title: Expression of hypoxic marker CA IX is regulated by site-specific DNA methylation and is associated with the histology of gastric cancer.
abstract: The hypoxic marker carbonic anhydrase (CA) IX has been recognized as a tumor-associated protein and is essential for cancer development. However, because CA IX expression does not always correlate with hypoxia, its regulatory mechanism remains unclear. The objective of the present study was to clarify the role and regulation of CA IX expression in gastric cancer. The immunohistochemical expression of CA IX and hypoxia-inducible factor-1α was assessed in 77 patients with gastric cancer. A methylation-sensitive restriction enzyme method was used to quantify site-specific methylation at -74 bp in the CA9 promoter in tissue from patients with gastric cancer and in corresponding normal tissue. CA9 expression in cell lines was strongly dependent on methylation status but not hypoxic stimuli. In tissue from patients with gastric cancer, the quantity of methylation was significantly correlated with the protein expression (P = 0.003). Moreover, the methylation value was significantly lower in intestinal-type compared with diffuse-type cancer (P = 0.003). Compared with normal mucosa, intestinal-type cancer demonstrated significant hypomethylation, whereas diffuse-type cancer exhibited hypermethylation. In conclusion, expression of CA IX in gastric cancer is predominantly regulated by methylation of a single CpG rather than by hypoxia. Furthermore, epigenetic alterations in CA9 differ between the intestinal and diffuse types of gastric cancer.
authors.affiliation: Department of Surgery, Saga University Faculty of Medicine, Saga, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Nakamura
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Kitajima
authors.forename: Keita
authors.initials: K
authors.lastname: Kai
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Hashiguchi
authors.forename: Masatsugu
authors.initials: M
authors.lastname: Hiraki
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Noshiro
authors.forename: Kohji
authors.initials: K
authors.lastname: Miyazaki
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000951:Antigens, Neoplasm / Q000235:genetics* / Q000378:metabolism; D001374:Azacitidine / Q000494:pharmacology / Q000627:therapeutic use; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases / Q000235:genetics* / Q000378:metabolism; D015687:Cell Hypoxia / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D019175:DNA Methylation / Q000187:drug effects / Q000235:genetics*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology / Q000627:therapeutic use; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D007150:Immunohistochemistry; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D011401:Promoter Regions, Genetic / Q000235:genetics; D013274:Stomach Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics* / Q000473:pathology*
chemical_list: D000951:Antigens, Neoplasm; D006877:Hydroxamic Acids; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C012589:trichostatin A; C089226:CA9 protein, human; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases; D001374:Azacitidine