Novel neuroendocrine role of γ-aminobutyric acid and gastrin-releasing peptide in the host response to influenza infection

Gastrin-releasing peptide (GRP), an evolutionarily conserved neuropeptide, significantly contributes to influenza-induced lethality and inflammation in rodent models. Because GRP is produced by pulmonary neuroendocrine cells (PNECs) in response to γ-aminobutyric acid (GABA), we hypothesized that influenza infection promotes GABA release from PNECs that activate GABAB receptors on PNECs to secrete GRP. Oxidative stress was increased in the lungs of influenza A/PR/8/34 (PR8)-infected mice, as well as serum glutamate decarboxylase 1, the enzyme that converts L-glutamic acid into GABA. The therapeutic administration of saclofen, a GABAB receptor antagonist, protected PR8-infected mice, reduced lung proinflammatory gene expression of C-C chemokine receptor type 2 (Ccr2), cluster of differentiation 68 (Cd68), and Toll like receptor 4 (Tlr4) and decreased the levels of GRP and high-mobility group box 1 (HMGB1) in sera. Conversely, baclofen, a GABAB receptor agonist, significantly increased the lethality and inflammatory responses. The GRP antagonist, NSC77427, as well as the GABAB antagonist, saclofen, blunted the PR8-induced monocyte infiltration into the lung. Together, these data provide the first report of neuroregulatory control of influenza-induced disease.

Cancer cell survival depends on collagen uptake into tumor-associated stroma

Collagen I, the most abundant protein in humans, is ubiquitous in solid tumors where it provides a rich source of exploitable metabolic fuel for cancer cells. While tumor cells were unable to exploit collagen directly, here we show they can usurp metabolic byproducts of collagen-consuming tumor-associated stroma. Using genetically engineered mouse models, we discovered that solid tumor growth depends upon collagen binding and uptake mediated by the TEM8/ANTXR1 cell surface protein in tumor-associated stroma. Tumor-associated stromal cells processed collagen into glutamine, which was then released and internalized by cancer cells. Under chronic nutrient starvation, a condition driven by the high metabolic demand of tumors, cancer cells exploited glutamine to survive, an effect that could be reversed by blocking collagen uptake with TEM8 neutralizing antibodies. These studies reveal that cancer cells exploit collagen-consuming stromal cells for survival, exposing an important vulnerability across solid tumors with implications for developing improved anticancer therapy.

Immediate Release of Gastrin-Releasing Peptide Mediates Delayed Radiation-Induced Pulmonary Fibrosis

Radiation-induced pulmonary fibrosis (RTPF) is a progressive, serious condition in many subjects treated for thoracic malignancies or after accidental nuclear exposure. No biomarker exists for identifying the irradiated subjects most susceptible to pulmonary fibrosis (PF). Previously, we determined that gastrin-releasing peptide (GRP) was elevated within days after birth in newborns exposed to hyperoxia who later developed chronic lung disease. The goal of the current study was to test whether radiation (RT) exposure triggers GRP release in mice and whether this contributes to RTPF in vivo. We determined urine GRP levels and lung GRP immunostaining in mice 0 to 24 after post-thoracic RT (15 Gy). Urine GRP levels were significantly elevated between 24 hours post-RT; GRP-blocking monoclonal antibody 2A11, given minutes post-RT, abrogated urine GRP levels by 6 to 12 hours and also altered phosphoprotein signaling pathways at 24 hours post-RT. Strong extracellular GRP immunostaining was observed in lung at 6 hours post-RT. Mice given one dose of GRP monoclonal antibody 2A11 24 hours post-RT had significantly reduced myofibroblast accumulation and collagen deposition 15 weeks later, indicating protection against lung fibrosis. Therefore, elevation of urine GRP could be predictive of RTPF development. In addition, transient GRP blockade could mitigate PF in normal lung after therapeutic or accidental RT exposure.

Sulforaphane Suppresses the Growth of Triple-negative Breast Cancer Stem-like Cells In vitro and In vivo

Triple-negative breast cancer (TNBC) represents the poorest prognosis among all of breast cancer subtypes with no currently available effective therapy. In this study, we hypothesized that sulforaphane, a dietary component abundant in broccoli and its sprouts, can inhibit malignant cell proliferation and tumor sphere formation of cancer stem-like cells (CSC) in TNBC. CSC population was isolated using FACS analysis with the combined stem cell surface markers, CD44⁺/CD24^-/CD49f⁺ The effect of sulforaphane on a stem-related embryonic oncogene CRIPTO-1/TDGF1 (CR1) was evaluated via ELISA. In vivo, BalbC/nude mice were supplemented with sulforaphane before and after TNBC cell inoculation (daily intraperitoneal injection of 50 mg sulforaphane/kg for 5 and 3 weeks, respectively), and the effects of sulforaphane during mammary tumor initiation and growth were accessed with NanoString gene analysis. We found that sulforaphane can inhibit cell proliferation and mammosphere formation of CSCs in TNBC. Further analysis of gene expression in these TNBC tumor cells revealed that sulforaphane significantly decreases the expression of cancer-specific CR1, CRIPTO-3/TDGF1P3 (CR3, a homologue of CR1), and various stem cell markers including Nanog, aldehyde dehydrogenase 1A1 (ALDH1A1), Wnt3, and Notch4. Our results suggest that sulforaphane may control the malignant proliferation of CSCs in TNBC via Cripto-mediated pathway by either suppressing its expression and/or by inhibiting Cripto/Alk4 protein complex formation. Thus, the use of sulforaphane for chemoprevention of TNBC is plausible and warrants further clinical evaluation.

Novel role of gastrin releasing peptide-mediated signaling in the host response to influenza infection

Gastrin-releasing peptide (GRP) is an evolutionarily well-conserved neuropeptide that was originally recognized for its ability to mediate gastric acid secretion in the gut. More recently, however, GRP has been implicated in pulmonary lung inflammatory diseases including bronchopulmonary dysplasia, chronic obstructive pulmonary disease, emphysema, and others. Antagonizing GRP or its receptor mitigated lethality associated with the onset of viral pneumonia in a well-characterized mouse model of influenza. In mice treated therapeutically with the small-molecule GRP inhibitor, NSC77427, increased survival was accompanied by decreased numbers of GRP-producing pulmonary neuroendocrine cells, improved lung histopathology, and suppressed cytokine gene expression. In addition, in vitro studies in macrophages indicate that GRP synergizes with the prototype TLR4 agonist, lipopolysaccharide, to induce cytokine gene expression. Thus, these findings reveal that GRP is a previously unidentified mediator of influenza-induced inflammatory disease that is a potentially novel target for therapeutic intervention.

Augmented Responses to Ozone in Obese Mice Require IL-17A and Gastrin-Releasing Peptide

Ozone and obesity both increase IL-17A in the lungs. In mice, obesity augments the airway hyperresponsiveness and neutrophil recruitment induced by acute ozone exposure. Therefore, we examined the role of IL-17A in obesity-related increases in the response to ozone observed in obese mice. Lean wild-type and obese db/db mice were pretreated with IL-17A-blocking or isotype antibodies, exposed to air or ozone (2 ppm for 3 h), and evaluated 24 hours later. Microarray analysis of lung tissue gene expression was used to examine the mechanistic basis for effects of anti-IL-17A. Compared with lean mice, ozone-exposed obese mice had greater concentrations of BAL IL-17A and greater numbers of pulmonary IL-17A⁺ cells. Ozone-induced increases in BAL IL-23 and CCL20, cytokines important for IL-17A⁺ cell recruitment and activation, were also greater in obese mice. Anti-IL-17A treatment reduced ozone-induced airway hyperresponsiveness toward levels observed in lean mice. Anti-IL-17A treatment also reduced BAL neutrophils in both lean and obese mice, possibly because of reductions in CXCL1. Microarray analysis identified gastrin-releasing peptide (GRP) receptor (Grpr) among those genes that were both elevated in the lungs of obese mice after ozone exposure and reduced after anti-IL-17A treatment. Furthermore, ozone exposure increased BAL GRP to a greater extent in obese than in lean mice, and GRP-neutralizing antibody treatment reduced obesity-related increases in ozone-induced airway hyperresponsiveness and neutrophil recruitment. Our data indicate that IL-17A contributes to augmented responses to ozone in db/db mice. Furthermore, IL-17A appears to act at least in part by inducing expression of Grpr.

