Hsp90 binds directly to fibronectin (FN) and inhibition reduces the extracellular fibronectin matrix in breast cancer cells

The Role of eHsp90 in Extracellular Matrix Remodeling, Tumor Invasiveness, and Metastasis

Identifying proteins that act in tumor invasiveness and metastasis remains a critical unmet need in our search for effective cancer therapy. Hsp90, an abundant intracellular chaperone protein, plays a key role in maintaining cell homeostasis, and its elevated activity is pivotal in cancer progression. Due to the reliance of cancer cells on Hsp90's chaperone function to sustain tumor growth and spread, Hsp90 inhibitors have been the subject of numerous clinical trials over the past two decades. However, these efforts have largely been unsuccessful, primarily due to the cellular toxicity caused by pan-Hsp90 inhibitors at doses required for anticancer efficacy. Therefore, novel approaches to target Hsp90 are necessary. An identified subpopulation of Hsp90 located outside cells (eHsp90) may offer a promising alternative as a therapeutic target against cancer. Studies including our own have shown that eHsp90 is released specifically by cancer cells, and eHsp90 has unique interactors and functions extracellularly to promote tumor invasiveness, the initial step in metastasis. Inhibition of eHsp90 has been shown to suppress metastasis in animal models, indicating its therapeutic potential, although the underlying mechanisms remain incompletely understood. Cancer cells modulate the tumor microenvironment (TME) during the invasion, especially the ECM proteins and the state of the ECM is a strong predictor of invasive and metastatic cancer. Given that most of the known eHsp90 clients are ECM proteins or are proteins involved in ECM modulation, ECM remodelling could be the key mechanism through which eHsp90 enhances invasiveness. This review will focus on ECM modulation by eHsp90 as a driver of cancer invasion and metastasis. We will also discuss the potency of inhibiting eHsp90 in inhibiting invasion and metastatic spread in preclinical models and the using circulating Hsp90 patient samples as a biomarker of cancer invasion and metastasis.

Modulators of the Hop-HSP90 Protein-Protein Interaction Disrupt KSHV Lytic Replication

The central role of the chaperome in maintaining cellular proteostasis has seen numerous viral families evolve to parasitically exploit host chaperones in their life cycle. The HSP90 chaperone protein and its cochaperone Hop have both individually been shown to be essential factors for Kaposi sarcoma-associated herpesvirus (KSHV) lytic replication. Given the fundamental regulatory role that protein-protein interactions (PPIs) play in cellular biology, we reasoned that disrupting the Hop-HSP90 PPI may provide a new host-based target for inhibiting KSHV lytic replication. This study expands upon a previous report of non-natural peptides, which were found to disrupt the association between the HopTPR2A domain and its interacting HSP90CTD. Here, in addition to providing insight into the structure-activity relationships of PPI inhibition, we show disruption of the full-length Hop-HSP90 PPI. The inhibitory peptides selectively engaged the HopTPR2A domain in cell lysates and when tethered to a cell-penetrating peptide acted as noncytotoxic inhibitors of KSHV lytic replication by lowering the viral load, preventing the production of infectious virions, and reducing the expression of KSHV lytic genes. In addition to tentative evidence of Hop-HSP90 PPI as a much-needed target for KSHV drug discovery, this study represents an important step in understanding viral interactions with the host proteostasis machinery.

Rationally modified SNX-class Hsp90 inhibitors disrupt extracellular fibronectin assembly without intracellular Hsp90 activity

Despite Hsp90's well documented promise as a target for developing cancer chemotherapeutics, its inhibitors have struggled to progress through clinical trials. This is, in part, attributed to the cytoprotective compensatory heat shock response (HSR) stimulated through intracellular Hsp90 inhibition. Beyond its intracellular role, secreted extracellular Hsp90 (eHsp90) interacts with numerous pro-oncogenic extracellular clients. This includes fibronectin, which in the tumour microenvironment enhances cell invasiveness and metastasis. Through the rational modification of known Hsp90 inhibitors (SNX2112 and SNX25a) we developed four Hsp90 inhibitory compounds, whose alterations restricted their interaction with intracellular Hsp90 and did not stimulate the HSR. Two of the modified cohort (compounds 10 and 11) were able to disrupt the assembly of the extracellular fibronectin network at non-cytotoxic concentrations, and thus represent promising new tool compounds for studying the druggability of eHsp90 as a target for inhibition of tumour invasiveness and metastasis.

Membrane-bound Heat Shock Protein mHsp70 Is Required for Migration and Invasion of Brain Tumors

Molecular chaperones, especially 70 kDa heat shock protein, in addition to their intracellular localization in cancer cells, can be exposed on the surface of the plasma membrane. We report that the membrane-associated chaperone mHsp70 of malignant brain tumors is required for high migratory and invasive activity of cancer cells. Live-cell inverted confocal microscopy of tumor samples from adult (n = 23) and pediatric (n = 9) neurooncologic patients showed pronounced protein expression on the membrane, especially in the perifocal zone. Mass spectrometry analysis of lipid rafts isolated from tumor cells confirmed the presence of the protein in the chaperone cluster (including representatives of other families, such as Hsp70, Hsc70, Hsp105, and Hsp90), which in turn, during interactome analysis, was associated with proteins involved in cell migration (e.g., Rac1, RhoC, and myosin-9). The use of small-molecule inhibitors of HSP70 (PES and JG98) led to a substantial decrease in the invasive potential of cells isolated from a tumor sample of patients, which indicates the role of the chaperone in invasion. Moreover, the use of HSP70 inhibitors in animal models of orthotopic brain tumors significantly delayed tumor progression, which was accompanied by an increase in overall survival. Data demonstrate that chaperone inhibitors, particularly JG98, disrupt the function of mHsp70, thereby providing an opportunity to better understand the diverse functions of this protein and offer aid in the development of novel cancer therapies.

SIGNIFICANCE

Membrane-bound mHsp70 is required for brain tumor cell migration and invasion and therefore could be employed as a target for anticancer therapies.

RosetteArray® Platform for Quantitative High-Throughput Screening of Human Neurodevelopmental Risk

Neural organoids have revolutionized how human neurodevelopmental disorders (NDDs) are studied. Yet, their utility for screening complex NDD etiologies and in drug discovery is limited by a lack of scalable and quantifiable derivation formats. Here, we describe the RosetteArray® platform's ability to be used as an off-the-shelf, 96-well plate assay that standardizes incipient forebrain and spinal cord organoid morphogenesis as micropatterned, 3-D, singularly polarized neural rosette tissues (>9000 per plate). RosetteArrays are seeded from cryopreserved human pluripotent stem cells, cultured over 6-8 days, and immunostained images can be quantified using artificial intelligence-based software. We demonstrate the platform's suitability for screening developmental neurotoxicity and genetic and environmental factors known to cause neural tube defect risk. Given the presence of rosette morphogenesis perturbation in neural organoid models of NDDs and neurodegenerative disorders, the RosetteArray platform could enable quantitative high-throughput screening (qHTS) of human neurodevelopmental risk across regulatory and precision medicine applications.

