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Chemical and physical carcinogenesis: advances and perspectives for the 1990s
1Laboratory of Human Carcinogenesis, National Cancer Institute, NIH, Bethesda, Maryland 20892.
Abstract:
Carcinogenesis is a multistage process driven by carcinogen-induced genetic and epigenetic damage in susceptible cells that gain a selective growth advantage and undergo clonal expansion as the result of activation of protooncogenes and/or inactivation of tumor suppressor genes. Therefore, the mutational spectra of chemical and physical carcinogens in these critical genes are of interest to define endogenous and exogenous mutational mechanisms. The p53 tumor suppressor gene is ideally suited for analysis of the mutational spectrum. Such an analysis has revealed evidence for both exogenous and endogenous molecular mechanisms of carcinogenesis. For example, an informative p53 mutational spectrum of frequent G----T transversions in codon 249 is found in hepatocellular carcinomas from either Qidong, People's Republic of China, or southern Africa. This observation links exposure to aflatoxin B1, a known cancer risk factor in these geographic regions, with a specific mutation in a cancer-related gene. Other studies indicate that abnormalities in genes controlling the cell cycle may cause genomic instability and increase the probability of neoplastic transformation. Finally, mechanistic understanding of carcinogenesis is leading to improved cancer risk assessment and to the identification of individuals at high cancer risk.
Insights
Analyzing p53 gene mutations reveals how carcinogens cause cancer. Specific mutations, like those linked to aflatoxin B1, help define cancer-causing mechanisms and improve risk assessment.
Area of Science:
- Molecular Biology
- Genetics
- Cancer Research
Background:
- Carcinogenesis is a multistage process involving genetic and epigenetic damage.
- Protooncogene activation and tumor suppressor gene inactivation drive cancer cell growth.
- Understanding carcinogen-induced mutations is key to defining cancer mechanisms.
Purpose of the Study:
- To analyze the mutational spectrum of the p53 tumor suppressor gene.
- To identify endogenous and exogenous molecular mechanisms of carcinogenesis.
- To link specific carcinogen exposures to distinct genetic mutations.
Main Methods:
- Analysis of p53 tumor suppressor gene mutational spectra.
- Investigating mutations in genes controlling the cell cycle.
- Correlating geographic cancer data with specific genetic alterations.
Main Results:
- The p53 gene is well-suited for analyzing mutational spectra.
- Specific p53 mutations, such as G----T transversions in codon 249, are linked to aflatoxin B1 exposure in hepatocellular carcinomas.
- Abnormalities in cell cycle genes contribute to genomic instability and cancer risk.
Conclusions:
- Mutational spectrum analysis of p53 provides evidence for both exogenous and endogenous carcinogenesis mechanisms.
- Identifying specific carcinogen-mutation links, like aflatoxin B1 and p53 codon 249 mutations, enhances cancer risk assessment.
- Mechanistic insights into carcinogenesis aid in identifying high-risk individuals.