Role of Eaf family proteins in prostate carcinogenesis

描述(申请人提供)：前列腺癌的发生涉及肿瘤抑制基因的失活和/或癌基因的激活，也深受雄激素的影响。雄激素影响前列腺癌的机制仍然知之甚少。初步研究表明，雄激素反应基因Eaf2，也被称为U19(上调基因19)，在前列腺中起到潜在的肿瘤抑制作用。在80%的晚期前列腺癌标本中检测到Eaf2下调和等位基因丢失。Eaf2基因敲除(KO)小鼠发生淋巴瘤、肝细胞癌和低分化肺腺癌，表明Eaf2在体内是一种肿瘤抑制因子。虽然Eaf2 KO前列腺癌并未发展为前列腺癌，但其表现为上皮增生和异型增生(MPIN)，提示Eaf2对前列腺癌有抑制作用。Eaf2和Eaf1被独立鉴定并命名为ELL相关因子(EAF)，基于它与ELL的关联，ELL是急性髓系白血病MLL的融合伙伴。Eaf2和Eaf1蛋白是EAF家族中仅有的成员，具有58%的同源性和74%的相似性。Eaf1和Eaf2在前列腺上皮细胞中均有表达，其中Eaf1是结构性的，Eaf2是雄激素诱导的。过表达Eaf1或Eaf2均可诱导前列腺癌细胞凋亡，表明它们在功能上具有相似性。这些发现导致了我们的假设，即肿瘤抑制需要适当的EAF基因剂量，两个EAF家族基因的缺失都可能导致前列腺癌。四个特定的目标将定义EAF家族基因在前列腺癌发生中的作用。1.确定在小鼠模型中，前列腺中的Eaf1条件性KO是否会导致与Eaf2 KO中观察到的表型相似的表型。2.检测两种EAF基因缺失是否会导致小鼠前列腺癌。我们将杂交Eaf2 KO小鼠和前列腺特异性Eaf1 KO小鼠，以产生Eaf1-Eaf2双KO小鼠。3.确定电弧炉基因剂量对电弧炉下游通路的影响。我们将利用基因芯片比较野生型、Eaf1 KO、Eaf2 KO和双KO前列腺的基因表达谱。4.确定前列腺癌标本中Eaf1和/或Eaf2的下调是否具有预后价值。我们将通过人类前列腺癌组织微阵列的半定量免疫染色来确定Eaf1和/或Eaf2的表达，并将其与临床结果相关联，例如无病生存。该项目的成功将把EAF蛋白定义为前列腺癌中的肿瘤抑制因子，提供雄激素和肿瘤抑制因子之间的联系，并为进一步探索EAF诊断、预后、预防和/或治疗前列腺癌的途径奠定坚实的基础。

DESCRIPTION (provided by applicant): Prostate carcinogenesis involves inactivation of tumor suppressors and/or activation of oncogenes and is also profoundly influenced by androgens. The mechanism by which androgens affect prostate cancer remains poorly understood. Preliminary studies show that the androgen-response gene Eaf2, also termed U19 (up-regulated gene 19), acts as a potential tumor suppressor in the prostate. Eaf2 down-regulation and allelic loss were detected in >80% of human advanced prostate cancer specimens. Eaf2 knockout (KO) mice developed lymphoma, hepatocellular carcinoma, and poorly differentiated lung adenocarcinoma, demonstrating that Eaf2 is a tumor suppressor in vivo. Although the Eaf2 KO prostate did not develop prostate cancer, it exhibited epithelial hyperplasia and dysplasia (mPIN), suggesting that Eaf2 contributes to the suppression of prostate tumors. Eaf2, along with Eafl, was independently identified and termed ELL- associated factors (Eaf), based on its association with ELL, a fusion partner of MLL in acute myeloid leukemia. Eaf2 and Eaf1 proteins, with 58% identity and 74% similarity, are the only members in the Eaf family. Both Eaf1 and Eaf2 are expressed in prostate epithelial cells, with Eaf1 being constitutive and Eaf2 androgen-inducible. Overexpression of either Eaf1 or Eaf2 induces apoptosis of prostate cancer cells, indicating their functional similarities. These findings led to our hypothesis that tumor suppression requires proper Eaf gene dosage and that the loss of both Eaf family genes can lead to prostate cancer. Four Specific Aims will define the roles of Eaf family genes in prostate carcinogenesis. 1. Determine if an Eaf1 conditional KO in the prostate will cause a similar phenotype to that observed in the Eaf2 KO prostate in the mouse model. 2. Test whether the loss of both Eaf genes causes prostate cancer in the mouse model. We will crossbreed the Eaf2 KO and prostate-specific Eaf1 KO mice to generate Eaf1-Eaf2 double KO mice. 3. Determine the effect of Eaf gene dosage on Eaf-downstream pathways. We will compare the gene expression profiles in the wild-type, Eaf1 KO, Eaf2 KO, and double KO prostate using cDNA microarray. 4. Determine if down-regulation of Eafl and/or Eaf2 in human prostate cancer specimens has prognostic value. We will determine Eafl and/or Eaf2 expression by a semiquantitative immunostaining of human prostate cancer tissue microarray and correlate this with clinical outcomes, such as disease-free survival. The success of this project will define Eaf proteins as tumor suppressors in the prostate, providing a link between androgens and tumor suppressors and a strong foundation for further exploring Eaf pathways for diagnosis, prognosis, prevention, and/or treatment of prostate cancer.