Mutations F352A and Y528A in human HSP90α reduce fibronectin association and fibrillogenesis in cell-derived matrices

HSP90 is a ubiquitously expressed chaperone protein that regulates the maturation of numerous substrate proteins called 'clients'. The glycoprotein fibronectin (FN) is an important protein of the extracellular matrix (ECM) and a client protein of HSP90. FN and HSP90 interact directly, and the FN ECM is regulated by exogenous HSP90 or HSP90 inhibitors. Here, we extend the analysis of the HSP90 - FN interaction. The importance of the N-terminal 70-kDa fragment of fibronectin (FN70) and FN type I repeat was demonstrated by competition for FN binding between HSP90 and the functional upstream domain (FUD) of the Streptococcus pyogenes F1 adhesin protein. Furthermore, His-HSP90α mutations F352A and Y528A (alone and in combination) reduced the association with full-length FN (FN-FL) and FN70 in vitro. Unlike wild type His-HSP90α, these HSP90 mutants did not enhance FN matrix assembly in the Hs578T cell line model when added exogenously. Interestingly, the HSP90 E353A mutation, which did not significantly reduce the HSP90 - FN interaction in vitro, dramatically blocked FN matrix assembly in Hs578T cell-derived matrices. Taken together, these data extend our understanding of the role of HSP90 in FN fibrillogenesis and suggest that promotion of FN ECM assembly by HSP90 is not solely regulated by the affinity of the direct interaction between HSP90 and FN.

Extracellular Hsp90 Binds to and Aligns Collagen-1 to Enhance Breast Cancer Cell Invasiveness

Cancer cell-secreted eHsp90 binds and activates proteins in the tumor microenvironment crucial in cancer invasion. Therefore, targeting eHsp90 could inhibit invasion, preventing metastasis-the leading cause of cancer-related mortality. Previous eHsp90 studies have solely focused on its role in cancer invasion through the 2D basement membrane (BM), a form of extracellular matrix (ECM) that lines the epithelial compartment. However, its role in cancer invasion through the 3D Interstitial Matrix (IM), an ECM beyond the BM, remains unexplored. Using a Collagen-1 binding assay and second harmonic generation (SHG) imaging, we demonstrate that eHsp90 directly binds and aligns Collagen-1 fibers, the primary component of IM. Furthermore, we show that eHsp90 enhances Collagen-1 invasion of breast cancer cells in the Transwell assay. Using Hsp90 conformation mutants and inhibitors, we established that the Hsp90 dimer binds to Collagen-1 via its N-domain. We also demonstrated that while Collagen-1 binding and alignment are not influenced by Hsp90's ATPase activity attributed to the N-domain, its open conformation is crucial for increasing Collagen-1 alignment and promoting breast cancer cell invasion. These findings unveil a novel role for eHsp90 in invasion through the IM and offer valuable mechanistic insights into potential therapeutic approaches for inhibiting Hsp90 to suppress invasion and metastasis.

Collagen-I influences the post-translational regulation, binding partners and role of Annexin A2 in breast cancer progression

Introduction

The extracellular matrix (ECM) has been heavily implicated in the development and progression of cancer. We have previously shown that Annexin A2 is integral in the migration and invasion of breast cancer cells and in the clinical progression of ER-negative breast cancer, processes which are highly influenced by the surrounding tumor microenvironment and ECM.

Methods

We investigated how modulations of the ECM may affect the role of Annexin A2 in MDA-MB-231 breast cancer cells using western blotting, immunofluorescent confocal microscopy and immuno-precipitation mass spectrometry techniques.

Results

We have shown that the presence of collagen-I, the main constituent of the ECM, increases the post-translational phosphorylation of Annexin A2 and subsequently causes the translocation of Annexin A2 to the extracellular surface. In the presence of collagen-I, we identified fibronectin as a novel interactor of Annexin A2, using mass spectrometry analysis. We then demonstrated that reducing Annexin A2 expression decreases the degradation of fibronectin by cancer cells and this effect on fibronectin turnover is increased according to collagen-I abundance.

Discussion

Our results suggest that Annexin A2's role in promoting cancer progression is mediated by collagen-I and Annexin A2 maybe a therapeutic target in the bi-directional cross-talk between cancer cells and ECM remodeling that supports metastatic cancer progression.

A Coumarin-Imidazothiadiazole Derivative, SP11 Abrogates Tumor Growth by Targeting HSP90 and Its Client Proteins

Despite several treatment options for blood cancer, mortality remains high due to relapse and the disease's aggressive nature. Elevated levels of HSP90, a molecular chaperone essential for protein folding, are associated with poor prognosis in leukemia and lymphoma. HSP90 as a target for chemotherapy has been met with limited success due to toxicity and induction of heat shock. This study tested the activity of an HSP90 inhibitor, SP11, against leukemic cells, mouse lymphoma allograft, and xenograft models. SP11 induced cytotoxicity in vitro in leukemic cell lines and induced cell death via apoptosis, with minimal effect on normal cells. SP11 induced cell death by altering the status of HSP90 client proteins both in vitro and in vivo. SP11 reduced the tumor burden in allograft and xenograft mouse models without apparent toxicity. The half-life of SP11 in the plasma was approximately 2 h. SP11 binding was observed at both the N-terminal and C-terminal domains of HSP90. C-terminal binding was more potent than N-terminal binding of HSP90 in silico and in vitro using isothermal calorimetry. SP11 bioavailability and minimal toxicity in vivo make it a potential candidate to be developed as a novel anticancer agent.

Optimizing antidotal treatment with the oral HSP90 inhibitor TAS-116 against hydrochloric acid-induced pulmonary fibrosis in mice

Exposure to high concentrations of hydrochloric acid (HCl) can lead to severe acute and chronic lung injury. In the aftermath of accidental spills, victims may be treated for the acute symptoms, but the chronic injury is often overlooked. We have developed a mouse model of acute and chronic lung injury, in which the peak of acute lung injury occurs on the day 4 after HCl exposure. We have also demonstrated that HSP90 inhibitors are effective antidotes when administered starting 24 h after HCl. In this study we examined the hypothesis that the novel oral HSP90 inhibitor TAS-116 can effectively ameliorate HCl-induced lung injury even when treatment starts at the peak of the acute injury, as late as 96 h after HCl. C57BI/6J mice were intratracheally instilled with 0.1N HCl. After 24 or 96 h, TAS-116 treatment began (3.5, 7 or 14 mg/kg, 5 times per week, p. o.) for either 2,3 or 4 or weeks. TAS-116 moderated the HCl-induced alveolar inflammation, as reflected in the reduction of white blood cells and total protein content in bronchoalveolar lavage fluid (BALF), overexpression of NLRP3 inflammasome, and inhibited the activation of pro-fibrotic pathways. Furthermore, TAS-116 normalized lung mechanics and decreased the deposition of extracellular matrix proteins in the lungs of mice exposed to HCl. Delayed and shortened treatment with TAS-116, successfully blocked the adverse chronic effects associated with acute exposure to HCl.

In silico analysis of the HSP90 chaperone system from the African trypanosome, Trypanosoma brucei

African trypanosomiasis is a neglected tropical disease caused by Trypanosoma brucei (T. brucei) and spread by the tsetse fly in sub-Saharan Africa. The trypanosome relies on heat shock proteins for survival in the insect vector and mammalian host. Heat shock protein 90 (HSP90) plays a crucial role in the stress response at the cellular level. Inhibition of its interactions with chaperones and co-chaperones is being explored as a potential therapeutic target for numerous diseases. This study provides an in silico overview of HSP90 and its co-chaperones in both T. brucei brucei and T. brucei gambiense in relation to human and other trypanosomal species, including non-parasitic Bodo saltans and the insect infecting Crithidia fasciculata. A structural analysis of T. brucei HSP90 revealed differences in the orientation of the linker and C-terminal domain in comparison to human HSP90. Phylogenetic analysis displayed the T. brucei HSP90 proteins clustering into three distinct groups based on subcellular localizations, namely, cytosol, mitochondria, and endoplasmic reticulum. Syntenic analysis of cytosolic HSP90 genes revealed that T. b. brucei encoded for 10 tandem copies, while T. b. gambiense encoded for three tandem copies; Leishmania major (L. major) had the highest gene copy number with 17 tandem copies. The updated information on HSP90 from recently published proteomics on T. brucei was examined for different life cycle stages and subcellular localizations. The results show a difference between T. b. brucei and T. b. gambiense with T. b. brucei encoding a total of twelve putative HSP90 genes, while T. b. gambiense encodes five HSP90 genes. Eighteen putative co-chaperones were identified with one notable absence being cell division cycle 37 (Cdc37). These results provide an updated framework on approaching HSP90 and its interactions as drug targets in the African trypanosome.

