The Effect of Transforming Growth Factor β on Human Neuroendocrine Tumor BON Cell Proliferation and Differentiation Is Mediated through Somatostatin Signaling

Characterization of Epithelial-Mesenchymal and Neuroendocrine Differentiation States in Pancreatic and Small Cell Ovarian Tumor Cells and Their Modulation by TGF-β1 and BMP-7

Pancreatic ductal adenocarcinoma (PDAC) has an extremely poor prognosis, due in part to early invasion and metastasis, which in turn involves epithelial-mesenchymal transition (EMT) of the cancer cells. Prompted by the discovery that two PDAC cell lines of the quasi-mesenchymal subtype (PANC-1, MIA PaCa-2) exhibit neuroendocrine differentiation (NED), we asked whether NED is associated with EMT. Using real-time PCR and immunoblotting, we initially verified endogenous expressions of various NED markers, i.e., chromogranin A (CHGA), synaptophysin (SYP), somatostatin receptor 2 (SSTR2), and SSTR5 in PANC-1 and MIA PaCa-2 cells. By means of immunohistochemistry, the expressions of CHGA, SYP, SSTR2, and the EMT markers cytokeratin 7 (CK7) and vimentin could be allocated to the neoplastic ductal epithelial cells of pancreatic ducts in surgically resected tissues from patients with PDAC. In HPDE6c7 normal pancreatic duct epithelial cells and in epithelial subtype BxPC-3 PDAC cells, the expression of CHGA, SYP, and neuron-specific enolase 2 (NSE) was either undetectable or much lower than in PANC-1 and MIA PaCa-2 cells. Parental cultures of PANC-1 cells exhibit EM plasticity (EMP) and harbor clonal subpopulations with both M- and E-phenotypes. Of note, M-type clones were found to display more pronounced NED than E-type clones. Inducing EMT in parental cultures of PANC-1 cells by treatment with transforming growth factor-β1 (TGF-β1) repressed epithelial genes and co-induced mesenchymal and NED genes, except for SSTR5. Surprisingly, treatment with bone morphogenetic protein (BMP)-7 differentially affected gene expressions in PANC-1, MIA PaCa-2, BxPC-3, and HPDE cells. It synergized with TGF-β1 in the induction of vimentin, SNAIL, SSTR2, and NSE but antagonized it in the regulation of CHGA and SSTR5. Phospho-immunoblotting in M- and E-type PANC-1 clones revealed that both TGF-β1 and, surprisingly, also BMP-7 activated SMAD2 and SMAD3 and that in M- but not E-type clones BMP-7 was able to dramatically enhance the activation of SMAD3. From these data, we conclude that in EMT of PDAC cells mesenchymal and NED markers are co-regulated, and that mesenchymal-epithelial transition (MET) is associated with a loss of both the mesenchymal and NED phenotypes. Analyzing NED in another tumor type, small cell carcinoma of the ovary hypercalcemic type (SCCOHT), revealed that two model cell lines of this disease (SCCOHT-1, BIN-67) do express CDH1, SNAI1, VIM, CHGA, SYP, ENO2, and SSTR2, but that in contrast to BMP-7, none of these genes was transcriptionally regulated by TGF-β1. Likewise, in BIN-67 cells, BMP-7 was able to reduce proliferation, while in SCCOHT-1 cells this occurred only upon combined treatment with TGF-β and BMP-7. We conclude that in PDAC-derived tumor cells, NED is closely linked to EMT and TGF-β signaling, which may have implications for the therapeutic use of TGF-β inhibitors in PDAC management.

Oncogenic pathway signatures predict the risk of progression and recurrence in well-differentiated pancreatic neuroendocrine tumors

BACKGROUND

Pancreatic neuroendocrine tumors (pNETs) are genomically diverse tumors. The management of newly diagnosed well-differentiated pNETs is limited by a lack of sensitivity of existing biomarkers for prognostication. Our goal was to investigate the potential utility of genetic markers as a predictor of progression-free survival (PFS) and recurrence-free survival (RFS).

METHODS

Whole-exome sequencing of resected well-differentiated, low and intermediate-grade (G1 and G2) pNETs and normal adjacent tissue from patients who underwent resection from 2005 to 2015 was performed. Genetic alterations were classified using pan-genomic and oncogenic pathway classifications. Additional samples with genetic and clinicopathologic data available were obtained from the publicly available International Cancer Genome Consortium (ICGC) database and included in the analysis. The prognostic relevance of these genomic signatures on PFS and RFS was analyzed.

RESULTS

Thirty-one patients who underwent resection for pNET were identified. Genomic analysis of mutational, copy number, cytogenetic, and complex phenomena revealed similar patterns to prior studies of pNETs with relatively few somatic gene mutations but numerous instances of copy number changes. Analysis of genomic and clinicopathologic outcomes using the combined data from our study as well as the ICGC pNET cohort (n = 124 patients) revealed that the recurrent pattern of whole chromosome loss (RPCL) and metastatic disease were independently associated with disease progression. When evaluating patients with local disease at the time of resection, RPCL and alterations in the TGFβ oncogenic pathway were independently associated with the risk of recurrence.

CONCLUSIONS

Well-differentiated pNETs are genomically diverse tumors. Pathway signatures may be prognostic for predicting disease progression and recurrence.

