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Background Integrin-linked kinase (ILK) is a serine-threonine kinase that regulates interactions between the cell and the extracellular matrix. In many cancers, overexpression of ILK leads to increased cell proliferation, motility, and invasion. We hypothesized that ILK functions as a regulator of viability and migration in thyroid cancer cells. Methods Eleven human thyroid cancer cell lines were screened for ILK protein expression. The cell lines with the greatest expression were treated with either ILK small interfering RNA (siRNA) or a novel ILK inhibitor, T315, and the effects were evaluated via Western blot and migration assay. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assays were performed to assess cell viability. Results siRNA against ILK decreased phosphorylation of downstream effectors Akt and MLC, as well as decreased migration. Treatment with T315 showed a dose-related decrease in both Akt and MLC phosphorylation, as well as decreased migration. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assays showed T315 to have an half maximal inhibitory concentration of less than 1 μM in cell lines with high ILK expression. Conclusion ILK is expressed differentially in thyroid cancer cell lines. Both ILK siRNA and T315 inhibit motility of thyroid cancer cell lines, and T315 is shown to be cytotoxic at low concentrations. Altogether, our study suggests that ILK may represent an important kinase in aggressive thyroid cancers.

Background Calcium-sensing receptor (CaSR) is expressed by parathyroid cells and thyroid C-cells (from which medullary thyroid carcinoma [MTC] is derived). A molecular imaging agent localizing to the CaSR could improve the detection of parathyroids and MTC preoperatively or intraoperatively. We synthesized a novel compound containing a fluorine residue for potential future labeling and demonstrated that the compound inhibited CaSR function in vitro. Methods We synthesized compound M, a derivative of a known calcilytic compound, Calhex-231. Human embryonic kidney cells transfected with green-fluorescent protein-tagged CaSR or control vector were preincubated with compound M before the addition of calcium. Immunoblotting for total mitogen-activated protein kinase (MAPK: ERK1/2), activated MAPK (phosphorylated ERK1/2), and glyceraldehyde 3-phosphate dehydrogenase was performed. Results Synthesis of compound M was confirmed by mass spectrometry. Inhibition of the MAPK signaling pathway by compound M was demonstrated in a dose-dependent manner by a decrease in phosphorylated ERK1/2 with no change in total ERK1/2 levels. Compound M inhibited MAPK signaling slightly better than the parent compound. Conclusion We have developed a novel molecule which demonstrates functional inhibition of CaSR and has a favorable structure for labeling. This compound appears to be appropriate for further development as a molecular imaging tool to enhance the surgical treatment of parathyroid disease and MTC.

Background: Although fine-needle aspiration (FNA) is the most sensitive method for the detection of thyroid carcinoma, it cannot provide a definitive diagnosis of malignancy in 60% of the patients operated on for suspicious lesions. Recently, human telomerase reverse transcriptase (hTERT) has been found to be a diagnostic marker of malignancy. We therefore sought to determine whether hTERT gene expression could serve as an adjunct to FNA in the differential diagnosis of thyroid nodules. Methods: Twenty-four FNA samples from thyroid nodules that were suspected of malignancy were collected. RNA was extracted, and hTERT gene expression was examined by RT-PCR. Cytologic and histologic examinations were also performed. Results: Two of three follicular, three of three Hurthle cell, and eight of eight papillary thyroid carcinomas had corresponding FNA samples that were positive for hTERT. One of two Hurthle cell adenomas was hTERT positive. FNA samples from three follicular adenomas and five hyperplastic nodules were negative for hTERT. Positive and negative predictive values were 93% and 90%, respectively. Conclusions: The detection of hTERT gene expression in thyroid FNA samples holds promise as a diagnostic marker in the distinction of benign from malignant thyroid lesions. Its application could alter the surgical management of these patients. (Surgery 1999;126:1195-9.)

