Heat shock cognate 70 regulates the translocation and angiogenic function of nucleolin

IL-28A/IL-10Rβ axis promotes angiogenesis via eNOS/AKT signaling and AP-1/NF-κB/MMP-2 network by regulating HSP70-1 expression

INTRODUCTION

Angiogenesis plays a significant role in the development of tumor progression and inflammatory diseases. The role of IL-28A in angiogenesis and its precise regulatory mechanisms remain rarely elucidated.

OBJECTIVES

We report the novel regulatory role of IL-28A in physiological angiogenesis. The study aimed to elucidate the regulatory mechanisms involved in IL-28A-mediated angiogenesis and identify key genes associated with IL-28A-induced angiogenic responses.

METHODS

To know the effect of IL-28A on angiogenesis, HUVECs were applied to perform proliferation, migration, invasion, tube formation, immunoblot, and EMSA. Gene expression changes in HUVECs following IL-28A treatment were analyzed by NGS. The functional role of HSP70-1 and IL-10Rβ in IL-28A-induced angiogenic responses was evaluated using PCR and siRNA knockdown. Animal studies were conducted by aortic ring ex vivo assays, Matrigel plug in vivo assays, and immunochemistry using HSP70-1 knockout and transgenic mice models. The efficacy of IL-28A in angiogenesis was confirmed in a hind-limb ischemia model.

RESULTS

Autocrine/paracrine actions in HUVECs regulated IL-28A protein expression. Exogenous IL-28A increased the proliferation of HUVECs via eNOS/AKT and ERK1/2 signaling. IL-28A treatment promoted migration, invasion, and capillary tube formation of HUVECs through induction of the AP-1/NF-κB/MMP-2 network, which was associated with eNOS/AKT and ERK1/2 signaling. The efficacy of IL-28A-induced angiogenic potential was confirmed by aortic ring and Matrigel plug assay. HSP70-1 was identified as an IL-28A-mediated angiogenic effector gene using bioinformatics. Knockdown of HSP70-1 abolished angiogenic responses and eNOS/AKT signaling in IL-28A-treated HUVECs. IL-28A-induced microvessel sprouting formation was testified in HSP70-1-deficient and HSP70-1 transgenic mice. Flow recovery in hind-limb ischemia mice was accelerated by IL-28A injection. Finally, ablation of the IL-10Rβ gene impeded the angiogenic responses and eNOS/AKT signaling stimulated by IL-28A in HUVECs.

CONCLUSION

HSP70-1 drives the progression of angiogenesis by the IL-28A/IL-10Rβ axis via eNOS/AKT signaling and the AP-1/NF-κB/MMP-2 network.

Rapid liposomal formulation for nucleolin targeting to rhabdomyosarcoma cells

Rhabdomyosarcoma (RMS) is the most common pediatric soft tissue sarcoma. More effective and less toxic therapies are urgently needed for high-risk patients. Peptide-guided targeted drug delivery can increase the therapeutic index of encapsulated drugs and improve patients' well-being. To apply this strategy to RMS, we identified the peptide F3 in a screening for peptides binding to RMS cells surface. F3 binds to nucleolin, which is present on the surface of RMS cells and is abundantly expressed at the mRNA level in RMS patients' biopsies compared to healthy tissues. We developed a rapid microfluidic formulation of F3-decorated PEGylated liposomes and remote loading of the chemotherapeutic drug vincristine. Size, surface charge, drug loading and retention of targeted and control liposomes were studied. Enhanced cellular binding and uptake were observed in three different nucleolin-positive RMS cell lines. Importantly, F3-functionalized liposomes loaded with vincristine were up to 11 times more cytotoxic than non-targeted liposomes for RMS cell lines. These results demonstrate that F3-functionalized liposomes are promising for targeted drug delivery to RMS and warrant further in vivo investigations.

RNA-Binding Proteins in Bladder Cancer

RNA-binding proteins (RBPs) are key regulators of transcription and translation, with highly dynamic spatio-temporal regulation. They are usually involved in the regulation of RNA splicing, polyadenylation, and mRNA stability and mediate processes such as mRNA localization and translation, thereby affecting the RNA life cycle and causing the production of abnormal protein phenotypes that lead to tumorigenesis and development. Accumulating evidence supports that RBPs play critical roles in vital life processes, such as bladder cancer initiation, progression, metastasis, and drug resistance. Uncovering the regulatory mechanisms of RBPs in bladder cancer is aimed at addressing the occurrence and progression of bladder cancer and finding new therapies for cancer treatment. This article reviews the effects and mechanisms of several RBPs on bladder cancer and summarizes the different types of RBPs involved in the progression of bladder cancer and the potential molecular mechanisms by which they are regulated, with a view to providing information for basic and clinical researchers.

