Histamine via histamine H1 receptor enhances the muscarinic receptor-induced calcium response to acetylcholine in an enterochromaffin cell model

As a prerequisite for serotonin secretion, the P‐STS ileal enterochromaffin cell line responds to acetylcholine (ACh) stimulation with an increase in intracellular calcium mediated by the muscarinic ACh receptor M3 (M3R). Histamine increases intracellular calcium via histamine H1 receptor (H1R) in P‐STS cells and pre‐incubation with histamine specifically augments the response to ACh but not to epinephrine or nicotine. We aimed to elucidate whether histamine receptors are involved in this synergism. Astonishingly, HEK‐293 T cells—known to express M3R, but only a very low amount of histamine receptor messenger RNA—showed a similar enhancement of the calcium response to ACh by pre‐incubation with histamine. Despite the much lower level of H1R protein detected in HEK‐293 T cells as compared to P‐STS cells, in both cell lines pre‐treatment with H1R antagonists inhibited the synergism between histamine and ACh. No indication for an involvement of histamine H2 or H4 receptors in the synergism was found. Furthermore, pre‐incubation with the cAMP‐inducing compound forskolin had no influence on the intracellular calcium response to ACh. Serotonin secretion from P‐STS cells was increased after challenge with ACh and histamine added simultaneously compared to ACh alone, suggesting that histamine increases ACh‐induced serotonin secretion from enterochromaffin cells. In conclusion, our data suggest that histamine enhances the M3R‐mediated intracellular calcium response to ACh via activation of H1R. This probably increases serotonin secretion from enterochromaffin cells and thereby affects intestinal motility in histamine intolerance, food allergies and irritable bowel syndrome.

Transcriptomic Profiling of In Vitro Tumor-Stromal Cell Paracrine Crosstalk Identifies Involvement of the Integrin Signaling Pathway in the Pathogenesis of Mesenteric Fibrosis in Human Small Intestinal Neuroendocrine Neoplasms

Aim

Analysis of the pathophysiology of mesenteric fibrosis (MF) in small intestinal neuroendocrine tumors (SI-NETs) in an in vitro paracrine model and in human SI-NET tissue samples.

Methods

An indirect co-culture model of SI-NET cells KRJ-I and P-STS with stromal cells HEK293 was designed to evaluate the paracrine effects on cell metabolic activity, gene expression by RT2 PCR Profilers to analyse cancer and fibrosis related genes, and RNA sequencing. The integrin signaling pathway, a specific Ingenuity enriched pathway, was further explored in a cohort of human SI-NET tissues by performing protein analysis and immunohistochemistry.

Results

RT Profiler array analysis demonstrated several genes to be significantly up- or down-regulated in a cell specific manner as a result of the paracrine effect. This was further confirmed by employing RNA sequencing revealing multiple signaling pathways involved in carcinogenesis and fibrogenesis that were significantly affected in these cell lines. A significant upregulation in the expression of various integrin pathway – related genes was identified in the mesenteric mass of fibrotic SI-NET as confirmed by RT-qPCR and immunohistochemistry. Protein analysis demonstrated downstream activation of the MAPK and mTOR pathways in some patients with fibrotic SI-NETs.

Conclusion

This study has provided the first comprehensive analysis of the crosstalk of SI-NET cells with stromal cells. A novel pathway – the integrin pathway – was identified and further validated and confirmed in a cohort of human SI-NET tissue featured by a dual role in fibrogenesis/carcinogenesis within the neoplastic fibrotic microenvironment.

The Transient Receptor Potential Vanilloid 4 Agonist RN-1747 Inhibits the Calcium Response to Histamine

BACKGROUND

Sensitization of transient receptor potential (TRP) cation channels probably contributes to intestinal hypersensitivity, a hallmark of gastrointestinal disorders. Histamine acting via histamine 1 receptor (H1R) to open TRP cation channels might also be involved.

METHOD

The enterochromaffin cell line P-STS, responsive to histamine via H1R, was used as model to study possible synergism between histamine and TRP vanilloid 4 (TRPV4) pathways.

RESULTS

The TRPV4 antagonist RN-1734, but not HC-067047, inhibited the cytoplasmic calcium response to histamine in P-STS cells. However, also pre-incubation with the TRPV4 agonist RN-1747 strongly inhibited the calcium response to histamine in P-STS as well as HeLa cells. This inhibitory effect of RN-1747 was not due to its known TRP melastatin 8 (TRPM8) antagonism, as the TRPM8 antagonist RQ-00203078 showed no significant effect on the histamine-induced calcium response of P-STS or HeLa cells.

CONCLUSION

The TRPV4 agonist RN-1747, and possibly also the structurally similar TRPV4 antagonist RN-1734, should be used with caution because of yet unidentified interference with histamine signaling via H1R.

The avian chorioallantoic membrane as an alternative tool to study medullary thyroid cancer

Preclinical trials of medullary thyroid cancer (MTC) therapeutics require both in vitro and in vivo analyses. Human tumour xenografted rodent models, which are considered the 'gold standard' to study and validate the efficacy and toxicity of lead compounds before translation to clinical trials, are very expensive, subject to organismal variability and ethical controversies. The avian chorioallantoic membrane (CAM) assay provides an alternative versatile, cost-effective and ethically less objectionable short-term, in vivo model for reliable screening of drugs. In this work, we grafted two MTC cell lines and patient-derived MTC tumour samples onto the avian CAM and characterised the resulted tumours histologically and immunohistochemically. Our findings provide the evidence that the CAM assay is a suitable model for studying the pathophysiology of MTC and can even be used as in vivo system for drug testing.

Histamine causes influx via T-type voltage-gated calcium channels in an enterochromaffin tumor cell line: potential therapeutic target in adverse food reactions

The P-STS human ileal neuroendocrine tumor cells, as a model for gut enterochromaffin cells, are strongly and synergistically activated by histamine plus acetylcholine (ACh), presumably via histamine 4 receptors, and weakly activated by histamine alone. Sensing these signals, enterochromaffin cells could participate in intestinal intolerance or allergic reactions to food constituents associated with elevated histamine levels. In this study we aimed to analyze the underlying molecular mechanisms. Inhibition by mepyramine and mibefradil indicated that histamine alone caused a rise in intracellular calcium concentration ([Ca²⁺]_i) via histamine 1 receptors involving T-type voltage-gated calcium channels (VGCCs). Sensitivity to histamine was enhanced by pretreatment with the inflammatory cytokine tumor necrosis factor-α (TNF-α). In accordance with the relief it offers some inflammatory bowel disease patients, otilonium bromide, a gut-impermeable inhibitor of T-type (and L-type) VGCCs and muscarinic ACh receptors, efficiently inhibited the [Ca²⁺]_i responses induced by histamine plus ACh or by histamine alone in P-STS cells. It will take clinical studies to show whether otilonium bromide has promise for the treatment of adverse food reactions. The cells did not react to the nutrient constituents glutamate, capsaicin, cinnamaldehyde, or amylase-trypsin inhibitors and the transient receptor potential channel vanilloid 4 agonist GSK-1016790A. The bacterial product butyrate evoked a rise in [Ca²⁺]_i only when added together with ACh. Lipopolysaccharide had no effect on [Ca²⁺]_i despite the presence of Toll-like receptor 4 protein. Our results indicate that inflammatory conditions with elevated levels of TNF-α might enhance histamine-induced serotonin release from intestinal neuroendocrine cells. NEW & NOTEWORTHY We show that histamine synergistically enhances the intracellular calcium response to the physiological agonist acetylcholine in human ileal enterochromaffin tumor cells. This synergistic activation and cell activation by histamine alone largely depend on T-type voltage-gated calcium channels and are inhibited by the antispasmodic otilonium bromide. The cells showed no response to wheat amylase-trypsin inhibitors, suggesting that enterochromaffin cells are not directly involved in nongluten wheat sensitivity.

Preclinical characterization of tyrosine kinase inhibitor-based targeted therapies for neuroendocrine thyroid cancer

Medullary thyroid carcinoma (MTC) is a slow growing neuroendocrine (NE) tumor for which few treatment options are available. Its incidence is rising and mortality rates have remained unchanged for decades. Increasing the repertoire of available treatments is thus crucial to manage MTC progression. Scarcity of patient samples and of relevant animal models are two challenges that have limited the development of effective non-surgical treatments. Here we use a clinically accurate mouse model of MTC to assess the effects and mode of action of the tyrosine kinase inhibitor (TKI) Vandetanib, one of only two drugs currently available to treat MTC. Effects on tumor progression, histopathology, and tumorigenic signaling were evaluated. Vandetanib blocked MTC growth through an anti-angiogenic mechanism. Furthermore, Vandetanib had an apparent anti-angiogenic effect in a patient MTC sample. Vandetanib displayed minimal anti-proliferative effects in vivo and in human and mouse MTC tumor-derived cells. Based on these results, we evaluated the second-generation TKI, Nintedanib, alone and in combination with the histone deacetylase (HDAC) inhibitor, Romidepsin, as potential alternative treatments to Vandetanib. Nintedanib showed an anti-angiogenic effect while Romidepsin decreased proliferation. Mechanistically, TKIs attenuated RET-, VEGFR2- and PI3K/AKT/FOXO signaling cascades. Nintedanib alone or in combination with Romidepsin, but not Vandetanib, inhibited mTOR signaling suggesting Nintedanib may have broader anti-cancer applicability. These findings validate the MTC mouse model as a clinically relevant platform for preclinical drug testing and reveal the modes of action and limitations of TKI therapies.

