Exposure to nonanoic acid alters small intestinal neuroendocrine tumor phenotype.

BACKGROUND: Small intestinal neuroendocrine tumors (SI-NET) are highly differentiated and genetically stable malignant tumors, yet they often present with advanced metastatic spread at the time of diagnosis. In contrast to many other types of malignant tumors, primary SI-NET are often asymptomatic and typically smaller in size compared to adjacent lymph node metastases. This study explores the hypothesis that stimulating the chemosensing olfactory receptor 51E1 (OR51E1) decreases SI-NET proliferation suggesting a mechanism that explains a difference in proliferative rate based on tumor location. METHODS: Clinical data was used to address difference in tumor size depending on location. A SI-NET tissue microarray was used to evaluate expression of OR51E1 and olfactory marker protein (OMP). Primary cultured tumor cells from 5 patients were utilized to determine the effect of OR51E1 agonist nonanoic acid on metabolic activity. The SI-NET cell line GOT1 was used to determine effects of nonanoic acid on the transcriptome as well as long-term effects of nonanoic acid exposure with regards to cell proliferation, serotonin secretion, alterations of the cell-cycle and morphology. RESULTS: Tumor size differed significantly based on location. OR51E1 and OMP were generally expressed in SI-NET. Primary SI-NET cells responded to nonanoic acid with a dose dependent altered metabolic activity and this was replicated in the GOT1 cell line but not in the MCF10A control cell line. Nonanoic acid treatment in GOT1 cells upregulated transcripts related to neuroendocrine differentiation and hormone secretion. Long-term nonanoic acid treatment of GOT1 cells decreased proliferation, induced senescence, and altered cell morphology. CONCLUSION: Our results raise the possibility that exposure of intraluminal metabolites could represent a mechanism determining aspects of the SI-NET tumor phenotype. However, we could not causally link the observed effects of nonanoic acid exposure to the OR51E1 receptor.

SARS-CoV-2 replicates and displays oncolytic properties in clear cell and papillary renal cell carcinoma.

The SARS-CoV-2 virus is currently causing a global pandemic. Infection may result in a systemic disease called COVID-19, affecting primarily the respiratory tract. Often the gastrointestinal tract and kidneys also become involved. Angiotensin converting enzyme 2 (ACE2) serves as the receptor for SARS-CoV-2. The membrane proteins, Transmembrane serine protease 2 (TMPRSS2) and Neuropilin 1 (NRP1) are accessory proteins facilitating the virus entry. In this study we show that the human proximal kidney tubules, express these factors. We hypothesized that cancers derived from proximal tubules as clear cell (CCRCC) and papillary renal cell carcinoma (PRCC), retain the expression of the SARS-CoV-2 entry factors making these cancers susceptible to SARS-CoV-2 infection. We used bioinformatics, western blotting, and assessment of tissue micro arrays (TMA) including 263 cases of CCRCC, 139 cases of PRCC and 18 cases of chromophobe RCC to demonstrate that the majority of CCRCC and PRCC cases retained the RNA and protein expression of the entry factors for SARS-CoV-2. We furthermore show that SARS-CoV-2 virus propagated robustly in primary cultures of CCRCC and PRCC cells with a visible virus cytopathogenic effect correlating with viral RNA expression levels. We also noted that the delta-variant of SARS-CoV-2 causes cancer cells to form syncytia in-vitro. This phenomenon was also identified histologically in CCRCC tissue from a patient that had been hospitalized for COVID-19, twelve months prior to nephrectomy. Our data provide insights into SARS-CoV-2 infectivity in renal cell carcinoma and that the virus causes a distinct cytopathogenic effect.

Independent somatic evolution underlies clustered neuroendocrine tumors in the human small intestine.

Small intestine neuroendocrine tumor (SI-NET), the most common cancer of the small bowel, often displays a curious multifocal phenotype with several tumors clustered together in a limited intestinal segment. SI-NET also shows an unusual absence of driver mutations explaining tumor initiation and metastatic spread. The evolutionary trajectories that underlie multifocal SI-NET lesions could provide insight into the underlying tumor biology, but this question remains unresolved. Here, we determine the complete genome sequences of 61 tumors and metastases from 11 patients with multifocal SI-NET, allowing for elucidation of phylogenetic relationships between tumors within single patients. Intra-individual comparisons revealed a lack of shared somatic single-nucleotide variants among the sampled intestinal lesions, supporting an independent clonal origin. Furthermore, in three of the patients, two independent tumors had metastasized. We conclude that primary multifocal SI-NETs generally arise from clonally independent cells, suggesting a contribution from a cancer-priming local factor.

