Two G protein oncogenes in human endocrine tumors.

Somatic mutations in a subset of growth hormone (GH)-secreting pituitary tumors convert the gene for the alpha polypeptide chain (alpha s) of Gs into a putative oncogene, termed gsp. These mutations, which activate alpha s by inhibiting its guanosine triphosphatase (GTPase) activity, are found in codons for either of two amino acids, each of which is completely conserved in all known G protein alpha chains. The likelihood that similar mutations would activate other G proteins prompted a survey of human tumors for mutations that replace either of these two amino acids in other G protein alpha chain genes. The first gene so far tested, which encodes the alpha chain of Gi2, showed mutations that replaced arginine-179 with either cysteine or histidine in 3 of 11 tumors of the adrenal cortex and 3 of 10 endocrine tumors of the ovary. The mutant alpha i2 gene is a putative oncogene, referred to as gip2. In addition, gsp mutations were found in 18 of 42 GH-secreting pituitary tumors and in an autonomously functioning thyroid adenoma. These findings suggest that human tumors may harbor oncogenic mutations in various G protein alpha chain genes.

Laparoscopic bilateral adrenalectomy: results for 30 consecutive cases.

BACKGROUND: Most patients requiring bilateral adrenalectomy have adrenocorticotropin hormone (ACTH)-dependent Cushing's syndrome. Some of these patients are severely debilitated from the chronic effects of cortisol overproduction. This study aimed to analyze the indications, safety, efficacy, and outcomes for laparoscopic bilateral adrenalectomy from the authors' experience. METHODS: A retrospective review was conducted at a university tertiary referral center. Between March 1996 and August 2006, 30 consecutive patients underwent simultaneous laparoscopic bilateral adrenalectomy. The patient records were analyzed to obtain patient demographics, disease etiology, surgical approach, operating room information, postoperative complications (30 days), hospital length of stay (LOS), and follow-up information. RESULTS: The 30 participants (22 women and 8 men) had a mean age of 44 years. The indications for bilateral adrenalectomy were refractory Cushing's disease (n = 16), occult ectopic ACTH syndrome (n = 9), and bilateral pheochromocytoma (n = 5). A mean of 53 months elapsed between onset of symptoms and adrenalectomy. Laparoscopic bilateral adrenalectomy was completed for all the patients with no intraoperative complications. Four patients (13%) experienced six complications. The mean postoperative LOS was 3.5 days (range, 1-12 days). Seven patients required a preoperative LOS, for a mean of 7.1 days (range, 1-20 days), and a postoperative LOS, for a mean of 5 days (range, 2-12 days). The 23 patients who did not require preoperative hospitalization had a mean postoperative LOS of 3 days (range, 1-7 days). All the patients received postoperative steroid replacement and appropriate follow-up assessment with an endocrinologist. At this writing, the patients with Cushing's syndrome available for follow-up evaluation continue to receive steroid replacement, and all the pheochromocytoma patients have experienced a documented postoperative biochemical cure. CONCLUSIONS: Laparoscopic bilateral adrenalectomy is safe and effective for this high-risk patient population. Although patients should be monitored closely in the postoperative period, most are discharged with glucocorticoid and mineralocorticoid replacement in a short time without complications.

Total gastrectomy and small intestinal cholesterol synthesis in diabetic rats.

Cholesterol synthesis is increased two- to threefold in the small intestine of diabetic rats. We have observed, in three separate experiments, that the characteristic increase in small intestinal cholesterol synthesis (SICS) in diabetic rats was prevented by total gastrectomy. Food intake was increased twofold, and the small intestine hypertrophied in the gastrectomized diabetic animals. In normal animals, total gastrectomy resulted in only a very small increase in intestinal cholesterol synthesis. In hyperphagic lactating animals, total gastrectomy did not prevent the characteristic increase in SICS that is usually observed in this hyperphagic model. These results indicate that the effects of total gastrectomy on preventing an increase in SICS are relatively specific for the diabetic state. The mechanism by which total gastrectomy prevents the increase in intestinal cholesterol synthesis in diabetic animals is unknown. Vagotomy did not prevent the typical increase in intestinal synthesis in diabetic animals. Additionally, selectively removing either the antrum or fundus of the stomach did not prevent the increase in SICS in diabetic animals, indicating that the inhibition requires the removal of the entire stomach. It can be speculated that the stomach produces a substance that induces the increase in SICS observed in diabetic animals and that total gastrectomy removes this stimulatory substance.

