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Possible involvement of O6-methylguanine formation and p53 dysfunction in mouse urinary bladder carcinogenesis
1Department of Pathology, Osaka City University Medical School, 1-4-3 Asahi-machi, Abeno-ku, 545-8585, Osaka, Japan. fukuchan@med.osaka-cu.ac.jp
Abstract:
The significance of O6-methylguanine formation in urinary bladder carcinogenesis was examined using O6-methylguanine-DNA methyltransferase (MGMT) transgenic mice carrying the ada gene. The ada MGMT transgenic mice demonstrated no differences in development of carcinogens-induced urinary bladder carcinomas compared with non-transgenic mice. Furthermore, no variation in p53 mutation frequency was evident between the two groups. The results indicated that other repair systems may have an important role for urinary bladder carcinogenesis. p53 knockout mice showed high sensitivity to urinary bladder carcinogens and increased cell proliferation plays an important role in urinary bladder carcinogenicity of p53 knockout mice. In addition, p53 knockout mice have an organ-specific increased sensitivity to carcinogenicity.
Insights
O6-methylguanine-DNA methyltransferase (MGMT) did not affect urinary bladder cancer development in transgenic mice. Other DNA repair pathways are crucial for bladder cancer, especially in p53 knockout mice.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- O6-methylguanine is a DNA adduct implicated in chemical carcinogenesis.
- O6-methylguanine-DNA methyltransferase (MGMT) is a key enzyme in repairing this adduct.
- The role of MGMT in urinary bladder carcinogenesis is not fully understood.
Purpose of the Study:
- To investigate the significance of O6-methylguanine formation in urinary bladder carcinogenesis.
- To evaluate the role of MGMT and p53 in this process using transgenic mouse models.
Main Methods:
- Utilized O6-methylguanine-DNA methyltransferase (MGMT) transgenic mice carrying the ada gene.
- Compared carcinogen-induced urinary bladder carcinomas in MGMT transgenic and non-transgenic mice.
- Assessed p53 mutation frequency in both groups.
- Examined p53 knockout mice for sensitivity to urinary bladder carcinogens.
Main Results:
- MGMT transgenic mice showed no difference in urinary bladder carcinoma development compared to non-transgenic controls.
- No significant variation in p53 mutation frequency was observed between the groups.
- p53 knockout mice exhibited heightened sensitivity to urinary bladder carcinogens.
- Increased cell proliferation was noted in p53 knockout mice, contributing to carcinogenicity.
Conclusions:
- MGMT activity does not appear to be a major determinant in urinary bladder carcinogenesis.
- Other DNA repair systems likely play a significant role.
- p53 deficiency confers organ-specific sensitivity to urinary bladder carcinogens, highlighting p53's critical role in preventing cancer initiation and progression.