Correction: Ponzo et al. Nucleolin Therapeutic Targeting Decreases Pancreatic Cancer Immunosuppression. Cancers 2022, 14, 4265

In the original publication [...].

Nucleolin Aptamer N6L Reprograms the Translational Machinery and Acts Synergistically with mTORi to Inhibit Pancreatic Cancer Proliferation

Simple Summary

Pancreatic cancer is an aggressive disease characterized by its invasiveness, rapid progression, and resistance to conventional therapy. There is a need to identify new molecules to improve current therapies. The aim of this study was to analyze how the pancreatic cancer cells react to the treatment with an inhibitor of nucleolin, N6L. To this end, we analyzed how the translation was affected in the cells during the treatment. We discovered that in response to N6L, a signaling pathway called the mTOR pathway was activated and was involved in the activation of translation of a subset of mRNA that could be involved in the resistance of the cells to the treatment. Indeed, we showed that the combined action of inhibitors of the mTOR pathway with N6L synergistically inhibited the cancer cells’ proliferation. We propose that this new combination of molecules could be a novel therapeutic option for pancreatic cancer.

Abstract

We previously showed that N6L, a pseudopeptide that targets nucleolin, impairs pancreatic ductal adenocarcinoma (PDAC) growth and normalizes tumor vessels in animal models. In this study, we analyzed the translatome of PDAC cells treated with N6L to identify the pathways that were either repressed or activated. We observed a strong decrease in global protein synthesis. However, about 6% of the mRNAs were enriched in the polysomes. We identified a 5′TOP motif in many of these mRNAs and demonstrated that a chimeric RNA bearing a 5‘TOP motif was up-regulated by N6L. We demonstrated that N6L activates the mTOR pathway, which is required for the translation of these mRNAs. An inhibitory synergistic effect in PDAC cell lines, including patient-derived xenografts and tumor-derived organoids, was observed when N6L was combined with mTOR inhibitors. In conclusion, N6L reduces pancreatic cells proliferation, which then undergoes translational reprogramming through activation of the mTOR pathway. N6L and mTOR inhibitors act synergistically to inhibit the proliferation of PDAC and human PDX cell lines. This combotherapy of N6L and mTOR inhibitors could constitute a promising alternative to treat pancreatic cancer.

The Extracellular Matrix in Pancreatic Cancer: Description of a Complex Network and Promising Therapeutic Options

The stroma is a relevant player in driving and supporting the progression of pancreatic ductal adenocarcinoma (PDAC), and a large body of evidence highlights its role in hindering the efficacy of current therapies. In fact, the dense extracellular matrix (ECM) characterizing this tumor acts as a natural physical barrier, impairing drug penetration. Consequently, all of the approaches combining stroma-targeting and anticancer therapy constitute an appealing option for improving drug penetration. Several strategies have been adopted in order to target the PDAC stroma, such as the depletion of ECM components and the targeting of cancer-associated fibroblasts (CAFs), which are responsible for the increased matrix deposition in cancer. Additionally, the leaky and collapsing blood vessels characterizing the tumor might be normalized, thus restoring blood perfusion and allowing drug penetration. Even though many stroma-targeting strategies have reported disappointing results in clinical trials, the ECM offers a wide range of potential therapeutic targets that are now being investigated. The dense ECM might be bypassed by implementing nanoparticle-based systems or by using mesenchymal stem cells as drug carriers. The present review aims to provide an overview of the principal mechanisms involved in the ECM remodeling and of new promising therapeutic strategies for PDAC.

Nucleolin Targeting by N6L Inhibits Wnt/β-Catenin Pathway Activation in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive and resistant cancer with no available effective therapy. We have previously demonstrated that nucleolin targeting by N6L impairs tumor growth and normalizes tumor vessels in PDAC mouse models. Here, we investigated new pathways that are regulated by nucleolin in PDAC. We found that N6L and nucleolin interact with β-catenin. We found that the Wnt/β-catenin pathway is activated in PDAC and is necessary for tumor-derived 3D growth. N6L and nucleolin loss of function induced by siRNA inhibited Wnt pathway activation by preventing β-catenin stabilization in PDAC cells. N6L also inhibited the growth and the activation of the Wnt/β-catenin pathway in vivo in mice and in 3D cultures derived from MIA PaCa2 tumors. On the other hand, nucleolin overexpression increased β-catenin stabilization. In conclusion, in this study, we identified β-catenin as a new nucleolin interactor and suggest that the Wnt/β-catenin pathway could be a new target of the nucleolin antagonist N6L in PDAC.

Tumor stiffening reversion through collagen crosslinking inhibition improves T cell migration and anti-PD-1 treatment

Only a fraction of cancer patients benefits from immune checkpoint inhibitors. This may be partly due to the dense extracellular matrix (ECM) that forms a barrier for T cells. Comparing five preclinical mouse tumor models with heterogeneous tumor microenvironments, we aimed to relate the rate of tumor stiffening with the remodeling of ECM architecture and to determine how these features affect intratumoral T cell migration. An ECM-targeted strategy, based on the inhibition of lysyl oxidase, was used. In vivo stiffness measurements were found to be strongly correlated with tumor growth and ECM crosslinking but negatively correlated with T cell migration. Interfering with collagen stabilization reduces ECM content and tumor stiffness leading to improved T cell migration and increased efficacy of anti-PD-1 blockade. This study highlights the rationale of mechanical characterizations in solid tumors to understand resistance to immunotherapy and of combining treatment strategies targeting the ECM with anti-PD-1 therapy.

Cell surface nucleolin as active bait for nanomedicine in cancer therapy: a promising option

Conventional chemotherapy used against cancer is mostly limited due to their non-targeted nature, affecting normal tissue and causing undesirable toxic effects to the affected tissue. With the aim of improving these treatments both therapeutically and in terms of their safety, numerous studies are currently being carried out using nanoparticles (NPs) as a vector combining tumor targeting and carrying therapeutic tools. In this context, it appears that nucleolin, a molecule over-expressed on the surface of tumor cells, is an interesting therapeutic target. Several ligands, antagonists of nucleolin of various origins, such as AS1411, the F3 peptide and the multivalent pseudopeptide N6L have been developed and studied as therapeutic tools against cancer. Over the last ten years or so, numerous studies have been published demonstrating that these antagonists can be used as tumor targeting agents with NPs from various origins. Focusing on nucleolin ligands, the aim of this article is to review the literature recently published or under experimentation in our research team to evaluate the efficacy and future development of these tools as anti-tumor agents.

Iron Oxide Nanoparticles as Carriers for DOX and Magnetic Hyperthermia after Intratumoral Application into Breast Cancer in Mice: Impact and Future Perspectives

There is still a need for improving the treatment of breast cancer with doxorubicin (DOX). In this paper, we functionalized magnetic nanoparticles (MNPs) with DOX and studied the DOX-induced antitumor effects in breast cancer cells (BT474) in the presence of magnetic hyperthermia (43 °C, 1 h). We show that i) intratumoral application of DOX-functionalized MNPs (at least at a concentration of 9.6 nmol DOX/100 mm³ tumor volume) combined with magnetic hyperthermia favors tumor regression in vivo, and there is evidence for an increased effect compared to magnetic hyperthermia alone or to the intratumoral application of free DOX and ii) the presence of the pseudopeptide NucAnt (N6L) on the MNP surface might well be beneficial in its function as carrier for MNP internalization into breast cancer cells in vitro, which could further augment the possibility of the induction of intracellular heating spots and cell death in the future.

