Gastrin-releasing peptide gene expression in developing, hyperplastic, and neoplastic human thyroid C-cells

Critical evaluation of the expression of gastrin-releasing peptide in dorsal root ganglia and spinal cord

There are substantial disagreements about the expression of gastrin-releasing peptide (GRP) in sensory neurons and whether GRP antibody cross-reacts with substance P (SP). These concerns necessitate a critical revaluation of GRP expression using additional approaches. Here, we show that a widely used GRP antibody specifically recognizes GRP but not SP. In the spinal cord of mice lacking SP (Tac1 KO), the expression of not only GRP but also other peptides, notably neuropeptide Y (NPY), is significantly diminished. We detected Grp mRNA in dorsal root ganglias using reverse transcription polymerase chain reaction, in situ hybridization and RNA-seq. We demonstrated that Grp mRNA and protein are upregulated in dorsal root ganglias, but not in the spinal cord, of mice with chronic itch. Few GRP⁺ immunostaining signals were detected in spinal sections following dorsal rhizotomy and GRP⁺ cell bodies were not detected in dissociated dorsal horn neurons. Ultrastructural analysis further shows that substantially more GRPergic fibers form synaptic contacts with gastrin releasing peptide receptor-positive (GRPR⁺) neurons than SPergic fibers. Our comprehensive study demonstrates that a majority of GRPergic fibers are of primary afferent origin. A number of factors such as low copy number of Grp transcripts, small percentage of cells expressing Grp, and the use of an eGFP GENSAT transgenic as a surrogate for GRP protein have contributed to the controversy. Optimization of experimental procedures facilitates the specific detection of GRP expression in dorsal root ganglia neurons.

Incidental thyroid C cell hyperplasia: clinical significance and implications in practice

Incidental C cell hyperplasia (CCH) following thyroidectomy for other indications may rarely be encountered, which may raise concerns about its clinical significance and proper management. CCH can be classified as physiological (reactive) or neoplastic. Reactive CCH has no malignant potential and can be observed in association with many other thyroid diseases (including differentiated thyroid cancer); in contrast, neoplastic CCH should be considered as a preneoplastic stage in the spectrum of C cell disease, ultimately leading to the development of medullary thyroid cancer (MTC). Neoplastic CCH is commonly observed in patients with germ-line mutations in the RET oncogene (commonly in families with a history of hereditary MTC, i.e. familial MTC or multiple endocrine neoplasia type 2 (MEN2)). CCH should be considered in patients with hypercalcitoninemia without nodular thyroidopathy. Total thyroidectomy, which is commonly performed for the majority of thyroid diseases, is an adequate treatment and achieves cure, even in patients with neoplastic CCH. There is no role for cervical lymph node dissection in patients with pure CCH. In conclusion, reactive CCH has no malignant potential, in contrast to neoplastic CCH. Total thyroidectomy achieves cure of patients with CCH.

Is Hashimoto's thyroiditis a risk factor for medullary thyroid carcinoma? Our experience and a literature review

The etiology of medullary thyroid carcinoma remains unknown. The aim of this study was to determine whether there is a significant association between medullary thyroid carcinoma and Hashimoto's thyroiditis in the histopathologic material of thyroidectomized patients. Retrospective cross-sectional study. In this study, we reviewed the medical records of all patients who underwent total thyroidectomy for different thyroid-related complaints between January 2000 and January 2012 at Jordan University Hospital-Amman, Jordan. To highlight relevant previously published studies addressing this topic, a literature search was conducted for English language studies reporting "medullary thyroid carcinoma" or "C-cell hyperplasia" in patients with Hashimoto's thyroiditis. Of the 863 patients with a mean age of 47.2 ± 12.3 years who underwent total thyroidectomy during the study period, 78 (9.04 %) were diagnosed with Hashimoto's thyroiditis, and 15 (1.74 %) had medullary thyroid carcinoma, 3 (20 %) of whom had coexistent Hashimoto's thyroiditis. A total of 683 (79.1 %) patients had benign thyroid disease, 67 (9.8 %) of whom had Hashimoto's thyroiditis. The difference between these rates was not statistically significant (p = 0.19). When examined by gender, 9 females had medullary thyroid carcinoma, 3 (33.3 %) of whom had coexistent Hashimoto's thyroiditis; by contrast, of 560 females with benign thyroid disease, 62 (11.1 %) had Hashimoto's thyroiditis (p = 0.04). Although this study population represents a small and single-institution experience, our results suggest that there might be an association between Hashimoto's thyroiditis and medullary thyroid carcinoma only in female patients who undergo total thyroidectomy.

