Neurotensin-mediated activation of MAPK pathways and AP-1 binding in the human pancreatic cancer cell line, MIA PaCa-2

Chelator boosted tumor-retention and pharmacokinetic properties: development of 64Cu labeled radiopharmaceuticals targeting neurotensin receptor

PURPOSE

Accumulating evidence suggests that neurotensin (NTS) and neurotensin receptors (NTSRs) play key roles in lung cancer progression by triggering multiple oncogenic signaling pathways. This study aims to develop Cu-labeled neurotensin receptor 1 (NTSR1)-targeting agents with the potential for both imaging and therapeutic applications.

METHOD

A series of neurotensin receptor antagonists (NRAs) with variable propylamine (PA) linker length and different chelators were synthesized, including [64Cu]Cu-CB-TE2A-iPA-NRA ([64Cu]Cu-4a-c, i = 1, 2, 3), [64Cu]Cu-NOTA-2PA-NRA ([64Cu]Cu-4d), [64Cu]Cu-DOTA-2PA-NRA ([64Cu]Cu-4e, also known as [64Cu]Cu-3BP-227), and [64Cu]Cu-DOTA-VS-2PA-NRA ([64Cu]Cu-4f). The series of small animal PET/CT were conducted in H1299 lung cancer model. The expression profile of NTSR1 was also confirmed by IHC using patient tissue samples.

RESULTS

For most of the compounds studied, PET/CT showed prominent tumor uptake and high tumor-to-background contrast, but the tumor retention was strongly influenced by the chelators used. For previously reported 4e, [64Cu]Cu-labeled derivative showed initial high tumor uptake accompanied by rapid tumor washout at 24 h. The newly developed [64Cu]Cu-4d and [64Cu]Cu-4f demonstrated good tumor uptake and tumor-to-background contrast at early time points, but were less promising in tumor retention. In contrast, our lead compound [64Cu]Cu-4b demonstrated 9.57 ± 1.35, 9.44 ± 2.38 and 9.72 ± 4.89%ID/g tumor uptake at 4, 24, and 48 h p.i., respectively. Moderate liver uptake (11.97 ± 3.85, 9.80 ± 3.63, and 7.72 ± 4.68%ID/g at 4, 24, and 48 h p.i.) was observed with low uptake in most other organs. The PA linker was found to have a significant effect on drug distribution. Compared to [64Cu]Cu-4b, [64Cu]Cu-4a had a lower background, including a greatly reduced liver uptake, while the tumor uptake was only moderately reduced. Meanwhile, [64Cu]Cu-4c showed increased uptake in both the tumor and the liver. The clinical relevance of NTSR1 was also demonstrated by the elevated tumor expression in patient tissue samples.

CONCLUSIONS

Through the side-by-side comparison, [64Cu]Cu-4b was identified as the lead agent for further evaluation based on its high and sustained tumor uptake and moderate liver uptake. It can not only be used to efficiently detect NTSR1 expression in lung cancer (for diagnosis, patient screening, and treatment monitoring), but also has the great potential to treat NTSR-positive lesions once chelating to the beta emitter 67Cu.

Neurotensin induces sustainable activation of the ErbB-ERK1/2 pathway, which is required for developmental competence of oocytes in mice

Purpose

LH induces the expression of EGF-like factors and their shedding enzyme (ADAM17) in granulosa cells (GCs), which is essential for ovulation via activation of the ErbB-ERK1/2 pathway in cumulus cells (CCs). Neurotensin (NTS) is reported as a novel regulator of ovulation, whereas the NTS-induced maturation mechanism in oocytes remains unclear. In this study, we focused on the role of NTS in the expression of EGF-like factors and ErbBs, and ADAM17 activity, during oocyte maturation and ovulation in mice.

Methods

The expression and localization in GC and CC were examined. Next, hCG and NTS receptor 1 antagonist (SR) were injected into eCG-primed mice, and the effects of SR on ERK1/2 phosphorylation were investigated. Finally, we explored the effects of SR on the expression of EGF-like factors and ErbBs, and ADAM17 activity in GC and CC.

Results

NTS was significantly upregulated in GC and CC following hCG injection. SR injection suppressed oocyte maturation and ERK1/2 phosphorylation. SR also downregulated part of the expression of EGF-like factors and their receptors, and ADAM17 activity.

Conclusions

NTS induces oocyte maturation through the sustainable activation of the ERK1/2 signaling pathway by upregulating part of the EGF-like factor-induced pathway during oocyte maturation in mice.

Adding of neurotensin to non-small cell lung cancer cells increases tyrosine phosphorylation of HER3

Neurotensin (NTS) receptor 1 regulates the growth non-small cell lung cancer (NSCLC) cells. NTS binds with high affinity to NTSR1, leading to increased tyrosine phosphorylation of the EGFR and HER2. Using Calu3, NCI-H358, or NCI-H441 cells, the effects of NTS on HER3 transactivation were investigated. HER3 tyrosine phosphorylation was increased by NTS or neuregulin (NRG1) addition to NSCLC cells. NCI-H358, NCI-H441, and Calu-3 cells have HER3, NTSR1 and neuregulin (NRG)1 protein. NTSR1 regulation of HER3 transactivation was impaired by SR48692 (NTSR1 antagonist) or monoclonal antibody (mAb)3481 (HER3 blocker). Immunoprecipitation experiments indicated that NTS addition to NCI-H441cells resulted in the formation of EGFR/HER3 and HER2/HER3 heterodimers. The ability of NTS to increase HER3 tyrosine phosphorylation was impaired by GM6001 (MMP inhibitor), PP2 (Src inhibitor), Tiron (superoxide scavenger), or N-acetylcysteine (antioxidant). Adding NTS to NSCLC cells increased phosphorylation of ERK, HER3, and AKT. NTS or NRG1 increased colony formation of NSCLC cells which was strongly inhibited by SR48692 and mAb3481. The results indicate that NTSR1 regulates HER3 transactivation in NSCLC cells leading to increased proliferation.

The Neurotensinergic System: A Target for Cancer Treatment

BACKGROUND

The scientific interest regarding the involvement of peptides in cancer has increased in the last years. In tumor cells the overexpression of peptides and their receptors is known and new therapeutic targets for the treatment of cancer have been suggested. The overexpression of the neurotensinergic system has been associated with poor prognosis, tumor size, higher tumor aggressiveness, increased relapse risk and worse sensitivity to chemotherapy agents.

OBJECTIVE

The aim of this review is to update the findings regarding the involvement of the neurotensinergic system in cancer to suggest anticancer therapeutic strategies targeting this system. The neurotensin (NT) precursor, NT and its receptors (NTR) and the involvement of the neurotensinergic system in lung, breast, prostate, gastric, colon, liver and pancreatic cancers, glioblastoma, neuroendocrine tumors and B-cell leukemia will be mentioned and discussed as well as the signaling pathways mediated by NT. Some research lines to be developed in the future will be suggested such as: molecules regulating the expression of the NT precursor, influence of the diet in the development of tumors, molecules and signaling pathways activated by NT and antitumor therapeutic strategies targeting the neurotensinergic system.

CONCLUSION

NT, via the NTR, exerts oncogenic (tumor cell proliferation, invasion, migration, angiogenesis) and antiapoptotic effects, whereas NTR antagonists inhibit these effects. NTR expression can be used as a diagnostic tool/therapeutic target and the administration of NTR antagonists as antitumor drugs could be a therapeutic strategy to treat tumors overexpressing NTR.

Bombesin, endothelin, neurotensin and pituitary adenylate cyclase activating polypeptide cause tyrosine phosphorylation of receptor tyrosine kinases

Numerous peptides including bombesin (BB), endothelin (ET), neurotensin (NTS) and pituitary adenylate cyclase-activating polypeptide (PACAP) are growth factors for lung cancer cells. The peptides bind to G protein-coupled receptors (GPCRs) resulting in elevated cAMP and/or phosphatidylinositol (PI) turnover. In contrast, growth factors such as epidermal growth factor (EGF) or neuregulin (NRG)-1 bind to receptor tyrosine kinases (RTKs) such as the EGFR or HER3, increasing tyrosine kinase activity, resulting in the phosphorylation of protein substrates such as PI3K or phospholipase (PL)C. Peptide GPCRs can transactivate numerous RTKs, especially members of the EGFR/HER family resulting in increased phosphorylation of ERK, leading to cellular proliferation or increased phosphorylation of AKT, leading to cellular survival. GRCR antagonists and tyrosine kinase inhibitors are useful agents to prevent RTK transactivation and inhibit proliferation of cancer cells.

