Abstract
This study was conducted to investigate the modifying effect of glutathione S-transferase (GST) M1 and T1 polymorphisms on aflatoxin-induced hepatocarcinogenesis among chronic hepatitis B virus surface antigen (HBsAg) carriers. A total of 79 HBsAg-positive cases of hepatocellular carcinoma (HCC) diagnosed between 1991 and 1997 were identified and individually matched to one or two HBsAg-positive controls on age, gender, residence and date of recruitment from the same cancer screening cohort in Taiwan. Blood samples were tested for hepatitis B and C viral markers by enzyme immunoassay and for aflatoxin B(1) (AFB(1))-albumin adducts by competitive enzyme-linked immunosorbent assay. GSTM1 and GSTT1 genotypes were determined by PCR. There was a statistically significant relationship between detectable levels of AFB(1)-albumin adducts in serum and risk of HCC among chronic HBsAg carriers, with an adjusted odds ratio (OR) of 2.0 [95% confidence interval (CI) 1.1-3.7]. In addition, the effect of aflatoxin exposure on HCC risk was more pronounced among chronic HBsAg carriers with the GSTT1 null genotype (OR 3.7, 95% CI 1.5-9.3) than those who were non-null (OR 0.9, 95% CI 0.3-2.4). The interaction between serum AFB(1)-albumin adduct level and GSTT1 genotype was statistically significant (P = 0.03). For GSTM1 the effect of aflatoxin exposure on HCC risk in those with the null genotype was also greater (adjusted OR 2.8, 95% CI 1.0-7.8) than in those with the gene present (adjusted OR 1.8, 95% CI 0.8-4.5), but the difference was not significant (P = 0.91). Notably, when the interaction between aflatoxin exposure and GSTT1 genotype was considered, aflatoxin exposure by itself was not a significant determinant of HCC risk among chronic HBsAg carriers. These results demonstrate the importance of gene-environment interactions in the multifactorial development of HCC.
Highlights
IntroductionPrimary hepatocellular carcinoma (HCC) is a tumor that occurs at high frequencies in southeast Asia and tropical Africa [1]
Primary hepatocellular carcinoma (HCC) is a tumor that occurs at high frequencies in southeast Asia and tropical Africa [1].In Taiwan HCC is the leading cancer in males and the fifth in females [2]
Aflatoxin B1 (AFB1) has long been suspected to play an etiological role in human hepatocellular carcinogenesis, largely because it produces liver tumors when administered to animals [23]
Summary
Primary hepatocellular carcinoma (HCC) is a tumor that occurs at high frequencies in southeast Asia and tropical Africa [1]. In Taiwan HCC is the leading cancer in males and the fifth in females [2]. HCC is a complex and multifactorial disease that is linked to both viral and chemical carcinogens [3,4,5,6,7]. On the basis of epidemiological evidence, 70–90% of HCC patients in Taiwan are seropositive for hepatitis B virus surface antigen (HBsAg) or antibodies to hepatitis C virus (HCV) [5], indicating that hepatotropic viral infections are major causes of HCC in this area. There are nonviral causes in 10–30% of HCC cases.
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