Interstitial lung diseases in children

Interstitial lung disease (ILD) in infants and children comprises a large spectrum of rare respiratory disorders that are mostly chronic and associated with high morbidity and mortality. These disorders are characterized by inflammatory and fibrotic changes that affect alveolar walls. Typical features of ILD include dyspnea, diffuse infiltrates on chest radiographs, and abnormal pulmonary function tests with restrictive ventilatory defect and/or impaired gas exchange. Many pathological situations can impair gas exchange and, therefore, may contribute to progressive lung damage and ILD. Consequently, diagnosis approach needs to be structured with a clinical evaluation requiring a careful history paying attention to exposures and systemic diseases. Several classifications for ILD have been proposed but none is entirely satisfactory especially in children. The present article reviews current concepts of pathophysiological mechanisms, etiology and diagnostic approaches, as well as therapeutic strategies. The following diagnostic grouping is used to discuss the various causes of pediatric ILD: 1) exposure-related ILD; 2) systemic disease-associated ILD; 3) alveolar structure disorder-associated ILD; and 4) ILD specific to infancy. Therapeutic options include mainly anti-inflammatory, immunosuppressive, and/or anti-fibrotic drugs. The outcome is highly variable with a mortality rate around 15%. An overall favorable response to corticosteroid therapy is observed in around 50% of cases, often associated with sequelae such as limited exercise tolerance or the need for long-term oxygen therapy.

C cells evolve at the same rhythm as follicular cells when thyroidal status changes in rats

C cells are primarily known for producing calcitonin, a hypocalcemic and hypophosphatemic hormone. Nevertheless, besides their role in calcium homeostasis, C cells may be involved in the intrathyroidal regulation of follicular cells, suggesting a possible interrelationship between the two endocrine populations. If this premise is true, massive changes induced by different agents in the activity of follicular cells may also affect calcitonin-producing cells. To investigate the behaviour of C cells in those circumstances, we have experimentally induced two opposite functional thyroid states. We hyperstimulated the follicular cells using a goitrogen (propylthiouracil), and we suppressed thyroid hormone synthesis by oral administration of thyroxine. In both scenarios, we measured T(4), TSH, calcitonin, and calcium serum levels. We also completely sectioned the thyroid gland, specifically immunostained the C cells, and rigorously quantified this endocrine population. In hypothyroid rats, not only follicular cells but also C cells displayed hyperplastic and hypertrophic changes as well as increased calcitonin levels. When exogenous thyroxine was administered to the rats, the opposite effect was noted as a decrease in the number and size of C cells, as well as decreased calcitonin levels. Additionally, we noted that the two cell types maintain the same numerical relation (10 +/- 2.5 follicular cells per C cell), independent of the functional activity of the thyroid gland. Considering that TSH serum levels are increased in hypothyroid rats and decreased in thyroxine-treated rats, we discuss the potential involvement of thyrotropin in the observed results.

Possible association of CEA expression with oxyphilic change but not with C-cell hyperplasia in Hashimoto's thyroiditis

Reactive C-cell hyperplasia (CCH) has been observed in cases of autoimmune Hashimoto's thyroiditis; however, its occurrence in Graves' disease, the other major autoimmune disorder, has not yet been investigated. On the other hand, although Carcinoembryonic Antigen (CEA) serum levels have been reported elevated in patients with autoimmune thyroid disease (ATD), the source of CEA production at the cellular level is not elucidated. The aim of this study was to evaluate CCH and CEA immunohistochemical expression and comparatively analyze them in 136 ATD cases (107 Hashimoto's and 29 Graves' disease cases) and 20 cases of nodular hyperplasia (NH). Immunohistochemistry using monoclonal antibodies to chromogranin and CEA was performed. A scoring system for CCH and semiquantitative evaluation for CEA expression were applied. C-cell hyperplasia was absent in NH cases. In contrast, it was detected in 11% of ATD cases being more frequently observed in Hashimoto's (12.1%) than Graves' disease (6.8%) CCH associated to male sex and older age of Hashimoto's patients. CEA was detected only in ATD cases (33.8%), in C-cells and in follicular cells as well, being more frequently detected in Graves' (44.8%) than Hashimoto's (30.8%) disease. An interesting finding was an emerging possible association of CEA expression with oxyphilic change but not with C-cell hyperplasia in Hashimoto's thyroiditis. No significant correlation was established between CCH and CEA follicular cell expression in neither disease. In conclusion, C-cell hyperplasia and CEA expression may be encountered in the setting of Hashimoto's thyroiditis and Graves' disease.