Treatment guidelines for patients with thyroid nodules and well-differentiated thyroid cancer. American Thyroid Association.

A set of minimum clinical guidelines for use by primary care physicians in the evaluation and management of patients with thyroid nodules or thyroid cancer was developed by consensus by an 11-member Standards of Care Committee (the authors of the article) of the American Thyroid Association, New York, NY. The participants were selected by the committee chairman and by the president of the American Thyroid Association based on their clinical experience. The committee members represented different geographic areas within the United States, to reflect different practice patterns. The guidelines were developed based on the expert opinion of the committee participants, as well as on previously published information. Each committee participant was initially assigned to write a section of the document and to submit it to the committee chairman, who revised and assembled the sections into a complete draft document, which was then circulated among all committee members for further revision. Several of the committee members further revised and refined the document, which was then submitted to the entire membership of the American Thyroid Association for written comments and suggestions, many of which were incorporated into a final draft document, which was reviewed and approved by the Executive Council of the American Thyroid Association.

Diagnosis and management of asymptomatic hyperparathyroidism: safety, efficacy, and deficiencies in our knowledge.

Several recent articles question whether patients with asymptomatic hyperparathyroidism and minimal hypercalcemia should be treated by parathyroidectomy. We therefore reviewed our experience in 103 consecutive patients with primary hyperparathyroidism who were treated by parathyroidectomy to determine, first, how many of these patients had asymptomatic or symptomatic hyperparathyroidism, and second, did these patients benefit from parathyroidectomy? We also analyzed the safety of parathyroidectomy in 426 consecutive patients, including 79 who required reoperation for hyperparathyroidism, specifically looking for complications and the outcome of these procedures. Our study documents the following: (1) only 2 of 103 (2%) patients referred for parathyroidectomy had "true" asymptomatic hyperparathyroidism; (2) only symptoms of fatigue, bone pain, and weight loss correlated with the degree of hypercalcemia, whereas muscular weakness, psychiatric symptoms, nocturia, polyuria, recent memory loss, constipation, and nephrolithiasis did not; (3) only 1 of 15 patients who were referred as asymptomatic were truly asymptomatic after more thorough questioning, and all 14 improved following parathyroidectomy; (4) 81% of the patients who were referred with symptoms improved following parathyroidectomy; and (5) permanent complications occurred in only 4 patients. All but 1 had reoperations for persistent or recurrent hyperparathyroidism (3 vocal cord paralyses and 1 hypoparathyroidism requiring autotransplantation of cryopreserved parathyroid tissue). There was 1 death of an 84-year-old woman with hypercalcemic crisis. Thus, most patients with hyperparathyroidism are symptomatic and benefit symptomatically and metabolically from parathyroidectomy, which is a safe operation.

Desensitization of adenylate cyclase in Chinese hamster ovary cells transfected with human thyroid-stimulating hormone receptor.

Desensitization or decreased response to the same (homologous) or other stimuli (heterologous) is a well known process. Homologous desensitization to TSH has been demonstrated in normal thyroid tissue. Chinese hamster ovary cells (CHO) transfected with normal human TSH receptor (hTSHR) DNA, in contrast, have been reported not to desensitize. The purpose of our investigation was to determine whether CHO cells transfected with hTSHR desensitize in response to TSH and postreceptor stimulation. CHO cells were stably transfected with plasmid DNA containing hTSHR; nontransfected CHO cells served as the control. TSH (10 mU/ml), 5'-beta,gamma-imido-triphosphate [Gpp(NH)p; 0.1 mM], sodium fluoride (NaF; 10 mM), forskolin (10 microM), and (Bu)2cAMP (100 microM) were used to determine whether homologous or postreceptor heterologous desensitization of adenylate cyclase activity occurred in CHO-transfected cells. Intracellular cAMP accumulation was determined by RIA. Cells were incubated with TSH (to stimulate TSH receptor), Gpp(NH)p, NaF (to stimulate G-protein), forskolin (to stimulate adenylate cyclase activity), and (Bu)2cAMP (nonmetabolized cAMP analog). A second incubation was carried out with TSH (10 mU/ml). Maximal desensitization to either TSH or postreceptor stimulation was observed at 2 h. When transfected CHO cells were preexposed to TSH (10 mU/ml) for 4 h, even the smallest dose of TSH (0.001 mU/ml) caused desensitization. All substances that increased the intracellular cAMP concentration, such as TSH, Gpp(NH)p, NaF, forskolin, and (Bu)2cAMP, caused desensitization. The decrease in the cAMP response to TSH added in the second incubation was 63% less than the initial response to TSH or to postreceptor stimulation (P = 0.0001). In conclusion, desensitization of hTSHR-transfected CHO cells occurs in response to both receptor and postreceptor stimulation that increase cAMP levels. Because hTSHR transfected CHO cells desensitize, no specific thyroid factor(s) other than increased levels of cAMP is required.

