Prostaglandin E2 and vasoactive intestinal peptide increase vascular endothelial cell growth factor mRNAs in lung cancer cells

Biochemical pharmacology of adenylyl cyclases in cancer

Globally, despite extensive research and pharmacological advancement, cancer remains one of the most common causes of mortality. Understanding the signaling pathways involved in cancer progression is essential for the discovery of new drug targets. The adenylyl cyclase (AC) superfamily comprises glycoproteins that regulate intracellular signaling and convert ATP into cyclic AMP, an important second messenger. The present review highlights the involvement of ACs in cancer progression and suppression, broken down for each specific mammalian AC isoform. The precise mechanisms by which ACs contribute to cancer cell proliferation and invasion are not well understood and are variable among cancer types; however, AC overactivation, along with that of downstream regulators, presents a potential target for novel anticancer therapies. The expression patterns of ACs in numerous cancers are discussed. In addition, we highlight inhibitors of AC-related signaling that are currently under investigation, with a focus on possible anti-cancer strategies. Recent discoveries with small molecules regarding more direct modulation AC activity are also discussed in detail. A more comprehensive understanding of different components in AC-related signaling could potentially lead to the development of novel therapeutic strategies for personalized oncology and might enhance the efficacy of chemoimmunotherapy in the treatment of various cancers.

The role of vasoactive intestinal peptide in pulmonary diseases

Vasoactive intestinal peptide (VIP) is an abundant neurotransmitter in the lungs and other organs. Its discovery dates back to 1970. And VIP gains attention again due to the potential application in COVID-19 after a research wave in the 1980s and 1990s. The diverse biological impacts of VIP extend beyond its usage in COVID-19 treatment, encompassing its involvement in various pulmonary and systemic disorders. This review centers on the function of VIP in various lung diseases, such as pulmonary arterial hypertension, chronic obstructive pulmonary disease, asthma, cystic fibrosis, acute lung injury/acute respiratory distress syndrome, pulmonary fibrosis, and lung tumors. This review also outlines two main limitations of VIP as a potential medication and gathers information on extended-release formulations and VIP analogues.

Signal Transduction by VIP and PACAP Receptors

Homeostasis of the human immune system is regulated by many cellular components, including two neuropeptides, VIP and PACAP, primary stimuli for three class B G protein-coupled receptors, VPAC1, VPAC2, and PAC1. Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) regulate intestinal motility and secretion and influence the functioning of the endocrine and immune systems. Inhibition of VIP and PACAP receptors is an emerging concept for new pharmacotherapies for chronic inflammation and cancer, while activation of their receptors provides neuroprotection. A small number of known active compounds for these receptors still impose limitations on their use in therapeutics. Recent cryo-EM structures of VPAC1 and PAC1 receptors in their agonist-bound active state have provided insights regarding their mechanism of activation. Here, we describe major molecular switches of VPAC1, VPAC2, and PAC1 that may act as triggers for receptor activation and compare them with similar non-covalent interactions changing upon activation that were observed for other GPCRs. Interhelical interactions in VIP and PACAP receptors that are important for agonist binding and/or activation provide a molecular basis for the design of novel selective drugs demonstrating anti-inflammatory, anti-cancer, and neuroprotective effects. The impact of genetic variants of VIP, PACAP, and their receptors on signalling mediated by endogenous agonists is also described. This sequence diversity resulting from gene splicing has a significant impact on agonist selectivity and potency as well as on the signalling properties of VIP and PACAP receptors.

Vasoactive intestinal peptide shapes first-trimester placenta trophoblast, vascular, and immune cell cooperation

BACKGROUND AND PURPOSE

Extravillous trophoblast (EVT) cells are responsible for decidual stromal invasion, vascular transformation, and the recruitment and functional modulation of maternal leukocytes in the first-trimester pregnant uterus. An early disruption of EVT function leads to placental insufficiency underlying pregnancy complications such as preeclampsia and fetal growth restriction. Vasoactive intestinal peptide (VIP) is a vasodilating and immune modulatory factor synthesized by trophoblast cells. However, its role in first-trimester placenta has not been explored. Here, we tested the hypothesis that VIP is involved in first-trimester EVT outgrowth, spiral artery remodelling, balancing angiogenesis, and maintenance of immune homeostasis.

EXPERIMENTAL APPROACH

First-trimester placental tissue (five to nine weeks of gestation) was collected, and was used for EVT outgrowth experiments, immunofluorescence, isolation of decidual natural killer (dNK) cells and decidual macrophages (dMA), and functional assays. Peripheral blood monocytes were differentiated with GM-CSF and used for angiogenesis assays.

KEY RESULTS

In decidua basalis, VIP+ EVT were observed sprouting from cell columns and lining spiral arterioles. EVT migrating from placental explants were also VIP+. VIP increased EVT outgrowth and IL-10 release, whereas it decreased pro-inflammatory cytokine production in EVT, dNK cells, and dMA. VIP disrupted endothelial cell networks, both directly and indirectly via an effect on macrophages.

CONCLUSION AND IMPLICATIONS

The results suggest that VIP assists the progress of EVT invasion and vessel remodelling in first-trimester placental bed in an immunologically "silent" milieu. The effects of VIP in the present ex vivo human placental model endorse its potential as a therapeutic candidate for deep placentation disorders.

Catecholamines facilitate VEGF-dependent angiogenesis via β2-adrenoceptor-induced Epac1 and PKA activation

Chronic stress has been associated with the progression of cancer and antagonists for β-adrenoceptors (βAR) are regarded as therapeutic option. As they are also used to treat hemangiomas as well as retinopathy of prematurity, a role of endothelial β₂AR in angiogenesis can be envisioned. We therefore investigated the role of β₂AR-induced cAMP formation by analyzing the role of the cAMP effector molecules exchange factor directly activated by cAMP 1 (Epac1) and protein kinase A (PKA) in endothelial cells (EC). Epac1-deficient mice showed a reduced amount of pre-retinal neovascularizations in the model of oxygen-induced retinopathy, which is predominantly driven by vascular endothelial growth factor (VEGF). siRNA-mediated knockdown of Epac1 in human umbilical vein EC (HUVEC) decreased angiogenic sprouting by lowering the expression of the endothelial VEGF-receptor-2 (VEGFR-2). Conversely, Epac1 activation by β₂AR stimulation or the Epac-selective activator cAMP analog 8-p-CPT-2’-O-Me-cAMP (8-pCPT) increased VEGFR-2 levels and VEGF-dependent sprouting. Similar to Epac1 knockdown, depletion of the monomeric GTPase Rac1 decreased VEGFR-2 expression. As Epac1 stimulation induces Rac1 activation, Epac1 might regulate VEGFR-2 expression through Rac1. In addition, we found that PKA was also involved in the regulation of angiogenesis in EC since the adenylyl cyclase (AC) activator forskolin (Fsk), but not 8-pCPT, increased sprouting in Epac1-depleted HUVEC and this increase was sensitive to a selective synthetic peptide PKA inhibitor. In accordance, β₂AR- and AC-activation, but not Epac1 stimulation increased VEGF secretion in HUVEC.

Our data indicate that high levels of catecholamines, which occur during chronic stress, prime the endothelium for angiogenesis through a β₂AR-mediated increase in endothelial VEGFR-2 expression and VEGF secretion.

Harnessing cAMP signaling in musculoskeletal regenerative engineering

This paper reviews the most recent findings in the search for small molecule cyclic AMP analogues regarding their potential use in musculoskeletal regenerative engineering.