Differential Effects of Somatostatin, Octreotide, and Lanreotide on Neuroendocrine Differentiation and Proliferation in Established and Primary NET Cell Lines: Possible Crosstalk with TGF-β Signaling

GEP-NETs are heterogeneous tumors originating from the pancreas (panNET) or the intestinal tract. Only a few patients with NETs are amenable to curative tumor resection, and for most patients, only palliative treatments to successfully control the disease or manage symptoms remain, such as with synthetic somatostatin (SST) analogs (SSAs), such as octreotide (OCT) or lanreotide (LAN). However, even cells expressing low levels of SST receptors (SSTRs) may exhibit significant responses to OCT, which suggests the possibility that SSAs signal through alternative mechanisms, e.g., transforming growth factor (TGF)-β. This signaling mode has been demonstrated in the established panNET line BON but not yet in other permanent (i.e., QGP) or primary (i.e., NT-3) panNET-derived cells. Here, we performed qPCR, immunoblot analyses, and cell counting assays to assess the effects of SST, OCT, LAN, and TGF-β1 on neuroendocrine marker expression and cell proliferation in NT-3, QGP, and BON cells. SST and SSAs were found to regulate a set of neuroendocrine genes in all three cell lines, with the effects of SST, mainly LAN, often differing from those of OCT. However, unlike NT-3 cells, BON cells failed to respond to OCT with growth arrest but paradoxically exhibited a growth-stimulatory effect after treatment with LAN. As previously shown for BON, NT-3 cells responded to TGF-β1 treatment with induction of expression of SST and SSTR2/5. Of note, the ability of NT-3 cells to respond to TGF-β1 with upregulation of the established TGF-β target gene SERPINE1 depended on cellular adherence to a collagen-coated matrix. Moreover, when applied to NT-3 cells for an extended period, i.e., 14 days, TGF-β1 induced growth suppression as shown earlier for BON cells. Finally, next-generation sequencing-based identification of microRNAs (miRNAs) in BON and NT-3 revealed that SST and OCT impact positively or negatively on the regulation of specific miRNAs. Our results suggest that primary panNET cells, such as NT-3, respond similarly as BON cells to SST, SSA, and TGF-β treatment and thus provide circumstantial evidence that crosstalk of SST and TGF-β signaling is not confined to BON cells but is a general feature of panNETs.

Inflammation Related to Obesity in the Etiopathogenesis of Gastroenteropancreatic Neuroendocrine Neoplasms

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) are rare neoplasms, which, due to their heterogeneous nature, non-specific symptoms, and lack of specific tumor markers pose many diagnostic and clinical challenges. In recent years, the effectiveness of GEP-NEN diagnosis has increased, which is probably associated with the greater availability of diagnostic tests and the cooperation of many experienced specialists in various scientific disciplines. In addition to the possible genetic etiology, the cause of GEP-NET development is not fully understood. Inflammation and obesity are known risks that contribute to the development of many diseases. Chronic inflammation accompanying obesity affects the hormonal balance and cell proliferation and causes the impairment of the immune system function, leading to neoplastic transformation. This review explores the role of inflammation and obesity in GEP-NETs. The exact mechanisms inducing tumor growth are unknown; however, the profile of inflammatory factors released in the GEP-NET tumor microenvironment is responsible for the progression or inhibition of tumor growth. Both the excess of adipose tissue and the impaired function of the immune system affect not only the initiation of cancer but also reduce the comfort and lifetime of patients.

Establishment and characterization of the third non-functional human pancreatic neuroendocrine tumor cell line

The mechanisms of neuroendocrine tumor (NET) were still poorly understood, largely due to the lack of preclinical models of neuroendocrine neoplasms. Herein, we established and characterized SPNE1 cell lines from primary pancreatic NET tissue obtained from a 44-year-old female. Neuroendocrine character of SPNE1 was compared with existing non-functional cell lines BON1 and QGP1, and the results indicated expressions of multiple NET-specific markers in SPNE1 were higher relative to BON1 and QGP1. The growth character measured by Ki67 labeling index, cell cycle analysis, and 3D matrigel spheroid essay indicated that the proliferative rate of SPNE1 was lower than that of BON1 and QGP1. SPNE1 also was characterized with cancer stemness because of the higher proportion of CD44 + and CD117 + subpopulations relative to BON1, whereas it was similar to that of QGP1. Interestingly, SPNE1 highly expressed somatostatin receptors (SSTR2 and SSTR5) and angiogenic factors (VEGF1). SPNE1 had sensitive response to the four clinical treatments including tyrosine kinase inhibitor (TKI), mTOR inhibitors, somatostatin analogs (SSA), chemotherapy, which was similar to the BON1 and QGP1. Subcutaneous transplantations of SPNE1 also present the tumorigenicity, and neuroendocrine marker expression of xenograft tumors resembled the original human NET tissue. Then, we found a total of 8 common mutation in BON1, QGP1 and SPNE1 included CROCC, FAM135A, GPATCH4, CTBP2, FBXL14, HERC2, HYDIN, and PABPC3 using whole-exome sequencing (WES), and more neuroendocrine-related functional processes were enriched based on the private mutation genes in SPNE1, such as neuron migration, insulin secretion, and neuron to neuron synapse. In brief, SPNE1 could be used as a relevant model to study pancreatic NET biology and to develop novel treatment options.

Pancreatic Neuroendocrine Tumors: Molecular Mechanisms and Therapeutic Targets

Pancreatic neuroendocrine tumors (pNETs) are unique, slow-growing malignancies whose molecular pathogenesis is incompletely understood. With rising incidence of pNETs over the last four decades, larger and more comprehensive 'omic' analyses of patient tumors have led to a clearer picture of the pNET genomic landscape and transcriptional profiles for both primary and metastatic lesions. In pNET patients with advanced disease, those insights have guided the use of targeted therapies that inhibit activated mTOR and receptor tyrosine kinase (RTK) pathways or stimulate somatostatin receptor signaling. Such treatments have significantly benefited patients, but intrinsic or acquired drug resistance in the tumors remains a major problem that leaves few to no effective treatment options for advanced cases. This demands a better understanding of essential molecular and biological events underlying pNET growth, metastasis, and drug resistance. This review examines the known molecular alterations associated with pNET pathogenesis, identifying which changes may be drivers of the disease and, as such, relevant therapeutic targets. We also highlight areas that warrant further investigation at the biological level and discuss available model systems for pNET research. The paucity of pNET models has hampered research efforts over the years, although recently developed cell line, animal, patient-derived xenograft, and patient-derived organoid models have significantly expanded the available platforms for pNET investigations. Advancements in pNET research and understanding are expected to guide improved patient treatments.

