Vasoactive intestinal peptide (VIP) induces c-fos expression in LNCaP prostate cancer cells through a mechanism that involves Ca2+ signalling. Implications in angiogenesis and neuroendocrine differentiation

Effects of curcumin and ursolic acid in prostate cancer: A systematic review

The major barriers to phytonutrients in prostate cancer therapy are non-specific mechanisms and bioavailability issues. Studies have pointed to a synergistic combination of curcumin (CURC) and ursolic acid (UA). We investigate this combination using a systematic review process to assess the most likely mechanistic pathway and human testing in prostate cancer. We used the PRISMA statement to screen titles, abstracts, and the full texts of relevant articles and performed a descriptive analysis of the literature reviewed for study inclusion and consensus of the manuscript. The most common molecular and cellular pathway from articles reporting on the pathways and effects of CURC (n = 173) in prostate cancer was NF-κB (n = 25, 14.5%). The most common molecular and cellular pathway from articles reporting on the pathways and effects of UA (n = 24) in prostate cancer was caspase 3/caspase 9 (n = 10, 41.6%). The three most common molecular and cellular pathway from articles reporting on the pathways and effects of both CURC and UA (n = 193) in prostate cancer was NF-κB (n = 28, 14.2%), Akt (n = 22, 11.2%), and androgen (n = 19, 9.6%). Therefore, we have identified the potential synergistic target pathways of curcumin and ursolic acid to involve NF-κB, Akt, androgen receptors, and apoptosis pathways. Our review highlights the limited human studies and specific effects in prostate cancer.

Heparin Oligosaccharides as Vasoactive Intestinal Peptide Inhibitors via their Binding Process Characterization

BACKGROUND

It has been proven that vasoactive intestinal peptide (VIP) was involved in the pathogenesis of prostate cancer. Cardin et al. found that by an alanine scan, the heparin- binding site on VIP was exactly the same sequence in VIP and its receptor. Therefore, heparin could competitively block the binding of VIP and its receptor. However, the structure-activity relationship between heparin and VIP has not been reported, especially in terms of the sequence and sulfation patterns of heparin oligosaccharides upon binding to VIP.

OBJECTIVE

A variety of experiments were designed to study the binding process and structure-activity relationship between heparin oligosaccharides and VIP.

METHODS

Heparin was enzymatically digested and purified to produce heparin oligosaccharides, and the structures were characterized by NMR. The binding capacity between heparin oligosaccharides and VIP was analyzed by GMSA and ITC experiments. The binding between heparin oligosaccharides and VIP was simulated using a molecular docking program to show the complex. ELISA assay was used to investigate the effect of non-anticoagulant heparin oligosaccharides on the VIP-mediated cAMP/PKA signaling pathway in vitro.

RESULTS

The results indicated that both the length and the sulfation pattern of heparin oligosaccharides affected its binding to VIP. VIP could induce the expression of cAMP at a higher level in PC3 cells, which could be regulated by the interaction of heparin oligosaccharides and VIP.

CONCLUSION

The binding between heparin oligosaccharides and VIP could block the binding between VIP and its receptor on tumor cells. Downloading the regulation of the expression level of cAMP could possibly further affect the subsequent activation of PKA. These non-anticoagulant heparin oligosaccharides may block the VIP-mediated cAMP/PKA signaling pathway and thus exert their antitumor activity.

The Role of Neuropeptide-Stimulated cAMP-EPACs Signalling in Cancer Cells

Neuropeptides are autocrine and paracrine signalling factors and mainly bind to G protein-coupled receptors (GPCRs) to trigger intracellular secondary messenger release including adenosine 3′, 5′-cyclic monophosphate (cAMP), thus modulating cancer progress in different kind of tumours. As one of the downstream effectors of cAMP, exchange proteins directly activated by cAMP (EPACs) play dual roles in cancer proliferation and metastasis. More evidence about the relationship between neuropeptides and EPAC pathways have been proposed for their potential role in cancer development; hence, this review focuses on the role of neuropeptide/GPCR system modulation of cAMP/EPACs pathways in cancers. The correlated downstream pathways between neuropeptides and EPACs in cancer cell proliferation, migration, and metastasis is discussed to glimmer the direction of future research.