Neurotensin receptor 1 signaling promotes pancreatic cancer progression

Pancreatic cancer is one of the cancers with the poorest prognosis, with a 5-year survival rate of approximately 5-10%. Thus, it is urgent to identify molecular targets for the treatment of pancreatic cancer. Using serial transplantations in a mouse pancreatic orthotopic inoculation model, we previously produced highly malignant pancreatic cancer sublines with increased tumor-forming abilities in vivo. Here, we used these sublines to screen molecular targets for the treatment of pancreatic cancer. Among the genes with increased expression levels in the sublines, we focused on those encoding cell surface receptors that may be involved in the interactions between cancer cells and the tumor microenvironment. Based on our previous RNA-sequence analysis, we found increased expression levels of neurotensin (NTS) receptor 1 (NTSR1) in highly malignant pancreatic cancer sublines. Furthermore, re-analysis of clinical databases revealed that the expression level of NTSR1 was increased in advanced pancreatic cancer and that high NTSR1 levels were correlated with a poor prognosis. Overexpression of NTSR1 in human pancreatic cancer cells Panc-1 and SUIT-2 accelerated their tumorigenic and metastatic abilities in vivo. In addition, RNA-sequence analysis showed that MAPK and NF-κB signaling pathways were activated upon NTS stimulation in highly malignant cancer sublines and also revealed many new target genes for NTS in pancreatic cancer cells. NTS stimulation increased the expression of MMP-9 and other pro-inflammatory cytokines and chemokines in pancreatic cancer cells. Moreover, the treatment with SR48692, a selective NTSR1 antagonist, suppressed the activation of the MAPK and NF-κB signaling pathways and induction of target genes in pancreatic cancer cells in vitro, while the administration of SR48692 attenuated the tumorigenicity of pancreatic cancer cells in vivo. These findings suggest that NTSR1 may be a prognostic marker and a molecular target for pancreatic cancer treatment.

Neurotensin pathway in digestive cancers and clinical applications: an overview

Initially, NEUROTENSIN (NTS) has been shown to play physiological and biological functions as a neuro-transmitter/modulator in the central nervous system and as an endocrine factor in the periphery, through its binding to two kinds of receptors: NTSR1 and 2 (G protein-coupled receptors) and NTSR3/sortilin (a vacuolar protein-sorting 10-domain receptor). NTS also plays oncogenic roles in many types of cancer, including digestive cancers. In tumor tissues, NTS and NTSR1 expression is higher than in healthy ones and is associated with poor prognosis. NTS and NTRS1 promote cancer progression and play key functions in metastatic processes; they modulate several signaling pathways and they contribute to changes in the tumor microenvironment. Conversely, NTRS2 involvement in digestive cancers is poorly understood. Discovered for mediating NTS biological effects, sortilin recently emerged as a promising target as its expression was found to be increased in various types of cancers. Because it can be secreted, a soluble form of sortilin (sSortilin) appears as a new serum biomarker which, on the basis of recent studies, promises to be useful in both the diagnosis and tumor progression monitoring. More precisely, it appears that soluble sortilin can be associated with other receptors like TRKB. These associations occur in exosomes and trigger the aggressiveness of cancers like glioblastoma, leading to the concept of a possible composite theranostic biomarker. This review summarizes the oncogenic roles of the NTS signaling pathways in digestive cancers and discusses their emergence as promising early diagnostic and/or prognostic biomarkers and therapeutic targets.

Effect of neurotensin on cultured mouse preimplantation embryos

Previously, we revealed that neurotensin (NTS) derived from the oviduct and uterus can function during fertilization. However, little is known about NTS actions on the pre-implantation embryo after fertilization. Here, we found that pro-Nts mRNA is expressed in the oviduct and uterus during when preimplantation embryos develop and an increase in mRNA level in the uterus is induced by human chorionic gonadotropin (hCG) treatment. Expression of mRNA for two NTS receptors, Ntr1 and Ntr3, was found throughout these stages, whereas Ntr2 mRNA was not detected, suggesting that NTS signaling occurred through NTR1 and NTR3. Supplementation of 1, 10, 100 or 1000 nM NTS to embryo culture medium after fertilization showed that 100 nM NTS significantly improved the blastocyst formation. In comparison, the total number of cells and inner cell mass ratio of blastocysts was not significant different between the 0 nM and 100 nM NTS treatment groups. These results indicate that NTS has a positive effect upon preimplantation embryo development in vitro.

The role of Neurotensin and its receptors in non-gastrointestinal cancers: a review

Background

Neurotensin, originally isolated in 1973 has both endocrine and neuromodulator activity and acts through its three main receptors. Their role in promoting tumour cell proliferation, migration, DNA synthesis has been studied in a wide range of cancers. Expression of Neurotensin and its receptors has also been correlated to prognosis and prediction to treatment.

Main body

The effects of NT are mediated through mitogen-activated protein kinases, epidermal growth factor receptors and phosphatidylinositol-3 kinases amongst others. This review is a comprehensive summary of the molecular pathways by which Neurotensin and its receptors act in cancer cells.

Conclusion

Identifying the role of Neurotensin in the underlying molecular mechanisms in various cancers can give way to developing new agnostic drugs and personalizing treatment according to the genomic structure of various cancers.

GPCRs in pancreatic adenocarcinoma: Contributors to tumour biology and novel therapeutic targets

Pancreatic cancer has one of the highest mortality rates (5-year survival ~9%) among cancers. Pancreatic adenocarcinoma (PAAD) is the most common (>80%) and the most lethal type of pancreatic cancer. A need exists for new approaches to treat pancreatic adenocarcinoma. GPCRs, the largest family of cell-surface receptors and drug targets, account for ~35% of approved drugs. Recent studies have revealed roles for GPCRs in PAAD cells and cells in the tumour micro-environment. This review assesses current information regarding GPCRs in PAAD by summarizing omics data for GPCRs expression in PAAD. The PAAD "GPCRome" includes GPCRs with approved agents, thereby offering potential for their repurposing/repositioning. We then reviewed the evidence for functional roles of specific GPCRs in PAAD. We also highlight gaps in understanding the contribution of GPCRs to PAAD biology and identify several GPCRs that may be novel therapeutic targets for future work in search of GPCR-targeted drugs to treat PAAD tumours.

Neurotensin receptors regulate transactivation of the EGFR and HER2 in a reactive oxygen species-dependent manner

Neurotensin is a 13 amino acid peptide which is present in many lung cancer cell lines. Neurotensin binds with high affinity to the neurotensin receptor 1, and functions as an autocrine growth factor in lung cancer cells. Neurotensin increases tyrosine phosphorylation of the epidermal growth factor receptor (EGFR) and the neurotensin receptor 1 antagonist SR48692 blocks the transactivation of the EGFR. Here the effects of reactive oxygen species on the transactivation of the EGFR and HER2 were investigated. Using non-small cell lung cancer (NSCLC) cell lines, neurotensin receptor 1 mRNA and protein were present. Using NCI-H838 cells, neurotensin or neurotensin^8-13 but not neurotensin^1-8 increased EGFR, ERK and HER2 tyrosine phosphorylation which was blocked by SR48692. Neurotensin addition to NCI-H838 cells increased significantly reactive oxygen species which was inhibited by SR48692, Tiron (superoxide scavenger) and diphenylene iodonium (DPI inhibits the ability of NADPH oxidase and dual oxidase enzymes to produce reactive oxygen species). Tiron or DPI impaired the ability of neurotensin to increase EGFR, ERK and HER2 tyrosine phosphorylation. Neurotensin stimulated NSCLC cellular proliferation whereas the growth was inhibited by SR48692, DPI or lapatinib (lapatinib is tyrosine kinase inhibitor of the EGFR and HER2). Lapatinib inhibited the ability of the neurotensin receptor 1 to transactivate the EGFR and HER2. The results indicate that neurotensin receptor 1 regulates the transactivation of the EGFR and HER2 in a reactive oxygen species-dependent manner.

Neurotensin as a source of cyclic AMP and co-mitogen in fibrolamellar hepatocellular carcinoma

Fibrolamellar hepatocellular carcinomas (FL-HCCs) possess a unique mutation that encodes a chimeric form of protein kinase A (DNAJ-PKAc), which includes a chaperonin binding domain. DNAJ-PKAc retains most of the biochemical properties of the native enzyme, however, and activity remains dependent on cAMP. We thus speculated that a persistent source of cAMP is necessary to promote FL-HCC carcinogenesis, and that neurotensin (NTS) may drive cAMP production in this setting, given that NS serum and tumor levels are elevated in many patients with FL-HCC. We examined expression of NTS pathway components in human FL-HCCs and paired normal livers, and determined the role of NTS in driving proliferation in tumor slice cultures. Cultured hepatocytes were used to determine interactions between NTS and other proliferative pathways, and to determine the effects of NTS on cAMP production and PKA activity. We found that the NTS pathway is up-regulated in human FL-HCCs, and that NTS activates cAMP and PKA in hepatocytes. NTS increases proliferation in the presence of epidermal growth factor (EGF), and NTS-induced proliferation is dependent on NTSR1 and the EGFR/MEK pathway. We conclude that NTS serves as a co-mitogen in FL-HCC, and provides a source of cAMP to facilitate ongoing activation of DNAJ-PKAc.