Genetic Drivers of Ileal Neuroendocrine Tumors

Simple Summary

Although ileal neuroendocrine tumors are the most common tumors of the small intestine, they are not well-defined at the genetic level. Unlike most cancers, they have an unusually low number of mutations, and also lack recurrently mutated genes. Moreover ileal NETs have been difficult to study in the laboratory because there were no animal models and because cell lines were generally unavailable. But recent advances, including the first ileal NET mouse model as well as methods for culturing patient tumor samples, have been described and have already helped to identify IGF2 and CDK4 as two of the genetic drivers for this tumor type. These advances may help in the development of new treatments for patients.

Abstract

The genetic causes of ileal neuroendocrine tumors (ileal NETs, or I-NETs) have been a mystery. For most types of tumors, key genes were revealed by large scale genomic sequencing that demonstrated recurrent mutations of specific oncogenes or tumor suppressors. In contrast, genomic sequencing of ileal NETs demonstrated a distinct lack of recurrently mutated genes, suggesting that the mechanisms that drive the formation of I-NETs may be quite different than the cell-intrinsic mutations that drive the formation of other tumor types. However, recent mouse studies have identified the IGF2 and RB1 pathways in the formation of ileal NETs, which is supported by the subsequent analysis of patient samples. Thus, ileal NETs no longer appear to be a cancer without genetic causes.

TGF-β1/Smad2/3 signaling pathway modulates octreotide antisecretory and antiproliferative effects in pituitary somatotroph tumor cells

Octreotide (OCT) is used to inhibit hormone secretion and growth in somatotroph tumors, although a significant percentage of patients are resistant. It has also been tested in nonfunctioning (NF) tumors but with poor results, with these outcomes having been associated with SSTR2 levels and impaired signaling. We investigated whether OCT inhibitory effects can be improved by TGF-β1 in functioning and nonfunctioning somatotroph tumor cells. OCT effects on hormone secretion and proliferation were analyzed in the presence of TGF-β1 in WT and SSTR2-overexpressing secreting GH3 and silent somatotroph tumor cells. The mechanism underlying these effects was assessed by studying SSTR and TGFβR signaling pathways mediators. In addition, we analyzed the effects of OCT/TGF-β1 treatment on tumor growth and cell proliferation in vivo. The inhibitory effects of OCT on GH- and PRL-secretion and proliferation were improved in the presence of TGF-β1, as well as by SSTR2 overexpression. The OCT/TGF-β1 treatment induced downregulation of pERK1/2 and pAkt, upregulation of pSmad3, and inhibition of cyclin D1. In vivo experiments showed that OCT in the presence of TGF-β1 blocked tumor volume growth, decreased cell proliferation, and increased tumor necrosis. These results indicate that SSTR2 levels and the stimulation of TGF-β1/TGFβR/Smad2/3 pathway are important for strengthening the antiproliferative and antisecretory effects of OCT.

Modelling Pancreatic Neuroendocrine Cancer: From Bench Side to Clinic

Pancreatic neuroendocrine tumours (pNETs) are a heterogeneous group of epithelial tumours with neuroendocrine differentiation. Although rare (incidence of <1 in 100,000), they are the second most common group of pancreatic neoplasms after pancreatic ductal adenocarcinoma (PDAC). pNET incidence is however on the rise and patient outcomes, although variable, have been linked with 5-year survival rates as low as 40%. Improvement of diagnostic and treatment modalities strongly relies on disease models that reconstruct the disease ex vivo. A key constraint in pNET research, however, is the absence of human pNET models that accurately capture the original tumour phenotype. In attempts to more closely mimic the disease in its native environment, three-dimensional culture models as well as in vivo models, such as genetically engineered mouse models (GEMMs), have been developed. Despite adding significant contributions to our understanding of more complex biological processes associated with the development and progression of pNETs, factors such as ethical considerations and low rates of clinical translatability limit their use. Furthermore, a role for the site-specific extracellular matrix (ECM) in disease development and progression has become clear. Advances in tissue engineering have enabled the use of tissue constructs that are designed to establish disease ex vivo within a close to native ECM that can recapitulate tumour-associated tissue remodelling. Yet, such advanced models for studying pNETs remain underdeveloped. This review summarises the most clinically relevant disease models of pNETs currently used, as well as future directions for improved modelling of the disease.

The tumor immune microenvironment in gastroenteropancreatic neuroendocrine neoplasms

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) are a group of rare tumors that are increasing in prevalence. The complex tumor immune microenvironment (TIME) plays an important role in tumor development and the response to immunotherapy but is poorly understood. In this review, the components of the TIME are described in detail, including discussion about infiltrating immune cells, the immune checkpoint system, the cytokine and chemokine milieu, and immunomodulatory factors. Moreover, a comparison between TIMEs among different types of GEP-NENs and the interplay among the TIME, tumor cells, and the stromal microenvironment is described. Novel treatment options for GEP-NENs and potential biomarkers for the immune response are also characterized. We provide a comprehensive generalized review of the TIME that can inform GEP-NEN treatment strategies.

