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Increased expression of CHK2 in human gastric carcinomas harboring p53 mutations
Hideo Shigeishi1, Hiroshi Yokozaki, Naohide Oue
1First Department of Pathology, Hiroshima University Faculty of Medicine, Hiroshima, Japan.
Abstract:
Human Chk1 and Chk2 are DNA damage-activated protein kinases that function as downstream mediators of ataxia-telangiectasia mutated (ATM), which is involved in G(2)/M cell cycle arrest. To clarify the relation between the expression of Chk1/Chk2 and p53 gene status in human gastric carcinomas, we examined expression of Chk1, Chk2 and p53 proteins in 87 gastric carcinomas by Western blotting and immunohistochemistry. We found a significant correlation between the expression levels of Chk1 and p53 proteins in gastric carcinomas (p = 0.016). Significant statistical association was also observed between levels of Chk2 and p53 proteins (p = 0.00024). To clarify the genetic alterations of p53 in gastric carcinomas, we performed PCR-SSCP analysis on 47 gastric carcinomas. Although we found that 5 of 7 (71%) gastric cancers expressed elevated levels of Chk1 had p53 mutation, there was not a statistically significant correlation between expression of Chk1 and genetic status of p53. We also found that 7 of 11 (78%) gastric carcinomas expressed elevated levels of Chk2 had p53 mutation, and this correlation was significant (p = 0.0157). We used a highly quantitative 5' nuclease fluorogenic RT-PCR method (TaqMan) to analyze the expression of Chk2 mRNA in 22 gastric carcinomas. Chk2 mRNA expression was higher in gastric carcinomas with p53 mutations compared to those harboring wild-type p53. A significant association was recognized between the expression of Chk2 mRNA and p53 mutational status (p = 0.031). Our findings support the hypothesis that expression of Chk2 protein is increased in gastric carcinomas with mutant p53. Chk1 and Chk2 may play important roles in the checkpoint function in human gastric carcinomas harboring p53 mutation when their functions are preserved to prevent cell cycle progression.
Insights
Checkpoint kinases Chk1 and Chk2 are linked to p53 status in gastric cancer. Elevated Chk2 expression correlates with p53 mutations, suggesting a role in DNA damage response for gastric carcinomas.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Human Chk1 and Chk2 are protein kinases mediating DNA damage response and cell cycle arrest.
- Ataxia-telangiectasia mutated (ATM) is upstream of Chk1/Chk2 in the DNA damage pathway.
- p53 is a critical tumor suppressor gene often altered in cancer.
Purpose of the Study:
- To investigate the relationship between Chk1/Chk2 expression and p53 gene status in human gastric carcinomas.
- To determine the functional implications of these relationships in gastric cancer progression.
Main Methods:
- Western blotting and immunohistochemistry to assess Chk1, Chk2, and p53 protein levels in 87 gastric carcinomas.
- PCR-SSCP analysis to identify p53 gene mutations in 47 gastric carcinomas.
- Quantitative RT-PCR (TaqMan) to analyze Chk2 mRNA expression in 22 gastric carcinomas.
Main Results:
- Significant correlations were found between Chk1 and p53 protein expression (p=0.016) and Chk2 and p53 protein expression (p=0.00024).
- Elevated Chk2 expression showed a significant association with p53 mutations (p=0.0157) and higher Chk2 mRNA levels (p=0.031).
- Chk1 expression did not show a statistically significant correlation with p53 genetic status.
Conclusions:
- Chk2 protein expression is increased in gastric carcinomas with mutant p53.
- Chk1 and Chk2 may play crucial roles in checkpoint function in gastric carcinomas with p53 mutations.
- These findings support the role of Chk2 in the DNA damage response pathway in p53-mutated gastric cancers.