KRAS, YAP, and obesity in pancreatic cancer: A signaling network with multiple loops

Pancreatic ductal adenocarcinoma (PDAC) continues to be a lethal disease with no efficacious treatment modalities. The incidence of PDAC is expected to increase, at least partially because of the obesity epidemic. Increased efforts to prevent or intercept this disease are clearly needed. Mutations in KRAS are initiating events in pancreatic carcinogenesis supported by genetically engineered mouse models of the disease. However, oncogenic KRAS is not entirely sufficient for the development of fully invasive PDAC. Additional genetic mutations and/or environmental, nutritional, and metabolic stressors, e.g. inflammation and obesity, are required for efficient PDAC formation with activation of KRAS downstream effectors. Multiple factors "upstream" of KRAS associated with obesity, including insulin resistance, inflammation, changes in gut microbiota and GI peptides, can enhance/modulate downstream signals. Multiple signaling networks and feedback loops "downstream" of KRAS have been described that respond to obesogenic diets. We propose that KRAS mutations potentiate a signaling network that is promoted by environmental factors. Specifically, we envisage that KRAS mutations increase the intensity and duration of the growth-promoting signaling network. As the transcriptional activator YAP plays a critical role in the network, we conclude that the rationale for targeting the network (at different points), e.g. with FDA approved drugs such as statins and metformin, is therefore compelling.

NT Agonist Regulates Expression of Nuclear High-affinity Neurotensin Receptors

Neurotensin (NT) exerts multiple functions in the central nervous system and peripheral tissues. Its actions are mainly mediated by a high-affinity G-protein-coupled receptor, the NT-1 receptor. In this study we demonstrated a nuclear NT binding site in different cellular models. We first noted that a large percentage of NT-1 receptor cell body immunoreactivity was located in the nuclear soma and nuclear envelope of rat substantia nigra, a brain area rich in NT-containing axon terminals. The NT-1 receptor was also visualized in purified nuclei from CHO cells stably transfected with NT-1 receptor coupled to the enhanced green fluorescence protein by immunocytochemistry. We observed that both the nuclear envelope and the nuclear soma were labeled, and the labeling intensity significantly increased after NT agonist treatment. These results suggested that NT-1 receptors, present in both the nuclear soma and the nuclear envelope, can be modulated by the ligand. Lastly, [125I]-NT binding experiments performed on isolated nuclei from a human lung cancer cell line endogenously expressing NT-1 receptor and NT, LNM35, revealed the existence of nuclear Gpp(NHp)-sensitive binding sites. These binding sites markedly decreased when cells were chronically treated with an NT-1 receptor antagonist, SR 48692. Taken together, these data suggest that the agonist regulates the expression of nuclear NT-1 receptors.

The significance of NTR1 expression and its correlation with β-catenin and EGFR in gastric cancer

BACKGROUND

Several reports indicate the high-affinity receptor of NT (neurotensin), NTR1 (neurotensin receptor 1), in numerous detrimental functions linked to neoplastic progression of several cancer types. Recently, it has also been shown that NTR1 gene is a target of the Wnt/APC oncogenic pathways connected with the β-catenin/Tcf transcriptional complex and NT can stimulate cancer proliferation in an EGFR-dependent mechanism. In this study, we explored NTR1, β-catenin and EGFR expression in gastric cancer. The possible associations of NTR1 expression with clinicopathological factors, prognosis, β-catenin and EGFR were analyzed.

METHODS

NTR1, β-catenin and EGFR expression in gastric cancer tissues and the adjacent normal tissues of 210 cases was detected by Immunohistochemistry. The possible associations of NTR1 expression with clinicopathological data, prognosis, β-catenin and EGFR were analyzed.

RESULTS

1. NTR1 expression in tumor tissues was significantly higher than that in adjacent normal tissues (P <0 .01). 2. Its expression was positively correlated with pathological grade, T stage, N stage and TNM stage and was not correlated with sex, age, tumor size and Lauren's classification. 3. A co-expression of NTR1 and nuclear β-catenin was in 53 (25.2 %) of cases and NTR1 expression was positively correlated with β-catenin nuclear translocation. NTR1 expression was not correlated with EGFR expression, but at a critical value (P = 0.05). 4. By log-rank test, higher expression of NTR1, higher pathological grade, diffusion Lauren's classification and advanced TNM stage showed worse prognosis (P <0 .05). Age, sex, tumor size, β-catenin and EGFR had no prognostic significance. Multivariate Cox analysis showed that NTR1 expression and TNM clinical stage (P <0 .05) were the independent prognostic factors for patients with GC.

CONCLUSION

By immunohistochemistry, we found that a high expression of NTR1 in GC specimens, which showed a bad prognosis, besides, NTR1 expression was related to invasion and migration of GC. These findings provide new and important information on the progression of GC. This study indicated that NTR1 may play an important role in tumor progression of GC and have its potential to be a predictive biomarker or a therapeutic molecular target in GC. The interaction between NTR1 and β-catenin may participate in the development of GC. However, the relationship between NTR1 and EGFR needs to be further investigated.

Neurotensin (NTS) and its receptor (NTSR1) causes EGFR, HER2 and HER3 over-expression and their autocrine/paracrine activation in lung tumors, confirming responsiveness to erlotinib

Alterations in the signaling pathways of epidermal growth factor receptors (HERs) are associated with tumor aggressiveness. Neurotensin (NTS) and its high affinity receptor (NTSR1) are up regulated in 60% of lung cancers. In a previous clinical study, NTSR1 overexpression was shown to predict a poor prognosis for 5 year overall survival in a selected population of stage I lung adenocarcinomas treated by surgery alone. In a second study, shown here, the frequent and high expression of NTSR1 was correlated with a pejorative prognosis in 389 patients with stage I to III lung adenocarcinoma, and was an independent prognosis marker. Interactions between NTS and NTSR1 induce pro-oncogenic biological effects associated with neoplastic processes and tumor progression. Here we highlight the cellular mechanisms activated by Neurotensin (NTS) and its high affinity receptor (NTSR1) contributing to lung cancer cell aggressiveness. We show that the NTS autocrine and/or paracrine regulation causes EGFR, HER2, and HER3 over-expression and activation in lung tumor cells. The EGFR and HER3 autocrine activation is mediated by MMP1 activation and EGF "like" ligands (HB-EGF, Neuregulin 1) release. By establishing autocrine and/or paracrine NTS regulation, we show that tumor growth is modulated according to NTS expression, with a low growth rate in those tumors that do not express NTS. Accordingly, xenografted tumors expressing NTS and NTSR1 showed a positive response to erlotinib, whereas tumors void of NTSR1 expression had no detectable response. This is consistent with the presence of a NTS autocrine loop, leading to the sustained activation of EGFR and responsible for cancer aggressiveness. We propose the use of NTS/NTSR1 tumor expression, as a biomarker for the use of EGFR tyrosine kinase inhibitors in patients lacking EGFR mutation.

Neurotensinergic augmentation of glutamate release at the perforant path-granule cell synapse in rat dentate gyrus: Roles of L-Type Ca²⁺ channels, calmodulin and myosin light-chain kinase

Neurotensin (NT) serves as a neuromodulator in the brain where it is involved in modulating a variety of physiological functions including nociception, temperature, blood pressure and cognition, and many neurological diseases such as Alzheimer's disease, schizophrenia and Parkinson's disease. Whereas there is compelling evidence demonstrating that NT facilitates cognitive processes, the underlying cellular and molecular mechanisms have not been fully determined. Because the dentate gyrus expresses high densities of NT and NT receptors, we examined the effects of NT on the synaptic transmission at the synapse formed between the perforant path (PP) and granule cells (GC) in the rats. Our results demonstrate that NT persistently increased the amplitude of the AMPA receptor-mediated EPSCs at the PP-GC synapse. NT-induced increases in AMPA EPSCs were mediated by presynaptic NTS1 receptors. NT reduced the coefficient of variation and paired-pulse ratio of AMPA EPSCs suggesting that NT facilitates presynaptic glutamate release. NT increased the release probability and the number of readily releasable vesicles with no effects on the rate of recovery from vesicle depletion. NT-mediated augmentation of glutamate release required the influx of Ca(2+) via L-type Ca(2+) channels and the functions of calmodulin and myosin light chain kinase. Our results provide a cellular and molecular mechanism to explain the roles of NT in the hippocampus.