A precision oncology approach to the pharmacological targeting of mechanistic dependencies in neuroendocrine tumors

We introduce and validate a new precision oncology framework for the systematic prioritization of drugs targeting mechanistic tumor dependencies in individual patients. Compounds are prioritized on the basis of their ability to invert the concerted activity of master regulator proteins that mechanistically regulate tumor cell state, as assessed from systematic drug perturbation assays. We validated the approach on a cohort of 212 gastroenteropancreatic neuroendocrine tumors (GEP-NETs), a rare malignancy originating in the pancreas and gastrointestinal tract. The analysis identified several master regulator proteins, including key regulators of neuroendocrine lineage progenitor state and immunoevasion, whose role as critical tumor dependencies was experimentally confirmed. Transcriptome analysis of GEP-NET-derived cells, perturbed with a library of 107 compounds, identified the HDAC class I inhibitor entinostat as a potent inhibitor of master regulator activity for 42% of metastatic GEP-NET patients, abrogating tumor growth in vivo. This approach may thus complement current efforts in precision oncology.

Abstract LB-061: Systematic, network-based, comparative analysis of differential mechanisms of action of lanreotide and octreotide in neuroendocrine tumor derived cell lines

Lanreotide and octreotide are somatostatin receptor (SSTR) agonists thought to exhibit overlapping Mechanism of Action (MoA), despite small differences in their SSTRs affinity and differential PK response in vivo [1]. To systematically and quantitatively assess both concentration- and time-dependent MoA differences at the molecular level —by characterizing the full protein repertoire that mediates the compound's pharmacological effects— we assessed the protein-specific activity of lanreotide and octreotide in two gastroenteropancreatic neuroendocrine tumor (GEP-NET) derived cell lines (H-STS and KRJ-1). We performed RNASeq profiling at 4 different time points (24h -96h), following cell perturbation at 4 non-toxic doses (2 nM - 1 μM). RNASeq profiles were used to assess compound activity on 6,276 regulatory proteins, using VIPER, an experimentally-validated algorithm to infer protein activity based on the expression of its targets [2]. The analysis was performed using a GEP-NET-specific regulatory model inferred from a collection of 212 primary and metastatic human samples. Concentrations above the EC50 of the drugs were selected to (a) assess potential off-target effects and (b) discount potential effects from differential compound degradation.

Confirming the robust nature of our approach, short-term (24h and 48h) transcriptional and protein activity profiles, following compound perturbation, were virtually identical across both cell lines and drug concentration (FET p-value < 10-12). However, the sensitivity and reproducibility of VIPER analysis, which represents the foundation for two NYS CLIA approved tests, allowed identification of 367 proteins affected differentially by these drugs (FDR < 0.05), which were enriched in cancer-relevant functional categories, including apoptosis, immune response, cell differentiation, cell proliferation and DNA-repair (FDR < 10-5). Most critically, while lanreotide-modulated proteins were virtually unchanged over time (from 24h to 96h, p < 0.05), the effect of octreotide on the same proteins was transient and virtually lost at 72h. This discrepancy cannot be attributed to concentration-related effects, since it was manifested identically across all tested concentrations.

This work constitutes the first systematic, genome-wide characterization of the MoA of two clinically relevant SSTR agonists, showing both common as well as differentially affected pathways. Two key elements which may account for differential clinical response in patients emerged from the analysis: (1) Differences in the repertoire of affected proteins (MoA) by each compound, and (2) different response kinetics, with sustained lanreotide response from 24h to 96h vs. transient octreotide response with subsequent adaptive cell response after 48h.

[1] Enzler et.al (2017) Sem. Oncol. 44:141.[2] Alvarez et.al (2016) Nat. Genet. 48:838.

Citation Format: Mariano J. Alvarez, Gideon Bosker, Roswitha Pfragner, Mark Kidd, Irvin Modlin, Andrea Califano. Systematic, network-based, comparative analysis of differential mechanisms of action of lanreotide and octreotide in neuroendocrine tumor derived cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-061.

The neuroendocrine phenotype, genomic profile and therapeutic sensitivity of GEPNET cell lines

Experimental models of neuroendocrine tumour disease are scarce, and no comprehensive characterisation of existing gastroenteropancreatic neuroendocrine tumour (GEPNET) cell lines has been reported. In this study, we aimed to define the molecular characteristics and therapeutic sensitivity of these cell lines. We therefore performed immunophenotyping, copy number profiling, whole-exome sequencing and a large-scale inhibitor screening of seven GEPNET cell lines. Four cell lines, GOT1, P-STS, BON-1 and QGP-1, displayed a neuroendocrine phenotype while three others, KRJ-I, L-STS and H-STS, did not. Instead, these three cell lines were identified as lymphoblastoid. Characterisation of remaining authentic GEPNET cell lines by copy number profiling showed that GOT1, among other chromosomal alterations, harboured losses on chromosome 18 encompassing the SMAD4 gene, while P-STS had a loss on 11q. BON-1 had a homozygous loss of CDKN2A and CDKN2B, and QGP-1 harboured amplifications of MDM2 and HMGA2 Whole-exome sequencing revealed both disease-characteristic mutations (e.g. ATRX mutation in QGP-1) and, for patient tumours, rare genetic events (e.g. TP53 mutation in P-STS, BON-1 and QGP-1). A large-scale inhibitor screening showed that cell lines from pancreatic NETs to a greater extent, when compared to small intestinal NETs, were sensitive to inhibitors of MEK. Similarly, neuroendocrine NET cells originating from the small intestine were considerably more sensitive to a group of HDAC inhibitors. Taken together, our results provide a comprehensive characterisation of GEPNET cell lines, demonstrate their relevance as neuroendocrine tumour models and explore their therapeutic sensitivity to a broad range of inhibitors.

Anti-tumor effects of shikonin derivatives on human medullary thyroid carcinoma cells

New treatment options are needed for medullary thyroid carcinoma (MTC), a highly metastasizing neuroendocrine tumor that is resistant to standard radiotherapy and chemotherapy. We show that the following shikonin derivatives inhibit cell proliferation and cell viability of the MTC cell line TT: acetylshikonin, β,β-dimethylacrylshikonin, shikonin and a petroleum ether extract of the roots of Onosma paniculata containing several shikonin derivatives. The unsubstituted shikonin derivative was found to be the most effective compound with an IC₅₀ of 1.1 µM. The cell viability of normal human skin fibroblasts, however, was not affected by the tested substances, indicating that shikonin derivatives might be selectively toxic for cancer cells. We further report that migration and invasion of TT cells were inhibited at non-toxic concentrations. Finally, shikonin was tested in vivo using the chick chorioallantoic membrane assay, where it significantly reduced tumor growth by inhibiting cell proliferation and inducing apoptosis. In summary, our results suggest that shikonin derivatives have the potential for the treatment of medullary thyroid carcinomas.

MicroRNAs associated with small bowel neuroendocrine tumours and their metastases

Novel molecular analytes are needed in small bowel neuroendocrine tumours (SBNETs) to better determine disease aggressiveness and predict treatment response. In this study, we aimed to profile the global miRNome of SBNETs, and identify microRNAs (miRNAs) involved in tumour progression for use as potential biomarkers. Two independent miRNA profiling experiments were performed (n=90), including primary SBNETs (n=28), adjacent normal small bowel (NSB; n=14), matched lymph node (LN) metastases (n=24), normal LNs (n=7), normal liver (n=2) and liver metastases (n=15). We then evaluated potentially targeted genes by performing integrated computational analyses. We discovered 39 miRNAs significantly deregulated in SBNETs compared with adjacent NSB. The most upregulated (miR-204-5p, miR-7-5p and miR-375) were confirmed by qRT-PCR. Two miRNAs (miR-1 and miR-143-3p) were significantly downregulated in LN and liver metastases compared with primary tumours. Furthermore, we identified upregulated gene targets for miR-1 and miR-143-3p in an existing SBNET dataset, which could contribute to disease progression, and show that these miRNAs directly regulate FOSB and NUAK2 oncogenes. Our study represents the largest global miRNA profiling of SBNETs using matched primary tumour and metastatic samples. We revealed novel miRNAs deregulated during SBNET disease progression, and important miRNA-mRNA interactions. These miRNAs have the potential to act as biomarkers for patient stratification and may also be able to guide treatment decisions. Further experiments to define molecular mechanisms and validate these miRNAs in larger tissue cohorts and in biofluids are now warranted.