Identification of Adrenomedullin in Avian Type II Pneumocytes: Increased Expression after Exposure to Air Pollutants

Adrenomedullin (AM) is a potent vasodilator peptide present in the lung of mammals where it is expressed mainly in the columnar epithelium and alveolar macrophages. AM increases the secretion of phosphatidylcholine by type II pneumocytes, which suggests a role as an autocrine modulator of surfactant secretion. In this study we show the expression of an AM-like protein in the lung of the pigeon, Columba livia. Using an antibody against its human ortholog, AM-like immunoreactivity was found to be associated with membranous structures of the multivesicular bodies of type II pneumocytes. We also studied the differential expression of AM-like peptide in the lung of pigeons exposed to polluted city air vs cleaner countryside conditions and found that AM-like expression was higher in city animals. Similar results were obtained in an experimental study in which pigeons were exposed to increasing concentrations of a single pollutant, ozone. Taken together, our findings support the implication of AM in the response of type II pneumocytes to air pollutants.

Developmental signaling pathways regulating mammary stem cells and contributing to the etiology of triple-negative breast cancer

Cancer has been considered as temporal and spatial aberrations of normal development in tissues. Similarities between mammary embryonic development and cell transformation suggest that the underlying processes required for mammary gland development are also those perturbed during various stages of mammary tumorigenesis and breast cancer (BC) development. The master regulators of embryonic development Cripto-1, Notch/CSL, and Wnt/β-catenin play key roles in modulating mammary gland morphogenesis and cell fate specification in the embryo through fetal mammary stem cells (fMaSC) and in the adult organism particularly within the adult mammary stem cells (aMaSC), which determine mammary progenitor cell lineages that generate the basal/myoepithelial and luminal compartments of the adult mammary gland. Together with recognized transcription factors and embryonic stem cell markers, these embryonic regulatory molecules can be inappropriately augmented during tumorigenesis to support the tumor-initiating cell (TIC)/cancer stem cell (CSC) compartment, and the effects of their deregulation may contribute for the etiology of BC, in particular the most aggressive subtype of BC, triple-negative breast cancer (TNBC). This in depth review will present evidence of the involvement of Cripto-1, Notch/CSL, and Wnt/β-catenin in the normal mammary gland morphogenesis and tumorigenesis, from fMaSC/aMaSC regulation to TIC generation and maintenance in TNBC. Specific therapies for treating TNBC by targeting these embryonic pathways in TICs will be further discussed, providing new opportunities to destroy not only the bulk tumor, but also TICs that initiate and promote the metastatic spread and recurrence of this aggressive subtype of BC.

Cripto-1: an extracellular protein - connecting the sequestered biological dots

Cripto-1 (CR-1) is a multifunctional embryonic protein that is re-expressed during inflammation, wound repair, and malignant transformation. CR-1 can function either as a tethered co-receptor or shed as a free ligand underpinning its flexible role in cell physiology. CR-1 has been shown to mediate cell growth, migration, invasion, and induce epithelial to mesenchymal transition (EMT). The main signaling pathways mediating CR-1 effects include Nodal-dependent (Smad2/3) and Nodal-independent (Src/p44/42/Akt) signaling transduction pathways. In addition, there are several naturally occurring binding partner proteins (BPPs) for CR-1 that can either agonize or antagonize its bioactivity. We will review the collective role of CR-1 as an extracellular protein, discuss caveats to consider in developing a quantitation assay, define possible mechanistic avenues applicable for drug discovery, and report on our experimental approaches to overcome these problematic issues.

Salvage treatment with ganciclovir in a splenectomized, polytransfused patient affected by systemic inflammatory response syndrome

A 23-year-old man was admitted to hospital with a 12-day history of daily fever. A clinical history revealed that 10 months previously, the patient had been splenectomized and polytransfused for a severe blunt trauma. On admission, laboratory data revealed significant leukocytosis (33,230/ul). The patient's general clinical conditions rapidly worsened into a severe systemic inflammatory response syndrome in four days. After 10 days of broad-spectrum antibiotic treatment, the temperature curve was unmodified and severe leukocytosis persisted (44,300 ul) with absolute lymphocytosis. Laboratory tests ruled out hematological diseases, pneumonia, abscesses and endocarditis. In the light of IgM positivity for CMV (unconfirmed by PCR) and with the support of a PubMed search, we commenced a salvage treatment with intravenous ganciclovir, suspecting a viral infection or reactivation. After two days of therapy, an immediate defervescence was observed with a remarkable clinical improvement. After 10 days, the clinical syndrome had been completely resolved and the patient was discharged in good, general clinical health.

Obesity and iron deficiency anemia as risk factors for asymptomatic bacteriuria

BACKGROUND

Few studies examined the risk factors of asymptomatic bacteriuria, showing contradictory results. Our study aimed to examine the association between different clinical and laboratory parameters and asymptomatic bacteriuria in internal medicine patients.

MATERIALS AND METHODS

330 consecutive hospitalized subjects, asymptomatic for urinary tract infections (UTIs), underwent to microscopic examination of urine specimens. 100 subjects were positive for microscopic bacteriuria and were recruited into the study. At the quantitative urine culture 31 subjects of study population were positive while 69 subjects were negative for bacteriuria.

RESULTS

The analysis of clinical characteristics showed that the two groups of subjects (positive and negative urine culture for bacteriuria) were significant different (p<0.05) about obesity (76.7% vs 42% respectively), metabolic syndrome (80.6% vs 44,9%), cholelithiasis (35.5% vs 13,2%) and iron deficiency anemia (80.6% vs 53,6%). The univariate analysis showed that only obesity, cholelithiasis and iron deficiency anemia were positively associated with positive urine culture for bacteriuria (Odds Ratios [OR]=3.79, p=0.0003; OR=2,65, p=0.0091; OR=2.63, p=0.0097; respectively). However, the multivariate analysis by logistic regression showed that only obesity and iron deficiency anemia, independently associated with positive urine culture for bacteriuria (OR=3.9695, p=0.0075; OR=3.1569, p=0.03420 respectively).

CONCLUSIONS

This study shows that obesity and iron deficiency anemia are independent risk factors for asymptomatic bacteriuria.

Novel Phenotypic Fluorescent Three-Dimensional Co-Culture Platforms for Recapitulating Tumor in vivo Progression and for Personalized Therapy

Because three-dimensional (3D) in vitro models are more accurate than 2D cell culture models and faster and cheaper than animal models, they have become a prospective trend in the biomedical and pharmaceutical fields, especially for personalized and targeted therapies. Because appropriate 3D models can be customized to mimic the in vivo microenvironment wherein various cell populations grow within an intricate but well organized extracellular matrix (ECM), they can accurately recapitulate physiological and pathophysiological progressions. The majority of cancers are carcinomas, which originate from epithelial cells, and dynamically interact with non-malignant cells including stromal cells (fibroblasts), vascular cells (endothelial cells and pericytes), immune cells (macrophages and mast cells), and the ECM. Employing a tumor monoclonal colony, tumor xenograft or patient cancer biopsy into an in vivo-like microenvironment, the native signaling pathways, cell-cell and cell-matrix interactions, and cell phenotypes are preserved and our fluorescent phenotypic 3D co-culture platforms can then accurately recapitulate the tumor in vivo scenario including tumor induced angiogenesis, tumor growth, and metastasis.