Compensatory thyroid hypertrophy after hemithyroidectomy in rats.

Thyroid enlargement occurs in association with a variety of circumstances characterized by an impaired capacity of the gland to secrete adequate amounts of hormone. To elucidate the factors responsible for such compensatory thyroid growth, particularly the role of TSH, we have observed the response of the serum TSH, T3 and T4 concentrations following hemithyroidectomy in the rat, and have attempted to correlate changes in these functions with changes in the weight and histology of the thyroid remnant. Hemithyroidectomy was performed in male Sprague-Dawley rats weighing 150 to 370 g, sham-operated animals serving as controls. As compared to findings in sham-operated animals, serum T4 concentrations declined promptly after hemithyroidectomy. In Experiment I serum T4 concentrations remained low for about 10 days and then returned to initial values. In Experiment II serum T4 concentrations remained lower than initial T4 values or values found in sham-operated animals until 34 days after hemithyroidectomy. Serum T3 concentrations were not significantly altered after hemithyroidectomy in either group but tended to be lower in the hemithyroidectomized animals. Serum TSH concentrations increased within 3 days after hemithyroidectomy and, for as long as 21 weeks, remained at values higher than those present preoperatively or those seen in sham-operated animals. Thyroid lobe weight increased following removal of the contralateral lobe and this increase was also sustained throughout the duration of the experiments. Biochemical and histological observations indicated that enlargement of the residual lobe was due to hypertrophy rather than hyperplasia.

Thyrotropin receptor-adenylate cyclase system in Hurthle cell neoplasms.

Hurthle cell neoplasms are though to arise from the follicular cells of the thyroid gland, although some studies suggest that they originate from the parafollicular cells. We studied tissue from five patients (three men and two women, aged 33-72 yr) with Hurthle cell neoplasms (four adenomas and one carcinoma) to determine whether Hurthle cell neoplasms have an intact TSH receptor-adenylate cyclase (AC) system and, if so, whether it differs in benign and malignant Hurthle cell and neoplasms. Binding of [125I]bovine (b) TSH and an AC response to TSH occurred in all four Hurthle cell adenomas. In three of these tumors, there was good binding and a relatively good correlation between the concentration of bTSH producing half-maximal inhibition of [125I]bTSH binding (4.8 mU/ml) and the TSH concentration causing half-maximal stimulation of AC (2.2 mU/ml). There was also a 2- to 5-fold increase in AC activity in response to bTSH (300 mU/ml), a value comparable to that which occurs in follicular thyroid neoplasms and differentiated thyroid cancers. In the fourth Hurthle cell adenoma, however, binding was low, the apparent Kd (170 mU/ml) and Km (20 mU/ml) were high, and there was only a 1.4-fold increase in AC activity in response to bTSH (300 mU/ml). In the one metastatic Hurthle cell carcinoma, there was no high affinity TSH binding or AC response to TSH. Thus, Hurthle cell neoplasms are of follicular cell origin, since benign Hurthle cell tumors have an intact TSH receptor-AC system. Malignant Hurthle cell neoplasms, like undifferentiated and medullary thyroid cancer, lack a functional TSH receptor.

Epidermal growth factor enhances proliferation, migration, and invasion of follicular and papillary thyroid cancer in vitro and in vivo.