Quantum Dot-Based Screening Identifies F3 Peptide and Reveals Cell Surface Nucleolin as a Therapeutic Target for Rhabdomyosarcoma

Active drug delivery by tumor-targeting peptides is a promising approach to improve existing therapies for rhabdomyosarcoma (RMS), by increasing the therapeutic effect and decreasing the systemic toxicity, e.g., by drug-loaded peptide-targeted nanoparticles. Here, we tested 20 different tumor-targeting peptides for their ability to bind to two RMS cell lines, Rh30 and RD, using quantum dots Streptavidin and biotin-peptides conjugates as a model for nanoparticles. Four peptides revealed a very strong binding to RMS cells: NCAM-1-targeting NTP peptide, nucleolin-targeting F3 peptide, and two Furin-targeting peptides, TmR and shTmR. F3 peptide showed the strongest binding to all RMS cell lines tested, low binding to normal control myoblasts and fibroblasts, and efficient internalization into RMS cells demonstrated by the cytoplasmic delivery of the Saporin toxin. The expression of the nucleophosphoprotein nucleolin, the target of F3, on the surface of RMS cell lines was validated by competition with the natural ligand lactoferrin, by colocalization with the nucleolin-binding aptamer AS1411, and by the marked sensitivity of RMS cell lines to the growth inhibitory nucleolin-binding N6L pseudopeptide. Taken together, our results indicate that nucleolin-targeting by F3 peptide represents a potential therapeutic approach for RMS.

Nucleolin: a cell portal for viruses, bacteria, and toxins

The main localization of nucleolin is the nucleolus, but this protein is present in multiple subcellular sites, and it is unconventionally secreted. On the cell surface, nucleolin acts as a receptor for various viruses, some bacteria, and some toxins. Aim of this review is to discuss the characteristics that make nucleolin able to act as receptor or co-receptor of so many and different pathogens. The important features that emerge are its multivalence, and its role as a bridge between the cell surface and the nucleus. Multiple domains, short linear motifs and post-translational modifications confer and modulate nucleolin ability to interact with nucleic acids, with proteins, but also with carbohydrates and lipids. This modular multivalence allows nucleolin to participate in different types of biomolecular condensates and to move to various subcellular locations, where it can act as a kind of molecular glue. It moves from the nucleus to the cell surface and can accompany particles in the reverse direction, from the cell surface into the nucleus, which is the destination of several pathogens to manipulate the cell in their favour.

HSP70 and HSP90 in Cancer: Cytosolic, Endoplasmic Reticulum and Mitochondrial Chaperones of Tumorigenesis

HSP70 and HSP90 are two powerful chaperone machineries involved in survival and proliferation of tumor cells. Residing in various cellular compartments, HSP70 and HSP90 perform specific functions. Concurrently, HSP70 and HSP90 homologs may also translocate from their primary site under various stress conditions. Herein, we address the current literature on the role of HSP70 and HSP90 chaperone networks in cancer. The goal is to provide a comprehensive review on the functions of cytosolic, mitochondrial and endoplasmic reticulum HSP70 and HSP90 homologs in cancer. Given that high expression of HSP70 and HSP90 enhances tumor development and associates with tumor aggressiveness, further understanding of HSP70 and HSP90 chaperone networks may provide clues for the discoveries of novel anti-cancer therapies.

The GAR/RGG motif defines a family of nuclear alarmins

The nucleus is the target of autoantibodies in many diseases, which suggests intrinsic nuclear adjuvants that confer its high autoimmunogenicity. Nucleolin (NCL) is one abundant nucleolar autoantigen in systemic lupus erythematosus (SLE) patients and, in lupus-prone mice, it elicits autoantibodies early. With purified NCL, we observed that it was a potent alarmin that activated monocytes, macrophages and dendritic cells and it was a ligand for TLR2 and TLR4. NCL released by necrotic cells also exhibited alarmin activity. The NCL alarmin activity resides in its glycine/arginine-rich (GAR/RGG) motif and can be displayed by synthetic GAR/RGG peptides. Two more GAR/RGG-containing nucleolar proteins, fibrillarin (FBRL) and GAR1, were also confirmed to be novel alarmins. Therefore, the GAR/RGG alarmin motif predicts a family of nucleolar alarmins. The apparent prevalence of nucleolar alarmins suggests their positive contribution to tissue homeostasis by inducing self-limiting tissue inflammation with autoimmunity only occurring when surveillance is broken down.