Targeting extracellular Hsp90: A unique frontier against cancer

The molecular chaperone Heat Shock Protein-90 (Hsp90) is known to interact with over 300 client proteins as well as regulatory factors (eg. nucleotide and proteins) that facilitate execution of its role as a chaperone and, ultimately, client protein activation. Hsp90 associates transiently with these molecular modulators during an eventful chaperone cycle, resulting in acquisition of flexible structural conformations, perfectly customized to the needs of each one of its client proteins. Due to the plethora and diverse nature of proteins it supports, the Hsp90 chaperone machinery is critical for normal cellular function particularly in response to stress. In diseases such as cancer, the Hsp90 chaperone machinery is hijacked for processes which encompass many of the hallmarks of cancer, including cell growth, survival, immune response evasion, migration, invasion, and angiogenesis. Elevated levels of extracellular Hsp90 (eHsp90) enhance tumorigenesis and the potential for metastasis. eHsp90 has been considered one of the new targets in the development of anti-cancer drugs as there are various stages of cancer progression where eHsp90 function could be targeted. Our limited understanding of the regulation of the eHsp90 chaperone machinery is a major drawback for designing successful Hsp90-targeted therapies, and more research is still warranted.

Targeting Fibronectin to Overcome Remyelination Failure in Multiple Sclerosis: The Need for Brain- and Lesion-Targeted Drug Delivery

Multiple sclerosis (MS) is a neuroinflammatory and neurodegenerative disease with unknown etiology that can be characterized by the presence of demyelinated lesions. Prevailing treatment protocols in MS rely on the modulation of the inflammatory process but do not impact disease progression. Remyelination is an essential factor for both axonal survival and functional neurological recovery but is often insufficient. The extracellular matrix protein fibronectin contributes to the inhibitory environment created in MS lesions and likely plays a causative role in remyelination failure. The presence of the blood-brain barrier (BBB) hinders the delivery of remyelination therapeutics to lesions. Therefore, therapeutic interventions to normalize the pathogenic MS lesion environment need to be able to cross the BBB. In this review, we outline the multifaceted roles of fibronectin in MS pathogenesis and discuss promising therapeutic targets and agents to overcome fibronectin-mediated inhibition of remyelination. In addition, to pave the way for clinical use, we reflect on opportunities to deliver MS therapeutics to lesions through the utilization of nanomedicine and discuss strategies to deliver fibronectin-directed therapeutics across the BBB. The use of well-designed nanocarriers with appropriate surface functionalization to cross the BBB and target the lesion sites is recommended.

Fibronectin isoforms in skeletal development and associated disorders

The extracellular matrix is an intricate and essential network of proteins and non-proteinaceous components that provide a conducive microenvironment for cells to regulate cell function, differentiation, and survival. Fibronectin is one key component in the extracellular matrix that participates in determining cell fate and function crucial for normal vertebrate development. Fibronectin undergoes time dependent expression patterns during stem cell differentiation, providing a unique stem cell niche. Mutations in fibronectin have been recently identified to cause a rare form of skeletal dysplasia with scoliosis and abnormal growth plates. Even though fibronectin has been extensively analyzed in developmental processes, the functional role and importance of this protein and its various isoforms in skeletal development remains less understood. This review attempts to provide a concise and critical overview of the role of fibronectin isoforms in cartilage and bone physiology and associated pathologies. This will facilitate a better understanding of the possible mechanisms through which fibronectin exerts its regulatory role on cellular differentiation during skeletal development. The review discusses the consequences of mutations in fibronectin leading to corner fracture type spondylometaphyseal dysplasia and presents a new outlook towards matrix-mediated molecular pathways in relation to therapeutic and clinical relevance.

The Heat Shock Protein 90 Inhibitor, AT13387, Protects the Alveolo-Capillary Barrier and Prevents HCl-Induced Chronic Lung Injury and Pulmonary Fibrosis

Hydrochloric acid (HCl) exposure causes asthma-like conditions, reactive airways dysfunction syndrome, and pulmonary fibrosis. Heat Shock Protein 90 (HSP90) is a molecular chaperone that regulates multiple cellular processes. HSP90 inhibitors are undergoing clinical trials for cancer and are also being studied in various pre-clinical settings for their anti-inflammatory and anti-fibrotic effects. Here we investigated the ability of the heat shock protein 90 (HSP90) inhibitor AT13387 to prevent chronic lung injury induced by exposure to HCl in vivo and its protective role in the endothelial barrier in vitro. We instilled C57Bl/6J mice with 0.1N HCl (2 µL/g body weight, intratracheally) and after 24 h began treatment with vehicle or AT13387 (10 or 15 mg/kg, SC), administered 3×/week; we analyzed histological, functional, and molecular markers 30 days after HCl. In addition, we monitored transendothelial electrical resistance (TER) and protein expression in a monolayer of human lung microvascular endothelial cells (HLMVEC) exposed to HCl (0.02 N) and treated with vehicle or AT13387 (2 µM). HCl provoked persistent alveolar inflammation; activation of profibrotic pathways (MAPK/ERK, HSP90); increased deposition of collagen, fibronectin and elastin; histological evidence of fibrosis; and a decline in lung function reflected in a downward shift in pressure-volume curves, increased respiratory system resistance (Rrs), elastance (Ers), tissue damping (G), and hyperresponsiveness to methacholine. Treatment with 15 mg/kg AT13387reduced alveolar inflammation, fibrosis, and NLRP3 staining; blocked activation of ERK and HSP90; and attenuated the deposition of collagen and the development of chronic lung injury and airway hyperreactivity. In vitro, AT13387 prevented HCl-induced loss of barrier function and AKT, ERK, and ROCK1 activation, and restored HSP70 and cofilin expression. The HSP90 inhibitor, AT13387, represents a promising drug candidate for chronic lung injury that can be administered subcutaneously in the field, and at low, non-toxic doses.

HSP90 as a regulator of extracellular matrix dynamics

The extracellular matrix (ECM) is a dynamic and organised extracellular network assembled from proteins and carbohydrates exported from the cell. The ECM is critical for multicellular life, providing spatial and temporal cellular cues to maintain tissue homeostasis. Consequently, ECM production must be carefully balanced with turnover to ensure homeostasis; ECM dysfunction culminates in disease. Hsp90 is a molecular chaperone central to protein homeostasis, including in the ECM. Intracellular and extracellular Hsp90 isoforms collaborate to regulate the levels and status of proteins in the ECM via multiple mechanisms. In so doing, Hsp90 regulates ECM dynamics, and changes in Hsp90 levels or activity support the development of ECM-related diseases, like cancer and fibrosis. Consequently, Hsp90 levels may have prognostic value, while inhibition of Hsp90 may have therapeutic potential in conditions characterised by ECM dysfunction.