In this paper, we describe a robust and standardized method to co-culture a tumor colony or biopsy with different cell populations, e.g., endothelial cells, immune cells, pericytes, etc. The procedures for recovering cells from the co-culture for molecular analyses, imaging, and analyzing are also described. We selected ECM solubilized extract derived from Engelbreth-Holm-Swam sarcoma cells. Because the 3D co-culture platforms can provide drug chemosensitivity data within 9 days that is equivalent to the results generated from mouse tumor xenograft models in 50 days, the 3D co-culture platforms are more accurate, efficient, and cost-effective and may replace animal models in the near future to predict drug efficacy, personalize therapies, prevent drug resistance, and improve the quality of life.

Novel Phenotypic Fluorescent Three-Dimensional Platforms for High-throughput Drug Screening and Personalized Chemotherapy

We have developed novel phenotypic fluorescent three-dimensional co-culture platforms that efficiently and economically screen anti-angiogenic/anti-metastatic drugs on a high-throughput scale. Individual cell populations can be identified and isolated for protein/gene expression profiling studies and cellular movement/interactions can be tracked by time-lapse cinematography. More importantly, these platforms closely parallel the in vivo angiogenic and metastatic outcomes of a given tumor xenograft in the nude mouse model but, unlike in vivo models, our co-culture platforms produce comparable results in five to nine days. Potentially, by incorporating cancer patient biopsies, the co-culture platforms should greatly improve the effectiveness and efficiency of personalized chemotherapy.

SCNH2 is a novel apelinergic family member acting as a potent mitogenic and chemotactic factor for both endothelial and epithelial cells

The gut hormone apelin is a major therapeutic focus for several diseases involving inflammation and aberrant cell growth. We investigated whether apelin-36 contained alternative bioactive peptides associated with normal physiology or disease. Amino acid sequence analysis of apelin-36 identified an amidation motif consistent with the formation of a secondary bioactive peptide (SCNH2). SCNH2 is proven to be mitogenic and chemotactic in normal/malignant cells and augments angiogenesis via a PTX-resistant/CT-X-sensitive G protein-coupled receptor (GPCR). Notably, SCNH2 is substantially more potent and sensitive than apelin-13 and vascular endothelial growth factor-A. Endogenous SCNH2 is highly expressed in human tumors and placenta and in mouse embryonic tissues. Our findings demonstrate that SCNH2 is a new apelinergic member with critical pluripotent roles in angiogenesis related diseases and embryogenesis via a non-APJ GPCR.

Aryl hydrocarbon receptor-induced adrenomedullin mediates cigarette smoke carcinogenicity in humans and mice

Cigarette smoking (CS) is a leading cause of death worldwide. The aryl hydrocarbon receptor (AHR) is partially responsible for tobacco-induced carcinogenesis although the underlying mechanisms involving early effector genes have yet to be determined. Here, we report that adrenomedullin (ADM) significantly contributes to the carcinogenicity of tobacco-activated AHR. CS and AHR activating ligands induced ADM in vitro and in vivo but not in AHR-deficient fibroblasts and mice. Ectopic transfection of AHR rescued ADM expression in AHR(-/-) fibroblasts whereas AHR blockage with siRNA in wild type cells significantly decreased ADM expression. AHR regulates ADM expression through two intronic xenobiotic response elements located close to the start codon in the ADM gene. Using tissue microarrays we showed that ADM and AHR were coupregulated in lung tumor biopsies from smoker patients. Microarray meta-analysis of 304 independent microarray experiments showed that ADM is elevated in smokers and smokers with cancer. In addition, ADM coassociated with a subset of AHR responsive genes and efficiently differentiated patients with lung cancer from nonsmokers. In a novel preclinical model of CS-induced tumor progression, host exposure to CS extracts significantly elevated tumor ADM although systemic treatment with the ADM antagonist NSC16311 efficiently blocked tobacco-induced tumor growth. In conclusion, ADM significantly contributes the carcinogenic effect of AHR and tobacco combustion products. We suggest that therapeutics targeting the AHR/ADM axis may be of clinical relevance in the treatment of tobacco-induced pulmonary malignancies.

Abstract A161: 3-Deazaneplanocin A (DZNep) inhibits repression of tumor suppressor genes and abrogates tumorigenicity of lung cancer cells mediated by cigarette smoke

Polycomb repressor complex-2 (PRC-2) - a critical mediator of stem cell pluripotency, is aberrantly expressed in a variety of human malignancies including lung cancers. PRC-2 contains three core proteins, enhancer of zeste 2 (EZH2), suppressor of zeste 12 (SUZ12), and embryonic ectoderm development (EED). The SET (suppressor of variegation-enhancer of zeste-trithorax) domain of EZH2 induces trimethylation of lysine 27 on histone H3 (H3K27Me3), a repressive histone mark observed in bivalent chromatin, as well as gene promoters normally inactivated during differentiation, or aberrantly silenced during malignant transformation. Previously we demonstrated that following in-vitro exposure to cigarette smoke condensate (CSC), lung cancer cells exhibit significantly increased tumorigenicity in nude mice. This phenomenon coincided with PRC-2 mediated repression of Dkk-1, encoding an antagonist of Wnt signaling implicated in maintenance of cancer stem cells. Knockdown of Dkk-1 recapitulated the pro-tumorigenic effects of cigarette smoke in lung cancer cells. The present study was undertaken to examine the effects of the S-adenosylhomocysteine hydrolase inhibitor, DZNep in lung cancer cells. Immunoblot analysis revealed that DZNep mediated dose-dependent depletion of EZH2, EED and SUZ12, with concomitant decreases in global H3K27Me3 levels in cultured human lung cancer cells. Microarray and qRT-PCR experiments revealed that DZNep induced Dkk-1 expression in A549, H841, and H322 lung cancer cells, a phenomenon coinciding with growth inhibition and apoptosis in these cells. Promoter reporter assays, ELISA and immunoblot experiments confirmed that DZNep significantly increased Dkk-1 promoter activity, and enhanced Dkk-1 protein expression/secretion in a dose-dependent manner in these cells. Chromatin immunoprecipitation (ChIP) experiments demonstrated that DZNep-mediated activation of Dkk-1 coincided with decreased levels of H3K27Me3 within the Dkk-1 promoter. qRT-PCR, ELISA and immunoblot experiments revealed that exposure of lung cancer cells to DZNep either before or concurrent with CSC, significantly abrogated tobacco-mediated repression of Dkk-1 in vitro. Additional experiments utilizing a novel in-vivo model system revealed that daily intra-peritoneal (IP) injections of CSC for 21 days significantly decreased Dkk-1 gene expression in subcutaneous A549 xenografts, and enhanced growth of these tumors in nude mice. Simultaneous IP administration of DZNep (2.5 mg/kg BID q4 days every 7 days) significantly attenuated CSC-mediated repression of Dkk-1, and abrogated growth of tumor xenografts induced by CSC. Collectively, these findings suggest that DZNep inhibits polycomb-mediated repression of tumor suppressor genes in lung cancer cells exposed to cigarette smoke in-vitro and in-vivo, and support evaluation of DZNep for epigenetic treatment and prevention of tobacco-induced lung cancers.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A161.

Chemotherapy-induced cardiotoxicity: role of the conventional echocardiography and the tissue Doppler

AIM

The cardiotoxicity of anticancer drugs is an emerging problem and only an identification of the early signs of cardiotoxicity by conventional echocardiography and not (tissue Doppler imaging, TDI), will limit and contain the long-term cardiotoxicity effects. The aim of this study was to identify, through conventional echocardiography and TDI, parameters to use as early "signs" of cardiotoxicity.