The prognosis of patients with follicular (FTC) and papillary (PTC) thyroid cancer depends on age and the size and extent of the tumor. Differentiated thyroid cancers bind more epidermal growth factor (EGF) than normal thyroid tissue, but the role of EGF in the proliferation and invasion of thyroid cancer is unknown. We investigated the effects of EGF on growth, migration, and invasion in a follicular thyroid cancer that metastasized to cervical lymph nodes and the lung (FTC 133, primary; FTC 236, lymph node; and FTC 238, lung metastasis) and in a papillary thyroid cancer (PTC-UC3). As measured by the formazan method (dimethylthiazol-diphenyltetrazolium bromide), EGF caused a dose- and time-dependent increase in the growth of FTC 133 and PTC-UC3 by 25%, but its stimulatory effect on growth of the metastatic FTC subclones was smaller (FTC 236, 14%; FTC 238, 8%; P < 0.001). EGF also enhanced the ability of all cell lines to migrate (through 8-microns pore membranes without Matrigel) or invade (membranes with Matrigel). Migration of FTC 133 was enhanced from 86% migrated tumor cells to 95% after 72 h (P < 0.02). Again, stimulation by EGF was lower in FTC 236 and FTC 238. EGF increased migration in PTC-UC3 from 49% to 58%. EGF stimulated invasion of FTC 133 from 17.5% to 24.9%. In the absence of EGF, FTC 238 was the most invasive tumor, but, again, the EGF stimulatory effect was less pronounced than in the primary tumor. EGF stimulated the invasion of PTC-UC3 from 10.9% to 14.3% (P < 0.03). EGF also stimulated the growth of thyroid cancer xenografts in nude mice. Although all FTC cell lines were 100% tumorigenic in nude mice, PTC-UC3 was less tumorigenic. However, after sc inoculation of EGF-pretreated tumor cells, 7 of 10 animals developed tumors (mean size, 2.3 cm3) compared to 2 of 10 animals (mean size, 1.4 cm3) in the control group (P < 0.02). In summary, EGF stimulates the growth and invasion of differentiated thyroid cancer cells in culture and in nude mice. Escape from growth factor control, such as in FTC 236 and FTC 238, may be an important step in the development of metastatic thyroid cancer.

Tamoxifen inhibits growth, migration, and invasion of human follicular and papillary thyroid cancer cells in vitro and in vivo.

Prognosis of differentiated thyroid cancer is best in young women. It has been proposed that sex steroids protect premenopausal women from aggressive thyroid malignancies. Some thyroid tissues have estrogen receptors, and estrogen stimulates human thyroid cells. Tamoxifen is thought to exert its antiproliferative effects mainly by blocking estrogen stimulation. However, recently, mechanisms independent of estrogen interactions were found to be important for the favorable effect. We investigated the effect of tamoxifen on the growth, migration, and invasion in three follicular thyroid cancer cell lines (FTC133, primary; FTC236, lymph node; and FTC238, lung metastasis) from one patient and two papillary lines (PTC-UC1 and PTC-UC3). Growth was measured by dimethylthiazol-diphenyltetrazolium bromide assays, and migration was determined by the ability of cells to penetrate 8-microns pore membranes, which were covered by Matrigel for invasion assays. For in vivo experiments, we used xenografts of FTC133 in nude mice. Tamoxifen (1.5 mumol/L) inhibited the growth of all thyroid cancer cell lines (FTC133, 59%; FTC236, 42%; FTC238, 46%; P < 0.01). This effect was less pronounced in PTC-UC1 (25%) and PTC-UC3 (19%; P < 0.006) cell lines. Tamoxifen also inhibited migration and invasion of FTC more than PTC. Invasion of FTC133 was inhibited by 36% (P < 0.01), FTC236 by 30%, and FTC238 by 32%. Immunohistochemistry showed no estrogen receptors in any cell line. Also, estradiol had no significant effect on the growth, migration, or invasion of FTC or PTC. Tamoxifen treatment inhibited the growth of FTC133 xenografts in nude mice by 52% compared to that in placebo-treated controls (P < 0.002). In conclusion, tamoxifen inhibited the growth, migration, and invasion of differentiated thyroid cancer cells in vitro and in vivo. This was not reversed by estrogen. Tamoxifen acts independently of estrogen interactions and may be useful as an adjuvant treatment for some differentiated human thyroid malignancies.

Somatostatin analog octreotide inhibits the growth of differentiated thyroid cancer cells in vitro, but not in vivo.