Relationship between various cytokines implicated in asthma

Asthma is a complex disorder involving immunologic, environmental, genetic and other factors. Today, asthma is the most common disease encountered in clinical medicine in both children and adults worldwide. Asthma is characterized by increased responsiveness of the tracheobronchial tree resulting in chronic swelling and inflammation of the airways recognized to be controlled by the T-helper 2 (Th2) lymphocytes, which secrete cytokines to increase the production of IgE by B cells. There are many cytokines implicated in the development of the chronic inflammatory processes that are often observed in asthma. Ultimately, these cytokines cause the release of mediators such as histamine and leukotrienes (LT), which in turn promote airway remodeling, bronchial hyperresponsiveness and bronchoconstriction. The CD4⁺ T-lymphocytes from the airways of asthmatics express a panel of cytokines that represent the Th2 cells. The knowledge derived from numerous experimental and clinical studies have allowed physicians and scientists to understand the normal functions of these cytokines and their roles in the pathogenesis of asthma. The main focus of this review is to accentuate the relationship between various cytokines implicated in human asthma. However, some key findings from animal models will be highlighted to support the discoveries from clinical studies.

Sustained somatostatin gene expression reverses kindling-induced increases in the number of dividing Type-1 neural stem cells in the hippocampi of behaviorally responsive rats

Neurogenesis persists throughout life in the hippocampi of all mammals, including humans. In the healthy hippocampus, relatively quiescent Type-1 neural stem cells (NSCs) can give rise to more proliferative Type-2a neural progenitor cells (NPCs), which generate neuronal-committed Type-2b NPCs that mature into Type-3 neuroblasts. Many Type-3 neuroblasts survive and mature into functionally integrated granule neurons over several weeks. In kindling models of epilepsy, neurogenesis is drastically upregulated and many new neurons form aberrant connections that could support epileptogenesis and/or seizures. We have shown that sustained vector-mediated hippocampal somatostatin (SST) expression can both block epileptogenesis and reverse seizure susceptibility in fully kindled rats. Here we test whether adeno-associated virus (AAV) vector-mediated sustained SST expression modulates hippocampal neurogenesis and microglial activation in fully kindled rats. We found significantly more dividing Type-1 NSCs and a corresponding increased number of surviving new neurons in the hippocampi of kindled versus sham-kindled rats. Increased numbers of activated microglia were found in the granule cell layer and hilus of kindled rats at both time points. After intrahippocampal injection with either eGFP or SST-eGFP vector, we found similar numbers of dividing Type-1 NSCs and -2 NPCs and surviving BrdU⁺ neurons and glia in the hippocampi of kindled rats. Upon observed variability in responses to SST-eGFP (2/4 rats exhibited Grade 0 seizures in the test session), we conducted an additional experiment. We found significantly fewer dividing Type-1 NSCs in the hippocampi of SST-eGFP vector-treated responder rats (5/13 rats) relative to SST-eGFP vector-treated non-responders and eGFP vector-treated controls that exhibited high-grade seizures on the test session. The number of activated microglia was upregulated in the GCL and hilus of kindled rats, regardless of vector treatment. These data support the hypothesis that sustained SST expression exerts antiepileptic effects potentially through normalization of neurogenesis and suggests that abnormally high proliferating Type-1 NSC numbers may be a cellular mechanism of epilepsy.

The variant at TGFBRAP1 is significantly associated with type 2 diabetes mellitus and affects diabetes-related miRNA expression

While the transforming growth factor-β1 (TGF-β1) regulates the growth and proliferation of pancreatic β-cells, its receptors trigger the activation of Smad network and subsequently induce the insulin resistance. A case-control was conducted to evaluate the associations of the polymorphisms of TGF-β1 receptor-associated protein 1 (TGFBRAP1) and TGF-β1 receptor 2 (TGFBR2) with type 2 diabetes mellitus (T2DM), and its genetic effects on diabetes-related miRNA expression. miRNA microarray chip was used to screen T2DM-related miRNA and 15 differential expressed miRNAs were further validated in 75 T2DM and 75 normal glucose tolerance (NGT). The variation of rs2241797 (T/C) at TGFBRAP1 showed significant association with T2DM in case-control study, and the OR (95% CI) of dominant model for cumulative effects was 1.204 (1.060-1.370), Bonferroni corrected P < 0.05. Significant differences in the fast glucose and HOMA-β indices were observed amongst the genotypes of rs2241797. The expression of has-miR-30b-5p and has-miR-93-5p was linearly increased across TT, TC, and CC genotypes of rs2241797 in NGT, Ptrend values were 0.024 and 0.016, respectively. Our findings suggest that genetic polymorphisms of TGFBRAP1 may contribute to the genetic susceptibility of T2DM by mediating diabetes-related miRNA expression.

M3 muscarinic acetylcholine receptors regulate epithelial-mesenchymal transition, perineural invasion, and migration/metastasis in cholangiocarcinoma through the AKT pathway

Background

Cholangiocarcinoma is a highly malignant tumor type that is not sensitive to radiotherapy or chemotherapy due to aggressive perineural invasion and metastasis. Unfortunately, the mechanisms underlying these processes and the signaling factors involved are largely unknown. In this study, we analyzed the role of M3 muscarinic acetylcholine receptors (M3-mAChR) in cell migration, perineural invasion, and metastasis during cholangiocarcinoma.

Methods

We assessed 60 human cholangiocarcinoma tissue samples and 30 normal biliary tissues. Immunohistochemical staining was used to detect M3-mAChR expression and the relationship between expression and clinical prognosis was evaluated. The biological functions of M3-mAChR in cholangiocarcinoma cell migration, perineural invasion, and epithelial–mesenchymal transition (EMT) were investigated using the human cholangiocarcinoma cell lines FRH0201 and RBE in conjunction with various techniques, including agonist/antagonist treatment, RNA interference, M3-mAChR overexpression, dorsal root ganglion co-culturing, immunohistochemistry, western blotting, etc.

