Overexpression of the hOGG1 gene and high 8-hydroxy-2'-deoxyguanosine (8-OHdG) lyase activity in human colorectal carcinoma: regulation mechanism of the 8-OHdG level in DNA.
8-Hydroxy-2'-deoxyguanosine (8-OHdG) is one of the most abundant oxidatively modified lesions in DNA. Our previous study (Kondo et al, Free Radic. Biol. Med., 27: 401-410, 1999) revealed that human colorectal carcinoma cells are oxidatively stressed based on 8-OHdG determination. To elucidate 8-OHdG metabolism and its clinical significance in colorectal carcinoma, we studied the 8-OHdG repair system in DNA by measuring specific lyase activity and hOGG1 expression using quantitative-competitive reverse transcription-PCR. In addition, we searched for the presence of mutations and single nucleotide polymorphisms of the hOGG1 gene by single-strand conformational polymorphism and sequencing analyses. It was found that 8-OHdG-specific lyase activity and hOGG1 expression were significantly up-regulated in carcinoma, and a proportional association between 8-OHdG levels and either 8-OHdG lyase activity (r = 0.641, P < 0.05) or hOGG1 expression (r = 0.702, P < 0.05) was present. Whereas no difference was detected in the 8-OHdG level between early- and advanced-stage cancer, lyase activity (1.2-fold) and hOG1 expression (1.6-fold) were significantly increased in advanced-stage cancer. No mutation was found in the 25 tumors examined. Three kinds of single nucleotide polymor. phism were observed, including that of codon 326 (Ser/Cys) in exon 7. However, there was no correlation between any of the three polymorphic patterns and either 8-OHdG level or lyase activity. These results suggest that increased 8-OHdG levels in colorectal carcinoma are attributed to increased formation and are maintained by induced 8-OHdG repair activity at appropriate high levels. Our results may offer a unique approach in the development of preventive and therapeutic interventions as well as new insights into the pathogenesis of colorectal carcinoma.
Kondo
S
S
Department of Pathology and Biology of Diseases, Graduate School of Medicine, Kyoto University, Japan.
Toyokuni
S
S
Tanaka
T
T
Hiai
H
H
Onodera
H
H
Kasai
H
H
Imamura
M
M
D000080242:8-Hydroxy-2'-Deoxyguanosine; D019757:Carbon-Oxygen Lyases / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D015179:Colorectal Neoplasms / Q000201:enzymology* / Q000235:genetics; D004252:DNA Mutational Analysis; D004273:DNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D043382:DNA-Formamidopyrimidine Glycosylase; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000378:metabolism; D043223:Deoxyribonuclease IV (Phage T4-Induced); D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D009699:N-Glycosyl Hydrolases / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D018807:Polymorphism, Single-Stranded Conformational; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012334:RNA, Neoplasm / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods
D004273:DNA, Neoplasm; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D000080242:8-Hydroxy-2'-Deoxyguanosine; D043223:Deoxyribonuclease IV (Phage T4-Induced); D009699:N-Glycosyl Hydrolases; D043382:DNA-Formamidopyrimidine Glycosylase; D019757:Carbon-Oxygen Lyases; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D003849:Deoxyguanosine