The potential of neurotensin secreted from neuroendocrine tumor cells to promote gelsolin-mediated invasiveness of prostate adenocarcinoma cells

Neuroendocrine (NE) cells in prostate cancer have been shown to be associated with the progression of prostate cancer. However, little is known about the molecular basis of this association. We have previously demonstrated that NE cells promote metastasis of a human prostate cancer cell line (LNCaP) with overexpression of the gelsolin gene. The purpose of this study was to investigate the interactions between NE cells and LNCaP cells and the involvement of gelsolin in contributing to the invasive potential of LNCaP cells. In addition, we examined whether neurotensin induced gelsolin-mediated invasion. We used the NE cell line NE-CS that was established from the prostate of the LPB-Tag 12T-10 transgenic mouse. Small interfering RNA (siRNA) targeting gelsolin or not targeting it was transfected into LNCaP cells. Cell invasion was assessed by Matrigel invasion assay. The supernatant of NE-CS cells and neurotensin induced the transformation of LNCaP cells. Neurotensin was observed in the supernatant of NE-CS cells but not in LNCaP cells. The siRNA targeting of gelsolin resulted in inhibition of invasion of LNCaP cells in the culture medium with neurotensin added, and in the supernatant of NE-CS cells with epidermal growth factor. The invasive potential of LNCaP cells enhanced by neurotensin or the supernatant of NE-CS cells through neurotensin receptor 1 (NTSR1) was blocked by a phospholipase Cγ inhibitor and an intracellular calcium chelator, with concomitant gelsolin suppression. This study indicates that NE cells and neurotensin induce gelsolin-mediated invasion of LNCaP cells through NTSR1 activation.

The combined use of serum neurotensin and IL-8 as screening markers for colorectal cancer

This pilot study aimed to determine the feasibility of serum neurotensin/IL-8 values being used as a screening tool for colorectal cancer. Fifty-six patients and 15 healthy controls were assigned to seven groups according to their disease entity based on theater records and histology report. Blood samples for neurotensin and IL-8 were measured using an enzyme-linked immunosorbent assay. There were no differences in the clinical and biochemical parameters of patients and controls. Group (p=0.003) and age (p=0.059, marginally significant) were independent predictors of neurotensin plasma values. Neurotensin (p=0.004) and IL-8 (p=0.029) differed between healthy and colorectal cancer patients. Neurotensin values differentiate the control group from all remaining groups. The value of plasma neurotensin ≤ 54.47 pg/ml at enrollment selected by receiver operating characteristic (ROC) curves demonstrated a sensitivity of 77 %, specificity of 90 %, and an estimate of area under ROC curve (accuracy) of 85 % in predicting colorectal cancer. At enrollment, the value of plasma IL-8 ≥ 8.83 pg/ml had a sensitivity of 85 %, specificity 80 %, and an estimate of area under ROC curve (accuracy) of 81 % in predicting colorectal cancer. IL-8 should be used complementary to neurotensin due to its lower specificity. None of the colorectal cancer patients displayed a combination of high neurotensin and low IL-8 values (beyond cutoffs). It seems that a blood neurotensin/IL-8 system may be used as a screening tool for colorectal cancer, but much has to be done before it is validated in larger-scale prospective studies.

Neurotensin-induced proinflammatory signaling in human colonocytes is regulated by β-arrestins and endothelin-converting enzyme-1-dependent endocytosis and resensitization of neurotensin receptor 1

The neuropeptide/hormone neurotensin (NT) mediates intestinal inflammation and cell proliferation by binding of its high affinity receptor, neurotensin receptor-1 (NTR1). NT stimulates IL-8 expression in NCM460 human colonic epithelial cells by both MAP kinase- and NF-κB-dependent pathways. Although the mechanism of NTR1 endocytosis has been studied, the relationship between NTR1 intracellular trafficking and inflammatory signaling remains to be elucidated. In the present study, we show that in NCM460 cells exposed to NT, β-arrestin-1 (βARR1), and β-arrestin-2 (βARR2) translocate to early endosomes together with NTR1. Endothelin-converting enzyme-1 (ECE-1) degrades NT in acidic conditions, and its activity is crucial for NTR1 recycling. Pretreatment of NCM460 cells with the ECE-1 inhibitor SM19712 or gene silencing of βARR1 or βARR2 inhibits NT-stimulated ERK1/2 and JNK phosphorylation, NF-κB p65 nuclear translocation and phosphorylation, and IL-8 secretion. Furthermore, NT-induced cell proliferation, but not IL-8 transcription, is attenuated by the JNK inhibitor, JNK(AII). Thus, NTR1 internalization and recycling in human colonic epithelial cells involves βARRs and ECE-1, respectively. Our results also indicate that βARRs and ECE-1-dependent recycling regulate MAP kinase and NF-κB signaling as well as cell proliferation in human colonocytes in response to NT.

Neurotensin and its receptors in the control of glucose homeostasis

The pharmacological roles of the neuropeptide neurotensin through its three known receptors are various and complex. Neurotensin is involved in several important biological functions including analgesia and hypothermia in the central nervous system and also food intake and glucose homeostasis in the periphery. This review focuses on recent works dealing with molecular mechanisms regulating blood glucose level and insulin secretion upon neurotensin action. Investigations on crucial cellular components involved in the protective effect of the peptide on beta cells are also detailed. The role of xenin, a neurotensin-related peptide, on the regulation of insulin release by glucose-dependent insulinotropic polypeptide is summarized. The last section comments on the future research areas which should be developed to address the function of new effectors of the neurotensinergic system in the endocrine pancreas.

Neurotensin and its high affinity receptor 1 as a potential pharmacological target in cancer therapy

Cancer is a worldwide health problem. Personalized treatment represents a future advancement for cancer treatment, in part due to the development of targeted therapeutic drugs. These molecules are expected to be more effective than current treatments and less harmful to normal cells. The discovery and validation of new targets are the foundation and the source of these new therapies. The neurotensinergic system has been shown to enhance cancer progression in various cancers such as pancreatic, prostate, lung, breast, and colon cancer. It also triggers multiple oncogenic signaling pathways, such as the PKC/ERK and AKT pathways. In this review, we discuss the contribution of the neurotensinergic system to cancer progression, as well as the regulation and mechanisms of the system in order to highlight its potential as a therapeutic target, and its prospect for its use as a treatment in certain cancers.

The neurotensin receptor-1 promotes tumor development in a sporadic but not an inflammation-associated mouse model of colon cancer

Neurotensin receptor-1 (NTR-1) is overexpressed in colon cancers and colon cancer cell lines. Signaling through this receptor stimulates proliferation of colonocyte-derived cell lines and promotes inflammation and mucosal healing in animal models of colitis. Given the causal role of this signaling pathway in mediating colitis and the importance of inflammation in cancer development, we tested the effects of NTR-1 in mouse models of inflammation-associated and sporadic colon cancer using NTR-1-deficient (Ntsr1(-) (/-)) and wild-type (Ntsr1(+/+)) mice. In mice treated with azoxymethane (AOM) to model sporadic cancer, NTR-1 had a significant effect on tumor development with Ntsr1(+/+) mice developing over twofold more tumors than Ntsr1(-) (/-) mice (p = 0.04). There was no effect of NTR-1 on the number of aberrant crypt foci or tumor size, suggesting that NT/NTR-1 signaling promotes the conversion of precancerous cells to adenomas. Interestingly, NTR-1 status did not affect tumor development in an inflammation-associated cancer model where mice were treated with AOM followed by two cycles of 5% dextran sulfate sodium (DSS). In addition, colonic molecular and histopathologic analyses were performed shortly after a single cycle of DSS. NTR-1 status did not affect colonic myeloperoxidase activity or histopathologic scores for damage and inflammation. However, Ntsr1(-) (/-) mice were more resistant to DSS-induced mortality (p = 0.01) and had over twofold higher colonic expression levels of Il6 and Cxcl2 (p < 0.04), cytokines known to promote tumor development. These results represent the first direct demonstration that targeted disruption of the Ntsr1 gene reduces susceptibility to colon tumorigenesis.

The potential use of the neurotensin high affinity receptor 1 as a biomarker for cancer progression and as a component of personalized medicine in selective cancers

A growing challenge in medicine today, is the need to improve the suitability of drug treatments for cancer patients. In this field, biomarkers have become the "flags" to provide additional information in tumor biology. They are a relay between the patient and practitioner and consequently, aid in the diagnosis, providing information for prognosis, or in some cases predicting the response to specific therapies. In addition to being markers, these tumor "flags" can also be major participants in the process of carcinogenesis. Neurotensin receptor 1 (NTSR1) was recently identified as a prognosis marker in breast, lung, and head and neck squamous carcinomas. Neurotensin (NTS) was also shown to exert numerous oncogenic effects involved in tumor growth and metastatic spread. These effects were mostly mediated by NTSR1, making the NTS/NTSR1 complex an actor in cancer progression. In this review, we gather information on the oncogenic effects of the NTS/NTSR1 complex and its associated signaling pathways in order to illuminate its significant role in tumor progression and its potential as a biomarker and a therapeutic target in some tumors.