Cromolyn platform suppresses fibrosis and inflammation, promotes microglial phagocytosis and neurite outgrowth

Neurodegenerative diseases are characterized by chronic neuroinflammation and may perpetuate ongoing fibrotic reactions within the central nervous system. Unfortunately, there is no therapeutic available that treats neurodegenerative inflammation and its sequelae. Here we utilize cromolyn, a mast cell inhibitor with anti-inflammatory capabilities, and its fluorinated analogue F-cromolyn to study fibrosis-related protein regulation and secretion downstream of neuroinflammation and their ability to promote microglial phagocytosis and neurite outgrowth. In this report, RNA-seq analysis shows that administration of the pro-inflammatory cytokine TNF-α to HMC3 human microglia results in a robust upregulation of fibrosis-associated genes. Subsequent treatment with cromolyn and F-cromolyn resulted in reduced secretion of collagen XVIII, fibronectin, and tenascin-c. Additionally, we show that cromolyn and F-cromolyn reduce pro-inflammatory proteins PLP1, PELP1, HSP90, IL-2, GRO-α, Eotaxin, and VEGF-Α, while promoting secretion of anti-inflammatory IL-4 in HMC3 microglia. Furthermore, cromolyn and F-cromolyn augment neurite outgrowth in PC12 neuronal cells in concert with nerve growth factor. Treatment also differentially altered secretion of neurogenesis-related proteins TTL, PROX1, Rab35, and CSDE1 in HMC3 microglia. Finally, iPSC-derived human microglia more readily phagocytose Aβ42 with cromolyn and F-cromolyn relative to controls. We propose the cromolyn platform targets multiple proteins upstream of PI3K/Akt/mTOR, NF-κB, and GSK-3β signaling pathways to affect cytokine, chemokine, and fibrosis-related protein expression.

A native mass spectrometry platform identifies HOP inhibitors that modulate the HSP90-HOP protein-protein interaction

Herein we describe a native mass spectromery protein-peptide model as a competent surrogate for the HOP-HSP90 protein-protein interaction (PPI), application of which led to the qualititive identification of two new peptides capable of in vitro PPI disruption. This proof of concept study offers a viable alternative for PPI inhibitor screening.

Youthful and age-related matreotypes predict drugs promoting longevity

The identification and validation of drugs that promote health during aging ("geroprotectors") are key to the retardation or prevention of chronic age-related diseases. Here, we found that most of the established pro-longevity compounds shown to extend lifespan in model organisms also alter extracellular matrix gene expression (i.e., matrisome) in human cell lines. To harness this observation, we used age-stratified human transcriptomes to define the age-related matreotype, which represents the matrisome gene expression pattern associated with age. Using a "youthful" matreotype, we screened in silico for geroprotective drug candidates. To validate drug candidates, we developed a novel tool using prolonged collagen expression as a non-invasive and in-vivo surrogate marker for Caenorhabditis elegans longevity. With this reporter, we were able to eliminate false-positive drug candidates and determine the appropriate dose for extending the lifespan of C. elegans. We improved drug uptake for one of our predicted compounds, genistein, and reconciled previous contradictory reports of its effects on longevity. We identified and validated new compounds, tretinoin, chondroitin sulfate, and hyaluronic acid, for their ability to restore age-related decline of collagen homeostasis and increase lifespan. Thus, our innovative drug screening approach-employing extracellular matrix homeostasis-facilitates the discovery of pharmacological interventions promoting healthy aging.

Inflammation, Extracellular Matrix Remodeling, and Proteostasis in Tumor Microenvironment

Cancer is a multifaceted and complex pathology characterized by uncontrolled cell proliferation and decreased apoptosis. Most cancers are recognized by an inflammatory environment rich in a myriad of factors produced by immune infiltrate cells that induce host cells to differentiate and to produce a matrix that is more favorable to tumor cells’ survival and metastasis. As a result, the extracellular matrix (ECM) is changed in terms of macromolecules content, degrading enzymes, and proteins. Altered ECM components, derived from remodeling processes, interact with a variety of surface receptors triggering intracellular signaling that, in turn, cancer cells exploit to their own benefit. This review aims to present the role of different aspects of ECM components in the tumor microenvironment. Particularly, we highlight the effect of pro- and inflammatory factors on ECM degrading enzymes, such as metalloproteases, and in a more detailed manner on hyaluronan metabolism and the signaling pathways triggered by the binding of hyaluronan with its receptors. In addition, we sought to explore the role of extracellular chaperones, especially of clusterin which is one of the most prominent in the extracellular space, in proteostasis and signaling transduction in the tumor microenvironment. Although the described tumor microenvironment components have different biological roles, they may engage common signaling pathways that favor tumor growth and metastasis.

The dark-side of the outside: how extracellular heat shock proteins promote cancer

In addition to exerting several essential house-keeping activities in the cell, heat shock proteins (HSPs) are crucial players in a well-structured molecular program activated in response to stressful challenges. Among the different activities carried out by HSPs during emergency, they reach the extracellular milieu, from where they scout the surroundings, regulate extracellular protein activity and send autocrine and paracrine signals. Cancer cells permanently experience stress conditions due to their altered equilibrium and behaviour, and constantly secrete heat shock proteins as a result. Other than supporting anti-tumour immunity, extracellular heat shock proteins (eHSPs), can also exacerbate cancer cell growth and malignancy by sustaining different cancer hallmarks. eHSPs are implicated in extracellular matrix remodelling, resistance to apoptosis, promotion of cell migration and invasion, induction of epithelial to mesenchymal transition, angiogenesis and activation of stromal cells, supporting ultimately, metastasis dissemination. A broader understanding of eHSP activity and contribution to tumour development and progression is leading to new opportunities in the diagnosis and treatment of cancer.

EZH2 knockdown in tamoxifen-resistant MCF-7 cells unravels novel targets for regaining sensitivity towards tamoxifen

BACKGROUND

Acquired resistance to drug involves multilayered genetic and epigenetic regulation. Inhibition of EZH2 has proven to reverse the tamoxifen resistance back to the sensitive state in breast cancer. However, the molecular players involved in EZH2-mediated effects on tamoxifen-resistant MCF-7 cells are unknown. This study was conducted to understand the global change in proteome profile of tamoxifen-resistant MCF-7 breast cancer cells upon EZH2 knockdown.

METHODS

Tamoxifen resistance MCF-7 breast cancer cells were established using increasing concentrations of 4-hydroxy tamoxifen. Using label free proteomics approach, we studied the alteration in total proteome in resistant cells as well as cells transfected with siEZH2 in comparison to sensitive and cells transfected with non-targeting siRNA.

RESULTS

Here, we report list of proteins that were previously not recognized for their role in tamoxifen resistance and hold a close association with breast cancer patient survival. Proteins Annexin A2, CD44, nucleosome assembly protein 1, and lamin A/C were among the most upregulated protein in tamoxifen-resistant cells that were found to be abrogated upon EZH2 knockdown. The study suggests the involvement for various proteins in acquiring resistance towards tamoxifen and anticipates further research for investigating their therapeutic potentials.

CONCLUSION

Overall, we propose that targeting EZH2 or the molecules down the cascade might be helpful in reacquiring sensitivity to tamoxifen in breast cancer.