Background. Although fine-needle aspiration (FNA) is 90% sensitive in the detection of papillary carcinoma (PC) of the thyroid, its specificity has been reported as low as 52%. Consequently, patients who have an FNA suspicious for PC may undergo operation for a benign process. The ribonucleoprotein telomerase has been noted to be activated in a wide variety of carcinomas. We examined 30 PCs for telomerase activity to determine whether this would be a useful adjunct to FNA in the diagnosis of lesions suspicious for PC. Methods. Standard telomere repeat amplification protocol assays were performed on fresh frozen tissue samples from 30 PCs, 3 benign nodules, and 10 normal thyroids. Results. Telomerase activity was documented in 20 of 30 (67%) of the PCs, 0 of 3 benign nodules, and 0 of 10 normal thyroids. In all, 11 of the 20 PCs had FNA cytology that was nondiagnostic of PC, and 2 of the benign nodules had FNA that was suspicious for PC. Conclusions. The telomerase assay appears useful in the distinction of benign from malignant thyroid lesions that have FNA suspicious for but not diagnostic of PC. On the basis of these findings, a prospective trial examining telomerase activity in FNAs suspicious for thyroid cancer has been initiated.

The oligosaccharide chains of pituitary glycoprotein hormones such as human thyroid-stimulating hormone (hTSH) have been shown to be important in biosynthesis, subunit association, secretion and bioactivity. However, the exact biological significance of these glycosylation variants (isoforms) remains controversial. The aim of this paper is to investigate the role of hTSH glycosylation variants in signal transduction. Human pituitary standard TSH (2nd International Reference Preparation 80/558; IRP-hTSH) was treated with neuraminidase, fractionated by isoelectric focusing (IEF) and affinity chromatography using the lectins concanavalin A (Con A) and lentil. To determine the in vitro bioactivity of these hTSH isoforms, simultaneous measurement of cAMP formation and inositol phosphates release was applied in two different cell systems (CHO cells stably and Cos-7 cells transiently transfected with hTSHR cDNA). Desialylated TSH variants showed a significantly increased ratio of bioactivity to immunoreactivity for cAMP production in CHO-R cells (B/I ratio desialylated variants: 3.54 +/- 0.005; B/I ratio sialylated variants: 2.84 +/- 0.01 P0.05). Testing the bioactivity of hTSH glycosylation variants isolated by IEF, we found basic variants to be significantly more active than acidic ones in stimulating the cAMP formation in CHO-R cells (B/I ratio basic variants: 9.92 +/- 0.64; neutral variants: 5.98 +/- 0.07; acidic variants: 2.80 +/- 0.12; P0.01). There were no differences in stimulation of IP-release. High-mannose TSH variants (firmly bound to Con A) showed greater potency to stimulate cAMP formation and IP-release in both CHO-R and Cos-7 cells than biantennary TSH variants (weakly bound to Con A). Both core-fucosylated (lentil-bound) and core-unfucosylated (lentil-unbound) TSH variants proved to be strong stimulators of cAMP release in CHO and Cos-7 cells. In CHO-R (Cos-7) cells, 400 microU/ml core-fucosylated TSH stimulated cAMP formation 14(2.6)-fold, core-unfucosylated TSH 7.3(2.3)-fold over control values. In contrast to our findings of cAMP activation by both core-fucosylated and core-unfucosylated TSH variants, release of IPs was stimulated only by, core-fucosylated (lentil-bound) TSH variants and not by TSH variants lacking core-fucose residues (lentil-unbound TSH). This was true for both CHO-R and Cos-7 cells. The lentil-unbound TSH therefore showed an identical differential activation of signal transduction pathways in two different cell systems: strong stimulation of the cAMP-cascade without activation of IPs release (P0.05). In conclusion, we showed for the first time for TSH that the two dominant intracellular signal transduction systems (cAMP formation and IPs release) are activated to different degrees by hTSH glycosylation variants.