SMAD4 haploinsufficiency in small intestinal neuroendocrine tumors.

BACKGROUND: Patients with small intestinal neuroendocrine tumors (SINETs) frequently present with lymph node and liver metastases at the time of diagnosis, but the molecular changes that lead to the progression of these tumors are largely unknown. Sequencing studies have only identified recurrent point mutations at low frequencies with CDKN1B being the most common harboring heterozygous mutations in less than 10% of all tumors. Although SINETs are genetically stable tumors with a low frequency of point mutations and indels, they often harbor recurrent hemizygous copy number alterations (CNAs) yet the functional implications of these CNA are unclear. METHODS: Utilizing comparative genomic hybridization (CGH) arrays we analyzed the CNA profile of 131 SINETs from 117 patients. Two tumor suppressor genes and corresponding proteins i.e. SMAD4, and CDKN1B, were further characterized using a tissue microarray (TMA) with 846 SINETs. Immunohistochemistry (IHC) was used to quantify protein expression in TMA samples and this was correlated with chromosome number evaluated with fluorescent in-situ hybridization (FISH). Intestinal tissue from a Smad4+/- mouse model was used to detect entero-endocrine cell hyperplasia with IHC. RESULTS: Analyzing the CGH arrays we found loss of chromosome 18q and SMAD4 in 71% of SINETs and that focal loss of chromosome 12 affecting the CDKN1B was present in 9.4% of SINETs. No homozygous loss of chromosome 18 was detected. Hemizygous loss of SMAD4, but not CDKN1B, significantly correlated with reduced protein levels but hemizygous loss of SMAD4 did not induce entero-endocrine cell hyperplasia in the Smad4+/- mouse model. In addition, patients with low SMAD4 protein expression in primary tumors more often presented with metastatic disease. CONCLUSIONS: Hemizygous loss of chromosome 18q and the SMAD4 gene is the most common genetic event in SINETs and our results suggests that this could influence SMAD4 protein expression and spread of metastases. Although SMAD4 haploinsufficiency alone did not induce tumor initiation, loss of chromosome 18 could represent an evolutionary advantage in SINETs explaining the high prevalence of this aberration. Functional consequences of reduced SMAD4 protein levels could hypothetically be a potential mechanism as to why loss of chromosome 18 appears to be clonally selected in SINETs.

177Lu-octreotate therapy for neuroendocrine tumours is enhanced by Hsp90 inhibition.

177Lu-octreotate is an FDA-approved radionuclide therapy for patients with gastroenteropancreatic neuroendocrine tumours (NETs) expressing somatostatin receptors. The 177Lu-octreotate therapy has shown promising results in clinical trials by prolonging progression-free survival, but complete responses are still uncommon. The aim of this study was to improve the 177Lu-octreotate therapy by means of combination therapy. To identify radiosensitising inhibitors, two cell lines, GOT1 and P-STS, derived from small intestinal neuroendocrine tumours (SINETs), were screened with 1,224 inhibitors alone or in combination with external radiation. The screening revealed that inhibitors of Hsp90 can potentiate the tumour cell-killing effect of radiation in a synergistic fashion (GOT1; false discovery rate <3.2×10-11). The potential for Hsp90 inhibitor ganetespib to enhance the anti-tumour effect of 177Lu-octreotate in an in vivo setting was studied in the somatostatin receptor-expressing GOT1 xenograft model. The combination led to a larger decrease in tumour volume relative to monotherapies and the tumour-reducing effect was shown to be synergistic. Using patient-derived tumour cells from eight metastatic SINETs, we could show that ganetespib enhanced the effect of 177Lu-octreotate therapy for all investigated patient tumours. Levels of Hsp90 protein expression were evaluated in 767 SINETs from 379 patients. We found that Hsp90 expression was upregulated in tumour cells relative to tumour stroma in the vast majority of SINETs. We conclude that Hsp90 inhibitors enhance the tumour-killing effect of 177Lu-octreotate therapy synergistically in SINET tumour models and suggest that this potentially promising combination should be further evaluated.

miRNA profiling of small intestinal neuroendocrine tumors defines novel molecular subtypes and identifies miR-375 as a biomarker of patient survival.