Endocrine and paracrine characteristics of neuroendocrine prostate cancer

Prostate cancer is a common malignancy affecting men worldwide. While the vast majority of newly diagnosed prostate cancers are categorized as adenocarcinomas, a spectrum of uncommon tumor types occur including those with small cell and neuroendocrine cell features. Benign neuroendocrine cells exist in the normal prostate microenvironment, and these cells may give rise to primary neuroendocrine carcinomas. However, the more common development of neuroendocrine prostate cancer is observed after therapeutics designed to repress the signaling program regulated by the androgen receptor which is active in the majority of localized and metastatic adenocarcinomas. Neuroendocrine tumors are identified through immunohistochemical staining for common markers including chromogranin A/B, synaptophysin and neuron specific enolase (NSE). These markers are also common to neuroendocrine tumors that arise in other tissues and organs such as the gastrointestinal tract, pancreas, lung and skin. Notably, neuroendocrine prostate cancer shares biochemical features with nerve cells, particularly functions involving the secretion of a variety of peptides and proteins. These secreted factors have the potential to exert local paracrine effects, and distant endocrine effects that may modulate tumor progression, invasion, and resistance to therapy. This review discusses the spectrum of factors derived from neuroendocrine prostate cancers and their potential to influence the pathophysiology of localized and metastatic prostate cancer.

Role of Calcium Signaling in Prostate Cancer Progression: Effects on Cancer Hallmarks and Bone Metastatic Mechanisms

Advanced prostate cancers that progress to tumor metastases are often considered incurable or difficult to treat. The etiology of prostate cancers is multi-factorial. Among other factors, de-regulation of calcium signals in prostate tumor cells mediates several pathological dysfunctions associated with tumor progression. Calcium plays a relevant role on tumor cell death, proliferation, motility-invasion and tumor metastasis. Calcium controls molecular factors and signaling pathways involved in the development of prostate cancer and its progression. Such factors and pathways include calcium channels and calcium-binding proteins. Nevertheless, the involvement of calcium signaling on prostate cancer predisposition for bone tropism has been relatively unexplored. In this regard, a diversity of mechanisms triggers transient accumulation of intracellular calcium in prostate cancer cells, potentially favoring bone metastases development. New therapies for the treatment of prostate cancer include compounds characterized by potent and specific actions that target calcium channels/transporters or pumps. These novel drugs for prostate cancer treatment encompass calcium-ATPase inhibitors, voltage-gated calcium channel inhibitors, transient receptor potential (TRP) channel regulators or Orai inhibitors. This review details the latest results that have evaluated the relationship between calcium signaling and progression of prostate cancer, as well as potential therapies aiming to modulate calcium signaling in prostate tumor progression.

Neuroendocrine Differentiation of Prostate Cancer-An Intriguing Example of Tumor Evolution at Play

Our understanding of neuroendocrine prostate cancer (NEPC) has assumed a new perspective in light of the recent advances in research. Although classical NEPC is rarely seen in the clinic, focal neuroendocrine trans-differentiation of prostate adenocarcinoma occurs in about 30% of advanced prostate cancer (PCa) cases, and represents a therapeutic challenge. Even though our knowledge of the mechanisms that mediate neuroendocrine differentiation (NED) is still evolving, the role of androgen deprivation therapy (ADT) as a key driver of this phenomenon is increasingly becoming evident. In this review, we discuss the molecular, cellular, and therapeutic mediators of NED, and emphasize the role of the tumor microenvironment (TME) in orchestrating the phenotype. Understanding the role of the TME in mediating NED could provide us with valuable insights into the plasticity associated with the phenotype, and reveal potential therapeutic targets against this aggressive form of PCa.

Pituitary adenylate cyclase activating polypeptide acts against neovascularization in retinal pigment epithelial cells

The purpose of this study was to determine whether pituitary adenylate cyclase activating polypeptide (PACAP) could influence the neovascularization processes in hyperosmotic and oxidative stress in retinal pigment epithelial cells. Hyperosmotic conditions and oxidative stress were induced by 200 mM sucrose and 250 µM hydrogen peroxide (H₂ O₂ ), respectively. Morphology and elasticity of adult retinal pigment epithelial (ARPE-19) cells were measured by atomic force microscopy, while the investigation of junctional molecules, such as occludin and ZO-1, was carried out using immunofluorescence. For cell viability measurement, the MTT test was used. The effect of PACAP on the key angiogenic factors, such as vascular endothelial growth factor, angiogenin, and endothelin-1, was measured by an angiogenesis array and flow cytometry. Hyperosmotic stress-induced reorganization of the cytoskeleton and impairment of the junctions decreased cell viability and upregulated several angiogenic factors. In oxidative stress, we found that opening of the junctions decreased viability and upregulated the expression of angiogenic factors. PACAP was shown to be protective in both conditions. Retinal pigment epithelium cells play an important role in several diseases, such as diabetic retinopathy and macular edema. Therefore, protecting retinal pigment epithelial (RPE) cells with PACAP could be a novel and potential treatment in these diseases.