Antagonist of nucleolin, N6L, inhibits neovascularization in mouse models of retinopathies

Retinal vascular diseases (RVD) have been identified as a major cause of blindness worldwide. These pathologies, including the wet form of age-related macular degeneration, retinopathy of prematurity, and diabetic retinopathy are currently treated by intravitreal delivery of anti-vascular endothelial growth factor (VEGF) agents. However, repeated intravitreal injections can lead to ocular complications and resistance to these treatments. Thus, there is a need to find new targeted therapies. Nucleolin regulates the endothelial cell (EC) activation and angiogenesis. In previous studies, we designed a pseudopeptide, N6L, that binds the nucleolin and blocks the tumor angiogenesis. In this study, the effect of N6L was investigated in two experimental models of retinopathies including oxygen-induced retinopathy (OIR) and choroidal neovascularization (CNV). We found that in mouse OIR, intraperitoneal injection of N6L is delivered to activated ECs and induced a 50% reduction of pathological neovascularization. The anti-angiogenic effect of N6L has been tested in CNV model in which the systemic injection of N6L induced a 33% reduction of angiogenesis. This effect is comparable to those obtained with VEGF-trap, a standard of care drug for RVD. Interestingly, with preventive and curative treatments, neoangiogenesis is inhibited by 59%. Our results have potential interest in the development of new therapies targeting other molecules than VEGF for RVD.

Aerosol-Assisted Synthesis of Tailor-Made Hollow Mesoporous Silica Microspheres for Controlled Release of Antibacterial and Anticancer Agents

Hollow mesoporous silica microsphere (HMSM) particles are one of the most promising vehicles for efficient drug delivery owing to their large hollow interior cavity for drug loading and the permeable mesoporous shell for controlled drug release. Here, we report an easily controllable aerosol-based approach to produce HMSM particles by continuous spray-drying of colloidal silica nanoparticles and Eudragit/Triton X100 composite (EUT) nanospheres as templates, followed by template removal. Importantly, the internal structure of the hollow cavity and the external morphology and the porosity of the mesoporous shell can be tuned to a certain extent by adjusting the experimental conditions (i.e., silica to EUT mass ratio and particle size of silica nanoparticles) to optimize the drug loading capacity and the controlled-release properties. Then, the application of aerosol-synthesized HMSM particles in controlled drug delivery was investigated by loading amoxicillin as an antibiotic compound with high entrapment efficiency (up to 46%). Furthermore, to improve the biocompatibility of the amoxicillin-loaded HMSM particles, their surfaces were functionalized with poly(allylamine hydrochloride) and alginate as biocompatible polymers via the layer-by-layer assembly. The resulting particles were evaluated toward Escherichia coli (Gram-negative) bacteria and indicated the bacterial inhibition up to 90% in less than 2 h. Finally, we explored the versatility of HMSMs as drug carriers for pancreatic cancer treatment. Because the pH value of the extracellular medium in pancreatic tumors is lower than that of the healthy tissue, chitosan as a pH-sensitive gatekeeper was grafted to the HMSM surface and then loaded with a pro-apoptotic NCL antagonist agent (N6L) as an anticancer drug. The obtained particles exhibited pH-responsive drug releases and excellent anticancer activities with inhibition of cancer cell growth up to 60%.

Weibel-Palade Bodies Orchestrate Pericytes During Angiogenesis

Objective Weibel-Palade bodies (WPBs) are endothelial cell (EC)-specific organelles formed by vWF (von Willebrand factor) polymerization and that contain the proangiogenic factor Ang-2 (angiopoietin-2). WPB exocytosis has been shown to be implicated for vascular repair and inflammatory responses. Here, we investigate the role of WPBs during angiogenesis and vessel stabilization. Approach and Results WPB density in ECs decreased at the angiogenic front of retinal vascular network during development and neovascularization compared with stable vessels. In vitro, VEGF (vascular endothelial growth factor) induced a VEGFR-2 (vascular endothelial growth factor receptor-2)-dependent exocytosis of WPBs that contain Ang-2 and consequently the secretion of vWF and Ang-2. Blocking VEGF-dependant WPB exocytosis and Ang-2 secretion promoted pericyte migration toward ECs. Pericyte migration was inhibited by adding recombinant Ang-2 or by silencing Ang-1 (angiopoietin-1) or Tie2 (angiopoietin-1 receptor) in pericytes. Consistently, in vivo anti-VEGF treatment induced accumulation of WPBs in retinal vessels because of the inhibition of WPB exocytosis and promoted the increase of pericyte coverage of retinal vessels during angiogenesis. In tumor angiogenesis, depletion of WPBs in vWF knockout tumor-bearing mice promoted an increase of tumor angiogenesis and a decrease of pericyte coverage of tumor vessels. By another approach, normalized tumor vessels had higher WPB density. Conclusions We demonstrate that WPB exocytosis and Ang-2 secretion are regulated during angiogenesis to limit pericyte coverage of remodeling vessels by disrupting Ang-1/Tie2 autocrine signaling in pericytes.

The phenotype of target pancreatic cancer cells influences cell death by magnetic hyperthermia with nanoparticles carrying gemicitabine and the pseudo-peptide NucAnt

In this paper we show that conjugation of magnetic nanoparticles (MNPs) with Gemcitabine and/or NucAnt (N6L) fostered their internalization into pancreatic tumor cells and that the coupling procedure did not alter the cytotoxic potential of the drugs. By treating tumor cells (BxPC3 and PANC-1) with the conjugated MNPs and magnetic hyperthermia (43 °C, 60 min), cell death was observed. The two pancreatic tumor cell lines showed different reactions against the combined therapy according to their intrinsic sensitivity against Gemcitabine (cell death, ROS production, ability to activate ERK 1/2 and JNK). Finally, tumors (e.g. 3 mL) could be effectively treated by using almost 4.2 × 10⁵ times lower Gemcitabine doses compared to conventional therapies. Our data show that this combinatorial therapy might well play an important role in certain cell phenotypes with low readiness of ROS production. This would be of great significance in distinctly optimizing local pancreatic tumor treatments.

Targeted therapy of human glioblastoma via delivery of a toxin through a peptide directed to cell surface nucleolin

Targeted anticancer therapies demand discovery of new cellular targets to be exploited for the delivery of toxic molecules and drugs. In this perspective, in the last few years, nucleolin has been identified as an interesting surface marker to be used for the therapy of glioblastoma. In this study, we investigated whether a synthetic antagonist of cell-surface nucleolin known as N6L, previously reported to decrease both tumor growth and tumor angiogenesis in several cancer cell lines, including glioblastoma cells, as well as endothelial cells proliferation, could be exploited to deliver a protein toxin (saporin) to glioblastoma cells. The pseudopeptide N6L cross-linked to saporin-S6 induced internalization of the toxin inside glioblastoma cancer cells. Our results in vitro demonstrated the effectiveness of this conjugate in inducing cell death, with an ID50 four orders of magnitude lower than that observed for free N6L. Furthermore, the preliminary in vivo study demonstrated efficiency in reducing the tumor mass in an orthotopic mouse model of glioblastoma.