The aim of this study was to define the miRNA profile of small intestinal neuroendocrine tumors and to search for novel molecular subgroups and prognostic biomarkers. miRNA profiling was conducted on 42 tumors from 37 patients who underwent surgery for small intestinal neuroendocrine tumors. Unsupervised hierarchical clustering analysis of miRNA profiles identified two groups of tumor metastases, denoted cluster M1 and M2. The smaller cluster M1 was associated with shorter overall survival and contained tumors with higher grade (WHO grade G2/3) and multiple chromosomal gains including gain of chromosome 14. Tumors of cluster M1 had elevated expression of miR-1246 and miR-663a, and reduced levels of miR-488-3p. Pathway analysis predicted Wnt signaling to be the most significantly altered signaling pathway between clusters M1 and M2. Analysis of miRNA expression in relation to tumor proliferation rate showed significant alterations including downregulation of miR-137 and miR-204-5p in tumors with Ki67 index above 3%. Similarly, tumor progression was associated with significant alterations in miRNA expression, e.g. higher expression of miR-95 and miR-210, and lower expression of miR-378a-3p in metastases. Pathway analysis predicted Wnt signaling to be altered during tumor progression, which was supported by decreased nuclear translocation of ß-catenin in metastases. Survival analysis revealed that downregulation of miR-375 was associated with shorter overall survival. We performed in situ hybridization on biopsies from an independent cohort of small intestinal neuroendocrine tumors using tissue microarrays. Expression of miR-375 was found in 578/635 (91%) biopsies and survival analysis confirmed that there was a correlation between downregulation of miR-375 in tumor metastases and shorter patient survival. We conclude that miRNA profiling defines novel molecular subgroups of metastatic small intestinal neuroendocrine tumors and identifies miRNAs associated with tumor proliferation rate and progression. miR-375 is highly expressed in small intestinal neuroendocrine tumors and may be used as a prognostic biomarker.

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.

Priming increases the anti-tumor effect and therapeutic window of 177Lu-octreotate in nude mice bearing human small intestine neuroendocrine tumor GOT1.

BACKGROUND: 177Lu-[DOTA0, Tyr3]-octreotate (177Lu-octreotate) is used for treatment of patients with somatostatin receptor (SSTR) expressing neuroendocrine tumors. However, complete tumor remission is rarely seen, and optimization of treatment protocols is needed. In vitro studies have shown that irradiation can up-regulate the expression of SSTR1, 2 and 5, and increase 177Lu-octreotate uptake. The aim of the present study was to examine the anti-tumor effect of a 177Lu-octreotate priming dose followed 24 h later by a second injection of 177Lu-octreotate compared to a single administration of 177Lu-octreotate, performed on the human small intestine neuroendocrine tumor cell line, GOT1, transplanted to nude mice. RESULTS: Priming resulted in a 1.9 times higher mean absorbed dose to the tumor tissue per administered activity, together with a reduced mean absorbed dose for kidneys. Priming gave the best overall anti-tumor effects. Magnetic resonance imaging showed no statistically significant difference in tumor response between treatment with and without priming. Gene expression analysis demonstrated effects on cell cycle regulation. Biological processes associated with apoptotic cell death were highly affected in the biodistribution and dosimetry study, via differential regulation of, e.g., APOE, BAX, CDKN1A, and GADD45A. CONCLUSIONS: Priming had the best overall anti-tumor effects and also resulted in an increased therapeutic window. Results indicate that potential biomarkers for tumor regrowth may be found in the p53 or JNK signaling pathways. Priming administration is an interesting optimization strategy for 177Lu-octreotate therapy of neuroendocrine tumors, and further studies should be performed to determine the mechanisms responsible for the reported effects.

NAMPT Inhibitor GMX1778 Enhances the Efficacy of 177Lu-DOTATATE Treatment of Neuroendocrine Tumors.

Neuroendocrine tumors (NETs) can be treated by peptide receptor radionuclide therapy using radiolabeled somatostatin analogs. However, the efficacy of such treatment is low and needs to be optimized. Our study evaluated the potential radiosensitizing effects of inhibition of nicotineamide phosphoribosyltransferase on 177Lu-DOTATATE treatment in a NET model. METHODS: Nude mice xenografted with the human NET cell line GOT1 were treated with semiefficient doses of 177Lu-DOTATATE (7.5 MBq, intravenously) or the nicotineamide phosphoribosyltransferase inhibitor GMX1778 (100 mg/kg/wk, orally). RESULTS: Median time to tumor progression (tumor volume larger than at day 0) was 3 d for controls, 7 d for single-dose GMX1778, 28 d for single-dose 177Lu-DOTATATE, 35 d for 3 weekly doses of GMX1778, and 98 d for combined treatment with 177Lu-DOTATATE and GMX1778 × 1. After 177Lu-DOTATATE and 3 weekly doses of GMX1778, none of the tumors progressed within 120 d. CONCLUSION: GMX1778 enhances the efficacy of 177Lu-DOTATATE treatment and induces a prolonged antitumor response.

