Hu Ying, Dobi Albert, Sreenath Taduru, Cook Christopher, Tadase Atekelt Y, Ravindranath Lakshmi, Cullen Jennifer, Furusato Bungo, Chen Yongmei, Thangapazham Rajesh L, Mohamed Ahmed, Sun Chen, Sesterhenn Isabell A, McLeod David G, Petrovics Gyorgy, Srivastava Shiv
Center for Prostate Disease Research, Department of Surgery, Uniformed Services University of the Health Sciences, Rockville, Maryland 20852, USA.
Clin Cancer Res. 2008 Aug 1;14(15):4719-25. doi: 10.1158/1078-0432.CCR-08-0531.
The expression of the ETS-related gene (ERG) is low or undetectable in benign prostate epithelial cells. High prevalence of ERG overexpression in prostate cancer cells due to TMPRSS2-ERG fusions suggest for causal roles of ERG protein in the neoplastic process. TMPRSS2-ERG fusion junctions have been extensively studied in prostate cancer. However, virtually nothing is known about the nature of full-length transcripts and encoded proteins. This study focuses on qualitative and quantitative features of full-length TMPRSS2-ERG transcripts in prostate cancer.
Full-length TMPRSS2-ERG transcripts were cloned and sequenced from a cDNA library generated from pooled RNA of six TMPRSS2-ERG fusion-positive prostate tumors. The encoded ERG proteins were analyzed in HEK293 cells. Copy numbers of TMPRSS2-ERG splice variants were determined by quantitative reverse transcription-PCR in laser capture microdissected prostate cancer cells.
Two types of TMPRSS2-ERG cDNAs were identified: type I, which encodes full-length prototypical ERG protein (ERG1, ERG2, ERG3), and type II, encoding truncated ERG proteins lacking the ETS domain (ERG8 and a new variant, TEPC). In microdissected prostate tumor cells from 122 patients, relative abundance of these variants was in the following order: ERG8 > TEPC > ERG 3 > ERG1/2 with combined overexpression rate of 62.3% in prostate cancer. Increased ratio of type I over type II splice forms showed a trend of correlation with less favorable pathology and outcome.
Qualitative and quantitative features of specific ERG splice variants defined here promise to enhance the utility of ERG as a biomarker and therapeutic target in prostate cancer.
ETS相关基因（ERG）在良性前列腺上皮细胞中的表达较低或无法检测到。由于TMPRSS2-ERG融合导致前列腺癌细胞中ERG过表达的高发生率提示ERG蛋白在肿瘤形成过程中具有因果作用。TMPRSS2-ERG融合接头已在前列腺癌中得到广泛研究。然而，关于全长转录本和编码蛋白的性质几乎一无所知。本研究聚焦于前列腺癌中全长TMPRSS2-ERG转录本的定性和定量特征。
从六个TMPRSS2-ERG融合阳性前列腺肿瘤的混合RNA生成的cDNA文库中克隆并测序全长TMPRSS2-ERG转录本。在HEK293细胞中分析编码的ERG蛋白。通过定量逆转录PCR在激光捕获显微切割的前列腺癌细胞中测定TMPRSS2-ERG剪接变体的拷贝数。
鉴定出两种类型的TMPRSS2-ERG cDNA：I型，编码全长原型ERG蛋白（ERG1、ERG2、ERG3）；II型，编码缺乏ETS结构域的截短ERG蛋白（ERG8和一种新变体TEPC）。在122例患者的显微切割前列腺肿瘤细胞中，这些变体的相对丰度顺序如下：ERG8>TEPC>ERG 3>ERG1/2，前列腺癌中的联合过表达率为62.3%。I型与II型剪接形式比例的增加显示出与较差病理和预后相关的趋势。
此处定义的特定ERG剪接变体的定性和定量特征有望提高ERG作为前列腺癌生物标志物和治疗靶点的效用。