Gender differences in hypoxic acclimatization in cyclooxygenase-2-deficient mice

The aim of this study was to determine the effect of cyclooxygenase‐2 (COX‐2) gene deletion on the adaptive responses during prolonged moderate hypobaric hypoxia. Wild‐type (WT) and COX‐2 knockout (KO) mice of both genders (3 months old) were exposed to hypobaric hypoxia (~0.4 ATM) or normoxia for 21 days and brain capillary densities were determined. Hematocrit was measured at different time intervals; brain hypoxia‐inducible factor ‐1α (HIF‐1α), angiopoietin 2 (Ang‐2), brain erythropoietin (EPO), and kidney EPO were measured under normoxic and hypoxic conditions. There were no gender differences in hypoxic acclimatization in the WT mice and similar adaptive responses were observed in the female KO mice. However, the male KO mice exhibited progressive vulnerability to prolonged hypoxia. Compared to the WT and female KO mice, the male COX‐2 KO mice had significantly lower survival rate and decreased erythropoietic and polycythemic responses, diminished cerebral angiogenesis, decreased brain accumulation of HIF‐1α, and attenuated upregulation of VEGF, EPO, and Ang‐2 during hypoxia. Our data suggest that there are physiologically important gender differences in hypoxic acclimatization in COX‐2‐deficient mice. The COX‐2 signaling pathway appears to be required for acclimatization in oxygen‐limiting environments only in males, whereas female COX‐2‐deficient mice may be able to access COX‐2‐independent mechanisms to achieve hypoxic acclimatization.

PACAP and VIP Inhibit the Invasiveness of Glioblastoma Cells Exposed to Hypoxia through the Regulation of HIFs and EGFR Expression

Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) through the binding of vasoactive intestinal peptide receptors (VIPRs), perform a wide variety of effects in human cancers, including glioblastoma multiforme (GBM). This tumor is characterized by extensive areas of hypoxia, which triggers the expression of hypoxia-inducible factors (HIFs). HIFs not only mediate angiogenesis but also tumor cell migration and invasion. Furthermore, HIFs activation is linked to epidermal growth factor receptor (EGFR) overexpression. Previous studies have shown that VIP interferes with the invasive nature of gliomas by regulating cell migration. However, the role of VIP family members in GBM infiltration under low oxygen tension has not been clarified yet. Therefore, in the present study we have investigated, for the first time, the molecular mechanisms involved in the anti-invasive effect of PACAP or VIP in U87MG glioblastoma cells exposed to hypoxia induced by treatment with desferrioxamine (DFX). The results suggest that either PACAP or VIP exert an anti-infiltrative effect under low oxygen tension by modulating HIFs and EGFR expression, key elements involved in cell migration and angiogenesis. These peptides act through the inhibition of PI3K/Akt and MAPK/ERK signaling pathways, which are known to have a crucial role in HIFs regulation.

Age-related decline of autocrine pituitary adenylate cyclase-activating polypeptide impairs angiogenic capacity of rat cerebromicrovascular endothelial cells

Aging impairs angiogenic capacity of cerebromicrovascular endothelial cells (CMVECs) promoting microvascular rarefaction, but the underlying mechanisms remain elusive. PACAP is an evolutionarily conserved neuropeptide secreted by endothelial cells and neurons, which confers important antiaging effects. To test the hypothesis that age-related changes in autocrine PACAP signaling contributes to dysregulation of endothelial angiogenic capacity, primary CMVECs were isolated from 3-month-old (young) and 24-month-old (aged) Fischer 344 x Brown Norway rats. In aged CMVECs, expression of PACAP was decreased, which was associated with impaired capacity to form capillary-like structures, impaired adhesiveness to collagen (assessed using electric cell-substrate impedance sensing [ECIS] technology), and increased apoptosis (caspase3 activity) when compared with young cells. Overexpression of PACAP in aged CMVECs resulted in increased formation of capillary-like structures, whereas it did not affect cell adhesion. Treatment with recombinant PACAP also significantly increased endothelial tube formation and inhibited apoptosis in aged CMVECs. In young CMVECs shRNA knockdown of autocrine PACAP expression significantly impaired tube formation capacity, mimicking the aging phenotype. Cellular and mitochondrial reactive oxygen species production (dihydroethidium and MitoSox fluorescence, respectively) were increased in aged CMVECs and were unaffected by PACAP. Collectively, PACAP exerts proangiogenic effects and age-related dysregulation of autocrine PACAP signaling may contribute to impaired angiogenic capacity of CMVECs in aging.

Vasoactive intestinal peptide receptor-based imaging and treatment of tumors (Review)

Vasoactive intestinal peptide receptors (VIPRs) are members of the G-protein-coupled receptor superfamily. These receptors are overexpressed in many common malignant tumors and play a major role in the progression and angiogenesis of a number of malignancies. Therefore, VIPRs may be a valuable target for the molecular imaging of tumors and therapeutic interventions. The specific natural ligand or its analogs can be labeled with a radionuclide and used for tumor receptor imaging, which could be used to visualize VIPR-related surface protein expression in vivo and to monitor the in vivo effects of molecular drugs on tumors. Moreover, the involvement of VIPRs in malignant transformation and angiogenesis renders them potential therapeutic targets for cancer treatment. A variety of VIP antagonists and cytotoxic VIP conjugates have been synthesized and evaluated for VIPR-targeted molecular therapy. The importance of VIPRs in tumor biology and the ability to predict responses to targeted therapy and monitor drug interventions suggest that VIP receptor-based imaging and treatment will be critical for the early diagnosis and management of cancer. Here, we review the current literature regarding VIPRs and their natural ligands and the involvement of VIPRs in tumor growth and angiogenesis, with an emphasis on the present use of VIPRs for the molecular imaging of tumors and therapies targeting VIPRs.

Honokiol augments the anti-cancer effects of oxaliplatin in colon cancer cells

Oxaliplatin is an important drug in the chemotherapy of colorectal carcinoma, but its toxicity, especially dose-related neurosensory toxicity, is not well tolerated. In this study, we investigated whether honokiol could augment the anti-tumor effect of oxaliplatin in colon cancer HT-29 cells in vitro and whether honokiol could be used with oxaliplatin to decrease oxaliplatin dose. We used the normal colon cells, human colonic epithelial cells (HCoEpiCs) as control cells. Cell proliferation, apoptosis, prostaglandin E2 (PGE2) and vascular endothelial growth factor (VEGF) levels were also investigated. Expression levels of cyclo-oxygenase 2 (COX-2), VEGF, AKT/p-AKT, extracellular signal-related kinase (ERK)1/2/p-ERK1/2, nuclear factor kappa B (NF-κB) P65/p-P65, and caspase-3 were measured. Honokiol or oxaliplatin suppressed the proliferation of HT-29 cells in a concentration-dependent manner, but only high concentrations of honokiol would suppress the proliferation of HCoEpiCs. HT-29 cells were more sensitive to oxaliplatin treatment in the presence of honokiol. Oxaliplatin combined with honokiol improved the apoptosis rate of HT-29 cell and reduced PGE2 and VEGF secretion levels. Expression levels of COX-2 and VEGF protein and phosphorylation of AKT, ERK1/2, and NF-κB P65 were also inhibited. Caspase-3 levels were upregulated after honokiol treatment. Therefore, honokiol can be used in combination with oxaliplatin in the chemotherapy of colon cancer. This combination allows a reduction in oxaliplatin dose, and thereby reduces its adverse effects. It may also enhance the chemotherapeutic effect of oxaliplatin for this disease.

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.

