原发性肝癌的等位基因型及肿瘤抑制基因p53第七外显子分析

Study of allelotype and suppressor gene p53 exon 7 in primary hepatocellular carcinoma

作者应用Southern杂交和PCR扩增技术,分析了45例配对的原发性肝癌及其癌旁肝组织的等位基因型和p53第七外显子的突变状况.共应用了位于14对染色体的31个基因标志,结果在8对染色体的19个基因位点出现不同程度的杂合型丢失(LOH),丢失频率3.2％～23.5％.其中第6对染色体的pJCZ30位点的LOH为首次报告.应用PCR扩增后限制性酶切,分析了p53第七外显子的229,247和249三个密码子,结果仅2例癌组织分别在247和249密码子出现点突变.本实验结果表明,原发性肝癌的分子遗传学变化是复杂的,不同原因(HBV,黄曲霉毒素)相关的原发性肝癌,其等位基因的变化和LOH的频率存在差异,特别是p53基因第249密码子的特征性点突变差别显著,说明原发性肝癌的发生是一多基因变化,多步骤的过程.

Allelotype and point mutation of p53 exon 7 were detected in 45 pairs of primary hepatocellular carcinoma (PHC) by restriction fragment length polymorphism (RFLP) and polymerase chain reaction (PCR). Thirty -one gene markers covered 14 chromosomes were used including suppressor genes p53 and RB1. The results showed 19 gene markers covered 8 chromosomes revealed loss of heterozygosity. Six of 28 informative cases showed loss on 6q21 using probe pJCZ30, which had not been reported before. The allele loss was low frequent on the other chromosomes including p53 and RBI.Fourty-five cases of PHC from areas of low aflatoxin Bl (AFB1) exposure but high risk to HBV were examined for identifying point mutation of p53 exon 7 by PCR and restriction enzyme analysis using Rsa Ⅰ, Msp Ⅰ, Hae Ⅲ site at codon 229, 247 and 249, respectively. Two of 45 cases showed point mutation at codon 247 and 249, respectively. Our results indicated that changes of molecular genetics on PHC is a complex event, and there are multiple steps, and multiple genes are involved in hepatocarcinogenesis. Meanwhile, the results supported the postulated role of AFB1 together with HBV in the generation of specific mutation of the p53 gene provide evidence to suggest that HBV infection alone-or exposure to AFB1 alone do not contribute to these base changes.