VIP regulation of a human pancreatic cancer cell line: Capan-1

Gastrointestinal hormones as potential adjuvant treatment of exocrine pancreatic adenocarcinoma

CONCLUSION

Gastrointestinal hormones and their antagonists can alter the growth of pancreatic adenocarcinoma in vitro and in vivo. The potential clinical benefit of this approach deserves further study.

BACKGROUND

Epithelial cell growth is normally under hormonal control. Hormones also affect the growth of many epithelial cancers, and this fact is used to modify tumor growth. Pancreatic epithelial cell growth is under the influence of gastrointestinal hormones. This article reviews experiments designed to determine the effect of gastrointestinal hormones on the growth of pancreatic adenocarcinoma.

METHODS

Eighty-eight articles were identified from a Medline search using the terms pancreatic adenocarcinoma and the individual names of gastrointestinal hormones. The experimental design and results of these studies are reviewed.

RESULTS

In general, somatostatin, vasoactive intestinal polypeptide, pancreatic polypeptide, and pancreastatin inhibit pancreatic adenocarcinoma growth. Cholecystokinin, secretin, bombesin, gastrin, EGF, TGF-alpha, insulin, and IGF-1 have a growth-promoting effect.

AR4-2J cells: a model to study polypeptide hormone receptors

The AR4-2J cell line is derived from a transplantable tumour of the exocrine rat pancreas. Acinar in origin, this cell line contains significant amounts of amylase and can be grown in continuous culture. Many in vitro studies have been done using these cells; these studies were often complemented with in vivo experiments on animals. Particularly, many polypeptide hormones interacting with specific receptors located on the cell membrane have been analysed. The accurate knowledge of the hormone-receptor interactions has allowed to design interesting analogs of these hormones. In several cases, these compounds are powerful antagonists and are able to control cell proliferation induced by the corresponding polypeptide hormones. Other cell lines are useful to understand human pancreatic cancer. These human cell lines (Capan 1, Panc-1 for example) are of ductal origin and differ from AR4-2J cells, especially regarding the distribution of several polypeptide hormone and growth factor receptors. Both models are important for basic studies of neuropeptides, gastrointestinal peptides and their receptors, as well as for a better understanding of the underlying mechanisms of human pancreatic cancer.

Adenylate cyclase activity in human pancreatic adenocarcinoma cell lines

CONCLUSION

BxPC-3, Hs 766T, Capan-2, Panc-1, and Capan-1 cells possess receptors for VIP and beta-adrenergic agonists that are functionally coupled to adenylate cyclase. In this respect, they resemble pancreatic duct cells. However, we speculate that the process of neoplastic transformation has either downregulated the expression of secretin receptors or led to a defect in the receptor itself, placing a question mark over the usefulness of these adenocarcinoma cell lines as models of the pancreatic ductal epithelium

BACKGROUND

Because of the importance of ducts in pancreatic disease, we wished to establish which duct cells receptors are functional on adenocarcinoma cell lines.

METHODS

We investigated the expression of agonist-stimulated adenylate cyclase activity in six human pancreatic adenocarcinoma cell lines. Known stimulants of pancreatic ductal secretion, VIP, PHI, secretin, beta-adrenergic, and dopamine, were tested.

RESULTS

For responsive cell lines, VIP was the most effective stimulant followed by adrenaline, isoprenaline, PHI, and secretin. Dopamine was without effect. Since high concentrations of PHI and secretin were required to stimulate cyclase activity, their effect is probably mediated by VIP receptors. Based on the degree of stimulation observed with the individual agonist, Hs 766T and BxPC-3 were the most responsive cell lines, followed by Capan-2 and Capan-1, and finally Panc-1. MIAPaCa-2 cells did not respond to any of the agonists tested.

Differential expression of VIP/PACAP receptor genes in breast, intestinal, and pancreatic cell lines

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating peptide (PACAP) are structurally-related neuropeptides that function as trophic factors in addition to their more classical roles as neurotransmitters. Binding and molecular cloning studies have shown that their actions are mediated by receptors encoded by at least three different genes. VIP binding has been demonstrated on many tumor types, and radiolabeled VIP has recently been used as a novel method to localize intestinal tumors in humans and their sites of metastasis. To determine the receptor subtype and level of gene expression, we screened breast, intestinal, and pancreatic, cell lines by Northern blot analysis. Breast lines expressed VIP/PACAP1 receptor mRNA levels comparable to intestinal lines, in agreement with the studies showing particularly high VIP binding in these tumors and their derived cell lines. Pancreatic cell lines expressed mRNA for several receptor types. This extends the potential utility of VIP and PACAP in the localization of tumors, and because VIP and PACAP may regulate the growth rate of some tumors by autocrine or other mechanisms, the identification of receptor subtypes on these lines sets the stage for studies in which the activity of these individual receptors in growth and other processes can be investigated.

