Secretin receptors in human pancreatic membranes

Crude membranes (27,000 g pellets) from five normal human pancreases were prepared. In the presence of GTP, the peptides of the secretin family stimulated adenylate cyclase activity, their order of potency being: secretin greater than helodermin greater than peptide histidine isoleucinamide (PHI) greater than or equal to vasoactive intestinal peptide (VIP) greater than growth hormone releasing factor (GRF) (1-29)-NH2. In addition, helodermin and PHI were more efficient than secretin. Secretin (3-27) inhibited fully the secretin stimulation and partially only the helodermin and PHI stimulation of the enzyme. Secretin receptors were investigated by the ability of secretin and related peptides to inhibit tracer binding. [125I]Secretin binding was fully inhibited by secretin (Kd 0.8 nM), helodermin (Kd 200 nM), and PHI (Kd 250 nM). VIP and GRF(1-29)-NH2 induced partial (20%) inhibition at a high 10 microM concentration. The fragments secretin (2-27), (3-27), (4-27), and (7-27) showed the same low potency and efficacy based on their ability to stimulate adenylate cyclase and to occupy secretin receptors. The analogues [Val5]secretin and [Ala2]secretin had a higher potency than secretin. Based on this comparison of adenylate cyclase stimulation and [125I]secretin binding inhibition, it is tempting to conclude that the human pancreas: (a) possesses highly specific secretin receptors and (b) such receptors could not fully account for the whole pattern of adenylate cyclase activation by related peptides, so that the presence of an added type of "helodermin-PHI-preferring" receptors is suggested.     

Effect of GHRH and peptides from the vasoactive intestinal peptide family on cAMP production of human cancer cell lines in vitro.

Antagonistic analogs of GHRH inhibit growth of various human cancers both in vivo and in vitro. To elucidate the mechanism of direct action of the antagonistic analogs of GHRH on tumor cells, cultured human cancer cells were exposed to GHRH, vasoactive intestinal peptide (VIP), secretin, glucagon, neuropeptide-Y (NPY), pituitary adenylate cyclase-activating peptide (PACAP), and VIP analogs in a superfusion system, and changes in cAMP and IGF-II release from the cells were measured. Various human cancer cell lines, such as mammary (MDAMB-468 and ZR-75-1), prostatic (PC-3), pancreatic (SW-1990 and Capan-2), ovarian (OV-1063), and colorectal (LoVo) responded to pulsatile stimuli with GHRH (0.5-20 nM), VIP (0.02-10 nM), and PACAP-38 (0.05-5 nM) with a rapid, transient increase in cAMP release from the cells. The VIP antagonist, PG-97-269, and the adenylate cyclase inhibitor, MDL-12330A, but not SQ-22536 or pertussis toxin, blocked the cAMP responses to these peptides. Stimulation of the cells with 100 nM secretin, glucagon or NPY did not alter the cAMP release. Our results suggest that GHRH receptors different from the type expressed in the pituitary are involved in mediating these effects. As cAMP is a potent second messenger controlling a wide variety of intracellular functions, including those required for cell growth, our results indicate that GHRH might have a direct stimulatory effect on growth of human cancers. Blockade of the autocrine/paracrine action of GHRH with its antagonistic analogs may provide a new approach to tumor control.     

Characterization of secretin and vasoactive intestinal peptide receptors in rat pancreatic plasma membranes using the native peptides, secretin-(7-27) and five secretin analogues

A comparison has been made of the ability of vasoactive intestinal peptide (VIP), secretin, secretin analogues, and secretin-(7-27) to stimulate adenylate cyclase in rat pancreatic plasma membranes. A parallel study of the capacity of peptides of the VIP-secretin family to compete with 125I-VIP for binding to the same plasma membranes was conducted. This allowed a classification of VIP-secretin receptors into three subtypes: (1) VIP-preferring receptors; (2) high-affinity secretin receptors, and (3) low-affinity secretin receptors. The properties of secretin at high-affinity secretin receptors were likely to reflect a contribution of membranes from centroacinar and duct cells.     

