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DNA mismatch repair genes in renal cell carcinoma
Masao Deguchi1, Hiroaki Shiina, Mikio Igawa
1Departments of Urology, Veterans Affairs Medical Center and University of California at San Francisco, San Francisco, California, USA.
Purpose:
DNA mismatch repair is one of the correcting mechanisms that preserves genetic stability during replication or chemically induced damage. We hypothesized that genetic instability is due to a defect in mismatch repair genes in renal cell carcinoma. To test this hypothesis mismatch repair genes hMLH1, hMSH2, hMSH3, hMSH6, hPMS1 and hPMS2 were analyzed in renal cell carcinoma cell lines and tissues. We further investigated the mechanisms of inactivation of these genes through CpG methylation pathways.
Materials And Methods:
We analyzed 41 fresh normal and renal cell carcinoma samples for gene and protein expression of various mismatch repair genes (hMLH1, hMSH2, hMSH3, hMSH6, hPMS1 and hPMS2) using reverse transcriptase-polymerase chain reaction and immunohistochemistry techniques. To investigate the mechanisms of inactivation of these genes cultured renal cancer cell lines (A498, Caki-1 and Caki-2) were treated with demethylating agent (5-aza-2'-deoxycytidine), and mismatch repair genes and protein expression were analyzed before and after treatment.
Results:
hMLH1 and hMSH3 mRNA expression was significantly lower in renal cell carcinoma tissues than in normal tissues. Similarly nuclear positivity of hMSH3 was significantly lower in renal cell carcinoma tissues than in normal tissues. Moreover, at the mRNA and protein levels hMSH3 expression in high grade renal cell carcinomas was significantly lower than in low grade tumors. However, there was no significant difference in hMSH2, hMSH6, hPMS1 or hPMS2 expression in renal cell carcinoma tissues versus normal kidney tissues. In renal cancer cell lines demethylation with 5-aza-2'-deoxycytidine did not affect the expression of hMLH1 and hMSH3 genes.
Conclusions:
To our knowledge this is the first comprehensive study demonstrating the down-regulation of mismatch repair genes in renal cell carcinoma. Selective defect in some mismatch repair genes can cause genomic instability and activate the malignant transformation as well as the progression of renal cell carcinoma.
Insights
Genetic instability in renal cell carcinoma may stem from defects in DNA mismatch repair genes. This study found lower expression of hMLH1 and hMSH3 in kidney cancer tissues, suggesting their role in tumor development.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- DNA mismatch repair (MMR) is crucial for maintaining genetic stability by correcting errors during DNA replication and repair.
- Defects in MMR genes are implicated in various cancers, but their specific role in renal cell carcinoma (RCC) requires further investigation.
Purpose of the Study:
- To investigate the expression of key MMR genes (hMLH1, hMSH2, hMSH3, hMSH6, hPMS1, hPMS2) in RCC.
- To explore potential mechanisms of MMR gene inactivation, including CpG methylation, in RCC.
Main Methods:
- Analysis of MMR gene and protein expression in 41 normal and RCC tissue samples using RT-PCR and immunohistochemistry.
- Treatment of RCC cell lines with a demethylating agent (5-aza-2'-deoxycytidine) to assess the impact on MMR gene expression.
Main Results:
- Significantly lower mRNA expression of hMLH1 and hMSH3 was observed in RCC tissues compared to normal tissues.
- Reduced nuclear positivity for hMSH3 protein in RCC tissues, with lower expression in high-grade tumors.
- Demethylation treatment did not restore hMLH1 or hMSH3 expression in RCC cell lines.
Conclusions:
- This study provides evidence for the down-regulation of specific MMR genes (hMLH1, hMSH3) in renal cell carcinoma.
- Defects in MMR genes may contribute to genomic instability, malignant transformation, and progression of RCC.