Effects of VIP on the regulation of mucin secretion in cultured human pancreatic cancer cells (Capan-1)

The effects of Vasoactive intestinal peptide (VIP) on mucin secretion in the pancreatic cancer Capan-1 cell line were studied by Enzyme-linked-immunosorbent-assay (ELISA), and by light and electron microscopy using immunocytological methods. During the exponential growth phase, mucins were accumulated in the cytoplasm of cells and slowly exocytosed. In contrast, there was enhanced exocytosis of mucins during the stationary phase when the cells were well-polarized. Moreover, during this phase, VIP induced a dose-dependent rise in mucin content in the extracellular medium. The reaction with anti-M1 monoclonal antibodies, which recognize specifically the peptide core of gastric mucins, showed an accumulation of secretion granules near the apex of well-polarized cells together with fusion of the granule and plasma membranes after VIP stimulation. Moreover, mucin exocytosis was stimulated by Pituitary adenylate cyclase activating polypeptide (PACAP) and secretin. It was also increased after forskolin treatment suggesting that this mechanism was cAMP-dependent. Our results suggested that exocytosis of mucins could be under the control of VIP in pancreatic duct cells of the Capan-1 cell line.

Molecular cloning and functional characterization of a human liver vasoactive intestinal peptide receptor

We have isolated a cDNA from a human liver library which is 2349 base pairs in length and encodes a near-full length seven transmembrane receptor (432 amino acids), 85% homologous to the amino acid sequence for the rat vasoactive intestinal peptide (VIP) receptor. Northern blot analysis identifies a major species at 3.3 kb in lung, and to a lesser extent in brain, heart and liver. In order to confirm the identity of this human clone, double-stranded oligonucleotides encoding the signal peptide of the rat VIP receptor were constructed by polymerase chain reaction and attached to the 5' end of the human clone. COS cells transiently transfected with this human VIP receptor chimera, express a single binding site for 125I-VIP with a Kd of 9.2 +/- 2 nM. Related peptides displace 125I-VIP with a relative potency of VIP = PACAP > helodermin >> PHM > secretin, which is similar to the binding profile seen in human tissues. This human chimeric receptor is functionally coupled to the stimulation of adenylyl cyclase in transfected COS cells, as evidenced by a dose-dependent increase in intracellular cAMP accumulation. These studies indicate that this cDNA encodes a human liver VIP receptor which is functionally coupled to the activation of adenylyl cyclase.

Phosphorylation-regulated low-conductance Cl- channels in a human pancreatic duct cell line

A low-conductance Cl- channel has been identified in the apical membrane of the human pancreatic duct cell Capan-1 using patch-clamp techniques. Cell-attached channels were activated by the vasoactive intestinal polypeptide (VIP, 0.1 mumol/l), dibutyryl-adenosine 3',5'-cyclic monophosphate (db-cAMP, 1 mmol/l), 8-bromo adenosine 3',5'-cyclic monophosphate (8-Br-cAMP, 1 mmol/l), 3-isobutyl-1-methyl-xanthine (IBMX, 100 mumol/l) and forskolin (10 mumol/l). No channel activity was observed in non-stimulated control cells. In both cell-attached and excised inside-out patches, the channel had a linear current/voltage relationship and a unitary conductance of 9 pS at 23 degrees C and 12 pS at 37 degrees C. Its opening probability was not voltage dependent although pronounced flickering was induced at negative potentials. Anionic substitution led to the selectivity sequence Cl- > I- >> > HCO3- > gluconate. In inside-out excised patches, the channel activity declined spontaneously within a few minutes. Reactivation of silent excised channels was achieved by adding protein kinase A (PKA, in the presence of ATP, cAMP and Mg2+). Conversely, active channels were silenced in the presence of alkaline phosphatase. The PKA-activated Cl- channel was 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS, 100 mumol/l) and 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulphonic acid (SITS, 100 mumol/l) insensitive, but was blocked by diphenylamine-2-carboxylic acid (DPC, 100 mumol/l). These results demonstrate that the apical low-conductance Cl- channel in Capan-1 is regulated on-cell by VIP receptors via cAMP and off-cell by PKA and phosphatases.(ABSTRACT TRUNCATED AT 250 WORDS)