Functional expression of the thyrotropin receptor in C cells: new insights into their involvement in the hypothalamic-pituitary-thyroid axis

Thyroid C cells, or parafollicular cells, are mainly known for producing calcitonin, a hormone involved in calcium homeostasis with hypocalcemic and hypophosphatemic effects. Classically, the main endocrine activity of this cell population has been believed to be restricted to its roles in serum calcium and bone metabolism. Nonetheless, in the last few years evidence has been accumulating in the literature with regard to local regulatory peptides secreted by C cells, such as somatostatin, ghrelin, thyrotropin releasing hormone or the recently described cocaine- and amphetamine-related transcript, which could modify thyroid function. As thyrotropin is the main hormone controlling the hypothalamic-pituitary-thyroid axis and, accordingly, thyroid function, we have examined the functional expression of the thyrotropin receptor in C-cell lines and in thyroid tissues. We have found that rat and human C-cell lines express the thyrotropin receptor at both mRNA and protein levels. Furthermore, incubation of C cells with thyrotropin resulted in a 10-fold inhibition of thyrotropin-receptor expression, and a concomitant decrease of the steady-state mRNA levels for calcitonin and calcitonin gene-related peptide determined by quantitative real-time PCR was found. Finally, thyrotropin receptor expression by C cells was confirmed at protein level in both normal and pathological thyroid tissues by immunohistochemistry and immunofluorescence. These results confirm that C cells, under regulation by thyrotropin, are involved in the hypothalamic-pituitary-thyroid axis and suggest a putative role in local fine-tuning of follicular cell activity.

Application of immunohistochemistry to thyroid neoplasms

CONTEXT

Thyroid lesions with nodular architecture and follicular pattern of growth often pose difficulties in accurate diagnosis during the assessment of cytologic and histologic specimens. The diagnosis of follicular neoplasm on cytology or of follicular tumor of uncertain malignant potential on histology is likely to cause confusion among clinicians and delay effective management of these lesions. Occasionally, thyroid tumors represent unusual or metastatic lesions and their accurate diagnosis requires immunohistochemical confirmation.

OBJECTIVE

To review the literature on the applications of immunohistochemistry in the differential diagnosis of thyroid tumors.

DATA SOURCES

Relevant articles indexed in PubMed (National Library of Medicine) between 1976 and 2006.

CONCLUSIONS

Our review supports the use of ancillary techniques involving a panel of antibodies suitable for immunohistochemistry and molecular analysis in the assessment of thyroid nodules. These tools can improve diagnostic accuracy when combined with standard morphologic criteria.

The cyclic AMP-dependent protein kinase A pathway is involved in progesterone effects on calcitonin secretion from TT cells

It is well known that gonadal steroid hormones influence the level of plasma calcitonin (CT), but the mechanism by which progesterone affects CT secretion is not clear. Immortalized TT cells are a reliable model system for studying the endocrine function of human parafollicular cells. In the present study, the effects of progesterone on CT secretion were examined in TT cells. TT cells were incubated in medium containing vehicle (DMSO), progesterone or BSA-progesterone for 60 or 150 min, and then the levels of CT in the medium, progesterone receptors, cAMP accumulation and CT mRNA expression were measured. To study the correlation between progesterone effects and the cAMP-dependent protein kinase A (PKA) pathway, cell lysates or cells in 24-well plates were treated with either vehicle or progesterone plus RU486, SQ22536, KT5720, or 3-isobutyl-1-methylxanthine. Then, adenylyl cyclase and protein kinase A (PKA) activities were measured in the cell lysates, and the CT levels were measured in the medium from the 24-well plate. The activated cAMP response element binding protein (P-CREB) was also measured by immunofluorescence. Administration of 1 microM progesterone or 500 nM BSA-progesterone increased the secretion of CT by 381% and 100%, respectively. Progesterone receptors A and B were downregulated by progesterone treatment. The cAMP concentration, adenylyl cyclase and PKA activity, CT mRNA expression, and nuclear P-CREB concentrations all showed an increase after progesterone treatment. RU486, SQ22536 and KT5720 inhibited the progesterone-stimulated effects. These results suggest that a cAMP-dependent PKA pathway is involved in progesterone-stimulated effects on CT secretion from TT cells.

Bombesin inhibits alveolarization and promotes pulmonary fibrosis in newborn mice

RATIONALE

Bombesin-like peptides promote fetal lung development. Normally, levels of mammalian bombesin (gastrin-releasing peptide [GRP]) drop postnatally, but these levels are elevated in newborns that develop bronchopulmonary dysplasia (BPD), a chronic lung disease characterized by arrested alveolarization. In premature baboons with BPD, antibombesin antibodies reduce lung injury and promote alveolarization.