The tobacco-specific carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone stimulates proliferation of immortalized human pancreatic duct epithelia through β-adrenergic transactivation of EGF receptors

Purpose: Pancreatic ductal adenocarcinoma is an aggressive smoking-associated human cancer in both men and women. The nicotine-derived 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is thought to contribute to the development of these neoplasms in smokers through genotoxic effects. However, NNK has been recently identified as an agonist for both β₁- and β₂-adrenergic receptors. Binding of NNK to these receptors stimulates proliferation of pulmonary and pancreatic adenocarcinomas cells in vitro and in hamster models. The goal of this study was to elucidate the NNK effects on the signal transduction pathways downstream of both β₁- and β₂-adrenergic receptors in immortalized human pancreatic HPDE6-c7 cells. Methods: The HPDE6-c7 cells are developed from normal pancreatic duct epithelial cells which are the putative cells of origin of pancreatic ductal adenocarcinoma. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazoliumbromide (MTT) cell proliferation assays, Western blot and cyclic AMP assays were employed to demonstrate the effects of NNK and other β₁- and β₂-adrenergic agonists and antagonist treatments on these cells. Results: MTT cell proliferation assays demonstrated that NNK and the classic β-adrenergic agonist, isoproterenol, increased cell proliferation in HPDE6-c7 cells. Western blot and cyclic AMP assays demonstrated that NNK treatments also resulted in: (1) transactivation of the epidermal growth factor receptor, EGFR, (2) an increase in intracellular cyclic AMP accumulation, and (3) phosphorylation of mitogen-activated protein kinase, Erk1/2. The proliferative response to NNK and isoproterenol were inhibited by the use of beta-blockers (propranolol), and the inhibitors of adenylyl cyclase (SQ 22536), EGFR-specific tyrosine kinase (AG 1478) and Erk (PD 98059). Conclusion: These findings suggest that the NNK -mediated β-adrenergic receptor transactivation of the EGFR and phosphorylation of Erk1/2 in immortalized human pancreatic duct epithelial cells as a novel mechanism might contribute to the development of tobacco-associated pancreatic carcinogenesis.     

花姜酮对胰腺癌细胞迁移和侵袭的影响及机制的研究

目的:探讨花姜酮(zerumbone)对人胰腺癌细胞株BxPC-3和Panc-1迁移和侵袭的影响及其相关基因的表达。方法:以BxPC-3和Panc-1为研究对象,通过四甲基偶氮唑盐(MTT)实验选择毒性较小的花姜酮浓度,用细胞划痕实验、Transwell小室迁移和侵袭实验检测药物对细胞迁移和侵袭能力的影响,蛋白质印迹(Western blot)检测各细胞组CXC族趋化因子受体4(CXCR4)、促分裂原活化蛋白酶激酶1/2(MEK1/2)、磷酸化MEK 1/2(p-MEK1/2)、细胞外调节激酶1/2(ERK1/2)、磷酸化ERK1/2(p-ERK1/2)蛋白表达变化。结果:花姜酮对BxPC-3和Panc-1细胞的生长均有抑制作用,且随着药物浓度的增高和作用时间的延长而增强(P<0.05)。低浓度药物作用后BxPC-3和Panc-1的划痕迁移率都低于对照组(P<0.05)。与对照组相比,Transwell迁移和侵袭实验中BxPC-3和Panc-1用药组的平均穿膜细胞数均减少(P     

Catecholamine-sensitive adenylate cyclase of human fat cell ghosts: a comparative study using different beta-adrenergic agents.

Some of the effects of beta-adrenergic agonists and antagonists on the adenylate cyclase system of human fat cell ghosts were studied. Isoproterenol, by causing about a fourfold increase of enzyme activity, was more potent than epinephrine and norepinephrine (about 2.5--3.0-fold stimulation). The beta2-adrenergic agonists salbutamol, terbutalin, and fenoterol were considerably less effective than the naturally occurring catecholamines. The stimulatory actions of isoproterenol and beta2-adrenergic agonists were competitively inhibited by the beta-blocking agent propranolol. Isoproterenol stimulation was also inhibited by the selective beta1-adrenergic antagonist practolol. This compound, however, was less potent than propranolol. The results are suggestive for an adenylate cyclase system in human fat cell ghosts coupled to beta1-adrenergic receptor sites. These receptors differ from the cardiac beta receptors with respect to practolol affinity.     

Gene expression analysis of pancreatic cell lines reveals genes overexpressed in pancreatic cancer.