Stimulation of neuroendocrine differentiation in prostate cancer cells by GHRH and its blockade by GHRH antagonists

Prostate cancer is the second leading cause of cancer-related deaths among men in developed countries. Neuroendocrine prostate cancer, in particular, is associated with an aggressive phenotype and a poor prognosis. Neuroendocrine cells produce and secrete peptide hormones and growth factors in a paracrine/autocrine manner which promote the progression of the disease. Recent studies have demonstrated that extracellular vesicles or exosomes are released by prostate cancer cells, supporting the spread of prostate cancer. Hence, the aim of this study was to investigate the effect of growth hormone-releasing hormone (GHRH) on neuroendocrine differentiation (NED) in the androgen-dependent prostate cancer cell line LNCaP and the molecular mechanisms underlying these effects. GHRH induced an increase in the percentage of neurite-bearing cells and in the protein levels of Neuron-Specific Enolase. Both effects were blocked by the GHRH receptor antagonist MIA-690. In addition, pretreatment of these cells with the calcium chelator BAPTA, the EGFR inhibitor AG-1478 or the HER2 inhibitor AG-825 reduced the effect of GHRH, suggesting that the GHRH-induced stimulation of NED involves calcium channel activation and EGFR/HER2 transactivation. Finally, PC3-derived exosomes led to an increase in NED, cell proliferation and cell adhesion. Altogether, these findings suggest that GHRH antagonists should be considered for in the management of neuroendocrine prostate cancer.

VIP Regulates Morphology and F-Actin Distribution of Schlemm's Canal in a Chronic Intraocular Pressure Hypertension Model via the VPAC2 Receptor

Purpose

To investigate the roles of vasoactive intestinal peptides (VIPs) in regulating the morphology and F-actin distribution of Schlemm's canal (SC) of rat eyes.

Methods

Chronic intraocular pressure (IOP) hypertension models with episcleral venous cauterization (EVC) were treated with topical VIP or PG99-465 (vasoactive intestinal peptide receptors 2 [VPAC2] antagonist). IOPs were measured with Tono-Pen, and the SC parameters, including the cross-section area, circumference, and length, were statistically evaluated by hematoxylin-eosin and CD31 immunohistochemical staining. Immunofluorescence was performed to detect the distribution of F-actin in the SC. Moreover, the distribution of filamentous actin (F-actin) and globular actin (G-actin) in human umbilical vein endothelial cells (HUVECs) was studied under a pressure system by immunofluorescence and Western blotting.

Results

Increased expressions of VIP and VPAC2 receptors, as well as a disordered distribution of F-actin were found in SC endothelial cells (SCEs) in the EVC model. Moreover, topical VIP maintained the normal distribution of F-actin in SCEs, expanded the collapsed SC, and induced a significant decrease in IOP in the EVC model. In in vitro HUVECs, the F-actin/G-actin ratio increased significantly under stress stimulation for 30 minutes. A total of 50 μM VIP helped maintain the normal F-actin/G-actin ratio of HUVECs against stress stimulation.

Conclusions

VIP regulates the distribution of F-actin in SCEs via the VPAC2 receptor in order to induce a decrease in IOP. VIP may represent a new target for antiglaucoma drugs.

The Anti-tumoral Properties of Orexin/Hypocretin Hypothalamic Neuropeptides: An Unexpected Therapeutic Role

Orexins (OxA and OxB) also termed hypocretins are hypothalamic neuropeptides involved in central nervous system (CNS) to control the sleep/wake process which is mediated by two G protein-coupled receptor subtypes, OX1R, and OX2R. Beside these central effects, orexins also play a role in various peripheral organs such as the intestine, pancreas, adrenal glands, kidney, adipose tissue and reproductive tract.In the past few years, an unexpected anti-tumoral role of orexins mediated by a new signaling pathway involving the presence of two immunoreceptor tyrosine-based inhibitory motifs (ITIM) in both orexin receptors subtypes, the recruitment of the phosphotyrosine phosphatase SHP2 and the induction of mitochondrial apoptosis has been elucidated. In the present review, we will discuss the anti-tumoral effect of orexin/OXR system in colon, pancreas, prostate and other cancers, and its interest as a possible therapeutic target.