METHODS

A prospective study was performed using patients with breast cancer (72 women, median age 57 ± 12) treated with anticancer drugs (adjuvant chemotherapy). All patients underwent a careful cardiological evaluation before starting treatment (T0) and during follow-up at 3 months (T1), 6 months (T2) and 1 year (T3). Electrocardiography and echocardiography were performed in all patients in these times. Echocardiography evaluation considered the following parameters: systolic and diastolic diameters and volumes, LVEF, MAPSE, TAPSE, E/A TDI (Em, Am, Sm, IVCT, IVRT, ET, TEI index). On the basis of chemotherapy treatment, patients were divided into 5 groups: A=FEC (fluorouracil, epirubicin, cyclophosphamide), B=FEC+trastuzumab, C=trastuzumab, D=FEC+taxotere, E=FEC+taxolo+trastuzumab.

RESULTS

A significant reduction in the echo parameters of TDI was observed. TDI appears to offer important advantages over traditional techniques in revealing the presence of early signs of cardiotoxicity.

CONCLUSION

The TDI should be utilized to complement conventional echocardiography in the assessment of cardiotoxicity.

Non-peptide small molecule regulators of lymphangiogenesis

Adrenomedullin (AM) and gastrin releasing peptide (GRP) are neuroendocrine peptides that have been previously implicated as regulators of angiogenesis and lymphangiogenesis. Using an immortalized human dermal microvascular lymphatic endothelial cell line stably transfected with red fluorescent protein (LEC/RFP), we demonstrate the ability of AM and GRP to augment tube formation complexity of this target cell in a dose-dependent manner. Maximum tube density was initiated at 1 nM for both peptides, and as concentrations exceeded 10 nM a decrease in tube formation was noted, hence following a classic rise/fall biological response curve. In addition, we show that appropriate small molecule mimetics to neutralizing monoclonal antibodies of AM or GRP, at 1 microM concentration, can function to either inhibit (antagonist) or enhance (super agonist) peptide-induced tube formation of LEC/RFP. Our small molecule reagents by themselves have no activity, but in the presence of their respective peptides can mediate a positive or negative response, hence the super agonist designation. These compounds represent new regulatory drugs of the lymphatic system with possible patient application in the clinical management of edema and metastatic disease.

Serum inter-alpha-trypsin inhibitor and matrix hyaluronan promote angiogenesis in fibrotic lung injury

RATIONALE

The etiology and pathogenesis of angiogenesis in idiopathic pulmonary fibrosis (IPF) is poorly understood. Inter-alpha-trypsin inhibitor (IaI) is a serum protein that can bind to hyaluronan (HA) and may contribute to the angiogenic response to tissue injury.

OBJECTIVES

To determine whether IaI promotes HA-mediated angiogenesis in tissue injury.

METHODS

An examination was undertaken of angiogenesis in IaI-sufficient and -deficient mice in the bleomycin model of pulmonary fibrosis and in angiogenesis assays in vivo and in vitro. IaI and HA in patients with IPF were examined.

MEASUREMENTS AND MAIN RESULTS

IaI significantly enhances the angiogenic response to short-fragment HA in vivo and in vitro. lal deficiency Ieads to decreased angiogenesis in the matrigel model, and decreases lung angiogenesis after bleomycin exposure in mice. IaI is found in fibroblastic foci in IPF, where it colocalizes with HA. The colocalization is particularly strong in vascular areas around fibroblastic foci. Serum levels of IaI and HA are significantly elevated in patients with IPF compared with control subjects. High serum IaI and HA levels are associated with decreased lung diffusing capacity, but not FVC.

CONCLUSIONS

Our findings indicate that serum IaI interacts with HA, and promotes angiogenesis in lung injury. IaI appears to contribute to the vascular response to lung injury and may lead to aberrant angiogenesis. Clinical trial registered with www.clinicaltrials.gov (NCT00016627).

Functional characterization of filamin a interacting protein 1-like, a novel candidate for antivascular cancer therapy

Inhibiting angiogenesis has become a major therapeutic strategy for cancer treatment. To identify common intracellular mediators, we previously analyzed gene expression profiles of endothelial cells after treatment with angiogenesis inhibitors. Filamin A interacting protein 1-like (FILIP1L; previously known as down-regulated in ovarian cancer 1) was identified as one of the genes up-regulated in endothelial cells in response to these inhibitors. However, the expression and function of FILIP1L protein is uncharacterized. Here, we provide the first description of the expression and specific subcellular localization of FILIP1L protein in human tissue. Overexpression of FILIP1L resulted in inhibition of cell proliferation and migration and increased apoptosis. In addition, overexpression of FILIP1L truncation mutants showed differential antiproliferative activity. A COOH terminal truncation mutant (FILIP1LDeltaC103) was more potent than wild-type FILIP1L in mediating this activity. Targeted expression of FILIP1LDeltaC103 in tumor vasculature inhibited tumor growth in vivo. Overall, these findings suggest that the novel protein FILIP1L may be an important mediator of the effects of angiogenesis inhibitors and that FILIP1L has the potential to be an antivascular reagent for cancer therapy.

Intracellular proadrenomedullin-derived peptides decorate the microtubules and contribute to cytoskeleton function

Adrenomedullin (AM) and proadrenomedullin N-terminal 20 peptide (PAMP) are secretory hormones, but it is not unusual to find them in intracellular compartments. Using yeast-2 hybrid technology, we found interactions between AM and several microtubule-associated proteins (MAPs), and between PAMP and tubulin. Expression of fluorescent-tagged AM and PAMP as well as immunofluorescence for the native peptides showed a complete decoration of the microtubules and colocalization with other MAPs. PAMP, but not AM, bound to tubulin in vitro and destabilized tubulin polymerization. Down-regulation of the gene coding for both AM and PAMP through small interfering RNA technology resulted in morphological changes, microtubule stabilization, increase in posttranslational modifications of tubulin such as acetylation and detyrosination, reduction in cell motility, and partial arrest at the G2 phase of the cell cycle, when compared with cells transfected with the same vector carrying a scrambled sequence. These results show that PAMP is a novel MAP, whereas AM may be exerting more subtle effects in regulating cytoskeleton function.

Differentially expressed nucleolar transforming growth factor-beta1 target (DENTT) exhibits an inhibitory role on tumorigenesis

Differentially expressed nucleolar transforming growth factor-beta1 target (DENTT), also known as testis-specific protein Y-encoded-like (TSPYL-2) and cell division autoantigen-1, is a member of the testis-specific protein Y-encoded (TSPY)/TSPY-L/SET/nucleosome assembly protein-1 superfamily. DENTT is expressed in various tissues including normal human lung. Here, we investigate the involvement of DENTT in cancer promotion and progression. DENTT messenger RNA (mRNA) and protein levels were shown to be markedly downregulated in human and mouse primary tumors and in human tumor cell lines. Overexpression of DENTT in human lung (A549-DENTT) and breast (MCF-7-DENTT) cancer cells resulted in diminished growth potential in anchorage-dependent growth assays and reduced capacity to form colonies under anchorage-independent culture conditions. The migratory potential of A549-DENTT and MCF-7-DENTT cells was reduced when compared with empty vector control cells. Treating human lung cell lines with demethylating agents increased DENTT expression significantly. DENTT expression pattern paralleled that of transforming growth factor-beta1 (TGF-beta1) in normal and malignant tissue and ectopic expression or treatment with TGF-beta1 in lung cancer cells was followed by increased DENTT mRNA and protein levels. Collectively, our results suggest a role for DENTT as a suppressor of the tumorigenic phenotype.

