Serum withdrawal-induced apoptosis in thyroid cells is caused by loss of fibronectin-integrin interaction

In some cell types, including a fetal thyroid cell line, denial of adhesion to extracellular matrix induces a type of apoptosis called anoikis. Serum withdrawal in dog and transformed rat thyroid cells also induces programmed cell death. Because serum can stimulate cells to produce some components o f the extracellular matrix, it was of interest to determine the role of the matrix in the apoptosis induced by serum withdrawal in normal human thyroi d cells in primary culture. The present report demonstrates that thyroid ce lls selectively produce and deposit insoluble fibronectin (FN) only when st imulated by serum. Adhesion in the presence of serum is dependent upon inte grin-FN interaction. Serum withdrawal determines a degradation of the insol uble FN deposited and a detachment of the cells from the plates. In these c onditions, cells undergo anoikis, demonstrated by DNA fragmentation and ann exin V staining. Apoptosis was prevented by exogenous FN immobilized onto t he plates. These results indicate that serum withdrawal induces apoptosis i n human thyroid cells, determining FN degradation and loss of cell-matrix a dhesion.