Somatostatin and its analogs are antiproliferative in a wide range of normal and neoplastic tissues. In this study we investigated the effect of octreotide (SMS 201-995) on the invasion and growth of three follicular thyroid cancer (FTC) cell lines from one patient in vitro and in vivo. FTC133 was established from the primary tumor, FTC236 from a cervical lymph node metastasis, and FTC238 from a lung metastasis. Invasion was the ability of tumor cells to penetrate 8-microns pore polycarbonate membranes coated with Matrigel. Invasion and proliferation were analyzed using the MTT assay. For in vivo experiments, athymic nude mice were sc inoculated with 500,000 calls of FTC133. The animals were treated twice daily with octreotide sc (100-300 micrograms/kg). RIA studies yielded dose-dependent high plasma levels of octreotide (3.43-6.5 ng/mL). Octreotide had a biphasic effect, enhancing growth at low concentrations (1-10 nmol/mL) and inhibiting it at high concentrations (100 nmol to 1 mumol/mL). Octreotide had also a dose-dependent biphasic effect on the invasion of FTC, inhibiting the invasion of all follicular thyroid cancer lines at high concentrations. However, it affected invasion less than growth. Octreotide (10 nmol/mL) stimulated the invasion of FTC133 by 13%, whereas stimulation was lower in both FTC metastases (FTC236, 6%; FTC238, 7%; P < 0.01). At higher concentrations (100 nmol to 1 mumol/mL), octreotide inhibited invasion of FTC133 by 17% (FTC236, 15%; FTC238, 17%; P < 0.01). During a 3-week treatment period, octreotide had no antiproliferative effect on the growth of FTC133 cells in nude mice. In conclusion, octreotide at low concentrations stimulates and at high concentrations inhibits the growth and invasion of follicular thyroid cancer cells in culture. However, it has no effect on the growth of FTC cells in animal experiments. Thus, the value of octreotide as an antitumoral agent in follicular thyroid cancer must be critically questioned.

Characterization of the thyrotropin receptor-adenylate cyclase system in neoplastic human thyroid tissue.

Experiments were performed to determine whether the TSH receptor-adenylate cyclase (AC) system in benign and malignant thyroid neoplasms differs from the TSH receptor-AC system in normal thyroid tissue removed from the same patients. TSH binding and AC assays were performed using the same in vitro conditions. TSH binding was rapid, reversible, saturable, and hormone specific in particulate fractions from both normal and neoplastic thyroid tissue. A positive correlation existed between the equilibrium constants for [125I]bovine ([125I]bTSH) TSH binding and the concentration of TSH required to activate AC, suggesting that binding sites were coupled to AC in neoplastic thyroid tissue. Mean values for dissociation constants (Kd1 and Kd2), capacity (site 2), as determined by Scatchard analysis, and nonspecific binding (NSB) for the TSH receptors were lower in neoplastic thyroid. Some normal thyroid tissue appeared to lack a high affinity site, and some tumors lacked a low affinity binding site. Hormone specificities (bTSH, human (h) TSH, hLH, hFSH, hGH, hACTH, and glucagon) in normal thyroid and neoplastic tissue were virtually identical. hFSH, hACTH, hGH, and glucagon failed to inhibit [125I]bTSH binding or stimulate AC in either normal or neoplastic thyroid tissue, whereas hLH inhibited [125I]bTSH binding and stimulated AC, but required 10- to 100-fold higher concentrations than hTSH or bTSH. The specific binding and NSB of [125I]bTSH in both normal and neoplastic thyroid tissue was highest at pH 7.0 and lowest at pH 8.3. In contrast to bTSH binding, TSH stimulation of AC was lowest at pH 7.0 in both normal and neoplastic tissues and highest at pH levels of 7.5-8.0. TSH binding and TSH stimulation of AC activity were highest in the absence of NaCl and decreased progressively as the salt concentration was increased in both normal and neoplastic thyroid tissues. Increasing the sucrose concentration and, thus, the osmolarity of the system had a minimal effect on the binding of [125I]bTSH. Preincubation with ammonium sulfate did not significantly influence binding. Basal AC activity and the AC response to TSH were greater in neoplastic thyroid than in normal tissues. These studies demonstrate that changes in salt concentration and pH affect the TSH receptor-cyclase system in a comparable fashion in normal and neoplastic thyroid tissues. The discriminatory properties of the TSH receptor are also maintained in thyroid neoplasms. Thyroid tumors, however, have a higher affinity for TSH and display a greater AC response to TSH than normal thyroid tissue.

Thyrotropin binding and adenylate cyclase activation in normal and neoplastic human thyroid tissue: lack of effect of thyroglobulin.