Anion channels in a human pancreatic cancer cell line (Capan-1) of ductal origin

Transepithelial solute transport and bicarbonate secretion are major functions of pancreatic duct cells, and both functions are thought to involve the presence of chloride channels in the apical membrane of the cell. After being isolated from a human pancreatic adenocarcinoma, the Capan-1 cell line conserves most of the properties of ductal cells and thus constitutes a useful system for investigating the role of chloride channels. Using patch-clamp techniques, we identified three different chloride-selective channels in the apical membrane of confluent Capan-1 cells. Two were non-rectifying chloride channels with low (50 pS) and high (350 pS) unitary conductances. Both channels were active in cell-attached recordings, and they were consistently located together in the same patch. Maxi Cl- channels displayed multiple subconductance states, and were reversibly inactivated by either positive or negative voltage changes, which indicates that they were optimally opened at the cell resting potential. The third was an outwardly rectifying chloride channel with a unitary conductance of 38 pS and 70 pS at negative and positive potentials respectively. Rectifying Cl- channels were clustered in discrete loci. They were silent in situ, but became active after patch excision. In inside-out excised patches, the three channels displayed a high selectivity for Cl- over monovalent cations (Na+ and K+) and gluconate. They were blocked by 20-200 microM 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) and were insensitive to changes in the Ca2+ concentration. Our results show that the apical membrane of Capan-1 cells contains a high density of chloride channels; these channels may provide pathways for transepithelial solute transport as well as for bicarbonate secretion.

Patterns of growth and metastases of induced pancreatic cancer in relation to the prognosis and its clinical implications

To understand high malignancy of pancreatic cancer, the growth and metastatic patterns of pancreatic cancer induced in Syrian hamsters were examined. In this model, induced tumors resemble the human disease morphologically, clinically, biologically, and immunologically. In the current study, primary-induced cancer and transplants of pancreatic cancer cell line (PC-1) into the SC tissue or pancreas of homologous hosts were used. In the primary-induced pancreatic cancer, perineural invasion was the most common path (88%), followed by lymphogenic (31%) or vascular (2%) metastases. Inoculation of PC-1 cells into the pancreas resulted in 100% tumor take within 3 weeks. Of 19 intrapancreatic allografts, all showed peritoneal invasion, 5 (26%) liver metastases, 3 (16%) lymph node metastases, 17 (89%) perineural invasion, and none vascular invasion. Even microscopic tumors were found to metastasize primarily via perineural spaces. It was also demonstrated, for the first time, that cancer cells take this route to reach distant tissues, including the lymph nodes. Intraductal spreading occurred in both primary cancers and intrapancreatic allografts either continuously or discontinuously. The patterns of discontinuous intraductal tumor expansion imitated tumor multicentricity. Although perineural invasion was the most common feature of primary cancer and intrapancreatic allografts, lymphatic, hepatic, and vascular invasion and metastases usually occurred in advanced cases. Environmental factors seem to influence expansion and metastases, as evidenced by differences in growth and in metastatic patterns between SC and intrapancreatic allografts.

Two subclasses of EGF receptors in the human pancreatic cancer cell lines CAPAN-1 and MIA PaCa-2

The existence of different classes of EGF receptors in human pancreatic cancer cells has yet not been determined. EGF binding to two cancer cell lines (CAPAN-1 and MIA PaCa-2) was studied. Two classes of EGF binding sites were characterized. The first class of EGF binding sites demonstrated a high affinity and low capacity for EGF, with a Kd of 0.25 +/- 0.11 nM, close to the concentration of EGF suggested to be present in human pancreatic juice. The second class of EGF binding sites had a lower affinity and a higher capacity for EGF, with Kd of 1.78 +/- 0.61 nM. The total number of EGF binding sites was about 40,000/cell. Treatment of the cells with a phorbol ester, TPA, caused a complete loss of the high affinity binding sites and also caused a decrease in the concentration of the lower affinity binding sites present on the cells. Interestingly, with the increasing age of the cells, the concentration of both the high and low affinity EGF binding sites was significantly decreased. In the presence or absence of fetal calf serum, EGF, at concentrations higher than 1.10(-10)M, exerted a dose-dependent mitogenic effect on the growth of the pancreatic cancer cells in culture. These data demonstrate the existence of two classes of binding sites for EGF on some human pancreatic cancer cells and a possible role of EGF in the growth of pancreatic tumors.