OBJECTIVES

The present study tests whether exogenous bombesin or GRP given perinatally alters alveolar development in newborn mice.

METHODS

Mice were given peptides intraperitoneally twice daily on Postnatal Days 1-3. On Day 14 lungs were inflation-fixed for histopathologic analyses of alveolarization.

MEASUREMENTS AND MAIN RESULTS

Bombesin had multiple effects on Day 14 lung, when alveolarization was about half complete. First, bombesin induced alveolar myofibroblast proliferation and increased alveolar wall thickness compared with saline-treated control animals. Second, bombesin diminished alveolarization in C57BL/6 (but not Swiss-Webster) mice. We used receptor-null mice to explore which receptors might mediate these effects. Compared with wild-type littermates, bombesin-treated GRP receptor (GRPR)-null mice had increased interstitial fibrosis but reduced defects in alveolarization. Neuromedin B (NMB) receptor-null and bombesin receptor subtype 3-null mice had the same responses as their wild-type littermates. GRP had the same effects as bombesin, whereas neither NMB nor a synthetic bombesin receptor type 3 ligand had any effect. All effects of GRP were abrogated in GRPR-null mice.

CONCLUSIONS

Bombesin/GRP can induce features of BPD, including interstitial fibrosis and diminished alveolarization. GRPR appears to mediate all effects of GRP, but only part of the bombesin effect on alveolarization, suggesting that novel receptors may mediate some effects of bombesin in newborn lung.

Comparative in vitro and in vivo evaluation of two 64Cu-labeled bombesin analogs in a mouse model of human prostate adenocarcinoma

Bombesin (BBN), an analog of human gastrin-releasing peptide (GRP), binds to the GRP receptor (GRPR) with high affinity and specificity. Overexpression of GRPR has been discovered in mostly androgen-independent human prostate tissues and, thus, provides a potential target for prostate cancer diagnosis and therapy. We have previously demonstrated the feasibility of the positron emission tomography (PET) imaging using 64Cu-1,4,7,10-tetraazadodecane-N,N',N'',N'''-tetraacetic acid (DOTA)-[Lys3]BBN to detect GRPR-positive prostate cancer. In this study, we compared the receptor affinity, metabolic stability, tumor-targeting efficacy, and pharmacokinetics of a truncated BBN analog 64Cu-DOTA-Aca-BBN(7-14) with 64Cu-DOTA-[Lys3]BBN. Binding of each DOTA conjugate to GRPR on PC-3 and 22Rv1 prostate cancer cells was evaluated with competitive binding assay using 125I-[Tyr4]BBN as radioligand. In vivo pharmacokinetics was determined on male nude mice subcutaneously implanted with PC-3 cells. Dynamic microPET imaging was performed to evaluate the systemic distribution of the tracers. Metabolic stability of the tracers in blood, urine, tumor, liver and kidney was studied using high-performance liquid chromatography. The results showed that 125I-[Tyr4]BBN has a K(d) of 14.8+/-0.4 nM against PC-3 cells, and the receptor concentration on PC-3 cell surface is approximately 2.7+/-0.1 x 10(6) receptors per cell. The 50% inhibitory concentration value for DOTA-Aca-BBN(7-14) is 18.4 +/- 0.2 nM, and that for DOTA-[Lys3]BBN is 2.2 +/- 0.5 nM. DOTA-[Lys3]BBN shows a better tumor contrast and absolute tumor activity accumulation compared to DOTA-Aca-BBN(7-14). Studies on metabolic stability for both tracers on organ homogenates showed that 64Cu-DOTA-[Lys3]BBN is relatively stable. This study demonstrated that both tracers are suitable for targeted PET imaging to detect the expression of GRPR in prostate cancer, while 64Cu-DOTA-[Lys3]BBN may have a better potential for clinical translation.

Practical markers used in the diagnosis of endocrine tumors

Endocrine tumors constitute a large group of neoplasms that are widely dispersed throughout the body. They are made up mostly of neuroendocrine tumors (NE), which are characterized by the presence of secretory granules and production of peptide hormones, and non-NE tumors such as those derived from thyroid follicular cells and adrenal cortical cells. Immunohistochemical markers have been used to characterize these lesions and distinguish them from other histologically similar tumors. Chromogranin and synaptophysin are the most widely used broad-spectrum neuroendocrine tumor markers. The use of antibodies to transcription factors, keratins, and specific peptides is quite valuable in the diagnosis of endocrine tumors. This article reviews the common markers used to characterize endocrine tumors and to recognize tumors involved in the differential diagnosis of specific lesions.

