High expression of the RNA-binding protein RBPMS2 in gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract and are often associated with KIT or PDGFRA gene mutations. GIST cells might arise from the interstitial cells of Cajal (ICCs) or from a mesenchymal precursor that is common to ICCs and smooth muscle cells (SMCs). Here, we analyzed the mRNA and protein expression of RNA-Binding Protein with Multiple Splicing-2 (RBPMS2), an early marker of gastrointestinal SMC precursors, in human GISTs (n = 23) by in situ hybridization, quantitative RT-PCR analysis and immunohistochemistry. The mean RBPMS2 mRNA level in GISTs was 42-fold higher than in control gastrointestinal samples (p < 0.001). RBPMS2 expression was not correlated with KIT and PDGFRA expression levels, but was higher in GISTs harboring KIT mutations than in tumors with wild type KIT and PDGFRA or in GISTs with PDGFRA mutations that were characterized by the lowest RBPMS2 levels. Moreover, RBPMS2 levels were 64-fold higher in GIST samples with high risk of aggressive behavior than in adult control gastrointestinal samples and 6.2-fold higher in high risk than in low risk GIST specimens. RBPMS2 protein level was high in 87% of the studied GISTs independently of their histological classification. Finally, by inhibiting the KIT signaling pathway in GIST882 cells, we show that RBPMS2 expression is independent of KIT activation. In conclusion, RBPMS2 is up-regulated in GISTs compared to normal adult gastrointestinal tissues, indicating that RBPMS2 might represent a new diagnostic marker for GISTs and a potential target for cancer therapy.     

具有多种剪接形式的RNA结合蛋白基因的克隆、表达及其细胞内定位

目的：构建具有多种剪接形式的RNA结合蛋白（RBPMS）基因的真核表达载体,并在真核细胞中进行表达,确定RBPMS在细胞中的定位.方法：采用PCR技术,从人卵巢文库中扩增RBPMS基因的完整编码序列,将所扩增基因克隆到带FLAG标签的真核表达载体上,转染人胚肾细胞293T,Western印迹鉴定RBPMS的表达.然后将所扩增基因克隆到带绿色荧光标签的pEGFP-C1表达载体上,转染乳癌细胞ZR75-1,观察RBPMS在细胞中的定位情况.结果：经限制性内切酶分析和DNA序列测定鉴定构建的重组表达载体正确,Western印迹实验证明RBPMS表达成功,通过激光共聚焦显微镜观察,RBPMS分布在胞质中,在40%～50%细胞中RBPMS呈聚集状分布.结论：成功构建了RBPMS基因的真核表达载体,该基因产物分布在胞质中,在40%～50%细胞中RBPMS呈聚集状分布.