Involvement of COX-2/PGE2 signalling in hypoxia-induced angiogenic response in endothelial cells

To evaluate the impact of hypoxia on the angiogenic capability of endothelial cells (ECs), and further investigate whether the cyclooxygenase-2 (COX-2)/prostaglandin E(2) (PGE(2)) signalling is involved in the angiogenic response of ECs to hypoxia. We explored the impact of various periods (1, 3, 6, 12, 24 hrs) of hypoxia (2% O(2)) on human umbilical vein endothelial cells (HUVECs) in vitro. We observed cell viability, migration, tube formation, analysed COX-2, vascular endothelial growth factor (VEGF), AQP1 mRNA transcription, protein expression and measured PGE(2), VEGF protein concentration in cell supernatants. Then we treated HUVECs with COX-2 selective inhibitor NS398, EP1/2 combined antagonist AH6809 and exogenous PGE(2) to investigate the role of COX-2/PGE(2) signalling in the angiogenic response of ECs to hypoxia. The results demonstrated that short-term hypoxic treatment enhanced HUVECs proliferation, migration, tube formation, significantly up-regulated COX-2, VEGF, AQP1 mRNA level, protein expression and promoted PGE(2) , VEGF release. The pharmacological inhibition study revealed that exposure of HUVEC to NS398 and AH6809 under hypoxia impaired the biological responses of ECs to hypoxia. Exogenous PGE(2) augments the effects of hypoxia on HUVECs, and partially reversed the inhibitory effects of NS398 on HUVECs proliferation and angiogenic capability. Short-term hypoxic treatment enhanced angiogenic capability of ECs, and COX-2/PGE(2) signalling may play a critical role in the biological response of ECs to hypoxia.

Inactivation of capsaicin-sensitive nerves reduces pulmonary remodeling in guinea pigs with chronic allergic pulmonary inflammation

Pulmonary remodeling is an important feature of asthma physiopathology that can contribute to irreversible changes in lung function. Although neurokinins influence lung inflammation, their exact role in the extracellular matrix (ECM) remodeling remains to be determined. Our objective was to investigate whether inactivation of capsaicin-sensitive nerves modulates pulmonary ECM remodeling in animals with chronic lung inflammation. After 14 days of capsaicin (50 mg/kg, sc) or vehicle administration, male Hartley guinea pigs weighing 250-300 g were submitted to seven inhalations of increasing doses of ovalbumin (1, 2.5, and 5 mg/mL) or saline for 4 weeks. Seventy-two hours after the seventh inhalation, animals were anesthetized and mechanically ventilated and the lung mechanics and collagen and elastic fiber content in the airways, vessels and lung parenchyma were evaluated. Ovalbumin-exposed animals presented increasing collagen and elastic fiber content, respectively, in the airways (9.2 ± 0.9; 13.8 ± 1.2), vessels (19.8 ± 0.8; 13.4 ± 0.5) and lung parenchyma (9.2 ± 0.9; 13.8 ± 1.2) compared to control (P < 0.05). Capsaicin treatment reduced collagen and elastic fibers, respectively, in airways (1.7 ± 1.1; 7.9 ± 1.5), vessels (2.8 ± 1.1; 4.4 ± 1.1) and lung tissue (2.8 ± 1.1; 4.4 ± 1.1) of ovalbumin-exposed animals (P < 0.05). These findings were positively correlated with lung mechanical responses to antigenic challenge (P < 0.05). In conclusion, inactivation of capsaicin-sensitive nerve fibers reduces pulmonary remodeling, particularly collagen and elastic fibers, which contributes to the attenuation of pulmonary functional parameters.

Dithiolethione modified valproate and diclofenac increase E-cadherin expression and decrease proliferation of non-small cell lung cancer cells

The effects of dithiolethione modified valproate, diclofenac and sulindac on non-small cell lung cancer (NSCLC) cells were investigated. Sulfur(S)-valproate and S-diclofenac at 1 microg/ml concentrations significantly reduced prostaglandin (PG)E(2) levels in NSCLC cell lines A549 and NCI-H1299 as did the COX-2 inhibitor DuP-697. In vitro, S-valproate, S-diclofenac and S-sulindac half-maximally inhibited the clonal growth of NCI-H1299 cells at 6, 6 and 15 microg/ml, respectively. Using the MTT assay, 10 microg/ml S-valproate, NO-aspirin and Cay10404, a selective COX-2 inhibitor, but not SC-560, a selective COX-1 inhibitor, inhibited the growth of A549 cells. In vivo, 18mg/kg i.p. of S-valproate and S-diclofenac, but not S-sulindac, significantly inhibited A549 or NCI-H1299 xenograft proliferation in nude mice, but had no effect on the nude mouse body weight. The mechanism by which S-valproate and S-diclofenac inhibited the growth of NSCLC cells was investigated. Nitric oxide-aspirin but not S-valproate caused apoptosis of NSCLC cells. By Western blot, S-valproate and S-diclofenac increased E-cadherin but reduced vimentin and ZEB1 (a transcriptional suppressor of E-cadherin) protein expression in NSCLC cells. Because S-valproate and S-diclofenac inhibit the growth of NSCLC cells and reduce PGE(2) levels, they may prove beneficial in the chemoprevention and/or therapy of NSCLC.

Vasoactive intestinal peptide in rats with focal cerebral ischemia enhances angiogenesis

We studied the effect of vasoactive intestinal peptide (VIP) on angiogenesis in the ischemic boundary area after focal cerebral ischemia. Adult male Sprague-Dawley rats underwent middle cerebral artery occlusion for 2 h. A single dose of VIP was given via i.c.v. injection at the beginning of reperfusion. Immunohistochemistry and Western blotting were performed to assay angiogenesis and brain levels of vascular endothelial growth factor (VEGF) protein, respectively. In addition, the expression of VEGF and its receptors (flt-1 and flk-1), as well as endothelial proliferation, was measured using rat brain microvascular endothelial cells. Immunohistochemical analyses revealed significant (P<0.05) increases in the numbers of bromodeoxyuridine (BrdU) positive endothelial cells and microvessels at the boundary of the ischemic lesion in rats treated with VIP compared with rats treated with saline. Western blotting analysis showed that treatment with VIP significantly (P<0.05) raised VEGF levels in the ischemic hemisphere. In addition, treatment with VIP increased flt-1 and flk-1 immunoreactivity in endothelial cells. In vitro, incubation with VIP significantly (P<0.01) increased the proliferation of endothelial cells and induced the expression of VEGF, flt-1 and flk-1 in endothelial cells. The stimulatory effect of VIP on the proliferation of endothelial cells was significantly (P<0.01) inhibited by SU5416, a selective inhibitor of VEGF receptor tyrosine kinase. Our data suggest that treatment with VIP enhances angiogenesis in the ischemic brain, and this effect may be mediated by increases in levels of VEGF and its receptors.

Adenylyl cyclase/cAMP system involvement in the antiangiogenic effect of somatostatin in the retina. Results from transgenic mice

Neoangiogenesis is a response to retinal hypoxia that is inhibited by somatostatin (SRIF) through its subtype 2 receptor (sst2). Using a mouse model of hypoxia-induced retinopathy, we investigated whether inhibition of adenylyl cyclase (AC) is involved in SRIF anti-angiogenic actions. Hypoxia increased AC responsiveness in wild type (WT) retinas and in retinas lacking sst2, but not in sst2-overexpressing retinas. Hypoxia also altered AC isoform expression with different patterns depending on sst2 expression level. The AC VII isoform mRNA and protein resulted the most affected. Indeed, in hypoxia AC VII expression was enhanced in WT retinas and it was further increased in sst2-lacking retinas, whereas in sst2 overexpressing retinas the increase of AC VII was lower than in WT retinas. These data suggest an involvement of AC/cAMP in mediating both hypoxia-evoked retinal neoangiogenesis and SRIF protective actions. The AC VII isoform is a candidate to a main role in these mechanisms.

