficient in MTBP did not have altered Mdm2 expression or function, but did have reduced Myc-mediated proliferation and a significant delay in Myc-mediated B cell lymphoma development. Moreover, murine and human lymphomas expressed increased levels of MTBP. These data suggest that MTBP may contribute to Myc-induced lymphomagenesis and that this is independent of Mdm2. Mass spectrometry data revealed a novel association of MTBP with proteins that are reported to modulate transforming and apoptotic functions of Myc. Together our data provide insight into a novel mechanism of MTBP function and uncovered a potentially novel regulator of Myc. Therefore the objective of this proposal is to elucidate MTBP function and its role in Myc-induced B cell lymphoma development and progression. We hypothesize that MTBP regulates the growth promoting functions of Myc and thereby contributes to Myc-induced tumorigenesis. To test this hypothesis, we propose two Specific Aims, each of which will utilize multiple complementary approaches. Experiments in Aim 1 will assess the biochemical mechanism of Myc regulation by MTBP. Experiments in Aim 2 will determine whether MTBP has oncogenic properties and the requirements and contribution of MTBP in Myc-induced proliferation, apoptosis, transformation, and lymphoma cell growth and progression. Our proposed studies will provide important new insights into Myc-induced lymphoma development and significantly increase our understanding of the role MTBP has in tumorigenesis. Results from our studies should ultimately lead to improved therapeutic intervention strategies for the treatment of non-Hodgkin's lymphoma and the 70% of human malignancies that overexpress Myc. PUBLIC HEALTH RELEVANCE: Myc is the most frequently overexpressed oncogene in human cancer and is linked to tumor development and progression. Myc is frequently overexpressed in lymphomas, which is one of the leading causes of cancer deaths in the United States for both women and men. Results from the studies proposed on a potential novel regulator of Myc should ultimately lead to improved intervention strategies for the treatment of lymphoma, as well as 70% of the human malignancies that overexpress Myc.