MUTUAL REGULATION OF P53, MDM2 AND NFKB:

描述：(申请人摘要)尽管在以下方面取得了实质性进展 儿童急性淋巴细胞白血病(ALL)的治疗，约25%-35% 患有这种疾病的儿童会复发或诱导治疗失败。失败 对治疗的反应可能是由于对细胞凋亡产生了抵抗力 由化疗药物引起的。在申请人的儿科ALL研究中 在复发中，他发现白血病细胞表达突变的p53基因或 过表达P53抑制的MDM2癌基因呈结构性高表达 活化的核因子kappaB(NFkB)水平，它已与 抗DNA损伤后的细胞凋亡。相反，所有细胞都表达 野生型(Wt)-p53通常不显示或非常低水平的激活 NFkB。由于wt-p53功能是在DNA损伤后在细胞中诱导的，而且由于 这一功能在表达mut-p53等位基因或过度表达的细胞中丢失 MDM2，申请人假设一个重要的诱导细胞凋亡的作用 WT-P53可能具有抑制NFkB活性的作用。相应地，MUT-P53的表达 或高水平的MDM2会增加激活的NFkB的水平 抑制wt-p53的NFkB抑制功能。因此，在正常细胞中，P53 和NFkB会相互作用，以响应DNA损伤，允许细胞凋亡 在遭受不可修复的DNA损伤的细胞中；这种相互调节的丧失通过 无论是p53突变还是mdm2过表达都会导致对 细胞凋亡诱导剂。为了验证他的假设，他将研究 突变型P53或MDM2上调所有细胞的NFkB活性。 重要的是，他将研究直接抑制的细胞后果 MDM2和NFkB激活。这些研究可能直接在临床上应用于 建议抑制NFkB介导的白血病耐药的方法 其他恶性肿瘤。这项研究的具体目的是：1)评估 突变型P53和过表达的MDM2激活NFkB的能力 转录调控NFkB/p65基因表达，包括鉴定 P65/relA中可能的p53或MDM2结合和反应元件 启动子；2)研究mut-p53和mdm2蛋白在转录水平的变化。 通过提高NFkB抑制剂Ikba的周转来激活NFkB，以及3) 评价阻断MDM2过表达和提高IKB水平的效果 反义MDM2和蛋白酶体对细胞凋亡敏感性的研究 分别为抑制剂。

DESCRIPTION: (Applicant's Abstract) Despite substantial advances in the treatment of childhood acute lymphoblastic leukemia (ALL), approximately 25-35% of children with this disease will relapse or fail induction therapy. Failure to respond to treatment may result from development of resistance to apoptosis induced by chemotherapeutic agents. In the applicant's studies of pediatric ALL in relapse, he has found that leukemic cells expressing a mutant p53 gene or overexpressing the p53-inhibitory MDM2 oncogene express constitutively high levels of activated Nuclear Factor kappa B (NFkB), which has been linked to resistance to apoptosis following DNA damage. Conversely, ALL cells expressing wild type (wt)-p53 typically show either no or very low levels of activated NFkB. Since wt-p53 function is induced in cells following DNA damage, and since this function is lost in cells expressing a mut-p53 allele or overexpressing MDM2, the applicant hypothesizes that an important apoptosis-inducing effect of wt-p53 may be inhibition of NFkB activity. Accordingly, expression of mut-p53 or high levels of MDM2 would increase the level of activated NFkB by suppressing the NFkB-inhibitory function of wt-p53. Thus, in normal cells, p53 and NFkB would mutually interact in response to DNA damage to permit apoptosis in cells sustaining irreparable DNA damage; loss of this mutual regulation by either p53 mutation or MDM2 overexpression would result in resistance to apoptosis-inducing agents. To test his hypothesis, he will study the potential upregulation of NFkB activity by either mutant p53 or MDM2 in ALL cells. Importantly, he will examine the cellular consequences of directly inhibiting MDM2 and NFkB activation. These studies may have direct clinical application in suggesting ways to inhibit NFkB-mediated therapy resistance in leukemia and other malignancies. The specific aims of this study are 1) To evaluate the ability of mutant p53 and overexpressed MDM2 to activate NFkB by transcriptionally regulating NFkB/p65 gene expression, including identification of possible p53- or MDM2-binding and response elements in the p65/RelA promoter; 2) To investigate the ability of mut-p53 and MDM2 proteins to activate NFkB by enhancing turnover of the NFkB inhibitor IkBa and 3) To evaluate the effect of blocking MDM2 overexpression and augmenting IkB levels on sensitivity to apoptosis utilizing anti-MDM2 antisense and proteasome inhibitors, respectively.