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 1 alpha (Il-1 alpha) and tumour
necrosis factor-alpha (
TNF-alpha).
Cytokine mRNA levels were monitored by semi-quantitative
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 < or = 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-1 alpha (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-alpha (10 U/ml) yielded divergent results. No significant increase of
GM-CSF mRNA or
protein expression was found in thyrocytes although
TNF-alpha receptor expression in these cells is well documented. Stimulation with
TNF-alpha 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-1 alpha, but only fibroblasts respond to
TNF-alpha with a significant increase in
GM-CSF.
Anaplastic thyroid carcinomas are potential
GM-CSF producers.