BACKGROUND: Pancreatic cancer is one of the leading causes of cancer-related death. Using DNA gene expression analysis based on a custom made Affymetrix cancer array, we investigated the expression pattern of both primary and established pancreatic carcinoma cell lines. METHODS: We analyzed the gene expression of 5 established pancreatic cancer cell lines (AsPC-1, BxPC-3, Capan-1, Capan-2 and HPAF II) and 5 primary isolates, 1 of them derived from benign pancreatic duct cells. RESULTS: Out of 1,540 genes which were expressed in at least 3 experiments, we found 122 genes upregulated and 18 downregulated in tumor cell lines compared to benign cells with a fold change >3. Several of the upregulated genes (like Prefoldin 5, ADAM9 and E-cadherin) have been associated with pancreatic cancer before. The other differentially regulated genes, however, play a so far unknown role in the course of human pancreatic carcinoma. By means of immunohistochemistry we could show that thymosin beta-10 (TMSB10), upregulated in tumor cell lines, is expressed in human pancreatic carcinoma, but not in non-neoplastic pancreatic tissue, suggesting a role for TMSB10 in the carcinogenesis of pancreatic carcinoma. CONCLUSION: Using gene expression profiling of pancreatic cell lines we were able to identify genes differentially expressed in pancreatic adenocarcinoma, which might contribute to pancreatic cancer development.     

Receptors for vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide in turkey cerebral cortex: characterization by [125I]-VIP binding and effects on cyclic AMP synthesis

Receptors for vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) in turkey cerebral cortex were characterized using two approaches: (1) in vitro radioreceptor binding of [125I]-VIP, and (2) effects of peptides from the PACAP/VIP/secretin family on cyclic AMP formation. The binding of [125I]-VIP to turkey cortical membranes was rapid, stable, and reversible. Saturation analysis resulted in a linear Scatchard plot, suggesting binding to a single class of high affinity receptor binding sites with a Kd of 0.70 nM and a Bmax of 52 fmol/mg protein. Various peptides displaced the specific binding of 0.12 nM [125I]-VIP to turkey cerebral cortical membranes in a concentration-dependent manner. The relative rank order of potency of the tested peptides to inhibit [125I]-VIP binding to turkey cerebrum was: PACAP38 approximately PACAP27 approximately chicken VIP approximately mammalian VIP > PHI > secretin, chicken VIP16-28 (inactive). About 65% of specific [125I]-VIP binding sites in turkey cerebral cortex was sensitive to Gpp(NH)p, a nonhydrolysable analogue of GTP. PACAP38, PACAP27, chicken VIP and, to a lesser extent, mammalian VIP potently stimulated cyclic AMP formation in turkey cerebral cortical slices in a concentration-dependent manner, displaying EC50 values of 8.7 nM (PACAP38), 21.3 nM (PACAP27), 67.4 nM (chicken VIP), and 202 nM (mammalian VIP). On the other hand, PHI and secretin very weakly affected the nucleotide production. The obtained results indicate that cerebral cortex of turkey contains VPAC type receptors that are positively linked to cyclic AMP-generating system and are labeled with [125I]-VIP.     

GnRH agonist-induced inhibitory and stimulatory effects during ovarian follicular maturation

The in vivo regulation of ovarian gonadotropin and prolactin receptors and adenylate cyclase activity by FSH, and the potent GnRH agonist [D-Ala⁶]des-Gly¹⁰-GnRH N-ethylamide (GnRHa), was studied in immature hypophysectomized diethylstilbestrol-implanted rats. During FSH treatment over a 48 h period, FSH receptors increased 2-fold with the maximum response during the first 12 h, whereas LH and prolactin receptors increased by 10-fold and 6-fold with the maximum response from 12 to 48 h. Administration of GnRHa at any time during the 48 h period of FSH treatment inhibited the subsequent development of gonadotropin and PRL receptors. In contrast, administration of a single dose of 10 μg GnRHa after 48 h of FSH treatment stimulated follicular luteinization and caused increases in basal adenylate cyclase activity, ovarian weight and PRL receptor content, and concomitant decreases in gonadotropin receptors and adenylate cyclase responses. In the immature follicles of animals not primed with FSH, GnRHa caused progressive inhibition of FSH-sensitive adenylate cyclase activity, with a decrease in FSH receptors, but increased both basal and GMP-P(NH)P-stimulated adenylate cyclase activities. These results demonstrate that GnRHa causes marked inhibition of gonadotropin receptor expression in the basal and FSH-stimulated ovary. This decrease in gonadotropin receptors is an important component of the mechanism by which GnRH agonists inhibit ovarian gonadotropin-sensitive adenylate cyclase activity. In addition, these peptides exert stimulatory effects upon ovarian weight and basal adenylate cyclase activity, and cause an increase in PRL receptors and luteinization of mature ovarian follicles. The stimulatory actions of GnRH agonists upon ovarian function are more prominent with increasing maturation of the granulosa cell.     