Results

M3-mAChR were highly expressed in cholangiocarcinoma tissue and expression was closely related to differentiation and lymphatic metastasis, affecting patient survival. Treatment with the M3-mAChR agonist pilocarpine and M3-mAChR overexpression significantly promoted migration and perineural invasion, while the M3-mAChR antagonist atropine blocked these effects. Similarly, M3-mAChR knock-down also weakened cell migration and perineural invasion. The expression of phosphatase and tensin homolog, AKT, E-cadherin, vimentin, and Snail, which are components of the phosphatidylinositol 3-kinase/AKT signaling pathway and EMT, were altered by pilocarpine, and these effects were again blocked by atropine. Notably, AKT knock-down decreased M3-mAChR expression and reversed the downstream effects of this receptor.

Conclusions

M3-mAChR are involved in tumor cell migration, perineural invasion, and EMT during cholangiocarcinoma, and these effects are modulated via the AKT signaling pathway.

Role of the tumor microenvironment in digestive neuroendocrine tumors

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) represent a group of heterogeneous tumors whose incidence increased over the past few years. Around half of patients already present with metastatic disease at the initial diagnosis. Despite extensive efforts, cytotoxic and targeted therapies have provided only limited efficacy for patients with metastatic GEP-NETs, mainly due to the development of a certain state of resistance. One factor contributing to both the failure of systemic therapies and the emergence of an aggressive tumor phenotype may be the tumor microenvironment (TME), comprising dynamic and adaptative assortment of extracellular matrix components and non-neoplastic cells, which surround the tumor niche. Accumulating evidence shows that the TME can simultaneously support both tumor growth and metastasis and contribute to a certain state of resistance to treatment. In this review, we summarize the current knowledge of the TME of GEP-NETs and discuss the current therapeutic agents that target GEP-NETs and those that could be of interest in the (near) future.

Targeting Somatostatin Receptors By Functionalized Mesoporous Silica Nanoparticles - Are We Striking Home?

The concept of delivering nanoformulations to desired tissues by means of targeting membrane receptors of high local abundance by ligands anchored to the nanocarrier has gained a lot of attention over the last decade. Currently, there is no unanimous opinion on whether surface functionalization of nanocarriers by targeting ligands translates into any real benefit in terms of pharmacokinetics or treatment outcomes. Having examined the published nanocarriers designed to engage with somatostatin receptors, we realized that in the majority of cases targetability claims were not supported by solid evidence of targeting ligand-targeted receptor coupling, which is the very crux of a targetability concept. Here, we present an approach to characterize targetability of mesoporous silica-based nanocarriers functionalized with ligands of somatostatin receptors. The targetability proof in our case comes from a functional assay based on a genetically-encoded cAMP probe, which allows for real-time capture of receptor activation in living cells, triggered by targeting ligands on nanoparticles. We elaborate on the development and validation of the assay, highlighting the power of proper functional tests in the characterization pipeline of targeted nanoformulations.

Arachidonic acid-induced Ca2+ entry and migration in a neuroendocrine cancer cell line

Background

Store-operated Ca²⁺ entry (SOCE) has been implicated in the migration of some cancer cell lines. The canonical SOCE is defined as the Ca²⁺ entry that occurs in response to near-maximal depletion of Ca²⁺ within the endoplasmic reticulum. Alternatively, arachidonic acid (AA) has been shown to induce Ca²⁺ entry in a store-independent manner through Orai1/Orai3 hetero-multimeric channels. However, the role of this AA-induced Ca²⁺ entry pathway in cancer cell migration has not been adequately assessed.

Methods

The present study investigated the involvement of AA-induced Ca²⁺ entry in migration in BON cells, a model gastro-enteropancreatic neuroendocrine tumor (GEPNET) cell line using pharmacological and gene knockdown methods in combination with live cell fluorescence imaging and standard migration assays.

Results

We showed that both the store-dependent and AA-induced Ca²⁺ entry modes could be selectively activated and that exogenous administration of AA resulted in Ca²⁺ entry that was pharmacologically distinct from SOCE. Also, whereas homomeric Orai1-containing channels appeared to largely underlie SOCE, the AA-induced Ca²⁺ entry channel required the expression of Orai3 as well as Orai1. Moreover, we showed that AA treatment enhanced the migration of BON cells and that this migration could be abrogated by selective inhibition of the AA-induced Ca²⁺ entry.

Conclusions

Taken together, these data revealed that an alternative Orai3-dependent Ca²⁺ entry pathway is an important signal for GEPNET cell migration.

Electronic supplementary material

The online version of this article (10.1186/s12935-018-0529-8) contains supplementary material, which is available to authorized users.

Establishment of the First Well-differentiated Human Pancreatic Neuroendocrine Tumor Model

Clinical options for systemic therapy of neuroendocrine tumors (NET) are limited. Development of new drugs requires suitable representative in vitro and in vivo model systems. So far, the unavailability of a human model with a well-differentiated phenotype and typical growth characteristics has impaired preclinical research in NET. Herein, we establish and characterize a lymph node-derived cell line (NT-3) from a male patient with well-differentiated pancreatic NET. Neuroendocrine differentiation and tumor biology was compared with existing NET cell lines BON and QGP-1. In vivo growth was assessed in a xenograft mouse model. The neuroendocrine identity of NT-3 was verified by expression of multiple NET-specific markers, which were highly expressed in NT-3 compared with BON and QGP-1. In addition, NT-3 expressed and secreted insulin. Until now, this well-differentiated phenotype is stable since 58 passages. The proliferative labeling index, measured by Ki-67, of 14.6% ± 1.0% in NT-3 is akin to the original tumor (15%-20%), and was lower than in BON (80.6% ± 3.3%) and QGP-1 (82.6% ± 1.0%). NT-3 highly expressed somatostatin receptors (SSTRs: 1, 2, 3, and 5). Upon subcutaneous transplantation of NT-3 cells, recipient mice developed tumors with an efficient tumor take rate (94%) and growth rate (139% ± 13%) by 4 weeks. Importantly, morphology and neuroendocrine marker expression of xenograft tumors resembled the original human tumor.Implications: High expression of somatostatin receptors and a well-differentiated phenotype as well as a slow growth rate qualify the new cell line as a relevant model to study neuroendocrine tumor biology and to develop new tumor treatments. Mol Cancer Res; 16(3); 496-507. ©2018 AACR.

