Objective To investigate the correlation between the deletion of exon 13 of hMSH2 mRNA in peripheral blood leu-kocyte and ISV12(-6) T>C polymorphism with sporadic colorectal cancer .Methods Total RNA and genomic DNA were extracted from peripheral blood of colorectal cancer patients and healthy controls .RT-PCR and PCR were used to amplified the mRNA and exon 13 of hMSH2 gene .The sequences of amplified hMSH2 cDNA ,ISV12(-6) T>C polymorphism and exon 13 sequence were confirmed by DNA sequencing .Results 23 of 23 (100% ) patients and 31 of 35 controls (88 .6% ,P>0 .05) were found to have an hMSH2 truncated transcript caused by a deletion of exon 13 .No deletions of exon 13 in hMSH2 gene were identified in genomic DNA .16 of 23 patients (69 .5% ) and 19 of 35 control (52 .3% ,P>0 .05) were found to have the T >C transition six bases up-stream of exon 13 of hMSH2 .Conclusion Deletion of hMSH2 mRNA exon 13 in peripheral blood leukocyte and the ISV12(-6) T>C polymorphism are common variants in population and have no correlation with sporadic colorectal cancer .The variant of splice site ISV12(-6)T>C is not a reason causing the deletion of hMSH2 mRNA exon 13 .%目的：分析人外周血白细胞hMSH2基因mRNA外显子13缺失及hMSH2基因ISV12（-6）T＞C多态性与散发性结直肠癌的相关性。方法应用RT-PCR技术及PCR技术分别扩增hMSH2基因mRNA和hMSH2基因外显子13，用DNA测序技术测定扩增的hMSH2 cDNA序列、IVS12（-6）T＞C多态性和外显子13序列。结果23例结直肠癌样本hMSH2 mRNA均出现外显子13缺失的转录本，35例健康对照样本中31例出现hMSH2 mRNA外显子13缺失转录本，频率分别为100．0％和88．6％（P＞0．05）。23例结直肠癌患者及35例正常对照样本均未发现基因组hMSH2基因外显子13缺失，16例子结直肠癌样本及19例健康对照样本检出ISV12（-6）T＞C位点突变，频率分别为69．5％和52．3％（P＞0．05）。结论外周血白细胞hMSH2基因mRNA外显子13缺失及IVS12（-6）T＞C多态性是人群中是常见的变异，与散发性结直肠癌无相关性，剪接位点ISV12（-6） T＞C变异不是导致hMSH2基因mRNA外显子13缺失的原因。
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