Differential expression of cell cycle regulators in CDK5-dependent medullary thyroid carcinoma tumorigenesis

Medullary thyroid carcinoma (MTC) is a neuroendocrine cancer of thyroid C-cells, for which few treatment options are available. We have recently reported a role for cyclin-dependent kinase 5 (CDK5) in MTC pathogenesis. We have generated a mouse model, in which MTC proliferation is induced upon conditional overexpression of the CDK5 activator, p25, in C-cells, and arrested by interrupting p25 overexpression. Here, we identify genes and proteins that are differentially expressed in proliferating versus arrested benign mouse MTC. We find that downstream target genes of the tumor suppressor, retinoblastoma protein, including genes encoding cell cycle regulators such as CDKs, cyclins and CDK inhibitors, are significantly upregulated in malignant mouse tumors in a CDK5-dependent manner. Reducing CDK5 activity in human MTC cells down-regulated these cell cycle regulators suggesting that CDK5 activity is critical for cell cycle progression and MTC proliferation. Finally, the same set of cell cycle proteins was consistently overexpressed in human sporadic MTC but not in hereditary MTC. Together these findings suggest that aberrant CDK5 activity precedes cell cycle initiation and thus may function as a tumor-promoting factor facilitating cell cycle protein expression in MTC. Targeting aberrant CDK5 or its downstream effectors may be a strategy to halt MTC tumorigenesis.

Cytotoxic Effects of Valproic Acid on Neuroendocrine Tumour Cells

BACKGROUND/AIMS

Histone deacetylases (HDACs) modulate lysine acetylation on histones and are frequently deregulated in cancer. HDAC inhibitors with potent anti-tumour effects have been developed and are now being tested in clinical trials. The aim of this study was to investigate the effects of valproic acid (VPA), an inhibitor of class I and class IIa HDACs, on neuroendocrine tumour (NET) cell growth.

METHODS

Three NET cell lines, GOT1 (small intestinal), KRJ-I (small intestinal), and BON (pancreatic), were treated with VPA and examined with respect to cell viability, cell cycle arrest, apoptosis, and global transcriptional response.

RESULTS

We found that VPA induced a dose-dependent growth inhibition of NET cells in vitro, which was mainly due to activation of extrinsic and intrinsic apoptotic pathways. VPA induced a major transcriptional response by altering the expression of 16-19% of the protein-coding genes in NET cell lines. Pathway analysis allowed the prediction of alterations in key regulatory pathways, e.g. activation of TGF-β1, FOXO3, p53 signalling, and inhibition of MYC signalling. Analysis of GOT1 xenografts showed reduced growth and reduced Ki-67 index, as well as an increase in apoptosis and necrosis after VPA treatment.

CONCLUSIONS

We found that VPA treatment has a cytotoxic effect on NET cells of intestinal and pancreatic origin. There are several mechanisms by which VPA kills NET cells, which suggests the possibility of combination therapy. We propose that epigenetic therapy with HDAC inhibitors should be evaluated further in patients with NET disease.

The anti-hypertensive drug prazosin induces apoptosis in the medullary thyroid carcinoma cell line TT

BACKGROUND/AIM

Medullary thyroid carcinoma (MTC) is a tumor associated with poor prognosis since it exhibits high resistance against conventional cancer therapy. Recent studies have shown that quinazolines exhibit a pro-apoptotic effect on malignant cells. The aim of the present study was to elucidate whether MTC cells are affected by quinazolines, in particular prazosin.

MATERIALS AND METHODS

Proliferation, apoptosis and cell morphology of the MTC cell line TT were analyzed by WST-1 assay, caspase 3/7 activation tests and microscopy. Fibroblasts were used as control for non-malignant cells.

RESULTS

Prazosin potently inhibited the growth of TT cells, induced apoptosis and caused vacuolization, as well as needle-like filopodia. Fibroblasts were affected by prazosin in the same way as MTC cells.

CONCLUSION

MTC cells are responsive to prazosin treatment similar to other malignancies. The fact that fibroblasts also respond to prazosin further highlights the importance to identify the unknown pro-apoptotic target of quinazolines.

Chromogranin A and its fragments as regulators of small intestinal neuroendocrine neoplasm proliferation

INTRODUCTION

Chromogranin A is a neuroendocrine secretory product and its loss is a feature of malignant NEN de-differentiation. We hypothesized that chromogranin A fragments were differentially expressed during NEN metastasis and played a role in the regulation of NEN proliferation.

METHODS

Chromogranin A mRNA (PCR) and protein (ELISA/western blot) were studied in 10 normal human mucosa, 5 enterochromaffin cell preparations, 26 small intestinal NEN primaries and 9 liver metastases. Cell viability (WST-1 assay), proliferation (bromodeoxyuridine ELISA) and expression of AKT/AKT-P (CASE ELISA/western blot) in response to chromogranin A silencing, inhibition of prohormone convertase and mTOR inhibition (RAD001/AKT antisense) as well as different chromogranin A fragments were examined in 4 SI-NEN cell lines.

RESULTS

Chromogranin A mRNA and protein levels were increased (37-340 fold, p<0.0001) in small intestinal NENs compared to normal enterochromaffin cells. Western blot identified chromogranin A-associated processing bands including vasostatin in small intestinal NENs as well as up-regulated expression of prohormone convertase in metastases. Proliferation in small intestinal NEN cell lines was decreased by silencing chromogranin A as well as by inhibition of prohormone convertase (p<0.05). This inhibition also decreased secretion of chromogranin A (p<0.05) and 5-HT (p<0.05) as well as expression of vasostatin. Metastatic small intestinal NEN cell lines were stimulated (50-80%, p<0.05) and AKT phosphorylated (Ser473: p<0.05) by vasostatin I, which was completely reversed by RAD001 (p<0.01) and AKT antisense (p<0.05) while chromostatin inhibited proliferation (~50%, p<0.05).

CONCLUSION

Chromogranin A was differentially regulated in primary and metastatic small intestinal NENs and cell lines. Chromogranin A fragments regulated metastatic small intestinal NEN proliferation via the AKT pathway indicating that CgA plays a far more complex role in the biology of these tumors than previously considered.

The role of Cdk5 in neuroendocrine thyroid cancer

Medullary thyroid carcinoma (MTC) is a neuroendocrine cancer that originates from calcitonin-secreting parafollicular cells, or C cells. We found that Cdk5 and its cofactors p35 and p25 are highly expressed in human MTC and that Cdk5 activity promotes MTC proliferation. A conditional MTC mouse model was generated and corroborated the role of aberrant Cdk5 activation in MTC. C cell-specific overexpression of p25 caused rapid C cell hyperplasia leading to lethal MTC, which was arrested by repressing p25 overexpression. A comparative phosphoproteomic screen between proliferating and arrested MTC identified the retinoblastoma protein (Rb) as a crucial Cdk5 downstream target. Prevention of Rb phosphorylation at Ser807/Ser811 attenuated MTC proliferation. These findings implicate Cdk5 signaling via Rb as critical to MTC tumorigenesis and progression.

Serotonin and the 5-HT7 receptor: the link between hepatocytes, IGF-1 and small intestinal neuroendocrine tumors

Platelet-derived serotonin (5-HT) is involved in liver regeneration. The liver is also the metastatic site for malignant enterochromaffin (EC) cell "carcinoid" (neuroendocrine) neoplasms, the principal cellular source of 5-HT. We hypothesized that 5-HT produced by metastatic EC cells played a role in the hepatic tumor-microenvironment principally via 5-HT₇ receptor-mediated activation of hepatocyte IGF-1 synthesis and secretion. Using isolated rat hepatocytes, we evaluated 5-HT₇ receptor expression (using PCR, sequencing and western blot). ELISA, cell transfection and western blots delineated 5-HT-mediated signaling pathways (pCREB, AKT and ERK). IGF-1 synthesis/secretion was evaluated using QPCR and ELISA. IGF-1 was tested on small intestinal neuroendocrine neoplasm proliferation, while IGF-1 production and 5-HT₇ expression were examined in an in vivo SCID metastasis model. Our results demonstrated evidence for a functional 5-HT₇ receptor. 5-HT activated cAMP/PKA activity, pCREB (130-205%, P < 0.05) and pERK/pAKT (1.2-1.75, P < 0.05). Signaling was reversed by the 5-HT₇ receptor antagonist SB269970. IGF-1 significantly stimulated proliferation of two small intestinal neuroendocrine neoplasm cell lines (EC₅₀: 7-70 pg/mL) and could be reversed by the small molecule inhibitor BMS-754807. IGF-1 and 5-HT were elevated (40-300×) in peri-tumoral hepatic tissue in nude mice, while 5-HT₇ was increased fourfold compared to sham-operated animals. We conclude that hepatocytes express a cAMP-coupled 5-HT₇ receptor, which, at elevated 5-HT concentrations that occur in liver metastases, signals via CREB/AKT and is linked to IGF-1 synthesis and secretion. Because IGF-1 regulates NEN proliferation, identification of a role for 5-HT₇ in the hepatic metastatic tumor microenvironment suggests the potential for novel therapeutic strategies for amine-producing mid-gut tumors.