Detection of hematogenic and lymphogenic tumor cell dissemination in patients with medullary thyroid carcinoma by cytokeratin 20 and preprogastrin-releasing peptide RT-PCR

Despite an extensive surgical approach only 50% of the patients with medullary thyroid carcinoma (MTC) are biochemically cured. The failure to cure a larger number of patients is a result of the early dissemination of MTC. The present study evaluates two RT-PCR based assays for the detection of disseminated tumor cells in blood, bone marrow and lymph node samples of patients with MTC. Frozen tissue and blood samples of 19 patients with MTC and 61 cervical lymph nodes of these patients were obtained intraoperatively during thyroidectomy and lymphadenectomy. Preoperative bone marrow samples were obtained from 8 patients with MTC. An expression of CK20 and preproGRP was found in all MTC tissue samples. Using CK20-PCR, disseminated MTC cells were detected in 67% of the cervical lymph nodes of patients with MTC, compared to 72% involved lymph nodes, detected by preproGRP-PCR. In 16 of 61 nodes (26%) each PCR-system detected disseminated tumor cells in histologically tumor-free lymph nodes. Disseminated tumor cells were detected with CK20-PCR and preproGRP in 5 of 18 (28%) preoperative blood samples, each. The detection of a hematogenic tumor cell dissemination by preproGRP correlated significantly with the tumor stages (p = 0.019). Circulating MTC cells were found in 3 of 8 bone marrow samples with CK20-PCR, compared to 1 of 8 samples with preproGRP-PCR. Both PCR assays are highly sensitive to detect disseminated MTC cells in blood, bone marrow and lymph node samples. Our results of disseminated MTC cells in 26% of histologically tumor-free cervical lymph nodes and in 28% of the blood samples of patients with MTC might therefore explain the low biochemical cure rates.

Bombesin-like peptide mediates lung injury in a baboon model of bronchopulmonary dysplasia

The etiology of bronchopulmonary dysplasia (BPD), a chronic lung disease of infants surviving respiratory distress syndrome, remains fundamentally enigmatic. BPD is decreasing in severity but continues to be a major problem in pediatric medicine, being especially prevalent among very premature infants. Increased numbers of pulmonary neuroendocrine cells containing bombesin-like peptide (BLP) have been reported to occur in human infants with BPD. We tested the hypothesis that BLP mediates BPD using the hyperoxic baboon model. Urine BLP levels increased soon after birth only in 100% O2-treated 140-d animals which developed BPD, correlating closely with severity of subsequent chronic lung disease. Similar elevations in urine BLP were observed in the 125-d baboon "interrupted gestation" model of BPD. Postnatal administration of anti-BLP antibody attenuated clinical and pathological evidence of chronic lung disease in the hyperoxic baboon model. Urine BLP could be a biological predictor of infants at risk for BPD, and blocking BLP postnatally could be useful for BPD prevention.

Evaluation of the role of mammalian thyroid parafollicular cells

In this report recent views are presented on the role of the parafollicular cells (PF) in the mammalian thyroid. Contemporary studies indicate morphological and functional heterogeneity of the PF cell population. In normal conditions most PF cells synthesize and secrete calcitonin (CT) and therefore they are frequently referred to as C cells. It seems however, that the contribution to the regional intrathyroidal regulation of secretion and growth processes is also an important role of all functionally mature PF cells of APUD (amine precursor uptake and decarboxylation) series. This has been confirmed by the latest reports on PF cells secreting numerous regulatory peptides (RP) usually defined as "paracrine" and/or "autocrine factors". These peptides are produced jointly with other RP in the same PF cells. Some of RP like CT, somatostatin, katacalcin I (CCP-I), CCP-II, gastrin-releasing peptide, thyroliberin and helodermin have been found in the PF cells, exclusively. Other RP, including calcitonin gene-related peptide, N-terminal peptide, neuromedin U, cholecystokinin and secretory peptide-I, have been simultaneously observed in the PF cells and intrathyroidal nerve fibres. Genetic mechanisms involved in RP production in the PF cells and possible path ways by which these peptides affect the adjacent follicular cells in the thyroid are discussed.