Implication of NPM1 phosphorylation and preclinical evaluation of the nucleoprotein antagonist N6L in prostate cancer

Despite the advent of several new treatment options over the past years, advanced/metastatic prostate carcinoma (PCa) still remains incurable, which justifies the search for novel targets and therapeutic molecules. Nucleophosmin (NPM1) is a shuttling nucleoprotein involved in tumor growth and its targeting could be a potential approach for cancer therapy. We previously demonstrated that the multivalent pseudopeptide N6L binds to NPM1 potently affecting in vitro and in vivo tumor cell growth of various tumor types as well as angiogenesis. Furthermore, NPM1 binds to androgen receptor (AR) and modulate its activity. In this study, we first investigated the implication of the NPM1 and its Thr199 and Thr234/237 phosphorylated forms in PCa. We showed that phosphorylated forms of NPM1 interact with androgen receptor (AR) in nucleoplasm. N6L treatment of prostate tumor cells led to inhibition of NPM1 phosphorylation in conjunction with inhibition of AR activity. We also found that total and phosphorylated NPM1 were overexpressed in castration-resistant PCa. Assessment of the potential therapeutic role of N6L in PCa indicated that N6L inhibited tumor growth both in vitro and in vivo when used either alone or in combination with the standard-of-care first- (hormonotherapy) and second-line (docetaxel) treatments for advanced PCa. Our findings reveal the role of Thr199 and Thr234/237 phosphorylated NPM1 in PCa progression and define N6L as a new drug candidate for PCa therapy.

Evidence for Novel Action at the Cell-Binding Site of Human Angiogenin Revealed by Heteronuclear NMR Spectroscopy, in silico and in vivo Studies

A member of the ribonuclease A superfamily, human angiogenin (hAng) is a potent angiogenic factor. Heteronuclear NMR spectroscopy combined with induced-fit docking revealed a dual binding mode for the most antiangiogenic compound of a series of ribofuranosyl pyrimidine nucleosides that strongly inhibit hAng's angiogenic activity in vivo. While modeling suggests the potential for simultaneous binding of the inhibitors at the active and cell-binding sites, NMR studies indicate greater affinity for the cell-binding site than for the active site. Additionally, molecular dynamics simulations at 100 ns confirmed the stability of binding at the cell-binding site with the predicted protein-ligand interactions, in excellent agreement with the NMR data. This is the first time that a nucleoside inhibitor is reported to completely inhibit the angiogenic activity of hAng in vivo by exerting dual inhibitory activity on hAng, blocking both the entrance of hAng into the cell and its ribonucleolytic activity.

N6L pseudopeptide interferes with nucleophosmin protein-protein interactions and sensitizes leukemic cells to chemotherapy

NPM1 is a multifunctional nucleolar protein implicated in several processes such as ribosome maturation and export, DNA damage response and apoptotic response to stress stimuli. The NPM1 gene is involved in human tumorigenesis and is found mutated in one third of acute myeloid leukemia patients, leading to the aberrant cytoplasmic localization of NPM1. Recent studies indicated that the N6L multivalent pseudopeptide, a synthetic ligand of cell-surface nucleolin, is also able to bind NPM1 with high affinity. N6L inhibits cell growth with different mechanisms and represents a good candidate as a novel anticancer drug for a number of malignancies of different histological origin. In this study we investigated whether N6L treatment could drive antitumor effect in acute myeloid leukemia cell lines. We found that N6L binds NPM1 at the N-terminal domain, co-localizes with cytoplasmic, mutated NPM1, and interferes with its protein-protein associations. N6L toxicity appears to be p53 dependent but interestingly, the leukemic cell line harbouring the mutated form of NPM1 is more resistant to treatment, suggesting that NPM1 cytoplasmic delocalization confers protection from p53 activation. Moreover, we show that N6L sensitizes AML cells to doxorubicin and cytarabine treatment. These studies suggest that N6L may be a promising option in combination therapies for acute myeloid leukemia treatment.

Multivalent cationic pseudopeptide polyplexes as a tool for cancer therapy

In this study, a novel anticancer reagent based on polyplexes nanoparticles was developed. These nanoparticles are obtained by mixing negatively charged polyelectrolytes with the antitumour cationically-charged pseudopeptide N6L. Using two in vivo experimental tumor pancreatic models based upon PANC-1 and mPDAC cells, we found that the antitumour activity of N6L is significantly raised via its incorporation in polyplexed nanoparticles. Study of the mechanism of action using affinity isolation and si-RNA experiments indicated that N6L-polyplexes are internalized through their interaction with nucleolin. In addition, using a very aggressive model of pancreatic cancer in which gemcitabine, a standard of care for this type of cancer, has a weak effect on tumour growth, we observed that N6L-polyplexes administration has a stronger efficacy than gemcitabine. Biodistribution studies carried out in tumour-bearing mice indicated that N6L-polyplexes localises in tumour tissue, in agreement with its antitumour effect. These results support the idea that N6L nanoparticles could develop into a promising strategy for the treatment of cancer, especially hard-to-treat pancreatic cancers.

Nucleolin Targeting Impairs the Progression of Pancreatic Cancer and Promotes the Normalization of Tumor Vasculature

Pancreatic cancer is a highly aggressive tumor, mostly resistant to the standard treatments. Nucleolin is overexpressed in cancers and its inhibition impairs tumor growth. Herein, we showed that nucleolin was overexpressed in human specimens of pancreatic ductal adenocarcinoma (PDAC) and that the overall survival significantly increased in patients with low levels of nucleolin. The nucleolin antagonist N6L strongly impaired the growth of primary tumors and liver metastasis in an orthotopic mouse model of PDAC (mPDAC). Similar antitumor effect of N6L has been observed in a highly angiogenic mouse model of pancreatic neuroendocrine tumor RIP-Tag2. N6L significantly inhibited both human and mouse pancreatic cell proliferation and invasion. Notably, the analysis of tumor vasculature revealed a strong increase of pericyte coverage and vessel perfusion both in mPDAC and RIP-Tag2 tumors, in parallel to an inhibition of tumor hypoxia. Nucleolin inhibition directly affected endothelial cell (EC) activation and changed a proangiogenic signature. Among the vascular activators, nucleolin inhibition significantly decreased angiopoietin-2 (Ang-2) secretion and expression in ECs, in the tumor and in the plasma of mPDAC mice. As a consequence of the observed N6L-induced tumor vessel normalization, pre-treatment with N6L efficiently improved chemotherapeutic drug delivery and increased the antitumor properties of gemcitabine in PDAC mice. In conclusion, nucleolin inhibition is a new anti-pancreatic cancer therapeutic strategy that dually blocks tumor progression and normalizes tumor vasculature, improving the delivery and efficacy of chemotherapeutic drugs. Moreover, we unveiled Ang-2 as a potential target and suitable response biomarker for N6L treatment in pancreatic cancer. Cancer Res; 76(24); 7181-93. ©2016 AACR.

Abstract 3366: NCL targeting impairs the progression of pancreatic ductal adenocarcinoma and promotes tumor vessel normalization through Ang-2 inhibition

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive tumor, mostly resistant to the standard treatments. NCL is overexpressed in cancers and its inhibition impairs tumor growth. Herein we described, that NCL was overexpressed in human specimens of PDAC, and low NCL staining patients had increased overall survival. Previously, we described a family of multivalent pseudopeptides binding to NCL and inhibiting tumour growth. Here, NCL antagonist N6L, strongly impaired tumor growth, liver metastasis formation and angiogenesis in an orthothopic mouse model of PDAC. N6L inhibited both human and mouse tumor cell proliferation and invasion. Proteome analysis of endothelial cell secreted proteins showed that NCL inhibition decreased Ang-2 levels and switched a pro-angiogenic signature. Importantly, Ang-2 levels were decreased in plasma of N6L-treated PDAC mice. The analysis of tumor vasculature revealed a strong increase of pericyte coverage and vessel perfusion in parallel to an inhibition of tumor hypoxia. As consequence of N6L-induced tumor vessel normalization, pre-treatment with N6L efficiently improved chemotherapeutic drug delivery and increased the anti-tumor properties of gemcitabine in PDAC mice.

