Genetic Polymorphism in Prostate Cancer

描述（由申请人提供）：NKX3.1是一种前列腺特异性同源盒基因，映射到染色体8p21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在前列腺癌中不发生体细胞突变，但该蛋白的表达随着肿瘤的进展而丢失，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，单倍功能不全占主导地位，导致前列腺上皮增生和不典型增生，并随着年龄的增长而恶化。此外，Nkx3.1单倍性不全与Pten等其他抑制基因的缺失共同促进前列腺癌的发生。这些数据表明，NKX3.1表达的缺失可能在很大一部分人类前列腺癌的发病机制中起重要作用，并且NKX3.1是一个候选的看门人基因。我们描述了一个NKX3.1多态性，C154T，导致密码子52的精氨酸到半胱氨酸的改变（NKX3.1 R52C）。在最初的资助期，我们发现单个NKX3.1 C154T等位基因（存在于11%的人群中）会增加患侵袭性前列腺癌的风险。我们还发现R52C变体改变了相邻丝氨酸48 （S48）的磷酸化，并且S48磷酸化在体外调节DNA结合。但NKX3.1不仅通过DNA结合影响基因表达，还通过与转录因子络合并调节其作为辅激活因子的活性来影响基因表达。初步数据显示，氨基酸44-64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端的结合。我们现在将确定NKX3.1的生化特性，这对它的作用至关重要。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结合的蛋白质。在Aim 3中，我们将鉴定和表征受NKX3.1表达调控的基因。在Aim 4中，我们将分析来自高级别前列腺癌患者的肿瘤标本，以确定在具有C154T多态性等位基因的患者中，C154T多态性等位基因是否在染色体8p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.