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At least 19 recordsLinked to original sources
PubMed1992

Gastrin-releasing peptide stimulation of corticotropin secretion in male rats.

Gastrin-releasing peptide (GRP; mammalian bombesin) may be involved in the neuroendocrine regulation of pituitary hormone secretion. We investigated the effect of GRP on ACTH secretion in conscious male rats. GRP (7-700 pmol) stimulated ACTH secretion dose-dependently after intracerebroventricular (icv) administration but had no effect after iv administration. GRP infused icv in a dose of 7 pmol, which alone increased ACTH 1.5-fold, potentiated the ACTH-releasing effect of arginine vasopressin (AVP; 80 pmol iv) and corticotropin-releasing hormone (CRH; 100 pmol iv). A higher dose of GRP (70 pmol icv), which stimulated ACTH secretion 2-fold, potentiated the effect of 80 and 400 pmol AVP iv, but had only additive effect on the ACTH response to 800 pmol AVP iv or 100 pmol CRH iv. GRP infused iv in a dose of 210 pmol, which in itself had no effect on ACTH secretion, potentiated the ACTH-stimulating effect of AVP and CRH approximately 2.5-fold. The effect of GRP (icv or iv) on AVP or CRH-stimulated ACTH release was only slightly smaller than the effect of combined administration of AVP and CRH (80 + 100 pmol iv). The ACTH-stimulating effect of GRP (700 pmol icv) was inhibited about 60% by pretreatment with either CRH or AVP antiserum and prevented by combined pretreatment with the antisera. The results indicate that: 1) GRP affects ACTH secretion indirectly at a suprapituitary level--possibly in the hypothalamus--by stimulating the release of AVP and CRH to the pituitary portal blood; and 2) GRP acts directly at the pituitary level to augment the effect of AVP and CRH on the corticotrophs. We suggest that GRP is involved in the multifactorial regulation of ACTH secretion.

Adrenocorticotropic Hormone↗
PubMed1992

Expression of the vasopressin and gastrin-releasing peptide genes in small cell lung carcinoma cell lines.

Various polypeptide hormones including vasopressin (VP) and gastrin-releasing peptide (GRP) are produced by small cell lung carcinomas (SCLC). VP as well as GRP have mitogenic effects on several cell types and are proposed to be autocrine growth factors. In this study the presence of VP mRNA, oxytocin (OT) mRNA and GRP mRNA was investigated in cell lines derived from SCLCs. Out of 26 cell lines 3 contained low amounts of VP mRNA (GLC-8, SCLC-21H and NCI-H345) and 7 contained abundant GRP mRNA (GLC-16, GLC-1-M13, SCLC-22H, NCI-H249, NCI-H345, NCI-H449 and NCI-H450). The GRP mRNA-containing cell lines belong to the classic SCLC type, whereas VP mRNA was found in two classic and one variant cell line. None of the SCLC cell lines contained detectable levels of OT mRNA. Of the three VP-expressing SCLC cell lines, GLC-8 had the highest level of VP mRNA. Both the length of the transcript and the hybridization with different probes containing exons A and C of the VP gene suggest that the detected transcript is a normal VP messenger. SCLC GLC-8 contained low levels of VP immunoreactivity and VP receptors. In GLC-8 an autocrine role of VP may be suspected.

Base Sequence↗
PubMed1992

Characterization of ligand binding and processing by gastrin-releasing peptide receptors in a small-cell lung cancer cell line.

