Selenium molecular signaling in human prostate cancer

描述（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应答的LNCaP和雄激素不应答的PC-3人前列腺癌细胞的生长。流式细胞术分析表明，硒在24小时后阻滞了细胞周期的多个过渡点，并在48小时后诱导细胞凋亡。Affymetrix基因芯片被用来分析可能介导这些细胞事件的基因表达变化。在硒处理细胞的生长抑制变得明显之前，许多细胞周期蛋白和CDKs被发现被抑制。这些变化伴随着CDK抑制剂和其他已知可降低CDK激活的调节分子的表达增加。此外，硒还降低了参与S相转变、DNA合成和有丝分裂的基因的表达。在蛋白质水平上证实了许多这些基因转录信号的改变。特别令人感兴趣的是GADD153，这是一个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)它是受硒调节程度最高的基因之一；(b)诱导发生较早，并在硒暴露后持续存在；(c)作为转录因子和其他c /EBP和ATF家族蛋白的二聚化伙伴，它是上游靶点，可能调节许多基因的转录；(d)在4种不同的前列腺癌细胞系中观察到GADD153的增加。本项目的目的是研究GADD153在硒的分子效应中的作用。研究计划包括4个目标。目的1：测定硒处理细胞中GADD153的DNA结合活性，并鉴定GADD153直接调控的基因。目的2是表征暴露于硒后GADD153的二聚化伙伴。目的3是评估在反义GADD153存在下细胞对硒的反应性变化。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处理对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.