The aryl hydrocarbon receptor repressor is a putative tumor suppressor gene in multiple human cancers

The aryl hydrocarbon receptor repressor (AHRR) is a bHLH/Per-ARNT-Sim transcription factor located in a region of chromosome 5 (5p15.3) that has been proposed to contain one or more tumor suppressor genes. We report here consistent downregulation of AHRR mRNA in human malignant tissue from different anatomical origins, including colon, breast, lung, stomach, cervix, and ovary, and demonstrate DNA hypermethylation as the regulatory mechanism of AHRR gene silencing. Knockdown of AHRR gene expression in a human lung cancer cell line using siRNA significantly enhanced in vitro anchorage-dependent and -independent cell growth as well as cell growth after transplantation into immunocompromised mice. In addition, knockdown of AHRR in non-clonable normal human mammary epithelial cells enabled them to grow in an anchorage-independent manner. Further, downregulation of AHRR expression in the human lung cancer cell line conferred resistance to apoptotic signals and enhanced motility and invasion in vitro and angiogenic potential in vivo. Ectopic expression of AHRR in tumor cells resulted in diminished anchorage-dependent and -independent cell growth and reduced angiogenic potential. These results therefore demonstrate that AHRR is a putative new tumor suppressor gene in multiple types of human cancers.

Bombesin-like peptides modulate alveolarization and angiogenesis in bronchopulmonary dysplasia

RATIONALE

The incidence of bronchopulmonary dysplasia (BPD), a chronic lung disease of newborns, is paradoxically rising despite medical advances. We demonstrated elevated bombesin-like peptide levels in infants that later developed BPD. In the 140-day hyperoxic baboon model of BPD, anti-bombesin antibody 2A11 abrogated lung injury.

OBJECTIVES

To test the hypothesis that bombesin-like peptides mediate BPD in extremely premature baboons (born at Gestational Day 125 and given oxygen pro re nata [PRN], called the 125-day PRN model), similar to "modern-day BPD."

METHODS

The 125-day animals were treated with 2A11 on Postnatal Day 1 (P1), P3, and P6. On P14 and P21, lungs were inflation-fixed for histopathologic analyses of alveolarization. Regulation of angiogenesis by bombesin was evaluated using cultured pulmonary microvascular endothelial cells.

MEASUREMENTS AND MAIN RESULTS

In 125-day PRN animals, urine bombesin-like peptide levels at P2-3 are directly correlated with impaired lung function at P14. Gastrin-releasing peptide (the major pulmonary bombesin-like peptide) mRNA was elevated eightfold at P1 and remained high thereafter. At P14, 2A11 reduced alveolar wall thickness and increased the percentage of secondary septa containing endothelial cells. At P21, 2A11-treated 125-day PRN animals had improved alveolarization according to mean linear intercepts and number of branch points per millimeter squared. Bombesin promoted tubulogenesis of cultured pulmonary microvascular endothelial cells, but cocultured fetal lung mesenchymal cells abrogated this effect.

CONCLUSIONS

Early bombesin-like peptide overproduction in 125-day PRN animals predicted alveolarization defects weeks later. Bombesin-like peptide blockade improved septation, with the greatest effects at P21. This could have implications for preventing BPD in premature infants.

IFN Regulatory Factor-2 Regulates Macrophage Apoptosis through a STAT1/3- and Caspase-1-Dependent Mechanism

IFN regulatory factor (IRF)-2(-/-) mice are significantly more resistant to LPS challenge than wild-type littermates, and this was correlated with increased numbers of apoptotic Kupffer cells. To assess the generality of this observation, and to understand the role of IRF-2 in apoptosis, responses of peritoneal macrophages from IRF-2(+/+) and IRF-2(-/-) mice to apoptotic stimuli, including the fungal metabolite, gliotoxin, were compared. IRF-2(-/-) macrophages exhibited a consistently higher incidence of apoptosis that failed to correlate with caspase-3/7 activity. Using microarray gene expression profiling of liver RNA samples derived from IRF-2(+/+) and IRF-2(-/-) mice treated with saline or LPS, we identified >40 genes that were significantly down-regulated in IRF-2(-/-) mice, including Stat3, which has been reported to regulate apoptosis. Compared with IRF-2(+/+) macrophages, STAT3alpha mRNA was up-regulated constitutively or after gliotoxin treatment of IRF-2(-/-) macrophages, whereas STAT3beta mRNA was down-regulated. Phospho-Y705-STAT3, phospho-S727-STAT1, and phospho-p38 protein levels were also significantly higher in IRF-2(-/-) than control macrophages. Activation of the STAT signaling pathway has been shown to elicit expression of CASP1 and apoptosis. IRF-2(-/-) macrophages exhibited increased basal and gliotoxin-induced caspase-1 mRNA expression and enhanced caspase-1 activity. Pharmacologic inhibition of STAT3 and caspase-1 abolished gliotoxin-induced apoptosis in IRF-2(-/-) macrophages. A novel IFN-stimulated response element, identified within the murine promoter of Casp1, was determined to be functional by EMSA and supershift analysis. Collectively, these data support the hypothesis that IRF-2 acts as a transcriptional repressor of Casp1, and that the absence of IRF-2 renders macrophages more sensitive to apoptotic stimuli in a caspase-1-dependent process.

Adrenomedullin (AM) and adrenomedullin binding protein (AM-BP) in the bovine mammary gland and milk: Effects of stage of lactation and experimental intramammary E. coli infection

Adrenomedullin (AM) has been characterized as an endogenous tissue survival factor and modulator of many inflammatory processes. Because of the increased susceptibility of the mammary gland to infection during the time surrounding parturition in the cow, we investigated how milk and tissue content of AM and its binding protein (AM-BP) might be affected by the stage of lactation and the udder health status. Milk and mammary biopsy samples were obtained from Holstein cows 21 days prior to and at various times after calving to represent the dry period and early and mid-stages of lactation. Additional cows received an intramammary challenge with Escherichia coli for immunohistochemical characterization of AM and AM-BP. Milk AM concentrations were relatively constant across the stages of lactation while AM-BP increased two-fold (P<0.04) between early and mid-lactation. Milk AM (P<0.04) and AM-BP (P<0.03) increased as somatic cell counts (SCCs) increased within a given stage of lactation. Tissue content of both (AM and AM-BP) were significantly affected by stage of lactation, lowest in the dry period and progressively increasing to peak at mid-lactation as well as increasing in association with higher levels of SCCs. Following E. coli challenge, AM increased in epithelial cells surrounding mammary alveoli presenting high levels of SCCs. The data suggest that AM and AM-BP are cooperatively regulated in the mammary gland during lactation; changes in localized tissue AM and AM-BP content reflect a dynamic regulation of these tissue factors in the bovine mammary gland consistent with their protective effects within inflamed tissue.

Molecular evolution of proadrenomedullin N-terminal 20 peptide (PAMP): evidence for gene co-option

Posttranslational processing of proadrenomedullin generates two biologically active peptides, adrenomedullin (AM) and proadrenomedullin N-terminal 20 peptide (PAMP). Sequence comparison of homologous proadrenomedullin genes in vertebrate evolution shows a high degree of stability in the reading frame for AM, whereas PAMP sequence changes rapidly. Here we investigate the functional significance of PAMP phylogenetic variation studying two of PAMP's better characterized physiological activities, angiogenic potential and antimicrobial capability, with synthetic peptides carrying the predicted sequence for human, mouse, chicken, and fish PAMP. All tested peptides induced angiogenesis when compared with untreated controls, but chicken and fish PAMP, which lack terminal amidation, were apparently less angiogenic than their human and mouse homologs. Confirming the role of amidation in angiogenesis, Gly-extended and free acid variants of human PAMP produced responses similar to the natural nonamidated peptides. In contrast, antimicrobial activity was restricted to human PAMP, indicating that this function may have been acquired at a late time during the evolution of PAMP. Interestingly, free acid human PAMP retained antimicrobial activity whereas the Gly-extended form did not. This fact may reflect the need for maintaining a tightly defined structural conformation in the pore-forming mechanism proposed for these antimicrobial agents. The evolution of PAMP provides an example of an angiogenic peptide that developed antimicrobial capabilities without losing its original function.