The ligand-binding properties of the gastrin-releasing peptide (GRP) receptor and the cellular processing of GRP have been studied in the small-cell lung cancer (SCLC) cell line COR-L42. Scatchard analysis of GRP receptor expression indicated a single class of high-affinity receptors (Kd 1.5 nM) and approx. 6700 receptors/cell. GRP bound to its receptor with a Ki of 2.4 nM. The bombesin-related peptides neuromedin B (NMB) and phyllolitorin also bound to GRP receptors with Ki values of 22.7 and 59.1 nM respectively. Binding of 125I-GRP to COR-L42 cells increased rapidly at 37 degrees, achieved a maximum at 10 min and declined rapidly thereafter. At 4 degrees C, maximum binding was achieved at 30 min and the subsequent decline in cell-associated radioactivity was slower than that seen at 37 degrees C. Acid/salt extraction, to separate surface-bound ligand from internalized GRP, indicated that after receptor binding 125I-GRP was rapidly internalized. To determine the pathway of 125I-GRP degradation, binding studies were carried out with the lysosomotropic agent chloroquine (5 mM), and with phosphoramidon (10 microM), an inhibitor of the membrane-bound enzyme (EC 3.4.24.11). Both agents markedly inhibited the degradation of GRP, indicating that this process involves a lysosomal pathway and a phosphoramidon-sensitive pathway, possibly involving the EC 3.4.24.11 enzyme. GRP receptor down-regulation was observed following a 10 min exposure to 100 nM-GRP. With longer pretreatment times the number of binding sites recovered to 80% of control values. Treatment with 5 mM-chloroquine plus GRP or cycloheximide (10 micrograms/ml) plus GRP demonstrated that the majority of GRP receptors are recycled. NMB and phyllolitorin pretreatment did not influence the subsequent binding of 125I-GRP, suggesting that these peptides do not down-regulate GRP receptors.

Anti-Bacterial Agents↗
PubMed1992

Gastrin-releasing peptide: in vivo and in vitro growth effects on an acinar pancreatic carcinoma.

The mammalian gastrin-releasing-peptide (GRP) and its structural amphibian analogue, bombesin, are known to be trophic factors for the normal exocrine pancreas. This work investigates the possible role of GRP in the growth of an acinar pancreatic cancer transplanted to the rat and in primary tumor cell cultures. Moreover, this adenocarcinoma was tested for its content of specific bombesin/GRP receptors by using autoradiographic technics and in vitro binding assays with tumor cells. In Lewis rats bearing the pancreatic carcinoma transplanted s.c. in the scapular region, chronic administration of GRP at the dose 30 micrograms/kg/day for 15 successive days significantly increased the tumor volume, the final tumor weight, and amylase, protein, RNA and DNA contents. Autoradiographic studies showed that tumor tissue was GRP receptor positive with a high density. The biochemical characterization indicated that receptor positive tumor tissue had saturable and high affinity receptors with pharmacological specificity for GRP and its bioactive analogues. In primary tumor cell cultures, GRP increased the incorporation of [3H] thymidine in DNA in a dose- and time-dependent manner. There was a good correlation between the ability of GRP and its COOH terminal analogues to elicit DNA synthesis and their affinity for 125I-GRP binding sites. These results from in vivo and in vitro experiments demonstrated that GRP induces growth of pancreatic carcinoma by acting directly on specific membrane receptors present on the tumor cells.

Adenocarcinoma↗
PubMed1992

Induction and spontaneous regression of intense pulmonary neuroendocrine cell differentiation in a model of preneoplastic lung injury.

Pulmonary neuroendocrine cell (PNEC) hyperplasia is associated with chronic lung diseases in humans, where it is thought to play a role in reparative responses to lung injury. To investigate the kinetics of strongly induced PNEC hyperplasia in an animal model, we exposed hamsters to a combination of hyperoxia (60% O2) and diethylnitrosamine (DEN) for up to 20 weeks. We thus demonstrate not only the induction but also spontaneous regression of intense PNEC differentiation and growth, which are much more intense than those observed with DEN alone. Lung tissues were immunostained for serotonin, calcitonin gene-related peptide (CGRP), calcitonin (CT), and gastrin-releasing peptide (GRP) (mammalian bombesin). Between 9 and 12 weeks of treatment, the number of CGRP- and serotonin-positive neuroepithelial bodies per cm airway epithelium increased over 10-fold, and CT became detectable. The number of neuroepithelial bodies immunostained for CGRP, serotonin, and CT peaked at 12-14 weeks of treatment, thereafter regressing to near-control levels by 20 weeks, in spite of continued DEN/O2 treatment. Simultaneously, by 6-7 weeks of treatment, there was a significant increase in the mean number of CGRP-positive cells per neuroepithelial body, which continued to rise up to double control levels, with a plateau at 13-20 weeks. GRP and pro-GRP immunostaining were not detectable at any time point. Polymerase chain reaction analyses of neuroendocrine-specific mRNAs demonstrated that CGRP, CT, and GRP mRNAs (normalized for beta-actin) peaked in lung tissues from most animals at 9-14 weeks after the beginning of DEN/O2 treatment, with decreased expression at 16-20 weeks. These data suggest that regulation of levels of these neuropeptides may be primarily transcriptional. This model may be a valuable system for analyzing mechanisms of induction and regression of normal PNEC differentiation and growth.