The major histocompatibility complex (MHC) class I gene cAMP response element (CRE)-like site, −107 to −100 base pairs, is a critical component of a previously unrecognized silencer, −127 to −90 bp, important for thyrotropin (TSH)/cAMP-mediated repression in thyrocytes. TSH/cAMP induced-silencer activity is associated with the formation of novel complexes with the 38-base pair silencer, whose appearance requires the CRE and involves ubiquitous and thyroid-specific proteins as follows: the CRE-binding protein, a Y-box protein termed thyrotropin receptor (TSHR) suppressor element protein-1 (TSEP-1); thyroid transcription factor-1 (TTF-1); and Pax-8. TTF-1 is an enhancer of class I promoter activity; Pax-8 and TSEP-1 are suppressors. TSH/cAMP decreases TTF-1 complex formation with the silencer, thereby decreasing maximal class I expression; TSH/cAMP enhance TSEP-1 and Pax-8 complex formation in association with their repressive actions. Oligonucleotides that bind TSEP-1, not Pax-8, prevent formation of the TSH/cAMP-induced complexes associated with TSH-induced class I suppression, i.e. TSEP-1 appears to be the dominant repressor factor associated with TSH/cAMP-decreased class I activity and formation of the novel complexes. TSEP-1, TTF-1, and/or Pax-8 are involved in TSH/cAMP-induced negative regulation of the TSH receptor gene in thyrocytes, suppression of MHC class II, and up-regulation of thyroglobulin. TSH/cAMP coordinate regulation of common transcription factors may, therefore, be the basis for self-tolerance and the absence of autoimmunity in the face of TSHR-mediated increases in gene products that are important for thyroid growth and function but are able to act as autoantigens.

3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity and mRNA levels were significantly reduced in FRTL-5 cells transformed with the Kirsten-Moloney sarcoma virus (KiMol); these cells have lost thyrotropin dependence and express high levels of p21ras. FRTL-5 cells, transformed with a temperature-sensitive mutant of the v-K-ras oncogene (Ats cells: 33°C, permissive; 39°C, nonpermissive), showed significant reduction of HMG-CoA reductase expression when exposed to 33°C. In KiMol cells, as well as in Ats cells at 33°C, the transcription driven by cAMP-responsive element was probed by measuring chloramphenicol acetyl transferase (CAT) levels after transfection with a chimeric plasmid containing the reporter gene linked to the rat reductase promoter. Basal CAT activity in KiMol cells transfected with wild-type promoter was lower than in FRTL-5 cells but was increased by forskolin to the levels attained in thyrotropin-stimulated FRTL-5 cells. Forskolin failed to increase CAT activity in KiMol cells transfected with the plasmid harboring a reductase promoter in which the cAMP-responsive element octamer was mutated to a nonpalindromic sequence. The effect of v-K-ras could be mimicked in FRTL-5 cells by tetradecanoyl phorbol acetate and reverted in KiMol and Ats cells, expressing active Ras protein, by increasing intracellular cAMP and/or by protein kinase C inhibition. The data are consistent with the contention that v-K-ras, through protein kinase C and depletion of intracellular cAMP, is inhibitory for the protein kinase A pathway. This is the first demonstration that active v-K-ras down-regulates HMG-CoA reductase expression.

The present study, utilizing the hormone-responsive rat thyroid cell line FRTL-5, presents evidence establishing the regulatory role of thyrotropin in modulating mRNA for beta-galactoside alpha 2,6-sialytransferase, the enzyme responsible for the expression of alpha 2,6-linked sialic acid. Both the cell surface membrane and the thyroglobulin secreted by cells grown in the presence of this hormone exhibit a marked decrease in the level of alpha 2,6-bound sialic acid with little or no change in the number of alpha 2,3-sialic acid residues. An additional, and unexpected, sequel is the finding of a coordinated decrease in all of the core monosaccharide constituents of the secreted thyroglobulin. Both of the above phenomenological changes appear to be at some variance with previously described systems wherein thyrotropin was deemed to increase glycosylation. It is anticipated that further resolution of this apparent difference may provide a clearer definition for the role of the carbohydrate moiety in affecting the biological function of thyroglobulin.