Endothelial angiogenic activity and adipose angiogenesis is controlled by extracellular matrix protein TGFBI

Several studies have suggested that extracellular matrix (ECM) remodeling and the microenvironment are tightly associated with adipogenesis and adipose angiogenesis. In the present study, we demonstrated that transforming growth factor-beta induced (TGFBI) suppresses angiogenesis stimulated by adipocyte-conditioned medium (Ad-CM), both in vitro and in vivo. TGFBI knockout (KO) mice exhibited increased numbers of blood vessels in adipose tissue, and blood vessels from these mice showed enhanced infiltration into Matrigel containing Ad-CM. The treatment of Ad-CM-stimulated SVEC-10 endothelial cells with TGFBI protein reduced migration and tube-forming activity. TGFBI protein suppressed the activation of the Src and extracellular signaling-related kinase signaling pathways of these SVEC-10 endothelial cells. Our findings indicated that TGFBI inhibited adipose angiogenesis by suppressing the activation of Src and ERK signaling pathways, possibly because of the stimulation of the angiogenic activity of endothelial cells.

Cancer Stem Cells and Nucleolin as Drivers of Carcinogenesis

Cancer, one of the most mortal diseases worldwide, is characterized by the gain of specific features and cellular heterogeneity. Clonal evolution is an established theory to explain heterogeneity, but the discovery of cancer stem cells expanded the concept to include the hierarchical growth and plasticity of cancer cells. The activation of epithelial-to-mesenchymal transition and its molecular players are widely correlated with the presence of cancer stem cells in tumors. Moreover, the acquisition of certain oncological features may be partially attributed to alterations in the levels, location or function of nucleolin, a multifunctional protein involved in several cellular processes. This review aims at integrating the established hallmarks of cancer with the plasticity of cancer cells as an emerging hallmark; responsible for tumor heterogeneity; therapy resistance and relapse. The discussion will contextualize the involvement of nucleolin in the establishment of cancer hallmarks and its application as a marker protein for targeted anticancer therapies

Growth Factor Midkine Aggravates Pulmonary Arterial Hypertension via Surface Nucleolin

Pulmonary arterial hypertension (PAH) is a progressive fatal disease caused by pulmonary arterial remodeling. Midkine regulates cell proliferation and migration, and it is induced by hypoxia, but its roles in pulmonary arterial remodeling remain unclear. Serum midkine levels were significantly increased in PAH patients compared with control patients. Midkine expression was increased in lungs and sera of hypoxia-induced PAH mice. Hypoxia-induced pulmonary arterial remodeling and right ventricular hypertrophy were attenuated in midkine-knockout mice. Midkine-induced proliferation and migration of pulmonary arterial smooth muscle cells (PASMC) and epidermal growth factor receptor (EGFR) signaling were significantly increased under hypoxia, which also induced cell-surface translocation of nucleolin. Nucleolin siRNA treatment suppressed midkine-induced EGFR activation in vitro, and nucleolin inhibitor AS1411 suppressed proliferation and migration of PASMC induced by midkine. Furthermore, AS1411 significantly prevented the development of PAH in Sugen hypoxia rat model. Midkine plays a crucial role in PAH development through interaction with surface nucleolin. These data define a role for midkine in PAH development and suggest midkine-nucleolin-EGFR axis as a novel therapeutic target for PAH.

Intracellular partners of fibroblast growth factors 1 and 2 - implications for functions

Fibroblast growth factors 1 and 2 (FGF1 and FGF2) are mainly considered as ligands of surface receptors through which they regulate a broad spectrum of biological processes. They are secreted in non-canonical way and, unlike other growth factors, they are able to translocate from the endosome to the cell interior. These unique features, as well as the role of the intracellular pool of FGF1 and FGF2, are far from being fully understood. An increasing number of reports address this problem, focusing on the intracellular interactions of FGF1 and 2. Here, we summarize the current state of knowledge of the FGF1 and FGF2 binding partners inside the cell and the possible role of these interactions. The partner proteins are grouped according to their function, including proteins involved in secretion, cell signaling, nucleocytoplasmic transport, binding and processing of nucleic acids, ATP binding, and cytoskeleton assembly. An in-depth analysis of the network of these binding partners could indicate novel, non-classical functions of FGF1 and FGF2 and uncover an additional level of a fine control of the well-known FGF-regulated cellular processes.

Nucleolin-based targeting strategies for cancer therapy: from targeted drug delivery to cytotoxic ligands

Cancer is currently the second leading cause of death worldwide and current therapeutic approaches remain ineffective in several cases. Therefore, there is a need to develop more efficacious therapeutic agents, especially for subtypes of cancer lacking targeted therapies. Limited drug penetration into tumors impairs the efficacy of therapies targeting cancer cells. One of the strategies to overcome this problem is targeting the more accessible tumor vasculature via molecules such as nucleolin, which is expressed at the surface of cancer and angiogenic endothelial cells, thus enabling a dual cellular targeting strategy. In this review, we present and discuss nucleolin-based targeting strategies that have been developed for cancer therapy, with a special focus on recent antibody-based approaches.