Expression profiling of small intestinal neuroendocrine tumors identifies subgroups with clinical relevance, prognostic markers and therapeutic targets.

We wanted to define the transcriptome of small intestinal neuroendocrine tumors in order to identify clinically relevant subgroups of tumors, prognostic markers and novel targets for treatment. Genome-wide expression profiling was conducted on tumor biopsies from 33 patients with well-differentiated neuroendocrine tumors of the distal ileum and metastatic disease at the time of diagnosis. Unsupervised hierarchical clustering analysis identified three groups of tumors. The largest group, comprising half of the tumors, was characterized by longer patient survival and higher expression of neuroendocrine markers, including SSTR2. Tumors with higher grade (G2/3) or gain of chromosome 14 were associated with shorter patient survival and increased expression of cell cycle-promoting genes. Pathway analysis predicted the prostaglandin E receptor 2 (PTGER2) as the most significantly activated regulator in tumors of higher grade, whereas Forkhead box M1 (FOXM1) was the most significantly activated regulator in tumors with gain of chromosome 14. Druggable genes identified from expression profiles included clinically proven SSTR2 and also novel targets, for example, receptor tyrosine kinases (RET, FGFR1/3, PDGFRB and FLT1), epigenetic regulators, molecular chaperones and signal transduction molecules. Evaluation of candidate drug targets on neuroendocrine tumors cells (GOT1) showed significant inhibition of tumor cell growth after treatment with tyrosine kinase inhibitors or inhibitors of HDAC, HSP90 and AKT. In conclusion, we have defined the transcriptome of small intestinal neuroendocrine tumors and identified novel subgroups with clinical relevance. We found specific gene expression patterns associated with tumor grade and chromosomal alterations. Our data also suggest novel prognostic biomarkers and therapies for these patients.

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-ß1, 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.

Gastrointestinal stromal tumors (GISTs) express somatostatin receptors and bind radiolabeled somatostatin analogs.

BACKGROUND: Gastrointestinal stromal tumors (GISTs) can be effectively treated with tyrosine kinase inhibitors (TKIs). However, some patients with GIST develop drug resistance, and alternative treatment strategies are therefore needed. The aim of this study was to analyze the expression of somatostatin receptors (SSTR) in GIST as a target for peptide receptor-mediated radiotherapy (PRRT). MATERIAL AND METHODS: Expression profiling of SSTR1-5 was performed on biopsies from 34 GISTs (16 gastric tumors, 15 small intestinal tumors, and three rectal tumors). SSTR scintigraphy ((111)In-octreotide) and measurement of (111)In activity in tumor specimens was performed in seven patients. Uptake and internalization of (177)Lu- octreotate was studied in primary cell cultures from two patients. RESULTS: Quantitative PCR analysis showed expression of SSTR1 and SSTR2 in the majority of tumors, while SSTR3-5 were expressed at low levels. Immunohistochemical analysis confirmed the presence of SSTR1 and SSTR2 proteins in all GISTs, and SSTR3-5 in a subset of tumors. Diagnostic imaging by SSTR scintigraphy, using (111)In-octreotide, demonstrated tumor uptake of (111)In in three of six GIST patients. Measurement of (111)In activity in excised tumor specimens from five patients gave tumor-to-blood (T/B) activity ratios of between eight and 96. Tumor cells in primary culture (gastric and small intestinal GIST) specifically bound and internalized (177)Lu when incubated with the therapeutic compound (177)Lu-octreotate for 4-48 hours (p < 0.05). CONCLUSION: Peptide receptor-mediated radiotherapy via SSTR may provide a novel treatment strategy in carefully selected GIST patients with TKI-resistant tumors.

New medical strategies for midgut carcinoids.

Patients with well-differentiated neuroendocrine tumours of the gastrointestinal tract often present with metastases and hormonal symptoms. These patients can be palliated by interventional tumour reduction and medical treatment with somatostatin analogues; no effective chemotherapy is available. Radionuclide therapy via somatostatin receptors is one new therapeutic alternative. The recognition that neuroendocrine tumours express specific receptors for growth factors and chemokines, which are of importance for tumour growth, vascularization, and spread, may open the way for new therapeutic approaches. The signalling pathways in carcinoid tumours are incompletely explored. This review summarizes potential new treatment strategies from clinical and experimental studies, e.g. inhibition of angiogenesis, targeting of growth factors or their receptors by tyrosine kinase inhibitors, interference with specific cellular pathways (mTOR, PI3K, RAS/RAF, Notch), and also inhibition of the proteasome and histone deacetylation. Combining targeted therapy with chemotherapy, or using drugs to sensitize for radionuclide therapy, may enhance the treatment outcome.

