Differentiation and growth in monolayer cultures of human oral normal and malignant keratinocytes and their relationship with adhesion molecules expression.

摘要

Adhesion molecules have been shown to provide both intercellular attachment and transmit extracellular signaling in most cell types. The primary objective of the work presented in this thesis was to determine the relationship between some adhesion molecules, growth, and differentiation in monolayer culture models of normal human oral keratinocytes.; In the first chapter, the characterization of normal human oral keratinocytes and two cell lines (SCC 15 and SCC25) was obtained. The SCC cell lines grow faster than normal cells, and this suggested that expression and localization of differentiation markers, adhesion molecules and ratio between saturated and unsaturated fatty acids would be different. The results showed that the main variations between cultures of normal oral epithelium and SCC cell lines are likely related to the stage of terminal differentiation demonstrated by the normal cell cultures, rather than the growth capacity.; In the second chapter, a known adhesion molecule, beta-catenin, with a demonstrated signaling function, was examined to determine its signaling role in cultures of normal and malignant (SCC 15 and SCC25 cell lines) keratinocytes. Beta-catenin localized in the cytoplasm and nucleus in SCC25 cell lines, not SCC 15 or normal cells; and only few invading islands of human oral cancers showed nuclear localization of beta-catenin. SCC25 cells proliferated faster than normal and SCC 15 cell lines over a period of 6 days (p 0.0001). These results suggested that beta-catenin might activate transcription of target genes in some cancer cells, not in normal cells, in the growth conditions tested.; The third chapter tested the hypothesis that increased expression of E-cadherin, an intercellular adhesion protein, would determine increased intercellular adhesion, and induce differentiation in cultures of normal keratinocytes. In the experimental assays, Ad5-Ecad transduction decreased intercellular spaces and determined a moderate increase of involucrin; however, it did not modify cell morphology, intercellular bridges formation and stratification. Thus, the increased intercellular adhesion mediated by the excess of E-cadherin may be responsible for the signaling leading to the moderated increase in involucrin synthesis. In absence of Ca++, this signal may not be functional.