Animals↗
PubMed1992

The response of regulatory peptides to moderate hypoglycaemia of short duration in type 1 (insulin-dependent) diabetes mellitus and in normal man.

The changes in plasma gastrin-releasing peptide (GRP), arginine vasopressin (AVP), neuropeptide Y (NPY), corticotropin releasing hormone (CRH), galanin, ACTH, cortisol, delta sleep-inducing peptide (DSIP), adrenaline, noradrenaline and pancreatic polypeptide (PP) were measured after 5 and 15 minutes of acute insulin-induced moderate hypoglycaemia (2.0 mmol/l) in 10 patients with Type 1 diabetes mellitus with no autonomic neuropathy and in 10 healthy subjects. Plasma catecholamine and PP levels rose in both groups in response to hypoglycemia and the secretory response of ACTH was lower in the diabetic subjects (p < 0.01). GRP concentrations increased during hypoglycaemia (p < 0.01) while a reduction in AVP occurred at the start of hypoglycaemia (p < 0.001). The plasma AVP concentrations were higher in the diabetic group compared with those in the normal group (p < 0.05). The NPY concentrations were higher in the normal subjects (p < 0.05) but no change in the mean level occurred in either group during hypoglycaemia. No group differences or changes in mean plasma concentrations were found for galanin, DSIP and CRH. These observations support the view that regulatory peptides, if involved in glucose homeostasis, may rather have a modulatory effect than a direct action in restoring normoglycaemia.

Adrenocorticotropic Hormone↗
PubMed1992

Growth of small cell lung cancer cells: stimulation by multiple neuropeptides and inhibition by broad spectrum antagonists in vitro and in vivo.

Neuropeptides are increasingly implicated in the control of cell proliferation and their mechanisms of action are attracting intense interest. The early complex cascade of events initiated by peptides of the bombesin family including gastrin-releasing peptide is increasingly understood. The cause-effect relationships and temporal organization of these early signals and molecular events provide a paradigm for the study of other growth factors and mitogenic neuropeptides and illustrate the activation and interaction of a variety of signaling pathways. These peptides may also act as autocrine growth factors for certain small cell lung cancer cells. The results discussed here strongly suggest that the autocrine growth loop of bombesin-like peptides may be only a part of an extensive network of autocrine and paracrine interactions involving a variety of Ca(2+)-mobilizing neuropeptides in small cell lung cancer including bradykinin, cholecystokinin, galanin, neurotensin, and vasopressin. In this context, broad spectrum antagonists that prevent the function of multiple Ca(2+)-mobilizing receptors are of special interest. These antagonists block neuropeptide mediated signals and inhibit small cell lung cancer growth in vitro and in vivo. Thus, broad spectrum neuropeptide antagonists constitute potential anticancer agents.

Amino Acid Sequence↗
PubMed1992

Molecular genetic analysis of two distinct receptors for mammalian bombesin-like peptides.