The effects of bovine TSH (bTSH) and bovine (bTg) and human thyroglobulin (hTg) on the binding of [125I] bTSH and the activation of adenylate cyclase (AC) were studied in both normal and neoplastic human thyroid homogenates in vitro using adenylate cyclase conditions. [125I]bTSH bound specifically and with high affinity to a particulate fraction from normal thyroid and from benign and malignant thyroid neoplasms; this binding was inhibited by unlabeled bTSH (approximate Kd = 10.0 mU/ml for normal tissue; Kd = 2.5 mU/ml for thyroid neoplasms). Half-maximal activation of AC was obtained at a TSH concentration of approximately 2.5 mU/ml for both normal and neoplastic thyroid tissue, indicating that the high affinity TSH receptors are coupled to AC, at least in the neoplastic thyroid tissue. bTg and hTg did not inhibit [125I]bTSH binding to high affinity TSH receptors in either normal or neoplastic thyroid tissue. bTSH increased AC activity up to 25-fold in neoplastic thyroid tissue and up to 4-fold in normal thyroid tissue, whereas at concentrations up to 1 mg/ml, bTg had no effect. The current study demonstrates that bTSH binds to specific, high affinity receptors and stimulates AC activity in both normal and neoplastic thyroid tissue. bTg and hTg, under the conditions used in this experiment, do not influence TSH binding to its high affinity receptor in these tissues. Since Tg does not influence high affinity TSH binding or AC activity in a particulate fraction rich in plasma membranes from normal or neoplastic thyroid tissue, it is unlikely to have a modulating role on TSH action at the thyroid plasma membrane.

Thyroid-stimulating immunoglobulin bioassay using cultured human thyroid cells.

Modifications are described in the cultured thyroid cell cAMP assay for TSH which make it suitable for the measurement of thyroid-stimulating immunoglobulins. Comparison was made between this assay and two others measuring cAMP responsiveness in human thyroid tissue, namely the thyroid slice and thyroid plasma membrane adenylate cyclase assays, all performed with the same tissue sample. Of immunoglobulin G (IgG) samples from 7 unselected patients with untreated hyperthyroidism associated with Graves' disease, 5 produced significant stimulation of cAMP content in cultured thyroid cells when compared to pooled normal IgG. None of these 7 produced a statistically significant increase in thyroid slice cAMP content when assayed in triplicate, the same replicate number used in the cultured thyroid cell assay. Similarly, none of the same Graves' IgG samples produced significant stimulation (vs. control IgG) in the membrane adenylate cyclase assay, in which sensitivity to TSH stimulation was very poor. With a scaled-down modification of the assay using microtiter wells and acetylation to enhance detection of cAMP in the RIA, significant TSI activity was observed in 15 of 18 (83%) IgG samples from patients with untreated Graves' disease. The data indicate the excellent sensitivity and precision of the thyroid cell cAMP assay, as well as its convenience.

Transforming growth factor-beta 1 is a negative regulator for differentiated thyroid cancer: studies of growth, migration, invasion, and adhesion of cultured follicular and papillary thyroid cancer cell lines.

Invasion and metastasis may be caused by the escape of tumor cells from the negative control of growth factors. We analyzed the effects of transforming growth factor-beta 1 (TGF beta 1) on growth, migration, invasion, and adhesion in three follicular thyroid cancer cell lines (FTC133, primary; FTC236, lymph node metastasis; FTC238, lung metastasis) from one patient and in a papillary line (PTC-UC3). Cell growth was measured by dimethylthiazol-diphenyltetrazolium bromide assays, and migration (basal or epidermal growth factor stimulated) was determined by the ability of cells to penetrate 8-microns pore membranes that were covered with Matrigel for invasion assays. Moreover, we studied tumor cell adhesion to collagen type IV, fibronectin, and laminin. TGF beta 1 inhibited growth in FTC (FTC133, by 31%; FTC236, 15%; FTC238, 17%; P < 0.008), but not in PTC. Migration was inhibited in all cell lines. TGF beta 1 inhibited epidermal growth factor-stimulated migration of FTC133 by 43% vs. 29% without epidermal growth factor (P < 0.03). TGF beta 1 also inhibited invasion (FTC133, 32%; FTC236, 18%; FTC238, 16%; PTC-UC3, 32%; P < 0.02). All cell lines adhered preferably to collagen type IV and fibronectin. TGF beta 1 enhanced adhesion. Again, these effects were less pronounced in the FTC metastases. In conclusion, TGF beta 1 inhibits the growth, migration, and invasion of thyroid cancer cells in vitro. It enhances adhesion to components of the extracellular matrix. Metastatic thyroid tumors may be less responsive to the negative regulation of TGF beta 1.