Trophoblast VIP deficiency entails immune homeostasis loss and adverse pregnancy outcome in mice

Immune homeostasis maintenance throughout pregnancy is critical for normal fetal development. Trophoblast cells differentiate into an invasive phenotype and contribute to the transformation of maternal arteries and the functional shaping of decidual leukocyte populations. Insufficient trophoblast invasion, inadequate vascular remodeling, and a loss of immunologic homeostasis are associated with pregnancy complications, such as preeclampsia and intrauterine growth restriction. Vasoactive intestinal peptide (VIP) is a pleiotropic neuropeptide synthetized in trophoblasts at the maternal-placental interface. It regulates the function of trophoblast cells and their interaction with decidual leukocytes. By means of a murine model of pregnancy in normal maternal background with VIP-deficient trophoblast cells, here we demonstrate that trophoblast VIP is critical for trophoblast function: VIP gene haploinsufficiency results in lower matrix metalloproteinase 9 expression, and reduced migration and invasion capacities. A reduced number of regulatory T cells at the implantation sites along with a lower expression of proangiogenic and antiinflammatory markers were also observed. Findings detected in the implantation sites at early stages were followed by an abnormal placental structure and lower fetal weight. This effect was overcome by VIP treatment of the early pregnant mice. Our results support the relevance of trophoblast-synthesized VIP as a critical factor in vivo for trophoblast-cell function and immune homeostasis maintenance in mouse pregnancy.-Hauk, V., Vota, D., Gallino, L., Calo, G., Paparini, D., Merech, F., Ochoa, F., Zotta, E., Ramhorst, R., Waschek, J., Leirós, C. P. Trophoblast VIP deficiency entails immune homeostasis loss and adverse pregnancy outcome in mice.

Vasoactive intestinal peptide/pituitary adenylate cyclase activating polypeptide, and their receptors and cancer

PURPOSE OF REVIEW

To summarize the roles of vasoactive intestinal peptide (VIP)/pituitary adenylate cyclase activating polypeptide (PACAP) and their receptors (VPAC1, VPAC2, PAC1) in human tumors as well as their role in potential novel treatments.

RECENT FINDINGS

Considerable progress has been made in understanding of the effects of VIP/PACAP on growth of various tumors as well as in the signaling cascades involved, especially in the role of transactivation of the epidermal growth factor family. The overexpression of VPAC1/2 and PAC1 on a number of common neoplasms (breast, lung, prostate, central nervous system and neuroblastoma) is receiving increased attention both as a means of tumor imaging the location and extent of these tumors, as well as for targeted directed treatment, by coupling cytotoxic agents to VIP/PACAP analogues.

SUMMARY

VIP/PACAP has prominent growth effects on a number of common neoplasms, which frequently overexpressed the three subtypes of their receptors. The increased understanding of their signaling cascades, effect on tumor growth/differentiation and the use of the overexpression of these receptors for localization/targeted cytotoxic delivery are all suggesting possible novel tumor treatments.

Vasoactive intestinal peptide administration after stroke in rats enhances neurogenesis and improves neurological function

The aim of this study was to investigate the effects of vasoactive intestinal peptide (VIP) on neurogenesis and neurological function after cerebral ischemia. Rats were intracerebroventricular administered with VIP after a 2h middle cerebral artery occlusion (MCAO) and sacrificed at 7, 14 and 28 days after MCAO. Functional outcome was studied with the modified neurological severity score. The infarct volume was evaluated via histology. Neurogenesis, angiogenesis and the protein expression of vascular endothelial growth factor (VEGF) were measured by immunohistochemistry and Western blotting analysis, respectively. The treatment with VIP significantly reduced the neurological severity score and the infarc volume, and increased the numbers of bromodeoxyuridine (BrdU) immunoreactive cells and doublecortin immunoreactive area in the subventricular zone (SVZ) at 7, 14 and 28 days after ischemia. The cerebral protein levels of VEGF and VEGF expression in the SVZ were also enhanced in VIP-treated rats at 7 days after stroke. VIP treatment obviously increased the number of BrdU positive endothelial cells in the SVZ and density of cerebral microvessels in the ischemic boundary at 28 days after ischemia. Our study suggests that in the ischemic rat brain VIP reduces brain damage and promotes neurogenesis by increasing VEGF. VIP-enhanced neurogenesis is associated with angiogenesis. These changes may contribute to improvement in functional outcome.

The orexin type 1 receptor is overexpressed in advanced prostate cancer with a neuroendocrine differentiation, and mediates apoptosis

AIM

In the present study, we have examined the presence of orexins and their receptors in prostate cancer (CaP) and investigated their effects on the apoptosis of prostate cancer cells.