C-cell hyperplasia associated with chronic lymphocytic thyroiditis: a retrospective quantitative study of 112 cases

Since the first description by Wolfe et al of C-cell hyperplasia (CCH) in asymptomatic relatives of patients suffering from a medullary thyroid carcinoma (MTC), several investigators have described CCH associated with a chronic lymphocytic thyroiditis (CLT) not within the context of MTC or multiple endocrine neoplasia (MEN). We report the study of C-cell density in 112 cases of CLT on retrospective surgical material to determine the frequency of the association between CCH and CLT. The cases of CLT were compared with 19 normal thyroid glands obtained at necropsy. C cells, immunoreactive with a polyclonal anti-calcitonin (CT) antibody, were counted at high magnification (X400) and the number of low-power magnification (X100) microscopic fields (LPFs) containing at least 50 C cells per slide was assessed. Image analysis was performed to determine the C-cell density expressed in number of C cells/cm2. C-cell hyperplasia was defined by the following criteria: C-cell density > 40 cells/cm2 and the presence of at least three LPFs containing more than 50 C cells. Twenty percent of the cases of CLT showed a CCH thus defined, and four of them had an elevated serum CT level. Statistical analysis showed no clinical or biological correlation with the presence of CCH. However, the frequency of CCH was higher if a follicular cell carcinoma was associated with CLT. This study confirms a pathological association between CCH and CLT, provides new criteria for the definition of CCH on surgical pathology material, and reports four cases with an elevated serum CT level not within the context of MTC or MEN.

Mammalian bombesin as a hormone in ovine pregnancy: ontogeny, origin, and molecular forms

Mammalian gastrin-releasing peptides (GRP) are present in female reproductive tissues and stimulate uterine contraction and DNA synthesis in the endometrium. We set out to establish whether the GRP were likely to play a role in fetal development by measuring the fetal and maternal plasma concentrations in chronically cannulated fetal sheep from 115 days gestation to term (145 days) and for 18 days after parturition. Placental fluids and fetal urine were also obtained. In a separate series of animals, uterine, placental, and fetal gut and lung tissues were collected. Samples were extracted in acid and assayed by radioimmunoassay, and molecular forms were characterized by high-performance liquid chromatography. GRP were present in the decidua (> 10 pmol/g), as well as placental, uterine, lung, and gastrointestinal tissues (all < 6 pmol/g). Fetal and maternal plasma GRP were elevated compared with nonpregnant ewes, falling sharply after parturition. Placental fluids and urine also contained GRP (80-410 fmol/ml). The main molecular form in all tissues and fluids examined coeluted with porcine GRP-(18-27). GRP immunoreactivity was primarily localized to epithelial cells of the decidua. These data suggest that plasma GRP is probably derived from the decidua and may play a role as a circulating hormone in ovine fetal and uterine development.

Anti-bombesin monoclonal antibodies modulate fetal mouse lung growth and maturation in utero and in organ cultures

Fetal pulmonary neuroendocrine cells (PNECs) contain abundant gastrin-releasing peptide (GRP, mammalian bombesin-like peptide [BLP]). Previously, addition of bombesin resulted in increased fetal lung growth and maturation in utero and in organ cultures. A monoclonal antibody (mAb) to bombesin (2A11) blocked baseline automaturation of lung organ cultures in serum-free medium. In the present study, we analyze lung development following daily in utero administration of 2A11 from gestational days 15-18. Fetal lung treated with 2A11 and then harvested on day 18 demonstrated a dose-dependent decrease in surfactant phospholipid synthesis compared to controls treated with MOPC, an unreactive mAb. However, 2A11-treated fetal lung harvested on day 17 showed paradoxical increases in 3H-choline incorporation into saturated phosphatidylcholine, 3H-thymidine incorporation into DNA, and relative numbers of differentiated type II pneumocytes. In serum-containing day 17 lung organ cultures, 2A11 stimulated choline and thymidine incorporation. Since epidermal growth factor (EGF) is the only agent besides bombesin known to stimulate both fetal lung growth and maturation, we added EGF to serum-free cultures and reconstituted the stimulatory effects. A murine EGF receptor mAb (ERA) blocked 2A11-induced lung growth and maturation in serum-containing cultures, and this effect was overcome by adding EGF. In vivo, ERA also blocked stimulatory effects of 2A11 in fetal lung on day 17. These observations suggest that EGF receptor up-regulation may maintain lung growth and maturation if BLP levels are diminished on day 17. Nonetheless, BLPs appear to be involved in lung maturation on day 18, supporting a role for PNECs in normal lung development.

