Control of the proliferation and differentiation of GEJ under platelet aggregating factor treatment

Abstract

The growth and the differentiation of thyroid cells is known to be under the control of both cyclic AMP dependent and independent pathways. Taking into account these data, we studied the regulation of proliferation and the expression of differentiation using the human thyroid hybrid cells we cloned (Karsenty et al. 1985). This study was conducted using platelet aggregating factor\x=req-\ acether (PAF-acether) (Roubin et al. 1983), a phospholipid mediator which has been shown to stimulate the phosphoinositol cycle of porcine thyroid cells without promoting cAMP accumulation (Haye et al. 1984). Materials and Methods ReagentsHighly purified human TSH (hTSH) was supplied by the National Pituitary Agency (Baltimore, MO) and iodine labelled using the lactoperoxidase method.PAF-acether was a gift of Dr J. M. Mencia-Huerta. Bovine serum albumin (BSA) and insulin were purchased from Sigma (St. Louis, MO). GEJ cell culture and proliferation GEJ cells were maintained in complete culture medium: RPMI 1640 (Gibco, Paisley, Scotland), penicillin 100 U/ml, streptomycin 100 \g=m\g/ml and 10% heat inactivated foetal calf serum (FCS) in an atmosphere of 10% C02 in air. For proliferation, cells were seeded at 5 x 103 cells (in 0.2 ml complete medium with 5% FCS) in a 96 well microtest II Falcon tissue culture plate and PAF-acether added at the specified concentrations. Cells were counted at the required time with a hemocytometer. Binding assay of [125I]TSH to GEJ cells was per¬ formed as previously reported (Roubin et al. 1983). ResultsFive thousand GEJ cells were cultured with -7 M to 10-12 M PAF-acether in complete culture me¬ dium containing 5% FCS. On days 3, 5 and 7 viable cells were counted with a haemocytometer.As shown in Table 1, on day -t-3 of culture, an increase of approximately 60% in cell numbers was found with doses of PAF-acether varying from 10-9 to 10-11 M. This increase promiferative response of the GEJ cells induced by the PAFacether was still detected on day + 5 while it disappears on day + 7 of culture.In a second series of experiments, we investi¬ gated if PAF-acether, apart from its proliferative action, could influence the number of binding sites for TSH on GEJ cells. From preliminary experiments (data not shown), we determined that incubation of GEJ cells during 1 h with 10"X2 M PAF-acether increases of approximately 50 to 60% the numbers of binding sites for TSH, this effect being detectable but less intense after 30 min of incubation. Moreover, we demonstrated that similar amounts of BSA have no effect on the number of TSH-R on GEJ cells (Table 2). We also investigated if these PAF-acether induced binding sites were specific for TSH; for that purpose, GEJ

Platelet-activating factor and human thyroid cancer

“…Only a few results are available concerning the effect of PAF on thyroid cell functions. Thus, PAF is reported to reduce cAMP production from porcine thyroid cells in response to thyreostimulin (31), and to increase the growth of GEJ cells (human thyroid hybrid cells) and their thyreostimulin receptor expression (32). Several molecular abnormalities are found during the progression from normal thyroid tissue to thyroid cancer (1).…”

Metabolic fate of platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) and lyso-PAF (1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine) in FRTL5 cells

“…PAF evoked a moderate but significant inhibition of cAMP accumulation, promoted by acute stimulation by TSH on porcine thyroid cells, and affected phospholipid metabolism and protein iodination of these cells (12). It has been reported that PAF significantly augments GEJ cell numbers (human thyroid hybrid cells) and the number of binding sites for [ 125 I]-labeled TSH while it induces high affinity TSH-binding sites on these cells (13).…”