The central role of adrenomedullin in host defense

Thirteen years after the isolation of adrenomedullin (AM) from a human pheochromocytoma, the literature is awash with reports describing its implication in countless physiological and disease mechanisms ranging from vasodilatation to cancer promotion. A growing body of evidence illustrates AM as a pivotal component in normal physiology and disease with marked beneficial effects in the host defense mechanism. Exogenous administration of AM as well as its ectopic overexpression and the use of drugs, which potentiates its activity, are promising strategies for treatment of septic shock and several other pathogen-related disorders. Although major progress toward this end has been achieved over the past few years, our further understanding of the pleiotropic mechanisms involved with AM as a protective peptide is paramount to maximize its clinical application.

Accelerated thymic maturation and autoreactive T cells in bronchopulmonary dysplasia

RATIONALE

Bronchopulmonary dysplasia (BPD), a chronic lung disease of newborns triggered by oxygen and barotrauma, is characterized by arrested alveolarization. Increased levels of bombesin-like peptides shortly after birth mediate lung injury: anti-bombesin antibody 2A11 protects against BPD in two baboon models. The role of adaptive immunity in BPD has not been explored previously.

OBJECTIVES

Our goal was to test the hypothesis that thymic architecture and/or T-cell function is altered with BPD, leading to autoimmunity and immunodeficiency.

METHODS

Thymic structure was analyzed by histopathology of thymic architecture and immunohistochemistry for thymic maturation markers (terminal deoxynucleotidyl transferase, proliferating cell nuclear antigen, CD4, and CD8). Thymic cortical epithelial cells (nurse cells) were studied using HLA-DR and protein gene product 9.5 as markers. Functional analysis was performed with "mixed lymphocyte reaction" of thymocyte or splenocyte responder cells with autologous lung cells as the stimulators.

MEASUREMENTS AND MAIN RESULTS

2A11 treatment attenuates thymic cortical involution in BPD animals, sustaining terminal deoxynucleotidyl transferase-positive prothymocytes and thymocyte proliferation. BPD animals have increased CD4(+) cells in thymic cortex and lung interstitium, which are reduced by 2A11. Conversely, cortical protein gene product 9.5/HLA-DR-positive thymic nurse cells are depleted in BPD animals, but are preserved by 2A11-treatment. Whereas fetal thymocytes and splenocytes respond to phythemagglutinin/ionomycin and to a lesser extent, to autologous lung, BPD thymocytes and splenocytes are phythemagglutinin/ionomycin-unresponsive, and yet react strongly to autologous lung. The 2A11 normalizes these responses.

CONCLUSIONS

These observations suggest that bombesin-like peptides mediate premature thymic maturation and thymic nurse-cell depletion, leading to autoreactive T cells that could contribute to lung injury.

Adrenomedullin is a cross-talk molecule that regulates tumor and mast cell function during human carcinogenesis

We have previously demonstrated that adrenomedullin (AM) plays a critical role as an autocrine/paracrine tumor cell survival factor. We now present evidence that AM is an important regulator of mast cell (MC) function and that this modulation is potentially involved in tumor promotion. AM induced histamine or beta-hexosaminidase release from rat and human MCs through a receptor-independent pathway. AM was chemotactic for human MCs and stimulated mRNA expression of vascular endothelial growth factor, monocyte chemoattractant protein-1, and basic fibroblast growth factor in this cell type. Differentiated but not undifferentiated human MCs responded to hypoxic insult with elevated AM mRNA/protein expression. Using confocal microscopy, we identified AM-producing MCs in tumor infiltrates of human breast and lung cancer patients. In mixed culture assays the AM-producing human MC line HMC-1 augmented both anchorage-dependent and -independent growth of human lung cancer A549 cells, an effect that was suppressed by MC-targeted siRNA AM knockdown. Finally, HMC-1 cells induced in vivo angiogenesis as assessed by directed in vivo angiogenesis assay analysis; neutralizing anti-AM monoclonal antibody blocked this ability. Our collective data suggest a new role for AM as a cross-talk molecule that integrates tumor and MC communication, underlying a unique promotion mechanism of human cancers.

Gastrin-releasing peptide (GRP) induces angiogenesis and the specific GRP blocker 77427 inhibits tumor growth in vitro and in vivo

Angiogenesis is becoming a major target for antitumor therapies, and identifying new angiogenic factors and their specific inhibitors may provide new avenues for tumor management. Here we identify gastrin-releasing peptide (GRP) as a new angiogenic molecule that is secreted by tumors and acts directly upon GRP receptors in the endothelial cells. Addition of GRP increases endothelial cell migration and cord formation in vitro, and induces angiogenesis in an in vivo assay. We have recently identified a small molecule GRP blocker, compound 77427. This inhibitor significantly reduced endothelial cell cord formation in vitro and angiogenesis in vivo. Conversely, when applied to VEGF-induced angiogenesis, the small molecule did not have any effect, demonstrating its specificity. Furthermore, this GRP blocker was able to reduce lung tumor cell growth in vitro as demonstrated by MTT and clonogenic assays. When applied to a xenograft model with lung cancer cells, compound 77427 reduced tumor volume to undetectable sizes, although when the treatment was suspended, tumors began to grow again at normal rates. Our collective observations indicate that GRP is a new angiogenic peptide and that its inhibition offers an attractive tool to reduce tumor burden.

Characterization of adrenomedullin in birds

Adrenomedullin (AM) is a multifunctional evolutionarily highly conserved peptide. Although its genomic and amino acid (aa) sequences are known in several mammalian species and in fish, the structure of the AM gene remains unknown in intermediate phyla, including birds. Here, we report the structure and aa sequence of the chicken (c) AM ortholog. The cAM gene is located at the short arm of chromosome 5, which shows high synteny with the short arm of human (h) chromosome 11, where hAM is located. Key sequences in the third intron have been conserved which allow for an alternative splicing mechanism, similar to the one found in mammals. The preprohormone contains two peptides with high homology to human proadrenomedullin N-terminal 20 peptide (PAMP) and hAM. We found through real-time PCR and immunocytochemistry cAM mRNA and peptide expression in a variety of chicken tissues, which parallel patterns observed for mammals, with the exception that cAM levels are almost non-detectable in brain. Similarly to mammals, cAM expression is upregulated under hypoxic conditions and following dexamethasone treatment. These data demonstrate a high degree of homology between the cAM gene and its mammalian ortholog and evolutionary conservation of the regulatory mechanisms controlling its expression.

Adrenomedullin: a new target for the design of small molecule modulators with promising pharmacological activities

Adrenomedullin (AM) is a 52-amino acid peptide with a pluripotential activity. AM is expressed in many tissues throughout the body, and plays a critical role in several diseases such as cancer, diabetes, cardiovascular and renal disorders, among others. While AM is a protective agent against cardiovascular disorders, it behaves as a stimulating factor in other pathologies such as cancer and diabetes. Therefore, AM is a new and promising target for the development of molecules which, through their ability to regulate AM levels, could be used in the treatment of these pathologies.

Matrix metalloproteinase-2 cleavage of adrenomedullin produces a vasoconstrictor out of a vasodilator

MMPs (matrix metalloproteinases) play a major role in the pathogenesis of hypertension by altering the extracellular matrix during cardiovascular remodelling. In the present study we show that MMP-2, but not MMP-9, cleaves the vasodilator peptide AM (adrenomedullin). Addition of the AM-binding protein, complement factor H, prevents this cleavage, providing a hitherto unknown mechanism of action for this binding protein. We identified the signature cleavage fragments and found some of them in human urine, suggesting that MMP-2 processing of AM may occur in vivo. Synthetic AM fragments regulated blood pressure in rats. The larger peptides are vasodilators, as is intact AM, whereas intermediate fragments did not affect blood pressure. In contrast, AM(11-22) elicited vasoconstriction. Studies of AM receptor activation in Rat2 cells confirm that the larger AM cleavage peptides activated this receptor, whereas AM(11-22) did not. The present study defines a new mechanism through which MMP-2 may regulate blood pressure by simultaneously eliminating a vasodilator and generating a vasoconstrictor.