Hsc70 Interacts with β4GalT5 to Regulate the Growth of Gliomas

Heat shock cognate protein 70 (Hsc70) is a key mediator for the maintenance of intracellular proteins and regulates cellular activities. And it is elevated in various tumor tissues including glioma, which is closely related to the malignancy and poor prognosis of the tumors. However, the effects of Hsc70 on gliomas and its regulatory mechanism have not yet been elucidated. In the present study, we found that Hsc70 was overexpressed in glioma tissues and cultured glioma cells. Furthermore, Hsc70 expression exhibited positive correlation with the grades of gliomas. Knockdown of Hsc70 could effectively inhibit cell proliferation and increase cell apoptosis. Furthermore, we identified that β4GalT5 was a critical target for Hsc70-mediated anti-glioma effects. Blocking β4GalT5 activity could effectively reverse the anti-tumor effect of Hsc70. Taken together, these data indicate that Hsc70 regulates β4GalT5 levels, and possibly plays a role in cell proliferation and apoptosis of glioma.

Blocking nuclear export of HSPA8 after heat shock stress severely alters cell survival

The nuclear translocation of endogenous heat shock cognate protein HSPA8 is a requisite for cell survival during oxidative and heat shock stress. Upon these events, cytoplasmic HSPA8 is thought to concentrate within the nucleus and nucleolus. When the situation returns to normal, HSPA8 is released from its nuclear/nucleolar anchors and redistributes into the cytoplasm. By using different stress conditions and a 21-mer phosphopeptide tool called P140, which binds HSPA8 and hampers its chaperone properties, we deciphered the cellular and molecular effects arising during this vital cytoplasmic-nuclear-cytoplasmic shuttling process. Using the non-metastatic fibroblastoid cell line MRL/N-1 derived from a MRL/MpTn-gld/gld lupus-prone mouse, we discovered that P140 treatment neutralized the egress of HSPA8 from nucleus to cytoplasm in the cell recovery phase. This lack of relocation of HSPA8 into the cytoplasm of heat-shocked MRL/N-1 cells altered the ability of these cells to survive when a second mild oxidative stress mimicking inflammatory conditions was applied. Crosslinking experiments followed by proteomics studies showed that P140 binds regions close to nuclear import and export signal sequences encompassed within the HSPA8 structure. These data are consistent with HSPA8 having a crucial cell protective role against reactive oxygen species (ROS) production by mitochondria during inflammatory conditions.

The anti-tumor diterpene oridonin is a direct inhibitor of Nucleolin in cancer cells

The bioactive plant diterpene oridonin displays important pharmacological activities and is widely used in traditional Chinese medicine; however, its molecular mechanism of action is still incompletely described. In vitro and in vivo data have demonstrated anti-tumor activity of oridonin and its ability to interfere with several cell pathways; however, presently only the molecular chaperone HSP70 has been identified as a direct potential target of this compound. Here, using a combination of different proteomic approaches, innovative Cellular Thermal Shift Assay (CETSA) experiments, and classical biochemical methods, we demonstrate that oridonin interacts with Nucleolin, effectively modulating the activity of this multifunctional protein. The ability of oridonin to target Nucleolin and/or HSP70 could account for the bioactivity profile of this plant diterpene. Recently, Nucleolin has attracted attention as a druggable target, as its diverse functions are implicated in pathological processes such as cancer, inflammation, and viral infection. However, up to now, no small molecule as Nucleolin binders has been reported, thus our finding represents the first evidence of Nucleolin modulation by a small inhibitor.

c-Myc targeted regulators of cell metabolism in a transgenic mouse model of papillary lung adenocarcinoma

