胃癌维甲酸信号通路相关基因启动子区协同高甲基化的研究

Synergistic Promoter Hypermethylation of Retinoic Acid Signaling Pathway-associated Genes in Gastric Carcinoma

背景:启动子区高甲基化与胃癌中多种抑癌基因表达沉默密切相关。目的:探讨维甲酸信号通路相关基因维甲酸受体β(RARβ)、细胞维生素A结合蛋白1(CRBP1)和他扎罗汀诱导基因1(TIG1)启动子区高甲基化与胃癌的关系。方法:以甲基化特异性聚合酶链反应(MSP)检测40例胃癌标本、10例正常胃黏膜标本和6株胃癌细胞株的RARβ、CRBP1和TIG1基因启动子区甲基化状态,分析三者甲基化状态的相关性及其与胃癌临床病理特征的关系。以逆转录聚合酶链反应(RT-PCR)检测胃癌细胞株RARβ、CRBP1和TIG1 mRNA表达。结果:40例胃癌组织的RARβ、CRBP1和TIG1基因甲基化率分别为45.0%、32.5%和57.5%,10例正常胃黏膜组织均未检测到上述基因甲基化(P<0.05)。胃癌组织中RARβ的甲基化状态与CRBP1和TIG1的甲基化状态显著相关(P<0.05),但三者的甲基化状态与胃癌临床病理特征无相关性。启动子区高甲基化胃癌细胞株相应基因mRNA表达缺失或减弱。结论:胃癌组织常发生维甲酸信号通路相关基因RARβ、CRBP1和TIG1启动子区高甲基化,高甲基化可能是相应基因转录失活的重要原因。

Background： Hypermethylation of promoter regions is associated with silencing of various tumor suppressor genes in gastric carcinoma. Aims： To investigate the promoter hypermethylation of retinoic acid signaling pathway-associated genes, such as retinoic acid receptor 13 （RAR13）, cellular retinol-binding protein 1 （CRBP1） and tazarotene-induced gene 1 （TIG1）, and their relationships with gastric carcinoma. Methods： Promoter methylation status of RAR13, CRBP1 and TIG1 was assessed by methylation-specific polymerase chain reaction （MSP） in 40 gastric cancer specimens, 10 normal gastric mucosal tissue specimens and 6 gastric cancer cell lines. The relevance between methylation status of these three genes and their relationships to the clinicopathological features of gastric carcinoma were analyzed. Expressions of mRNA of these three genes were measured by reverse transcriptase polymerase chain reaction （RT-PCR） in gastric cancer cell lines. Results： Of the 40 gastric cancer tissue specimens, the hypermethylation rates of RAR13, CRBP1 and TIG1 were 45.0%, 32.5% and 57.5%, respectively, while no hypermethylation was detected in 10 normal gastric mucosal tissue specimens （P〈0.05）. A statistically significant correlation was found in the hypermethylation status between RAR13 and CRBP1, RAR13 and TIG1, respectively （P〈0.05） in gastric cancer tissues, whereas no significant correlation was found between aberrant methylation of these three genes and clinicopathological features of gastric carcinoma. RT-PCR analysis showed that the expression of mRNA of these genes was absent or reduced in gastric cancer cell lines with methylated promoter regions. Conclusions： Aberrant promoter methylation of retinoic acid signaling pathway-associated genes such as RAR13, CRBP1 and TIG1 occur frequently in gastric cancer tissues. DNA hypermethylation may be the crucial step of gene transcription inactivation.