Pancreatic cancer bears overexpression of neurotensin and neurotensin receptor subtype-1 and SR 48692 counteracts neurotensin induced cell proliferation in human pancreatic ductal carcinoma cell line PANC-1

The presence of neurotensin and neurotensin receptors has been demonstrated in human pancreatic carcinomas using autoradiography and Northern blot analysis. In vitro studies have reported that the neurotensin antagonist SR 48692 could inhibit the growth of MIA PaCa-2 cells in a neurotensin mediated fashion, and neurotensin could overcome this inhibition or stimulate proliferation. However, it is currently unknown whether such actions are exerted on PANC-1 cells. In addition, the immunolocation of neurotensin and neurotensin receptors is still unclear in human pancreatic ductal carcinoma tissues. Immunohistochemistry was applied to detect the distribution of neurotensin and neurotensin receptor subtype-1 in human pancreatic ductal carcinoma and normal pancreatic tissues. Furthermore, an in vitro study was carried out to test the pharmacological profile of neurotensin and SR 48692 in human pancreatic ductal carcinoma cell line PANC-1. Compared with normal pancreatic tissues, pancreatic ductal carcinoma tissues have higher neurotensin and neurotensin receptor subtype-1 expression rates. Pancreatic ductal carcinomas (32/40) bear the expression of both neurotensin and neurotensin receptor subtype-1. We observed that neurotensin (10⁻¹¹-10⁻⁷ M) significantly stimulated the proliferation of PANC-1 and SR 48692 (10⁻¹¹-10⁻⁷ M) alone had no effect on the growth of PANC-1 cells; however, SR 48692 (10⁻¹⁰-10⁻⁶ M) inhibited the stimulatory effect of neurotensin (10⁻⁹ M). Considering the overexpression of both neurotensin and neurotensin receptor subtype-1 in pancreatic ductal carcinomas, it could enable us to develop markers for pancreatic cancer diagnosis. As SR 48692 could inhibit neurotensin induced cell growth, neurotensin receptor subtype-1 may serve as a therapeutic target for the therapy of pancreatic carcinomas. Furthermore, our study indicates that the counteraction of neurotensin and neurotensin receptor subtype-1 regulates the genesis and development of pancreatic carcinomas.

Loss of Raf-1 kinase inhibitory protein in pancreatic ductal adenocarcinoma

AIMS

Raf-1 kinase inhibitor protein (RKIP) has emerged as a significant metastatic suppressor in a variety of human cancers. The aim of this study was to evaluate RKIP expression and to determine its association with metastasis and prognostic significance in pancreatic cancer patients.

METHODS

Immunohistochemical staining for RKIP was performed on 63 cases of pancreatic ductal adenocarcinoma (PDAC). We investigated whether RKIP expression correlated with clinicopathological parameters and patient outcomes.

RESULTS

The islet cells, acinar cells and ductal epithelial cells of normal pancreas consistently showed strong RKIP immunoreactivity. In contrast, in PDAC, RKIP was lost in 57.1% (37/63) of cases. Loss of RKIP expression was significantly associated with the presence of nodal (p=0.001) and distant (p=0.010) metastases and a higher stage group (p=0.012). Univariate analysis for distant metastasis-free survival (DMFS) showed that the median DMFS of RKIP negative PDAC patients (10 months) was significantly shorter than that of RKIP positive PDAC patients (17 months; p=0.009). Multivariate analysis also revealed that loss of RKIP expression was an independent predictor of worse DMFS in PDAC patients (p=0.015).

CONCLUSIONS

Our results strongly suggest that RKIP is a metastasis suppressor in PDAC.

Protein kinase D1 promotes anchorage-independent growth, invasion, and angiogenesis by human pancreatic cancer cells

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal diseases. Novel molecularly targeted therapies are urgently needed. Here, we extended our studies on the role of protein kinase D1 (PKD1) in PDAC cell lines. Given that Panc-1 express moderate levels of PKD1, we used retroviral-mediated gene transfer to create a Panc-1 derivative that stably over-expresses PKD1 (Panc-1-PKD1). Reciprocally, we used shRNA targeting PKD1 in Panc-28 to produce a PKD1 under-expressing Panc-28 derivative (Panc-28-shPKD1). Our results demonstrate that Panc-1-PKD1 cells exhibit significantly increased anchorage-independent growth in soft agar and increased in vitro invasion compared with Panc-1-mock. Reciprocally, Panc-28-shPKD1 cells show a significant decrease in anchorage-independent growth and invasiveness, as compared with Panc-28-mock cells. The selective PKD family inhibitor CRT0066101 markedly decreased colony-forming ability and invasiveness by either Panc-1-PKD1 or Panc-28-mock cells. Secretion of the pro-angiogenic factors vascular endothelial growth factor (VEGF) and CXC chemokines (CXCL8) was significantly elevated by PKD1 over-expression in Panc-1 cells and reduced either by depletion of PKD1 via shRNA in Panc-28 cells or by addition of CRT0066101 to either Panc-1-PKD1 or Panc-28-mock cells. Furthermore, human umbilical vein endothelial cell (HUVEC) tube formation was significantly enhanced by co-culture with Panc-1-PKD1 compared with Panc-1-mock in an angiogenesis assay in vitro. Conversely, PKD1 depletion in Panc-28 cells decreased their ability to induce endotube formation by HUVECs. PDAC-induced angiogenesis in vitro and in vivo was markedly inhibited by CRT0066101. Our results lend further support to the hypothesis that PKD family members provide a novel target for PDAC therapy.

Neurotensin receptor 1 determines the outcome of non-small cell lung cancer

PURPOSE

This study aimed to investigate the role of the neurotensin/neurotensin receptor I (NTSR1) complex in non-small cell lung cancer (NSCLC) progression.

EXPERIMENTAL DESIGN

The expression of neurotensin and NTSR1 was studied by transcriptome analysis and immunohistochemistry in two series of 74 and 139 consecutive patients with pathologic stage I NSCLC adenocarcinoma. The findings were correlated with clinic-pathologic features. Experimental tumors were generated from the malignant human lung carcinoma cell line A459, and a subclone of LNM35, LNM-R. The role of the neurotensin signaling system on tumor growth and metastasis was investigated by small hairpin RNA-mediated silencing of NTSR1 and neurotensin.

RESULTS

Transcriptome analysis carried out in a series of 74 patients showed that the positive regulation of NTSR1 put it within the top 50 genes related with relapse-free survival. Immunohistochemistry revealed neurotensin- and NTSR1-positive staining in 60.4% and 59.7% of lung adenocarcinomas, respectively. At univariate analysis, NTSR1 expression was strongly associated with worse 5-year overall survival rate (P = 0.0081) and relapse-free survival (P = 0.0024). Multivariate analysis showed that patients over 65 years of age (P = 0.0018) and NTSR1 expression (P = 0.0034) were independent negative prognostic factors. Experimental tumor xenografts generated by neurotensin- and NTSR1-silenced human lung cancer cells revealed that neurotensin enhanced primary tumor growth and production of massive nodal metastasis via autocrine and paracrine regulation loops.

CONCLUSION

NTSR1 expression was identified as a potential new prognostic biomarker for surgically resected stage I lung adenocarcinomas, as NTSR1 activation was shown to participate in lung cancer progression.

Insulin-like growth factor-1 receptor transactivation modulates the inflammatory and proliferative responses of neurotensin in human colonic epithelial cells

Neurotensin (NT) is a gastrointestinal neuropeptide that modulates intestinal inflammation and healing by binding to its high-affinity receptor NTR1. The dual role of NT in inflammation and healing is demonstrated in models of colitis induced by Clostridium difficile toxin A and dextran sulfate sodium, respectively, and involves NF-κB-dependent IL-8 expression and EGF receptor-mediated MAPK activation in human colonocytes. However, the detailed signaling pathways involved in these responses remain to be elucidated. We report here that NT/NTR1 coupling in human colonic epithelial NCM460 cells activates tyrosine phosphorylation of the insulin-like growth factor-1 receptor (IGF-1R) in a time- and dose-dependent manner. NT also rapidly induces Src tyrosine phosphorylation, whereas pretreatment of cells with the Src inhibitor PP2 before NT exposure decreases NT-induced IGF-1R phosphorylation. In addition, inhibition of IGF-1R activation by either its specific antagonist AG1024 or siRNA against IGF-1 significantly reduces NT-induced IL-8 expression and NF-κB-dependent reporter gene expression. Pretreatment with AG1024 also inhibits Akt activation and apoptosis induced by NT. Silencing of Akt expression by siRNA also substantially attenuates NT-induced IL-8 promoter activity and NF-κB-dependent reporter gene expression. This is the first report to indicate that NT transactivates IGF-1R and that this response is linked to Akt phosphorylation and NF-κB activation, contributing to both pro-inflammatory and tissue repair signaling pathways in response to NT in colonic epithelial cells. We propose that IGF-1R activation represents a previously unrecognized key pathway involved in the mechanisms by which NT and NTR1 modulate colonic inflammation and inflammatory bowel disease.

