Murthy S S, Shen T, De Rienzo A, Lee W C, Ferriola P C, Jhanwar S C, Mossman B T, Filmus J, Testa J R
Human Genetics Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA.
Oncogene. 2000 Jan 20;19(3):410-6. doi: 10.1038/sj.onc.1203322.
Gene expression changes in rat asbestos-induced malignant mesothelioma (MM) cells were investigated by differential mRNA display. A mRNA transcript identified by this approach was abundant in normal rat mesothelial cells but not expressed in rat MM cell lines. Northern blot analysis confirmed that this transcript is uniformly silenced in rat MM cell lines and primary tumors. Nucleotide sequence analysis revealed that this transcript is encoded by the rat glypican 3 gene (GPC3), whose human homolog is mutated in the Simpson-Golabi-Behmel overgrowth syndrome. Allelic loss at the GPC3 locus was infrequent (6.9%) in MM cell lines, and no mutations were found. GPC3 transcript levels were markedly decreased in 16 of 18 primary tumors and 17 of 22 human MM cell lines. Most of the cell lines were shown to have aberrant methylation of the GPC3 promoter region. In two of four human MM cell lines tested, GPC3 expression was restored after 2-deoxy 5-azacytidine (DAC)-mediated demethylation of its promoter region. Ectopic expression of GPC3 inhibited in vitro colony formation of human MM cells. Collectively, these data suggest that down-regulation of GPC3 is a common occurrence in MM and that GPC3, an X-linked recessive overgrowth gene, may encode a negative regulator of mesothelial cell growth.
通过差异mRNA显示技术研究了大鼠石棉诱导的恶性间皮瘤（MM）细胞中的基因表达变化。通过这种方法鉴定出的一种mRNA转录本在正常大鼠间皮细胞中丰富，但在大鼠MM细胞系中不表达。Northern印迹分析证实，该转录本在大鼠MM细胞系和原发性肿瘤中均被一致沉默。核苷酸序列分析表明，该转录本由大鼠磷脂酰肌醇蛋白聚糖3基因（GPC3）编码，其人同源基因在辛普森-戈拉比-贝梅尔过度生长综合征中发生突变。MM细胞系中GPC3基因座的等位基因缺失很少见（6.9%）且未发现突变。18个原发性肿瘤中的16个以及22个人类MM细胞系中的17个GPC3转录水平明显降低。大多数细胞系显示GPC3启动子区域存在异常甲基化。在测试的四个人类MM细胞系中的两个中，2-脱氧5-氮杂胞苷（DAC）介导其启动子区域去甲基化后，GPC3表达得以恢复。GPC3的异位表达抑制了人类MM细胞的体外集落形成。总体而言，这些数据表明GPC3的下调在MM中很常见，并且GPC3作为一个X连锁隐性过度生长基因，可能编码间皮细胞生长的负调节因子。
