Oncogenic Function of a P53-Induced Phosphatase

描述(申请人提供)：在大多数人类肿瘤中，肿瘤抑制基因P53在结构或功能上是失活的。在那些保留完整P53的肿瘤中，P53信号通常通过改变其他分子的表达而失活。这种P53功能失活的一个例子发生在人类肉瘤的一部分中，其中癌基因MDM2的扩增和过度表达导致P53的降解。最近文献中的两份报告暗示，在人类乳腺癌和前列腺癌中，另一个潜在的癌基因可能会使P53失活。该基因编码野生型P53诱导的磷酸酶Wip1或Ppm1d)。在16%的人类乳腺癌中被扩增和过度表达。它是这些乳腺癌中唯一持续扩增的基因，在体外转化试验中显示出转化活性。WIPL是由P53在电离或紫外线照射后诱导的，已有研究表明WIPL可使p38MAPK去磷酸化，使其失活，并通过磷酸化抑制P53的p38激活。假设Wip1形成负调控反馈环的一部分，该负调控反馈环在p53最初激活后间接抑制P53功能。因此，Wip1在人类肿瘤中的扩增可能导致对P53信号的抑制程度增加，并通过P53依赖的机制促进肿瘤的发生。这项建议的一个主要目标是使用体外培养系统和动物模型(包括我们实验室培育的Wip1基因敲除小鼠)在多种情况下测试Wip1的致癌活性。我们将确定Wipl的缺失是否通过增加P53的活性来赋予肿瘤耐药表型。我们还将研究Wipl在促进转化或肿瘤形成方面是否具有P53独立的作用，以及Wipl的哪些区域对转化相关效应至关重要。这项建议的第二个主要目标是确定受Wipl影响的正常细胞信号通路，以试图了解这种磷酸酶的正常生物学功能。将鉴定与Wip1相互作用的蛋白质，并探索它们与Wip1的关系。我们的总体目标是更好地理解这种假定的人类癌基因影响正常和致癌细胞信号的分子机制。

DESCRIPTION (provided by applicant): The tumor suppressor p53 is structurally or functionally inactivated in most human tumors. In those tumors that retain intact p53, p53 signaling is often inactivated through altered expression of other molecules. An example of this p53 functional inactivation occurs in a fraction of human sarcomas, in which amplification and overexpression of the oncogene mdm2 results in p53 degradation. Two recent reports in the literature implicate another potential oncogene that may inactivate p53 in human breast and prostate cancers. This gene, encoding the wildtype p53-induced phosphatase wip1 or Ppm1 d). is amplified and overexpressed in 16% of human breast cancers. It is the only consistently amplified gene in these breast cancers that shows transforming activity in in vitro transformation assays. Wipl is induced by p53 following ionizing or ultraviolet radiation and it has been shown to dephosphorylate p38 MAP kinase, inactivating it and inhibiting p38 activation of p53 through phosphorylation. It is hypothesized that Wipl forms part of a negative regulatory feedback loop that indirectly inhibits p53 function following initial activation of p53. Thus, amplification of Wipl in human tumors could cause increased inhibition of p53 signaling and promote tumorigenesis through p53-dependent mechanisms. A major goal of this proposal is to use in vitro culture systems and animal models (including a Wipl knockout mouse that our laboratory has generated) to test the oncogenicib, of Wip1 in multiple contexts. We will determine whether the absence of Wipl confers a tumor resistance phenotype through increased p53 activity. We will also examine whether Wipl has p53-independent effects in enhancement of transformation or tumorigenesis and which domains of Wipl are crucial for transformation-related effects. A second major goal of this proposal is to identify normal cell signaling pathways influenced by Wipl in an attempt to understand the normal biological functions of this phosphatase. Wip1-interacting proteins will be identified and their relationship to Wipl will be explored. Our overall goal is to better understand the molecular mechanisms by which this putative human oncogene affects both normal and oncogenic cell signaling.