THE ROLE OF PTEN AND THE PI3K PATHWAY IN PROSTATE CANCER

本基金的三个项目重点是评估PTEN/MMAC1肿瘤抑制基因和磷酸肌醇激酶（PI3K）信号通路在前列腺癌中的作用。PI3K与前列腺癌有关，因为最近发现PTEN编码一种磷酸酶，该磷酸酶可水解PTEN缺陷的癌症脂质产物。缺乏PTEN的前列腺癌细胞系具有PI3K下游酶的组成性激活，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，导致细胞生长下降和细胞凋亡增加。尽管对细胞系的研究表明，抑制PI3K可以阻断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。小鼠PTEN的杂合缺失导致多种组织增生，包括前列腺和前列腺腺癌。这些小鼠为PTEN缺失导致的人类前列腺癌提供了一个模型。这项工作的目标是测试删除PI3K通路中酶基因对小鼠前列腺癌发展的影响，并开发技术来评估PI3K通路是否在人类前列腺癌中被激活。拟议的工作涉及三个项目和三个核心之间的广泛合作，利用各自实验室的专业知识。在Project 1中，Cantley实验室将生成前列腺中PI3K调控亚基缺失的小鼠。然后将这些小鼠与缺乏PTEN的小鼠杂交，以确定PI3k调节亚基的缺失是否会阻止PTEN缺失导致的前列腺癌的发展。在Project 2中，Robert的实验室将产生在前列腺中删除PI3K催化亚基的小鼠作为样本。为了同样的目的，前列腺中PI3K的调控和催化亚基的多个基因被删除。为了同样的目的，前列腺中PI3K的调控和催化亚基的多个基因被删除。PI3K调控亚基和催化亚基的多个基因在小鼠和男性中都存在，这些研究将表明其中哪一个对前列腺癌的发展最为关键。在项目3中，Sellers实验室将评估PI3K下游的其他蛋白质。对于被认为对前列腺癌细胞依赖pi3k生长或存活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靶向删除这些基因。制药公司目前正在开发PI3K催化位点抑制剂、AKT抑制剂和PI3K调控亚基功能抑制剂。然而，迄今为止，可用的抑制剂缺乏足够的特异性，并且存在生物利用度和毒性问题，妨碍了评估。这些研究将提示哪些蛋白质应该成为治疗前列腺癌的目标。

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.