Adhesion to type I collagen fibrous gels induces E- to N-cadherin switching without other EMT-related phenotypes in lung carcinoma cell A549

Abstract

In culture system, environmental factors, such as increasing exogenous growth factors and adhesion to type I collagen (Col-I) induce epithelial-to-mesenchymal transition (EMT) in cells. Col-I molecules maintain a non-fibril form under acidic conditions, and they reassemble into fibrils under physiological conditions. Col-I fibrils often assemble to form three-dimensional gels. The gels and non-gel-form of Col-I can be utilized as culture substrates and different gel-forming state often elicit different cell behaviors. However, gel-form dependent effects on cell behaviors, including EMT induction, remain unclear. EMT induction in lung cancer cell line A549 has been reported via adhesion to Col-I but the effects of gel form dependency are unelucidated. This study investigated the changes in EMT-related behaviors in A549 cells cultured on Col-I gels.

We examined cell morphology, proliferation, single-cell migration and expression of EMT-related features in A549 cells cultured on gels or non-gel form of Col-I and non-treated dish with or without transforming growth factor (TGF)-β1. On Col-I gels, some cells kept cell–cell contacts and formed clusters, others maintained single-cell form. In cell–cell contact regions, E-cadherin expression was downregulated, whereas that of N-cadherin was upregulated. Vimentin and integrins α2 and β1 expression were not increased. In TGF-β1-treated A549 cells, cadherin switched from E- to N-cadherin. Their morphology changed to a mesenchymal form and cells scattered with no cluster formation. Vimentin, integrins α2 and β1 expression were upregulated. Thus, we concluded that culture on Col-I fibrous gels induced E- to N-cadherin switching without other EMT-related phenotypes in A549 cells.