Expression of apurinic/apyrimidinic endonuclease-1 (APE-1) in H. pylori-associated gastritis, gastric adenoma, and gastric cancer.
OBJECTIVE
Apurinic/apyrimidinic endonuclease-1 (APE-1) is a key enzyme in DNA base excision repair (BER), linked to cancer chemosensitivity. However, little is known about the localization of APE-1 in Helicobacter pylori-infected gastric mucosa or its role in the development of gastric cancer. To investigate the role of APE-1 in the development of gastric cancer, we examined APE-1 expression and localization in cultured cells and gastric biopsies from patients with H. pylori-infected gastritis or gastric adenoma, and from surgically resected gastric cancer.


METHODS
APE-1 mRNA and protein expression were determined in H. pylori (CagA+) water-extract protein (HPWEP)-stimulated MKN-28 cells, gastric adenocarcinoma cell-line (AGS) cells, and human peripheral macrophages by real-time polymerase chain reaction and Western blot analysis. APE-1 expression and 8-OHdG as a measure of oxidative DNA damage were evaluated by immunostaining. Localization of APE-1 and IkappaBalpha phosphorylation in gastric adenoma and gastric cancer tissues were evaluated by single- and double-label immunohistochemistry.


RESULTS
In studies in vitro, HPWEP-stimulation significantly increased APE-1 mRNA expression levels in both MKN-28 cells and human peripheral macrophages. Hypo/reoxygenation treatment significantly increased APE-1 protein expression in HPWEP-stimulated MKN-28 cells. HPWEP stimulation significantly increased both APE-1 expression and IkappaBalpha phosphorylation levels in MKN-28 and AGS cells. In human tissues, APE-1 expression in H. pylori-infected gastritis without goblet cell metaplasia was significantly increased as compared to that in tissues from uninfected subjects. Eradication therapy significantly reduced both APE-1 and 8-OHdG expression levels in the gastric mucosa. APE-1 expression was mainly localized in epithelial cells within gastric adenoma and in mesenchymal cells of gastric cancer tissues. APE-1 expression in gastric cancer tissues was significantly reduced compared to that in H. pylori-infected gastric adenoma, while 8-OHdG index and IkappaBalpha phosphorylation levels did not differ between these two neoplastic tissue types. Co-localization of APE-1 and IkappaBalpha phosphorylation was observed not in gastric cancer cells but in gastric adenoma cells.


CONCLUSIONS
H. pylori infection is associated with increased APE-1 expression in human cell lines and in gastric tissues from subjects with gastritis and gastric adenomas. The observed distinct expression patterns of APE-1 and 8-OHdG in gastric adenoma and gastric cancer tissues may provide insight into the progression of these conditions and warrants further investigation.
Futagami
Seiji
S
Division of Gastroenterology, Department of Internal Medicine, Nippon Medical School, Tokyo, Japan. seiji-f@nms.ac.jp
Hiratsuka
Tetsuro
T
Shindo
Tomotaka
T
Horie
Akane
A
Hamamoto
Tatsuhiko
T
Suzuki
Kenji
K
Kusunoki
Masafumi
M
Miyake
Kazumasa
K
Gudis
Katya
K
Crowe
Sheila E
SE
Tsukui
Taku
T
Sakamoto
Choitsu
C
D000236:Adenoma / Q000201:enzymology / Q000235:genetics / Q000382:microbiology; D000328:Adult; D000368:Aged; D002478:Cells, Cultured; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000235:genetics / Q000378:metabolism*; D005260:Female; D005753:Gastric Mucosa / Q000378:metabolism / Q000382:microbiology; D005756:Gastritis / Q000201:enzymology* / Q000235:genetics / Q000382:microbiology*; D016481:Helicobacter Infections / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D016480:Helicobacter pylori; D006801:Humans; D008297:Male; D008875:Middle Aged; D012333:RNA, Messenger / Q000378:metabolism; D013274:Stomach Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000382:microbiology*
D012333:RNA, Messenger; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase