结直肠癌中胰岛素样生长因子结合蛋白-相关蛋白1表达上调与其5′CpG岛低甲基化的相关性

摘要

Objective To investigate the methylation status of 5' CpG island of insulin-like growth factor binding protein-related protein 1 (IGFBP-rP1) in colorectal cancer and its relationship with gene expression and clinicopathologic parameters.Methods Semi-quantitative reverse transcription-PCR (RT-PCR) was used to detect the expression of IGFBP-rP1 in 46 cases of colorectal cancer and their matched normal mucosa. Methylation-specific PCR (MSP) was applied to evaluate the methylation status of 5' CpG island of IGFBP-rP1. Colon cancer cell lines LoVo and SW620 were treated with demethylation agent 5-aza-2'-deoxycytidine (5-aza-dC), followed by RT-PCR and MSP detection. Results At the mRNA level, the expression of IGFBP-rP1 was higher in colorectal cancer tissue than that in the matched normal mucosa (P<0.05). IGFBP-rP1 was methylated in 28/46 (60.9%) cases of colorectal cancer and 37/46 (80.4%) matched normal mucosa samples (P<0.05). A negative correlation was found between IGFBP-rP1 expression and its methylation status. The expression of IGFBP-rP1 was restored in LoVo and SW620 after treatment with 5-aza-dC and MSP confirmation of its demethylation status. No relationships was found between the methylation status and clinicopathologic parameters. Conclusions IGFBP-rP1 expression is negatively correlated with its methylation status in colorectal cancer. DNA methylation is one of the mechanisms regulating the expression of IGFBP-rP1. Hypomethylation of IGFBP-rP1 gene with its overexpression plays an important role in the initiation and development of colorectal cancer.%目的 探讨胰岛素样生长因子结合蛋白-相关蛋白1(IGFBP-rP1)在结直肠癌中的表达改变并分析其与该基因5′CpG岛甲基化改变的关系.方法 采用半定量逆转录聚合酶链反应(RT-PCR)和甲基化特异性聚合酶链反应(MSP)检测46例结直肠癌组织和配对的正常黏膜中IGFBP-rP1基因的表达水平及5′CpG岛的甲基化状况,并通过T-A克隆、测序加以验证.不表达IGFBP-rP1基因的结肠癌细胞株LoVo和SW620经去甲基化药物5-氮-2′-脱氧胞苷(5-aza-2′-deoxycytidine,5-aza-dC)处理后,分别用RT-PCR和MSP检测IGFBP-rP1表达改变和甲基化状况.结果 mRNA水平上,IGFBP-rP1在结直肠癌组织中的表达水平高于配对的正常黏膜(P<0.01).在46例结直肠癌组织中,28例(60.9%)可检测到IGFBP-rP1基因5′CpG岛发生甲基化,而在配对的正常黏膜中,37例(80.4%)可检测到,二者差异有统计学意义(P<0.05).IGFBP-rP1基因的表达和甲基化水平之间存在负相关(P<0.05).5-aza-dC处理后,两株细胞均出现IGFBP-rP1基因的再表达,MSP法检测证实基因发生了去甲基化.结论 IGFBP-rP1基因的表达水平与5′CpG岛甲基化水平之间存在负相关.DNA甲基化是结直肠癌中IGFBP-rP1表达调控的一种机制.IGFBP-rP1低甲基化引起的基因表达上调可能与结直肠癌的发生发展有关.