Effect of gastrin-releasing peptide on the pancreatic tumor cell line (Capan)

Gastrin-releasing peptide (GRP) has previously been shown to be an autocrine growth factor for small cell lung cancer, and our objective in the study presented here was to determine whether GRP has a similar role in pancreatic cancer. Using 125I-GRP, we demonstrated binding to specific, saturable, high-affinity sites (Kd = 1 nM; Bmax = 245 fmol/mg protein) in membrane preparations from the pancreatic tumor cell line Capan. The receptors were found to be biologically active. In whole cells, a GRP analogue bound to these receptors and stimulated rapid transfer of tritium from the tritiated lipid inositol pool to inositol triphosphates. Exogenous GRP addition stimulated incorporation of [3H]thymidine into DNA 20-60%. This stimulatory effect was blocked by the addition of a monoclonal antibody that complexed specifically with the receptor-binding portion of the peptide. In addition, the monoclonal antibody inhibited the growth of Capan cells in an in vitro growth assay without exogenous peptide. Bombesin receptor-specific antagonists also inhibited growth in a similar fashion. These data suggest that paracrine production of GRP may be important in pancreatic tumor growth, or that low-levels of a GRP-like peptide may play an autocrine role in this tumor.

Increase in cytoplasmic Ca2+ and stimulation of calcitonin secretion from human medullary thyroid carcinoma cells by the gastrin-releasing peptide

Examination was made of the effects of gastrin-releasing peptide (GRP) on human medullary thyroid carcinoma cells (TT cells). GRP stimulated calcitonin(CT) release in a concentration-dependent manner at 0.1-1000 nmol/l. On adding forskolin along with GRP, CT release was greater than by GRP alone. The stimulatory effect of A23187 was not additive. Intracellular free calcium concentration ([Ca2+]i) was measured for individual TT cells loaded with fura-2. The addition of GRP caused a rapid and transient rise in [Ca2+]i in a concentration-dependent manner followed by a sustained increase in [Ca2+]i. In the medium without Ca2+, this sustained increase did not occur and the concentration of CT release from TT cells by GRP was reduced by approximately a half. GRP would thus appear to be importantly involved in the regulation of thyroid C cell function through modulation of [Ca2+]i.

Gastrin-releasing peptide gene expression in small cell and large cell undifferentiated lung carcinomas

Gastrin-releasing peptide (GRP; mammalian bombesin) is present in the neuroendocrine cells of human fetal lung and in small cell lung carcinomas (SCLCs), where it may act as a growth factor. Considering the potential importance of GRP as a tumor marker, we have conducted a retrospective immunohistochemical analysis of 176 lung tumors for markers of GRP gene expression, as well as several other markers of neuroendocrine cell differentiation: chromogranin A, neuron-specific enolase, and calcitonin. The majority of carcinoids contained mature GRP, in contrast to only a minority of SCLCs and large cell lung carcinomas (LCLCs). However, a majority of SCLCs and LCLCs contained proGRP immunoreactivity. In situ hybridization did not add any information beyond what was obtained using proGRP antisera. In spite of sharing these neuroendocrine cell markers, SCLCs are associated with a graver prognosis than LCLCs. No prognostic significance was associated with immunostaining for GRP or several other markers of neuroendocrine cell differentiation.

Inhibitory effect of bombesin and SMS 201-995 on DNA synthesis in the rat thyroid lobes incubated in vitro

The effects of 4-h incubation in the presence of bombesin on the incorporation of [3H]-thymidine into DNA of the rat thyroid lobes, collected from animals treated in vivo with a long-acting somatostatin analog (SMS 201-995) or with 0.9% NaCl, were investigated. It was shown that not only in vivo injections of SMS 201-995, but also, unexpectedly, in vitro incubation with bombesin inhibited [3H]-thymidine incorporation. The two examined substances did not reveal any additive action in their inhibitory effects on the thyroid growth.