Suppression of neurotensin receptor type 1 expression and function by histone deacetylase inhibitors in human colorectal cancers

Neurotensin, a gut peptide, stimulates the growth of colorectal cancers that possess the high-affinity neurotensin receptor (NTR1). Sodium butyrate (NaBT) is a potent histone deacetylase inhibitor (HDACi) that induces growth arrest, differentiation, and apoptosis of colorectal cancers. Previously, we had shown that NaBT increases nuclear GSK-3beta expression and kinase activity; GSK-3beta functions as a negative regulator of extracellular signal-regulated kinase (ERK) signaling. The purpose of our current study was to determine: (a) whether HDACi alters NTR1 expression and function, and (b) the role of GSK-3beta/ERK in NTR1 regulation. Human colorectal cancers with NTR1 were treated with various HDACi, and NTR1 expression and function were assessed. Treatment with HDACi dramatically decreased endogenous NTR1 mRNA, protein, and promoter activity. Overexpression of GSK-3beta decreased NTR1 promoter activity (> 30%); inhibition of GSK-3beta increased NTR1 expression in colorectal cancer cells, indicating that GSK-3beta is a negative regulator of ERK and NTR1. Consistent with our previous findings, HDACi significantly decreased phosphorylated ERK while increasing GSK-3beta. Selective MAP/ERK kinase/ERK inhibitors suppressed NTR1 mRNA expression in a time- and dose-dependent fashion, and reduced NTR1 promoter activity by approximately 70%. Finally, pretreatment with NaBT prevented neurotensin-mediated cyclooxygenase-2 and c-myc expression and attenuated neurotensin-induced interleukin-8 expression. HDACi suppresses endogenous NTR1 expression and function in colorectal cancer cell lines; this effect is mediated, at least in part, through the GSK-3beta/ERK pathway. The downregulation of NTR1 in colorectal cancers may represent an important mechanism for the anticancer effects of HDACi.

Role of protein kinase D signaling in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal cancers with dismal survival rates. Its intransigence to conventional therapy renders PDAC an aggressive disease with early metastatic potential. Thus, novel targets for PDAC therapy are urgently needed. Multiple signal transduction pathways are implicated in progression of PDAC. These pathways stimulate production of intracellular messengers in their target cells to modify their behavior, including the lipid-derived diacylglycerol (DAG). One of the prominent intracellular targets of DAG is the protein kinase C (PKC) family. However, the mechanisms by which PKC-mediated signals are decoded by the cell remain incompletely understood. Protein kinase D1 (PKD or PKD1, initially called atypical PKCμ), is the founding member of a novel protein kinase family that includes two additional protein kinases that share extensive overall homology with PKD, termed PKD2, and PKD3. The PKD family occupies a unique position in the signal transduction pathways initiated by DAG and PKC. PKD lies downstream of PKCs in a novel signal transduction pathway implicated in the regulation of multiple fundamental biological processes. We and others have shown that PKD-mediated signaling pathways promote mitogenesis and angiogenesis in PDAC. Our recent observations demonstrate that PKD also potentiates chemoresistance and invasive potential of PDAC cells. This review will briefly highlight diverse biological roles of PKD family in multiple neoplasias including PDAC. Further, this review will underscore our latest advancement with the development of a potent PKD family inhibitor and its effect both in vitro and in vivo in PDAC.

Activator protein-1 has an essential role in pancreatic cancer cells and is regulated by a novel Akt-mediated mechanism

Activator protein-1 (AP-1) regulates the expression of several genes involved in human tumorigenesis. However, there is little known about this transcription factor in pancreatic ductal adenocarcinoma. We recently found high levels of AP-1-binding activities and multiple AP-1/DNA complexes containing c-Jun, JunD, Fra1, and Fra2 in pancreatic cancer cells. Transient transfection assays indicated that AP-1 was functional and capable of transactivating its gene targets. Furthermore, a c-Jun transactivation mutant inhibited anchorage-dependent and anchorage-independent proliferation, suggesting that AP-1 had an essential role in pancreatic cancer cells. Our study also uncovered a novel mechanism by which protein kinase Akt controls c-Jun activity in pancreatic cancer cells. Indeed, distinct from its known ability to induce c-fos and fra1 and to stabilize c-Jun, Akt appeared to directly regulate the transcriptional activity of c-Jun independently of the phosphorylation sites targeted by c-Jun NH(2)-terminal kinase (Ser(63)/Ser(73)) and glycogen synthase kinase-3 (Thr(239)). Our data also suggest that growth factors might use this Akt-regulated mechanism to potently induce c-Jun targets such as cyclin D1. Collectively, our findings indicate that AP-1 has an important function in pancreatic cancer cells and provide evidence for a previously unknown Akt-mediated mechanism of c-Jun activation.

The neurotensin receptor-1 pathway contributes to human ductal breast cancer progression

Background

The neurotensin (NTS) and its specific high affinity G protein coupled receptor, the NT1 receptor (NTSR1), are considered to be a good candidate for one of the factors implicated in neoplastic progression. In breast cancer cells, functionally expressed NT1 receptor coordinates a series of transforming functions including cellular migration and invasion.

Methods and Results

we investigated the expression of NTS and NTSR1 in normal human breast tissue and in invasive ductal breast carcinomas (IDCs) by immunohistochemistry and RT-PCR. NTS is expressed and up-regulated by estrogen in normal epithelial breast cells. NTS is also found expressed in the ductal and invasive components of IDCs. The high expression of NTSR1 is associated with the SBR grade, the size of the tumor, and the number of metastatic lymph nodes. Furthermore, the NTSR1 high expression is an independent factor of prognosis associated with the death of patients.

Conclusion

these data support the activation of neurotensinergic deleterious pathways in breast cancer progression.

Identification of a novel therapeutic target for head and neck squamous cell carcinomas: a role for the neurotensin-neurotensin receptor 1 oncogenic signaling pathway

Distant metastasis is a major factor associated with poor prognosis in head and neck squamous cell carcinomas (HNSCC), but little is known of its molecular mechanisms. New markers that predict clinical outcome, in particular the ability of primary tumors to develop metastatic tumors, are urgently needed. Based on a genome-wide gene expression analysis using clinical specimens of HNSCC, we narrowed our focus to the analysis of the neurotensin (NTS) and neurotensin receptor 1 (NTSR1) oncogenic signal pathways. Kaplan-Meier curves and log rank tests revealed that high mRNA expression levels of NTS and NTSR1 had a significant adverse effect on metastasis-free survival rate, suggesting a contribution of this pathway in HNSCC cancer progression. In HNSCC cells, which expressed NTSR1, a NTS agonist promoted cellular invasion, migration and induction of several mRNAs, such as interleukin 8 and matrix metalloproteinase 1 transcripts. In addition, knock down of NTSR1 expression with small interfering RNAs resulted in reduction of cellular invasion and migration in HNSCC cell lines. Our findings suggest a critical role for the NTS and NTSR1 oncogenic pathways in invasion and migration of HNSCC cells during the metastatic process. Our study raises the possibility that NTS and NTSR1 could be a useful predictive marker of poor prognosis in patients with HNSCC and a molecular therapeutic target in antimetastatic strategies for HNSCCs.

Neurotensin Enhances GABAergic Activity in Rat Hippocampus CA1 Region by Modulating L-Type Calcium Channels

Neurotensin (NT) is a tridecapeptide that interacts with three NT receptors; NTS1, NTS2, and NTS3. Although NT has been reported to modulate GABAergic activity in the brain, the underlying cellular and molecular mechanisms of NT are elusive. Here, we examined the effects of NT on GABAergic transmission and the involved cellular and signaling mechanisms of NT in the hippocampus. Application of NT dose-dependently increased the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) recorded from CA1 pyramidal neurons with no effects on the amplitude of sIPSCs. NT did not change either the frequency or the amplitude of miniature (m)IPSCs recorded in the presence of tetrodotoxin. Triple immunofluorescent staining of recorded interneurons demonstrated the expression of NTS1 on GABAergic interneurons. NT increased the action potential firing rate but decreased the afterhyperpolarization (AHP) amplitude in identified CA1 interneurons. Application of L-type calcium channel blockers (nimodipine and nifedipine) abolished NT-induced increases in action potential firing rate and sIPSC frequency and reduction in AHP amplitude, suggesting that the effects of NT are mediated by interaction with L-type Ca2+channels. NT-induced increase in sIPSC frequency was blocked by application of the specific NTS1 antagonist SR48692, the phospholipase C (PLC) inhibitor U73122, the IP3receptor antagonist 2-APB, and the protein kinase C inhibitor GF109203X, suggesting that NT increases γ-aminobutyric acid release via a PLC pathway. Our results provide a cellular mechanism by which NT controls GABAergic neuronal activity in hippocampus.

Future strategies for targeted therapies and tailored patient management in pancreatic cancer

Pancreatic cancer represents the fourth leading cause of cancer-related mortality in the United States. The vast majority of patients are diagnosed at advanced stages of the disease, at which time gemcitabine-based chemotherapy is typically offered as the standard of care. However, as investigators have arrived at a greater understanding of pancreatic tumor biology, newer therapeutic agents that "target" specific pathways or molecules governing the growth, spread, and maintenance of tumor cells have gained considerable interest. Erlotinib, an orally bioavailable small molecule inhibitor of the epidermal growth factor receptor, is the first of these targeted compounds to be approved for use in combination with gemcitabine for patients with advanced pancreatic cancer. Other targeted agents, including monoclonal antibodies and small molecule inhibitors aimed at a variety of targets, also have been extensively evaluated, with limited success to date. A newer strategy worth pursuing involves tailoring an individual patient's therapy according to the molecular characteristics of both host and tumor, as has shown promise in other solid tumor types.