Tumor microenvironment of gastroenteropancreatic neuroendocrine neoplasms

Tumor microenvironment provides a unique environment for tumor development, where the biology behavior of tumor cells is regulated not only by their genetics but also by the surrounding environment. Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) originating from the neuroendocrine cells of the gastroenteropancreatic system are characterized by a propensity to secrete a variety of peptide hormones and biogenic amines. The symptoms of GEP-NENs at early stages are often atypical, thus delaying the diagnosis. A further understanding of the pathobiology of GEP-NENs on the basis of studies on GEP-NENs tumor microenvironment can provide new evidence for clinical diagnosis and treatment. This review aims to introduce different cell types, several proteins involved in extracellular matrix remodeling, some growth factors, and chromogranin A (CgA) in the tumor microenvironment of GEP-NENs, in order to highlight their indispensable roles in GEP-NENs progression.

Induced differentiation of human gingival fibroblasts into VSMC-like cells

Vascular smooth muscle cells (VSMCs) are major component of the vascular wall, and they play an essential role in maintaining the basic physiological function and stable structure of the vascular wall. In the present study, human gingival fibroblasts (HGFs) were cultured and induced into VSMC-like cells in vitro to confirm that HGFs with properties of stem cells have the potential for differentiation. The epithelium isolated from patients was extracted from normal human gingiva consisting of epithelium and connective tissue. HGFs were first identified by morphological examination, as well as specific gene and protein expression, and then induced by 10ng/mL PDGF-BB combined with 2ng/mL of TGF-β1 for 28 days. After induction, ICS data indicated that induced VSMC-like cells were positive for α-SMA and SM-MHC, and IFA data showed that induced cells were positive for SM22α and Cnn1. RT-PCR results demonstrated that α-SMA and SM-MHC mRNA were specifically expressed, and myofilament-like structures also appeared in induced cells. In conclusion, the data indicated that HGFs could differentiate to VSMC-like cells with typical VSMC morphologic, ultrastructural, and immunological characteristics via induction with PDGF-BB and TGF-β1.

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 truncated isoform of somatostatin receptor5 (sst5TMD4) is associated with poorly differentiated thyroid cancer

Somatostatin receptors (ssts) are expressed in thyroid cancer cells, but their biological significance is not well understood. The aim of this study was to assess ssts in well differentiated (WDTC) and poorly differentiated thyroid cancer (PDTC) by means of imaging and molecular tools and its relationship with the efficacy of somatostatin analog treatment. Thirty-nine cases of thyroid carcinoma were evaluated (20 PDTC and 19 WDTC). Depreotide scintigraphy and mRNA levels of sst-subtypes, including the truncated variant sst5TMD4, were carried out. Depreotide scans were positive in the recurrent tumor in the neck in 6 of 11 (54%) PDTC, and in those with lung metastases in 5/11 cases (45.4%); sst5TMD4 was present in 18/20 (90%) of PDTC, being the most densely expressed sst-subtype, with a 20-fold increase in relation to sst2. In WDTC, sst2 was the most represented, while sst5TMD4 was not found; sst2 was significantly increased in PDTC in comparison to WDTC. Five depreotide positive PDTC received octreotide for 3–6 months in a pilot study with no changes in the size of the lesions in 3 of them, and a significant increase in the pulmonary and cervical lesions in the other 2. All PDTC patients treated with octreotide showed high expression of sst5TMD4. ROC curve analysis demonstrated that only sst5TMD4 discriminates between PDTC and WDTC. We conclude that sst5TMD4 is overexpressed in PDTC and may be involved in the lack of response to somatostatin analogue treatment.

Gastrointestinal hormones stimulate growth of Foregut Neuroendocrine Tumors by transactivating the EGF receptor

Foregut neuroendocrine tumors [NETs] usually pursuit a benign course, but some show aggressive behavior. The treatment of patients with advanced NETs is marginally effective and new approaches are needed. In other tumors, transactivation of the EGF receptor (EGFR) by growth factors, gastrointestinal (GI) hormones and lipids can stimulate growth, which has led to new treatments. Recent studies show a direct correlation between NET malignancy and EGFR expression, EGFR inhibition decreases basal NET growth and an autocrine growth effect exerted by GI hormones, for some NETs. To determine if GI hormones can stimulate NET growth by inducing transactivation of EGFR, we examined the ability of EGF, TGFα and various GI hormones to stimulate growth of the human foregut carcinoid,BON, the somatostatinoma QGP-1 and the rat islet tumor,Rin-14B-cell lines. The EGFR tyrosine-kinase inhibitor, AG1478 strongly inhibited EGF and the GI hormones stimulated cell growth, both in BON and QGP-1 cells. In all the three neuroendocrine cell lines studied, we found EGF, TGFα and the other growth-stimulating GI hormones increased Tyr(1068) EGFR phosphorylation. In BON cells, both the GI hormones neurotensin and a bombesin analogue caused a time- and dose-dependent increase in EGFR phosphorylation, which was strongly inhibited by AG1478. Moreover, we found this stimulated phosphorylation was dependent on Src kinases, PKCs, matrix metalloproteinase activation and the generation of reactive oxygen species. These results raise the possibility that disruption of this signaling cascade by either EGFR inhibition alone or combined with receptor antagonists may be a novel therapeutic approach for treatment of foregut NETs/PETs.

