Expression of the DNA repair enzyme, N-methylpurine-DNA glycosylase (MPG) in astrocytic tumors.
BACKGROUND
DNA is continuously damaged due to exposure to alkylating compounds or oxygen free radicals generated during normal cellular metabolism as well as to environmental mutagens. Several studies have shown that N-methylpurine-DNA-glycosylase (MPG) mRNA levels were lower in adult brain than in other tissues. Terminally differentiated and nonproliferating cells have a lower DNA repair capacity than proliferating cells from various organs, embryo, ovary and testis. If the DNA repair are not efficient, the damaged DNA may lead to tumorigenesis or cell death. This study was designed to investigate the association of tumorigenesis with MPG in astrocytic tumors.


METHODS
MPG mRNA expression and localization in astrocytic tumors and tumor-adjacent brain tissues was examined by reverse transcriptase-polymerase chain reaction (RT-PCR) and RNA in situ hybridization. The expression and intracellular localization of MPG protein was determined by immunohistochemistry.


RESULTS
MPG mRNA expression in RT-PCR was slightly higher in astrocytic tumor tissues than in brain tissues adjacent to tumor and in astrocytic tumor tissues, regardless of the tumor grades. MPG protein localization in immunohistochemical study was detected only in the nucleus of all tumor tissues. Interestingly, in brain tissues adjacent to tumor, immunohistochemical staining for MPG was not observed either in the nucleus or the cytoplasm. However, we could not detect MPG protein in the brain tissues adjacent to the tumor although MPG mRNA was detected in the tissues.


CONCLUSIONS
These results suggest an MPG's role in human astrocytic tumors and raise the possibility that the altered MPG expression and intracellular localization could be associated with astrocytic tumorigenesis.
Kim
Nam Keun
NK
Department of Biochemistry, Institute for Clinical Research, College of Medicine, Pochon CHA University, Sungnam 463-712, S. Korea.
Ahn
Jung Yong
JY
Song
Jihwan
J
Kim
Jin Kyeoung
JK
Han
Jin Hee
JH
An
Hee Jung
HJ
Chung
Hyung Min
HM
Joo
Jin Yang
JY
Choi
Joong Uhn
JU
Lee
Kyu Sung
KS
Roy
Rabindra
R
Oh
Doyeun
D
D001254:Astrocytoma / Q000201:enzymology* / Q000473:pathology; D001921:Brain / Q000201:enzymology; D001932:Brain Neoplasms / Q000201:enzymology* / Q000473:pathology; D002467:Cell Nucleus / Q000201:enzymology; D045647:DNA Glycosylases; D004260:DNA Repair; D004790:Enzyme Induction; D005909:Glioblastoma / Q000201:enzymology* / Q000473:pathology; D006801:Humans; D007124:Immunoenzyme Techniques; D017403:In Situ Hybridization; D009699:N-Glycosyl Hydrolases / Q000032:analysis / Q000502:physiology*; D009363:Neoplasm Proteins / Q000032:analysis / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D012334:RNA, Neoplasm / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction
D009363:Neoplasm Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; C076131:DNA-3-methyladenine glycosidase II