METHODS

We have localised the orexin type 1 and 2 receptors (OX1R and OX2R) and orexin A (OxA) in CaP sections of various grades and we have quantified tumour cells containing OX1R. Expression of OX1R was evaluated in the androgeno-dependent (AD) LNCaP and the androgeno-independent (AI) DU145 prostate cancer cells submitted or not to a neuroendocrine differentiation. The effects of orexins on the apoptosis and viability of DU145 cells were also investigated.

RESULTS

OX1R is strongly expressed in carcinomatous foci exhibiting a neuroendocrine differentiation, and the number of OX1R-stained cancer cells increases with the grade of the CaP. In contrast, OX2R is only detected in scattered malignant cells in high grade CaP. OX1R is expressed in the AI DU145 cells but is undetectable in the LNCaP cells. Acquisition of a neuroendocrine phenotype by the DU145 cells is associated with an overexpression of OX1R. Orexins induce the apoptosis of DU145 cells submitted to a neuroendocrine differentiation.

CONCLUSION

The present data indicate that OX1R-driven apoptosis is overexpressed in AI CaP exhibiting a neuroendocrine differentiation opening a gate for novel therapies for these aggressive cancers which are incurable until now.

Vasoactive intestinal peptide increases VEGF expression to promote proliferation of brain vascular endothelial cells via the cAMP/PKA pathway after ischemic insult in vitro

Vasoactive intestinal peptide (VIP) enhances angiogenesis in rats with focal cerebral ischemia. In the present study, we investigated the molecular mechanism of the proangiogenic action of VIP using an in vitro ischemic model, in which rat brain microvascular endothelial cells (RBMECs) are subjected to oxygen and glucose deprivation (OGD). Western blotting and immunocytochemistry were carried out to examine the expression of VIP receptors and vascular endothelial growth factor (VEGF) in cultured RBMECs. The cell proliferation was assessed by the MTT assay. Cyclic adenosine monophosphate (cAMP) and VEGF levels were measured by using the enzyme-linked immunosorbent assay. The cultured RBMECs expressed VPAC1, VPAC2 and PAC1 receptors. Treatment with VIP significantly promoted the proliferation of RBMECs and increased OGD-induced expression of VEGF, and this effect was antagonized by the VPAC receptor antagonist VIP6-28 and VEGF antibody. VIP significantly increased contents of cAMP in RBMECs and VEGF in the culture medium. The VIP-induced VEGF production was blocked by H89, a protein kinase A (PKA) inhibitor. These data suggest that treatment with VIP promotes VEGF-mediated endothelial cell proliferation after ischemic insult in vitro, and this effect appears to be initiated by the VPAC receptors leading to activation of the cAMP/PKA pathway.

Store-operated Ca2+ entry is remodelled and controls in vitro angiogenesis in endothelial progenitor cells isolated from tumoral patients

BACKGROUND

Endothelial progenitor cells (EPCs) may be recruited from bone marrow to sustain tumor vascularisation and promote the metastatic switch. Understanding the molecular mechanisms driving EPC proliferation and tubulogenesis could outline novel targets for alternative anti-angiogenic treatments. Store-operated Ca(2+) entry (SOCE), which is activated by a depletion of the intracellular Ca(2+) pool, regulates the growth of human EPCs, where is mediated by the interaction between the endoplasmic reticulum Ca(2+)-sensor, Stim1, and the plasmalemmal Ca(2+) channel, Orai1. As oncogenesis may be associated to the capability of tumor cells to grow independently on Ca(2+) influx, it is important to assess whether SOCE regulates EPC-dependent angiogenesis also in tumor patients.

METHODOLOGY/PRINCIPAL FINDINGS

The present study employed Ca(2+) imaging, recombinant sub-membranal and mitochondrial aequorin, real-time polymerase chain reaction, gene silencing techniques and western blot analysis to investigate the expression and the role of SOCE in EPCs isolated from peripheral blood of patients affected by renal cellular carcinoma (RCC; RCC-EPCs) as compared to control EPCs (N-EPCs). SOCE, activated by either pharmacological (i.e. cyclopiazonic acid) or physiological (i.e. ATP) stimulation, was significantly higher in RCC-EPCs and was selectively sensitive to BTP-2, and to the trivalent cations, La(3+) and Gd(3+). Furthermore, 2-APB enhanced thapsigargin-evoked SOCE at low concentrations, whereas higher doses caused SOCE inhibition. Conversely, the anti-angiogenic drug, carboxyamidotriazole (CAI), blocked both SOCE and the intracellular Ca(2+) release. SOCE was associated to the over-expression of Orai1, Stim1, and transient receptor potential channel 1 (TRPC1) at both mRNA and protein level The intracellular Ca(2+) buffer, BAPTA, BTP-2, and CAI inhibited RCC-EPC proliferation and tubulogenesis. The genetic suppression of Stim1, Orai1, and TRPC1 blocked CPA-evoked SOCE in RCC-EPCs.