The stimulatory adenosine receptor ADORA2B regulates serotonin (5-HT) synthesis and release in oxygen-depleted EC cells in inflammatory bowel disease

OBJECTIVE

We recently demonstrated that hypoxia, a key feature of IBD, increases enterochromaffin (EC) cell 5-HT secretion, which is also physiologically regulated by the ADORA2B mechanoreceptor. Since hypoxia is associated with increased extracellular adenosine, we wanted to examine whether this nucleotide amplifies HIF-1α-mediated 5-HT secretion.

DESIGN

The effects of hypoxia were studied on IBD mucosa, isolated IBD-EC cells, isolated normal EC cells and the EC cell tumor derived cell line KRJ-1. Hypoxia (0.5% O2) was compared to NECA (adenosine agonist), MRS1754 (ADORA2B receptor antagonist) and SCH442146 (ADORA2A antagonist) on HIF signaling and 5-HT secretion. Antisense approaches were used to mechanistically evaluate EC cells in vitro. PCR and western blot were used to analyze transcript and protein levels of HIF-1α signaling and neuroendocrine cell function. An animal model of colitis was evaluated to confirm hypoxia:adenosine signaling in vivo.

RESULTS

HIF-1α is upregulated in IBD mucosa and IBD-EC cells, the majority (~90%) of which express an activated phenotype in situ. Hypoxia stimulated 5-HT release maximally at 30 mins, an effect amplified by NECA and selectively inhibited by MRS1754, through phosphorylation of TPH-1 and activation of VMAT-1. Transient transfection with Renilla luciferase under hypoxia transcriptional response element (HRE) control identified that ADORA2B activated HIF-1α signaling under hypoxic conditions. Additional signaling pathways associated with hypoxia:adenosine included MAP kinase and CREB. Antisense approaches mechanistically confirmed that ADORA2B signaling was linked to these pathways and 5-HT release under hypoxic conditions. Hypoxia:adenosine activation which could be reversed by 5'-ASA treatment was confirmed in a TNBS-model.

CONCLUSION

Hypoxia induced 5-HT synthesis and secretion is amplified by ADORA2B signaling via MAPK/CREB and TPH-1 activation. Targeting ADORA2s may decrease EC cell 5-HT production and secretion in IBD.

The influence of glutamate receptors on proliferation and metabolic cell activity of neuroendocrine tumors

Neuroendocrine tumors are relatively insensitive to radiation therapy, as well as chemotherapy. Thus, new approaches for alternative therapies are needed. We found that glutamate receptor antagonists are capable of suppressing tumor growth and cell activity of different peripheral malignancies. In the present article we review scientific literature in this field of science. Subtype-specific, non-competitive, metabotropic glutamate receptor-1 antagonists differently suppressed the growth and metabolic cell activity of one human medullary thyroid carcinoma cell line, as well as of four different human midgut neuroendocrine tumor cell lines. Furthermore, PCR analyses revealed that this subtype of glutamate receptor is expressed in these cell lines. These first results indicate that specific metabotropic glutamate receptor antagonists suppress the proliferation and cell activity of neuroendocrine tumor cells, which makes them possible targets in cancer therapy.

Christia vespertilionis plant extracts as novel antiproliferative agent against human neuroendocrine tumor cells

Neuroendocrine tumors respond poorly to radiation and conventional chemotherapy, hence surgical removal of the neoplastic tissue is still the most effective way of treatment. In an attempt to find new therapeutic plant extracts of Christia vespertilionis (CV) their antitumor potential in human medullary thyroid carcinoma (MTC) and human small intestinal neuroendocrine tumor (SI-NET) cell lines were tested. Proliferation and viability were analyzed using cell counting and WST-1 assay. Apoptosis was determined by microscopy, luminescence assays for caspases 3/7, and expression studies of apoptosis-related genes. CV extracts showed antiproliferative and proapoptotic effects in all MTC and SI-NET cell lines, whereby high growth inhibition was observed by treatment with the ethylacetate-extracts (CV-45) in tumor cell lines but not in normal human fibroblasts. Furthermore CV-45 treatment resulted in alterations of gene expression of PDCD5, MTDH and TNFRSF10b in MTC as well as in SI-NET cells. The results indicate that Christia vespertilionis could serve as an anticancer therapeutic for treatment of neuroendocrine tumors.

Differential signal pathway activation and 5-HT function: the role of gut enterochromaffin cells as oxygen sensors

The chemomechanosensory function of the gut enterochromaffin (EC) cell enables it to respond to dietary agents and mechanical stretch. We hypothesized that the EC cell, which also sensed alterations in luminal or mucosal oxygen level, was physiologically sensitive to fluctuations in O(2). Given that low oxygen levels induce 5-HT production and secretion through a hypoxia inducible factor 1α (HIF-1α)-dependent pathway, we also hypothesized that increasing O(2) would reduce 5-HT production and secretion. Isolated normal EC cells as well as the well-characterized EC cell model KRJ-I were used to examine HIF signaling (luciferase-assays), hypoxia transcriptional response element (HRE)-mediated transcription (PCR), signaling pathways (Western blot), and 5-HT release (ELISA) during exposure to different oxygen levels. Normal EC cells and KRJ-I cells express HIF-1α, and transient transfection with Renilla luciferase under HRE control identified a hypoxia-mediated pathway in these cells. PCR confirmed activation of HIF-downstream targets, GLUT1, IGF2, and VEGF under reduced O(2) levels (0.5%). Reducing O(2) also elevated 5-HT secretion (2-3.2-fold) as well as protein levels of HIF-1α (1.7-3-fold). Increasing O(2) to 100% inhibited HRE-mediated signaling, transcription, reduced 5-HT secretion, and significantly lowered HIF-1α levels (∼75% of control). NF-κB signaling was also elevated during hypoxia (1.2-1.6-fold), but no significant changes were noted in PKA/cAMP. We concluded that gut EC cells are oxygen responsive, and alterations in O(2) levels differentially activate HIF-1α and tryptophan hydroxylase 1, as well as NF-κB signaling. This results in alterations in 5-HT production and secretion and identifies that the chemomechanosensory role of EC cells extends to oxygen sensing.

Molecular evidence for the bi-clonal origin of neuroendocrine tumor derived metastases

Background

Reports on common mutations in neuroendocrine tumors (NET) are rare and clonality of NET metastases has not been investigated in this tumor entity yet. We selected one NET and the corresponding lymph node and liver metastases as well as the derivative cell lines to screen for somatic mutations in the primary NET and to track the fate of genetic changes during metastasis and in vitro progression.

Results

Applying microarray based sequence capture resequencing including 4,935 Exons from of 203 cancer-associated genes and high-resolution copy number and genotype analysis identified multiple somatic mutations in the primary NET, affecting BRCA2, CTNNB1, ERCC5, HNF1A, KIT, MLL, RB1, ROS1, SMAD4, and TP53. All mutations were confirmed in the patients’ lymph node and liver metastasis tissue as well as early cell line passages. In contrast to the tumor derived cell line, higher passages of the metastases derived cell lines lacked somatic mutations and chromosomal alterations, while expression of the classical NET marker serotonin was maintained.

Conclusion

Our study reveals that both metastases have evolved from the same pair of genetically differing NET cell clones. In both metastases, the in vivo dominating “mutant” tumor cell clone has undergone negative selection in vitro being replaced by the “non-mutant” tumor cell population. This is the first report of a bi-clonal origin of NET derived metastases, indicating selective advantage of interclonal cooperation during metastasis. In addition, this study underscores the importance to monitor cell line integrity using high-resolution genome analysis tools.

Establishment of a continuous cell line from a human carcinoid of the small intestine (KRJ-I)

A new continuous cell line from a human malignant carcinoid of the small intestine (KRJ-I) was established. The cells showed morphological and immunocytochemical features of the tumor of origin and expressed estrogen receptors. The cells are growing as a suspension, forming multicellular aggregates and spheroids. Electron microscopy confirmed the presence of neuroendocrine granules. Dose-dependent growth inhibition was observed after incubation with 5-azacytidine. Cytogenetic analyses of the tumor of origin, the cell line KRJ-I and a liver metastasis KRJ-II revealed clonal tetraploidy and clonal loss of the Y-chromosome and chromosome 19.

New continuous cell-line from human medullary-thyroid carcinoma - sinj - phenotypic analysis and invivo carcinogenesis

SINJ is a new continuous human cell line derived from a lymph node metastasis of a probably sporadic medullary thyroid carcinoma. It is compared to MTC-SK, another medullary thyroid carcinoma cell line, established earlier (1). SINJ has been continuously cultivated in vitro for two years. The cells grow as a suspension of single cells and cell clusters. Repeated immunocytochemistry showed positive immunoreactivity with antibodies to CT, CGRP and GRP. The maintenance of NSE and chromogranins were proved. Northern blot analysis confirmed endocrine activity at mRNA level. Flow cytometry of 27 SINJ - clones showed 25 diploid and two tetraploid subpopulations. Cytogenetic analyses strengthened these findings. According to DNA analysis the cells are free of SV40 sequences. Tumorigenicity was proved in nude mice. The new cell line SINJ has potential use for in vitro studies of medullary thyroid carcinomas in sporadic as well as hereditary forms - the MEN2A syndrome.