The mammalian bombesin-like peptides are known to be growth factors for certain cells with high-affinity bombesin receptors and have been implicated as autocrine growth factors influencing the pathogenesis and progression of a subset of human small-cell lung carcinomas. Thus, antagonists that interfere with bombesin receptor-ligand interaction might prove to be of value in treatment of gastrin-releasing peptide (GRP)-responsive tumors. A precise definition of the structure and properties of the bombesin receptors found on human lung cancer cells would provide important information for the design and rational application of such antagonists. Recently, we isolated cDNA clones encoding two distinct receptors for the mammalian bombesin-like peptides, GRP, and neuromedian B (NMB). The two receptors show 56% amino acid identity, encode seven putative transmembrane domains, and are members of the G-protein-coupled receptor superfamily. Ligand-binding studies show that while both receptors can be activated by either GRP or NMB, one receptor has a higher affinity for GRP than for NMB (GRP-R), while the other has a higher affinity for NMB than for GRP (NMB-R). A different spectrum of antagonists is needed to block responses from the two different receptors. These studies indicate that it will be critical in future studies to define which bombesin receptor subtypes are present on a given tumor to optimize the potential therapeutic benefit of antagonists in blocking growth.

Amino Acid Sequence↗
PubMed1992

Activation of neuromedin B-preferring bombesin receptors on rat glioblastoma C-6 cells increases cellular Ca2+ and phosphoinositides.

Recent cloning studies confirm the presence of two subtypes of bombesin (Bn) receptors. In contrast to the gastrin-releasing peptide (GRP)-preferring subtype, which has been widely studied, nothing is known about the cellular mechanisms of the neuromedin B (NMB)-preferring subtype, which occurs widely in the central nervous system and gastrointestinal tissues, partially because of the lack of a cell line with functional receptors. In the present study we have investigated Bn receptors on the rat glioblastoma cell line C-6, reported to contain mRNA of the NMB receptor subtype. Binding of 125I-[D-Tyr0]NMB to these cells was time- and temperature-dependent, saturable, reversible, and only inhibited by Bn receptor agonists or antagonists. For Bn receptor agonists the relative potencies were: NMB (1.7 nM) approximately equal to litorin (3 nM) greater than ranatensin (8 nM) greater than Bn (19 nM) greater than neuromedin C (NMC) (210 nM) greater than GRP (500 nM). These relative affinities were almost identical to those for the NMB receptor subtype on rat oesophageal tissue and for Balb 3T3 cells stably transfected with the NMB receptor subtype. These potencies differed from those for the GRP receptor subtype on rat pancreatic acini [Bn approximately equal to litorin (4 nM) greater than ranatensin, NMC, GRP (15-20 nM) much greater than NMB (351 nM)]. The relative potencies of four different classes of Bn receptor antagonists were compared. Results from C-6 tumour cells agreed closely with those for binding to the NMB receptor subtype on rat oesophageal tissue and in Balb 3T3 cells stably transfected with this receptor, and differed markedly from those for binding to the GRP receptor subtype on rat pancreatic acini. Four Bn receptor antagonists had a higher affinity for the GRP subtype ([D-Phe6]Bn-(6-13)ethyl ester (500 x), [D-Phe6][psi 13-14,Cpa14]Bn- (6-14) (70 x) (where psi 13-14 refers to the replacement of the -CONH- peptide bond between Leu13 and Met14 by -CH2NH2) [psi 13-14,Leu14]Bn, [D-Phe6]Bn-(6-13) propylamide (30 x)] and two had a higher affinity for the NMB subtype on C-6 cells and transfected cells ([D-Pro4,D-Trp7,9,10] substance P-(4-11) (9 x) and [Tyr4,D-Phe12]Bn (18 x)]. In C-6 tumour cells, Bn receptor agonists caused an increase in cytosolic Ca2+ and the generation of inositol phosphates. For both responses, NMB was more than 50-fold more potent than GRP. Neither NMB nor GRP increased cyclic AMP. These results demonstrate that the rat glioblastoma cell line C-6 possesses functional NMB-preferring Bn receptors, and agonist occupation activates phospholipase C, thus increasing cytosolic Ca2+ and inositol phosphate formation. Because the interaction of Bn-related peptides with C-6 cell receptors is identical with that reported in other tissues containing the mRNA for the NMB subtype, this cell line should prove useful in exploring further the cellular basis of action of the peptides that interact with this receptor in the central nervous system and various other tissues.