Neurotensin stimulates expression of early growth response gene-1 and EGF receptor through MAP kinase activation in human colonic epithelial cells

Neurotensin (NT) is a highly expressed gastrointestinal (GI) neuropeptide, which modulates GI motility, secretion and cell growth as well as intestinal inflammation. Since EGF receptor is highly expressed in human colon cancer cells, we sought to examine whether NT stimulation contributes to the EGFR overexpression using nontransformed colonocyte NCM460 cells. The results show that NT treatment caused a significant increase in EGFR protein expression and gene transcription. Pretreatment with MAP kinase pathway inhibitor PD98059 blocked NT-induced EGFR expression. As the EGFR promoter has a functional Egr-1 site, previously shown to mediate its transcription in response to hypoxia, we examined the role of Egr-1 in the NT response. We first show that NT stimulated Egr-1 expression, which can be inhibited by PD98059. We also determined whether NT increases Egr-1 binding to its site within the EGFR promoter. The data indicate that NT enhanced the amount of Egr-1 binding to the EGFR Egr-1 site and that this binding was significantly decreased by PD98059. To verify that Egr-1 mediated NT-induced EGFR transcription, Egr-1 siRNA was used to knock down its expression. The data show that transfection of Egr-1 siRNA significantly inhibited NT-stimulated EGFR transcription. Together, our results suggest that NT can stimulate MAP kinase-mediated Egr-1 and EGFR gene expression in human colonocytes. Our results may be relevant to the mechanisms by which NT participates in the development of colon cancer.

Tuberin: a stimulus-regulated tumor suppressor protein controlled by a diverse array of receptor tyrosine kinases and G protein-coupled receptors

Tuberin, a tumor suppressor protein, is involved in various cellular functions including survival, proliferation, and growth. It has emerged as an important effector regulated by receptor tyrosine kinases (RTKs) and G protein-coupled receptors (GPCRs). Regulation of tuberin by RTKs and GPCRs is highly complex and dependent on the type of receptors and their associated signaling molecules. Apart from Akt, the first kinase recognized to phosphorylate and inactivate tuberin upon growth factor stimulation, an increasing number of kinases upstream of tuberin have been identified. Furthermore, recruitment of different scaffolding adaptor components to the activated receptors appears to play an important role in the regulation of tuberin activity. More recently, the differential regulation of tuberin by various G protein family members have also been intensively studied, it appears that G proteins can both facilitate (e.g., G(i/o)) as well as inhibit (e.g., G(q)) tuberin phosphorylation. In the present review, we attempt to summarize our emerging understandings of the roles of RTKs, GPCRs, and their cross-talk on the regulation of tuberin.

Curcumin inhibits neurotensin-mediated interleukin-8 production and migration of HCT116 human colon cancer cells

PURPOSE

Neurotensin, a gut tridecapeptide, acts as a potent cellular mitogen for various colorectal and pancreatic cancers that possess high-affinity neurotensin receptors. Cytokine/chemokine proteins are increasingly recognized as important local factors that play a role in the metastasis and invasion of multiple cancers. The purpose of this study was to (a) determine the effect of neurotensin on cytokine/chemokine gene expression and cell migration in human cancer cells and (b) assess the effect of curcumin, a natural dietary product, on neurotensin-mediated processes.

EXPERIMENTAL DESIGN

The human colorectal cancer, HCT116, was treated with neurotensin, with or without curcumin, and interleukin (IL)-8 expression and protein secretion was measured. Signaling pathways, which contribute to the effects of neurotensin, were assessed. Finally, the effect of curcumin on neurotensin-mediated HCT116 cell migration was analyzed.

RESULTS

We show that neurotensin, acting through the native high-affinity neurotensin receptor, induced IL-8 expression in human colorectal cancer cells in a time- and dose-dependent fashion. This stimulation involves Ca2+-dependent protein kinase C, extracellular signal-regulated kinase-dependent activator protein-1, and extracellular signal-regulated kinase-independent nuclear factor-kappaB pathways. Curcumin inhibited neurotensin-mediated activator protein-1 and nuclear factor-kappaB activation and Ca2+ mobilization. Moreover, curcumin blocked neurotensin-stimulated IL-8 gene induction and protein secretion and, at a low concentration (i.e., 10 micromol/L), blocked neurotensin-stimulated colon cancer cell migration.

CONCLUSIONS

Neurotensin-mediated induction of tumor cell IL-8 expression and secretion may contribute to the procarcinogenic effects of neurotensin on gastrointestinal cancers. Furthermore, a potential mechanism for the chemopreventive and chemotherapeutic effects of curcumin on colon cancers may be through the inhibition of gastrointestinal hormone (e.g., neurotensin)-induced chemokine expression and cell migration.

Neurotensin phosphorylates GSK-3alpha/beta through the activation of PKC in human colon cancer cells

Neurotensin (NT), a gastrointestinal hormone, binds its receptor [neurotensin receptor (NTR)] to regulate the growth of normal and neoplastic intestinal cells; molecular mechanisms remain largely undefined. Glycogen synthase kinase-3 (GSK-3) regulates diverse cellular processes, including cell growth and apoptosis. Here, we show that NT induces the phosphorylation of GSK-3alpha/beta in the human colon cancer cell line HT29, HCT116, or SW480, which possesses high-affinity NTR. The effect of NT was blocked by inhibitors of protein kinase C (PKC), but not by inhibitors of MEK1 or phosphatidylinositol-3 kinase, suggesting a predominant role for PKC in GSK-3beta phosphorylation by NT. Pretreatment with Gö6976 (which inhibits PKCalpha and PKCbeta1) or downregulation of endogenous PKCalpha or PKCbeta1 blocked NT-mediated GSK-3beta (but not GSK-3alpha) phosphorylation. Moreover, a selective PKCbeta inhibitor, LY379196, reduced NT-mediated GSK-3beta (but not GSK-3alpha) phosphorylation, suggesting a role for PKCbeta1 in the NT-mediated phosphorylation of GSK-3beta and an undefined kinase in the NT-mediated phosphorylation of GSK-3alpha. Treatment with NT or the GSK-3 inhibitor SB216763 increased the expression of cyclin D1, a downstream effector protein of GSK-3 and a critical protein for the proliferation of various cells. Our results indicate that NT uses PKC-dependent pathways to modulate GSK-3, which may play a role in the NT regulation of intestinal cell growth.

Neurotensin and growth of normal and neoplastic tissues

Neurotensin (NT) is a brain-gut tridecapeptide that functions as a neurotransmitter/neuromodulator in the central nervous system (CNS) and as an endocrine agent in the periphery. NT has numerous physiologic effects on multiple organs. This review will focus on the effects of NT as a trophic factor for normal and neoplastic tissues. In this regard, NT may act as an endocrine agent or, in some instances, in a paracrine and/or autocrine fashion. These effects appear to be mediated predominantly through the G protein-coupled high-affinity NT receptor. However, some of the trophic effects may also be through the other two receptor subtypes, particularly the NT receptor type 3, which belongs to a recently identified family of sorting receptors. The signaling pathways mediating the effects of NT are multiple but most appear to activate the ERK signaling pathway, which then activates downstream transcription factors, ultimately leading to proliferation. NT may be a useful agent to enhance the growth of normal tissues such as the small bowel mucosa during periods of gut disuse or disease and, finally, the selective targeting of NT receptor subtypes on certain cancers may offer a novel strategy in the armamentarium of cancer chemotherapeutics.

Involvement of neurotensin in cancer growth: evidence, mechanisms and development of diagnostic tools

Focusing on the literature of the past 15 years, we evaluate the evidence that neurotensin and neurotensin receptors participate in cancer growth and we describe possible mechanisms. In addition, we review the progress achieved in the use of neurotensin analogs to image tumors in animals and humans. These exciting advances encourage us to pursue further research and stimulate us to consider novel ideas regarding the multiple inputs to cancer growth that neurotensin might influence.

On the mechanisms of 12-O-tetradecanoylphorbol-13-acetate-induced growth arrest in pancreatic cancer cells

OBJECTIVES

Protein kinase C (PKC) is involved in cell growth, differentiation, and apoptosis. We investigated the effects of the PKC activator, the tetradecanylphorbol acetate (TPA), in human pancreatic cancer cells.

METHODS

Cell proliferation was measured by thymidine incorporation. Expression of cell cycle proteins was investigated by Western blot. Real-time reverse transcriptase-polymerase chain reaction was used to measure p21 messenger RNA expression, whereas knockdown of its expression was accomplished with a specific small interferring RNA. Cell cycle phases were determined by flow cytometry.