c-Myc's role in pulmonary cancer metabolism is uncertain. We therefore investigated c-Myc activity in papillary lung adenocarcinomas (PLAC). Genomics revealed 90 significantly regulated genes (> 3-fold) coding for cell growth, DNA metabolism, RNA processing and ribosomal biogenesis and bioinformatics defined c-Myc binding sites (TFBS) at > 95% of up-regulated genes. EMSA assays at 33 novel TFBS evidenced DNA binding activity and ChIP-seq data retrieved from public repositories confirmed these to be c-Myc bound. Dual-luciferase gene reporter assays developed for RNA-Terminal-Phosphate-Cyclase-Like-1(RCL1), Ribosomal-Protein-SA(RPSA), Nucleophosmin/Nucleoplasmin-3(NPM3) and Hexokinase-1(HK1) confirmed c-Myc functional relevance and ChIP assays with HEK293T cells over-expressing ectopic c-Myc demonstrated enriched c-Myc occupancy at predicted TFBS for RCL1, NPM3, HK1 and RPSA. Note, c-Myc recruitment on chromatin was comparable to the positive controls CCND2 and CDK4. Computational analyses defined master regulators (MR), i.e. heterogeneous nuclear ribonucleoprotein A1, nucleolin, the apurinic/apyrimidinic endonuclease 1, triosephosphate-isomerase 1, folate transporter (SLC19A1) and nucleophosmin to influence activity of up to 90% of PLAC-regulated genes. Their expression was induced by 3-, 3-, 6-, 3-, 11- and 7-fold, respectively. STRING analysis confirmed protein-protein-interactions of regulated genes and Western immunoblotting of fatty acid synthase, serine hydroxyl-methyltransferase 1, arginine 1 and hexokinase 2 showed tumor specific induction. Published knock down studies confirmed these proteins to induce apoptosis by disrupting neoplastic lipogenesis, by endorsing uracil accumulation and by suppressing arginine metabolism and glucose-derived ribonucleotide biosynthesis. Finally, translational research demonstrated high expression of MR and of 47 PLAC up-regulated genes to be associated with poor survival in lung adenocarcinoma patients (HR 3.2 p < 0.001) thus, providing a rationale for molecular targeted therapies in PLACs.

Mitochondrial catalase induces cells transformation through nucleolin-dependent Cox-2 mRNA stabilization

It's well documented that over-production of reactive oxygen species (ROS) causes detrimental damages to cells. While a low level of ROS, such as H2O2, functions as signaling transducer and motivates cell proliferation in both cancer and non-transformed stem cells. As a double-edged sword, the direct evidence for demonstrating the function of H2O2 in the cause of tumor is barely characterized in intact cells. In our current study, we found that targeted expression of mitochondrial catalase (mCAT), but not catalase, could significantly reduce the accumulation of H2O2 in mouse epithelial JB6 Cl41 cells, consequently led to the cell malignant transformation and anchorage-independent cell growth. Further study revealed that this reduction of H2O2 resulted in the translocation of nucleolin from the cytoplasm to nuclear, and maintaining the nucleolin nuclear location status, and in turn stabilizing the cox-2 mRNA and consequently leading to a COX-2 protein upregulation, as well as malignant transforming mCAT-overexpressed Cl41 cells. Collectively, our studies here provide direct experimental evidence demonstrating a novel function and molecular mechanisms of mCAT in transforming mouse Cl41 cells, and high significance insight into understanding the beneficial aspect of H2O2 in circumventing tumor promotion and the theoretical basis for the management of H2O2 in the clinic implementation as a chemotherapeutic strategy.

Multifaceted Nucleolin Protein and Its Molecular Partners in Oncogenesis

Discovered in 1973, nucleolin is one of the most abundant phosphoproteins of the nucleolus. The ability of nucleolin to be involved in many cellular processes is probably related to its structural organization and its capability to form many different interactions with other proteins. Many functions of nucleolin affect cellular processes involved in oncogenesis-for instance: in ribosome biogenesis; in DNA repair, remodeling, and genome stability; in cell division and cell survival; in chemokine and growth factor signaling pathways; in angiogenesis and lymphangiogenesis; in epithelial-mesenchymal transition; and in stemness. In this review, we will describe the different functions of nucleolin in oncogenesis through its interaction with other proteins.

New perspectives of physiological and pathological functions of nucleolin (NCL)

Nucleolin (NCL) is a multifunctional protein that mainly localized in the nucleolus, it is also found in the nucleoplasm, cytoplasm and cell membrane. The three main structural domains allow the interaction of NCL with different proteins and RNA sequences. Moreover, specific post-translational modifications and its shuttling property also contribute to its multifunctionality. NCL has been demonstrated to be involved in a variety of aspects such as ribosome biogenesis, chromatin organization and stability, DNA and RNA metabolism, cytokinesis, cell proliferation, angiogenesis, apoptosis regulation, stress response and microRNA processing. NCL has been increasingly implicated in several pathological processes, especially in tumorigenesis and viral infection, which makes NCL a potential target for the development of anti-tumor and anti-viral strategies. In this review, we present an overview on the structure, localizations and various functions of NCL, and further describe how the multiple functions of NCL are correlated to its multiple cellular distributions.