CONCLUSIONS

SOCE is remodelled in EPCs from RCC patients and stands out as a novel molecular target to interfere with RCC vascularisation due to its ability to control proliferation and tubulogenesis.

Vasoactive intestinal peptide (VIP) inhibits human renal cell carcinoma proliferation

Clear renal cell carcinoma (cRCC) is an aggressive and fatal neoplasm. The present work was undertaken to investigate the antiproliferative potential of vasoactive intestinal peptide (VIP) exposure on non-tumoral (HK2) and tumoral (A498, cRCC) human proximal tubular epithelial cell lines. Reverse transcription and semiquantitative PCR was used at the VIP mRNA level whereas enzyme immunoanalysis was performed at the protein level. Both renal cell lines expressed VIP as well as VIP/pituitary adenylate cyclase-activating peptide (VPAC) receptors whereas only HK2 cells expressed formyl peptide receptor-like 1 (FPRL-1). Receptors were functional, as shown by VIP stimulation of adenylyl cyclase activity. Treatment with 0.1μM VIP (24h) inhibited proliferation of A498 but not HK2 cells as based on a reduction in the incorporation of [(3)H]-thymidine and BrdU (5'-Br-2'-deoxyuridine), PCNA (proliferating-cell nuclear antigen) expression and STAT3 (signal transducer and activator of transcription 3) expression and activation. VPAC(1)-receptor participation was established using JV-1-53 antagonist and siRNA transfection. Growth-inhibitory response to VIP was related to the cyclic adenosine monophosphate (cAMP)/exchange protein directly activated by cAMP (EPAC)/phosphoinositide 3-kinase (PI3-K) signaling systems as shown by studies on adenylate cyclase stimulation, and using the EPAC-specific compound 8CPT-2Me-cAMP and specific kinase inhibitors such as H89, wortmannin and PD98059. The efficacy of VIP on the prevention of tumor progression was confirmed in vivo using xenografted athymic mouse. These actions support a potential role of this peptide and its agonists in new therapies for cRCC.

Nuclear localization of vasoactive intestinal peptide (VIP) receptors in human breast cancer

Vasoactive intestinal peptide (VIP) and its receptors (VPACs) are involved in proliferation, survival, and differentiation in human breast cancer cells. Its mechanism of action is traditionally thought to be through specific plasma membrane receptors. There is compelling evidence for a novel intracrine mode of genomic regulation by G-protein-coupled receptors (GPCRs) that implies both endocytosis and nuclear translocation of peripheral GPCR and/or the activation of nuclear-located GPCRs by endogenously-produced, non-secreted ligands. Regarding to VPAC receptors, which are GPCRs, there is only a report suggesting them as a dynamic system for signaling from plasma membrane and nuclear membrane complex. In this study, we show that VPAC(1) receptor is localized in cell nuclear fraction whereas VPAC(2) receptor presents an extranuclear localization and its protein expression is lower than that of VPAC(1) receptor in human breast tissue samples. Both receptors as well as VIP are overexpressed in breast cancer as compared to non-tumor tissue. Moreover, we report the markedly nuclear localization of VPAC(1) receptors in estrogen-dependent (T47D) and independent (MDA-MB-468) human breast cancer cell lines. VPAC(1) receptors are functional in plasma membrane and nucleus as shown by VIP stimulation of cAMP production in both cell lines. In addition, VIP increases its own intracellular and extracellular levels, and could be involved in the regulation of VPAC(1)-receptor traffic from the plasma membrane to the nucleus. These results support new concepts on function and regulation of nuclear GPCRs which could have an impact on development of new therapeutic drugs.

Vasoactive intestinal peptide behaves as a pro-metastatic factor in human prostate cancer cells

BACKGROUND

There is little known on the involvement of vasoactive intestinal peptide (VIP) in the metastatic cascade of human prostate cancer, that is, cell proliferation, cell-cell adhesion, extracellular-matrix degradation, and migration/invasion. Here we evaluated the expression of related biomarker proteins (cyclin D1, metalloproteinases MMP-2 and MMP-9, and E-cadherin) in human androgen-dependent (LNCaP) and independent (PC3) prostate cancer cells.