Microencapsulation of small intestinal neuroendocrine neoplasm cells for tumor model studies

Basic cancer research is dependent on reliable in vitro and in vivo tumor models. The serotonin (5-HT) producing small intestinal neuroendocrine tumor cell line KRJ-1 has been used in in vitro proliferation and secretion studies, but its use in in vivo models has been hampered by problems related to the xeno-barrier and tumor formation. This may be overcome by the encapsulation of tumor cells into alginate microspheres, which can function as bioreactors and protect against the host immune system. We used alginate encapsulation of KRJ-1 cells to achieve long-term functionality, growth and survival. Different conditions, including capsule size, variations in M/G content, gelling ions (Ca(2+) /Ba(2+)) and microcapsule core properties, and variations in KRJ-1 cell condition (single cells/spheroids) were tested. Viability and cell growth was evaluated with MTT, and confocal laser scanner microscopy combined with LIVE/DEAD viability stains. 5-HT secretion was measured to determine functionality. Under all conditions, single cell encapsulation proved unfavorable due to gradual cell death, while encapsulation of aggregates/spheroids resulted in surviving, functional bioreactors. The most ideal spheroids for encapsulation were 200-350 μm. Long-term survival (>30 days) was seen with solid Ca(2+) /Ba(2+) microbeads and hollow microcapsules. Basal 5-HT secretion was increased (sixfold) after hollow microcapsule encapsulation, while Ca(2+) /Ba(2+) microbeads was associated with normal basal secretion and responsiveness to cAMP/PKA activation. In conclusion, encapsulation of KRJ-1 cells into hollow microcapsules produces a bioreactor with a high constitutively activate basal 5-HT secretion, while Ca(2+) /Ba(2+) microbeads provide a more stable bioreactor similar to non-encapsulated cells. Alginate microspheres technology can thus be used to tailor different functional bioreactors for both in vitro and in vivo studies.

The role of mechanical forces and adenosine in the regulation of intestinal enterochromaffin cell serotonin secretion

Enterochromaffin (EC) cells of the diffuse neuroendocrine cell system secrete serotonin (5-HT) with activation of gut motility, secretion, and pain. These cells express adenosine (ADORA) receptors and are considered to function as mechanosensors. Physiological pathways mediating mechanosensitivity and adenosine responsiveness remain to be fully elucidated, as do their roles in inflammatory bowel disease (IBD) and neoplasia. Pure (98-99%) FACS-sorted normal and IBD human EC cells and neoplastic EC cells (KRJ-I) were studied. IBD-EC cells and KRJ-I overexpressed ADORA2B. NECA, a general ADORA receptor agonist, stimulated, whereas the A2B receptor antagonist MRS1754 inhibited, 5-HT release (EC50 = 1.8 × 10-6 M; IC50 = 3.7 × 10-8 M), which was associated with corresponding alterations in intracellular cAMP levels and pCREB (Ser133). Mechanical stimulation using a rhythmic flex model induced transcription and activation of Tph1 (tryptophan hydroxylase) and VMAT₁ (vesicular monoamine transporter 1) and the release of 5-HT, which could be inhibited by MRS1754 and amplified by NECA. Secretion was also inhibited by H-89 (PKA inhibitor) while Tph1 and VMAT₁ transcription was regulated by PKA/MAPK and PI₃K-mediated signaling. Normal and IBD-EC cells also responded to NECA and mechanical stimulation with PKA activation, cAMP production, and 5-HT release, effects reversible by MRS1754. EC cells express stimulatory ADORA2B, and rhythmic stretch induces A2B activation, PKA/MAPK/IP3-dependent transcription, and PKA-dependent secretion of 5-HT synthesis and secretion. Receptor expression is amplified in IBD and neoplasia, and 5-HT release is increased. Determination of factors that regulate EC cell function are necessary for understanding its role as a mechanosensory cell and to facilitate the development of agents that can selectively target cell function in EC cell-associated disease.

High-resolution analysis of alterations in medullary thyroid carcinoma genomes

Hereditary and sporadic medullary thyroid carcinoma (MTC) are closely associated with RET proto-oncogene mutations. However, the role of additional changes in the tumor genomes remains unclear. Our objective was the identification of chromosomal regions involved in MTC tumorigenesis and to assess their significance by using MTC-derived cell lines. We used array-CGH (comparative genomic hybridization) to map chromosomal imbalances in 52 primary tumors and ten metastases. Eleven tumors (11/52, 21%) were hereditary and 41 (41/52, 79%) were sporadic. Among the latter, 15 tumors (15/41, 37%) harbored RET mutations. Furthermore, we characterized five MTC cell lines in detail and evaluated the tumorigenicity by severe combined immunodeficiency (SCID)-mouse experiments. Most MTCs had only few copy number changes, and losses of chromosomes 1p, 4q, 19p and 22q were observed most frequently. The number of chromosomal aberrations increased in metastases. Twenty-three percent (12/52) of the primary tumors did not even show any chromosomal gains and losses. We injected three cell lines (two of these were without chromosomal changes and pathogenic RET mutations) into immune deficient SCID mice, and in each case, we observed rapid tumor growth at the injection sites. Our data suggest that MTCs--in contrast to most other tumor entities--do not acquire a multitude of genomic imbalances. SCID mouse experiments performed with chromosomally normal cell lines and without RET mutations suggest that presently unknown submicroscopic genomic changes are sufficient in MTC tumorigenesis.

Adenosine A2A and A2B receptor expression in neuroendocrine tumours: potential targets for therapy

The clinical management of neuroendocrine tumours is complex. Such tumours are highly vascular suggesting tumour-related angiogenesis. Adenosine, released during cellular stress, damage and hypoxia, is a major regulator of angiogenesis. Herein, we describe the expression and function of adenosine receptors (A(1), A(2A), A(2B) and A(3)) in neuroendocrine tumours. Expression of adenosine receptors was investigated in archival human neuroendocrine tumour sections and in two human tumour cell lines, BON-1 (pancreatic) and KRJ-I (intestinal). Their function, with respect to growth and chromogranin A secretion was carried out in vitro. Immunocytochemical data showed that A(2A) and A(2B) receptors were strongly expressed in 15/15 and 13/18 archival tumour sections. Staining for A(1) (4/18) and A(3) (6/18) receptors was either very weak or absent. In vitro data showed that adenosine stimulated a three- to fourfold increase in cAMP levels in BON-1 and KRJ-1 cells. The non-selective adenosine receptor agonist (adenosine-5'N-ethylcarboxamide, NECA) and the A(2A)R agonist (CGS21680) stimulated cell proliferation by up to 20-40% which was attenuated by A(2B) (PSB603 and MRS1754) and A(2A) (SCH442416) receptor selective antagonists but not by the A(1) receptor antagonist (PSB36). Adenosine and NECA stimulated a twofold increase in chromogranin A secretion in BON-1 cells. Our data suggest that neuroendocrine tumours predominantly express A(2A) and A(2B) adenosine receptors; their activation leads to increased proliferation and secretion of chromogranin A. Targeting adenosine signal pathways, specifically inhibition of A(2) receptors, may thus be a useful addition to the therapeutic management of neuroendocrine tumours.

A water soluble tri-cationic porphyrin-EDTA conjugate induces apoptosis in human neuroendocrine tumor cell lines

In this study, a completely water soluble tri-cationic porphyrin–EDTA conjugate was synthesized. We present data demonstrating the tumoristatic effects of the novel fully water soluble cationic porphyrin TMPy₃PhenEDTA-P-Cl₄ in the dark, in the medullary thyroid carcinoma cell lines MTC-SK and SHER-I and weaker effects in the small intestinal neuroendocrine tumor cell line KRJ-I. In addition, cytotoxic effects were also studied in normal human fibroblasts that represent normal tissue and the results are compared to the tumor cell lines.

