Related Experiment Videos
Long-term persistence of DNA alkylation in hamster tissues after N-nitrosobis(2-oxopropyl)amine
1Division of Chemical Carcinogenesis, The Netherlands Cancer Institute, (Antoni van Leeuwenhoek Huis), Amsterdam.
Abstract:
The persistence of 7- and O6-alkylation of guanine in DNA of cell nuclei of male Syrian hamster pancreas, liver, kidneys, lungs [target tissues of N-nitrosobis(2-oxopropyl)amine (BOP)] and salivary glands (nontarget tissue) was studied immunocytochemically 6 h, 1, 3, 7, 14, 28, and 56 days after a single s.c. injection of 20 mg BOP/kg. Conventional antisera raised against O6-methylguanine and imidazole-ring-opened 7-methyl-guanine were used. Persistent alkyl-specific staining was observed for up to 7 days (7-alkylguanine) or 56 days (O6-alkylguanine) in inter- and intralobular duct cells and centro-acinar cells of the pancreas, periportal hepatocytes and bile duct cells of the liver, cells of the proximal convoluted tubules of the renal cortex, and bronchiolar Clara and alveolar cells in the lungs. Both adducts disappeared from centrilobular liver cells within 1 day, from pancreatic acinar cells within 3 days, and from ducts and acini of the submandibular salivary glands within 14 days after BOP treatment. A high level of persistent O6-alkylation of guanine was related with a high tumor incidence only in case of the ductal/ductular system of the pancreas, the main target tissue of BOP-induced carcinogenesis. The relatively weak carcinogenicity of BOP in other tissues with long-term persistence of O6-alkylguanine in DNA indicates that the formation and persistence of DNA alkylation are not sufficient to account for the carcinogenic organotropism of BOP. Additional factors, such as cell proliferation, appropriate promoting stimuli and the (onco)genes critically involved, may be as important as the modification of DNA.
Insights
DNA adducts 7-alkylguanine and O6-alkylguanine persistence varied by tissue after N-nitrosobis(2-oxopropyl)amine (BOP) exposure. Persistent O6-alkylation correlated with tumor incidence only in the pancreas, suggesting other factors influence BOP
Area of Science:
- Toxicology
- Carcinogenesis
- Molecular Biology
Background:
- N-nitrosobis(2-oxopropyl)amine (BOP) is a carcinogen targeting specific organs.
- DNA alkylation, particularly guanine modification, is a key mechanism in chemical carcinogenesis.
- Understanding DNA adduct persistence is crucial for elucidating organ-specific toxicity.
Purpose of the Study:
- To investigate the temporal persistence of 7- and O6-alkylation of guanine in DNA adducts.
- To compare adduct persistence in target (pancreas, liver, kidneys, lungs) and non-target (salivary glands) tissues following BOP exposure.
- To correlate DNA adduct levels with carcinogenic organotropism of BOP.
Main Methods:
- Single subcutaneous injection of N-nitrosobis(2-oxopropyl)amine (BOP) in male Syrian hamsters.
- Immunocytochemical detection of 7-methylguanine and O6-methylguanine DNA adducts.
- Analysis of DNA adducts at multiple time points (6 hours to 56 days) post-injection.
Main Results:
- Persistent 7-alkylguanine (up to 7 days) and O6-alkylguanine (up to 56 days) were detected in target tissues.
- Adducts cleared faster in non-target salivary glands (within 14 days) and some liver/pancreas cells.
- High O6-alkylguanine persistence correlated with tumor incidence only in the pancreatic ductal system.
Conclusions:
- DNA alkylation persistence alone does not fully explain BOP's organ-specific carcinogenicity.
- Factors beyond DNA modification, including cell proliferation and genetic events, are critical for carcinogenic organotropism.
- Further research is needed to understand the complex interplay of factors determining BOP's carcinogenic effects.