METHODS

Reverse transcriptase (RT)-polymerase chain reaction (PCR), gelatin zymography, Western blotting, confocal immunofluorescence microscopy, and assays on cell proliferation, adhesion, wound-healing, migration and random homing were performed.

RESULTS

VIP increased cell proliferation and cyclin D1 expression whereas it decreased cell adhesion and E-cadherin expression in LNCaP and PC3 cells. VIP enhanced the gelatinolytic activity of MMP-2 and MMP-9. Semiquantitative RT-PCR assays showed that VIP stimulated mRNA levels of these MMPs and suppressed mRNA levels of its inhibitory protein RECK. VIP promoted cell invasion and migration, and the responses were faster according to the most aggressive status in cancer progression (androgen-independence). The involvement of nuclear factor-kappaB (NF-kappaB) was demonstrated since the anti-inflammatory agent curcumin blocked VIP effects on the above biomarkers in both cell lines.

CONCLUSIONS

Taken together, these results and the presence of kappaB sites on gene promoter of cyclin D1, MMPs and, possibly, E-cadherin suggest that VIP may act as a cytokine in an early metastatic stage of human prostate cancer through the NF-kappaB/MMPs-RECK/E-cadherin system. Our findings may help to define novel targets and agents with potential usefulness in prostate cancer therapy.

Knockout of alpha-calcitonin gene-related peptide reduces cholangiocyte proliferation in bile duct ligated mice

The role of sensory innervation in the regulation of liver physiology and the pathogenesis of cholestatic liver disease are undefined. Biliary proliferation has been shown to be coordinately controlled by parasympathetic and sympathetic innervation of the liver. The aim of our study was to address the role of the sensory neuropeptide calcitonin gene-related peptide (alpha-CGRP) in the regulation of cholangiocyte proliferation during cholestasis induced by extrahepatic bile duct obstruction (BDL). Our study utilized a knockout (KO) mouse model, which lacks the sensory neuropeptide alpha-CGRP. Wild-type (WT) and alpha-CGRP KO mice were subjected to sham surgery or BDL for 3 and 7 days. In addition, immediately after BDL, WT and KO mice were administered the CGRP receptor antagonist (CGRP(8-37)) for 3 and 7 days by osmotic minipumps. Liver sections and isolated cholangiocytes were evaluated for proliferation markers. Isolated WT BDL (3 days) cholangiocytes were stimulated with alpha- and beta-CGRP and evaluated for proliferation and cAMP-mediated signaling. Lack of alpha-CGRP inhibits cholangiocyte proliferation induced by BDL at both 3 and 7 days. BDL-induced cholangiocyte proliferation in WT mice was associated with increases of circulating alpha-CGRP levels. In vitro, alpha- and beta-CGRP stimulated proliferation in purified BDL cholangiocytes, induced elevation of cAMP levels, and stimulated the activation of cAMP-dependent protein kinase A and cAMP response element binding protein DNA binding. In conclusion, sensory innervation of the liver and biliary expression of alpha-CGRP play an important role in the regulation of cholangiocyte proliferation during cholestasis.

Vasoactive intestinal peptide enhances growth and angiogenesis of human experimental prostate cancer in a xenograft model

We show that vasoactive intestinal peptide (VIP) exerts trophic and proangiogenic activities in experimental prostate cancer in vivo. Nude mice were subcutaneously injected with Matrigel impregnated with LNCaP prostate cancer cells. Cell treatment with 100 nM VIP for 1h before xenograft resulted in increased tumor growth after 8 and, more remarkably, 15 days of injection. The same occurred with the mRNA expression of the main angiogenic factor, vascular endothelial growth factor (VEGF), as shown by real-time RT-PCR quantification. The proangiogenic activity of VIP was further established by showing increases of hemoglobin levels, Masson trichromic staining, and immunohistochemical CD34 staining in tumors excised 15 days after subcutaneous injection of VIP-treated cells as compared to control conditions. All these parameters indicate that VIP increases vessel formation. This xenograft model is a useful tool to study in vivo the effects of VIP-related peptides in tumor growth and development of blood supply as well as their therapeutical potential in prostate cancer.