Evaluation of somatostatin and nucleolin receptors for therapeutic delivery in non-small cell lung cancer stem cells applying the somatostatin-analog DOTATATE and the nucleolin-targeting aptamer AS1411

Cancer stem cells represent the putative tumor-driving subpopulation thought to account for drug resistance, relapse, and metastatic spread of epithelial and other cancer types. Accordingly, cell surface markers for therapeutic delivery to cancer stem cells are subject of intense research. Somatostatin receptor 2 and nucleolin are known to be overexpressed by various cancer types, which have elicited comprehensive efforts to explore their therapeutic utilization. Here, we evaluated somatostatin receptor 2 targeting and nucleolin targeting for therapeutic delivery to cancer stem cells from lung cancer. Nucleolin is expressed highly but not selectively, while somatostatin receptor 2 is expressed selectively but not highly by cancer cells. The non-small cell lung cancer cell lines A549 and H1299, displayed average levels of both surface molecules as judged based on analysis of a larger cell line panel. H1299 compared to A549 cells showed significantly elevated sphere-forming capacity, indicating higher cancer stem cell content, thus qualifying as suitable test system. Nucleolin-targeting 57Co-DOTA-AS1411 aptamer showed efficient internalization by cancer cells and, remarkably, at even higher efficiency by cancer stem cells. In contrast, somatostatin receptor 2 expression levels were not sufficiently high in H1299 cells to confer efficient uptake by either non-cancer stem cells or cancer stem cells. The data provides indication that the nucleolin-targeting AS1411 aptamer might be used for therapeutic delivery to non-small cell lung cancer stem cells.

HSP70-1 is required for interleukin-5-induced angiogenic responses through eNOS pathway

We report a pivotal role for IL-5 as an angiogenic activator. IL-5 increased proliferation, migration and colony tube formation in HUVECs associated with the phosphorylation of ERK and AKT/eNOS, and promoted microvessel sprouting from an angiogenesis animal model. The angiogenic effects were confirmed in IL-5-deficient mice and addition of IL-5 antibody. HSP70-1 was identified via expression profiling following IL-5 stimulation. A siRNA knockdown of HSP70-1 suppressed angiogenic responses and eNOS phosphorylation induced by IL-5. HSP70-1 overexpression enhanced IL-5-induced angiogenic responses. In addition, IL-5-induced neo-vascular formation was verified in both HSP70-1 knockout and HSP70-1 transgenic mice. Furthermore, transcription factor AP-1 was a main factor in IL-5-induced HSP70-1 in response to ERK and AKT signaling pathway. Angiogenic responses induced by VEGF had no effect in either HSP70-1 siRNA in vitro or HSP70-1 knockout mice. IL-5-induced angiogenic responses depended on the binding of IL-5Rα. Our data demonstrate that binding of IL-5 to IL-5Rα receptors enhances angiogenic responses by stimulating the expression of HSP70-1 via the eNOS signaling pathway.

Involvement of nuclear protein C23 in activation of EGFR signaling in cervical cancer

Nuclear protein C23 and epidermal growth factor receptor (EGFR) are reported to be correlated with cervical cancer (CC). However the correlations between C23 and EGFR were rarely reported. Here, this study explored the effects of C23 in activation of EGFR signaling pathway. In our study, immunohistochemistry was used to identify the expression of C23 or EGFR in CC tissues. The level of the phosphorylated EGFR was observed by western blot, and cell invasion capacity was detected by Transwell assay. In this study, we found that C23 and EGFR were highly expressed in cervical cancer tissues, while C23 on the cell surface mainly expressed in CC tissues with lymph node metastasis, and was correlated to EGFR statistically. In vitro, western blot showed that either anti-C23 or anti-EGFR antibodies can inhibit the phosphorlation of EGFR with significant differences (p < 0.01). Besides, based on Transwell assay, the number of membrane-invading cells was reduced significantly in anti-C23 group, and no significant difference was found compared with anti-EGFR treatment (p > 0.05). In conclusion, C23 on the cell surface may be a kind of indispensable component in activation of EGFR signaling, by which C23 can participate in the growth and invasion of tumors. C23 antagonists may provide a new field for cervical cancer therapy.

Nucleolin enhances the proliferation and migration of heat-denatured human dermal fibroblasts

Denatured dermis, a part of dermis in burned skin, has the ability to restore its normal morphology and functions after their surrounding microenvironment is improved. However, the cellular and molecular mechanisms by which the denatured dermis could improve wound healing are still unclear. This study aimed to investigate the role of nucleolin during the recovery of heat-denatured human dermal fibroblasts. Nucleolin mRNA and protein expression were significantly increased time-dependently during the recovery of heat-denatured human dermal fibroblasts (52 °C, 30 seconds). Heat-denaturation promoted a time-dependent cell proliferation, migration, chemotaxis, and scratched wound healing during the recovery of human dermal fibroblasts. These effects were prevented by knockdown of nucleolin expression with small interference RNA (siRNA), whereas overexpression of nucleolin enhanced cell proliferation, migration, and chemotaxis of human dermal fibroblasts with heat-denaturation. In addition, the expression of transforming growth factor-beta 1(TGF-β1) was significantly increased during the recovery of heat-denatured dermis and human dermal fibroblasts. TGF-β1 expression was up-regulated by nucleolin in human dermal fibroblasts. The results suggest that nucleolin expression is up-regulated, and play an important role in promoting cell proliferation, migration, and chemotaxis of human dermal fibroblasts during the recovery of heat-denatured dermis with a mechanism probably related to TGF-β1.

