Genetic Polymorphism in Prostate Cancer

描述(申请人提供)：NKX3.1是一种前列腺特异的同源框基因，它映射到8p21染色体上的一个区域，该区域在高达85%的前列腺癌病例中丢失。尽管NKX3.1在前列腺癌中没有发生体细胞突变，但随着肿瘤的进展，NKX3.1蛋白的表达丢失，这表明NKX3.1在前列腺癌的发病机制中发挥了作用。在Nkx3.1小鼠中，单倍体功能不全占主导地位，导致前列腺上皮增生和异型增生，并随着年龄的增长而恶化。此外，Nkx3.1单倍体功能不全与其他抑制基因如Pten的缺失协同促进前列腺癌的发生。这些数据表明，NKX3.1的表达缺失可能在很大一部分人前列腺癌的发病机制中起重要作用，NKX3.1是一个候选的把关基因。我们描述了一个NKX3.1多态，C154T，该多态导致52位密码子(NKX3.1 R52C)精氨酸到半胱氨酸的改变。在最初的资助期间，我们发现在11%的人群中存在单个NKX3.1C154T等位基因，这会增加患侵袭性前列腺癌的风险。我们还发现R52C变异体改变了邻近的丝氨酸48的磷酸化(S48)，并且S48的磷酸化在体外调节了DNA的结合。但NKX3.1不仅通过DNA结合影响基因表达，还通过与转录因子结合并调节其作为辅助激活因子的活性来影响基因表达。初步数据表明，氨基酸44-区域对NKX3.1共激活活性的自动调节至关重要，可能是通过介导与C末端的结合来实现的。我们现在将确定对其作用至关重要的NKX3.1的生化特性。在目标1中，我们将对NKX3.1进行遗传分析，以确定调节蛋白质活性的关键元件。在目标2中，我们将使用NKX3.1进行亲和层析，以分离和鉴定与NKX3.1结合的蛋白。在目标3中，我们将识别和表征其表达受NKX3.1调控的基因。在目标4中，我们将分析来自高级别前列腺癌患者的肿瘤标本，以确定在那些具有C154T多态等位基因的患者中，它是否在8p染色体杂合性丢失后优先保留。

DESCRIPTION (provided by applicant): NKX3.1 is a prostate-specific homeobox gene that maps to a region of chromosome 8p21 that is lost in up to 85% of prostate cancer cases. Although NKX3.1 does not undergo somatic mutations in prostate cancer, expression of the protein is lost with tumor progression, suggesting a role for NKX3.1 in prostate cancer pathogenesis. In Nkx3.1 mice haploinsufficiency is dominant, resulting in prostatic epithelial hyperplasia and dysplasia that worsens with age. Moreover, Nkx3.1 haploinsufficiency cooperates with loss of other suppressor genes such as Pten to enhance prostate carcinogenesis. These data suggest that loss of NKX3.1 expression may be important in pathogenesis of a large fraction of human prostate cancers and that NKX3.1 is a candidate gatekeeper gene. We described an NKX3.1 polymorphism, C154T, that resulted in an arginine to cysteine alteration of codon 52 (NKX3.1 R52C). In the initial grant period we showed that a single NKX3.1 C154T allele, present in 11% of the population, conferred an increased risk for aggressive prostate cancer. We also showed that the R52C variant altered phosphorylation at the adjacent serine 48 (S48) and that S48 phosphorylation regulated DNA binding in vitro. But NKX3.1 influences gene expression not only by DNA binding, but also by complexing with transcription factors and regulating their activity as a coactivator. Preliminary data shows that the region of amino acids 44-64 is critical for autoregulation of NKX3.1 coactivation activity, presumably by mediating binding to the C-terminus. We now will determine biochemical properties of NKX3.1 critical for its action. In Aim 1 we will perform genetic analysis of NKX3.1 to identify critical elements that regulate protein activity. In Aim 2 we will perform affinity chromatography with NKX3.1 to isolate and identify proteins that bind to NKX3.1. In Aim 3 we will identify and characterize genes whose expression is regulated by NKX3.1. In Aim 4, we will analyze tumor specimens from patients with high-grade prostate cancer to determine whether in those with the C154T polymorphic allele it is preferentially retained after loss of chromosome 8p heterozygosity.