Protein-mediated assembly of nanodiamond hydrogels into a biocompatible and biofunctional multilayer nanofilm

Aqueous dispersible detonation nanodiamonds (NDs) with a diameter of 2-8 nm were assembled into a closely packed ND multilayer nanofilm with positively charged poly-L-lysine via the layer-by-layer deposition technique. The innate biocompatibility of the NDs in both free-floating and thin-film forms was confirmed via cellular gene expression examination by real-time polymerase chain reaction as well as MTT and DNA fragmentation assays. The highly biologically amenable ND nanofilm was successfully integrated with therapeutic molecules, and the functionality of the composite drug-ND material was assessed via interrogation of the suppression of inflammatory cytokine release. Knockdown of lipopolysaccharide-mediated inflammation was observed through the potent attenuation of tumor necrosis factor-alpha, interleukin-6, and inducible nitric oxide synthase levels following ND nanofilm interfacing with RAW 264.7 murine macrophages. Furthermore, basal cytokine secretion levels were assessed to examine innate material biocompability, revealing unchanged cellular inflammatory responses which strongly supported the relevance of the NDs as effective treatment platforms for nanoscale medicine. In addition to the easy preparation, robustness, and fine controllability of the film structures, these hybrid materials possess enormous potential for biomedical applications such as localized drug delivery and anti-inflammatory implant coatings and devices, as demonstrated in vitro in this work.

Trophic factors in the carotid body

The aim of the present study is to provide a review of the expression and action of trophic factors in the carotid body. In glomic type I cells, the following factors have been identified: brain-derived neurotrophic factor, glial cell line-derived neurotrophic factor, artemin, ciliary neurotrophic factor, insulin-like growth factors-I and -II, basic fibroblast growth factor, epidermal growth factor, transforming growth factor-alpha and -beta1, interleukin-1beta and -6, tumour necrosis factor-alpha, vascular endothelial growth factor, and endothelin-1 (ET-1). Growth factor receptors in the above cells include p75LNGFR, TrkA, TrkB, RET, GDNF family receptors alpha1-3, gp130, IL-6Ralpha, EGFR, FGFR1, IL1-RI, TNF-RI, VEGFR-1 and -2, ETA and ETB receptors, and PDGFR-alpha. Differential local expression of growth factors and corresponding receptors plays a role in pre- and postnatal development of the carotid body. Their local actions contribute toward producing the morphologic and molecular changes associated with chronic hypoxia and/or hypertension, such as cellular hyperplasia, extracellular matrix expansion, changes in channel densities, and neurotransmitter patterns. Neurotrophic factor production is also considered to play a key role in the therapeutic effects of intracerebral carotid body grafts in Parkinson's disease. Future research should also focus on trophic actions on carotid body type I cells by peptide neuromodulators, which are known to be present in the carotid body and to show trophic effects on other cell populations, that is, angiotensin II, adrenomedullin, bombesin, calcitonin, calcitonin gene-related peptide, cholecystokinin, erythropoietin, galanin, opioids, pituitary adenylate cyclase-activating polypeptide, atrial natriuretic peptide, somatostatin, tachykinins, neuropeptide Y, neurotensin, and vasoactive intestinal peptide.

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.

Vasoactive intestinal peptide-camptothecin conjugates inhibit the proliferation of breast cancer cells

The effects of vasoactive intestinal peptide-camptothecin (VIP-CPT) conjugates were investigated on breast cancer cells and cells transfected with VIP receptors (R). (Ala(2,8,9,19,24.25.27), Nle(17), Lys(28))VIP, (A-NL-K)VIP, was synthesized and Lys(28) was coupled to a linker, N-methyl-amino-ethyl-glycine, L2, which formed a carbamate bond with CPT. The resulting (A-NL-K)VIP-L2-CPT was cytotoxic for MCF7 breast cancer cells, which have VPAC(1)-R, with IC(50) values of 380 and 90 nM using the MTT and clonogenic assays, respectively. (A-NL-K)VIP, (A-NL-K)VIP-L2 and (A-NL-K)VIP-L2-CPT inhibited specific binding of (125)I-VIP to 3T3 cells transfected with VPAC(1)-R with IC(50) values of 1.9, 56 and 126 nM, respectively. In contrast, (A-NL-K)VIP, (A-NL-K)VIP-L2 and (A-NL-K)VIP-L2-CPT inhibited specific binding of (125)I-Ro25-1553 to 3T3 cells transfected with VPAC(2)-R with IC(50) values of 3.9, 3162 and 2690 nM, respectively. (A-NL-K)VIP, (A-NL-K)VIP-L2 and (A-NL-K)VIP-L2-CPT caused increased cAMP after addition to MCF7 cells. (125)I-(A-NL-K)VIP-L2-CPT was internalized by MCF7 cells at 37 degrees C but not 4 degrees C. These results indicate that (A-NL-K)VIP-L2-CPT is a VPAC(1)-R agonist which is cytotoxic for breast cancer cells.

Vasoactive intestinal peptide (VIP) increases vascular endothelial growth factor (VEGF) expression and secretion in human breast cancer cells

Previous studies have shown that vasoactive intestinal peptide (VIP) and its receptors (VPAC(1) and VPAC(2) receptors) are involved in promotion and growth of many human tumours including breast cancer. Here we investigated whether VIP regulates the expression of the main angiogenic factor, vascular endothelial cell growth factor (VEGF) in human oestrogen-dependent (T47D) and oestrogen-independent (MDA-MB-4687) breast cancer cells. Semiquantitative and quantitative real-time RT-PCRs were used at mRNA level whereas enzyme immunoanalysis was performed at protein level. Both cancer cell lines expressed VIP and VPAC(1) (but not VPAC(2)) receptors that were functional as shown by VIP stimulation of adenylate cyclase activity. VIP induced VEGF expression at both mRNA and protein levels following a time-dependent pattern. The responses were faster in T47D than in MDA-MB-468 cells. The observed VIP regulation of VEGF expression appears to be modulated at least by the cAMP/protein kinase A (PKA) and the phosphoinositide 3-kinase (PI3-K) signalling systems as shown by studies of adenylate cyclase stimulation and using specific kinase inhibitors such as H89 and wortmannin. These actions suggest a proangiogenic potential of VIP in breast cancer.

Chemoprevention of colorectal cancer - a new target needed?

OBJECTIVE

Novel treatments for colorectal cancer (CRC) include chemoprevention. Nonsteroidal anti-inflammatory drugs (NSAIDs) were the first to be studied and an inverse association was proven between their use and the development of invasive CRC. The numerous side effects of NSAIDs led, however, to the search for safer drugs. These have included Coxibs (selective COX-2 inhibitors). In this study, the role of coxibs in the chemoprevention of CRC is reviewed.

RESULTS

Numerous in-vitro and in-vivo experiments have shown the effectiveness of coxibs in the chemoprevention of CRC. These have led to the registration of celecoxib by the USA Food and Drug Administration for the treatment of familial adenomatous polyposis. Further studies of coxibs have revealed an increased risk of serious cardiovascular events when compared with placebo. This finding has considerably decreased the opportunities for chemoprevention of CRC.