Phenylacetate inhibits growth and vascular endothelial growth factor secretion in human thyroid carcinoma cells and modulates their differentiated function.

There is increasing evidence that phenylacetate inhibits growth and modulates differentiation in a variety of tumors with effects on gene expression, and protein prenylation and glycosylation at concentrations that have been safely used in humans. We evaluated the antineoplastic effects of phenylacetate in five thyroid cancer cell lines of follicular cell origin in vitro. We found early growth inhibition occurred with phenylacetate treatment at a dose of 2.5-10 mmol/L. The growth inhibition was cytostatic with the thyroid carcinoma cells arrested in the G0-1 cell phase. When evaluating the effect of phenylacetate on the differentiated functions of thyroid carcinoma cells, phenylacetate exposure: 1) decreased the TSH (10 mU/mL) growth response; 2) increased radioactive iodine (125I) uptake in two out of five cell lines; and 3) inhibited thyroglobulin secretion. Phenylacetate also inhibited the secretion of vascular endothelial growth factor (a glycoprotein dependent on glycosylation for efficient cellular excretion) from the thyroid cancer cell lines. Our results support that phenylacetate has an antiproliferative effect in many cell types, but the differentiating effects were not uniform. Importantly, we have identified that phenylacetate inhibits the secretion of vascular endothelial growth factor, which possibly mediates the antiangiogenic effects observed in vivo. Because of the minimal toxicity associated with phenylacetate treatment in humans, at concentrations we show to have a significant antineoplastic effect in thyroid carcinoma cells, phenylacetate could be useful in patients with differentiated thyroid cancer who fail conventional therapy or as an adjuvant to radioactive iodine therapy in patients with aggressive tumors.

Production of parathyroid hormone by a malignant nonparathyroid tumor in a hypercalcemic patient.

Few cases exist in which the production and secretion of PTH by malignant nonparathyroid tumors have been authenticated. A 69-yr-old man developed hypercalcemia complicating a primitive neuroectodermal malignancy that was widely metastatic. The serum level of intact PTH was markedly increased by immunoradiometric assay (90-290 ng/L; normal, 10-65 ng/L). The serum level of a PTH-related protein was also increased (19-20 ngeq/L; normal, < 10 ngeq/L). Exploration of the neck and mediastinum at two operations revealed four normal parathyroid glands. Extracts of the metastatic tumor contained immunoreactive PTH and transcripts of both the PTH and PTH-related protein genes. Thus, hypercalcemia in this patient was associated with production of PTH by a nonparathyroid malignancy.

Deoxyribonucleic acid cytometry helps identify parathyroid carcinomas.

It may be difficult in some patients with parathyroid tumors to distinguish between parathyroid carcinoma and parathyroid adenoma on the basis of clinical and histopathological findings. Patients initially diagnosed as having a parathyroid adenoma have subsequently occasionally developed metastases, and thereby their tumor was proven to be a carcinoma. To determine whether the nuclear DNA content would correlate with the clinical course and pathology of parathyroid tumors DNA cytometry was performed on parathyroid carcinomas (9 patients), histologically atypical adenomas (10 patients), adenomas associated with severe hypercalcemia [serum calcium, greater than or equal to 13.0 mg/dL (greater than or equal to 3.24 mmol/L); 11 patients], typical benign adenomas (11 patients), and incidentally removed normal parathyroid glands (6 patients). Sections were cut from the original paraffin-embedded surgical specimens and stained for nuclear DNA using the azure A Feulgen reaction. Nuclear DNA stain content was measured using an integrating image cytometer, and the results were plotted as histograms. Adjusted optical density (AOD) values were measured (in arbitrary units) to estimate the DNA content of whole nuclei in the specimens. The mean nuclear DNA content in the parathyroid carcinomas [24.6 +/- 2.1 (+/- SE) AOD] was significantly greater than that in the three groups of parathyroid adenomas (P less than 0.005, by unpaired t test) and in the normal parathyroid glands (P less than 0.0005). The mean nuclear DNA content in the atypical adenomas (15.8 +/- 1.6 AOD), profoundly hypercalcemic adenomas (16.8 +/- 1.3 AOD), and typical adenomas (16.0 +/- 1.1. AOD) were similar, and all were significantly greater than that in the normal parathyroid glands (11.5 +/- 0.7 AOD, P less than 0.05). Five distinct DNA histogram patterns were present in the parathyroid specimens from these 47 patients. Four of the 9 parathyroid carcinomas had an aneuploid DNA pattern, an abnormal pattern not found in any of the other groups; 2 of these tumors were originally diagnosed as atypical parathyroid adenomas. Both patients developed recurrent disease, and 1 died from a hepatic metastasis. Therefore, DNA cytometry provides valuable information in differentiating some parathyroid carcinomas from adenomas and diagnosing certain parathyroid carcinomas before the appearance of grossly invasive or metastatic tumor.