RESULTS

TPA time and concentration dependently inhibited thymidine incorporation in Panc-1 and CD18 cells and induced G2/M cell cycle arrest. The TPA decreased cyclin A and B expression, increased cyclin E, and markedly increased the expression of p21 at both the messenger RNA and protein levels. TPA-induced p21 expression and growth inhibition were blocked by the PKC inhibitor, bisindoylmaleimide. TPA induced extracellular signal-regulated kinase1/2 phosphorylation, whereas the MEK inhibitor, PD98059, blocked the TPA-induced p21 expression. Small interferring RNA targeted to p21 blocked TPA-induced p21 protein expression but not TPA-induced cell growth arrest.

CONCLUSIONS

TPA-induced p21 expression is mediated by the MEK/ERK pathway but is not involved in TPA-induced growth inhibition. In contrast, cyclin A and cyclin B are likely involved in TPA-induced G2/M arrest because both proteins are involved in S phase and G2/M transition during cell proliferation.

Expression of Neurotensin and NT1 Receptor in Human Breast Cancer: A Potential Role in Tumor Progression

Emerging evidence supports neurotensin as a trophic and antiapoptotic factor, mediating its control via the high-affinity neurotensin receptor (NT1 receptor) in several human solid tumors. In a series of 51 patients with invasive ductal breast cancers, 34% of all tumors were positive for neurotensin and 91% positive for NT1 receptor. We found a coexpression of neurotensin and NT1 receptor in a large proportion (30%) of ductal breast tumors, suggesting a contribution of the neurotensinergic signaling cascade within breast cancer progression. Functionally expressed NT1 receptor, in the highly malignant MDA-MB-231 human breast cancer cell line, coordinated a series of transforming functions, including cellular migration, invasion, induction of the matrix metalloproteinase (MMP)-9 transcripts, and MMP-9 gelatinase activity. Disruption of NT1 receptor signaling by silencing RNA or use of a specific NT1 receptor antagonist, SR48692, caused the reversion of these transforming functions and tumor growth of MDA-MB-231 cells xenografted in nude mice. Our findings support the contribution of neurotensin in human breast cancer progression and point out the utility to develop therapeutic molecules targeting neurotensin or NT1 receptor signaling cascade. These strategies would increase the range of therapeutic approaches and be beneficial for specific patients.

Effects of peripheral inflammation on activation of ERK in the rostral ventromedial medulla

In the present study, the activation of extracellular signal-regulated kinase (ERK) in the rostral ventromedial medulla (RVM) following the injection of complete Freund's adjuvant (CFA) into the rat hindpaw was examined in order to clarify the mechanisms underlying the dynamic changes in the descending pain modulatory system after peripheral inflammation. Phospho-extracellular signal-regulated kinase-immunoreactive (p-ERK-IR) neurons were observed in the nucleus raphe magnus (NRM) and nucleus reticularis gigantocellularis pars alpha (GiA). Inflammation induced the activation of ERK in the RVM, with a peak at 7 h after the injection of CFA into the hindpaw and a duration of 24 h. In the RVM, the number of p-ERK-IR neurons per section in rats killed at 7 h after CFA injection (14.2 +/- 1.7) was significantly higher than that in the control group (4.5 +/- 0.9) [P < 0.01]. At 7 h after CFA injection, about 60% of p-ERK-IR neurons in the RVM were serotonergic neurons. The percentage of RVM serotonergic neurons that are also p-ERK positive in the rats with inflammation (20.5% +/- 2.3%) was seven times higher than that in control rats (2.7% +/- 1.4%) [P < 0.01]. These findings suggest that inflammation-induced activation of ERK in the RVM may be involved in the plasticity in the descending pain modulatory system following inflammation.

Neurotensin negatively modulates Akt activity in neurotensin receptor-1-transfected AV12 cells

Neurotensin (NT) regulates a variety of biological processes primarily through interaction with neurotensin receptor-1 (NTR1), a heterotrimeric G-protein-coupled receptor (GPCR). Stimulation of NTR1 has been linked to activation of multiple signaling transduction pathways via specific coupling to G(q), G(i/o), or G(s), in various cell systems. However, the function of NT/NTR1 in the regulation of the Akt pathway remains unknown. Here, we report that activation of NTR1 by NT inhibits Akt activity as determined by the dephosphorylation of Akt at both Ser473 and Thr308 in AV12 cells constitutively expressing human NTR1 (NTR1/AV12). The inactivation of Akt by NT was rapid and dose-dependent. This effect of NT was completely blocked by the specific NTR1 antagonist, (S)-(+)-[1-(7-chloro-4-quinolinyl)-5-(2,6-dimethoxyphenyl)pyrazol-3-yl)-carbonylamino] cyclohexylacetic acid (SR 48527), but unaffected by the less active enantiomer ((R)-(-)-[1-(7-chloro-4-quinolinyl)-5-(2,6-dimethoxyphenyl)pyrazol-3-yl)-carbonylamino] cyclohexylacetic acid (SR 49711)), indicating the stereospecificity of NTR1 in the negative regulation of Akt. In addition, NT prevented insulin- and epidermal growth factor (EGF)-mediated Akt activation. Our results provide insight into the role of NT in the modulation of Akt signaling and the potential physiological significance of Akt regulation by NT.

Low-affinity neurotensin receptor (NTS2) signaling: internalization-dependent activation of extracellular signal-regulated kinases 1/2

The role and signaling properties of the low-affinity neurotensin receptor (NTS2) are still controversial. In particular, it is unclear whether neurotensin acts as an agonist, inverse agonist, or antagonist at this site. In view of the growing evidence for a role of NTS2 in antinociception, the elucidation of the pharmacological and coupling properties of this receptor is particularly critical. In the present study, we demonstrate that in Chinese hamster ovary (CHO) cells expressing the rat NTS2 receptor, neurotensin (NT), levocabastine, neuromedin N, and the high-affinity NT receptor antagonist SR48692 [2-[[1-(-7-chloroquinolin-4-yl)-5-(2,6-dimethoxyphenyl)-1H-pyrazole-3-carbonyl]amino]adamantane-2-carboxylic acid] all bind to and activate the NTS2 receptor. This activation is followed by ligand-induced internalization of receptor-ligand complexes, as evidenced by confocal microscopy using a fluorescent NT analog. All compounds tested produced a rapid and sustained activation of extracellular signal-regulated kinases 1/2 (ERK1/2) but were without specific effect on Ca(2+) mobilization. The agonist-induced activation of ERK1/2 was completely abolished by preincubation of the cells with the endocytosis inhibitors phenylarsine oxide and monodansylcadaverine as well as overexpression of a dominant-negative mutant of dynamin 1 (DynK44A), indicating that receptor internalization was required for ERK1/2 activation. NTS2-induced activation of ERK1/2 was not species-specific, because the same agonistic effects of NT and analogs were observed in CHO cells transfected with the human NTS2 receptor. In conclusion, this study demonstrates that NTS2 is a bona fide NT receptor and that activation of this receptor by NT or NT analogs results in an internalization-dependent activation of the ERK1/2 signaling cascade.

Involvement of MAP-kinase, PI3-kinase and EGF-receptor in the stimulatory effect of Neurotensin on DNA synthesis in PC3 cells

The mechanism by which neurotensin (NT) promotes the growth of prostate cancer epithelial cells is not yet defined. Here, androgen-independent PC3 cells, which express high levels of the type 1 NT-receptor (NTR1), are used to examine the involvement of epidermal growth factor receptor (EGFR), mitogen-activated protein kinases (ERK, SAPK/JNK and p38), PI3 kinase and PKC in the mitogenic effect of NT. NT dose dependently (0.1-30 nM) enhanced phosphorylation of EGFR, ERK and Akt, reaching maximal levels within 3 min as measured by Western blotting. These effects were associated with an accumulation of EGF-like substance(s) in the medium (assayed by EGFR binding) and a 2-fold increase in DNA synthesis (assayed by [3H]thymidine incorporation). The DNA synthesis enhancement by NT was non-additive with that of EGF. The NT-induced stimulation of EGFR/ERK/Akt phosphorylation and DNA synthesis was inhibited by EGFR-tyrosine kinase inhibitors (AG1478, PD153035), metallo-endopeptidase inhibitor phosphoramidon and by heparin, but not by neutralizing anti-EGF antibody. Thus, transactivation of EGFR by NT involved heparin-binding EGF (HB-EGF or amphiregulin) rather than EGF. The effects of NT on EGFR/ERK/Akt activation and DNA synthesis were attenuated by PLC-inhibitor (U73122), PKC-inhibitors (bisindolylmaleimide, staurosporine, rottlerin), MEK inhibitor (U0126) and PI3 kinase inhibitors (wortmannin, LY 294002). We conclude that NT stimulated mitogenesis in PC3 cells by a PKC-dependent ligand-mediated transactivation of EGFR, which led to stimulation of the Raf-MEK-ERK pathway in a PI3 kinase-dependent manner.