Polycyclic aromatic hydrocarbon‐DNA adducts in liver tissues of hepatocellular carcinoma patients and controls

Abstract

HCC is a common cancer and HBV and AFB 1 are welldocumented, major risk factors. Epidemiologic studies have documented that cigarette smoking also contributes to the development of HCC. PAHs are ubiquitous environmental pollutants and products of incomplete combustion. They are present in both mainstream and sidestream cigarette smoke. PAHs are metabolically activated by phase I enzymes, including CYP1A1, into electrophilic reactants (diol epoxides), which covalently bind to DNA to form adducts. Diol epoxides are also substrates for phase II detoxifying enzymes, including GSTM and GSTP. To examine the association between PAH-DNA adducts and HCC, adduct levels were determined in liver tissue by relative staining intensity with an immunoperoxidase method using a polyclonal antiserum against BPDE-modified DNA. Subjects were also genotyped for polymorphism in several genes involved in the metabolism of PAH, including GSTM1 and GSTP1. Liver tissue was collected from patients with histologically confirmed HCC (n ‫؍‬ 105) and from non-HCC controls (n ‫؍‬ 37). There was a significant positive correlation (r ‫؍‬ 0.3, p < 0.01) between adducts in tumor and adjacent nontumor tissues among HCC cases. The risk of HCC was higher after adjustment for age, sex and HBsAg in the group with the highest tertile tissue levels of PAH-DNA adducts (mean relative nuclear staining intensity of tumor and nontumor tissue > 344) than in the group with the lowest tertile (staining < 241, OR ‫؍‬ 3.9, 95% CI ‫؍‬ 1.0 -14.9). Among non-HCC controls, there were no significant associations between adduct levels and cigarette smoking, GSTM1 null genotype and HBsAg positivity. A strikingly increased HCC risk was observed (OR ‫؍‬ 20.3, 95% CI ‫؍‬ 5.0 -81.8) among HBsAg-positive subjects whose PAH-DNA adduct levels were high (mean relative nuclear staining intensity of tumor and nontumor tissue > 301, median of control tissues) compared to HBsAg-negative subjects who had low PAH-DNA adduct levels. 4-ABP-and AFB 1 -DNA adducts had been measured previously in these same tissues. Subjects with elevated DNA adduct levels of PAH, 4-ABP and AFB 1 had a significantly higher HCC risk with an OR of 36.7 (95% CI 7.2-187.2) compared to those who had low DNA adduct levels. These results suggest that PAHs may play a role in human hepatocarcinogenesis in conjunction with HBsAg carrier status, GSTM1 and GSTP1 genotypes and exposure to 4-ABP and AFB 1 . © 2002 Wiley-Liss, Inc.Key words: PAH-DNA adduct; hepatocellular carcinoma; HbsAg; GSTM1; GSTP1 HCC is one of the major malignant neoplasms in the world, especially in sub-Saharan Africa and Southeast Asia, including Taiwan. 1,2 Previous studies have indicated that HCC is an environmentally related cancer, with both viral and chemical carcinogens involved in the multistage process. HBV is hyperendemic in Taiwan and chronic HBV infection has been well documented as an important HCC risk factor. 2,3 In addition to HBV, chronic infection with hepatitis C virus, consumption of dietary aflatoxins and alcohol and low consum...

N‐Acetyltransferase‐2, glutathione S‐transferase M1 and T1 genetic polymorphisms, cigarette smoking and hepatocellular carcinoma: A case‐control study

“…26,27 Furthermore, a strong correlation has been found between HCC and DNA adducts induced by polycyclic aromatic hydrocarbon. 28 Tobacco smoking was indicated as a risk factor for liver cancer in a previous review. 4 Apart from this, no role of tobacco smoking in the development of HCC has been found in other case-control studies 29,30 and some large prospective studies among Asians.…”

Southern Europe as an example of interaction between various environmental factors: a systematic review of the epidemiologic evidence

“…Furthermore, a strong correlation has been observed between HCC risk and DNA-adducts of 4-aminobiphenyl and polycyclic aromatic hydrocarbons, which are animal carcinogens and components of tobacco smoking (Wang et al, 1998;Chen et al, 2002).…”

Environmental Carcinogenic Polycyclic Aromatic Hydrocarbons: Photochemistry and Phototoxicity

“…It is generally accepted that formation of diolepoxide-derived DNA adducts is the principal metabolic activation pathway leading to cancer initiation (13,15,(24)(25)(26) (Figure 2). The diolepoxide metabolites, particularly the bay-region diolepoxides, can react with DNA to form covalently bound DNA adducts (2)(3)(4)(13)(14)(15).…”

“…In these experiments, the amount of DNA single strand cleavage depends on both light and PAH doses. Therefore, by fixing the light dose at 170 J/cm 2 (1 hour irradiation), a relative DNA photocleavage efficiency indicator, C 25 , the concentration at which 25% of the original supercoiled DNA is converted into relaxed, open circular DNA upon the combination of a PAH and light irradiation is determined. The C 25 can be used for comparing relative DNA photocleavage efficiency for various PAHs.…”

“…Relative DNA single strand cleavage efficiencies (C 25 ) for selected PAHs in aqueous solutions (10 mM sodium phosphate at pH 7 in 4% dimethylformamide). …”