Properties of a recombinant human secretin receptor: a comparison with the rat and rabbit receptors.

A secretin receptor was cloned from a commercial human pancreatic complementary DNA (cDNA) bank. The amino acid sequence deduced from the nucleotide sequence differed slightly from the three different sequences previously published, suggesting a genetic polymorphism of the human receptor. The binding properties of the receptor were evaluated by testing natural secretin, related peptides, and synthetic analogs or fragments on membranes of Chinese hamster ovary (CHO) cells expressing the receptor after transfection. The second-messenger coupling was evaluated by adenylate cyclase measurement. The human secretin receptor was compared with the rat and the rabbit receptors. In the three animals species, rat and human secretin were equipotent; rabbit secretin was equipotent on human and rabbit secretin receptors and less potent on the rat receptor. Similar data were obtained for the [Arg16]-secretin analog. Deletion of histidine 1 and replacement of aspartate 3 reduced the affinity of the peptides for the three receptors; however, the reduction was more pronounced on rat than on human and rabbit secretin receptors. Finally, the low affinity of the rat and human receptors for vasoactive intestinal peptide (VIP) was identical; the rabbit receptor, however, had a 20-fold higher affinity. Thus the human secretin receptor shows properties of both rat and rabbit receptors. Evaluation of the properties of chimeric receptors will be useful to fit the ligand on the receptors.     

Regulation by vasoactive intestinal peptide, histamine, somatostatin-14 and -28 of cyclic adenosine monophosphate levels in gastric glands isolated from the guinea pig fundus or antrum

Studies were conducted to explore the effects of vasoactive intestinal peptide (VIP), histamine, somatostatin-14 and -28 (S-14 and S-28), and prostaglandin E2 (PGE2) on cAMP production in gastric glands isolated from the guinea pig. VIP (EC50 = 5 X 10(-10) M) and PGE2 (EC50 = 10(-8) M) induced cAMP accumulation in glands isolated by means of EDTA from the fundus or antrum. The structurally related peptides PHI (peptide with N-terminal histidine and C-terminal isoleucine amide) and secretin also increased cAMP production in the system, but with 200 to 2000 times lower potencies than VIP. Combinations of VIP with PHI or secretin do not produce additive stimulation, indicating that PHI or secretin interact with the receptor-cAMP system highly sensitive to VIP. Histamine was about 10 times more potent in fundus (EC50 = 10(-5) M) than in antrum (EC50 = 9 X 10(-5) M) and did not produce any stimulation in enterocytes isolated from the upper part of the duodenum. Complete inhibitions caused by the H2 receptor antagonist cimetidine (Ki = 0.15-0.16 X 10(-6) M) (Ki is the inhibition constant) or by the H1 receptor antagonist diphenhydramine (DPH) (Ki = 13-17 X 10(-6) M) indicate that H interacts with typical H2 receptors mediating adenylate cyclase activation in fundic (Ka = 10(-5) M) (Ka is the association constant) or antral membranes (Ka = 3 X 10(-5) M). In fundus, S-14 inhibited partially (about 60%) cAMP production evoked by H or by its H1 or H2 agonists. The kinetics and the inhibitory potencies (2 X 10(-8) M) or efficacies of S-14 and -28 were identical. No effect of S-14 was found on basal or on cAMP production induced by VIP or PGE2 in either fundic or antral glands or by H in antral glands. The results support the hypothesis of a regulatory role for VIP and/or secretin in mucous and/or peptic secretions via a cAMP-dependent mechanism in gastric mucosa in mammals. Second, we propose that S-14 as well as S-28 may inhibit gastric acid secretion by a direct and selective control of H-induced cAMP production in parietal cells, through a common recognition site (receptor?) distinct from the H2 receptor. Third, not only parietal cells, but also nonparietal cells of the antrum possess an H2 receptor-cAMP system. This finding could be related to the in vivo regulation by cimetidine of endocrine (somatostatin) and exocrine (pepsin) secretions by the stomach.     