3T3 Cells↗
PubMed1992

Development of innumerable neuroendocrine tumorlets in pulmonary lobe scarred by intralobar sequestration. Immunohistochemical and ultrastructural study of an unusual case.

We describe the microscopic, histochemical, immunohistochemical, and ultrastructural features of hundreds of neuroendocrine tumorlets occurring within a pulmonary lobe severely scarred by intralobar sequestration in a nonsmoking 49-year-old white man. To our knowledge, there have thus far been no descriptions or detailed analyses of neuroendocrine tumorlets arising within a pulmonary sequestration. The neuroendocrine tumorlets appeared in the form of minute aggregates--mostly microscopic, up to a maximum of 0.3 cm in greatest diameter--of small round and short spindle-shaped cells. They were organized in compact nests of fascicles and were supplied with round or elongated euchromatic nuclei and scant weakly eosinophilic cytoplasm. The neuroendocrine tumorlets were clustered around diseased bronchioles or embedded in a fibrotic pulmonary parenchyma with a distinctive infiltrative appearance. Sometimes they lay near an artery channel without an identifiable bronchiole or herniated into distal airways. Most of the neuroendocrine tumorlets were strongly argyrophilic on Grimelius staining. Immunohistochemically, there was reactivity for markers of epithelial and neuroendocrine differentiation together with evidence of orthotopic production of calcitonin, serotonin, and gastrin-releasing peptide and ectopic production of vasoactive intestinal peptide. Ultrastructurally, most of the neuroendocrine cells showed 100- to 120-nm dense-core membrane-bound secretory granules; mucus secretory cells were also present. We prefer the term neuroendocrine tumorlets over the generally used term carcinoid tumorlets, because the nature of these lesions is undefined and the relationship with neuroendocrine pulmonary neoplasms is not yet established.

Calcitonin↗
PubMed1992

The correct dose: pharmacologically guided end point for anti-growth factor therapy.

Strategies to block the effects of tumor growth factors, such as estrogen, and to recruit other regulatory elements, such as with retinoids, have focused interest on the possibility of successful tumor intervention approaches. Approaches that neutralize the effects of critical molecules that drive tumor promotion are attractive targets for evaluation as new intervention agents. Clinical intervention trials with early stage patients or with subjects from "high risk" populations impose stricter types of constraints than conventional chemotherapy approaches in advanced stage patients. The potential for short-term toxicity has to be considered, as it may affect subject accrual or compliance. The longer expected survival of intervention subjects mandates closer attention to the possibilities of unexpected long-term toxicities with chronic administration of an intervention agent. As part of a Phase I clinical trial evaluating the utility of a monoclonal antibody directed against the autocrine growth factor, gastrin-releasing peptide to block the growth of small cell lung cancer, we developed a mathematical model to predict the requisite amount of antibody to neutralize growth factor effect. This model requires knowledge of the equilibrium concentration of the secreted growth factor, specific receptor, and bioavailability of the antibody in the tumor interstitium. A range of possible target doses of antibody can be developed to address the potential for heterogeneity frequently encountered in such systems, including a range of levels for peptide production and specific receptor expression. This approach could be applied to rationally derive treatment or intervention in which specific information regarding the relevant binding parameters is available. Through refinement of this modeling approach more context-specific dosing of agonist/antagonists could be determined which may decrease side effects associated with the drug administration.

Antibodies, Monoclonal↗
PubMed1992

A potent bombesin receptor antagonist inhibits bombesin-stimulated growth of mouse colon cancer cells in vitro: absence of autocrine effects.