Neuropeptide Y and peptide YY stimulate the growth of exocrine pancreatic carcinoma cells

Neuropeptides exert inhibitory effects on pancreatic secretion, but their role in the regulation of growth is unknown. This study was executed to evaluate the effects of PYY and NPY on cell growth and 3H-thymidine incorporation in human (MiaPaCa-2, Capan-2) and hamster (H2T) exocrine pancreatic carcinoma cells in vitro. A significant increase in the number of cells after 96 h of treatment with NPY was observed at 0.01 microM in H2T, 0.1 microM in MiaPCa-2 and at 1 microM in Capan-2 cells. PYY was less potent and did not increase significantly cell growth in MiaPaCa-2, but did at 0.1 microM in Capan-2 and at 1 microM concentration in H2T. Stimulation for 48h with NPY increased 3H-thymidine incorporation significantly at 0.01 microM in all cell lines. With PYY, stimulation of 3H-thymidine incorporation occurred in H2T cells at 0.01 microM. 3H-thymidine incorporation after PYY treatment was significantly increased at 0.1 microM in MiaPaCa-2 and at 1 microM in Capan-2 cells. Receptor studies showed low but definite specific binding of both NPY and PYY in all cell lines. The results suggest that NPY and PYY may have a role in the regulation of growth of exocrine pancreatic carcinoma cells.

Differentiation of the human pancreatic adenocarcinoma cell line (Capan-1) in culture and co-culture with fibroblasts dome formation

This study was designed to investigate differentiation of human pancreatic duct carcinoma cells (Capan-1) in vitro. Observations on live cells, and electron microscopic examination, together with enzymological and immunocytochemical methods, have demonstrated that these cells differentiate spontaneously at an early stage. The cells are seen to be joined by apical junctions. High ATPase activity can be detected in the basolateral membranes, and the cells secrete a gastric type mucin (MI) bearing acidic groups. During differentiation in culture, they form domes which are thought to be the morphological expression of trans-epithelial transport of water and electrolytes. This particular structure is transitory, since after 6 days in culture all the cells lose their adhesivity, and form into floating cords. Co-culture of Capan-1 cells and human, nude mice or chick embryo fibroblasts leads to a higher degree of differentiation of epithelial cells, reflected by the earlier appearance of numerous domes. In addition, the anchorage of Capan-1 cells to fibroblasts prevents retraction of the monolayer, and enables the domes to be maintained in the cultures for more than one month. These findings suggest that Capan-1 cells are able to carry out trans-epithelial movement of water and electrolytes. It is suggested that excretion of ions (bicarbonate and/or chloride) is preserved after transformation of pancreatic duct cells. Mucins (MI) and the recently described VIP receptor sites are also thought to play a part in these exchange processes.

Cyclic-AMP-stimulated synthesis and release of carcinoembryonic antigen by pancreatic cancer cells

The effect of cyclic adenosine 3':5'-monophosphate (cAMP) upon the synthesis and release of carcinoembryonic antigen (CEA) was studied in the human pancreatic ductal cancer cell line, SW-1990. Incubation for up to 24 h with forskolin, an activator of adenylate cyclase, or isobutylmethyl xanthine, a theophylline analog, increased cellular cAMP levels by over 100-fold and significantly increased CEA release and cellular CEA content. Whereas cAMP levels were augmented within 10 min of exposure to these agents, CEA release and CEA cell content were not increased until 90 min and 24 h, respectively. Similar results were obtained using dibutyryl-cAMP, a cAMP analog, but not using sodium butyrate, a metabolite of dibutyryl-cAMP. Cells were incubated with 35S-cysteine and 3H-glucosamine in the presence or absence of forskolin in order to compare the effects of high cAMP levels upon the synthesis and release of total proteins, total glycoproteins, and immunoprecipitable CEA. Both CEA synthesis and release were enhanced by forskolin, but these effects were not specific to CEA since the release of labeled proteins and glycoproteins also increased. In addition, altered CEA expression caused by forskolin was consistently associated with a cessation of cell division, an effect which was reversible upon removing the agent. There was no effect upon cell morphology or viability. The data indicate that increased levels of cellular cAMP in pancreatic cancer cells is associated with decreased cell proliferation and increased expression of CEA and other glycoproteins.