Human pancreatic adenocarcinomas express parathyroid hormone-related protein

PTH-related protein (PTHrP) is expressed in many common malignancies such as breast and prostate cancer and can regulate their growth. Little is known, however, about the role of PTHrP in pancreatic adenocarcinoma. To study PTHrP in pancreatic exocrine cancer, we studied its expression in pancreatic cancer cell lines and surgical specimens. Eight human pancreatic adenocarcinoma cell lines were evaluated: AsPC-1, BxPC-3, Capan-1, CFPAC-1, MIA PaCa-2, PANC-1, PANC-28, and PANC-48. Murine monoclonal antibodies to the amino-terminal (1-34), mid-region (38-64), and carboxyl-terminal peptides (109-141) of PTHrP were used to identify cellular PTHrP and secreted PTHrP, including Western blotting and immunocytochemical staining for PTHrP from each cell line. Cellular PTHrP was detected in all cell line extracts by both Western blotting and immunoassay. CFPAC-1, derived from a pancreatic liver metastasis, had the highest concentration of PTHrP, and MIA PaCa-2, derived from primary pancreatic adenocarcinoma, had the lowest. PTHrP was localized by immunocytochemical staining in the cytoplasm in all but one cell line, and both nuclear and cytoplasmic immunostaining were observed in the MIA PaCa-2 and PANC-1 cells. Secretion of PTHrP into cell medium was also observed for each cell line and paralleled intracellular PTHrP levels. Evidence for differential processing of PTHrP expression was provided by studies demonstrating different patterns of PTHrP among the cell lines when assessed by PTHrP immunoassays directed against different PTHrP peptides. In specific, PTHrP secretion measured by a PTHrP-(38-64) assay was highest for BxPC-3, whereas the highest levels of secreted PTHrP-(109-141) occurred in CFPAC-1 and PANC-1. Growth of AsPC-1 cells was stimulated in a dose-dependent manner by PTHrP-(1-34). Immunostaining from archival tissue of patients with pancreatic adenocarcinoma revealed strong PTHrP expression in all 14 specimens. All patients were eucalcemic preoperatively. These results demonstrate that PTHrP is commonly expressed in pancreatic cancer. Our data suggest that PTHrP may have growth-regulating properties in pancreatic adenocarcinoma cells, but further studies are required.     

Growth and function of isolated canine pancreatic ductal cells

These studies investigated the growth characteristics and functional properties of isolated canine pancreatic ductal epithelial cells. Cells were isolated from the accessory pancreatic duct and cultured by using three conditions: on vitrogen-coated petri dishes with fibroblast conditioned medium (nonpolarized); in vitrogen-coated Transwells above a fibroblast feeder layer (polarized); or as organotypic rafts above a fibroblast-embedded collagen layer (polarized). Growth characteristics, transepithelial resistances, and carbonic anhydrase and cyclic adenosine monophosphate (AMP) responses were evaluated. Under polarized conditions, the cells grew as monolayers with columnar epithelial characteristics. The monolayers developed high transepithelial resistance and became impervious to the passage of horseradish peroxidase. Epithelial growth factor (EGF) (2 ng/ml) stimulated ductal cell growth and accelerated the formation of a high-resistance monolayer. Forskolin (10 microM) rapidly decreased transepithelial resistance. Carbonic anhydrase activity, which was lower in nonpolarized compared with polarized conditions, was stimulated by carbachol (175 microM). Secretin, however, did not stimulate carbonic anhydrase activity in these cells. Although secretin stimulated adenylyl cyclase activity in early-passage cells, this response was lost in later-passage cells. Both vasoactive intestinal polypeptide (VIP; 1 microM) and forskolin (10 microM) consistently increased adenylyl cyclase activity. Isolated canine pancreatic ductal epithelial cells proliferate in vitro, develop high-resistance epithelial monolayers, and respond to stimuli that activate adenylyl cyclase. These cells should provide a useful model for regulatory studies of ductal cell functions.     