CONCLUSION

The multi-directional activity of coxibs, which was the reason for their effectiveness against CRC development may be the key to proposing a new target area for chemoprevention. It has been shown that celecoxib partly inhibits the activity of NF-kappaB, transcription factor involved in inflammation and carcinogenesis pathways. Modulation of its activation may be the future of effective CRC chemoprevention.

Nonclassic Endogenous Novel 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.

Single periocular injection of celecoxib-PLGA microparticles inhibits diabetes-induced elevations in retinal PGE2, VEGF, and vascular leakage

PURPOSE

To determine whether celecoxib inhibits VEGF secretion from ARPE-19 cells and to investigate further the safety and effectiveness of periocular celecoxib-poly (lactide-co-glycolide; PLGA) microparticles in inhibiting elevations in retinal PGE(2), VEGF, and blood-tissue barrier leakage at the end of 60 days in a streptozotocin diabetic rat model.

METHODS

VEGF mRNA and protein expression in ARPE-19 cells was evaluated in the presence of 0 to 10 microM celecoxib, and cytotoxicity of celecoxib on ARPE-19 and RF6A cells was evaluated over a 0- to 100-microM concentration range. Celecoxib-PLGA microparticles were prepared by a modified solvent evaporation technique, sterilized by 25 kGy of gamma-irradiation, and characterized for size, zeta potential, drug loading, and in vitro release. Normal and streptozotocin-diabetic male Sprague-Dawley rats were divided into five groups: normal, diabetic, diabetic+placebo, normal+celecoxib, and diabetic+celecoxib. Phosphate-buffered saline (PBS) containing celecoxib-PLGA microparticles, placebo PLGA microparticles, or plain PBS in one eye was injected into the posterior subconjunctival (periocular) space in rats under anesthesia. Sixty days after administration, the animals were killed, and retinal PGE2 secretion, VEGF protein, and blood-retinal barrier leakage were estimated. Blood cell counts, blood chemistry and histology were used to assess the safety of the microparticulate system.

RESULTS

Celecoxib (up to 25 microM) did not cause significant cytotoxicity in ARPE-19 or RF6A cells. Nanomolar concentrations of celecoxib reduced VEGF mRNA and VEGF protein secretion. Celecoxib-PLGA microparticles (diameter: 1140 +/- 15 nm), containing 14.93% +/- 0.21% of celecoxib sustained in vitro drug release and in vivo drug levels in the retina for 60 days. Diabetes elevated PGE2 secretion, VEGF protein, the vitreous-plasma protein ratio, and blood-retinal barrier leakage by 3-, 1.7-, 3.1-, and 2.7-fold, and celecoxib-PLGA microparticles significantly reduced these elevations by 40%, 50%, 40%, and 50%, respectively. Neither the placebo-treated eyes nor the contralateral eyes in celecoxib-PLGA microparticle-treated rats showed significant effects. Celecoxib-PLGA or placebo-PLGA particles had no effect on the body weight or blood sugar level of rats. The celecoxib-PLGA microparticles did not cause any changes in blood cell counts or chemistry and caused no histopathological damage to the retina or periocular tissues.

CONCLUSIONS

Nanomolar concentrations of celecoxib can inhibit VEGF mRNA and protein expression from ARPE-19 cells. Periocular celecoxib microparticles are useful sustained drug delivery systems for inhibiting diabetes-induced elevations in PGE2, VEGF, and blood-retinal barrier leakage. The periocular celecoxib-PLGA microparticles are safe and do not cause any damage to the retina.

Carbonyl Reductase Expression and Its Clinical Significance in Non-Small-Cell Lung Cancer

Carbonyl reductase (CBR) is a cytosolic NADPH-dependent oxidoreductase metabolizing prostaglandins, steroids, quinines, and anthracycline antibiotics. Many experimental studies have shown that CBR plays important roles in the regulation of tumor progression, but clinical significance of CBR status remains unclear. Thus, we conducted a retrospective study on CBR mRNA expression in lung cancer. Tumor tissues obtained from 59 non-small-cell lung cancer patients were analyzed by quantitative real-time reverse transcription-PCR assay to reveal clinical significance of CBR expression. Angiogenesis was measured immunohistochemically as intratumoral microvessel density (IMVD) using anti-CD34 monoclonal antibody CD34-IMVD) and anti-CD105 monoclonal antibody (CD105-IMVD). CBR mRNA expression was significantly reduced along with progression of primary tumors (the mean CBR mRNA/GAPDH mRNA, 3.288x10(-2) for pT1, 1.628x10(-2) for pT2, and 1.175x10(-2) for pT3-4 disease, respectively; P=0.02). Moreover, CBR mRNA expression in tumor with nodal involvement seemed to be reduced as compared with that in tumor without nodal involvement (the mean CBR mRNA/GAPDH mRNA, 1.446x10(-2) and 2.531x10(-2), respectively), whereas the difference did not reach a statistical significance (P=0.09). The mean CD105-IMVD for CBR-high tumor was 59.2, which was significantly lower than that for CBR-low tumor (130.6, P=0.02), whereas no significant difference between the mean CD34-IMVDs for CBR-high tumor and CBR-low tumor was found. The 5-year survival rate of CBR-high patients was 68.3%, significantly higher than that of CBR-low patients (36.5%; P=0.03). A multivariate analysis confirmed that CBR-high expression was a significant factor to predict a favorable prognosis (P=0.04; relative risk, 0.39; 95% confidence interval, 0.16-0.98). Expression of CBR mRNA was a significant prognostic factor in non-small-cell lung cancer and was inversely associated with tumor progression and angiogenesis.

Effect of c-fos antisense probe on prostaglandin E2 -induced upregulation of vascular endothelial growth factor mRNA in human liver cancer cells

AIM: To examine the effect of prostaglandin E₂ (PGE₂) on the expression of vascular endothelial growth factor (VEGF) mRNA in the human hepatocellular carcinoma (HCC) HepG2 cells and the possible involvement of c-fos protein in this process.

METHODS: Human HCC HepG2 cells were divided into three groups treated respectively with PGE₂, a combination of PGE₂ and c-fos antisense oligodeoxynucleotide (ASO), and PGE₂ plus c-fos sense oligodeoxynucleotide (SO). The expression of VEGF mRNA in HepG2 cells after different treatments was detected by reverse transcriptase-polymerase chain reaction (RT-PCR). The relative expression level of VEGF mRNA in HepG2 cells in each group was measured.

RESULTS: Administration of PGE₂ resulted in an increased expression of c-fos and VEGF mRNA in HepG2 cells. The relative expression level of c-fos mRNA reached the peak at 3 h (68.44.7%) after PGE₂ treatment, which was significantly higher than that at 0 h (20.6±1.7%, P<0.01). Whereas, the highest expression level of VEGF mRNA was observed at 6 h (100.5±6.1%) after PGE₂treatment, which was significantly higher than that at 0 h (33.2±2.4%, P<0.01). C-fos ASO significantly reduced PGE₂-induced VEGF mRNA expression in HepG2 cells.

CONCLUSION: PGE₂ increases the expression and secretion of VEGF in HCC cells by activating the transcription factor c-fos, promotes the angiogenesis of HCC and plays an important role in the pathogenesis of liver cancer.

Cyclooxygenase-2 activation mediates the proangiogenic effect of nitric oxide in colorectal cancer

PURPOSE

Up-regulation of both inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) enzymes has been reported in colorectal cancer. We aimed at evaluating the possible interaction between the nitric oxide and COX-2 pathways, and its effect on promoting tumor angiogenesis.