Endostatin Prevents Dietary-Induced Obesity by Inhibiting Adipogenesis and Angiogenesis

Endostatin is a well-known angiogenesis inhibitor. Although angiogenesis has been considered as a potential therapeutic target of obesity, the inhibitory effect of endostatin on adipogenesis and dietary-induced obesity has never been demonstrated. Adipogenesis plays a critical role in controlling adipocyte cell number, body weight, and metabolic profile in a homeostatic state. Here we reveal that endostatin inhibits adipogenesis and dietary-induced obesity. The antiadipogenic mechanism of endostatin lies in its interaction with Sam68 RNA-binding protein in the nuclei of preadipocytes. This interaction competitively impairs the binding of Sam68 to intron 5 of mammalian target of rapamycin (mTOR), causing an error in mTOR transcript. This consequently decreases the expression of mTOR, results in decreased activities of the mTOR complex 1 pathway, and leads to defects in adipogenesis. Moreover, our findings demonstrate that the antiangiogenic function of endostatin also contributes to its obesity-inhibitory activity. Through the combined functions on adipogenesis and angiogenesis, endostatin prevents dietary-induced obesity and its related metabolic disorders, including insulin resistance, glucose intolerance, and hepatic steatosis. Thus, our findings reveal that endostatin has a potential application for antiobesity therapy and the prevention of obesity-related metabolic syndromes.

Phosphorylation and changes in the distribution of nucleolin promote tumor metastasis via the PI3K/Akt pathway in colorectal carcinoma

Here, we investigated the molecular mechanism underlying the changes in the distribution of nucleolin. Our study identified PI3K/Akt signaling as an essential pathway regulating the distribution of nucleolin. Furthermore, nucleolin can interact with phospho-PI3K-p55, and changes in the distribution of nucleolin were related to its phosphorylation. Subsequently, we analyzed the correlation of VEGF and nucleolin, and found that distribution of nucleolin related to metastatic potential. Finally, blocking cell surface nucleolin influences the process of epithelial-mesenchymal transitions. This indicates that nucleolin may be a novel cancer therapy target and a predictive marker for tumor migration in colorectal carcinoma.

A novel autoantibody test for the detection of pre-neoplastic lung lesions

Background

Atypical adenomatous hyperplasia (AAH) and squamous cell dysplasia (SCD) are associated with the development of malignant lesions in the lung. Accurate diagnosis of AAH and SCD could facilitate earlier clinical intervention and provide useful information for assessing lung cancer risk in human populations. Detection of AAH and SCD has been achieved by imaging and bronchoscopy clinically, but sensitivity and specificity remain less than satisfactory. We utilized the ability of the immune system to identify lesion specific proteins for detection of AAH and SCD.

Methods

AAH and SCD tissue was surgically removed from six patients of Chinese descent (3 AAH and 3 SCD) with corresponding serum samples. Total RNA was extracted from the tissues and a cDNA library was generated and incorporated into a T7 bacteriophage vector. Following enrichment to remove "normal" reactive phages, a total of 200 AAH related and 200 SCD related phage clones were chosen for statistical classifier development and incorporation into a microarray. Microarray slides were tested with an independent double-blinded population consisting of 100 AAH subjects, 100 SCD subjects and 200 healthy control subjects.

Results

Sensitivity of 82% and specificity of 70% were achieved in the detection of AAH using a combination of 9 autoantibody biomarkers. Likewise, 86% sensitivity and 78% specificity were achieved in the detection of SCD using a combination of 13 SCD-associated markers. Sequencing analysis identified that most of these 22 autoantibody biomarkers had known malignant associations.

Conclusions

Both diagnostic values showed promising sensitivity and specificity in detection of pre-neoplastic lung lesions. Hence, this technology could be a useful non-invasive tool to assess lung cancer risk in human populations.

