SEMA3B基因在鼻咽癌组织中的表达、杂合性丢失和甲基化分析

SEMA3B基因定位于鼻咽癌高频缺失区域3p21.3上,最近被证明具有抑瘤基因的功能.分析了鼻咽癌组织中SEMA3B基因的表达、杂合性丢失(LOH)和甲基化情况.首先应用逆转录-聚合酶链式反应(RT-PCR)方法检测了33例鼻咽癌组织和15例慢性鼻咽炎组织中SEMA3B基因的表达,结果显示75.8%(25/33)鼻咽癌组织中SEMA3B基因表达缺失或下调,显著低于慢性鼻咽炎组织中的表达(P=0.001).进一步选取3个微卫星位点D3S1568、D3S1621和D3S4597分析了20例鼻咽癌组织中SEMA3B基因LOH的情况,结果表明3个位点的丢失率分别为10%、20%和15%,总的丢失率为45%,统计分析发现LOH与基因表达之间存在明显相关(P=0.023).最后,采用甲基化特异性PCR方法分析了SEMA3B基因启动子区甲基化,结果发现在100%的鼻咽癌组织和73.3%的慢性鼻咽炎组织中检测到SEMA3B基因启动子区高甲基化.由此得出结论,SEMA3B基因在鼻咽癌组织中表达缺失或下调,LOH是引起其表达异常的原因之一.

Expression, Allele Loss and Methylation of SEMA3B Gene in Nasopharyngeal Carcinoma

SEMA3B gene locates at 3p21.3,a region of high-frequency deletion in nasopharyngeal carcinoma (NPC),and its role as a tumor suppressor gene has been proved recently.In this study,the status of expression,allele loss and methylation of SEMA3B gene were investigated in NPC.We first detected the expression level of SEMA3B gene in 33 primary NPC tissues and 15 chronic nasopharyngitis tissues by RT-PCR.The RT-PCR results demonstrated that absent expression or down-regulation of SEMA3B gene were observed in 75.8% (25 of 35) of primary NPC tissues.The expression level of SEMA3B gene in NPC tissues was significantly lower than that in chronic nasopharyngitis tissues( P=0.001) .Using D3S1568,D3S1621 and D3S4597 microsatellites,we further analyzed the status of loss of heterozygosity (LOH) of SEMA3B gene in 20 primary NPC tissues.The results showed that the allele loss of D3S1568,D3S1621 and D3S4597 microsatellite was found in 10% ,20% and 15% of NPC tissues,respectively,that is,the total loss frequency of SEMA3B gene was detected in 45% of NPC tissues.Statistical analysis indicated that there was a significant correlation between the allele loss status of SEMA3B and its expression level(P=0.023). Finally,we measured the methylation of SEMA3B promoter region by methylation-specific PCR(MSP).The MSP results revealed that there was hypermethylation of SEMA3B promoter region in all tested primary NPC tissues and in 73.3% of chronic nasopharyngitis tissues.It is concluded that expression of SEMA3B gene is down-regulated or absent in NPC tissues and LOH should be one mechanism leading to its abnormal expression.