肝细胞癌p53基因特异点突变的分子流行病学意义

MOLECULAR EPIDEMIOLOGIC SIGNIFICANCE OF AFLATOXIN B1 CHARACTERISTIC MUTATIONAL POINT IN HEPATOCELLULAR CARCINOMA

目的研究肝细胞癌（ＨＣＣ）ｐ５３基因突变热点的特异性及其分子流行病学意义。方法取广西高、中、低流行区ＨＣＣ样品，进行ＤＮＡ测序，并用限制性片段长度多态性（ＲＦＬＰ）分析。结果ＤＮＡ测序结果为２４９密码子第３碱基Ｇ→Ｔ颠换占５７％（２０／３５）。ＲＦＬＰ分析表明ＨａｅⅢ酶切点丢失占６９％（３６／５２），与低发区的１０％（１／１０）和２０％（２／１０）比较，差异有显著意义（Ｐ＜０．０１）。结论广西ＨＣＣ高发主要原因为黄曲霉毒素（ＡＦＢ１）高污染。ｐ５３基因突变集中于２４９第３碱基Ｇ→Ｔ颠换。这个由ＡＦＢ１介导的特异位点、固定形式（Ｇ→Ｔ）和高频率的ｐ５３突变，应称为“ＡＦＢ１突变点”，具有分子流行病学意义，可用于确定流行区不同个体ＨＣＣ由ＡＦＢ１介导和某些地区受ＡＦＢ１污染的情况。用ＲＦＬＰ替代ＤＮＡ测序可获同样效果。

The specific characteristic mutational hotspot of p53 gene and its molecular epidemiologic significance were studied. METHODS and RESULTS HCC samples were from different parts of Guangxi. Samples from the high and middle prevalant parts were detected and found p53 gene mutation cluster at codon 249 third base G to T transversion of the exon 7 by DNA direct sequencing, it presented in 57% (20/35) samples. Meantime, 69%(36/52) samples were found Hae Ⅲ enzyme allelic loss by methods of restriction fragment length polymorphism(RFLP) analysis. Compare to two low prevalent parts of Guangxi the rates were 1/10 by sequencing and 2/10 by RFLP respectively, the differences between high and low were significant ( P <0.01). CONCLUSIONS The principal risk fators responsible for HCC high prevalent in some parts of Guangxi is attributed to AFB1 severe contamination. AFB1 induced special p53 mutational point (249 third nucleotide), mutational form (G to T), and frequency (50%～60%)are stable and repeatable in HCC samples from any high AFB1 areas but not low areas so far as we know. Named“AFB1 mutational hot spot” would match the reality. Using it for molecular epidemiologic general survey of unknown AFB1 contaminated areas can achieve confident result, and also it can decide the HCC individuals whether inducing by AFB1 or not. RFLP instead of DNA direct sequencing achieve alike result.