The somatostatin analogue octreotide inhibits growth of small intestine neuroendocrine tumour cells

Octreotide is a widely used synthetic somatostatin analogue that significantly improves the management of neuroendocrine tumours (NETs). Octreotide acts through somatostatin receptors (SSTRs). However, the molecular mechanisms leading to successful disease control or symptom management, especially when SSTRs levels are low, are largely unknown. We provide novel insights into how octreotide controls NET cells. CNDT2.5 cells were treated from 1 day up to 16 months with octreotide and then were profiled using Affymetrix microarray analysis. Quantitative real-time PCR and western blot analyses were used to validate microarray profiling in silico data. WST-1 cell proliferation assay was applied to evaluate cell growth of CNDT2.5 cells in the presence or absence of 1 µM octreotide at different time points. Moreover, laser capture microdissected tumour cells and paraffin embedded tissue slides from SI-NETs at different stages of disease were used to identify transcriptional and translational expression. Microarrays analyses did not reveal relevant changes in SSTR expression levels. Unexpectedly, six novel genes were found to be upregulated by octreotide: annexin A1 (ANXA1), rho GTPase-activating protein 18 (ARHGAP18), epithelial membrane protein 1 (EMP1), growth/differentiation factor 15 (GDF15), TGF-beta type II receptor (TGFBR2) and tumour necrosis factor (ligand) superfamily member 15 (TNFSF15). Furthermore, these novel genes were expressed in tumour tissues at transcript and protein levels. We suggest that octreotide may use a potential novel framework to exert its beneficial effect as a drug and to convey its action on neuroendocrine cells. Thus, six novel genes may regulate cell growth and differentiation in normal and tumour neuroendocrine cells and have a role in a novel octreotide mechanism system.

Muscarinic acetylcholine receptor M3 in proliferation and perineural invasion of cholangiocarcinoma cells

BACKGROUND

Cholangiocarcinoma, a type of malignant tumor, originates from epithelial cells of the bile duct. Perineural invasion is common path for cholangiocarcinoma metastasis, and it is highly correlated with postoperative recurrence and poor prognosis. It has been reported that muscarinic acetylcholine receptor M3 (mAChR M3) is widely expressed in digestive tract cancer, and may play an important role in the proliferation, differentiation, transformation and carcinogenesis of tumors. This study was to explore the effect of mAChR M3 on the growth of cholangiocarcinoma cells in vitro and provide a new approach to the pathogenesis and treatment of cholangiocarcinoma.

METHODS

Streptavidin-biotin complex immunohistochemistry was carried out to assess the expression of mAChR M3 in surgical specimens of cholangiocarcinomas (40 cases) and normal bile duct tissues (9), as well as to investigate nerve infiltration. The cholangiocarcinoma cells were treated with different concentrations of selective M-receptor agonist pilocarpine and M-receptor blocker atropine sulfate to induce changes in cell proliferation. The experimental data were analyzed by the Chi-square test.

RESULTS

The strongly-positive expression rate of mAChR M3 was much higher in poorly-differentiated (69%, 9/13) than in well- and moderately-differentiated cholangiocarcinomas (30%, 8/27) (X2=5.631, P<0.05). The strongly-positive mAChR M3 expression rate in hilar cholangiocarcinoma (50%, 14/28) was higher than that in cholangiocarcinomas from the middle and lower common bile duct (25%, 3/12) (X2=2.148, P<0.05). Cholangiocarcinomas with distant metastasis had a strongly-positive expression rate (75%, 9/12), which was much higher than those without distant metastasis (29%, 8/28) (X2=7.410, P<0.01). The absorbance value in the pilocarpine+atropine group was significantly higher than the corresponding value in the pilocarpine group.

CONCLUSIONS

The expression of mAChR M3 is influenced by the extent of differentiation, distant metastasis and the site of cholangiocarcinoma. It also plays a key role in the proliferation and metastasis of cholangiocarcinoma.

The new truncated somatostatin receptor variant sst5TMD4 is associated to poor prognosis in breast cancer and increases malignancy in MCF-7 cells

Somatostatin receptors (sst1-5) are present in different types of tumors, where they inhibit key cellular processes such as proliferation and invasion. Although ssts are densely expressed in breast cancer, especially sst2, their role and therapeutic potential remain uncertain. Recently, we identified a new truncated sst5 variant, sst5TMD4, which is related to the abnormal response of certain pituitary tumors to treatment with somatostatin analogs. Here, we investigated the possible role of sst5TMD4 in breast cancer. This study revealed that sst5TMD4 is absent in normal mammary gland, but is abundant in a subset of poorly differentiated human breast tumors, where its expression correlated to that of sst2. Moreover, in the MCF-7 breast cancer model cell, sst5TMD4 expression increased malignancy features such as invasion and proliferation abilities (both in cell cultures and nude mice). This was likely mediated by sst5TMD4-induced increase in phosphorylated extracellular signal-regulated kinases 1 and 2 and p-Akt levels, and cyclin D3 and Arp2/3 complex expression, which also led to mesenchymal-like phenotype. Interestingly, sst5TMD4 interacts physically with sst2 and thereby alters its signaling, enabling disruption of sst2 inhibitory feedback and providing a plausible basis for our findings. These results suggest that sst5TMD4 could be involved in the pathophysiology of certain types of breast tumors.

The biological hallmarks of ileal carcinoids

Endocrine tumours derived from the small intestine, ileal carcinoids, produce and secrete the hormones tachykinins and serotonin, which induces the specific symptoms related to the tumour. Because of their low proliferation rate, they are often discovered at late stages when metastases have occurred. The biology that characterizes these tumours differs in many ways from what is generally recognized for other malignancies. In this overview, the current knowledge on the development and progression of ileal carcinoids is described.

