| Objective:To investigate the levels of Aflatoxin B1(AFB1) DNA adducts in the human liver tissues from Nanning, Liuzhou and Guilin cities in Guangxi, Yinchuang city in Ningxia, and to explore the association between AFB1exposure and DNA damage repair.Methods:Formalin-fixed and paraffin-embeded liver tissues were collected from304cases of hepatocellular carcinoma (HCC) patients from Yinchuang of Ningxia province, Nanning, Liuzhou and Guilin cities of Guangxi province. One hundred ninty cases of liver tissue samples were collected from hemageoma and biliary calculi patients as controls. Immunohistochemistry method was used to detected the levels of AFB1DNA adducts,8-OHdG, hOGG1, MGMT and PARP-1. Polymerase Chain Reaction-restriction fragment length polymorphism assay (PCR-RFLP) was applied to detected the expression of P53gene. Life-style information was collected by questionnaire from226HBsAg(-) adult males in Nanning, their levels of AAA, PCC in plasma and AFB1,8-OHdG in urine were detected by ELISA.Results:1. In HCC group, the positive levels of AFB1-DNA adducts were59.5%(47/79) in Nanning,43.8%(39/89) in Liuzhou,17.4%(15/86) in Guilin and36%(18/50) in Yinchuang of Ningxia province. Higher levels of AFB1-DNA adducts in Nanning was found when it was compared with that in Guilin and Yinchuang (P<0.05). But in control group, no significant difference was found among them (P>0.05). The positive levels of AFB1-DNA adducts were15.5%(9/58) in Nanning,16.4%(9/55)in Liuzhou、10.8%(4/37)in Guilin and12.5%(5/40) in Yinchuang of Ningxia province, respectivly.2. In HCC group, the positive levels of8-OHdG were50.6%(40/79) in Nanning,51.7%(46/89) in Liuzhou,48.8%(42/86) in Guilin. No significant difference was observed among them (P>0.05). In control group, no significant difference was found among them, either (P>0.05). The positive levels of8-OHdG were55.2%(32/58),54.5%(30/55) and64.7%(24/37) in Nanning, Liuzhou and Guilin, individually.3. In HCC group, the positive rate of "hot spot mutation " of P53gene was21.7%(55/254)(P<0.001). In Nanning, Liuzhou and Guilin, the rate of "hot spot mutation " of P53gene were26.6%(21/79)、24.7(22/89)'14.0%(12/86), respectively. No statistically different was found among them (P>0.05) Furthermore, compared with subjects which AFB1-DNA adducts was negative, higher rate of "hot spot mutation" of P53gene was observed in patients which AFB1-DNA adducts was positive (x2=8.076, P=0.004)4. In HCC group, high levels of hOGGl were75.7%(60/79)、67.4%(60/89) and60.5%(52/86) in Nanning, Liuzhou and Guilin, respectively. Compared with normal control group, the highest level of expression of hOGG1was in Nanning (P<0.05). In HCC and control group of Nanning, positive correlation was found between hOGG1and AFB1-DNA adducts (P<0.05). But no statistically significant association was observed between Liuzhou and Guilin (P>0.05)5. For levels of MGMT in HCC group,51.4%(40/79),51.7%(46/89) and47.7%(41/86) were found in Nanning, Liuzhou and Guilin city, no significant difference was found among them. Their corresponding control group was 82.8%(48/58)、76.3%(42/55) and75.7%(28/37) of MGMT, no significant difference was observed among them. But in these three cities, higher expressions of MGMT was found in control groups when compared with their corresponding HCC group (P<0.05). No statistically significant association was observed between levels of MGMT and valves of AFB1-DNA adducts(P>0.05).6. In HCC group, expressions of PARP-1were89.9%(71/79),76.4%(68/89) and60.5%(52/86) in Nanning, Liuzhou and Guilin city. Statistical difference was found (%2=19.200, P<0.05).Their corresponding control groups were46.6%(27/58),60.0%(33/55) and40.5%(15/37). No significant difference was found(χ2=3.800, P=0.150). Positive correlation was observed between PARP-1and valves of AFB1-DNA adducts in HCC groups (x2=17.400, P=0.001), but not in control groups (x2=0.852, P=0.356)7. Univariate and multivariate analysis showed that occupation, smoking, alcohol, tea, dinning-out, food grain and oil whether the packaging and save time of rice significantly affect the level of AFB1exposure in adult males in Nanning city. Moreover, occupation, smoking, consumption of bulk grain and oil,vegetables and fruits intaking, significantly affect the level of oxidative stress in the participants.Conclusions:1. There are regional differences of AFB1-DNA adducts among Yinchuang of Ningxia province, Nanning, Liuzhou and Guilin cities of Guangxi province. AFB1exposure level in the southern part of Guangxi province is higher than those in the northern part of Guangxi and Yinchuang of Ningxia province. AFB1exposure is universal in Guangxi province. These data suggest that AFB1exposure contributes to HCC prevalence in Guangxi province. Moreover, complex life-style factors caused the AFB1exposure may increase the risk of HCC in Guangxi population.2. For levels of8-OHdG in liver tissues, no significant difference was found among Nanning, Liuzhou and Guilin cities of Guangxi province. The AFB1exposure failed to show a statistically significant association with8-OHdG expression.3. Compared with normal control, higher levels of hOGG1was observed in patients with HCC in Nanning, Liuzhou and Guilin cities of Guangxi province. hOGG1showed a close association with AFB1-DNA adducts in high AFB1exposure situation.4. Declining of DNA damage repair function which resulted from deletion of MGMT repairing protein expression may play an important role in the pathogenesis of HCC.5. The level of PARP-1expression in HCC was significant higher than those in healthy control. A declining tendency was found in Nanning, Liuzhou and Guilin group for the level of PARP-1.6. The high frequency "hotspot mutation" of P53gene in HCC patients in Guangxi, play an important role in AFB1exposured popualtion.7. The level of AFB1exposure and oxidative stress in adult males in Nanning city were affected by environment. |
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