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[Carcinogenesis through abnormalities of DNA repair genes]
1First Department of Pathology, Hiroshima University School of Medicine.
Abstract:
Mechanisms of carcinogenesis through abnormalities of DNA repair genes are overviewed. Inactivation of DNA mismatch repair(MMR) gene(s) observed in tumors of hereditary non-polyposis colorectal cancer induces frameshift mutator mutation in MMR genes themselves, growth inhibitory genes and apoptosis inhibitory genes providing favorable genetic background for a malignant clone to be expanded. Deficiency of nucleotide excision repair that is usually employed for the removal of pyrimidine dimer formed by ultraviolet-irradiation in xeroderma pigmentosum (XP) causes hypersensitivity of the skin to sunlight as well as increased risk of skin cancer. Strand specificity and absence of hot spots for p53 tumor suppressor gene mutations was reported in ultraviolet induced skin cancers of XP model mice.
Insights
DNA repair gene abnormalities drive cancer by enabling mutations and uncontrolled cell growth. Defects in mismatch repair and nucleotide excision repair increase cancer risk, particularly in hereditary non-polyposis colorectal cancer and xeroderma pigmentosum.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Context:
- Carcinogenesis involves complex genetic alterations.
- DNA repair mechanisms are crucial for maintaining genomic stability.
- Defects in DNA repair are linked to hereditary cancer syndromes and environmental exposures.
Purpose:
- To overview the mechanisms of carcinogenesis driven by DNA repair gene abnormalities.
- To highlight the role of DNA mismatch repair (MMR) gene inactivation in hereditary non-polyposis colorectal cancer (HNPCC).
- To examine the impact of nucleotide excision repair (NER) deficiency in xeroderma pigmentosum (XP) on skin cancer development.
Summary:
- Inactivation of MMR genes in HNPCC tumors leads to frameshift mutations, promoting malignant clone expansion.
- NER deficiency in XP patients results in hypersensitivity to UV radiation and elevated skin cancer risk.
- UV-induced skin cancers in XP model mice show strand-specific, non-hotspot mutations in the p53 tumor suppressor gene.
Impact:
- Understanding these mechanisms is vital for cancer prevention and targeted therapies.
- Identifies key genetic vulnerabilities in hereditary cancer syndromes.
- Provides insights into the mutagenic pathways of UV-induced skin carcinogenesis.