Desmoglein-3/γ-catenin and E-cadherin/-catenin differential expression in oral leukoplakia and squamous cell carcinoma

The purpose of this study was to investigate gene/protein expression alterations of intercellular connections' components in oral leukoplakia (OLs) and squamous-cell carcinoma (OSCCs). Expression of desmogleins-2,3 (Dsg2/Dsg3), E-cadherin, and their cytoplasmic ligand, beta/gamma-catenins were quantitatively assessed in HSC-3 cells growing as monolayer cultures (ML)/multicellular aggregates (MCAs), using RT-PCR/Western blot, whereas their localization was detected by immunofluorescence. Furthermore, their expression was semi-quantitatively investigated in tissues from 25 OLs/25 OSCCs, using automated immunohistochemistry. The steady-state levels of Dsg3 RNA transcripts increased as HSC-3 cells enter their exponential phase of growth, before a dramatic decrease to be observed as cells reached their plateau phase especially in MCAs. Upon the same period of time, Dsg2 levels have been increased. The expression of gamma-catenin but not that of beta-catenin was increased after 48 h in both MLs and MCAs. In clinical samples, Dsg3, I center dot-cadherin, beta/gamma-catenin down-regulation was observed to be associated with the grade of OLs-dysplasia and OSCCs. Importantly, a membrane-to-cytoplasmic switch of expression and strong perinuclear aggregation of Dsg3/gamma-catenin was seen in both HSC-3 cells and OLs/OSCCs. The altered expression of Dsg3/gamma-catenin and E-cadherin/beta-catenin, in vitro and in ODs/OSCC imply their involvement in growth regulation and phenotype of dysplastic/malignant oral epithelial cells, contributing to the better understanding of epithelial dysplasia and OSCCs. The observed alterations of their expression suggest a role of Dsg3 and gamma-catenin (additionally to E-cadherin/beta-catenin) as biomarkers of malignant transformation risk of oral dysplasia and the biological behavior (aggressiveness) of oral cancer, respectively.