DIFFERENTIAL REGULATION OF GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR MESSENGER-RNA AND PROTEIN EXPRESSION IN HUMAN THYROCYTES AND THYROID-DERIVED FIBROBLASTS BY INTERLEUKIN-1-ALPHA AND TUMOR-NECROSIS-FACTOR-ALPHA

In this study, we provide the first report on the production of granul ocyte-macrophage colony-stimulating factor (GM-CSF) by human thyroid e pithelial cells, Primary cultures of highly purified thyrocytes and th yroid-derived fibroblasts (n=3) and three thyroid anaplastic and one l argely papillary carcinoma cell lines were exposed to different potent GM-CSF stimulators, employing interleukin 1 alpha (IL-1 alpha) and tu mour necrosis factor-alpha (TNF-alpha). Cytokine mRNA levels were moni tored by semiquantitative reverse transcriptase-PCR including an inter nal heterologous competitor fragment after 3, 6 and 18 h of culture. C ulture supernatants were assayed for GM-CSF using a highly sensitive E LISA (detection limit less than or equal to 0.5 pg/ml) after 24 h. Bas al GM-CSF mRNA expression was higher in fibroblasts and SW 1736 cells compared with thyrocytes, C 634, 8505 C and HTh 74 cells. GM-CSF was s pontaneously secreted by fibroblasts (means +/- S.E.M.; 43 +/- 15 pg/m l), SW 17.36 (59 +/- 4 pg/ml), HTh 74 (34 +/- 4 pg/ml) and C 643 cells (12 +/- 1 pg/ml) but not by thyrocytes and 8505 C cells. Treatment wi th IL-1 alpha (10 U/ml) resulted in a marked increase of GM-CSF mRNA w ithin 3 h and an increase or induction of protein expression in thyroc yte (2350 +/- 214 pg/ml), fibroblast (5242 +/- 1400 pg/ml), SW 1736 (2 0016 +/- 280 pg/ml) and C 643 cultures (1285 +/- 79 pg/ml). Stimulatio n with TNF-alpha (10 U/ml) yielded divergent results. No significant i ncrease of GM-CSF mRNA or protein expression was found in thyrocytes a lthough TNF-alpha receptor expression in these cells is well documente d. Stimulation with TNF-alpha resulted in an increased GM-CSF producti on in fibroblasts (361 +/- 14 pg/ml), HTh 74 (148 +/- 51 pg/ml) and SW 1736 cultures (235 +/- 43 pg/ml). TSH (10 mU/ml) did not stimulate GM -CSF secretion in thyrocytes and HTh 74 cells, both expressing the TSH receptor. Phorbol 12-myristate 13-acetate (10 ng/ml) enhanced GM-CSF mRNA and protein levels in all cell types investigated.Our data sugges t that both thyrocytes and fibroblasts synthesize GM-CSF in response t o IL-1 alpha, but only fibroblasts respond to TNF-alpha with a signifi cant increase in GM-CSF. Anaplastic thyroid carcinomas are potential G M-CSF producers.