Laminin receptors in differentiated thyroid tumors: Restricted expression of the 67-kilodalton laminin receptor in follicular carcinoma cells

The expression of integrin laminin receptors was investigated in normal thy roid primary cultures; immortalized normal thyroid cells (TAD-2); papillary (NPA), follicular (WRO), and anaplastic (ARO) thyroid tumor cell lines; se ven thyroid tumors (four papillary and three follicular carcinomas); and no rmal thyroid glands. The expression of alpha(1)beta(1), alpha(2)beta(1), al pha(3)beta(1), alpha(6)beta(1), and alpha(6)beta(4) was found in all tumor specimens and in tumor cell lines, whereas normal thyroid cells and TAD-2 c ells lacked the expression of alpha(6)beta(4). Despite the presence of seve ral integrin laminin receptors, adhesion of TAD-2, NPA, and ARO cells to im mobilized laminin-l was poor, whereas WRO cells and follicular carcinoma-de rived cells displayed a strong adhesion, indeed, WRO and follicular carcino ma-derived cells showed expression of a nonintegrin laminin receptor, the 6 7-kDa high affinity laminin receptor (67LR). TAD-2, NPA, and ARO cells as w ell as nodular goiter, toxic adenoma, follicular adenoma, and papillary car cinoma-derived cells did not express the 67LR. Adhesion of WRO and follicul ar carcinoma-derived cells to laminin-l was specifically inhibited by a rec ombinant polypeptide containing laminin-binding domains of 67LR, demonstrat ing that this receptor confers to follicular carcinoma cells attachment cap acity to laminin. Moreover, tissue specimens from follicular carcinomas exp ressed the 67LR, whereas follicular adenomas and normal thyroid tissues wer e negative. in thyroid tumors, integrin receptors, although abundant, parti cipate weakly in adhesion to laminin. The expression in follicular carcinom a cells of a functional, high affinity 67LR together with nonfunctional int egrin LM receptors could be responsible for the tendency of follicular carc inoma cells to metastasize by mediating stable contacts with basal membrane s.