Gene network inference and biochemical assessment delineates GPCR pathways and CREB targets in small intestinal neuroendocrine neoplasia

Small intestinal (SI) neuroendocrine tumors (NET) are increasing in incidence, however little is known about their biology. High throughput techniques such as inference of gene regulatory networks from microarray experiments can objectively define signaling machinery in this disease. Genome-wide co-expression analysis was used to infer gene relevance network in SI-NETs. The network was confirmed to be non-random, scale-free, and highly modular. Functional analysis of gene co-expression modules revealed processes including ‘Nervous system development’, ‘Immune response’, and ‘Cell-cycle’. Importantly, gene network topology and differential expression analysis identified over-expression of the GPCR signaling regulators, the cAMP synthetase, ADCY2, and the protein kinase A, PRKAR1A. Seven CREB response element (CRE) transcripts associated with proliferation and secretion: BEX1, BICD1, CHGB, CPE, GABRB3, SCG2 and SCG3 as well as ADCY2 and PRKAR1A were measured in an independent SI dataset (n = 10 NETs; n = 8 normal preparations). All were up-regulated (p<0.035) with the exception of SCG3 which was not differently expressed. Forskolin (a direct cAMP activator, 10⁻⁵ M) significantly stimulated transcription of pCREB and 3/7 CREB targets, isoproterenol (a selective ß-adrenergic receptor agonist and cAMP activator, 10⁻⁵ M) stimulated pCREB and 4/7 targets while BIM-53061 (a dopamine D₂ and Serotonin [5-HT₂] receptor agonist, 10⁻⁶ M) stimulated 100% of targets as well as pCREB; CRE transcription correlated with the levels of cAMP accumulation and PKA activity; BIM-53061 stimulated the highest levels of cAMP and PKA (2.8-fold and 2.5-fold vs. 1.8–2-fold for isoproterenol and forskolin). Gene network inference and graph topology analysis in SI NETs suggests that SI NETs express neural GPCRs that activate different CRE targets associated with proliferation and secretion. In vitro studies, in a model NET cell system, confirmed that transcriptional effects are signaled through the cAMP/PKA/pCREB signaling pathway and that a SI NET cell line was most sensitive to a D₂ and 5-HT₂ receptor agonist BIM-53061.

Limitations in small intestinal neuroendocrine tumor therapy by mTor kinase inhibition reflect growth factor-mediated PI3K feedback loop activation via ERK1/2 and AKT

BACKGROUND

Treatment of small intestinal neuroendocrine tumors (SINETs) with mammalian target of rapamycin (mTOR) inhibitors alone or with somatostatin analogs has been proposed as effective therapy, because both agents have been reported to exhibit antiproliferative activity. Because adenocarcinomas escape mTOR inhibition, we examined whether the escape phenomenon occurred in SINETs and whether usage of somatostatin analogs with mTOR inhibitors surmounted loss of inhibition.

METHODS

The effects of the somatostatin analog octreotide (OCT), the mTOR inhibitor RAD001 (RAD), or the combination were evaluated in SINET cell lines (KRJ-I, H-STS) using cell viability assays, western blotting, enzyme-linked immunosorbent assay, and reverse-transcription polymerase chain reaction to assess antiproliferative signaling pathways and feedback regulation.

RESULTS

RAD (10(-9) M) incompletely decreased cell viability (-40% to +15%); growth escape (P < .001) was noted at 72 hours in both cell lines. Phosphorylated (p)mTOR/mTOR and pp70S6K/p70S6K ratios were decreased but were associated with increases in phosphorylated extracellular signal-regulated kinase (pERK)/ERK and pAKT/AKT in both cell lines, whereas phosphorylated insulin-like growth factor 1 receptor (pIGF-1R)/IGF-1R levels were elevated only in H-STS cells. Increased (P < .05) transcript levels for AKT1, MAPK, mTOR, IGF-1R, IGF-1, and TGFβ1 were evident. OCT (10(-6) M) itself had no significant effect on growth signaling in either cell line. An antiproliferative effect (66 ± 5%) using OCT+RAD was only noted in the KRJ-I cells (P < .05).

CONCLUSIONS

SINET treatment with the mTOR inhibitor RAD had no antiproliferative effect based on activation of pAKT and pERK1/2. A combinatorial approach using OCT and RAD failed to overcome this escape phenomenon. However, differences in RAD response rates in individual NET cell lines suggested that pretreatment identification of different tumor sensitivity to mTOR inhibitors could provide the basis for individualized treatment.

Peripheral glutamate signaling in head and neck areas

The major excitatory neurotransmitter glutamate is also found in the periphery in an increasing number of nonexcitable cells. In line with this it became apparent that glutamate can regulate a broad array of peripheral biological responses, as well. Of particular interest is the discovery that glutamate receptor reactive reagents can influence tumor biology. However, the knowledge of glutamate signaling in peripheral tissues is still incomplete and, in the case of head and neck areas, is almost lacking. The roles of glutamate signaling pathways in these regions are manifold and include orofacial pain, periodontal bone production, skin and airway inflammation, as well as salivation. Furthermore, the interrelations between glutamate and cancers in the oral cavity, thyroid gland, and other regions are discussed. In summary, this review shall strengthen the view that glutamate receptor reagents may also be promising targets for novel therapeutic concepts suitable for a number of diseases in peripheral tissues. The contents of this review cover the following sections: Introduction; The "Glutamate System"; The Taste of Glutamate; Glutamate Signaling in Dental Regions; Glutamate Signaling in Head and Neck Areas; Glutamate Signaling in Head and Neck Cancer; A Brief Overview of Glutamate Signaling in Other Cancers; and Conclusion.

Mutations of the metabolic genes IDH1, IDH2, and SDHAF2 are not major determinants of the pseudohypoxic phenotype of sporadic pheochromocytomas and paragangliomas

CONTEXT

Pheochromocytomas and paragangliomas are genetically heterogeneous tumors of neural crest origin. Approximately half of these tumors activate a pseudohypoxic transcription response, which is due in a minority of the cases to germline mutations of the VHL gene or the genes encoding subunits of the metabolic enzyme succinate dehydrogenase (SDH), SDHB, SDHC, or SDHD. However, the genetic basis of the hypoxic-like profile of the remaining tumors is undetermined. Mutations in genes involved in the energy metabolism, isocitrate dehydrogenase 1 (IDH1) and -2 (IDH2) and SDHAF2, a component of SDH, can mimic a pseudohypoxic state.

DESIGN

We examined the sequence spanning the mutation-susceptible codons 132 of IDH1 and 172 of IDH2, and the entire coding region of SDHAF2, in 104 pheochromocytomas and paragangliomas, including tumors with a pseudohypoxic expression profile.

RESULTS

We did not find mutations in IDH1, IDH2, or SDHAF2 in any of the tumors in this cohort.

CONCLUSION

Conserved residues of IDH1 and IDH2 or the SDHAF2 gene are not frequently mutated in pheochromocytomas and paragangliomas. The molecular basis for activation of a hypoxic response in the majority of tumors without VHL or SDH mutations remains to be defined.

Anticancer activity of novel plant extracts from Trailliaedoxa gracilis (W. W. Smith & Forrest) in human carcinoid KRJ-I Cells

BACKGROUND

Small intestinal (SI) neuroendocrine tumors (NETs) are rare neoplasms derived from neuroendocrine cells presenting distinct clinical symptoms according to the ability to secrete neuroamines. Nevertheless, many are asymptomatic and misdiagnosed. As response rates to chemotherapy are low, surgery remains the only effective treatment. Because many tumors have metastasized at the time of diagnosis, curative surgery is rarely achieved. Consequently, a substantial need for new therapeutic options has emerged.

MATERIALS AND METHODS

The effects of novel plant extracts from Trailliaedoxa gracilis (W.W. Smith & Forrest) were investigated in the SI-NET cell line KRJ-I and in KRJ-I transplanted mice. Proliferation and viability were analyzed using cell counting and WST-1 cell proliferation assay. Apoptosis was determined by DAPI staining and electron microscopy, and quantified by luminescence assays for caspases 3/7, 6, 8, 9 and 2.

RESULTS

Extracts of Trailliaedoxa gracilis showed a dose-dependent reduction of proliferation and induction of apoptosis in the KRJ-I cells. Normal fibroblasts were not impaired. Tumor growth inhibition was also observed in heterotransplanted SCID (severe combined immunodeficiency) mice.

CONCLUSION

The in vitro and in vivo outcomes suggest a potential clinical effect of Trailliaedoxa gracilis in SI-NETs.

Autoregulatory effects of serotonin on proliferation and signaling pathways in lung and small intestine neuroendocrine tumor cell lines

BACKGROUND

: Survival rates for gastrointestinal (GI) and bronchopulmonary (BP) neuroendocrine tumors (NETs) have not altered significantly (5-year survival rate: GI NETs, 64.1%; BP NETs, 87%-89%) in 30 years (from 1973 to 2004). No effective or specific antineoplastic agents are available to date, although somatostatin analogs inhibit NET 5-hydroxytryptophan (5-HT) secretion. Given the expression of 5-HT receptors on NETs, the authors hypothesized that 5-HT autoregulated NET proliferation.

METHODS

: Proliferation was evaluated in 3 NET cell lines using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide uptake; in addition, real-time polymerase chain reaction analyses and enzyme-linked immunosorbent assay studies were performed to delineate 5-HT-mediated signaling pathways. To determine the receptor and role of endogenous 5-HT production, the effects of ketanserin (5-HT receptor subtypes 2A and 2C [5-HT(2A/2C)]); ondansetron (5-HT(3)); and the suicide inhibitor of the rate-limiting enzyme for 5-HT synthesis, tryptophan hydroxylase (7-HTP) were investigated.