Bombesin (BBS) exerts significant effects on the growth of a mouse colon cancer cell line (MC-26) in vitro. The presence of specific binding sites on MC-26 cells for gastrin-releasing peptide (GRP)/BBS-related peptides was recently reported by us. In the present study, we determined that the transcript size of the mRNA species that codes for GRP receptors is 9 kilobase pairs, which is similar to that reported for mouse Swiss 3T3 cells, using the complementary DNA probe for the GRP receptor gene from mouse Swiss 3T3 cells. We next examined the effects of potent GRP receptor antagonists, D-Phe6, bombesin(6-13)-propylamide (D-Phe6,BN(6-13)PA) and Leu13-psi-(CH2NH)Leu14-bombesin (LL-BBS), on BBS-stimulated growth of MC-26 cells in vitro. A possible autocrine role of GRP in the growth of MC-26 cells was also investigated. MC-26 cells were inoculated s.c. into male BALB/c mice, and tumors were harvested 21-28 days postinoculation. Both D-Phe6,BN(6-13)PA and LL-BBS significantly inhibited the binding of 125I-GRP to MC-26 tumor membranes in a dose-dependent manner, with 50% inhibitory concentrations of 4.5 +/- 0.52 nM and 87 +/- 6 nM, respectively. D-Phe6,BN(6-13)PA similarly inhibited the specific binding of 125I-GRP, cross-linked to a approximately 80 kilodalton binding protein on the MC-26 tumor membranes. In order to determine whether the BBS receptor antagonist, D-Phe6,BN(6-13)PA, functioned as an antagonist or an agonist of biological functions, we measured the bioefficacy of D-Phe6,BN(6-13)PA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Ovarian mucinous tumors frequently express markers of gastric, intestinal, and pancreatobiliary epithelial cells.

In 100 mucinous tumors of the ovary (37 benign, 24 borderline, and 39 malignant), the authors determined by histochemical and immunohistochemical techniques the frequencies and patterns of expression of a total of nine markers of gastric, intestinal, and pancreatobiliary duct epithelial cells. M1, a mucin antigen, and cathepsin E (CaE), an aspartic proteinase, two markers of normal gastric superficial/foveolar epithelial cells, were expressed in 95 and 92 tumors, respectively. Periodic acid-concanavalin A-reactive mucin or pepsinogen (PG) II, markers of gastric mucus neck and pyloric gland cells, were found in 79 tumors. All of these tumors also expressed M1 or CaE. DU-PAN-2 and the N-terminal epitope of gastrin-releasing peptide, markers of normal pancreatobiliary duct cells, were found in 70 and 49 tumors, respectively, and CAR-5 and M3SI, markers of intestinal mucin, were expressed in 51 and 30 tumors, respectively. All tumors expressed at least two of the nine markers studied; none expressed PG I, a marker of gastric chief cells. The mucopeptic cell marker, PG II, was significantly more common in benign and borderline than in malignant tumors (P less than 0.005), whereas CAR-5 and M3SI, markers of intestinal mucin, were expressed significantly more often in malignant than in benign and borderline tumors (P less than 0.001). By electron microscopic examination, many tumor cells had fine structural features characteristic of gastric superficial/foveolar and pyloric gland cells, intestinal columnar or goblet cells, and endocervical cells. The results indicate that gastroenteropancreatic cell differentiation--and, in particular, gastric type differentiation--is a prominent feature of ovarian mucinous tumors.

Adenocarcinoma, Mucinous↗
PubMed1992

Constitutive presence of a catalytic fragment of protein kinase C epsilon in a small cell lung carcinoma cell line.