HSP90 Interacts with the Fibronectin N-terminal Domains and Increases Matrix Formation

Heat shock protein 90 (HSP90) is an evolutionarily conserved chaperone protein that controls the function and stability of a wide range of cellular client proteins. Fibronectin (FN) is an extracellular client protein of HSP90, and exogenous HSP90 or inhibitors of HSP90 alter the morphology of the extracellular matrix. Here, we further characterized the HSP90 and FN interaction. FN bound to the M domain of HSP90 and interacted with both the open and closed HSP90 conformations; and the interaction was reduced in the presence of sodium molybdate. HSP90 interacted with the N-terminal regions of FN, which are known to be important for matrix assembly. The highest affinity interaction was with the 30-kDa (heparin-binding) FN fragment, which also showed the greatest colocalization in cells and accommodated both HSP90 and heparin in the complex. The strength of interaction with HSP90 was influenced by the inherent stability of the FN fragments, together with the type of motif, where HSP90 preferentially bound the type-I FN repeat over the type-II repeat. Exogenous extracellular HSP90 led to increased incorporation of both full-length and 70-kDa fragments of FN into fibrils. Together, our data suggested that HSP90 may regulate FN matrix assembly through its interaction with N-terminal FN fragments.

Fibronectin in Cancer: Friend or Foe

The role of fibronectin (FN) in tumorigenesis and malignant progression has been highly controversial. Cancerous FN plays a tumor-suppressive role, whereas it is pro-metastatic and associated with poor prognosis. Interestingly, FN matrix deposited in the tumor microenvironments (TMEs) promotes tumor progression but is paradoxically related to a better prognosis. Here, we justify how FN impacts tumor transformation and subsequently metastatic progression. Next, we try to reconcile and rationalize the seemingly conflicting roles of FN in cancer and TMEs. Finally, we propose future perspectives for potential FN-based therapeutic strategies.

A novel pan-cancer biomarker plasma heat shock protein 90alpha and its diagnosis determinants in clinic

A sensitive and specific diagnosis biomarker, in principle scalable to most cancer types, is needed to reduce the prevalent cancer mortality. Meanwhile, the investigation of diagnosis determinants of a biomarker will facilitate the interpretation of its screening results in clinic. Here we design a large-scale (1558 enrollments), multicenter (multiple hospitals), and cross-validation (two datasets) clinic study to validate plasma Hsp90α quantified by ELISA as a pan-cancer biomarker. ROC curve shows the optimum diagnostic cutoff is 69.19 ng/mL in discriminating various cancer patients from all controls (AUC 0.895, sensitivity 81.33% and specificity 81.65% in test cohort; AUC 0.893, sensitivity 81.72% and specificity 81.03% in validation cohort). Similar results are noted in detecting early-stage cancer patients. Plasma Hsp90α maintains also broad-spectrum for cancer subtypes, especially with 91.78% sensitivity and 91.96% specificity in patients with AFP-limited liver cancer. In addition, we demonstrate levels of plasma Hsp90α are determined by ADAM10 expression, which will affect Hsp90α content in exosomes. Furthermore, Western blotting and PRM-based quantitative proteomics identify that partial false ELISA-negative patients secret high levels of plasma Hsp90α. Mechanism analysis reveal that TGFβ-PKCγ gene signature defines a distinct pool of hyperphosphorylated Hsp90α at Theronine residue. In clinic, a mechanistically relevant population of false ELISA-negative patients express also higher levels of PKCγ. In sum, plasma Hsp90α is a novel pan-cancer diagnosis biomarker, and cancer diagnosis with plasma Hsp90α is particularly effective in those patients with high expression of ADAM10, but may be insufficient to detect the patients with low ADAM10 and those with hyperphosphorylated Hsp90α.

COL6A1 knockdown suppresses cell proliferation and migration in human aortic vascular smooth muscle cells

Vascular smooth muscle cell (VSMC) migration is an important pathophysiological signature of neointimal hyperplasia. The aim of the present study was to investigate the effects of collagen type VI α1 chain (COL6A1) on VSMC migration. COL6A1 expression was silenced in platelet-derived growth factor (PDGF-BB)-stimulated VSMCs. Cell counting kit-8, wound healing and Transwell assays were used to measure cell viability, migration and invasion, respectively. Reverse transcription-quantitative PCR and western blot analysis were performed to analyze the expression of factors associated with metastasis. COL6A1 silencing attenuated PDGF-BB-induced increases in cell viability and invasive abilities of VSMCs, in addition to partially reversing the increased expression of fibronectin (FN), matrix metalloproteinase (MMP)-2 and MMP-9 induced by PDGF-BB stimulation. The silencing of COL6A also overturned PDGF-BB-induced reduction in tissue inhibitor of metalloproteinase 2 expression in VSMCs. PDGF-BB activated the AKT/mTOR pathway, which was also inhibited by COL6A1 knockdown. Taken together, these findings suggest that COL6A1 silencing inhibited VSMC viability and migration by inhibiting AKT/mTOR activation.

Heat Shock Proteins (HSPs): A Novel Target for Cancer Metastasis Prevention

Background:

Heat shock proteins (HSPs) are predominant molecular chaperones which are actively involved in the protein folding; which is essential in protecting the structure and functioning of proteins during various stress conditions. Though HSPs have important physiological roles, they have been well known for their roles in various pathogenic conditions such as carcinogenesis; however, limited literature has consolidated its potential as an anti-metastatic drug target.

Objectives:

The present review outlines the role of different HSPs on cancer progression and metastasis; possible role of HSP inhibitors as anti-neoplastic agents is also discussed.

Methods:

The data were collected from PubMed/Medline and other reputed journal databases. The literature that was too old and had no significant role to the review was then omitted.

Results:

Despite their strong physiological functions, HSPs are considered as good markers for cancer prognosis and diagnosis. They have control over survival, proliferation and progression events of cancer including drug resistance, metastasis, and angiogenesis. Since, neoplastic cells are more dependent on HSPs for survival and proliferation, the selectivity and specificity of HSP-targeted cancer drugs remain high. This has made various HSPs potential clinical and experimental targets for cancer prevention. An array of HSP inhibitors has been in trials and many others are in experimental conditions as anticancer and anti-metastatic agents. Several natural products are also being investigated for their efficacy for anticancer and anti-metastatic agents by modulating HSPs.

Conclusion:

Apart from their role as an anticancer drug target, HSPs have shown to be promising targets for the prevention of cancer progression. Extensive studies are required for the use of these molecules as anti-metastatic agents. Further studies in this line may yield specific and effective antimetastatic agents.

Cell surface heparan sulfate proteoglycans are involved in the extracellular Hsp90-stimulated migration and invasion of cancer cells

The extracellular heat shock protein 90 (Hsp90) is known to participate in cell migration and invasion. Recently, we have shown that cell surface heparan sulfate proteoglycans (HSPGs) are involved in the binding and anchoring of extracellular Hsp90 to the plasma membrane, but the biological relevance of this finding was unclear. Here, we demonstrated that the digestion of heparan sulfate (HS) moieties of HSPGs with a heparinase I/III blend and the metabolic inhibition of the sulfation of HS chains by sodium chlorate considerably impair the migration and invasion of human glioblastoma A-172 and fibrosarcoma HT1080 cells stimulated by extracellular native Hsp90. Heparin, a polysaccharide closely related to HS, also reduced the Hsp90-stimulated migration and invasion of cells. Phorbol 12-myristate 13-acetate, an intracellular inducer of cell motility bypassing the ligand activation of receptors, restored the basal migration of heparinase- and chlorate-treated cells almost to the control level, suggesting that the cell motility machinery was insignificantly affected in cells with degraded and undersulfated HS chains. On the other hand, the downstream phosphorylation of AKT in response to extracellular Hsp90 was substantially impaired in heparinase- and chlorate-treated cells as compared to untreated cells. Taken together, our results demonstrated for the first time that cell surface HSPGs play an important role in the migration and invasion of cancer cells stimulated by extracellular Hsp90 and that plasma membrane-associated HSPGs are required for the efficient transmission of signal from extracellular Hsp90 into the cell.