Immunocytochemical detection of p53 in human thyroid carcinomas is associated with mutation and immortalization of cell lines.

Mutations in the tumor suppressor gene p53 are the most-common mutations found in human cancers. In thyroid cancers, p53 mutations generally are found only in poorly differentiated and undifferentiated tumors and in cell lines. To determine the prevalence of p53 mutations in thyroid neoplasms and thyroid cell lines, we screened 58 thyroid tissues and 3 thyroid cell lines, p53 primers bracketing exons 4, 5/6, 7, and 8 were used to amplify genomic DNA using the PCR. Mutations were screened by denaturing gradient gel electrophoresis and confirmed by sequencing. The two papillary thyroid cancer cell lines and the follicular thyroid carcinoma cell line (positive control) had transitions (CGT->CAT) in exon 8, codon 273, resulting in the replacement of arginine with histidine. No normal thyroid tissues or primary tumors from which the cell lines were derived demonstrated exon 8 mutations, using this technique. p53 immunocytochemistry demonstrated a progression of p53 immunopositivity between synchronous and metachronous neoplasms, paralleling the neoplastic progression from a benign adenoma to primary carcinoma, regional, and distant metastasis and ultimately, the cell lines, where intense immunopositivity is noted. In addition, fluorescence in situ hybridization, using probes specific for the p53 locus, revealed the presence of 3 homologues of p53 in the follicular cell line and 2 homologues in the papillary and Hürthle cell lines. These results suggest that a point mutation present in a small number of original tumor cells and amplification of the mutant allele may be responsible for immortalizing well-differentiated thyroid cancer cells into cell lines.

Vascular endothelial growth factor expression is higher in differentiated thyroid cancer than in normal or benign thyroid.

Vascular endothelial growth factor (VEGF) is an angiogenic factor, and its expression has been rarely demonstrated in thyroid tumors. We, therefore, investigated the expression of VEGF messenger RNA (mRNA) and production of VEGF protein in cell lines from human primary and metastatic follicular (FTC-133, FTC-236, and FTC-238), papillary (TPC-1), Hürthle cell (XTC-1), and medullary thyroid cancers (MTC-1.1 and MTC-2.2), and in human thyroid tissues (papillary, follicular, medullary, and Hürthle cell cancers, follicular adenomas, and Graves' thyroid tissue) by Northern blot, immunohistochemistry, and enzyme-linked immunosorbent assay (ELISA) studies. All thyroid cell lines expressed a 4.2-kilobase VEGF mRNA. The VEGF mRNA levels were higher in the thyroid cancer cell lines than in primary cultures of normal thyroid cells, and higher in thyroid cancers of follicular than those of parafollicular cell origin. The VEGF mRNA levels were similar in primary and metastatic thyroid tumors. Immunohistochemical staining and Northern blot analysis of the cell lines correlated positively, thus thyroid cancer cell lines stained more intensely than normal thyroid cells and follicular tumor cells more intensely than parafollicular tumor cells. Again, no difference was noted in VEGF staining between primary and metastatic thyroid tumors. Deparafinized sections of papillary, follicular, and Hürthle cell cancers also stained much stronger than those of medullary thyroid cancers, benign, or hyperplastic (Graves' disease) thyroid tissue. Thyroid cancer cell lines (XTC-1 > TPC-1 > FTC-133 > MTC-1.1) also secreted more VEGF protein as measured by ELISA than did normal thyroid cells. VEGF secretion of cell lines derived from primary and metastatic thyroid tumors were similar. VEGF mRNA is therefore expressed, and VEGF protein is secreted by normal, hyperplastic, and neoplastic thyroid tissues. The higher levels of VEGF expression in differentiated thyroid cancers of follicular cell origin suggests a role in oncogenesis.