Selenium molecular signaling in human prostate cancer

描述(由申请人提供)：目前关于硒化学预防前列腺癌的分子机制的信息很少。初步研究表明，生理浓度的硒代谢物抑制雄激素反应性LNCaP和雄激素非反应性PC-3人前列腺癌细胞的生长。流式细胞仪分析表明，硒在24小时后在多个转换点阻断细胞周期进程，48小时后诱导细胞凋亡。Affymetrix基因芯片被用来描述可能介导这些细胞事件的基因表达变化。就在硒处理的细胞生长受到明显抑制之前，一些细胞周期蛋白和CDK被发现受到抑制。伴随着这些变化的是CDK抑制剂和其他已知可减少CDK激活的调节分子的表达增加。此外，硒还降低了S相变、脱氧核糖核酸合成和有丝分裂相关基因的表达。这些基因中的许多转录信号的变化在蛋白质水平得到了证实。特别令人感兴趣的是GADD153，这是一种有充分证据证明在细胞周期控制和细胞凋亡中发挥重要作用的基因。关注GADD153的原因是：(A)它是受硒调控最高的基因之一；(B)在硒暴露后，GADD153的诱导发生在早期并持续；(C)作为一个转录因子和其他C/EBP和ATF家族蛋白的二聚体伙伴，它是一个上游靶标，可能调节许多基因的转录；以及(D)在4个不同的前列腺癌细胞系中观察到GADD153表达增加。该项目的目标是研究GADD153在硒的分子效应中的作用。该研究计划包括四个目标。目的1测定GADD153在硒处理细胞中的DNA结合活性，并鉴定GADD153直接调控的基因。目的2是研究暴露于硒后GADD153的二聚化伙伴的特征。目的3是评价反义GADD153存在下细胞对硒反应的变化。目的4研究硒对GADD153的转录调控作用。因此，拟议的研究旨在系统地检查硒治疗对GADD153诱导的影响。

DESCRIPTION (provided by applicant): Scanty information is currently available on the molecular mechanism of selenium chemoprevention in prostate cancer. Preliminary studies showed that physiological concentrations of a selenium metabolite inhibited the growth of both the androgen-responsive LNCaP and the androgen-nonresponsive PC-3 human prostate cancer cells. Analysis by flow cytometry indicated that selenium blocked cell cycle progression at multiple transition points after 24 hours and induced apoptosis after 48 hours. The Affymetrix GeneChip was used to profile the gene expression changes that might mediate these cellular events. Immediately before growth inhibition became evident in selenium-treated cells, a number of cyclins and CDKs were found to be depressed. These changes were accompanied by an increased expression of CDK inhibitors and other regulatory molecules that are known to reduce the activation of CDKs. Additionally, selenium also decreased the expression of genes involved in S phase transition, DNA synthesis and mitosis. Alterations in the transcript signal of many of these genes were confirmed at the protein level. Of particular interest is GADD153, a gene well documented to play an essential role in cell cycle control and apoptosis. The reasons for focusing on GADD153 are (a) it is one of the most highly modulated genes by selenium; (b) the induction occurs early and persists following selenium exposure; (c) as a transcription factor and a dimerization partner to other C/EBP and ATF family of proteins, it is an upstream target and is likely to modulate the transcription of many genes; and (d) the increase of GADD153 is observed in 4 different prostate cancer cell lines. The goal of this project is to investigate the role of GADD153 in contributing to the molecular effects of selenium. The research plan consists of 4 aims. Aim 1 is to determine the DNA binding activity of GADD153 in selenium-treated cells, and to identify the genes modulated directly by GADD153. Aim 2 is to characterize the dimerization partners of GADD153 following exposure to selenium. Aim 3 is to evaluate the changes in cellular responsiveness to selenium in the presence of antisense GADD153. Aim 4 is to study the transcriptional control of GADD153 by selenium. The proposed research is thus designed to examine systemically the impact of GADD153 induction as a result of selenium treatment.