Fibronectin aggregates promote features of a classically and alternatively activated phenotype in macrophages

BACKGROUND

Means to promote endogenous remyelination in multiple sclerosis (MS) benefit from insights into the role of inhibitory molecules that preclude remyelination. Fibronectin assembles into aggregates in MS, which impair oligodendrocyte differentiation and remyelination. Microglia and macrophages are required for complete remyelination and normally switch from a pro-inflammatory classical phenotype upon demyelination to a supportive alternative phenotype during remyelination. Here, we investigated the role of fibronectin aggregates in modulating microglia and macrophage behavior and phenotypes.

METHODS

Bone marrow-derived macrophages and microglia from newborn rats were exposed to (a) plasma fibronectin coatings; (b) coatings of deoxycholate-insoluble fibronectin aggregates; (c) interferon-γ (IFNγ) treatment, as an inducer of the pro-inflammatory classically activated phenotype; (d) interleukin-4 (IL-4) treatment, to promote the pro-regenerative anti-inflammatory alternatively activated phenotype; or (e) left unstimulated on uncoated plastic. To examine the in vitro effects of the different stimulations on cell behavior and phenotype, proliferation, phagocytosis, morphology, and pro- and anti-inflammatory features were assessed.

RESULTS

In line with a classically activated phenotype, exposure of microglia and macrophages to both plasma fibronectin and fibronectin aggregates induced an amoeboid morphology and stimulated phagocytosis by macrophages. Furthermore, as observed upon IFNγ treatment, coatings of aggregated, but not plasma fibronectin, promoted nitric oxide release by microglia and macrophages. Remarkably, fibronectin aggregates induced nitric oxide release in an integrin-independent manner. In addition, fibronectin aggregates, but not plasma fibronectin, increased the expression of arginase-1, similarly as observed upon treatment with IL-4. Proteomic analysis revealed that aggregates of fibronectin act as a scaffold for other proteins, including Hsp70 and thrombospondin-1, which may clarify the induction of both pro-inflammatory and anti-inflammatory features in macrophages cultured on fibronectin aggregate, but not plasma fibronectin coatings.

CONCLUSIONS

Macrophages and microglia grown on aggregated fibronectin coatings adopt a distinct phenotype compared to plasma fibronectin coatings, showing pro-inflammatory and anti-inflammatory features. Therefore, the pathological fibronectin aggregates in MS lesions may impair remyelination by promoting and/or retaining several classically activated phenotypic features in microglia and macrophages.

LRP1 is required for novobiocin-mediated fibronectin turnover

Fibronectin (FN) plays a major role in the stability and organization of the extracellular matrix (ECM). We have previously demonstrated that FN interacts directly with Hsp90, as well as showing that the Hsp90 inhibitor novobiocin results in FN turnover via a receptor mediated process. However, the receptor involved has not been previously identified. LRP1 is a ubiquitous receptor responsible for the internalisation of numerous ligands that binds both Hsp90 and FN, and therefore we investigated whether LRP1 was involved in novobiocin-mediated FN turnover. FN, LRP1 and Hsp90 could be isolated in a common complex, and inhibition of Hsp90 by novobiocin increased the colocalisation of FN and LRP1. Novobiocin induced an increase (at low concentrations) followed by a loss of FN that was primarily derived from extracellular matrix-associated FN and led to a concomitant increase in intracellular FN. The effect of novobiocin was specific to LRP1-expressing cells and could be recapitulated by an LRP1 blocking antibody and the allosteric C-terminal Hsp90 inhibitor SM253, but not the N-terminal inhibitor geldanamycin. Together these data suggest that LRP1 is required for FN turnover in response to Hsp90 inhibition by novobiocin, which may have unintended physiological consequences in contexts where C-terminal Hsp90 inhibition is to be used therapeutically.

Heat shock proteins as modulators and therapeutic targets of chronic disease: an integrated perspective

Many heat shock proteins (HSPs) are essential to survival as a consequence of their role as molecular chaperones, and play a critical role in maintaining cellular proteostasis by integrating the fundamental processes of protein folding and degradation. HSPs are arguably among the most prominent classes of proteins that have been broadly linked to many human disorders, with changes in their expression profile and/or intracellular/extracellular location now being described as contributing to the pathogenesis of a number of different diseases. Although the concept was initially controversial, it is now widely accepted that HSPs have additional biological functions over and above their role in proteostasis (so-called 'protein moonlighting'). Most importantly, these new insights are enlightening our understanding of biological processes in health and disease, and revealing novel and exciting therapeutic opportunities. This theme issue draws on therapeutic insights from established research on HSPs in cancer and other non-communicable disorders, with an emphasis on how the intracellular function of HSPs contrasts with their extracellular properties and function, and interrogates their potential diagnostic and therapeutic value to the prevention, management and treatment of chronic diseases.This article is part of the theme issue 'Heat shock proteins as modulators and therapeutic targets of chronic disease: an integrated perspective'.

Immunosurveillance of cancer and the heat shock protein-CD91 pathway

The intracellular functions of heat shock proteins (HSPs) as chaperones of macromolecules are well known. Current observations point to a role of these chaperones in initiating and modulating immune responses to tumors via receptor(s) on dendritic cells. In this article we provide an insight into, and a basis for, the importance of these HSP-mediated immune responses in rejecting nascent and emerging tumors.

Fibronectin is a stress responsive gene regulated by HSF1 in response to geldanamycin

Fibronectin is an extracellular matrix glycoprotein with key roles in cell adhesion and migration. Hsp90 binds directly to fibronectin and Hsp90 depletion regulates fibronectin matrix stability. Where inhibition of Hsp90 with a C-terminal inhibitor, novobiocin, reduced the fibronectin matrix, treatment with an N-terminal inhibitor, geldanamycin, increased fibronectin levels. Geldanamycin treatment induced a stress response and a strong dose and time dependent increase in fibronectin mRNA via activation of the fibronectin promoter. Three putative heat shock elements (HSEs) were identified in the fibronectin promoter. Loss of two of these HSEs reduced both basal and geldanamycin-induced promoter activity, as did inhibition of the stress-responsive transcription factor HSF1. Binding of HSF1 to one of the putative HSE was confirmed by ChIP under basal conditions, and occupancy shown to increase with geldanamycin treatment. These data support the hypothesis that fibronectin is stress-responsive and a functional HSF1 target gene. COLA42 and LAMB3 mRNA levels were also increased with geldanamycin indicating that regulation of extracellular matrix (ECM) genes by HSF1 may be a wider phenomenon. Taken together, these data have implications for our understanding of ECM dynamics in stress-related diseases in which HSF1 is activated, and where the clinical application of N-terminal Hsp90 inhibitors is intended.

