The ectopic expression of Snail in MDBK cells does not induce epithelial-mesenchymal transition.

Epithelial-mesenchymal transition (EMT), a key process in the tumor metastatic cascade, is characterized by the loss of cell-cell junctions and cell polarity, as well as by the acquisition of migratory and invasive properties. However, the precise molecular events that initiate this complex EMT process are poorly understood. Snail expression induces EMT in Madin-Darby canine kidney (MDCK) cells and the human epidermoid carcinoma cell line, A431. Snail is a zinc finger transcription factor and triggers EMT by suppressing E-cadherin expression. In the present study, to broaden our knowledge of Snail­induced EMT, we generated stable Snail transfectants using Madin-Darby bovine kidney (MDBK) cells. Contrary to the MDCK or A431 cells examined in our previous studies, the MDBK cells transfected with the Snail construct maintained an epithelial morphology and showed no sign of reduced cell-cell adhesiveness compared to the control cells. Consistent with these observations, the downregulation of epithelial marker proteins, e.g. E-cadherin and desmoglein, and the upregulation of mesenchymal marker proteins, e.g., N-cadherin and fibronectin, were not detected. Furthermore, the E-cadherin promoter was not methylated. Therefore, in the MDBK cells, the ectopic expression of Snail failed to induce EMT. As previously demonstrated, in MDCK cells, Snail expression is accompanied by the increased expression of other EMT-inducing transcription factors, e.g., Slug and zinc finger E-box-binding homeobox 1 (ZEB1). However, the MDBK cells transfected with the Snail construct did not exhibit an increased expression of these factors. Thus, it is possible that the failure to upregulate other EMT-related transcription factors may explain the lack of Snail-mediated induction of EMT in MDBK cells.

Desmoglein 3 and keratin 10 expressions are reduced by chronic exposure to cigarette smoke in human keratinised oral mucosa explants.

OBJECTIVE: Oral mucosa is a physiological barrier against several exogenous stimuli, among which cigarette smoke represents a source of reactive oxidizing compounds. No morphological evidences exist on the smoke effects induced in the human oral epithelium. In this study we performed a preliminary light and transmission electron microscopy morphological evaluation focussing in particular on keratinocyte intercellular adhesion and terminal differentiation in chronic smokers. DESIGN: Human biopsies were obtained from healthy young chronic smoker women (n=5) compared with a parallel group of non-smoker healthy volunteers (n=5), as the smoking habit among women is ever more spreading. Samples were processed for light and transmission electron microscopy. On paraffin sections Masson's and Dane and Herman's histochemical staining were performed. Biomarker expressions of intercellular adhesion (desmoglein 3, Dsg3), terminal differentiation (keratin 10, K10 and keratin 14, K14), and basal membrane preservation (laminin) were investigated by immunofluorescence. RESULTS: In both groups the epithelial structural integrity, homeostasis, and the basal membrane were comparable. Dsg3 and K10 expressions were affected in smokers with the former significantly reduced (p<0.05). Ultrastructural analysis showed hypertrophic keratinocytes in the upper spinous layer and morphologically preserved desmosomes throughout the epithelial compartment. CONCLUSIONS: The reduction of Dsg3 and K10 expressions indicates that the overall process of keratinocyte terminal differentiation was altered. These preliminary results strongly suggest that Dsg3 and K10 can represent valuable immunomarkers to evaluate the tissue attempt to respond to an exogenous stress such as chronic cigarette smoke, but further samples need to be analysed.