title: Downregulation of connexin 26 in human lung cancer is related to promoter methylation.
abstract: Cell-Cell communication via gap junctions plays a key role in carcinogenesis and in growth control. One of the gap junction proteins, Connexin 26 (Cx26) was considered as tumor suppressor in various cancers. In our study, the expression of Cx26 was analyzed in human lung cancer. The reduced mRNA expression was observed in 17 lung cancer cell lines examined by Northern blot analysis and RT-PCR. In 138 primary carcinomas comprising all subtypes analyzed by immunohistochemistry, 85 cases (62%) exhibited no expression of Cx26, whereas in other 53 cases the Cx26 staining was positive (38%). Additionally, an association between Cx26 protein expression and higher grading of tumors was found in whole tumor samples (p =0.028) but no statistically significant correlations could be observed with tumor stage, tumor size and node status. In squamous cell carcinoma, tumors with higher stage and grading were linked to higher expression of Cx26 (p = 0.015 and 0.017, respectively). To explore the mechanism responsible for the downregulation of Cx26, we treated 2 lung cancer cell lines H2170 and H226 with the demethylation agent 5-aza-2'-deoxycytidine and found the reexpression of Cx26 mRNA. Methylation status of these 2 cell lines was further analyzed by PCR amplification of bisulfite modified DNA and sequencing. A heterogeneous methylation pattern turned out. Our results suggest the inactivation of Cx26 in lung cancer may be explained by promoter methylation.
authors.affiliation: Institute of Pathology, University Hospital Charité, Berlin, Germany.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Chen
authors.forename: Daniela
authors.initials: D
authors.lastname: Hühn
authors.forename: Thomas
authors.initials: T
authors.lastname: Knösel
authors.forename: Manuela
authors.initials: M
authors.lastname: Pacyna-Gengelbach
authors.forename: Nicole
authors.initials: N
authors.lastname: Deutschmann
authors.forename: Iver
authors.initials: I
authors.lastname: Petersen
mesh_terms: D000199:Actins; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D015152:Blotting, Northern; D015139:Blotting, Southern; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000473:pathology; D045744:Cell Line, Tumor; D000072259:Connexin 26; D017630:Connexins / Q000235:genetics*; D019175:DNA Methylation / Q000187:drug effects; D015254:DNA Modification Methylases / Q000037:antagonists & inhibitors; D004273:DNA, Neoplasm / Q000378:metabolism*; D000077209:Decitabine; D015536:Down-Regulation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D006801:Humans; D007150:Immunohistochemistry; D008175:Lung Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology*; D011401:Promoter Regions, Genetic / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA
chemical_list: D000199:Actins; D000964:Antimetabolites, Antineoplastic; D017630:Connexins; D004273:DNA, Neoplasm; D004791:Enzyme Inhibitors; C000607042:GJB2 protein, human; D000072259:Connexin 26; D000077209:Decitabine; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D015254:DNA Modification Methylases; D001374:Azacitidine