Targeting the Tumor Environment in Squamous Cell Carcinoma of the Head and Neck

OPINION STATEMENT

The survival rate for patients with advanced stages of squamous cell carcinoma of the head and neck (SCCHN) remains poor despite multimodal treatment options. Cetuximab, an anti-EGFR inhibitor, is the only FDA-approved targeted agent for this disease. Recent findings have implicated modifications of the microenvironment and, consequently, phenotypical modifications of the cancer cell, in treatment resistance mechanisms. For many years, cancer research has focused mainly on targetable sites on or inside the cancer cell. Nowadays, in preclinical and clinical studies, a greater emphasis is being placed on drugs that target the tumor microenvironment. Potential targets relate to tumor vascularization, immunology, extracellular matrix components, or cancer-associated fibroblasts. The combination of these new agents with standard treatment options is of particular interest to overcome resistance mechanisms and/or to increase treatment efficacy. Whereas antiangiogenic agents show poor clinical activity, immunotherapy seems to be a more promising tool with an objective response rate (ORR) of 20 % in patients with recurrent and/or metastatic squamous cell carcinoma (R/M SCC). Other targets, located inside the extracellular matrix or on cancer associated fibroblasts, are under preclinical investigation. These new agents all need to be tested in clinical trials alone, or in combination with standard treatment modalities, based on preclinical data. To increase our knowledge of the complex network between the cancer cell and its environment, preclinical studies should consider co-culture models, and clinical studies should incorporate a translational research objective.

Extracellular Hsp90 and TGFβ regulate adhesion, migration and anchorage independent growth in a paired colon cancer cell line model

Background

Tumour metastasis remains the major cause of death in cancer patients and, to date, the mechanism and signalling pathways governing this process are not completely understood. The TGF-β pathway is the most commonly mutated pathway in cancer, however its role in cancer progression is controversial as it can function as both a promoter and a suppressor of metastasis. Although previous studies have suggested a role for the molecular chaperone Hsp90 in regulating the TGF-β pathway, the level at which this occurs as well as the consequences in terms of colon cancer metastasis are unknown.

Methods

The paired SW480 and SW620 colon cancer cell lines, derived from a primary tumour and its lymph node metastasis, respectively, were used as an in vitro model to study key cellular processes required for metastasis. The status of the TGF-β pathway was examined in these cells using ELISA, flow cytometry, western blot analysis and confocal microscopy. Furthermore, the effect of addition or inhibition of the TGF-β pathway and Hsp90 on adhesion, migration and anchorage-independent growth, was determined in the cell lines.

Results

When comparing the canonical TGF-β1 pathway in the genetically paired cell lines our data suggests that this pathway may be constitutively active in the SW620 metastasis-derived cell line and not the SW480 primary tumour-derived line. In addition, we report that, when present in combination, TGF-β1 and Hsp90β stimulate anchorage-independent growth, reduce adhesion and stimulate migration. This effect is potentiated by inhibition of the TGF-β1 receptor and occurs via an alternate TGF-β1 pathway, mediated by αvβ6 integrin. Interestingly, in the SW620 cells, activation of this alternate TGF-β1 signalling machinery does not appear to require inhibition of the canonical TGF-β1 receptor, which would allow them to respond more effectively to the pro-metastasis stimulus of a combination of Hsp90β and TGF-β1 and this could account for the increased migratory capacity of these cells.

Conclusions

In this study we report an apparent synergy between TGF-β1 and Hsp90β in stimulating migratory behaviour of colon cancer cells when signalling occurs via αvβ6 integrin as opposed to the canonical TGF-β1 pathway.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-017-3190-z) contains supplementary material, which is available to authorized users.

Cell surface heparan sulfate proteoglycans are involved in the binding of Hsp90α and Hsp90β to the cell plasma membrane

Extracellular membrane-bound and secreted heat shock protein 90 (Hsp90) is known to be involved in cell motility and invasion. The mechanism of Hsp90 anchoring to the plasma membrane remains obscure. We showed that treatment of human glioblastoma A-172 and fibrosarcoma HT1080 cells with sodium chlorate, heparinase, and heparin causes a prominent loss of 2 Hsp90 cytosolic isoforms, Hsp90α and Hsp90β, from the cell surface and strongly inhibits the binding of exogenous Hsp90 to cells. We revealed that Hsp90α and Hsp90β are partly colocalized with heparan sulfate proteoglycans (HSPGs) on the cell surface and that this colocalization was sensitive to heparin. The results demonstrate that cell surface HSPGs are involved in the binding/anchoring of Hsp90α and Hsp90β to the plasma membrane.

Targeting highly expressed extracellular HSP90 in breast cancer stem cells inhibits tumor growth in vitro and in vivo

Breast cancer stem cells (BCSC) have been identified in breast carcinoma as CD44(+)/CD24(-/low) cells, which display tumorigenic activity and have the ability to self-renew, differentiate and metastasize. Previous studies showed that extracellular HSP90 (eHSP90) participates in the invasion and metastatic processes of various cancers including breast cancer. Here, we show for the first time that eHSP90 is over-expressed in mammosphere cultures that are derived from the MDA-MB-231, MDA-MB-453 and MCF-7 breast cancer cell lines. These mammospheres are highly enriched in cells of the CD44(+)/CD24(-/low) BCSC phenotype and additionally show high expression of the BCSC markers CD49f and Sox2. Thus our results indicate that eHSP90 represents a potential novel BCSC marker. Moreover, we present evidence that eHSP90 is functionally involved in BCSC activity in vitro and in vivo. Selective neutralization of eHSP90, using the monoclonal antibody mAb 4C5, has the capacity to inhibit stem cell activity in vitro because the formation of mammosphere-derived colonies is dramatically reduced in its presence. In vivo, the treatment of mice with mAb4C5 using a prophylactic protocol, significantly inhibited the primary growth of MDA-MB-231 and mammosphere-derived tumors. More importantly, administration of this antibody in a therapeutic protocol caused a statistically significant regression of established tumors derived from MDA-MB-231 originating mammospheres. Tumor regression was even greater when mAb 4C5 was administered in combination with paclitaxel. Overall, our findings implicate eHSP90 as a potential novel BCSC biomarker. Moreover they show that eHSP90 participates in BCSC-derived primary tumor growth. Finally, we provide additional support for the possible therapeutic value of mAb4C5 in the treatment of breast cancer.

Emerging Roles of Extracellular Hsp90 in Cancer

Heat shock protein 90 (Hsp90) is a highly expressed chaperone that modulates the function and stability of hundreds of cellular client proteins. In this capacity, Hsp90 impacts human health in myriad ways and it is accordingly a high-interest molecular target in the oncology setting. This interest has led to a large number of clinical trials to evaluate the potential benefit of Hsp90 inhibitors in cancer treatment and, more recently, in combination with chemotherapeutic agents. Although these studies are still ongoing, some issues have arisen, such as toxicity effects associated with administration of these agents. We and others have identified a novel role for Hsp90 outside of cancer cells. This extracellular Hsp90 (eHsp90) was shown to be critical for the regulation of tumor invasiveness and metastasis, central processes associated with cancer lethality. Since these initial papers, a considerable cohort of studies has expanded upon this role, implicating eHsp90 in the activation of a number of proteins that support tumor cell invasion. As eHsp90 is preferentially detected on the surface of tumor cells, and within their surrounding microenvironment, it is possible that drugs capable of selectively targeting eHsp90 may exploit this differential expression. This selectivity may, in turn, enable treatment regimens with reduced target-related toxicity. This review will focus on our current understanding of eHsp90, particularly in cancer, and we will discuss the relevance of eHsp90 as a biomarker for invasive cancer and its potential as a drug target.