Isolation of a gastrin releasing peptide receptor from normal rat pancreas

The presence of a putative GRP receptor on rat pancreatic particulate membranes was demonstrated by covalent cross-linking to 125I-gastrin releasing peptide (GRP), which revealed a radioactive band with Mr = 80-90 kDa on reduced SDS-PAGE. Fresh rat pancreatic membranes contained a GRP receptor which was solubilized with Triton X-100 as assessed by its failure to sediment at 100,000 x g for one hour and its ability to pass through a 0.22 mu filter. When 125I-GRP binding was studied using Sephadex G50 gel filtration chromatography to separate bound from unbound ligand, substantial amounts of 125I-GRP binding were observed in rat crude solubilized pancreatic membranes, but essentially no specific binding was observed until the crude solubilized membranes were fractionated by ammonium sulfate precipitation. Specific 125I-GRP binding was 500, 700 and 1400 fmol/mg protein, respectively, in the 0-25%, 25-50% and 50-80% saturated ammonium sulfate fractions (125I-GRP concentration = 1 nM). Specific binding was temperature dependent, saturable and of high affinity, (KD = 2.3 nM). A unique 70 kDa band was visualized by silver staining of the SDS-PAGE of eluates of GRP(14-27) affinity gel compared with eluates of control affinity gels incubated with the 25-50% (NH4)2SO4 fraction. The lower Mr than that observed with covalent cross-linking may represent the binding subunit of a larger receptor protein. This ligand-affinity isolated protein is thus a good candidate for the GRP receptor, or the binding subunit of it, from normal rat pancreas.

Immunocytochemical localization and identification of members of the pancreatic polypeptide (PP)-fold family in human thyroid C cells and medullary carcinomas

An increasing number of regulatory peptides not coded by the calcitonin genes are known to occur in the thyroid C cells. We have now carried out light and electron microscopic immunocytochemical analyses on specimens of normal human thyroids and medullary carcinomas to establish the occurrence of members of the PP-PYY-NPY family in the C cell system. By means of site-directed immunocytochemistry we provide the first evidence that a molecule closely related to proNPY is present in normal and pathologic C cells, and is co-stored with calcitonin in the cytoplasmic dense-core granules. Preliminary observations also suggest that high levels of expression of NPY-gene products help to define a subset of tumours with a less aggressive behaviour.

Bombesin increases fetal lung growth and maturation in utero and in organ culture

Pulmonary neuroendocrine cells (PNECs) in fetuses synthesize gastrin-releasing peptide (GRP, or mammalian bombesin) at high levels, but the role of this hormone in lung development has been obscure. The present study demonstrates that bombesin administered for 2 to 4 d toward the end of gestation in utero led to increased DNA (days 17 and 18) and saturated phosphatidylcholine (SPC) synthesis (day 18) in a dose-dependent fashion in fetal lung. These kinetics coincide with the timing of endogenous GRP gene activation in untreated fetal mouse lung, where GRP mRNA is detectable on day 16 and peaks at day 18. Electron microscopy on in vivo bombesin-treated fetal lung showed an increase in the number of cells containing lamellar bodies on both days 17 and 18, consistent with increased growth and/or maturation of type II cells. In mouse fetal lung organ cultures, the addition of bombesin led to accelerated uptake of [3H]thymidine into DNA, [3H]leucine into protein, and [3H]choline into SPC, indicating that increased growth and maturation may be direct effects. Extending these observations to another species, bombesin was found to induce growth and maturation of human fetal lung in organ culture. A monoclonal antibody to bombesin (2A11) prevented bombesin-induced increases in choline and thymidine incorporation in lung organ cultures and also blocked baseline automaturation of control lung organ cultures in serum-free medium. These data suggest that bombesin, and thus PNECs, play a role in normal lung development.

The intratumoral immunoassayable somatostatin concentration is frequently elevated in medullary thyroid carcinoma. Results in 34 cases

The current work has been performed by the Cooperative French Group of Medullary Thyroid Carcinoma (GETC). A systematic evaluation of RIA somatostatin (SRIH) was performed in 34 medullary thyroid carcinomas (MTC) (25 inherited, seven sporadic). Plasma SRIH was measured by radioimmunoassay in parallel with calcitonin (CT) and carcinoembryonic antigen (CEA). Immunoassayable SRIH was tested in fresh tumoral tissue samples from the same 34 MTC and, for comparison, in 10 nontumoral thyroid extracts (less than 6 pmol/g wet). Although plasma SRIH was only slightly elevated in two of 20 cases, tumoral SRIH was elevated in 70.6% of our MTC (10 to 3973 pmol/g). The chromatography of two tumoral extracts showed that somatostatin 14 was the major molecular form. We found no correlation (P greater than 0.1) between tumoral SRIH and the following: (1) tumor size (r = 0.227); (2) epidemiologic form of MTC (r = 0.144); (3) plasma SRIH (r = 0.045), plasma CT (R = 0.095) or (4) plasma CEA (r = 0.032). Thus, in the authors' experience, SRIH appears as a major product of tumoral C-cell in human MTC, even when plasma SRIH is normal and SRIH immunohistochemical staining is scarce. Multiple hormonal production of these tumors may explain its presence but SRIH may act also as a regulator, since negative influence of SRIH on CT is demonstrated in normal as well in tumoral conditions.