Nonclassic endogenous novel [corrected] regulators of angiogenesis

Angiogenesis, the process through which new blood vessels arise from preexisting ones, is regulated by several "classic" factors, among which the most studied are vascular endothelial growth factor (VEGF) and fibroblast growth factor-2 (FGF-2). In recent years, investigations showed that, in addition to the classic factors, numerous endogenous peptides play a relevant regulatory role in angiogenesis. Such regulatory peptides, each of which exerts well-known specific biological activities, are present, along with their receptors, in the blood vessels and may take part in the control of the "angiogenic switch." An in vivo and in vitro proangiogenic effect has been demonstrated for erythropoietin, angiotensin II (ANG-II), endothelins (ETs), adrenomedullin (AM), proadrenomedullin N-terminal 20 peptide (PAMP), urotensin-II, leptin, adiponectin, resistin, neuropeptide-Y, vasoactive intestinal peptide (VIP), pituitary adenylate cyclase-activating polypeptide (PACAP), and substance P. There is evidence that the angiogenic action of some of these peptides is at least partly mediated by their stimulating effect on VEGF (ANG-II, ETs, PAMP, resistin, VIP and PACAP) and/or FGF-2 systems (PAMP and leptin). AM raises the expression of VEGF in endothelial cells, but VEGF blockade does not affect the proangiogenic action of AM. Other endogenous peptides have been reported to exert an in vivo and in vitro antiangiogenic action. These include somatostatin and natriuretic peptides, which suppress the VEGF system, and ghrelin, that antagonizes FGF-2 effects. Investigations on "nonclassic" regulators of angiogenesis could open new perspectives in the therapy of diseases coupled to dysregulation of angiogenesis.

Vasoactive intestinal peptide induces cyclooxygenase-2 expression through nuclear factor-kappaB in human prostate cell lines Differential time-dependent responses in cancer progression

The effect of vasoactive intestinal peptide (VIP) on cyclooxygenase-2 (COX-2) expression was analyzed in human prostate non-neoplastic (RWPE-1) as well as cancer androgen-dependent (LNCaP) and independent (PC3) cells. The three cell lines expressed VIP mRNA and VIP peptide, as measured by RT-PCR and immunochemistry, which supports an autocrine/paracrine action of VIP in the prostate gland. VIP levels were progressively higher from non-neoplastic to androgen-dependent and independent cells. Real-time RT-PCR and Western-blotting showed that VIP stimulated both COX-2 mRNA and protein expression in a faster manner as prostate cancer stage progressed (i.e. RWPE1<LNCaP<PC3 cells). Furthermore, VIP induced higher levels of COX-2 protein expression in cancer cells as compared with non-neoplastic cells. The anti-inflammatory agent curcumin blocked VIP-induced COX-2 expression in all cell lines studied supporting the involvement of nuclear factor-kappaB (NFkappaB) in such a response. In fact, VIP increased the translocation of the NFkappaB p50 subunit to the nucleus and the binding of the active form to its target gene promoter, as measured by Western-blotting and ELISA, respectively. VIP provoked faster responses according to the most aggressive status in cancer progression (androgen-independent situation). These results together with the existence of two NFkappaB sites in the COX-2 gene promoter together suggest that COX-2 may be a target for VIP in prostate cancer progression. On the other hand, VIP could be a proinflammatory cytokine acting through the NFkappaB/COX-2 system.

Hypoxia regulation of expression and angiogenic effects of vasoactive intestinal peptide (VIP) and VIP receptors in LNCaP prostate cancer cells

Vascular endothelial growth factor (VEGF) is a main factor promoting neovascularization (angiogenesis) of solid tumours as prostate carcinoma. Hypoxia stimulates VEGF gene expression by activating the hypoxia-inducible factor-1 (HIF-1alpha). In the present study, the hypoxia-mimicking agent Ni(2+) induced vasoactive intestinal peptide (VIP) expression at both mRNA and peptide levels but it did not modify the expression of VIP receptors (VPAC(1), VPAC(2) and PAC(1) receptors) in androgen-dependent human LNCaP prostate cancer cells. VIP increased the mRNA levels of VPAC(1) and PAC(1) receptors whereas it decreased VPAC(2) receptor mRNA level. These features support that hypoxia up-regulation of VIP gene expression in prostatic carcinoma may lead to VIP regulation of the expression of its receptors by means of autocrine/paracrine mechanisms. Either VIP or hypoxia mimetics with Ni(2+) increased VEGF expression whereas both conditions together resulted in an additive response. It suggests two independent mechanisms for the observed pro-angiogenic activities of VIP and hypoxia. VIP did not stimulate HIF-1alpha mRNA expression but increased the translocation of HIF-1alpha from the cytosolic compartment to the cell nucleus. Moreover, VIP was unable to modify the expression of the HIF-1alpha inhibitor FIH-1 discarding the possibility of an indirect effect of VIP on HIF-1 transactivation.