Oncolytic adenovirus modified with somatostatin motifs for selective infection of neuroendocrine tumor cells

We have previously described the oncolytic adenovirus, Ad(CgA-E1A-miR122), herein denoted Ad5(CgA-E1A-miR122) that selectively replicates in and kills neuroendocrine cells, including freshly isolated midgut carcinoid cells from liver metastases. Ad5(CgA-E1A-miR122) is based on human adenovirus serotype 5 (Ad5) and infects target cells by binding to the coxsackie-adenovirus receptor (CAR) and integrins on the cell surface. Some neuroendocrine tumor (NET) and neuroblastoma cells express low levels of CAR and are therefore poorly transduced by Ad5. However, they often express high levels of somatostatin receptors (SSTRs). Therefore, we introduced cyclic peptides, which contain four amino acids (FWKT) and mimic the binding site for SSTRs in the virus fiber knob. We show that FWKT-modified Ad5 binds to SSTR₂ on NET cells and transduces midgut carcinoid cells from liver metastases about 3-4 times better than non-modified Ad5. Moreover, FWKT-modified Ad5 overcomes neutralization in an ex vivo human blood loop model to greater extent than Ad5, indicating that fiber knob modification may prolong the systemic circulation time. We conclude that modification of adenovirus with the FWKT motif may be beneficial for NET therapy.

GPCR somatostatin receptor extracellular loop 2 is a key ectodomain for making subtype-selective antibodies with agonist-like activities in the pancreatic neuroendocrine tumor BON cell line

OBJECTIVES

The extracellular loop 2 (ECL2) ectodomain of the G protein-coupled receptor class A is thought to function like an inactivation "lid." We created polyclonal somatostatin receptor ECL2 (anti-SSTR ECL2) antibodies to target this lid and to examine if these antibodies can selectively activate the SSTR.

METHODS

Western blots and live-cell immunofluorescence microscopy determined anti-SSTR ECL2 antibody receptor binding selectivity. 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay (MTS assay) and cell cycle assay (fluorescence-activated cell sorting) checked for antibody effect on antiproliferation. Nexin assay examined the antibody's ability to induce apoptosis. LANCE cAMP kit (Perkin Elmer) detected antibody-dependent cAMP decrease. Enzyme-linked immunosorbent assay measured antibody effect on suppressing serotonin secretion. Ligand-receptor binding interference assay with the fluorescent somatostatin (FAM-SST) was used to examine antibody interference to SST-SSTR binding.

RESULTS

Anti-SSTR ECL2 antibodies are SSTR subtype selective and agonist-like, and they suppress cell proliferation via cell cycle arrest and apoptosis. In addition, these antibodies decrease cAMP production and inhibit serotonin secretion. Interestingly, these antibodies do not interfere with SST-SSTR binding.

CONCLUSIONS

The ECL2 is an important ectodomain for G protein-coupled receptor activation and required for ligand binding selectivity. The anti-SSTR2, anti-SSTR3, and anti-SSTR5 ECL2 antibodies independently inhibited BON proliferation and decreased hormone secretion. Unlike octreotide, our antibodies do not interfere with SST-SSTR binding.

Potential applications for cell regulatory factors in liver progenitor cell therapy

Orthotopic liver transplant represent the state of the art treatment for terminal liver pathologies such as cirrhosis in adults and hemochromatosis in neonates. A limited supply of transplantable organs in relationship to the demand means that many patients will succumb to disease before an organ becomes available. One promising alternative to liver transplant is therapy based on the transplant of liver progenitor cells. These cells may be derived from the patient, expanded in vitro, and transplanted back to the diseased liver. Inborn metabolic disorders represent the most attractive target for liver progenitor cell therapy, as many of these disorders may be corrected by repopulation of only a portion of the liver by healthy cells. Another potential application for liver progenitor cell therapy is the seeding of bio-artificial liver matrix. These ex vivo bioreactors may someday be used to bridge critically ill patients to other treatments. Conferring a selective growth advantage to the progenitor cell population remains an obstacle to therapy development. Understanding the molecular signaling mechanisms and micro-environmental cues that govern liver progenitor cell phenotype may someday lead to strategies for providing this selective growth advantage. The discovery of a population of cells within the bone marrow possessing the ability to differentiate into hepatocytes may provide an easily accessible source of cells for liver therapies.

The expression of E-cadherin in somatotroph pituitary adenomas is related to tumor size, invasiveness, and somatostatin analog response

CONTEXT

Appropriate cell-to-cell adhesion is fundamental for the epithelial phenotype of pituitary cells. Loss of the adhesion protein E-cadherin has been associated with invasiveness, metastasis, and poor prognosis in cancers of epithelial origin. In somatotroph adenomas, a variable and reduced expression of E-cadherin has been demonstrated. In addition, nuclear translocation of E-cadherin was found to correlate with pituitary tumor invasion.

OBJECTIVE

The objective was to examine the protein expression of E-cadherin in somatotroph pituitary adenomas in relation to adenoma size, invasiveness, and somatostatin analog (SMS) efficacy.

PATIENTS AND METHODS

Eighty-three patients were included, and 29 were treated preoperatively with SMS. Adenoma E-cadherin protein expression was analyzed by Western blot (61 patients) and immunohistochemistry (IHC) (80 patients) with antibodies directed against both extracellular and intracellular domains (IHC). The acute (direct surgery group) and long-term (preoperatively treated group) SMS responses were evaluated. Baseline tumor volume and invasiveness were measured on magnetic resonance imaging scans.

RESULTS

Membranous E-cadherin was lost in several adenomas. Nine of these were nuclear E-cadherin positive. The E-cadherin protein expression correlated negatively to tumor size and positively to acute SMS response. Low E-cadherin levels (preoperatively treated group only) and loss of membranous E-cadherin correlated to tumor invasiveness. The E-cadherin level correlated positively to tumor reduction after SMS treatment, and adenomas with nuclear E-cadherin staining had lower IGF-I reduction and tumor shrinkage. Preoperatively treated adenomas had reduced E-cadherin protein levels, but the IHC expression was unaltered.

CONCLUSION

Reduced E-cadherin expression may correlate to a dedifferentiated phenotype in the somatotroph pituitary adenomas.