TUMOR SUPPRESSOR RB FAMILY/PRB2 IN MEDULLOBLASTOMA

髓母细胞瘤中的肿瘤抑制因子 RB 家族/PRB2

• 批准号: 6825071
• 负责人: Antonio Giordano
• 金额: $ 25.98万
• 依托单位: TEMPLE UNIV OF THE COMMONWEALTH
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-09-30 至 2008-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6825071
• 关键词: Papovaviridae; cell cycle proteins; cellular oncology; disease /disorder model; gene mutation; genetically modified animals; human tissue; immunocytochemistry; immunoprecipitation; laboratory mouse; medulloblastoma; molecular oncology; neoplastic growth; pathologic process; protein structure function; retinoblastoma protein; tissue /cell culture; tumor antigens; tumor suppressor genes; virus antigen; virus related neoplasm /cancer; western blottings

Project #2: Tumor Suppressor Rb Family/pRb2 in Medulloblastoma. The human neurotropic virus, JCV, is widespread in the human population and is the established etiologic agent of the fatal demyelinating disease of the central nervous system (CNS), Progressive Multifocal Leukoencephalopathy (PML). Like other papovaviruses, the JCV genome consists of circular double-stranded DNA that is separated into early and late coding sequences by the viral cell type-specific regulatory region. The viral early gene, T-antigen has important regulatory functions in orchestrating the viral lytic cycle and possesses the ability to interact with several important cellular proteins including the tumor suppressor protein, pRb pointing to the oncogenic potential of this virus. In support of this notion, earlier studies have revealed that JCV has the ability to induce neural origin tumors in several animal models. More recently, in collaboration with Dr. Khalili (Leader Project #1), a transgenic animal which developed tumor from external granular layer of cerebellun_ mimicking human medulloblastoma was created. The transgene which express T-antigen exhibited the ability to interact with pRb as well as p53 and that may de-regulate cell cycle pathway leading to evolution of tumor However, the underlying mechanism of transactivation of these two tumor suppressors, particularly pRb remains unknown. To better understand the molecular events involved in the genesis of T-antigen inducec medulloblastomas, we have developed cell lines from mouse tumors. Interestingly, similar to tumor tissue, not all cells expressed T-antigen, leading to speculation that as tumor cells develop, expression of T-antigen may no longer be needed and expression of T-antigen becomes silent. Loss of T-antigen expression which is concomitant with the lack of the hypophosphorylated form (active form) of pRb2/pl30 suggests that at the early stage of tumorigenesis, expression of T-antigen and its association with pRb2/pl30 functionally inactivates this protein, while at the latter stage of tumor development, the active form of pRb2/pl30 may be lost due to an increase in the level of phosphorylation of pRb2/pl30 and/or enhancement in its proteolytic degradation. The observation on murine medulloblastoma tumors is in accord with our earlier observation on human medulloblastoma that demonstrated detection of active pRb2/p 130 in JCV-associated medulloblastomas expressing T-antigen, but not in tumor cells lacking JCV and its early protein. As the biological function ot pRb2/pl30 is dictated at several stage, most notably through its partnership with p27 Kip1 and the E2F family, in this research proposal we will utilize the mouse model of medulloblastoma as well as a collection of well-characterized human medulloblastomas to decipher the molecular events involved in dysregulation o1 pRb2/pl30 during various stages of the cell cycle in vitro and during the course of tumor formation in the cerebellum of experimental animals. The outcome should provide useful information for therapeutic intervention.

项目＃2：肿瘤抑制RB家族/PRB2在髓母细胞瘤中。 人类人群中的人类神经性病毒JCV是普遍存在的，是中枢神经系统致命性脱髓鞘疾病（CNS），进行性多灶性白细胞症（PML）的既定病因。与其他乳木瓜病毒一样，JCV基因组由圆形双链DNA组成，该DNA被病毒细胞类型特异性调节区分为早期和晚期编码序列。病毒早期基因T-抗原具有重要的调节功能，在策划病毒裂解周期，并具有与几种重要的细胞蛋白相互作用的能力，包括肿瘤抑制蛋白，PRB指向 该病毒的致癌潜力。为了支持这一概念，早期的研究表明，JCV具有在几种动物模型中诱导神经起源肿瘤的能力。最近，创建了一种转基因动物Khalili（领导者项目＃1）的合作，该动物从小脑外部颗粒层开发了肿瘤，模仿了人类髓母细胞瘤。表达T-抗原的转基因表现出与PRB相互作用以及p53相互作用的能力，并且可能取消调节细胞周期途径，导致肿瘤的演变，但是，这两个肿瘤抑制剂的反式激活的潜在机制，尤其是PRB仍然未知。为了更好地了解T-抗原诱导型髓母细胞瘤的发生所涉及的分子事件，我们已经从小鼠肿瘤中发展出细胞系。有趣的是，类似于肿瘤组织，并非所有细胞都表达T-抗原，导致人们猜测随着肿瘤细胞的发展，可能不再需要T-抗原的表达，而T-抗原的表达变得沉默。 T-抗原表达的丧失与缺乏prb2/pl30的低磷酸化形式（活性形式）同时表明，在肿瘤发生的早期，T-抗原的表达及其与PRB2/PL30的关系在功能上 使该蛋白质失活，而在肿瘤发育的后期，由于PRB2/PL30的磷酸化水平增加，PRB2/PL30的活性形式可能会丢失。对鼠类髓母细胞瘤肿瘤的观察结果与我们对人类髓母细胞瘤的早期观察结果一致，该观察结果证明了在JCV相关的表达T-抗原的JCV相关的髓母细胞瘤中检测到活性PRB2/P 130，但在缺乏JCV及其早期蛋白质的肿瘤细胞中发现了肿瘤细胞中。由于PRB2/PL30的生物学功能是在几个阶段决定的，最著名的是通过其与P27 KIP1和E2F家族的伙伴关系，在这项研究建议中，我们将利用髓母细胞瘤的鼠标模型，以及在含有较高的髓质体中涉及的分子prb2/prb2 prb2/prb2 prb2/prb2 prb2 prb2/prb2 prb2/prb2 prb的分解过程中prb2/prb2 prb2 prb2/prb2 prb2/prb2/pl。实验动物小脑中的肿瘤形成过程。结果应为治疗干预提供有用的信息。