Protein kinase C (PKC) has been implicated in a variety of cellular responses such as proliferation, differentiation, and secretion. We assessed the role of PKC in the mitogenic effects of gastrin-releasing peptide (in a small cell lung cancer (SCLC) cell line. Using antisera that specifically recognize the PKC isoforms alpha, beta, gamma, delta, and epsilon, we determined that PKC epsilon is the major isoform in the SCLC cell line NCI-N417, followed by PKC alpha and delta. In addition to the 90-kDa PKC epsilon, our anti-PKC epsilon antiserum specifically detected a 40-kDa immunoreactive protein. Treatment of the cells with either 20 nM phorbol myristate acetate or 50 nM GRP enhanced significantly the level of the 40-kDa protein in a time-dependent (1-8 h), cycloheximide-sensitive fashion. Subcellular fractionation revealed that 90% of PKC epsilon was in particulate form, while the 40-kDa immunoreactive protein was cytosolic. To test the hypothesis that the 40-kDa soluble protein represented a catalytically independent PKC epsilon fragment, cytosolic extracts were assayed for kinase activity. 45-50% of the activity was apparent in the absence of the PKC activators phosphatidylserine and diacylglycerol. This effector-independent kinase activity was further purified by affinity chromatography using a synthetic peptide corresponding to the pseudosubstrate region of PKC epsilon (ERMRPRKRQGAVRRRV) coupled to Sepharose. The partially purified protein, recognized by the anti-PKC epsilon antiserum, exhibited histone kinase activity with kinetics similar to those of the tryptically generated catalytic fragment of brain PKC epsilon. This activity was inhibited by staurosporine (IC50 = 1 x 10(-8) M) and by the pseudosubstrate inhibitor peptide (IC50 = 7.7 x 10(-8) M). The SCLC kinase and the brain PKC epsilon catalytic fragment were similar as indicated by the relative sizes of the PKC epsilon immunoreactive peptides generated with protease V8 from Staphylococcus aureus (Mr approximately 37,000, 34,000, 28,000, 26,000, and 25,000). Taken together, we conclude that a variant SCLC cell line expresses a constitutively active catalytic fragment of PKC epsilon. Regulation by 12-O-tetradecanoyl-13-acetate or GRP via de novo protein synthesis suggests a novel mechanism of control of PKC diversity with implications for small cell lung cancer and possibly other malignancies.

Amino Acid Sequence↗
PubMed1992

Characterization of functional receptors for gastrointestinal hormones on human colon cancer cells.

Studies demonstrate that some colon cancers possess receptors for various gastrointestinal hormones or neurotransmitters, the occupation of which can affect growth. These results are limited because frequently only a small number of tumors are studied, only 1 or 2 receptors are sought, and the effect on cell function is not investigated. In the present study, 10 recently characterized human colon cancer cell lines were studied to determine whether they possess receptors for any of 12 different gastrointestinal hormones or neurotransmitters and to determine whether these receptors mediate changes in cellular function. Each of the cell lines exhibited receptors for at least one radioligand. Receptors for vasoactive intestinal peptide (VIP) and muscarinic cholinergic agents occurred on 60%, bombesin and gastrin on 30%, beta-adrenergic agents and gastrin-releasing peptide (GRP) on 20%, and somatostatin, opiates, neuromedin B, and substance P on 10%. Analysis of [3H]N-methylscopolamine binding revealed a Kd of 0.2 nM for N-methylscopolamine with a binding capacity of 2500 sites/cell. With the agonist carbamylcholine, the receptor exhibited 2 classes of binding sites: one of high affinity (Kd 55 microM) representing 75% of the binding sites and one of low affinity (Kd 0.3 mM) representing 25% of the binding sites. Analysis of 125I-[Tyr4]bombesin binding revealed a receptor of high affinity (Kd 2.1 microM) with a binding capacity of 3300 sites/cell. Inhibition of binding by agonists revealed relative potencies of 125I-[Tyr4]bombesin greater than GRP much greater than neuromedin B, and two recently described antagonists were similar in potency to GRP. Analysis of 125I-VIP binding revealed a receptor having 2 classes of binding sites: one of high affinity (Kd 3.6 nM) and one of low affinity (Kd 1.7 microM) which represented the majority of the 5.5 x 10(6) binding sites/cell. The relative potencies of agonists were VIP greater than helodermin greater than peptide histidine methionine greater than secretin. Evaluation of biological activity mediated by the muscarinic cholinergic and bombesin receptors revealed an increase of intracellular calcium and of inositol triphosphate by specific receptor agonists. The presence or absence of receptors detected by binding correlated closely with the ability of selective receptor agonists to alter cell function. These results demonstrate the presence of several different receptors for gastrointestinal hormones or neurotransmitters, some described for the first time, on human colon cancer cell lines, including bombesin-related peptides, VIP, somatostatin, substance P, beta-adrenergic agents, calcitonin gene-related peptide, gastrin, muscarinic cholinergic agents, and opiates.(ABSTRACT TRUNCATED AT 400 WORDS)

Bombesin↗
PubMed1992

[Physiological analyses of secretory kinetics of adrenocorticotropic hormone (ACTH) from anterior pituitary cells: development and application of a microperfusion system].

