COMPARISON OF INTEGRIN EXPRESSION AND TERMINAL DIFFERENTIATION CAPACITY IN CELL-LINES DERIVED FROM ORAL SQUAMOUS-CELL CARCINOMAS

Receptors of the integrin family regulate adhesion and terminal differ entiation of keratinocytes. In order to investigate the significance o f changes in integrin expression associated with malignant transformat ion we have examined normal human oral keratinocytes and seven oral sq uamous cell carcinoma (SCC) lines. Cell surface levels of the alpha2, alpha3, alpha5, alpha6, alpha(v), beta1 and beta4 integrin subunits we re determined by flow cytometry and the distribution of the beta1 subu nit was examined by immunohistochemistry. In normal keratinocytes and one SCC line the beta1 subunit was most abundant in the basal cell lay er, but in other lines anti-beta1 antibodies stained basal and supraba sal layers uniformly. All lines had reduced surface levels of at least one integrin subunit and in some cell lines distinct subpopulations c ould be distinguished on the basis of differences in integrin expressi on. Reduced integrin expression was not, however, generally reflected in reduced adhesion to laminin, fibronectin, type IV collagen or vitro nectin in three cell lines examined. Those cell lines with the lowest capacity for terminal differentiation, as measured by involucrin expre ssion, had the lowest levels of the alpha6 and beta4 subunits or were completely lacking alpha(v). Oral SCC show considerable variation in i ntegrin expression, but focal or extensive loss of the alpha6 and beta 4 subunits is a common feature of poorly differentiated tumours. The c ell lines we have examined therefore provide a relevant experimental m odel with which to explore the relationship between aberrant integrin expression and impaired terminal differentiation capacity.