摘要目的 研究Hedgehog通路中Ptchl基因表达及其甲基化状态在胃癌发生中的变化.方法 分别抽提10例胃癌组织及其癌旁＞3 cm组织和胃癌细胞株AGS的总RNA和基因组DNA.实时定量逆转录多聚酶链反应(QRT-PCR)检测Ptch基因的mRNA表达.应用软件分析Ptchl基因5'调控序列的CpG岛状态,亚硫酸氢盐测序PCR(BSP)分析甲基化水平.结果 对Ptchl mRNAla转录体转录起始位点(计为0点)上游-3950 bp和下游+2050 bp进行CpG岛分析,发现存在两个CpG岛,第1个为-1139 bp～+860 bp,第2个为+875 bp～+1692 bp.以第1个CpG岛的-870 bp～+229 bp区段内的19个CpG位点的BSP测序结果显示,胃癌细胞株AGS全部发生甲基化,胃癌组织中甲基化程度为16%～100%,平均64%±32%,癌旁组织甲基化程度为0%～42%,平均13%±14%,两组问差异有统计学意义(P＜0.05).Spearman秩相关分析发现,Ptchl基因甲基化同其表达呈负相关(r=-0.558,P=0.011).结论 Ptchl基因高甲基化参与胃癌的发生,可能为胃癌新的肿瘤标志物.

abstractsObjective To investigate the expression and aberrant methylation of Ptchl gene in hedgehog signal pathway in carcinogenesis of human gastric cancer.Methods The total RNA and genomic DNA were extracted from 10 human gastric carcinoma tissues,adjacent tissues(＞3 cm from cancerous tissue)and gastric cancer eell line AGS.Ptchl mRNA expression was detected by real-time quantitative reverse transcription PCR.The pattern of CpG island in Ptchl gene 5'regulation sequence was analyzed by software and its methylation extent was tested by bisulfite sequencing PCR.Results The analysis of CpG island(starting-3950 bases upstream of the Ptchl mRNAla transcription start site and ending 2050 bases downstream)revealed that there were two CpG islands in Ptchl gene 5' regulation sequence(first CpG:-1139 bp～+860 bp;second CpG:+875 bp～+1692 bp).Bisulfite sequencing PCR analysis of 19 CpG sites included in the first CpG island(-870 bp～+229 bp)showed that there was methylation present in all cell lines and the average extent of the methylation of these CpG sites was significantly higher in cancerous tissues(64%±32%,ranged 16%～100%)than that in adjacent tissues(13%±14%,ranged 0%～42%,P＜0.05).There was a negative correlation of the Ptchl methylation with its expression.Conclusion The high methylation of Ptchl gene that involves in the carcinogenesis of human gastric carcer will be a new biomarker for gastric carcer.