MDM2 AS A NEGATIVE REGULATOR OF P21 WAF1/CIP1

项目描述（申请人提供）：本项目的长期目标是确定MDM 2癌基因在p21调控中的作用，评估MDM 2和p21作为癌症化学预防和化疗新靶点的潜力，并将这些发现转化为更合理的人类癌症预防和治疗。p21的表达受p53的调控。然而，p21也受到p53非依赖性途径的调节。MDM 2癌基因在许多人类癌症中过表达，MDM 2水平与肿瘤进展和预后不良相关。MDM 2在调节p53稳定性和活性中起作用。此外，MDM 2还具有p53非依赖性活性，这可能与其致癌特性有关。初步研究表明，MDM 2在p21的调节中具有重要作用。用抗MDM 2反义寡核苷酸或靶向MDM 2的siRNA抑制MDM 2显著提高癌细胞中的p21蛋白水平（p53无效）。相反，MDM 2的过表达降低了p21水平，缩短了p21半衰期。MDM 2促进p21降解，而不依赖于MDM 2的泛素化和E3连接酶功能。相反，MDM 2通过促进p21与蛋白酶体C8亚基的结合来促进p21降解。MDM 2作为p21的负调节剂发挥作用，这种作用独立于p53和泛素化。本申请旨在进一步阐明MDM 2癌基因作为p21负调控因子的作用和机制，具体目的有三：1）.确定MDM 2在转录水平调节p21的机制; 2）确定MDM 2在翻译后水平调节p21的机制; 3）确定MDM 2和p21在体外和体内对人类癌症生长和进展的活性。这些研究将产生有关MDM 2的p53非依赖性致癌活性机制的知识，并评估这些途径用于人类癌症预防和治疗的潜力。

DESCRIPTION (provided by applicant): The long-term objectives of this project are to determine the role of MDM2 oncogene in p21 regulation, to evaluate the potential of MDM2 and p21as novel targets for cancer chemoprevention and chemotherapy, and to translate these findings into more rational prevention and treatment of human cancers. The expression of p21 is under the control of p53. However, p21 is also regulated by p53-independent pathways. The MDM2 oncogene is overexpressed in many human cancers, with the MDM2 levels being associated with tumor progression and poor prognosis. MDM2 has a role in the regulation of p53 stability and activity. In addition, MDM2 also has p53-independent activity, which may be associated with its carcinogenic properties. Preliminary studies have indicated that MDM2 has an important role in regulation of p21. The inhibition of MDM2 with anti-MDM2 antisense oligonucleotide or siRNA targeting MDM2 significantly elevates p21 protein levels in cancer cells (p53 null). In contrast, overexpression of MDM2 diminishes the p21 level, shortening the p21 half-life. MDM2 facilitates p21 degradation independent of ubiquitination and the E3 ligase function of MDM2. Instead, MDM2 promotes p21 degradation by facilitating binding of p21 with the proteasomal C8-subunit. MDM2 functions as a negative regulator of p21, an effect independent of both p53 and ubiquitination. This application seeks to further clarify the role and mechanisms of MDM2 oncogene as a negative regulator of p21, including three Specific Aims: 1). To determine the mechanisms by which MDM2 regulates p21 at transcriptional level; 2) To determine the mechanisms by which MDM2 regulates p21 at post-translational level; and 3) To determine the in vitro and in vivo activity of MDM2 and p21 human cancer growth and progression. These studies will generate knowledge on the mechanisms responsible for the p53-independent carcinogenic activities of MDM2 and evaluate the potential of these pathways for human cancer prevention and treatment.