Insights into erlotinib action in pancreatic cancer cells using a combined experimental and mathematical approach

AIM:To gain insights into the molecular action of erlotinib in pancreatic cancer (PC) cells. METHODS:Two PC cell lines, BxPC-3 and Capan-1, were treated with various concentrations of erlotinib, the specific mitogen-activated protein kinase kinase (MEK) inhibitor U0126, and protein kinase B (AKT) inhibitor XIV. DNA synthesis was measured by 5-bromo-2'-deoxyuridine (BrdU) assays. Expression and phosphorylation of the epidermal growth factor receptor (EGFR) and downstream signaling molecules were quantified by Western blot analysis. The data were processed to calibrate a mathematical model, based on ordinary differential equations, describing the EGFRmediated signal transduction. RESULTS:Erlotinib significantly inhibited BrdU incorporation in BxPC-3 cells at a concentration of 1 mol/L, whereas Capan-1 cells were much more resistant. In both cell lines, MEK inhibitor U0126 and erlotinib attenuated DNA synthesis in a cumulative manner, whereas the AKT pathway-specific inhibitor did not enhance the effects of erlotinib. While basal phosphorylation of EGFR and extracellular signal-regulated kinase (ERK) did not differ much between the two cell lines, BxPC-3 cells displayed a more than five-times higher basal phospho-AKT level than Capan-1 cells. Epidermal growth factor (EGF) at 10 ng/mL induced the phosphorylation of EGFR, AKT and ERK in both cell lines with similar kinetics. In BxPC-3 cells, higher levels of phospho-AKT and phospho-ERK (normalized to the total protein levels) were observed. Independent of the cell line, erlotinib efficiently inhibited phosphorylation of EGFR, AKT and ERK. The mathematical model successfully simulated the experimental findings and provided predictions regarding phosphoprotein levels that could be verified experimentally. CONCLUSION:Our data suggest basal AKT phosphorylation and the degree of EGF-induced activation of AKT and ERK as molecular determinants of erlotinib efficiency in PC cells.     

Identification of Genomic Alterations Associated with the Aggressiveness of Pancreatic Cancer Using an Ultra-High-Resolution CGH Array

Background: Genomic alterations present in pancreatic adenocarcinoma have been described only partially. In addition, the relations between these alterations and the aggressiveness of the phenotype remain unknown. Methods: Genomic DNA and total RNA from 5 pancreatic cell lines, of which 2 have an aggressive phenotype and are gemcitabine-resistant (Mia-Paca2 and Panc-1), and 3 less aggressive and gemcitabine-sensitive (Capan-1, Capan-2 and BxPC3), have been purified. DNA abnormalities have been analyzed using an ultra-high-resolution CGH array and mRNA expression was studied with an Affymetrix GeneChip expression array. Results: We identified 573 amplified and 30 deleted genes common to all 5 cell lines. Some of them have already been described, whereas other genes, implicated in signal transduction, apoptosis, cell cycle or cell migration, are described for the first time as being related to this cancer. Comparison of genomic abnormalities between the 2 most aggressive and the 3 less aggressive cell lines led to the identification of 368 genes specifically amplified in the aggressive cell lines. However, no specific gene deletion seems to be associated with the aggressive phenotype. Conclusion: Using a high-resolution approach, we could precisely describe the genomic alterations associated with pancreatic adenocarcinoma and determine those associated with an aggressive phenotype.     

Dissociated insulin and islet amyloid polypeptide secretion from isolated rat pancreatic islets cocultured with human pancreatic adenocarcinoma cells

Abnormal insulin and islet amyloid polypeptide (IAPP) secretion are usually seen in patients with exocrine pancreatic cancer. The beta-cell dysfunction is a characteristic of the glucose intolerance found in pancreatic cancer patients. The effects of pancreatic cancer cells on insulin and IAPP secretion from beta cells are unclear. In this study, isolated rat pancreatic islets were cocultured with two human pancreatic adenocarcinoma cell lines (Panc-1 and HPAF) and a human colonic adenocarcinoma cell line (HT-29). As a control, islets were incubated in the absence of malignant cells. The accumulation of insulin and IAPP in culture media was measured by radioimmunoassay. Output of insulin and IAPP was decreased in islets cocultured with each malignant cell line. Molar ratio of secreted IAPP and insulin (IAPP/insulin) was increased in the islets cocultured with Panc-1 or HPAF cells, but not HT-29 cells. The decreased insulin and IAPP secretion were partly recovered after Panc-1, HPAF, or HT-29 cells were removed. The IAPP/insulin ratio was normalized after the removal of Panc-1 or HPAF cells. This study indicates that insulin and IAPP secretion are altered by the human adenocarcinoma cells investigated. The impairment induced by pancreatic adenocarcinoma cells is associated with a hypersecretion of IAPP relative to insulin on a molar basis.