RESULTS

: Exogenously added 5-HT stimulated proliferation in atypical BP NET NCI-H720 cells (+50%; half-maximal stimulatory concentration [EC(50)] = 10 nM), in typical BP NET NCI-H727 cells (+40%; EC(50) = 0.01 nM), and in GI NET KRJ-I cells (+60%; EC(50) = 25 nM). In NCI-H720 cells, proliferation was inhibited by ketanserin (half-maximal inhibitory concentration [IC(50)] = 0.06 nM) and ondansetron (IC(50) = 0.4 nM) and also was inhibited by 7-HTP (IC(50) = 0.3 nM). In NCI-H727 cells, ketanserin and 7-HTP inhibited proliferation (IC(50) = 0.3 nM and IC(50) = 2.3 nM, respectively), whereas ondansetron had no effect. In KRJ-I cells, ketanserin (IC(50) = 0.1 nM) and 7-HTP (IC(50) = 0.6 nM), but not ondansetron, inhibited proliferation. In all cell lines, 5-HT activated proliferation through extracellular signal-regulated kinase 1 (ERK1) and ERK2 phosphorylation and c-Jun N-terminal kinase (JNK)-mediated pathways (c-JUN and Ki-67 transcription). An autoregulatory effect was indicated by the 7-HTP-mediated inhibition of extracellular 5-HT and downstream effects on NET proliferation.

CONCLUSIONS

: Lung and GI NET proliferation was autoregulated by 5-HT through alterations in ERK and JNK signaling. Targeting NET cells with 5-HT(2) receptor antagonists and 7-HTP reversed proliferation. The current results indicated that 5-HT(2) receptor subtype-specific antagonists may represent a viable antiproliferative therapeutic strategy. Cancer 2009. (c) 2009 American Cancer Society.

Antiproliferative and pro-apoptotic effects of Uncaria tomentosa in human medullary thyroid carcinoma cells

Medullary thyroid carcinoma (MTC), a rare calcitonin-producing tumor, is derived from parafollicular C-cells of the thyroid and is characterized by constitutive Bcl-2 overexpression. The tumor is relatively insensitive to radiation therapy as well as conventional chemotherapy. To date, the only curative treatment is the early and complete surgical removal of all neoplastic tissue. In this study, the antiproliferative and pro-apoptotic effects of fractions obtained from Uncaria tomentosa (Willd.) DC, commonly known as uña de gato or cat's claw were investigated. Cell growth of MTC cells as well as enzymatic activity of mitochondrial dehydrogenase was markedly inhibited after treatment with different fractions of the plant. Furthermore, there was an increase in the expressions of caspase-3 and -7 and poly(ADP-ribose) polymerase (PARP) fraction, while bcl-2 overexpression remained constant. In particular, the alkaloids isopterpodine and pteropodine of U. tomentosa exhibited a significant pro-apoptotic effect on MTC cells, whereas the alkaloid-poor fraction inhibited cell proliferation but did not show any pro-apoptotic effects. These promising results indicate the growth-restraining and apoptotic potential of plant extracts against neuroendocrine tumors, which may add to existing therapies for cancer.

Establishment of stably transfected rat neuronal cell lines expressing alpha-synuclein GFP fusion proteins

Mutations in the alpha-synuclein gene have been linked to rare cases of familial Parkinson's disease (PD). alpha-Synuclein, a 140 amino acid polypeptide, is a major component of Lewy bodies (LB), a pathological hallmark of PD. Transgenic mice, Drosophila and marmosets (Challitrix jacchus) expressing either wild type (WT) or mutant human alpha-synuclein develop motor deficits, LB-like inclusions in some neurons and neuronal degeneration. The effects of human alpha-synuclein were investigated in a neuronal rat cell line (B103). Plasmids expressing WT and mutant human alpha-synuclein regulated by the cytomegalovirus (CMV) promoter were prepared and used for creating stably transfected neuronal rat cell lines. For localizing alpha-synuclein expression, stably transfected neuronal rat cell lines, expressing alpha-synuclein enhanced green fluorescent protein fusion proteins, regulated by either the CMV or the human platelet-derived growth factor ss promoter were generated. Over-expression of WT and A53T alpha-synuclein regulated by CMV promoter in stable transfectants resulted in formation of alpha-synuclein-immunopositive inclusion-like structures and mitochondrial alterations. Taken together, these results suggest that abnormal accumulation of alpha-synuclein could lead to mitochondrial alterations that might result in oxidative stress and eventually, cell death.

Establishment and characterization of three novel cell lines - P-STS, L-STS, H-STS - derived from a human metastatic midgut carcinoid

Carcinoids are rare tumors derived from enterochromaffin (EC) cells of the embryonic neural crest. They have malignant potential and their incidence is steadily increasing. The only curative treatment option is surgery. We have focused on cultivation of human neuroendocrine tumors (NET) as relevant models for the study of potential therapy. Only a few cell lines from human carcinoids have been established so far, among them our earlier KRJ-I cell line from a human ileal carcinoid. The reason for the poor success in establishing carcinoid cell lines is due to the small amount of tissue available and the low mitotic activity in primary cultures. We have successfully established three continuously growing cell lines from tissue obtained from a metastatic human carcinoid of the terminal ileum (midgut carcinoid): P-STS was derived from the primary tumor, L-STS from a lymph node metastasis and H-STS from a hepatic metastasis. Immunocytochemistry proved the maintenance of characteristic neuroendocrine properties. Electron microscopy confirmed the presence of neuroendocrine granules. The three cell lines were tumorigenous in SCID-mice. Cytogenetic analyses revealed clonal tetraploidy, inversion and deletion in chromosome 18q, and non-clonal numerical and structural aberrations. Array CGH did not show notable imbalances. Mutation screening of P-STS excluded a MEN1-gene-associated genetic predisposition with high probability. The novel cell lines P-STS, L-STS and H-STS may be useful in vitro and in vivo models for further studies of biological characteristics and the development of new therapeutic agents.

KRJ-I and BON cell lines: defining an appropriate enterochromaffin cell neuroendocrine tumor model

BACKGROUND

Neuroendocrine tumors (NETs) of the gastrointestinal (GI) system are increasing in incidence with minimal improvement in prognosis. Although the cell of origin has been identified as the enterochromaffin (EC) cell, its secretory and proliferative regulation has not been defined at a mechanistic level. To date, the BON cell line has been the most widely used in vitro EC cell model despite its pancreatic origin. Using whole-genome mathematical analysis as well as secretory and proliferative studies, we compared the BON cell line to the small intestine (SI) EC cell-derived NET cell line, KRJ-I, to assess individual cell line validity and applicability for the investigation of GI-NET disease.

METHODS AND RESULTS

Principal component analysis and ANOVA of KRJ-I and BON transcriptomes (U133 Plus 2) identified substantially different (<10%) overlap in transcripts with minimal (R(2) = 0.24) correlation in gene expression profiles. RT-PCR detected large variability (>12%) in neuroendocrine (NE) marker transcripts in the BON cell line and the absence of Tph-2, DDC, TGFbetaR2, and M3 transcripts in KRJ-I. The KRJ-I cell line secreted serotonin (5-HT) in response to isoproterenol (EC(50) = 100 nM), noradrenaline (EC(50) = 1.7 nM), and pituitary adenylate cyclase (PACAP, EC(50) = 0.03 nM). Cholecystokinin (IC(50) = 430 nM), somatostatin (IC(50) = 400 nM), acetylcholine (IC(50) = 3.7 nM), and gamma-aminobutyric acid A (GABA(A), IC(50) = 2 nM) all inhibited 5-HT release, while gastrin and bombesin had no effect. 5-HT secretion in the BON cell line was stimulated by isoproterenol (EC(50) = 900 nM), noradrenaline (EC(50) = 20 nM), cholecystokinin (EC(50) = 130 nM), PACAP (EC(50) = 0.12 nM), bombesin (EC(50) = 15 nM), and acetylcholine (EC(50) = 0.2 nM). It was inhibited by somatostatin (IC(50) = 300 nM) but not GABA(A). KRJ-I responded with proliferation to connective tissue growth factor (CTGF, EC(50) = 0.002 ng/ml), transforming growth factor-alpha (TGFalpha, EC(50) = 0.63 ng/ml) and transforming growth factor-beta (TGFbeta, EC(50) = 0.63 ng/ml). Epidermal growth factor (EGF) and somatostatin had no significant effect. BON cell proliferation was stimulated only by EGF and TGFalpha (EC(50) = 15.8 and 10 ng/ml). TGFbeta (IC(50) = 0.16 ng/ml), MZ-4-147 (IC(50) = 0.5 nM), and BIM23A761 (IC(50) = 0.06 nM) all inhibited proliferation. CTGF and somatostatin had no effect.

CONCLUSION

KRJ-I and BON cell lines demonstrate substantial differences in gene level transcripts, inconsistent receptor profile expression, wide variability in NE marker transcript levels, and significantly differential proliferative and secretory responses. Given the EC cell origin of KRJ-I, these results provide evidence that the BON cell line does not represent an EC cell system and is not a valid study model of (carcinoid) EC cell-derived NET.

