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异型盒基因，其定位于染色体8 p21的一个区域，该区域在高达85%的前列腺癌病例中丢失。虽然NKX3.1在前列腺癌中不经历体细胞突变，但该蛋白的表达随着肿瘤进展而丧失，表明NKX3.1在前列腺癌发病机制中的作用。在Nkx3.1小鼠中，单倍不足占主导地位，导致前列腺上皮增生和发育不良，这与年龄有关。此外，Nkx3.1单倍不足与其他抑制基因（如Pten）的缺失协同作用，增强前列腺癌的发生。这些数据表明，NKX3.1表达的丧失可能在大部分人前列腺癌的发病机制中是重要的，并且NKX3.1是候选的看门基因。我们描述了一个NKX3.1多态性，C154 T，导致精氨酸半胱氨酸密码子52（NKX3.1 R52 C）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NKX3.1 C154 T等位基因，会增加侵袭性前列腺癌的风险。我们还发现，R52 C变异改变了相邻丝氨酸48（S48）的磷酸化，S48磷酸化调节体外DNA结合。但NKX3.1不仅通过DNA结合影响基因表达，还通过与转录因子复合并作为共激活因子调节其活性来影响基因表达。初步数据显示，氨基酸44-64的区域对于NKX3.1共激活活性的自动调节是关键的，推测是通过介导与C-末端的结合。我们现在将确定NKX3.1的生化特性对其作用至关重要。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。在目标3中，我们将鉴定和表征其表达受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，以确定在具有C154 T多态性等位基因的患者中，其在染色体8 p杂合性丢失后是否优先保留。

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.