EXPERIMENTAL DESIGN

Expression of iNOS, COX-2, vascular endothelial growth factor (VEGF), and CD31 was analyzed in tumor samples and corresponding normal mucosa obtained from 46 surgical specimens. We also evaluated iNOS activity, prostaglandin E(2) (PGE(2)), cyclic GMP and cyclic AMP production in the same specimens. Nitrite/nitrate levels, and PGE(2) and VEGF production were assessed in HCT116 and HT29 colon cancer cell lines after induction and selective inhibition of the two enzyme pathways.

RESULTS

A significant correlation was found between iNOS and COX-2 immunohistochemical expression. PGE(2) production significantly correlated with iNOS activity and cGMP levels. A significant correlation was also found among PGE(2) production, microvessel density, and VEGF expression. Coinduction of both iNOS and COX-2 activities occurred after lipopolysaccharide (LPS) and epidermal growth factor (EGF) treatment in HCT116 and HT29 cells. Inhibition of iNOS by 1400W significantly reduced both LPS- and EGF-induced PGE(2) production. Treatment with LPS, EGF, and arachidonic acid significantly increased VEGF production in the iNOS-negative/COX-2-positive HT29 cells. This effect was completely reversed by treatment with the selective COX-2 inhibitor celecoxib.

CONCLUSIONS

Our data showed a prominent role of nitric oxide in stimulating COX-2 activity in colorectal cancer. This interaction is likely to produce a cooperative effect in promoting angiogenesis through PGE(2)-mediated increase in VEGF production.

Bombesin-like peptides and associated receptors within the brain: distribution and behavioral implications

As we commemorate the 25th anniversary of the journal Peptides, it is timely to review the functional significance of the bombesin (BB)-like peptides and receptors in the CNS. Over two decades ago we published an article in the journal Peptides demonstrating that BB-like peptides are present in high densities in certain rat brain regions (such as the paraventricular nucleus of the hypothalamus). Subsequently, one of the mammalian forms of BB, gastrin-releasing peptide (GRP) containing cell bodies were found in the suprachiasmatic nucleus of the hypothalamus and nucleus of the solitary tract of the hindbrain. Another related peptide, namely neuromedin (NM)B, was detected in the olfactory bulb and dentate gyrus. BB and GRP bind with high affinity to BB(2) receptors, whereas NMB binds with high affinity to BB(1) receptors. The actions of BB or GRP are blocked by BB(2) receptor antagonists such as (Psi(13,14)-Leu(14))BB whereas PD168368 is a BB(1) receptor antagonist. Exogenous administration of BB into the rat brain causes hypothermia, hyperglycemia, grooming and satiety. BB-like peptides activate the sympathetic nervous system and appear to modulate stress, fear and anxiety responses. GRP and NMB modulate distinct biological processes through discrete brain regions or circuits, and globally these peptidergic systems may serve in an integrative or homeostatic function.

Emerging drugs for non-small cell lung cancer

Lung cancer is the leading cause of cancer death in the world. Therapeutic improvements caused by recent cytotoxic agents seem to have reached a plateau. New therapeutic strategies are, therefore, necessary to improve the cure rate. These include receptor-targeted therapy, signal transduction or cell-cycle inhibition, angiogenesis inhibitors, cyclooxygenase-2 (COX-2) inhibitors, gene therapy and vaccines. The antiepidermal growth factor receptor (EGFR) group includes compounds acting on the extracellular domain of EGFR, such as IMC-C225 and trastuzumab; small molecules inhibiting EGFR phosphorylation, such as ZD 1839 and OSI-774; or compounds that interfere with one of the downstream steps, such as mitogen-activated protein kinase kinase (MEK) inhibitors. Farnesyl transferase inhibitors, such as SCH66336, and protein kinase C inhibitors, such as ISIS 3521, have also shown antitumour activity. Antiangiogenesis inhibitors include matrix metalloprotease inhibitors (MMPIs), suchs as marimastat, AG3340, BAY 12-9566, BMS-275291 and Col-3. Antiangiogenic agents offer great potential for the treatment of lung cancer, as shown in preclinical models, whereas emerging data suggest that there are limits to their use as monotherapy in advanced disease. Molecules targeting vascular endothelial growth factor (VEGF) or its receptor (VEGFR) also seem to control tumour progression and may prolong survival. COX-2 inhibitors are another class of agents currently under evaluation in clinical trials for their chemoprevention role in subjects at high lung cancer risk, and also in patients with non-small cell lung cancer (NSCLC) in combination with standard chemotherapeutics. Genetic and immunologic therapies represent two additional promising modalities. All of these therapies are in different phases of clinical testing and have shown encouraging activity alone or in combination with chemotherapy drugs.

The future of cyclooxygenase-2 inhibitors and other inhibitors of the eicosanoid signal pathway in the prevention and therapy of lung cancer

Recent advances in the understanding of the biology and molecular biology of lung cancer has provided targets for novel therapeutic and chemoprevention strategies. The eicosanoid/prostaglandin signal pathway is involved in the metabolism of membrane phospholipids to end products that are involved in apoptosis, proliferation, differentiation, and angiogenesis. Abnormalities in this pathway occur frequently in lung cancer, including the overexpression of cytoplasmic phospholipase A2, cyclooxygenase-2 (COX-2), prostaglandin E (PGE) synthase, PGE2, 5-lipoxygenase (LOX), 8-LOX, and 12-LOX. Increased levels of PGE2, 5-LOX, 8-LOX, and 12-LOX promote tumor proliferation and angiogenesis and inhibit apoptosis. On the other hand, levels of proapoptotic, antiangiogenic, and antiproliferative products are frequently decreased in lung cancer due to decreased levels of enzymes such as prostacyclin synthase. These abnormalities provide a rationale for the use of inhibitors of overexpressed enzymes or replacement of anticarcinogenic end products, and such agents have been studied in preclinical and clinical trials.

Autocrine/paracrine action of pituitary vasoactive intestinal peptide on lactotroph hyperplasia induced by estrogen

Vasoactive intestinal polypeptide (VIP) content is increased in the hyperplastic pituitaries of estrogen (E)-treated rats, thus suggesting that this neuropeptide could mediate the E effect on lactotrophs. E also decreases pituitary TGF-beta1 content, an autocrine/paracrine inhibitor of lactotroph proliferation, and induces pituitary angiogenesis. To elucidate the role of VIP in this context, lactotroph hyperplasia was induced in female Fisher 344 rats by implanting sc pellets of diethylstilbestrol (DES). Twenty-five days later, the rats were treated with three different increasing doses of a VIP receptor antagonist or the vehicle for 5 d. DES treatment resulted in a marked increase of serum prolactin (PRL), pituitary PRL content, PRL mRNA expression, pituitary weight, and pituitary proliferating cell nuclear antigen. DES treatment also increased pituitary VIP content and VIP mRNA levels, but not in the hypothalamus and cerebral cortex. Simultaneously, DES treatment decreased the pituitary TGF-beta1 content and increased the pituitary content of vascular endothelial growth factor. VIP receptor antagonist partially reverted the effect of DES on serum PRL and pituitary PRL, proliferating cell nuclear antigen, TGF-beta1, and vascular endothelial growth factor contents, as well as on pituitary weight, in a dose-dependent relation. These data suggest that pituitary VIP mediates the effect of E on lactotroph hyperplasia, pituitary TGF-beta1, and angiogenesis.

