Differential regulation of granulocyte-macrophage colony-stimulating factor mRNA and protein expression in human thyrocytes and thyroid-derived fibroblasts by interleukin-1α and tumour necrosis factor-α

Abstract

Abstract In this study, we provide the first report on the production of granulocyte-macrophage colony-stimulating factor (GM-CSF) by human thyroid epithelial cells. Primary cultures of highly purified thyrocytes and thyroid-derived fibroblasts (n=3) and three thyroid anaplastic and one largely papillary carcinoma cell lines were exposed to different potent GM-CSF stimulators, employing interleukin 1α (Il-1α) and tumour necrosis factor-α (TNF-α). Cytokine mRNA levels were monitored by semiquantitative reverse transcriptase-PCR including an internal heterologous competitor fragment after 3, 6 and 18 h of culture. Culture supernatants were assayed for GM-CSF using a highly sensitive ELISA (detection limit ≤ 0·5 pg/ml) after 24 h. Basal 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 spontaneously secreted by fibroblasts (means ± s.e.m.; 43 ± 15 pg/ml), SW 1736 (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 with Il-1α (10 U/ml) resulted in a marked increase of GM-CSF mRNA within 3 h and an increase or induction of protein expression in thyrocyte (2350 ± 214 pg/ml), fibroblast (5242 ± 1400 pg/ml), SW 1736 (20016 ± 280 pg/ml) and C 643 cultures (1285 ± 79 pg/ml). Stimulation with TNF-α (10 U/ml) yielded divergent results. No significant increase of GM-CSF mRNA or protein expression was found in thyrocytes although TNF-α receptor expression in these cells is well documented. Stimulation with TNF-α resulted in an increased GM-CSF production 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 suggest that both thyrocytes and fibroblasts synthesize GM-CSF in response to Il-1α, but only fibroblasts respond to TNF-α with a significant increase in GM-CSF. Anaplastic thyroid carcinomas are potential GM-CSF producers. Journal of Endocrinology (1996) 151, 277–285