title: Altered expression of adhesion molecules and epithelial-mesenchymal transition in silica-induced rat lung carcinogenesis.
abstract: Loss of the epithelial phenotype and disruption of adhesion molecules is a hallmark in the epithelial-mesenchymal transition (EMT) reported in several types of cancer. Most of the studies about the relevance of adhesion and junction molecules in lung cancer have been performed using established tumors or in vitro models. The sequential molecular events leading to EMT during lung cancer progression are still not well understood. We have used a rat model for multistep lung carcinogenesis to study the status of adherens and tight junction proteins and mesenchymal markers during EMT. After silica-induced chronic inflammation, rats sequentially develop epithelial hyperplasia, preneoplastic lesions, and tumors such as adenocarcinomas and squamous cell carcinomas. In comparison with normal and hyperplastic bronchiolar epithelium and with hyperplastic alveolar type II cells, the expression levels of E-cadherin, alpha-catenin and beta-catenin were significantly reduced in adenomatoid preneoplastic lesions and in late tumors. The loss of E-cadherin in tumors was associated with its promoter hypermethylation. alpha- and beta-catenin dysregulation lead to cytoplasmic accumulation in some carcinomas. No nuclear beta-catenin localization was found at any stage of any preneoplastic or neoplastic lesion. Zonula occludens protein-1 was markedly decreased in 66% of adenocarcinomas and in 100% squamous cell carcinomas. The mesenchymal-associated proteins N-cadherin and vimentin were analyzed as markers for EMT. N-cadherin was de novo expressed in 32% of adenocarcinomas and 33% of squamous cell carcinomas. Vimentin-positive tumor cells were found in 35% of adenocarcinomas and 88% of squamous cell carcinomas. Mesenchymal markers were absent in precursor lesions, both hyperplastic and adenomatoid. The present results show that silica-induced rat lung carcinogenesis is a good model to study EMT in vivo, and also provide in vivo evidence suggesting that the changes in cell-cell adhesion molecules are an early event in lung carcinogenesis, while EMT occurs at a later stage.
authors.affiliation: Department of Histology and Pathology and Division of Oncology (Center for Applied Biomedical Research, CIMA), University of Navarra, Pamplona, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Blanco
authors.forename: Silvestre
authors.initials: S
authors.lastname: Vicent
authors.forename: Eider
authors.initials: E
authors.lastname: Elizegi
authors.forename: Irene
authors.initials: I
authors.lastname: Pino
authors.forename: Mario F
authors.initials: MF
authors.lastname: Fraga
authors.forename: Manel
authors.initials: M
authors.lastname: Esteller
authors.forename: Umberto
authors.initials: U
authors.lastname: Saffiotti
authors.forename: Fernando
authors.initials: F
authors.lastname: Lecanda
authors.forename: Luis M
authors.initials: LM
authors.lastname: Montuenga
mesh_terms: D000818:Animals; D001483:Base Sequence; D015820:Cadherins / Q000378:metabolism; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004247:DNA / Q000235:genetics; D019175:DNA Methylation; D004848:Epithelium / Q000378:metabolism / Q000473:pathology; D005260:Female; D007150:Immunohistochemistry; D008175:Lung Neoplasms / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology*; D008565:Membrane Proteins / Q000378:metabolism; D008648:Mesoderm / Q000378:metabolism / Q000473:pathology; D010750:Phosphoproteins / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D012822:Silicon Dioxide / Q000633:toxicity; D015534:Trans-Activators / Q000378:metabolism; D062826:Zonula Occludens-1 Protein; D051178:alpha Catenin; D051176:beta Catenin
chemical_list: D015820:Cadherins; D015815:Cell Adhesion Molecules; C495268:Ctnnb1 protein, rat; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D010750:Phosphoproteins; C569044:Tjp1 protein, rat; D015534:Trans-Activators; D062826:Zonula Occludens-1 Protein; D051178:alpha Catenin; D051176:beta Catenin; D012822:Silicon Dioxide; D004247:DNA