Lung cancer chemoprevention: moving from concept to a reality

Vast numbers of individuals who have stopped smoking have already been exposed to critical amounts of tobacco combustion products and are at significant risk of developing lung cancer. If these individuals are diagnosed with regional or distant metastatic disease this condition is not typically curable with existing systemic therapy. The need for more effective tools to detect and intervene with early lung cancer detection is a pressing public health priority. A major challenge in this regard is the development of safe and effective lung cancer chemoprevention. The factors influencing the development of this new clinical tool are reviewed in the context of existing trends for lung cancer care. Existing pharmaceutical efforts have involved evaluation of existing treatments for advanced cancer or other disorders in early lung cancer. The paper describes approaches to tailor chemoprevention development specifically to the biological, pharmacological and anatomical realities of this most lethal cancer.

PGE(2) is generated by specific COX-2 activity and increases VEGF production in COX-2-expressing human pancreatic cancer cells

In some cancers cyclooxygenase (COX) inhibition appears to be anti-mitogenic and anti-angiogenic, but the actions of COX-derived prostaglandins in pancreatic cancer (PaCa) are unknown. In this study COX-2 was detected in three of six PaCa cell lines while COX-1 was identified in all cell lines. COX-2 expression correlated with basal and arachidonic acid (AA) stimulated PGE(2) production. PGE(2) production was inhibited by the COX-2 inhibitor nimesulide. In COX-2 expressing cells, exogenous AA and PGE(2) increased VEGF synthesis via the EP(2) receptor. Whereas PGE(2) stimulated intracellular cAMP formation in COX-2 positive and negative cells, 8-bromo cAMP stimulated VEGF production only in COX-2 expressing cells. Stimulating COX-2 expressing PaCa cell lines with AA enhanced migration of endothelial cells, an effect which was inhibited by a COX-2 inhibitor and EP(2) receptor antagonist. These data identify a subset of human PaCa cell lines that express functional COX-2 enzyme. PGE(2) generated by specific COX-2 activity increases VEGF secretion in human PaCa cells through an autocrine mechanism.

A wholly nutritional 'multifocal angiostatic therapy' for control of disseminated cancer

A great deal of effort is now being devoted to the development of new drugs that hopefully will control the spread of inoperable cancer by safely inhibiting tumor-evoked angiogenesis. However, there is growing evidence that certain practical nutritional measures have the potential to slow tumor angiogenesis, and it is reasonable to anticipate that, by combining several measures that work in distinct but complementary ways to impede the angiogenic process, a clinically useful 'multifocal angiostatic therapy' (MAT) might be devised. Several measures which might reasonably be included in such a protocol are discussed below, and include: a low-fat, low-glycemic index vegan diet, which may down-regulate the systemic IGF-I activity that supports angiogenesis; supplemental omega-3-rich fish oil, which has been shown to inhibit endothelial expression of Flk-1, a functionally crucial receptor for VEGF, and also can suppress tumor production of pro-angiogenic eicosanoids; high-dose selenium, which has recently been shown to inhibit tumor production of VEGF; green tea polyphenols, which can suppress endothelial responsiveness to both VEGF and fibroblast growth factor; and high-dose glycine, whose recently reported angiostatic activity may reflect inhibition of endothelial cell mitosis, possibly mediated by activation of glycine-gated chloride channels. In light of evidence that tumor-evoked angiogenesis has a high requirement for copper, copper depletion may have exceptional potential as an angiostatic measure, and is most efficiently achieved with the copper-chelating drug tetrathiomolybdate. If logistical difficulties make it difficult to acquire this experimental drug, high-dose zinc supplementation can achieve a slower depletion of the body's copper pool, and in any case can be used as maintenance therapy to maintain an adequate level of copper depletion. A provisional protocol is offered for a nutritionally based MAT entailing a vegan diet and supplemental intakes of fish oil, selenium, green tea polyphenols, glycine, and zinc. Inasmuch as cox-2 is overexpressed in many cancers, and cAMP can boost tumor production of various angiogenic factors as well as autogenous growth factors, adjunctive use of cox-2-specific NSAIDS may be warranted in some cases.

CAI inhibits the growth of small cell lung cancer cells

The effects of carboxyamido-triazole (CAI) on small cell lung cancer (SCLC) cells were investigated. Using SCLC cell lines NCI-H209 or H345, 20 micro M CAI had little effect on basal cytosolic Ca(2+) but inhibited the ability of 10 nM bombesin (BB) or 1 nM neurotensin (NT) to elevate cytosolic Ca(2+). Also, CAI, impaired the ability of BB or NT to cause tyrosine phosphorylation of focal adhesion kinase. In contrast, CAI did not affect the ability of (125I-Tyr(4))BB or 125I-NT to bind with high affinity to NCI-H345 cells. These results indicate that CAI impairs SCLC second messenger activation, but not neuropeptide receptor binding. Using a MTT growth assay, CAI inhibited the proliferation of NCI-H209 or H345 cells in a concentration-dependent manner with little proliferation occurring using 100 micro M CAI. Also, CAI inhibited colony formation of NCI-H209 or H345 cells in a dose-dependent manner in vitro. In vivo, CAI (2 mg/day by gavage) inhibited significantly NCI-H209 xenograft proliferation in nude mice. Animals treated daily with CAI had significantly reduced CD31 immunostaining of microvessels in the tumor. Also, CAI inhibited the increase in vascular endothelial cell growth factor (VEGF) mRNA after addition of BB to SCLC cells. These results suggest that CAI inhibits the growth of SCLC cells as well as the angiogenesis of SCLC tumors in a VEGF-dependent manner.

VIP and PACAP receptors coupled to adenylyl cyclase in human lung cancer: a study in biopsy specimens

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are important neuropeptides in the control of lung physiology. Both of these commonly bind to specific G protein coupled receptors named VPAC(1)-R and VPAC(2)-R, and PAC(1)-R (with higher affinity for PACAP). VIP and PACAP have been implicated in the control of cell proliferation and tumor growth. This study examined the presence of VIP and PACAP receptors in human lung cancer samples, as well as the functionality of adenylyl cyclase (AC) stimulated by both peptides. Results from RT-PCR and immunoblot experiments showed the expression of VPAC(1)-, VPAC(2)- and PAC(1)-R in lung cancer samples. Immunohistochemical studies showed the expression of VPAC(1) and VPAC(2) receptors. These receptors were positively coupled to AC, but the enzyme activity was impaired as compared to normal lung. There were no changes in Galpha(s) or Galpha(i) levels. Present results contribute to a better knowledge of VIP/PACAP actions in lung cancer and support the interest for the development of VIP/PACAP analogues with therapeutic roles.

VIP as a trophic factor in the CNS and cancer cells

The effects of vasoactive intestinal peptide (VIP) on the proliferation of central nervous system (CNS) and cancer cells were investigated. VIP has important actions during CNS development. During neurogenesis, VIP stimulates the proliferation and differentiation of brain neurons. Addition of VIP to embryonic mouse spinal cord cultures increases neuronal survival and activity dependent neurotrophic factor (ADNF) secretion from astroglial cells. VIP is an integrative regulator of brain growth and development during neurogenesis and embryogenesis. Also, VIP causes increased proliferation of human breast and lung cancer cells in vitro. VIP binds with high affinity to cancer cells, elevates the cAMP and increases gene expression of c-fos, c-jun, c-myc and vascular endothelial cell growth factor. The effects of VIP on cancer cells are reversed by VIPhybrid, a synthetic VPAC(1) receptor antagonist. VIPhyb inhibits the basal growth of lung cancer cells in vitro and tumors in vivo and potentiates the ability of chemotherapeutic drugs to kill cancer cells. Due to the high density of VPAC(1) receptors in cancer cells, VIP has been radiolabeled with 123I, 18F and 99mTc to image tumors. It remains to be determined if radiolabeled VIP analogs will be useful agents for early detection of cancer in patients.