In conclusion, NCL inhibition is a new anti-tumor therapeutic strategy that dually blocks tumor progression and normalizes tumor vessels improving the delivery and efficacy of chemotherapeutic drugs in PDAC cancers. Moreover, we identified Ang-2 as a potential target and suitable response biomarker for N6L treatment in PDAC.

Citation Format: Maud-Emmanuelle Gilles, Federica Maione, Mélissande Cossutta, Gilles Carpentier, Laure Caruana, Silvia Di Maria, Damien Destouches, Ksenya Shchors, Christopher Prochasson, Anne Couvelard, José Courty, Enrico Giraudo, Ilaria Cascone. NCL targeting impairs the progression of pancreatic ductal adenocarcinoma and promotes tumor vessel normalization through Ang-2 inhibition. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3366.

Pleiotrophin exerts its migration and invasion effect through the neuropilin-1 pathway

Pleiotrophin (PTN) is a pleiotropic growth factor that exhibits angiogenic properties and is involved in tumor growth and metastasis. Although it has been shown that PTN is expressed in tumor cells, few studies have investigated its receptors and their involvement in cell migration and invasion. Neuropilin-1 (NRP-1) is a receptor for multiple growth factors that mediates cell motility and plays an important role in angiogenesis and tumor progression. Here we provide evidence for the first time that NRP-1 is crucial for biological activities of PTN. We found that PTN interacted directly with NRP-1 through its thrombospondin type-I repeat domains. Importantly, binding of PTN to NRP-1 stimulated the internalization and recycling of NRP-1 at the cell surface. Invalidation of NRP-1 by RNA interference in human carcinoma cells inhibited PTN-induced intracellular signaling of the serine-threonine kinase, mitogen-activated protein MAP kinase, and focal adhesion kinase pathways. Accordingly, NRP-1 silencing or blocking by antibody inhibited PTN-induced human umbilical vein endothelial cell migration and tumor cell invasion. These results suggest that NRP-1/PTN interaction provides a novel mechanism for controlling the response of endothelial and tumoral cells to PTN and may explain, at least in part, how PTN contributes to tumor angiogenesis and cancer progression.

Mutation-Independent Activation of the Anaplastic Lymphoma Kinase in Neuroblastoma

Activating mutations of anaplastic lymphoma kinase (ALK) have been identified as important players in neuroblastoma development. Our goal was to evaluate the significance of overall ALK activation in neuroblastoma. Expression of phosphorylated ALK, ALK, and its putative ligands, pleiotrophin and midkine, was screened in 289 neuroblastomas and 56 paired normal tissues. ALK was expressed in 99% of tumors and phosphorylated in 48% of cases. Pleiotrophin and midkine were expressed in 58% and 79% of tumors, respectively. ALK activation was significantly higher in tumors than in paired normal tissues, together with ALK and midkine expression. ALK activation was largely independent of mutations and correlated with midkine expression in tumors. ALK activation in tumors was associated with favorable features, including a younger age at diagnosis, hyperdiploidy, and detection by mass screening. Antitumor activity of the ALK inhibitor TAE684 was evaluated in wild-type or mutated ALK neuroblastoma cell lines and xenografts. TAE684 was cytotoxic in vitro in all cell lines, especially those harboring an ALK mutation. TAE684 efficiently inhibited ALK phosphorylation in vivo in both F1174I and R1275Q xenografts but demonstrated antitumor activity only against the R1275Q xenograft. In conclusion, ALK activation occurs frequently during neuroblastoma oncogenesis, mainly through mutation-independent mechanisms. However, ALK activation is not associated with a poor outcome and is not always a driver of cell proliferation and/or survival in neuroblastoma.

Nucleolin antagonist triggers autophagic cell death in human glioblastoma primary cells and decreased in vivo tumor growth in orthotopic brain tumor model

Nucleolin (NCL) is highly expressed in several types of cancer and represents an interesting therapeutic target. It is expressed at the plasma membrane of tumor cells, a property which is being used as a marker for several human cancer including glioblastoma. In this study we investigated targeting NCL as a new therapeutic strategy for the treatment of this pathology. To explore this possibility, we studied the effect of an antagonist of NCL, the multivalent pseudopeptide N6L using primary culture of human glioblastoma cells. In this system, N6L inhibits cell growth with different sensitivity depending to NCL localization. Cell cycle analysis indicated that N6L-induced growth reduction was due to a block of the G1/S transition with down-regulation of the expression of cyclin D1 and B2. By monitoring autophagy markers such as p62 and LC3II, we demonstrate that autophagy is enhanced after N6L treatment. In addition, N6L-treatment of mice bearing tumor decreased in vivo tumor growth in orthotopic brain tumor model and increase mice survival. The results obtained indicated an anti-proliferative and pro-autophagic effect of N6L and point towards its possible use as adjuvant agent to the standard therapeutic protocols presently utilized for glioblastoma.

Abstract A02: Nucleolin antagonist peptide N6L, normalizes tumor vasculature by decreasing Ang-2 secretion and inhibits pancreatic ductal adenocarcinoma growth and metastasis

Nucleolin (NCL) is a nucleolar protein regulating ribogenesis and cell cycle progression, and is overexpressed in tumor cells. Shuttling to the cell surface of tumor cells and tumor vessels NCL is a marker of tumor tissues and a target for cancer therapy. Recently, we developed a family of nucleolin antagonist pseudopeptides (NucANT). The N6L peptide, strongly inhibits human tumor growth by inducing apoptosis of tumor cells (1), and is currently in clinical trial for cancer. Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal human malignancies, and an explanation of the failure of treatments is that chemotherapies are poorly delivered to the tumor because of a deficient and pathologic vasculature. We investigated the possibility that N6L could dually target tumor cells and tumor vasculature and be a promising new option for the treatment of PDAC.

NCL targeting by N6L inhibited pancreatic tumor cell proliferation and pancreatic tumor cell motility similarly to other tumor cell types (1). Concerning endothelial cells (EC), N6L inhibited EC proliferation, motility, adhesion and tubulogenesis. We screened proteins involved in vascular stability and showed that N6L treatment or NCL depletion regulated the secretion of Ang-2. This N6L effect was specific of NCL targeting because NCL depletion rescued the inhibition of Ang-2 secretion induced by N6L.

We investigated the effect of N6L on the growth and metastasis of a PDAC orthotopic mouse model that was deficient in vasculature such as the human tumors and NCL was highly expressed in tumor ductal epithelial cells. We showed that N6L strongly inhibited the tumor growth by inhibiting NCL expression, tumor cell proliferation, and increasing tumor cell apoptosis. Coherently with the in vitro data, N6L decreased Ang-2 plasma concentration of PDAC mice. By characterizing the PDAC tumor vasculature after treatment, we demonstrated that N6L induced both vessel pruning and normalization of tumor vasculature by improving pericyte coverage and tumor blood vessel perfusion. Moreover, N6L-induced tumor vessel normalization was accompanied by an improved efficiency of chemotherapeutic drugs delivery to cancer tissues and an inhibition of liver metastasis incidence.

We conclude that NCL inhibition by N6L normalizes pancreatic tumor vasculature and suggest Ang-2 as a target and a biomarker of N6L response. N6L-induced PDAC vessel normalization promotes drug delivery and contributes to decrease metastasis formation.

1. Destouches D, et al. (2011) A simple approach to cancer therapy afforded by multivalent pseudopeptides that target cell-surface nucleoproteins. Cancer Res 71(9):3296-3305.

