Loss of Polarity and De-novo Expression of the Beta(1) Family of Integrins In Thyroid-tumors

The expression and cell-membrane distribution of the beta(1) family of integrins (very-lake-activation antigens, VLA) were investigated in benign and malignant human thyroid tumors. We compared tissue samples of normal glands, nodular goiters, adenomas and carcinomas. We also examined 3 thyroid-carcinoma cell lines cultured in vitro. The expression of sub-units of the beta(1) family of integrins was assessed by flow cytometry and specific antibodies in dispersed single-cell suspensions and by immunofluorescence on frozen tissue sections. In contrast to the heterogeneity of the expression of beta(1) integrins observed in other tumors, thyroid neoplastic lesions showed an remarkable constant VLA profile. In all tumors, benign as well as malignant, and in carcinoma cell lines, all sub-units of beta(1) integrins were expressed at high levels. While sub-units alpha(1), alpha(3), alpha(5), alpha(6) and occasionally alpha(2) were also present in a cell sub-set of normal glands and nodular goiters, expression of alpha(4) was restricted to neoplastic lesions; this integrin can be therefore considered an antigen associated with thyroid tumors. It has been reported that in normal glands and in nodular goiters, the expression of beta(1), integrins is restricted to the basal-cell membrane. Immunofluorescence on tissue sections showed instead that, in adenomas and carcinomas, the polarized distribution of these integrins on the cell membrane is lost.