Hypoxia stimulates CXCR4 signalling in ileal carcinoids.

Tumour hypoxia is associated with increased metastatic potential and resistance to radiotherapy and chemotherapy. Ileal carcinoids are usually metastatic at the time of diagnosis and respond poorly to chemotherapy. The aim of this study was to investigate the extent of hypoxia in ileal carcinoids and the response of tumour cells to induced hypoxia. Vascular endothelial growth factor (VEGF), carbonic anhydrase (CA-IX), hypoxia-inducible factor (HIF)-1alpha and HIF-2alpha were studied by immunohistochemistry in biopsies from 24 patients with ileal carcinoids. All hypoxic markers were shown to be highly expressed in localized areas of the tumours irrespective of tumour location or stage. However, HIF-2alpha expression was significantly higher in distant metastases compared to primary tumours in the same patient. Global gene expression profiling of GOT1 carcinoid cells revealed a marked response to hypoxia. Expression of genes related to epithelial-to-mesenchymal transition and development was altered including increased expression of the C-X-C chemokine receptor type 4 (CXCR4), an important regulator of invasive growth and metastasis formation. High expression of CXCR4 was confirmed by immunohistochemistry in tumour biopsies. Stimulation of GOT1 cells by the CXCR4 ligand, CXCL12 (stromal cell-derived factor 1 (SDF-1)), activated the mitogen-activated protein kinase (MAPK) p42/44 signalling pathway and increased tumour cell migration. We conclude that ileal carcinoids contain hypoxic areas expressing HIF-1alpha, HIF-2alpha and CXCR4. Signalling through the CXCL12-CXCR4 axis may contribute to the metastatic potential of ileal carcinoids. Targeting of HIFs and/or the CXCR4 signalling pathway may offer new therapeutic strategies for carcinoid tumour disease.

The multifunctional FUS, EWS and TAF15 proto-oncoproteins show cell type-specific expression patterns and involvement in cell spreading and stress response.

BACKGROUND: FUS, EWS and TAF15 are structurally similar multifunctional proteins that were first discovered upon characterization of fusion oncogenes in human sarcomas and leukemias. The proteins belong to the FET (previously TET) family of RNA-binding proteins and are implicated in central cellular processes such as regulation of gene expression, maintenance of genomic integrity and mRNA/microRNA processing. In the present study, we investigated the expression and cellular localization of FET proteins in multiple human tissues and cell types. RESULTS: FUS, EWS and TAF15 were expressed in both distinct and overlapping patterns in human tissues. The three proteins showed almost ubiquitous nuclear expression and FUS and TAF15 were in addition present in the cytoplasm of most cell types. Cytoplasmic EWS was more rarely detected and seen mainly in secretory cell types. Furthermore, FET expression was downregulated in differentiating human embryonic stem cells, during induced differentiation of neuroblastoma cells and absent in terminally differentiated melanocytes and cardiac muscle cells. The FET proteins were targeted to stress granules induced by heat shock and oxidative stress and FUS required its RNA-binding domain for this translocation. Furthermore, FUS and TAF15 were detected in spreading initiation centers of adhering cells. CONCLUSION: Our results point to cell-specific expression patterns and functions of the FET proteins rather than the housekeeping roles inferred from earlier studies. The localization of FET proteins to stress granules suggests activities in translational regulation during stress conditions. Roles in central processes such as stress response, translational control and adhesion may explain the FET proteins frequent involvement in human cancer.

Amyloid precursor-like protein 1 is differentially upregulated in neuroendocrine tumours of the gastrointestinal tract.