Citation Format: Maud-Emmanuelle Gilles, Federica Maione, Gilles Carpentier, damien Destouches, José Courty, Enrico Giraudo, Ilaria Cascone. Nucleolin antagonist peptide N6L, normalizes tumor vasculature by decreasing Ang-2 secretion and inhibits pancreatic ductal adenocarcinoma growth and metastasis. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Angiogenesis and Vascular Normalization: Bench to Bedside to Biomarkers; Mar 5-8, 2015; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl):Abstract nr A02.

Efficient treatment of breast cancer xenografts with multifunctionalized iron oxide nanoparticles combining magnetic hyperthermia and anti-cancer drug delivery

Introduction

Tumor cells can effectively be killed by heat, e.g. by using magnetic hyperthermia. The main challenge in the field, however, is the generation of therapeutic temperatures selectively in the whole tumor region. We aimed to improve magnetic hyperthermia of breast cancer by using innovative nanoparticles which display a high heating potential and are functionalized with a cell internalization and a chemotherapeutic agent to increase cell death.

Methods

The superparamagnetic iron oxide nanoparticles (MF66) were electrostatically functionalized with either Nucant multivalent pseudopeptide (N6L; MF66-N6L), doxorubicin (DOX; MF66-DOX) or both (MF66-N6LDOX). Their cytotoxic potential was assessed in a breast adenocarcinoma cell line MDA-MB-231. Therapeutic efficacy was analyzed on subcutaneous MDA-MB-231 tumor bearing female athymic nude mice.

Results

All nanoparticle variants showed an excellent heating potential around 500 W/g Fe in the alternating magnetic field (AMF, conditions: H = 15.4 kA/m, f = 435 kHz). We could show a gradual inter- and intracellular release of the ligands, and nanoparticle uptake in cells was increased by the N6L functionalization. MF66-DOX and MF66-N6LDOX in combination with hyperthermia were more cytotoxic to breast cancer cells than the respective free ligands. We observed a substantial tumor growth inhibition (to 40% of the initial tumor volume, complete tumor regression in many cases) after intratumoral injection of the nanoparticles in vivo. The proliferative activity of the remaining tumor tissue was distinctly reduced.

Conclusion

The therapeutic effects of breast cancer magnetic hyperthermia could be strongly enhanced by the combination of MF66 functionalized with N6L and DOX and magnetic hyperthermia. Our approach combines two ways of tumor cell killing (magnetic hyperthermia and chemotherapy) and represents a straightforward strategy for translation into the clinical practice when injecting nanoparticles intratumorally.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-015-0576-1) contains supplementary material, which is available to authorized users.

Proliferation and migration activities of fibroblast growth factor-2 in endothelial cells are modulated by its direct interaction with heparin affin regulatory peptide

Angiogenesis is the physiological process involving the growth of new blood vessels from pre-existing vessels. In normal or pathological angiogenesis, angiogenic growth factors activate cognate receptors on endothelial cells. Fibroblast growth factor-2 (FGF-2) and heparin affin regulatory peptide (HARP) are two heparin-binding growth factors and were described for their pro-angiogenic properties on human umbilical endothelial cells (HUVEC). We now show that HARP acts as a mediator of FGF-2's stimulatory effects, since it is able to inhibit the proliferation and migration of HUVEC induced by FGF-2. We demonstrate by ELISA and optical biosensor binding assay that HARP and FGF-2 interact through direct binding. We have adapted a previously developed structural proteomics method for the identification of residues involved in protein-protein interactions. Application of this method showed that two sequences in HARP were involved in binding FGF-2. One was in the C-thrombospondin type 1 repeat (C-TSR-1) domain and the other in the C-terminal domain of HARP. The identification of these regions as mediating the binding of FGF-2 was confirmed by ELISA using synthetic peptides, which are as well mediators of FGF-2-induced proliferation, migration and tubes formation on HUVEC in vitro. These results imply that besides a regulation of the proliferation, migration and angiogenesis of HUVEC by direct interaction of FGF-2 with its receptors, an alternative pathway exists involving its binding to growth factors such as HARP.

Glycosaminoglycan mimetic associated to human mesenchymal stem cell-based scaffolds inhibit ectopic bone formation, but induce angiogenesis in vivo

Tissue engineering approaches to stimulate bone formation currently combine bioactive scaffolds with osteocompetent human mesenchymal stem cells (hMSC). Moreover, osteogenic and angiogenic factors are required to promote differentiation and survival of hMSC through improved vascularization through the damaged extracellular matrix (ECM). Glycosaminoglycans (GAGs) are ECM compounds acting as modulators of heparin-binding protein activities during bone development and regenerative processes. GAG mimetics have been proposed as ECM stabilizers and were previously described for their positive effects on bone formation and angiogenesis after local treatment. Here, we developed a strategy associating the GAG mimetic [OTR4120] with bone substitutes to optimize stem cell-based therapeutic products. We showed that [OTR4120] was able to potentiate proliferation, migration, and osteogenic differentiation of hMSC in vitro. Its link to tricalcium phosphate/hydroxyapatite scaffolds improved their colonization by hMSC. Surprisingly, when these combinations were tested in an ectopic model of bone formation in immunodeficient mice, the GAG mimetics inhibit bone formation induced by hMSC and promoted an osteoclastic activity. Moreover, the inflammatory response was modulated, and the peri-implant vascularization stimulated. All together, these findings further support the ability of GAG mimetics to organize the local ECM to coordinate the host response toward the implanted biomaterial, and to inhibit the abnormal bone formation process on a subcutaneous ectopic site.

Pleiotrophin promotes capillary-like sprouting from senescent aortic rings

BACKGROUND

Pleiotrophin (PTN) is a heparin-binding growth factor involved in angiogenesis during development and tumor growth. Plasmid therapy with PTN also induces angiogenesis after myocardial infarction. During aging, angiogenesis is impaired and we therefore examined whether a growth factor therapy with PTN is able to restore neovascularization.

METHODS

We evaluated the PTN effects on capillary-like endothelial sprouting in adult (n = 10) and senescent (n = 10) rats, using an ex vivo model of explanted aortic segments in culture. Freshly cut thoracic aortic rings from 3 and 24 month old (mo) rats (both n = 12) were cultured in a 3-dimensional collagen matrix with or without addition of recombinant human PTN (2.5-250 ng/ml) or Vascular Endothelial Growth Factor-165 (VEGF) (1-100 ng/ml) and the length of developed capillary network was quantified at day 3 and 6 by image analysis.

RESULTS

After 6 days of culture, capillary-like tube formation was lower in control conditions in 24 mo aortic rings than in 3 mo rings. Addition of PTN increased dose-dependently the length of capillary-like tube formation in both 3 and 24 mo rings (P < 0.001 and P < 0.001 respectively). Age-associated impairment of capillary-like tube formation had been successfully restored in senescent aortic segments by PTN treatment. PTN induced development of capillary network similar to that observed with VEGF therapy with doses equal or superior to 10 ng/ml.

CONCLUSION

PTN is able to induce ex vivo angiogenesis during aging and might be a new promising therapy to induce neovascularization in aged tissues as well as after age-associated cardiac, hindlimb or cerebral ischemia.

Expression of the growth factor pleiotrophin and its receptor protein tyrosine phosphatase beta/zeta in the serum, cartilage and subchondral bone of patients with osteoarthritis

OBJECTIVES

Pleiotrophin is a heparin-binding growth factor expressed in embryonic but not mature cartilage, suggesting a role in cartilage development. Elucidation of the molecular changes observed during the remodelling process in osteoarthritis is of paramount importance. This study aimed to investigate serum pleiotrophin levels and expression of pleiotrophin and its receptor protein tyrosine phosphatase beta/zeta in the cartilage and subchondral bone of osteoarthritis patients.