The regulatory mechanism of a client kinase controlling its own release from Hsp90 chaperone machinery through phosphorylation

It is believed that the stability and activity of client proteins are passively regulated by the Hsp90 (heat-shock protein 90) chaperone machinery, which is known to be modulated by its intrinsic ATPase activity, co-chaperones and post-translational modifications. However, it is unclear whether client proteins themselves participate in regulation of the chaperoning process. The present study is the first example to show that a client kinase directly regulates Hsp90 activity, which is a novel level of regulation for the Hsp90 chaperone machinery. First, we prove that PKCγ (protein kinase Cγ) is a client protein of Hsp90α, and, that by interacting with PKCγ, Hsp90α prevents PKCγ degradation and facilitates its cytosol-to-membrane translocation and activation. A threonine residue set, Thr¹¹⁵/Thr⁴²⁵/Thr⁶⁰³, of Hsp90α is specifically phosphorylated by PKCγ, and, more interestingly, this threonine residue set serves as a ‘phosphorylation switch’ for Hsp90α binding or release of PKCγ. Moreover, phosphorylation of Hsp90α by PKCγ decreases the binding affinity of Hsp90α towards ATP and co-chaperones such as Cdc37 (cell-division cycle 37), thereby decreasing its chaperone activity. Further investigation demonstrated that the reciprocal regulation of Hsp90α and PKCγ plays a critical role in cancer cells, and that simultaneous inhibition of PKCγ and Hsp90α synergistically prevents cell migration and promotes apoptosis in cancer cells.

The present study is the first example to show that a client directly regulates Hsp90 activity, which is a novel level of regulation for the Hsp90 chaperone machinery.

Genetically engineered endostatin-lidamycin fusion proteins effectively inhibit tumor growth and metastasis

Background

Endostatin (ES) inhibits endothelial cell proliferation, migration, invasion, and tube formation. It also shows antiangiogenesis and antitumor activities in several animal models. Endostatin specifically targets tumor vasculature to block tumor growth. Lidamycin (LDM), which consists of an active enediyne chromophore (AE) and a non-covalently bound apo-protein (LDP), is a member of chromoprotein family of antitumor antibiotics with extremely potent cytotoxicity to cancer cells. Therefore, we reasoned that endostatin-lidamycin (ES-LDM) fusion proteins upon energizing with enediyne chromophore may obtain the combined capability targeting tumor vasculature and tumor cell by respective ES and LDM moiety.

Methods

In this study, we designed and obtained two new endostatin-based fusion proteins, endostatin-LDP (ES-LDP) and LDP-endostatin (LDP-ES). In vitro, the antiangiogenic effect of fusion proteins was determined by the wound healing assay and tube formation assay and the cytotoxicity of their enediyne-energized analogs was evaluated by CCK-8 assay. Tissue microarray was used to analyze the binding affinity of LDP, ES or ES-LDP with specimens of human lung tissue and lung tumor. The in vivo efficacy of the fusion proteins was evaluated with human lung carcinoma PG-BE1 xenograft and the experimental metastasis model of 4T1-luc breast cancer.

Results

ES-LDP and LDP-ES disrupted the formation of endothelial tube structures and inhibited endothelial cell migration. Evidently, ES-LDP accumulated in the tumor and suppressed tumor growth and metastasis. ES-LDP and ES show higher binding capability than LDP to lung carcinoma; in addition, ES-LDP and ES share similar binding capability. Furthermore, the enediyne-energized fusion protein ES-LDP-AE demonstrated significant efficacy against lung carcinoma xenograft in athymic mice.

Conclusions

The ES-based fusion protein therapy provides some fundamental information for further drug development. Targeting both tumor vasculature and tumor cells by endostatin-based fusion proteins and their enediyne-energized analogs probably provides a promising modality in cancer therapy.

Nucleolin protects the heart from ischaemia-reperfusion injury by up-regulating heat shock protein 32

AIMS

Nucleolin plays important roles in a variety of cellular processes. In this study, we aimed to investigate the role of nucleolin in cardiac ischaemia-reperfusion (I-R) injury.

METHODS AND RESULTS

We investigated the expression pattern of nucleolin in hearts subjected to I-R, or neonatal rat cardiomyocytes subjected to hypoxia-re-oxygenation. We found that nucleolin expression was significantly down-regulated and the cleaved protein was present, both in vivo and in vitro. Gene transfection and RNA interference approaches were employed in cardiomyocytes to investigate the function of nucleolin. Over-expression of nucleolin was cytoprotective, whereas nucleolin ablation enhanced both hypoxia- and H₂O₂-induced cardiomyocyte death. Furthermore, transgenic mice with cardiac-specific over-expression of nucleolin were resistant to I-R injury as indicated by decreased cellular necrosis and decreased infarct size. The cardio-protective roles of nucleolin in cardiomyocytes, are attributable to the interaction of nucleolin with the mRNA of heat shock protein 32 (Hsp32), resulting in an increase of Hsp32 mRNA stability, and subsequent up-regulation of Hsp32 expression. The selective Hsp32 inhibitor, zinc protoporphyrin-IX, abrograted the cardiac protection mediated by nucleolin.

CONCLUSION

This study has demonstrated that nucleolin is involved in the regulation of I-R-induced cardiac injury and dysfunction via the regulation of Hsp32, and may be a novel therapeutic target for ischaemic heart diseases.

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.