DNA mismatch repair genes in renal cell carcinoma.
OBJECTIVE
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.


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.
Deguchi
Masao
M
Departments of Urology, Veterans Affairs Medical Center and University of California at San Francisco, San Francisco, California, USA.
Shiina
Hiroaki
H
Igawa
Mikio
M
Kaneuchi
Masanori
M
Nakajima
Koichi
K
Dahiya
Rajvir
R
D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D020137:Base Pair Mismatch / Q000235:genetics*; D015153:Blotting, Western; D002292:Carcinoma, Renal Cell / Q000737:chemistry / Q000235:genetics*; D015254:DNA Modification Methylases / Q000037:antagonists & inhibitors; D004260:DNA Repair / Q000235:genetics*; D004273:DNA, Neoplasm / Q000235:genetics*; D000077209:Decitabine; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D020868:Gene Silencing / Q000187:drug effects; D006801:Humans; D007150:Immunohistochemistry; D007680:Kidney Neoplasms / Q000737:chemistry / Q000235:genetics*; D008297:Male; D009363:Neoplasm Proteins / Q000032:analysis / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured
D004273:DNA, Neoplasm; D009363:Neoplasm Proteins; D000077209:Decitabine; D015254:DNA Modification Methylases; D001374:Azacitidine