THE ROLE OF PTEN AND THE PI3K PATHWAY IN PROSTATE CANCER

这项拨款的三个项目高度集中于评估前列腺癌中的PTEN/MMAC1抑癌基因和磷脂酰肌醇3-激酶(PI3K)信号通路。PI3K与前列腺癌有关，因为最近发现PTEN编码一种磷酸酶，该酶能降解癌症的脂肪产物，PTEN存在缺陷。缺乏PTEN的前列腺癌细胞系具有PI3K下游酶的结构性激活，包括AKT蛋白-丝氨酸/苏氨酸激酶，PTEN的重新引入(或添加PI3K抑制剂)阻断了这一途径，导致细胞生长减慢和细胞凋亡增加。尽管对细胞系的研究表明，抑制PI3K应该会阻止PTEN缺失导致的肿瘤的生长和存活，但没有证据表明这在体内是正确的。在小鼠中，PTEN杂合性缺失会导致多种组织的增殖，包括前列腺癌和前列腺癌。这些小鼠为人类前列腺癌提供了一个模型，这种癌症是由PTEN基因缺失引起的。这项拟议工作的目标是测试删除PI3K途径中的酶基因对小鼠前列腺癌发展的影响，并开发评估PI3K途径在人类前列腺癌中是否激活的技术。拟议的工作涉及三个项目和三个核心之间的广泛合作，利用各个实验室的专门知识。在项目1中，坎特利实验室将培育出前列腺中PI3K调节亚基缺失的小鼠。然后，这些小鼠将与PTEN缺失的小鼠杂交，以确定PI3K调节亚单位的缺失是否阻止了PTEN缺失导致的前列腺癌的发展。在项目2中，罗伯特的实验室将产生PI3K催化亚单位在前列腺中被删除的小鼠作为样本。为了同样的目的，PI3K的调节和催化亚基的多个基因在前列腺中被删除。为了同样的目的，PI3K的调节和催化亚基的多个基因在前列腺中被删除。PI3K的调节亚基和催化亚基在小鼠和人类中都存在多个基因，这些研究将表明其中哪一个对前列腺癌的发生最关键。在项目3中，Sellers实验室将评估PI3K下游的其他蛋白质。对于被判断为对PI3K依赖的前列腺癌细胞系的生长或生存至关重要的下游靶点，将进行显性-阴性形式的前列腺特异性表达或有针对性的基因缺失。制药公司目前正在开发PI3K催化位点抑制剂、AKT抑制剂和PI3K功能调节亚单位的抑制剂。然而，到目前为止，可用的抑制剂还不够具体，在生物利用度和毒性方面存在问题，无法进行评估。这些研究将建议将这些蛋白质中的哪一种作为前列腺癌治疗的靶点。

The three projects of this grant are highly focused on evaluating the PTEN/MMAC1 tumor suppressor gene and the phosphoinositide 3-kinase (PI3K) signaling pathway in prostate cancer. PI3K has been implicated in prostate cancer because of the recent discovery that PTEN encodes a phosphatase that hydrolyzes the lipid products of cancers have defects in PTEN. Prostate cancer cell lines that lack PTEN have constitutive activation of enzymes down-stream of PI3K, including the AKT protein- Ser/Thr kinase and reintroduction of PTEN (or addition of PI3K inhibitors) blocks this pathway and leads to decreased cell growth and increased apoptosis. Although studies with cell lines suggest that inhibition of PI3K should block growth and survival of tumors that result from loss of PTEN, there is no evidence that this is true in vivo. Heterozygous loss of PTEN in mice results in hyperplasia in multiple tissues, including prostate and adenocarcinomas of the prostate. These mice provide a model for human prostate cancers that result from loss of PTEN. The goal of the proposed work is to test the effect of deleting genes of enzymes in the PI3K pathway on the development of prostate cancer in mice, and to develop techniques that will evaluate whether the PI3K pathway is activated in human prostate cancers. The proposed work involves extensive collaborations between the three projects and the three cores, taking advantage of the expertise of individual laboratories. In Project 1, the Cantley laboratory will generate mice in which the regulatory subunits of PI3K are deleted in the prostate. These mice will then be crossed with the mice that lack PTEN in order to determine whether loss of the PI3k regulatory subunit blocks the development of prostate cancers that result from loss of PTEN. In Project 2, the Robert's laboratory will generate mice in which the catalytic subunit of PI3K is deleted in the prostate for the sample purpose. Multiple genes for both the regulatory and catalytic subunits of PI3K is deleted in the prostate for the same purpose. Multiple genes for both the regulatory and catalytic subunit of PI3K is deleted in the prostate for the same purpose. Multiple genes for both the regulatory and catalytic subunits of PI3K exist in mice and men and these studies will indicate which of these is the most critical for prostate cancer development. In Project 3, the Sellers laboratory will evaluate additional proteins downstream of PI3K. For downstream targets judged to be critical for PI3K-dependent growth or survival of prostate cancer cell lines, prostate-specific expression of dominant- negative forms or targeted deletion of the genes will be performed. Pharmaceutical companies are currently developing PI3K catalytic site inhibitors, AKT inhibitors and inhibitors of the function of the regulatory subunit of PI3K. However, to date, the inhibitors available are not sufficiently specific and have problems with bioavailability and toxicity that preclude evaluation. These studies will suggest which of these proteins should be targeted for treatment of prostate cancer.