A microperfusion system was developed to study detailed kinetics of adrenocorticotropic hormone (ACTH) secretion by dispersed rat anterior pituitary cells responding to various ACTH secretagogues. The system approaches hydrodynamics to square-wave stimuli and enables kinetic analysis of ACTH secretion with intervals as short as 5 sec. ACTH secretion initiated within 5 sec of exposure of the cells to corticotropin-releasing factor (CRF), arginine vasopressin (AVP), oxytocin (OT) or angiotensin II (A-II) and reached a maximum within 20-40 sec. CRF induced a plateau-shaped secretion of ACTH which remained constant as long as CRF was perifused. In contrast, the ACTH secretion responding to AVP, OT and A-II rose rapidly to a peak and fell to the baseline despite continued perifusion of these agents. There were two components of ACTH secretory response to AVP and OT. AVP had synergistic effect with CRF only if it was perifused simultaneously with CRF or immediately after CRF was stopped. The ACTH secretory response to A-II was greatly diminished when cells were exposed to AVP or OT before A-II perifusion. Prior exposure to A-II had no effect on the magnitude of the ACTH secretory response to either AVP or OT. Epinephrine, nor-epinephrine, gastrin-releasing peptide, atrial natriuretic factor and cholecystokinin stimulated no significant ACTH secretion in the microperfusion system, although some of them induced ACTH secretion by same cell preparation in static culture systems.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗
PubMed1992

Pre- and postoperative sequential study on the serum gastrin level in patients with lung cancer.

Serial changes in serum gastrin level were detected by radioimmunoassay in 58 lung cancer patients before and after operation. In comparing these tests with those of 40 cases of noncancerous thoracic lesions and 151 normal adults, the serum gastrin from lung cancer patients is significantly higher than that of noncancerous thoracic lesions and normal individuals (P less than 0.01). The gastrin level is closely related to stage of cancer, size of primary tumor, presence of lymph node metastasis, and type of histological classification. The serum gastrin was found to decrease gradually after the removal of the tumor and to return to normal on the 14th postoperative day. Those patients whose serum gastrin level can return to normal on the 14th postoperative day will have a good prognosis; if not, their prognosis will be very poor. These results suggest that serum from patients with lung cancer contains a high concentration of gastrin that can help differentiate benign from malignant thoracic lesions and evaluate prognosis of patients with lung cancer. Therefore, the cause of high serum gastrin in patients with lung cancer is likely due to the gastrin-producing property of the lung cancer cells.

Adenocarcinoma↗
PubMed1992

Increased expression of differentiation markers can accompany laminin-induced attachment of small cell lung cancer cells.

We investigated the interaction between human lung cancer cells, laminin, and several differentiating agents. When grown on laminin coated substrate eight out of 11 small cell lung cancer (SCLC) cell lines exhibited attachment to laminin and three had extensive outgrowth of long neurite-like processes. Of seven non-small cell lung cancer cell lines, selected for their in vitro anchorage-independent growth, attachment was observed in only three cell lines, and process formation was far less extensive than in SCLC cell lines. Among several differentiating agents, only dcAMP, which alone induced attachment and some process formation, increased laminin-mediated attachment and process formation of two SCLC cell lines, NCI-N417 a variant cell line, and NCI-H345, a classic cell line. The expression of several neuroendocrine and neuronal markers was investigated in these two SCLC cell lines. The expression of the light subunit of neurofilaments increased in NCI-N417 within 3 to 4 days of seeding, while NCI-H345 exhibited approximately 5 fold increase in expression of the GRP gene and a 3 fold increase expression of the beta-actin gene. The expression of a number of other neuroendocrine and neuronal markers did not change following growth on laminin. The doubling times remained unchanged independent of the presence of and attachment to laminin while topoisomerase II gene expression levels in NCI-N417 cells decreased approximately 5 fold when cells were growing on laminin.

Acetamides↗