Thyrotropin (TSH) receptor mRNA levels in rat FRTL-5 thyroid cells are decreased by treatment with the calcium ionophores, A23187 or ionomycin, as well as with TSH, cholera toxin, forskolin, and 8-bromo-cAMP. Down regulation is, in each case, associated with a decrease in [125I]TSH binding and a decreased ability of TSH to increase cAMP levels. The ionophore does not alter cAMP levels and ethylene glycol-bis-(beta-aminoethyl ether) N, N'-tetraacetic acid (EGTA) in the medium prevents down regulation of TSH receptor mRNA levels by the ionophore, but not by TSH; the EGTA action is reversed by the simultaneous addition of Ca++. Whereas down regulation by TSH and its cAMP signal requires the presence of insulin and/or serum in the medium; down regulation by a calcium ionophore is still evident in their absence. Down regulation of TSH receptor mRNA levels and receptor desensitization by TSH/cAMP or an ionophore is lost in cells transfected with a full length TSH receptor cDNA devoid of regulatory elements, but able to reconstitute TSH receptor signal generation.

The present report shows that thyrotropin (TSH) regulates all three steps involved in prostaglandin synthesis in FRTL-5 rat thyroid cells, i.e. arachidonic acid release from membrane phospholipids, cyclooxygenase (prostaglandin H synthase) action, and individual prostaglandin formation; however, its action at specific steps may require the presence of, or can be duplicated by, insulin, insulin-like growth factor-I (IGF-I), and/or a serum factor. Thus, TSH releases free arachidonic acid from rat FRTL-5 thyroid cells whose phospholipid fraction is radiolabeled with [3H]arachidonic acid; this action involves a pertussis toxin-sensitive G protein, is not cAMP mediated, and does not require insulin or 5% serum. To quantitate TSH effects on cyclooxygenase activity and on individual prostaglandin formation, a homogenate system and a rapid reversed-phase high pressure liquid chromatography procedure have been developed to measure cyclooxygenase metabolites. TSH increased cyclooxygenase activity in homogenates only if the cells were also exposed to insulin, IGF-I, and/or 5% calf serum; TSH alone had no apparent effect on the activity. Maximal activation, 4-fold over basal/micrograms of DNA, took 36 h to achieve and reflected, at least in part, an increase in cyclooxygenase gene expression. Like cyclooxygenase activity, induction of prostaglandin E2 production required 2 or more factors, i.e. TSH plus insulin/IGF-I or TSH plus insulin/IGF-I plus serum. Increased production of prostaglandin D2, could, however, be detected if cells were treated with TSH alone and the TSH activity could be duplicated by insulin, IGF-I, or calf serum alone.

In order to resolve questions concerning the in situ structure of the thyrotropin (TSH) receptor, [35S]methionine-labeled thyroid cell preparations were detergent solubilized and proteins exhibiting TSH-dependent binding to TSH-Sepharose were identified. Two such proteins, 43 and 70 kd, are identified in this report as gamma-actin and a member of the heat shock 70 protein family, respectively, based on the microsequence of two peptides from each. Identification of the former was confirmed by Western blotting and immunostaining using anti-actin, the latter by its ability to bind [32P]ATP, a characteristic feature of this family of proteins. The results suggest that TSH-cross linking reports defining TSH receptor subunits should be viewed with caution in the absence of comparative sequence data; consideration must, however, be given to the existence of receptor associated proteins.

Recombinant human interleukin 1 alpha (rhIL-1 alpha) stimulates prostaglandin E2 and bone resorption in cultured forearm bones of fetal mouse in a dose-dependent manner: the minimal rhIL-1 alpha to elicit a significant bone resorption was 1.6 ng/ml (89 pM). The half maximal concentrations to elicit bone resorption and thymocyte proliferation were 3.3 ng/ml (183 pM) and 0.31 ng/ml (17 pM), respectively. The bone resorbing activity induced by IL-1 was partially inhibited by indomethacin and hydrocortisone, and completely inhibited by anti-IL 1-antibody. There was a good correlation between PGE2 production and bone resorption induced by IL-1 alpha. These results suggest that rhIL-1 alpha stimulates bone resorption at approximately 10 times the concentrations necessary for thymocyte proliferation and that PGE2 produced in the bone is at least in part involved in osteoclastic bone resorption.