We have examined the global gene expression profile of small intestinal carcinoids by microarray analysis. High expression of a number of genes was found including amyloid precursor-like protein 1 (APLP1). Quantitative real-time PCR and western blot analysis demonstrated higher expression of APLP1 in carcinoid metastases relative to primary tumours indicating a role of APLP1 in tumour dissemination. Tissue microarray analysis of gastroentero-pancreatic tumours demonstrated a high frequency of APLP1 expression and a low frequency of APLP2 expression in neuroendocrine (NE) tumours when compared with non-NE tumours at the same sites. Meta-analysis of gene expression data from a large number of tumours outside the gastrointestinal tract confirmed a correlation between APLP1 expression and NE phenotype where high expression of APLP1 was accompanied by downregulation of APLP2 in NE tumours. Cellular localization of APLP1, APLP2 and amyloid precursor protein (APP) in carcinoid cells (GOT1) by confocal microscopy demonstrated partial co-localization with synaptophysin. This suggests that the APP family of proteins is transported to the cell membrane by synaptic microvesicles and that they may influence tumour cell adhesion and invasiveness. We conclude that APLP1 is differentially upregulated in gastrointestinal NE tumours and that APLP1 may be important for the dissemination of small intestinal carcinoids. Identification of APLP1 in NE tumours offers a novel target for treatment and may also serve as a tumour-specific marker.

Neuroblastoma-specific cytotoxicity mediated by the Mash1-promoter and E. coli purine nucleoside phosphorylase.

BACKGROUND: Neuroblastoma is derived from cells of neural crest origin and often expresses the transcription factor human achaete-scute homolog 1 (HASH1). The aim of this study was to selectively kill neuroblastoma cells by expressing the suicide gene E. coli purine nucleoside phosphorylase (PNP) under the control of the Mash1 promoter, the murine homolog of HASH1. PROCEDURE: The E. coli PNP gene regulated by the Mash1 promoter was cloned into an expression vector and transfected into neuroblastoma and non-neuroblastoma cell lines. After addition of the prodrug M2-fluoroadenine 9-beta-D-arabinofuranoside (F-araA) the cell-specific toxicity was examined. To optimize the cell specific activity, different sizes of the Mash1 promoter were analyzed in neuroblastoma cell lines and compared with the activity in non-neuroblastoma cells. RESULTS: Estimated as the percentages of CMV enhancer-promoter, the activity was significantly higher in the neuroblastoma cells, ranging from 17 to 58% when the shortest and the most active promoter was measured. The non-neuroblastoma cells yielded only 1-6% of the CMV promoter activity. When the shortest Mash1 promoter was combined with the E. coli PNP gene the cytotoxicity was 65% in the neuroblastoma cells with low cell death in the non-neuroblastoma cell lines, relative to the cytotoxicity where the E.coli PNP gene was regulated by the strong but non-specific CMV enhancer-promoter. CONCLUSIONS: We show here that the Mash1 promoter regulating the PNP gene confers a cell-type selective toxicity in neuroblastoma cell lines. These results indicate the feasibility to use the Mash1 promoter for regulating E.coli PNP expression in gene-directed enzyme prodrug therapy (GDEPT) of neuroblastoma.

Antitumoural effects of the pyridyl cyanoguanidine CHS 828 on three different types of neuroendocrine tumours xenografted to nude mice.

CHS 828, a cyanoguanidine with potent experimental antitumoural activity, inhibits activation of nuclear factor-kappaB. In the present study, marked antitumoural activity of peroral CHS 828 was shown against three different human neuroendocrine tumours, midgut carcinoid (GOT1), pancreatic carcinoid (BON), and medullary thyroid carcinoma (GOT2), transplanted in nude mice. Our results indicate that CHS 828 can be a candidate drug for treatment of neuroendocrine tumours.

ASK1 inhibits astroglial development via p38 mitogen-activated protein kinase and promotes neuronal differentiation in adult hippocampus-derived progenitor cells.

The mechanisms controlling differentiation and lineage specification of neural stem cells are still poorly understood, and many of the molecules involved in this process and their specific functions are yet unknown. We investigated the effect of apoptosis signal-regulating kinase 1 (ASK1) on neural stem cells by infecting adult hippocampus-derived rat progenitors with an adenovirus encoding the constitutively active form of ASK1. Following ASK1 overexpression, a significantly larger number of cells differentiated into neurons and a substantial increase in Mash1 transcription was observed. Moreover, a marked depletion of glial cells was observed, persisting even after additional treatment of ASK1-infected cultures with potent glia inducers such as leukemia inhibitory factor and bone morphogenetic protein. Analysis of the promoter for glial fibrillary acidic protein revealed that ASK1 acts as a potent inhibitor of glial-specific gene transcription. However, the signal transducers and activators of transcription 3 (STAT3)-binding site in the promoter was dispensable, while the activation of p38 mitogen-activated protein kinase was crucial for this effect, suggesting the presence of a novel mechanism for the inhibition of glial differentiation.