METHODS

Serum samples derived from 16 osteoarthritis patients and 18 healthy donors. Pleiotrophin and receptor protein tyrosine phosphatase beta/zeta in the cartilage and subchondral bone were studied in 29 patients who had undergone total knee or hip replacement for primary osteoarthritis and in 10 control patients without macroscopic osteoarthritis changes.

RESULTS

Serum pleiotrophin levels and expression of pleiotrophin in chondrocytes and subchondral bone osteocytes significantly increased in osteoarthritis patients graded Ahlback II to III. Receptor protein tyrosine phosphatase beta/zeta was mainly detected in the subchondral bone osteocytes of patients with moderate osteoarthritis and as disease severity increased, in the osteocytes and bone lining cells of the distant trabeculae.

CONCLUSIONS

These data render pleiotrophin and receptor protein tyrosine phosphatase beta/zeta promising candidates for further studies towards developing targeted therapeutic schemes for osteoarthritis.

Interplay between αvβ3 integrin and nucleolin regulates human endothelial and glioma cell migration

The multifunctional protein nucleolin (NCL) is overexpressed on the surface of activated endothelial and tumor cells and mediates the stimulatory actions of several angiogenic growth factors, such as pleiotrophin (PTN). Because α(v)β(3) integrin is also required for PTN-induced cell migration, the aim of the present work was to study the interplay between NCL and α(v)β(3) by using biochemical, immunofluorescence, and proximity ligation assays in cells with genetically altered expression of the studied molecules. Interestingly, cell surface NCL localization was detected only in cells expressing α(v)β(3) and depended on the phosphorylation of β(3) at Tyr(773) through receptor protein-tyrosine phosphatase β/ζ (RPTPβ/ζ) and c-Src activation. Downstream of α(v)β(3,) PI3K activity mediated this phenomenon and cell surface NCL was found to interact with both α(v)β(3) and RPTPβ/ζ. Positive correlation of cell surface NCL and α(v)β(3) expression was also observed in human glioblastoma tissue arrays, and inhibition of cell migration by cell surface NCL antagonists was observed only in cells expressing α(v)β(3). Collectively, these data suggest that both expression and β(3) integrin phosphorylation at Tyr(773) determine the cell surface localization of NCL downstream of the RPTPβ/ζ/c-Src signaling cascade and can be used as a biomarker for the use of cell surface NCL antagonists as anticancer agents.

Multivalent pseudopeptides targeting cell surface nucleoproteins inhibit cancer cell invasion through tissue inhibitor of metalloproteinases 3 (TIMP-3) release

Blockage of the metastasis process remains a significant clinical challenge, requiring innovative therapeutic approaches. For this purpose, molecules that inhibit matrix metalloproteinases activity or induce the expression of their natural inhibitor, the tissue inhibitor of metalloproteinases (TIMPs), are potentially interesting. In a previous study, we have shown that synthetic ligands binding to cell surface nucleolin/nucleophosmin and known as HB 19 for the lead compound and NucAnt 6L (N6L) for the most potent analog, inhibit both tumor growth and angiogenesis. Furthermore, they prevent metastasis in a RET transgenic mice model which develops melanoma. Here, we investigated the effect of N6L on the invasion capacity of MDA-MB-435 melanoma cells. Our results show that the multivalent pseudopeptide N6L inhibited Matrigel invasion of MDA-MB-435 cells in a modified Boyden chamber model. This was associated with an increase in TIMP-3 in the cell culture medium without a change in TIMP-3 mRNA expression suggesting its release from cell surface and/or extracellular matrix. This may be explained by our demonstrated N6L interaction with sulfated glycosaminoglycans and consequently the controlled bioavailability of glycosaminoglycan-bound TIMP-3. The implication of TIMP-3 in N6L-induced inhibition of cell invasion was evidenced by siRNA silencing experiments showing that the loss of TIMP-3 expression abrogated the effect of N6L. The inhibition of tumor cell invasion by N6L demonstrated in this study, in addition to its previously established inhibitory effect on tumor growth and angiogenesis, suggests that N6L represents a promising anticancer drug candidate warranting further investigation.

Antitumor and angiostatic activities of the antimicrobial peptide dermaseptin B2

Recently, we have found that the skin secretions of the Amazonian tree frog Phyllomedusa bicolor contains molecules with antitumor and angiostatic activities and identified one of them as the antimicrobial peptide dermaseptin (Drs) B2. In the present study we further explored the in vitro and in vivo antitumor activity of this molecule and investigated its mechanism of action. We showed that Drs B2 inhibits the proliferation and colony formation of various human tumor cell types, and the proliferation and capillary formation of endothelial cells in vitro. Furthermore, Drs B2 inhibited tumor growth of the human prostate adenocarcinoma cell line PC3 in a xenograft model in vivo. Research on the mechanism of action of Drs B2 on tumor PC3 cells demonstrated a rapid increasing amount of cytosolic lactate dehydrogenase, no activation of caspase-3, and no changes in mitochondrial membrane potential. Confocal microscopy analysis revealed that Drs B2 can interact with the tumor cell surface, aggregate and penetrate the cells. These data together indicate that Drs B2 does not act by apoptosis but possibly by necrosis. In conclusion, Drs B2 could be considered as an interesting and promising pharmacological and therapeutic leader molecule for the treatment of cancer.

Modulation of inflammation by Cicaderma ointment accelerates skin wound healing

Skin wound healing is a natural and intricate process that takes place after injury, involving different sequential phases such as hemostasis, inflammatory phase, proliferative phase, and remodeling that are associated with complex biochemical events. The interruption or failure of wound healing leads to chronic nonhealing wounds or fibrosis-associated diseases constituting a major health problem where, unfortunately, medicines are not very effective. The objective of this study was to evaluate the capacity of Cicaderma ointment (Boiron, Lyon, France) to accelerate ulcer closure without fibrosis and investigate wound healing dynamic processes. We used a necrotic ulcer model in mice induced by intradermal doxorubicin injection, and after 11 days, when the ulcer area was maximal, we applied Vaseline petroleum jelly or Cicaderma every 2 days. Topical application of Cicaderma allowed a rapid recovery of mature epidermal structure, a more compact and organized dermis and collagen bundles compared with the Vaseline group. Furthermore, the expression of numerous cytokines/molecules in the ulcer was increased 11 days after doxorubicin injection compared with healthy skin. Cicaderma rapidly reduced the level of proinflammatory cytokines, mainly tumor necrosis factor (TNF)-α and others of the TNF pathway, which can be correlated to a decrease of polymorphonuclear recruitment. It is noteworthy that the modulation of inflammation through TNF-α, macrophage inflammatory protein-1α, interleukin (IL)-12, IL-4, and macrophage-colony-stimulating factor was maintained 9 days after the first ointment application, facilitating the wound closure without affecting angiogenesis. These cytokines seem to be potential targets for therapeutic approaches in chronic wounds. Our results confirm the use of Cicaderma for accelerating skin wound healing and open new avenues for sequential treatments to improve healing.