Anticancer activity of novel extracts from Cautleya gracilis (Smith) Dandy: apoptosis in human medullary thyroid carcinoma cells

BACKGROUND

Medullary thyroid carcinoma (MTC) is a calcitonin-producing tumor of the thyroid arising from the parafollicular C-cells. MTC is poorly responsive to chemotherapy and radiotherapy, hence the only effective therapy is surgery. Based on this fact, alternative strategies have been sought.

MATERIALS AND METHODS

The effects of Cautleya gracilis (Smith) Dandy were investigated for the first time in three human MTC cell lines and in MTC-transplanted mice. Proliferation and viability were quantified by cell counting, WST-1 tests, and ATP luminescent cell viability assays. Apoptosis was studied by DAPI staining, flow cytometry and luminescent assays for caspases 3/7, 8 and 9.

RESULTS

A dose-dependent reduction of proliferation and an induction of apoptosis were found in all MTC cell lines, while normal fibroblasts were not impaired. Similar tumor inhibition was seen in heterotransplanted mice.

CONCLUSION

Our in vitro and in vivo findings suggest a new potential clinical effect of Cautleya.

Differential cytotoxicity of novel somatostatin and dopamine chimeric compounds on bronchopulmonary and small intestinal neuroendocrine tumor cell lines

BACKGROUND

Survival rates for gastrointestinal (GI) and bronchopulmonary (BP) neuroendocrine tumors (NETs) have not significantly altered (overall 67%, 5-year survival) in 30 years (1973-2004), whereas the incidence has increased ( approximately 1000%) in the same time frame. No effective or specific antineoplastic agent is available for treatment, although somatostatin analogs inhibit tumor secretion. Given the coexistence of somatostatin and dopamine regulatory receptors on NET cells, the antiproliferative efficacy as well as the signaling and transcriptional targets of their ligands were evaluated.

METHODS

The cytotoxic effects of 12 somatostatin/dopamine compounds were evaluated in 3 NET cell lines, and real-time polymerase chain reaction and enzyme-linked immunoadsorbent assay studies were performed to delineate antiproliferative signaling pathways.

RESULTS

The atypical BP-NET, NCI-H720, was most sensitive to the sst(5) analog BIM23206 (half-maximal concentration, 2.4 pM) and demonstrated similar sensitivity to lanreotide and the sst(2) analog BIM23120. The typical BP-NET, NCI-H727, was most sensitive to BIM23120 (0.7 nM) and to the pan-somatostatin receptor analog (BIM23A779). The GI-NET, KRJ-I, was most sensitive to sst(2,5) analogs lanreotide (1 nM) and BIM23244 (7.4 nM). Lanreotide activated extracellular signal regulated kinase-1/2 phosphorylation and p21(WAF1/CIP1) transcription, but inhibited Ki-67 transcription. NCI-H720 was most sensitive to the sst(2,5)- and D(2)-selective compound BIM23A761 (4.2 nM), as was NCI-H727 (5.5 nM). KRJ-I did not respond to any chimeric analog. BIM23A761 activated c-Jun N-terminal kinase signaling and caused inhibition of Ki-67 transcription. P21(WAF1/CIP1) transcription was activated only in NCI-H727 cells.

CONCLUSIONS

The different responses of each individual cell line suggested that NETs from different locations arising from different neuroendocrine cells may require cell-specific antiproliferative agents based on the unique receptor profile of individual lesions.

Luminal regulation of normal and neoplastic human EC cell serotonin release is mediated by bile salts, amines, tastants, and olfactants

Mechanisms by which gut luminal content regulates secretion and motility are ill understood. We evaluated whether neuroendocrine enterochromaffin (EC) cells act as luminal sensors for a wide variety of nutrients and defined the secretory mechanisms of this process. Pure (98-99%) FACS-sorted human EC cells and neoplastic EC cells (KRJ-I) were studied. RT-PCR identified transcripts for T2R1 (bitter), OR1G1 (class II olfactory) and trace amine (TAR1) G protein-coupled receptors (GPCRs) and transporters for glutamine (SNAT1/2), glucose (GLUT1/3/SGLT1), and bile salts (ABST). Glutamine and sodium deoxycholate stimulated 5-HT release (EC(50) = 0.002-0.2 microM; 2-fold release) but were 10-100 times more potent in neoplastic EC cells, which also secreted 6-13 times more 5-HT. Tastants (caffeine, tyramine, octopamine) and olfactants (thymol and eugenol) also stimulated normal and neoplastic EC cell 5-HT secretion (EC(50) = 1.2 nM to 2.1 microM and 0.05 nM to 0.1 microM release, respectively); 2-deoxyglucose and the artificial sweetener sucralose also stimulated (EC(50) = 9.2 and 0.38 nM). 5-HT release was associated with ERK phosphorylation (1.5-fold, P < 0.02) and could be inhibited by a somatostatin analog (IC(50) = 1 pM). Eleven secretory associated genes including the vesicle docking inhibitor STXBP3 were upregulated in response to glutamine and bile salt stimulation in neoplastic EC cells. Targeting STXBP3 expression by use of antisense knockdown significantly (P < 0.05) reduced 5-HT secretion. In conclusion, EC cells express GPCRs and transporters for luminal tastants, olfactants, glutamine, glucose, and bile salts. Activation includes a panel of secretory genes, ERK phosphorylation, and 5-HT secretion. Luminal EC cell regulation is likely to be as important as G cell regulation in gastric acid secretion; development of agents to target EC cell function is therefore a critical therapeutic goal.

Allogeneic tumor lysate can serve as both antigen source and protein supplementation for dendritic cell culture

BACKGROUND

Recent preclinical and clinical evidence suggests the use of allogeneic tumor as a source of antigen for DC-based immunotherapy against cancer. We hypothesized that addition of allogeneic tumor lysate to monocyte-derived DC culture could serve a dual purpose: (1) antigen source and (2) protein supplementation of DC culture media. Protein supplementation whether of known origin (human serum/plasma, fetal bovine serum, human serum albumin) or undeclared origin ("serum-free" media) is a source of variability and bias. We addressed the question whether protein supplementation can be omitted in the presence of allogeneic tumor lysate.

MATERIALS AND METHODS

Human DC cultured in the presence of lysate from medullary thyroid carcinoma (MTC) cell line SHER-I (TuLy-DC) and DC pulsed with the same lysate but cultured in the presence of FBS (FBS-DC) were assessed for morphology, phenotype, maturation and functional properties.

RESULTS

In comparison of FBS-DC/TuLy-DC no significant differences in morphology, phenotype and maturation could be detected. Both culture conditions produced CD1a(high), CD14(low) DC with high expression of costimulatory molecules and CD83 upon stimulation. TuLy-DC gave significantly better yields and produced more IL12p70. DC showed high (allo)stimulatory capacity toward T-cells. TuLy-DC induced more intracellular IFNgamma in CD8+T-cells of vaccinated MTC patients. Both types of DC induced killing of SHER-I after short in vitro restimulation. Tumor lysate from SHER-I can substitute for further protein supplementation in DC culture. Allogeneic tumor lysates should be taken into consideration as both source of antigen and protein supplementation in monocyte-derived DC culture.

Inhibition of proliferation of small intestinal and bronchopulmonary neuroendocrine cell lines by using peptide analogs targeting receptors

BACKGROUND

Currently, no consistently effective therapy is available to inhibit cell proliferation or metastasis of neuroendocrine tumor (NET) disease. The effects of 4 novel peptides were analyzed: a targeted cytotoxic analog of luteinizing hormone-releasing hormone (LH-RH) analog (AN-152), a targeted cytotoxic analog of somatostatin (AN-238), and 2 antagonists of growth hormone-releasing hormone (GH-RH) on 3 NET (carcinoid) cell lines that expressed respective peptide receptors.

METHODS

The effects of the compounds were evaluated on cell proliferation in vitro using MTT uptake and Ki67 expression, apoptosis (caspase 3 expression and activity), and cell cycle parameters (DNA distribution).

RESULTS

Proliferation of the LH-RH receptor-expressing lung NET, NCI-H720 line, was inhibited 2-fold by AN-152 containing doxorubicin compared with the chemotherapy alone (IC50 of 9.1 nM vs 24 nM). This was associated with a reduction in Ki67 transcript and an increase in both caspase 3 mRNA levels and activity. Proliferation of the GH-RH receptor expressing lung NET, NCI-H727 line, was inhibited by both GH-RH antagonists, the effects being mediated through changes in Ki67 expression, but not in caspase 3-mediated apoptosis. The small intestinal NET, KRJ-I line, was 8x more sensitive to inhibition by AN-238 than to 2-pyrolino-doxorubicin, reflected by increased caspase 3 transcript as well as activity. AN-238-mediated growth inhibition culminated in complete G1 arrest.

CONCLUSIONS

The data demonstrate GH-RH antagonists or peptide-linked antineoplastic agents such as AN-152 and AN-238 are effective inhibitors of NET proliferation in vitro. Because peptide receptors such as those for GH-RH, LH-RH, and SST subtypes are commonly expressed by NETs, the development of antineoplastic agents targeted to specific tumor receptors may provide a more efficacious strategy than systemic chemotherapeutic agents currently in use.