The Study Of Aflatoxin Exposure In Liver Tissues From Residents In Nanning, Liuzhou And Guilin Cities, Guangxi, China

Objective: We investigate the levels of Aflatoxin B1 (AFB₁) DNA adducts in the human liver tissues from Nanning, Liuzhou and Guilin cities in Guangxi, China, to explore wheather there is geographical differences of AFB₁ exposure in this region and its association with hepatocarcinogenesis.Methods: 254 liver tissues from hepatocellular carcinoma (HCC) and no-HCC controls from Nanning , Liuzhou and Guilin cities of Guangxi province, were categorized into Nanning HCC group (79 cases) , Nanning controls (58 cases) ; Liuzhou HCC group (89 cases), Liuzhou controls (55 cases) ; Guilin HCC group (86 cases), Guilin controls (37 cases). Immunohistochemistry method was used to detected the levels of AFB₁-DNA adducts and Polymerase Chain Reaction-restriction fragment length polymorphism assay was used to detected the G→T mutation at the third base at 249 codon of p53 gene.Results: AFB₁-DNA adducts was detected in 39.8% (101/254) HCC and 14.7% (22/150) non-HCC liver tissues(χ²=28.051,P<0.001); there is a declining tendency of detection rate of this adduct from southern to northern Guangxi : Nanning HCC group(47/79, 59.5%), Liuzhou HCC group(39/89, 43.8%) and Guilin HCC group(15/86, 17.4%). There were significant difference of adduct detection rate between Nanning HCC group and Guilin HCC group(χ²=31.042, P<0.001), and between Liuzhou HCC group and Guilin HCC group(χ²=14.264, P<0.001), while were not significant difference of adduct detection rate between Nanning HCC group and Liuzhou HCC group(χ²=4.115 , P=0.043),The"hot spot mutation"of p53 gene was detected in 21.7% (55/254) HCC ; the difference of mutation rate between Nanning HCC group (21/79, 26.6%) and Guilin HCC group (12/86, 14.0%) , between Nanning HCC group (21/79, 26.6%) and Liuzhou HCC group(22/89, 24.7%), between Liuzhou HCC group(22/89, 24.7%)and Guilin HCC group(12/86, 14.0%)were no significant (χ²=4.104, P=0.043;χ²=0.076, P=0.782 ;χ²=3.238, P=0.072, respectively).HCC patients in Nanning HCC Group, Liuzhou HCC group and Guilin HCC group who positive for AFB₁-DNA adducts beared higher frequency of p53-249codon mutation than those negative for the AFB₁-DNA adducts., the statistic power in Nanning HCC group was significant((χ²=5.466,P=0.019), whilst it was not in Liuzhou HCC group(χ²=1.366,P=0.243) and Guilin HCC group(χ²=0.006,P=0.939); 254 cases of HCC with AFB₁-DNA adduct positive (31/101, 30.7%) was also higher mutation than negative ones (24/153, 15.7%), the difference was significant (χ²=8.076,P=0.004)Conclusions: AFB₁ exposure level is higher in the southern part of Guangxi province. AFB₁ exposure contributes to HCC prevalence in Guangxi province. The high frequency " hotspot mutation" of p53 gene in HCC patients in Guangxi also support this exposure.