Abstract: Nonantigen specific adhesion systems lymphocyte function-associated antigen 1/intercellular adhesion molecule (LFA-1/ICAM-1) and cluster designation 2/lymphocyte function-associated antigen 3 (CD2/LFA-3) are considered a crucial step in immune-mediated cell-cell adhesion reactions. In particular, the LFA-1/ICAM-1 system is deeply involved in major histocompatibility system (MHC)-restricted and non-MHC-restricted cellular cytotoxicity of effector cells against cancer tissues. We have investigated in human thyroid carcinoma cell lines the role of the protein kinase C (PKC) pathway on ICAM-1 expression. Incubation with tissue plasminogen activator (TPA), an agonist of PKC, of two papillary (NPA and TPC-1) and one anaplastic (ARO) carcinoma cell lines induced an ICAM-1 upregulation of both protein and mRNA production. This phenomenon was dependent on RNA and protein synthesis and was inhibited by PKC antagonists such as staurosporine and H-7. A parallel increase in the soluble form of ICAM-1 followed the upregulation of cellular ICAM-1 levels induced by TPA. In conclusion, the PKC pathway is involved in the regulation of ICAM-1 expression in human thyroid carcinoma cell lines. Further studies are necessary to clarify the effects of the PKC pathway on the diffusion of thyroid tumors.
Abstract: The expression of intercellular adhesion molecule-1 (ICAM-1) in tumoral tissues may promote their interaction with the immune system and cytotoxic effect on tumoral cells. This observation led to the investigation of ICAM-1 expression and modulation in different tumoral cell systems in vitro. Recently, retinoic acid-responsive elements have been found in the 5'-regulatory region of the human ICAM-1 gene. In the present study, we investigated, by flow cytometry, the effect of retinoic acid on the surface expression of ICAM-1 in human thyroid carcinoma cell lines. Two papillary (NPA and TPC-1), one follicular (WRO), one anaplastic (ARO) and one immortalized fetal (TAD-2) cell line have been studied. All of them produced constitutively ICAM-1; its surface expression and specific messenger ribonucleic acid (mRNA) levels were increased significantly by retinoic acid in all except the WRO cell line. ICAM-1 hyperexpression by retinoic acid was time dependent, reversible, and dependent on mRNA and protein synthesis. Furthermore, cytokines, such as interferon-gamma and tumor necrosis factor-alpha, both individually and, to a greater extent, in combination with retinoic acid, increased ICAM-1 surface expression and its mRNA levels. In conclusion, retinoic acid is able to induce ICAM-1 up-regulation via mRNA accumulation in human thyroid carcinoma cell lines.
Abstract: The expression of the beta 1 family of integrins was studied in normal thyroid tissue cultures and monolayer cell cultures. The expression of the various subunits was measured by flow cytofluorometry with specific monoclonal antibodies and by Northern analysis. In monolayer cell cultures but not in tissue cultures, the expression of the alpha 3 subunit on the cell membrane progressively increased soon after plating, reaching a 30-fold higher intensity. The alpha 2 subunit, not detectable in native follicular cells, was expressed de novo and reached a remarkable high level. Up-regulation of alpha 2 and alpha 3 in monolayer cell cultures was serum-independent and preceded the expression of proliferating cell nuclear antigen, [3H]thymidine incorporation, and cell replication. Northern analysis demonstrated an increased level of beta 1 integrin mRNA. The increase of alpha 2 and alpha 3 was readily reversible since the expression of these molecules returned to a lower level when cultures reached a high cell density. Down-regulation did not occur until cell cultures were confluent. When cells from high cell density and low integrin expression were harvested and sparsely seeded in culture, up-regulation of integrins was observed again, while rapid reaggregation of isolated cells inhibited this phenomenon. Altogether these data suggest that cell-to-cell contact may regulate the expression of beta 1 integrins in thyroid primary cultures.
Abstract: The expression and cell-membrane distribution of the beta 1 family of integrins (very-late-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 subunits 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 a remarkably 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.
Abstract: To assess the expression of the very late antigens family of the integrin superfamily in normal and diseased thyroid glands, tissue specimens were digested to a single cell suspension and analyzed by flow cytometry with antibodies against the common beta 1 chain and the six alpha chains known to be associated to beta 1. In multinodular goiters, two cell populations were recognized. The thyroglobulin containing follicular cell population, represented the majority of cells; a minor population was composed of leukocytes. In normal glands, more than 97% of follicular cells expressed the beta 1 chain, associated with high levels of alpha 3 and very low levels of alpha 1, alpha 5, and alpha 6. The remaining cells (< 3%) expressed the beta 1 chain with a 10-fold higher intensity, associated with relatively high levels of alpha 1, alpha 5, and alpha 6, in addition to alpha 3. This small subset was much more represented in multinodular goiters, where it ranged from 10-60% of the total follicular cell population. Immunofluorescence on tissue sections showed that very late antigens were mostly located on the basal cell membrane and that in multinodular goiters cells expressing the alpha 1, alpha 5, and alpha 6 chains occurred in clusters.