Quantitative tissue proteomic investigation of invasive ductal carcinoma of breast with luminal B HER2 positive and HER2 enriched subtypes towards potential diagnostic and therapeutic biomarkers

Worldwide, breast cancer is one of the frequently diagnosed cancers in women with high mortality if not diagnosed at early stage. Although biomarker discoveries through various proteomic approaches have been studied in breast cancer, a limited number of studies have explored the invasive ductal carcinoma with Luminal B HER2 positive (LB) and HER2 enriched (HE) subtypes. The present study employed the complementary quantitative proteomic approaches to find a panel of markers that could discriminate LB and HE subtypes as well as early (ES) and late stages (LS) of these subtypes. A total of 67 and 68 differentially expressed proteins were identified by DIGE for the subtype and stage wise categories, respectively. Multivariate statistical analysis was employed to identify the set of most significant proteins, which could discriminate between these two subtypes and also early and late stages under study. Immunoblotting and MRM based validation in a separate cohort of samples confirmed that panel of biosignatures for LB are APOA1, GELS, HS90B, EF1A1, NHRF1 and PRDX3 and for HE are PRDX1, CATD, CALR, ATPB and CH60. For the diagnosis of early and late stages the potential markers are TPM4, CATD, PRDX3, ANXA3, HSPB1 and CALR, TRFE, GELS, CH60, CAPG, NHRF1, 1433G, GRP78 respectively.

Functions of heat shock proteins in pathways of the innate and adaptive immune system

For more than 50 years, heat shock proteins (HSPs) have been studied for their role in protecting cells from elevated temperature and other forms of stress. More recently, several roles have been ascribed to HSPs in the immune system. These include intracellular roles in Ag presentation and expression of innate receptors, as well as extracellular roles in tumor immunosurveillance and autoimmunity. Exogenously administered HSPs can elicit a variety of immune responses that have been used in immunotherapy of cancer, infectious diseases, and autoimmune disease.

Extracellular molecules involved in cancer cell invasion

Nowadays it is perfectly clear that understanding and eradicating cancer cell invasion and metastasis represent the crucial, definitive points in cancer therapeutics. During the last two decades there has been a great interest in the understanding of the extracellular molecular mechanisms involved in cancer cell invasion. In this review, we highlight the findings concerning these processes, focusing in particular on extracellular molecules, including extracellular matrix proteins and their receptors, growth factors and their receptors, matrix metalloproteinases and extracellular chaperones. We report the molecular mechanisms underlying the important contribution of this pool of molecules to the complex, multi-step phenomenon of cancer cell invasion.

Endoplasmic reticulum chaperones and their roles in the immunogenicity of cancer vaccines

The endoplasmic reticulum (ER) is a major site of passage for proteins en route to other organelles, to the cell surface, and to the extracellular space. It is also the transport route for peptides generated in the cytosol by the proteasome into the ER for loading onto major histocompatibility complex class I (MHC I) molecules for eventual antigen presentation at the cell surface. Chaperones within the ER are critical for many of these processes; however, outside the ER certain of those chaperones may play important and direct roles in immune responses. In some cases, particular ER chaperones have been utilized as vaccines against tumors or infectious disease pathogens when purified from tumor tissue or recombinantly generated and loaded with antigen. In other cases, the cell surface location of ER chaperones has implications for immune responses as well as possible tumor resistance. We have produced heat-shock protein/chaperone protein-based cancer vaccines called “chaperone-rich cell lysate” (CRCL) that are conglomerates of chaperones enriched from solid tumors by an isoelectric focusing technique. These preparations have been effective against numerous murine tumors, as well as in a canine with an advanced lung carcinoma treated with autologous CRCL. We also published extensive proteomic analyses of CRCL prepared from human surgically resected tumor samples. Of note, these preparations contained at least 10 ER chaperones and a number of other residents, along with many other chaperones/heat-shock proteins. Gene ontology and network analyses utilizing these proteins essentially recapitulate the antigen presentation pathways and interconnections. In conjunction with our current knowledge of cell surface/extracellular ER chaperones, these data collectively suggest that a systems-level view may provide insight into the potent immune stimulatory activities of CRCL with an emphasis on the roles of ER components in those processes.

Studying protein-protein interactions using surface plasmon resonance

Protein-protein interactions regulate many important cellular processes, including carbohydrate and lipid metabolism, cell cycle and cell death regulation, protein and nucleic acid metabolism, signal transduction, and cellular architecture. A complete understanding of cellular function depends on full characterization of the complex network of cellular protein-protein interactions, including measurements of their kinetic and binding properties. Surface plasmon resonance (SPR) is one of the commonly used technologies for detailed and quantitative studies of protein-protein interactions and determination of their equilibrium and kinetic parameters. SPR provides excellent instrumentation for a label-free, real-time investigation of protein-protein interactions. This chapter details the experimental design and proper use of the instrumentation for a kinetic experiment. It will provide readers with basic theory, assay setup, and the proper way of reporting this type of results with practical tips useful for SPR-based studies. A generic protocol for immobilizing ligands using amino coupling chemistry, also useful if an antibody affinity capture approach is used, performing kinetic studies, and collecting and analyzing data is described.

Fibronectin predicts the outcome of acute-on-chronic hepatitis B liver failure

BACKGROUND

Acute-on-chronic hepatitis B liver failure (ACHBLF) is a serious condition with varied etiologies and manifestations, and is associated with a high mortality rate. Fibronectin is involved in a number of biological processes, including cellular adhesion, motility, differentiation, apoptosis, hemostasis, wound healing and ischemic injury. Serum fibronectin concentrations may provide prognostic information in ACHBLF; however, as a prognostic marker of mortality in patients with ACHBLF, it needs further validation.

METHODS

The aim of this study was to examine whether admission levels of fibronectin in ACHBLF patients are correlated with outcomes. In this prospective study, 78 ACHBLF patients were compared to 70 matched healthy controls. Fibronectin levels were determined using a commercial enzyme-linked immunosorbent assay kit to determine the prognostic value of fibronectin levels on admission.

RESULTS

The median (range) fibronectin level at admission for ACHBLF patients was significantly reduced compared with that of healthy controls (142 [62-275] mg/l vs 265 [190-346] mg/l, respectively; p<0.001). Fibronectin levels were significantly higher in surviving patients than in those who died (155 [70-275] mg/l vs 119 [62-235] mg/l; p=0.020). Receiver operating characteristic curve analysis showed that a cut-off level of 135 mg/l was the best prognostic indicator, yielding positive and negative predictive values of 60% (18/30) and 71% (30/42), respectively.

CONCLUSIONS

Our results suggested that decreased serum fibronectin levels in patients with ACHBLF were correlated to hepatic injury and inflammation. However, because of the lack of specificity, the use of fibronectin as an independent prognostic indicator is limited.

The double-edged sword: conserved functions of extracellular hsp90 in wound healing and cancer

Heat shock proteins (Hsps) represent a diverse group of chaperones that play a vital role in the protection of cells against numerous environmental stresses. Although our understanding of chaperone biology has deepened over the last decade, the “atypical” extracellular functions of Hsps have remained somewhat enigmatic and comparatively understudied. The heat shock protein 90 (Hsp90) chaperone is a prototypic model for an Hsp family member exhibiting a duality of intracellular and extracellular functions. Intracellular Hsp90 is best known as a master regulator of protein folding. Cancers are particularly adept at exploiting this function of Hsp90, providing the impetus for the robust clinical development of small molecule Hsp90 inhibitors. However, in addition to its maintenance of protein homeostasis, Hsp90 has also been identified as an extracellular protein. Although early reports ascribed immunoregulatory functions to extracellular Hsp90 (eHsp90), recent studies have illuminated expanded functions for eHsp90 in wound healing and cancer. While the intended physiological role of eHsp90 remains enigmatic, its evolutionarily conserved functions in wound healing are easily co-opted during malignancy, a pathology sharing many properties of wounded tissue. This review will highlight the emerging functions of eHsp90 and shed light on its seemingly dichotomous roles as a benevolent facilitator of wound healing and as a sinister effector of tumor progression.