Alterations of overused supraspinatus tendon: a possible role of glycosaminoglycans and HARP/pleiotrophin in early tendon pathology

Supraspinatus tendon overuse injuries lead to significant pain and disability in athletes and workers. Despite the prevalence and high social cost of these injuries, the early pathological events are not well known. We analyzed the potential relation between glycosaminoglycan (GAG) composition and phenotypic cellular alteration using a rat model of rotator cuff overuse. Total sulfated GAGs increased after 4 weeks of overuse and remained elevated up to 16 weeks. GAG accumulation was preceded by up-regulation of decorin, versican, and aggrecan proteoglycans (PGs) mRNAs and proteins and biglycan PG mRNA after 2 weeks. At 2 weeks, collagen 1 transcript decreased whereas mRNAs for collagen 2, collagen 3, collagen 6, and the transcription factor Sox9 were increased. Protein levels of heparin affine regulatory peptide (HARP)/pleiotrophin, a cytokine known to regulate developmental chondrocyte formation, were enhanced especially at 4 weeks, without up-regulation of HARP/pleiotrophin mRNA. Further results suggest that the increased GAGs present in early lesions may sequester HARP/pleiotrophin, which could contribute to a loss of tenocyte's phenotype. All these modifications are characteristic of a shift towards the chondrocyte phenotype. Identification of these early changes in the extra-cellular matrix may help to prevent the progression of the pathology to more disabling, degenerative alterations.

Pleiotrophin over-expression provides trophic support to dopaminergic neurons in parkinsonian rats

Background

Pleiotrophin is known to promote the survival and differentiation of dopaminergic neurons in vitro and is up-regulated in the substantia nigra of Parkinson's disease patients. To establish whether pleiotrophin has a trophic effect on nigrostriatal dopaminergic neurons in vivo, we injected a recombinant adenovirus expressing pleiotrophin in the substantia nigra of 6-hydroxydopamine lesioned rats.

Results

The viral vector induced pleiotrophin over-expression by astrocytes in the substantia nigra pars compacta, without modifying endogenous neuronal expression. The percentage of tyrosine hydroxylase-immunoreactive cells as well as the area of their projections in the lesioned striatum was higher in pleiotrophin-treated animals than in controls.

Conclusions

These results indicate that pleiotrophin over-expression partially rescues tyrosine hydroxylase-immunoreactive cell bodies and terminals of dopaminergic neurons undergoing 6-hydroxydopamine-induced degeneration.

The synthetic peptide P111-136 derived from the C-terminal domain of heparin affin regulatory peptide inhibits tumour growth of prostate cancer PC-3 cells

Background

Heparin affin regulatory peptide (HARP), also called pleiotrophin, is a heparin-binding, secreted factor that is overexpressed in several tumours and associated to tumour growth, angiogenesis and metastasis. The C-terminus part of HARP composed of amino acids 111 to 136 is particularly involved in its biological activities and we previously established that a synthetic peptide composed of the same amino acids (P111-136) was capable of inhibiting the biological activities of HARP. Here we evaluate the ability of P111-136 to inhibit in vitro and in vivo the growth of a human tumour cell line PC-3 which possess an HARP autocrine loop.

Methods

A total lysate of PC-3 cells was incubated with biotinylated P111-136 and pulled down for the presence of the HARP receptors in Western blot. In vitro, the P111-136 effect on HARP autocrine loop in PC-3 cells was determined by colony formation in soft agar. In vivo, PC-3 cells were inoculated in the flank of athymic nude mice. Animals were treated with P111-136 (5 mg/kg/day) for 25 days. Tumour volume was evaluated during the treatment. After the animal sacrifice, the tumour apoptosis and associated angiogenesis were evaluated by immunohistochemistry. In vivo anti-angiogenic effect was confirmed using a mouse Matrigel™ plug assay.

Results

Using pull down experiments, we identified the HARP receptors RPTPβ/ζ, ALK and nucleolin as P111-136 binding proteins. In vitro, P111-136 inhibits dose-dependently PC-3 cell colony formation. Treatment with P111-136 inhibits significantly the PC-3 tumour growth in the xenograft model as well as tumour angiogenesis. The angiostatic effect of P111-136 on HARP was also confirmed using an in vivo Matrigel™ plug assay in mice

Conclusions

Our results demonstrate that P111-136 strongly inhibits the mitogenic effect of HARP on in vitro and in vivo growth of PC-3 cells. This inhibition could be linked to a direct or indirect binding of this peptide to the HARP receptors (ALK, RPTPβ/ζ, nucleolin). In vivo, the P111-136 treatment significantly inhibits both the PC-3 tumour growth and the associated angiogenesis. Thus, P111-136 may be considered as an interesting pharmacological tool to interfere with tumour growth that has now to be evaluated in other cancer types.

A simple approach to cancer therapy afforded by multivalent pseudopeptides that target cell-surface nucleoproteins

Recent studies have implicated the involvement of cell surface forms of nucleolin in tumor growth. In this study, we investigated whether a synthetic ligand of cell-surface nucleolin known as N6L could exert antitumor activity. We found that N6L inhibits the anchorage-dependent and independent growth of tumor cell lines and that it also hampers angiogenesis. Additionally, we found that N6L is a proapoptotic molecule that increases Annexin V staining and caspase-3/7 activity in vitro and DNA fragmentation in vivo. Through affinity isolation experiments and mass-spectrometry analysis, we also identified nucleophosmin as a new N6L target. Notably, in mouse xenograft models, N6L administration inhibited human tumor growth. Biodistribution studies carried out in tumor-bearing mice indicated that following administration N6L rapidly localizes to tumor tissue, consistent with its observed antitumor effects. Our findings define N6L as a novel anticancer drug candidate warranting further investigation.

HARPΔ111-136 enhances radiation-induced apoptosis of U87MG glioblastoma by induction of the proapoptotic protein CHOP

We previously demonstrated, using the glioblastoma cell line U87MG as an experimental model, that the adenoviral mediated overexpression of the truncated protein HARPΔ111-136 inhibits the proliferation of these cells in vitro as well as tumor growth and angiogenesis in vivo. This study focused on identifying the underlying mechanisms for the observed antitumoral effect. The present study demonstrated that HARPΔ111-136 induced the ATF4/ATF3/CHOP cascade resulting in a strong expression of the proapoptotic protein CHOP, leading to tumor cell apoptosis as demonstrated by PARP cleavage and FACS analysis. siRNA-mediated CHOP gene silencing abolished Ad-HARPΔ111-136 induced apoptosis. Moreover, Ad-HARPΔ111-136 increased the expression of the death receptor DR5 and enhanced U87MG cells sensitivity in vitro to TRAIL a DR5 ligand with subsequent activation of caspase 8. Infection of U87MG cells with Ad-HARPΔ111-136 also enhanced radiation-induced apoptosis. In vivo, the combination of Ad-HARPΔ111-136 and radiation therapy resulted in a striking inhibition (92%) of the growth of U87MG xenografts, resulting from the potent effect on tumor angiogenesis and tumor cell apoptosis as determined by TUNEL analysis. Taken together, our results indicated that the inhibitor HARPΔ111-136 sensitized U87MG cells to apoptosis.

Antitumor and angiostatic peptides from frog skin secretions

The discovery of new molecules with potential antitumor activity continues to be of great importance in cancer research. In this respect, natural antimicrobial peptides isolated from various animal species including humans and amphibians have been found to be of particular interest. Here, we report the presence of two anti-proliferative peptides active against cancer cells in the skin secretions of the South American tree frog, Phyllomedusa bicolor. The crude skin exudate was fractioned by size exclusion gel followed by reverse-phase HPLC chromatography. After these two purification steps, we identified two fractions that exhibited anti-proliferative activity. Sequence analysis indicated that this activity was due to two antimicrobial α-helical cationic peptides of the dermaseptin family (dermaseptins B2 and B3). This result was confirmed using synthetic dermaseptins. When tested in vitro, synthetic B2 and B3 dermaseptins inhibited the proliferation of the human prostatic adenocarcinoma PC-3 cell line by more than 90%, with an EC(50) of around 2-3 μM. No effect was observed on the growth of the NIH-3T3 non-tumor mouse cell line with Drs B2, whereas a slight inhibiting effect was observed with Drs B3 at high dose. In addition, the two fractions obtained after size exclusion chromatography also inhibited PC-3 cell colony formation in soft agar. Interestingly, inhibition of the proliferation and differentiation of activated adult bovine aortic endothelial cells was observed in cells treated with these two fractions. Dermaseptins B2 and B3 could, therefore, represent interesting new pharmacological molecules with antitumor and angiostatic properties for the development of a new class of anticancer drugs.