Proadrenomedullin NH2-terminal 20 peptide is a potent angiogenic factor, and its inhibition results in reduction of tumor growth

We have found through ex vivo and in vivo angiogenesis models that the adrenomedullin gene-related peptide, proadrenomedullin NH2-terminal 20 peptide (PAMP), exhibits a potent angiogenic potential at femtomolar concentrations, whereas classic angiogenic factors such as vascular endothelial growth factor and adrenomedullin mediate a comparable effect at nanomolar concentrations. We found that human microvascular endothelial cells express PAMP receptors and respond to exogenous addition of PAMP by increasing migration and cord formation. Exposure of endothelial cells to PAMP increases gene expression of other angiogenic factors such as adrenomedullin, vascular endothelial growth factor, basic fibroblast growth factor, and platelet-derived growth factor C. In addition, the peptide fragment PAMP(12-20) inhibits tumor cell-induced angiogenesis in vivo and reduces tumor growth in xenograft models. Together, our data demonstrate PAMP to be an extremely potent angiogenic factor and implicate this peptide as an attractive molecular target for angiogenesis-based antitumor therapy.

Characterization of adrenomedullin in non-human primates

Adrenomedullin (AM) is a 52 amino acid peptide involved in the pathophysiology of several human diseases. Here we show the gene structure, organ distribution, and regulated expression of AM in monkey. The monkey AM (mAM) gene is located on the short arm of chromosome 9 and it codes for a 185 amino acid preprohormone, which contains two amidated peptides identical to the human AM and proadrenomedullin N-terminal 20 peptide. The promoter region of the mAM gene contains a variety of transcription factor binding motifs. mAM is widely expressed throughout many organs as shown by real-time PCR and immunohistochemical techniques, and we have found similar levels of circulating plasma AM in monkeys and humans. A significant upregulation of the mAM mRNA was observed in monkey cells exposed to low oxygen tension conditions, TGF-beta1, all-trans-retinoic acid, and dexamethasone. Our collective data show a high degree of homology between mAM and hAM, which renders the monkey an attractive animal model for future pharmacological and pre-clinical studies targeting AM.

Expression of complement factor H by lung cancer cells: effects on the activation of the alternative pathway of complement

The complement system is important in immunosurveillance against tumors. However, malignant cells are usually resistant to complement-mediated lysis. In this study, we examine the expression of factor H, an inhibitor of complement activation, and factor H-like protein 1 (FHL-1), its alternatively spliced form, in lung cancer. We also evaluate the potential effect of factor H/FHL-1 in the protection of lung cancer cells against the activation of the complement cascade. By Northern blot analysis we demonstrate a high expression of factor H and FHL-1 in most non-small cell lung cancer cell lines, although neuroendocrine pulmonary tumors (small cell lung carcinoma and carcinoid cell lines) had undetectable levels. Western blot analysis of conditioned medium showed the active secretion of factor H and FHL-1 by cells that were positive by Northern blot. Expression of factor H/FHL-1 mRNA was also shown in a series of non-small cell lung cancer biopsies by in situ hybridization. Interestingly, many cultured lung cancer cells were able to bind fluorescence-labeled factor H to their surfaces. Deposition of C3 fragments from normal human serum on H1264, a lung adenocarcinoma cell line, was more efficient when factor H/FHL-1 activity was blocked by specific antibodies. Blocking factor H/FHL-1 activity also enhanced the release of anaphylatoxin C5a and moderately increased the susceptibility of these cells to complement-mediated cytotoxicity. In summary, we demonstrate the expression of factor H and FHL-1 by some lung cancer cells and analyze the contribution of these proteins to the protection against complement activation.

Identification of vasoactive nonpeptidic positive and negative modulators of adrenomedullin using a neutralizing antibody-based screening strategy

Adrenomedullin (AM) is a peptide hormone implicated in blood pressure regulation and in the pathophysiology of important diseases, such as hypertension, cancer, and diabetes. However, nonpeptidic modulators of this peptide that could be used to clinically regulate its actions are not available. We present here an efficient new method to screen a large library of small molecules. This technology was applied to the identification of positive and negative modulators of AM function. A two-tier screening strategy was developed in which the first screening entails disruption of the interaction between the peptide and a neutralizing monoclonal antibody. Selected compounds were further characterized by their ability to modulate second messengers in cells containing specific AM receptors. A parallel screen against gastrin-releasing peptide selected a different subset of molecules, confirming the specificity of the screening method. Identified AM-positive regulators reduced blood pressure in vivo, whereas AM-negative regulators mediated vasoconstriction, as predicted by the vasodilatory activity of AM. Binding of the small molecules to immobilized AM was demonstrated by surface plasmon resonance assays, with K(d) values ranging from 7.76 x 10(-9) to 4.14 x 10(-6) m. Preclinical development of AM modulators may result in useful drugs for the prevention and treatment of hypertension, cancer, and diabetes.

Anti-angiogenic activity of human endostatin is HIF-1-independent in vitro and sensitive to timing of treatment in a human saphenous vein assay

Endostatin is a 20-kDa endogenous angiogenesis inhibitor that has recently been shown to inhibit the expression of vascular endothelial growth factor (VEGF), an angiogenic growth factor that is up-regulated by hypoxia via the HIF-1 transcription factor complex. To determine if the anti-angiogenic activity of endostatin involves a modulation of the HIF-1/VEGF pathway in cancer cells, experiments were conducted to establish what effect endostatin has on HIF-1 activity, HIF-1alpha protein production, and cellular localization in prostate cancer cells and endothelial cells. Endothelial cell tube formation was inhibited by endostatin purchased from Calbiochem (San Diego, CA) but not endostatin obtained from EntreMed (Rockville, MD). Subsequent experiments using Calbiochem endostatin showed that it did not alter HIF-1alpha protein production or cellular localization in any of the cell lines tested, nor did it alter HIF-1 transactivational activity in hypoxia. Whether or not this is also true in vivo remains to be determined. Nevertheless, these data suggest that the anti-angiogenic activity of endostatin is independent of the HIF-1/VEGF pathway. Immunocytochemical staining results do not indicate a decreased production of VEGF in Calbiochem endostatin-treated LNCaP or human umbilical vein endothelial cells (HUVEC). Treatment of rat aortic cross sections with human endostatin from Calbiochem resulted in a dose-dependent inhibition of microvessel outgrowth. Importantly, inhibition of vessel outgrowth by Calbiochem endostatin in a human saphenous vein angiogenesis assay required early treatment. In view of this in vitro data, we suggest that clinical trials involving endostatin treatment of late-stage disease may not adequately represent the efficacy of this drug in early-stage cancer.

Distribution and possible function of an adrenomedullin-like peptide in the developing chick limb bud

Adrenomedullin (AM) is a multifunctional peptide that exhibits discrete domains of expression during mouse embryogenesis consistent with a role in regulating growth and differentiation during morphogenesis. Here we report that AM immunoreactivity is present at high levels throughout the apical ectodermal ridge (AER) of the chick limb bud as the AER is directing the outgrowth and patterning of underlying limb mesoderm. Immunostaining is particularly strong along the surfaces of the contiguous cells of the AER. AM immunoreactivity attenuates as the AER regresses and is absent from the distal apical ectoderm of stage 20 limbless mutant limb buds which fail to develop an AER. To explore the possible role of AM in AER activity, we examined the effect of exogenous AM and an AM inhibitor on the in vitro morphogenesis of limb mesoderm, cultured in the presence and absence of the AER. Although exogenous AM cannot substitute for the AER in promoting outgrowth of limb mesoderm in vitro, a specific AM antagonist, AM(22-52), impairs the outgrowth and proliferation of limb mesoderm cultured in the presence of the AER. This is consistent with the possibility that inhibition of endogenous AM activity in the AER impairs the ability of the AER to promote limb morphogenesis. Taken together, these studies suggest that an AM-like molecule may function in an autocrine fashion to regulate some aspect of AER activity.