PACAP-27 tyrosine phosphorylates mitogen activated protein kinase and increases VEGF mRNAs in human lung cancer cells

The effects of pituitary adenylate cyclase activating polypeptide (PACAP) on human lung cancer cell line NCI-1299 mitogen activated protein kinase (MAPK) tyrosine phosphorylation and vascular endothelial cell growth factor (VEGF) expression were investigated. PACAP-27 (100 nM) increased MAPK tyrosine phosphorylation 3-fold, 5 min after addition to NCI-H1299 cells. PACAP caused tyrosine phosphorylation in a concentration-dependent manner being half-maximal at 10 nM PACAP-27. PACAP-27 or PACAP-38 (100 nM) but not PACAP28-38 or VIP caused increased MAPK tyrosine phosphorylation using NCI-H1299 cells. Also, the increase in MAPK tyrosine phosphorylation caused by PACAP-27 was totally inhibited by 10 microM PACAP(6-38), a PAC(1) receptor antagonist or 10 microM PD98059, a MAPKK inhibitor. These results suggest that PAC(1) receptors regulate tyrosine phosphorylation of MAPK in a MAPKK-dependent manner. PACAP-27 (100 nM) caused increased VEGF mRNA in NCI-H1299 cells after 8 h. The increase in VEGF mRNA caused by PACAP-27 was partially inhibited by PACAP(6-38), PD98059 and H-89. Addition of VIP to NCI-H1299 cells caused increased VEGF mRNA, which was totally inhibited by H89, a PKA inhibitor. These results suggest that PAC(1) and VPAC(1) receptors regulate VEGF expression in lung cancer cells.

AH6809 antagonizes non-small cell lung cancer prostaglandin receptors

The effects of prostaglandin (PG)E2 on lung cancer cells were investigated. 3H-PGE2 bound with high affinity to membranes derived from small cell lung cancer (SCLC) and non-SCLC (NSCLC) cell lines. Using NSCLC NCI-H1299 membranes, specific 3H-PGE2 binding to NCI-H1299 membranes was inhibited with moderate affinity by PGE2, PGE1, PGF2alpha and 6-isopropoxy-9-xanthone-2-carboxylic acid (AH6809) but not PGD2, LTB4 or 5-HETE. By RT-PCR, EP2 receptor PCR products were detected in extracts derived from lung cancer cells. PGE2 caused cAMP elevation in a concentration-dependent manner using NCI-H1299 cells and the increase in cAMP caused by PGE2 was antagonized by AH6809. PGE2 had no effect on cytosolic Ca2+ but PGE2 caused increased c-fos mRNA in NCI-H1299 cells. AH6809 inhibited the proliferation of NCI-H1299 cells using MTT and clonogenic assays. These results indicate that functional PG receptors are present on NSCLC cells which are antagonized by AH6809.

Cyclooxygenase-2 and adenylate cyclase/protein kinase A signaling pathway enhances angiogenesis through induction of vascular endothelial growth factor in rat sponge implants

Angiogenesis is reportedly enhanced by prostaglandins (PGs). In the present experiment, we tested whether or not COX-2 and adenylate cyclase/protein kinase A (AC/PKA)-dependent VEGF induction enhanced angiogenesis in this model. Angiogenesis was enhanced by topical injection of human recombinant basic fibroblast growth factor (bFGF). The enhanced angiogenesis by bFGF was inhibited by indomethacin or selective COX-2 inhibitors, NS398, nimesulide, and JTE-522. Topical daily injections of 8-bromo-cAMP enhanced angiogenesis in a dose-dependent manner. Forskolin, an activator of AC, also facilitated angiogenesis in a dose-dependent manner, as did amrinone, an inhibitor of phosphodiesterase. VEGF induction was confirmed by the increased levels in the fluids in the sponge matrix after topical injection of 8-bromo-cAMP. Immunohistochemical investigation further revealed the VEGF-expressed cells in the sponge granulation tissues to be fibroblasts, and the intensity of positive reactions was enhanced by bFGF, 8-bromo-cAMP, forskolin, and amrinone. Angiogenesis was inhibited by indometacin or selective COX-2 inhibitors, NS-398, nimesulide, and JTE-522. In addition, angiogenesis without topical injections of the above compounds was also suppressed by SQ22,536, an inhibitor for AC. or H-89, an inhibitor for PKA, with concomitant reductions in VEGF levels. Daily topical injections of neutralizing antibody or anti-sense oligonucleotide against VEGF significantly suppressed angiogenesis. These results suggested that COX-2 and AC/PKA-dependent induction of VEGF certainly enhanced angiogenesis, and that pharmacological tools for controlling this signaling pathway may be able to facilitate the management of conditions involving angiogenesis.

Adenylate cyclase/protein kinase A signaling pathway enhances angiogenesis through induction of vascular endothelial growth factor in vivo

We previously reported that endogenous prostaglandins (PGs) may increase cAMP facilitated angiogenesis through the induction of vascular endothelial growth factor (VEGF) in rat sponge implantation models. In the present experiment, we tested whether or not adenylate cyclase / protein kinase A (AC/PKA)-dependent VEGF induction enhanced angiogenesis in this model. Topical daily injections of 8-bromo-cAMP enhanced angiogenesis in a dose-dependent manner. Forskolin, an activator of AC, also facilitated angiogenesis as did amrinone, an inhibitor of phosphodiesterase. VEGF induction was confirmed by the increased levels in the fluids in the sponge matrix after topical injection of 8-bromo-cAMP. Immunohistochemical investigation further revealed the VEGF-expressed cells in the sponge granulation tissues to be fibroblasts, and the intensity of positive reactions was enhanced by 8-bromo-cAMP, forskolin and amrinone. Angiogenesis without topical injections of the above compounds was suppressed by SQ22,536, an inhibitor for AC, or H-89, an inhibitor for PKA, with concomitant reductions in VEGF levels. Daily topical injections of neutralizing antibody or anti-sense oligonucleotide against VEGF significantly suppressed angiogenesis. PGE2-induced angiogenesis was suppressed with SQ22,536 or H-89. These results suggested that AC/PKA-dependent induction of VEGF certainly enhanced angiogenesis and that pharmacological tools for controlling this signaling pathway may be able to facilitate the management of conditions involving angiogenesis.

PGE(2) stimulates VEGF expression in endothelial cells via ERK2/JNK1 signaling pathways

Vascular endothelial growth factor (VEGF) plays an essential role in the initiation and regulation of angiogenesis-a crucial component of wound healing and cancer growth. Prostaglandins (PGs) stimulate angiogenesis but the precise mechanisms of their pro-angiogenic actions remain unexplained. We investigated whether prostaglandin E(2) (PGE(2)) can induce VEGF expression in rat gastric microvascular endothelial cells (RGMEC) and the signaling pathway(s) involved. We demonstrated that PGE(2) significantly increased ERK2 and JNK1 activation and VEGF mRNA and protein expression. Incubation of RGMEC with PD 98059 (MEK kinase inhibitor) significantly reduced PGE(2)-induced ERK2 activity, VEGF mRNA and protein expression. Furthermore, PD 98059 treatment almost completely abolished JNK1 activation. Our data suggest that PGE(2)-stimulates VEGF expression in RGMEC via transactivation of JNK1 by ERK2. One potential implication of this finding is that increased PG levels in cancers could facilitate tumor growth by stimulating VEGF synthesis and angiogenesis.