Intramyocardial protein therapy with vascular endothelial growth factor (VEGF-165) induces functional angiogenesis in rat senescent myocardium

Myocardial capillary density and angiogenesis are impaired during aging but whether growth factor therapy is able to induce functional neovascularization in senescent heart have never been studied. In 3, 24, 28 and 32 mo male Wistar rats, cardiac hemodynamic measurements indicated heart failure at 28 and 32 mo, associated with left ventricular hypertrophy. VEGF/VEGF-R2, Ang-1/Ang-2/Tie-2 and PTN levels, quantitated in left ventricle by western blotting and immunohistochemistry, showed that VEGF and VEGF-R2 levels were specifically decreased during aging. In vitro angiogenesis ± rhVEGF-165 (5 and 50 ng/mL) was measured in aortic segments in 3D-collagen. Aortic sprouting was decreased during aging but restored by VEGF treatment (P<0.001), similarly in 3 and 24 mo with 50 ng/mLVEGF. Finally, 3 and 24 mo rats were submitted to in vivo intramyocardial rhVEGF-165 (10 micrograms) or saline solution injection and angiogenesis was measured by SPECT imaging of the alpha(v)beta(3) integrin-targeted tracer (99m)Tc-RAFT-RGD, capillary fluorescence staining in isolated perfused heart and vWF and alpha smooth muscle actin immunohistochemistry, 7 and 21 days later. VEGF administration increased capillary density in 3 but also in 24 mo rats at days 7 (+26%, P<0.01) and 21 (+41%, P<0.01) and arteriolar density at day 21 (+36%, P<0.01). Activity of (99m)Tc-RAFT-RGD and capillary fluorescence labeling indicated that new formed capillaries were functional. Cardiac aging was associated with strong VEGF/VEGF-R2 pathway downregulation. VEGF-165 protein therapy was able to induce in vitro and in vivo angiogenesis during aging. In 24 mo hearts, in vivo angiogenesis was functional, sustained and comparable to neovascularization observed in 3 mo hearts.

Localization of butyrylcholinesterase at the neuromuscular junction of normal and acetylcholinesterase knockout mice

At the mouse neuromuscular junction (NMJ), there are two distinct cholinesterases (ChE): acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Until now, it has been difficult to determine the precise localization of BChE at the NMJ. In this study, we use a modification of Koelle's method to stain AChE and BChE activity. This method does not interfere with fluorescent co-staining, which allows precise co-localization of ChE and other synaptic molecules at the NMJ. We demonstrate that AChE and BChE exhibit different localization patterns at the mouse NMJ. AChE activity is present both in the primary cleft and in the secondary folds, whereas BChE activity appears to be almost absent in the primary cleft and to be concentrated in subsynaptic folds. The same localization for BChE is observed in the AChE-knockout (KO) mouse NMJ. Collagenase treatment removed AChE from the primary cleft, but not from secondary folds in the wild-type mouse, whereas in the AChE-KO mouse, BChE remains in the secondary folds. After peripheral nerve injury and regeneration, BChE localization is not modified in either normal or KO mice. In conclusion, specific localization of BChE in the secondary folds of the NMJ suggests that this enzyme is not a strict surrogate of AChE and that the two enzymes have two different roles.

A Pleiotrophin C-terminus peptide induces anti-cancer effects through RPTPβ/ζ

BACKGROUND

Pleiotrophin, also known as HARP (Heparin Affin Regulatory Peptide) is a growth factor expressed in various tissues and cell lines. Pleiotrophin participates in multiple biological actions including the induction of cellular proliferation, migration and angiogenesis, and is involved in carcinogenesis. Recently, we identified and characterized several pleiotrophin proteolytic fragments with biological activities similar or opposite to that of pleiotrophin. Here, we investigated the biological actions of P(122-131), a synthetic peptide corresponding to the carboxy terminal region of this growth factor.

RESULTS

Our results show that P(122-131) inhibits in vitro adhesion, anchorage-independent proliferation, and migration of DU145 and LNCaP cells, which express pleiotrophin and its receptor RPTPβ/ζ. In addition, P(122-131) inhibits angiogenesis in vivo, as determined by the chicken embryo CAM assay. Investigation of the transduction mechanisms revealed that P(122-131) reduces the phosphorylation levels of Src, Pten, Fak, and Erk1/2. Finally, P(122-131) not only interacts with RPTPβ/ζ, but also interferes with other pleiotrophin receptors, as demonstrated by selective knockdown of pleiotrophin or RPTPβ/ζ expression with the RNAi technology.

CONCLUSIONS

In conclusion, our results demonstrate that P(122-131) inhibits biological activities that are related to the induction of a transformed phenotype in PCa cells, by interacing with RPTPβ/ζ and interfering with other pleiotrophin receptors. Cumulatively, these results indicate that P(122-131) may be a potential anticancer agent, and they warrant further study of this peptide.

Targeting surface nucleolin with a multivalent pseudopeptide delays development of spontaneous melanoma in RET transgenic mice

BACKGROUND

The importance of cell-surface nucleolin in cancer biology was recently highlighted by studies showing that ligands of nucleolin play critical role in tumorigenesis and angiogenesis. By using a specific antagonist that binds the C-terminal tail of nucleolin, the HB-19 pseudopeptide, we recently reported that HB-19 treatment markedly suppressed the progression of established human breast tumor cell xenografts in the athymic nude mice without apparent toxicity.

METHODS

The in vivo antitumoral action of HB-19 treatment was assessed on the spontaneous development of melanoma in the RET transgenic mouse model. Ten days old RET mice were treated with HB-19 in a prophylactic setting that extended 300 days. In parallel, the molecular basis for the action of HB-19 was investigated on a melanoma cell line (called TIII) derived from a cutaneous nodule of a RET mouse.

RESULTS

HB-19 treatment of RET mice caused a significant delay in the onset of cutaneous tumors, several-months delay in the incidence of large tumors, a lower frequency of cutaneous nodules, and a reduction of visceral metastatic nodules while displaying no toxicity to normal tissue. Moreover, microvessel density was significantly reduced in tumors recovered from HB-19 treated mice compared to corresponding controls. Studies on the melanoma-derived tumor cells demonstrated that HB-19 treatment of TIII cells could restore contact inhibition, impair anchorage-independent growth, and reduce their tumorigenic potential in mice. Moreover, HB-19 treatment caused selective down regulation of transcripts coding matrix metalloproteinase 2 and 9, and tumor necrosis factor-alpha in the TIII cells and in melanoma tumors of RET mice.

CONCLUSIONS

Although HB-19 treatment failed to prevent the development of spontaneous melanoma in the RET mice, it delayed for several months the onset and frequency of cutaneous tumors, and exerted a significant inhibitory effect on visceral metastasis. Consequently, HB-19 could provide a novel therapeutic agent by itself or as an adjuvant therapy in association with current therapeutic interventions on a virulent cancer like melanoma.