Distribution of immunoreactivity for the adrenomedullin binding protein, complement factor H, in the rat brain

Adrenomedullin is a multifunctional amidated peptide that has been found in most nuclei of the CNS, where it plays a neuromodulatory role. An adrenomedullin binding protein has recently been found in plasma and characterized as complement factor H. This regulator of the complement system inhibits the progression of the complement cascade and modulates the function of adrenomedullin. Our study shows the ample distribution of factor H immunoreactivity in neurons of telencephalon, diencephalon, mesencephalon, pons, medulla, and cerebellum in the rat CNS, using immunohistochemical techniques for both light and electron microscopy. Factor H immunoreactivity was found in the cytoplasm, but nuclear staining was also a common finding. Some blood vessels and glial cells were also immunoreactive for factor H. Colocalization studies by double immunofluorescence followed by confocal microscopy revealed frequent coexistence of factor H and adrenomedullin immunoreactivities, thus providing morphological evidence for the potential interaction of these molecules in the CNS. The presence of factor H immunoreactivity in glial cells was confirmed by colocalization with glial fibrillary acidic protein. In summary, factor H is highly expressed in the CNS where it could play important roles in regulating adrenomedullin actions and contributing to an intracerebral complement system.

Adrenomedullin and cancer

Adrenomedullin (AM) is a pluripotent hormone with structural similarities to calcitonin gene-related peptide (CGRP), which is expressed by many tissues in the body and shows a remarkable range of effects mediated by paracrine/autocrine and possibly endocrine mechanisms. AM has been implicated as a mediator of several pathologies such as cardiovascular and renal disorders, sepsis, inflammation, diabetes and cancer, among others. AM is expressed in a variety of tumors where it aggravates several of the molecular and physiological features of malignant cells. AM has been shown to be a mitogenic factor stimulating growth in several cancer types and to encourage a more aggressive tumor phenotype. In addition, AM is an apoptosis survival factor for cancer cells and an indirect suppressor of the immune response through its binding protein, complement factor H, and regulation in expression of cytokines. AM plays an important role in environments subjected to low oxygen tensions, which is a typical feature in the proximity of solid tumors. Under these conditions, AM is upregulated through a hypoxia-inducible factor 1 (HIF-1)-dependent pathway and acts as a potent angiogenic factor promoting neovascularization. The collective findings brought together over the last years place AM as a major regulator of carcinogenesis-tumor progression and identifies its autocrine loop as a putative target for developing new strategies against human cancers.

Regulation of pancreatic physiology by adrenomedullin and its binding protein

Adrenomedullin (AM) is a 52 amino acid, multifunctional hormone. It is expressed in many tissues of the human body including the pancreas, where it is mainly localized to the periphery of the islets of Langerhans and specifically to the pancreatic polypeptide-expressing cells. The AM receptor, a complex formed by calcitonin receptor-like receptor (CRLR) and receptor activity-modifying proteins (RAMPs), and the recently discovered AM-binding protein, complement factor H (fH), are expressed in the insulin-producing beta-cells. The colocalization of these key elements of the AM system in the endocrine portion of the pancreas implicates AM in the control of both normal and altered pancreatic physiologies. AM inhibits insulin secretion both in vitro (isolated rat islets) and in vivo (oral glucose tolerance test in rats) in a dose-dependent manner. The addition of fH to isolated rat islets produces a further reduction of insulin secretion in the presence of AM. Furthermore, AM is elevated in plasma from patients with pancreatic dysfunctions such as type 1 or type 2 diabetes and insulinoma. Using a diabetic model in rats, we have shown that AM increases circulating glucose levels whereas a blocking monoclonal antibody against AM has the opposite effect and improves postprandial recovery. Such experimental evidence implicates AM as a fundamental factor in maintaining insulin homeostasis and normoglycemia, and suggests the implication of AM as a possible causal agent in diabetes. Further investigation focused on the development of blocking agents for AM could result in new treatments for pancreatic AM-related disorders.

Mapping of the adrenomedullin-binding domains in human complement factor H

Adrenomedullin (AM) is a multifunctional peptide involved in roles as varied as blood pressure regulation, growth, neurotransmission, and inflammation control, among others. We previously identified complement factor H as a serum binding protein for AM and showed that factor H regulates AM functions and vice versa. Here we searched for the specific binding sites for AM by using recombinant fragments of factor H and a non-radioactive binding assay with fluorescein-tagged AM. By this methodology, two specific binding sites for AM were found in factor H. One of them shows a high affinity for AM and is located at the carboxy terminal end of factor H, comprising short consensus repeats (SCR) 15-20. Smaller fragments of this region did not bind to AM efficiently, suggesting that the high affinity binding site of factor H requires a complex three-dimensional structure to recognize AM. Another binding site with lower affinity for AM was found in the middle of the factor H molecule, at SCR 8-11. Antibodies against factor H prevented AM binding altogether, but the main binding partner of factor H, C3b, did not, indicating that C3b and AM bind to different regions of factor H. These structure-function data support previous biochemical observations. Our understanding of the binding between AM and factor H may help in the development of new treatments for diseases in which these molecules play active roles.

Overexpression of adrenomedullin gene markedly inhibits proliferation of PC3 prostate cancer cells in vitro and in vivo

The expression of the gene encoding adrenomedullin (AM), a multifunctional peptide hormone, in the prostate is localized to the epithelial cells. Prostate cancer cells are derived from prostatic epithelial cells. To elucidate the potential role of the AM gene in prostate cancer progression, we have stably-transfected the PC3 human prostate cancer cell line with an AM gene expression vector. The AM-transfected PC3 sublines were studied along with parental and empty vector transfected PC3 cells as controls. The average level of AM in the conditioned media of AM-transfected cells was 0.959+/-0.113 nM, a physiologically relevant concentration. The ectopic expression of AM gene inhibited the proliferation of PC3 cells in culture dishes. In addition, anchorage-independent growth of the transfected sublines was virtually abolished in soft agar assays. Flow cytometry studies showed that overexpression of AM gene caused a very significant G(1)/G(0) cell cycle arrest. In vivo experiments demonstrated that AM gene expression markedly inhibited the growth of xenograft tumors in nude mice. Our in vivo and in vitro studies suggest that AM could strongly suppress the malignancy of prostate cancer cells, via autocrine and/or paracrine mechanisms.

Downregulation of hnRNP A2/B1 expression in tumor cells under prolonged hypoxia

Heterogeneous nuclear ribonucleoprotein (hnRNP) A2/B1 has been previously shown to be overexpressed in breast and lung tumors. Because hypoxia is a feature inherent in solid tumors, the regulation of hnRNP A2/B1 expression and subcellular localization under hypoxic conditions was studied on human lung and breast carcinoma cell lines. We found that sustained hypoxic treatment downregulated hnRNP A2/B1 expression in MCF7 and H157 cell lines. Northern blot analysis showed that this decay: (i) was observed as a marked diminution of transcript levels after 24-48 h of exposure to low oxygen tension; (ii) is not mediated by the transcription factor, hypoxia inducible factor-1; and (iii) is partially dependent on a higher hnRNP A2/B1 messenger RNA turnover under hypoxic than normoxic conditions. Immunocytochemical staining also showed a significant diminution of hnRNP A2/B1 staining in these cell lines after 24-48 h of hypoxia, together with a predominant loss of cytoplasmic staining. Further investigations are warranted to evaluate the relevance of modulation of hnRNP A2/B1 in hypoxic environments relative to its previously reported utility as a marker of early lung carcinogenesis.