title: Higher susceptibility of spontaneous and NNK-induced lung neoplasms in connexin 43 deficient CD1 × AJ F1 mice: paradoxical expression of connexin 43 during lung carcinogenesis.
abstract: Connexins (Cxs) are proteins that form the communicating gap junctions, and reportedly have a role in carcinogenesis. Here, we evaluated the importance of Connexin43 (Cx43) in spontaneous and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung carcinogenesis. Male wild-type (Cx43(+/+) ) and hemizygote (Cx43(+/-) ) CD1 × AJ F1 mice were injected with NNK or saline. After 60 weeks mice were euthanized; lung nodules were counted, measured, and fixed in formalin or snap frozen. Immunohistochemistry for Cx43 and Beta-catenin (β-catenin) was performed and Cx43 mRNA expression was evaluated by real-time PCR. Cx43 deletion significantly increased the incidence and number of spontaneous nodules in the CD1 × AJ F1 mice and the number of gross lesions and the aggressiveness of lesions in NNK-treated mice. Cx43 mRNA increased significantly and was correlated with the aggressiveness of tumors, although lesions from Cx43(+/-) mice expressed less Cx43 RNAm than their counterparts. Lung parenchyma presented a Cx43 immunostaining pattern with points or plaques between cells. In hyperplasias and adenomas, Cx43 was found in the membrane and in cytoplasm. Malignant lesions presented increased Cx43 in cytoplasm and a few membrane spots of immunostaining. β-catenin was weakly expressed in lung parenchyma. Though hyperplasias presented some cells with nuclear β-catenin, NNK-induced tumors contained a higher number of this staining pattern. Also, no difference in β-catenin occurred between both genotypes independently of the histological grade. In summary, our results indicate that Cx43 acts as a tumor suppressor gene in early lung tumorigenesis and loses this property in advanced carcinogenesis. Therefore, Cxs are better classified as conditional tumor suppressors.
authors.affiliation: Laboratory of Experimental and Comparative Oncology, Department of Pathology, School of Veterinary Medicine and Animal Sciences, University of Sao Paulo, Sao Paulo, Brazil.
authors.forename: Heidge
authors.initials: H
authors.lastname: Fukumasu
authors.forename: Jose L
authors.initials: JL
authors.lastname: Avanzo
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Sanches
authors.forename: Gregory
authors.initials: G
authors.lastname: Mennecier
authors.forename: Claudia M C
authors.initials: CM
authors.lastname: Mori
authors.forename: Maria L Z
authors.initials: ML
authors.lastname: Dagli
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002273:Carcinogens / Q000633:toxicity*; D002471:Cell Transformation, Neoplastic / Q000473:pathology*; D018031:Connexin 43 / Q000502:physiology*; D004198:Disease Susceptibility; D005260:Female; D007124:Immunoenzyme Techniques; D008175:Lung Neoplasms / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009602:Nitrosamines / Q000633:toxicity*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
chemical_list: D002273:Carcinogens; D018031:Connexin 43; C543076:GJA1 protein, mouse; D009602:Nitrosamines; D012333:RNA, Messenger; D051176:beta Catenin; C016583:4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone