Distinguishing integral and receptor-bound heat shock protein 70 (Hsp70) on the cell surface by Hsp70-specific antibodies

The Interplay between Heat Shock Proteins and Cancer Pathogenesis: A Novel Strategy for Cancer Therapeutics

Heat shock proteins (HSPs) are developmentally conserved families of protein found in both prokaryotic and eukaryotic organisms. HSPs are engaged in a diverse range of physiological processes, including molecular chaperone activity to assist the initial protein folding or promote the unfolding and refolding of misfolded intermediates to acquire the normal or native conformation and its translocation and prevent protein aggregation as well as in immunity, apoptosis, and autophagy. These molecular chaperonins are classified into various families according to their molecular size or weight, encompassing small HSPs (e.g., HSP10 and HSP27), HSP40, HSP60, HSP70, HSP90, and the category of large HSPs that include HSP100 and ClpB proteins. The overexpression of HSPs is induced to counteract cell stress at elevated levels in a variety of solid tumors, including anticancer chemotherapy, and is closely related to a worse prognosis and therapeutic resistance to cancer cells. HSPs are also involved in anti-apoptotic properties and are associated with processes of cancer progression and development, such as metastasis, invasion, and cell proliferation. This review outlines the previously mentioned HSPs and their significant involvement in diverse mechanisms of tumor advancement and metastasis, as well as their contribution to identifying potential targets for therapeutic interventions.

Prediction of prognosis and immune landscape in cervical cancer based on heat shock protein-related genes

Objective: Heat shock proteins (HSPs) play key roles in the malignant transformation and progression of many tumors. However, the effectiveness of using HSP-related genes to predict the prognosis of patients with cervical cancer (CC) remains elusive. We aimed to delineate the prognosis and biological significance of HSP-related genes in CC. Methods: We collected the transcriptional and clinical data of CC patients from The Cancer Genome Atlas (TCGA) and searched for HSP-related genes in the literature. LASSO and univariate/multivariate Cox regression analyses were utilized to screen genes; 12 genes were found to be related to CC survival, and a prediction model was built. The effectiveness of the model was confirmed using TCGA and GEO, and it was found to be an independent predictor of CC. The nomogram is plotted. The prognostic model was further visualized using calibration curves, which showed good agreement with the predicted outcomes at 1-, 3, and 5 years. Results: We found that low-risk patients had higher immune cell infiltration and stronger immune function, and according to the immunophenoscore and TIDE scores, the low-risk group tended to respond more to immunotherapy. Additionally, we used the GDSC database to predict drug sensitivity in patients with different prognostic risks. Conclusion: In summary, we built a good model to help predict the prognosis of CC patients and provide a reference for personalized treatment and medication for different patients.

The multifunction of HSP70 in cancer: Guardian or traitor to the survival of tumor cells and the next potential therapeutic target

Heat shock protein 70 (HSP70) is a highly conserved protein composed of nucleotide-binding domains (NBD) and C-terminal substrate binding domain (SBD) that can function as a "molecular chaperone". HSP70 was discovered to directly or indirectly play a regulatory role in both internal and external apoptosis pathways. Studies have shown that HSP70 can not only promote tumor progression, enhance tumor cell resistance and inhibit anticancer effects but also induce an anticancer response by activating immune cells. In addition, chemotherapy, radiotherapy and immunotherapy for cancer may be affected by HSP70, which has shown promising potential as an anticancer drug. In this review, we summarized the molecular structure and mechanism of HSP70 and discussed the dual effects of HSP70 on tumor cells and the possibility and potential methods of using HSP70 as a target to treat cancer.

Forcing the Antitumor Effects of HSPs Using a Modulated Electric Field

The role of Heat Shock Proteins (HSPs) is a “double-edged sword” with regards to tumors. The location and interactions of HSPs determine their pro- or antitumor activity. The present review includes an overview of the relevant functions of HSPs, which could improve their antitumor activity. Promoting the antitumor processes could assist in the local and systemic management of cancer. We explore the possibility of achieving this by manipulating the electromagnetic interactions within the tumor microenvironment. An appropriate electric field may select and affect the cancer cells using the electric heterogeneity of the tumor tissue. This review describes the method proposed to effect such changes: amplitude-modulated radiofrequency (amRF) applied with a 13.56 MHz carrier frequency. We summarize the preclinical investigations of the amRF on the HSPs in malignant cells. The preclinical studies show the promotion of the expression of HSP70 on the plasma membrane, participating in the immunogenic cell death (ICD) pathway. The sequence of guided molecular changes triggers innate and adaptive immune reactions. The amRF promotes the secretion of HSP70 also in the extracellular matrix. The extracellular HSP70 accompanied by free HMGB1 and membrane-expressed calreticulin (CRT) form damage-associated molecular patterns encouraging the dendritic cells’ maturing for antigen presentation. The process promotes killer T-cells. Clinical results demonstrate the potential of this immune process to trigger a systemic effect. We conclude that the properly applied amRF promotes antitumor HSP activity, and in situ, it could support the tumor-specific immune effects produced locally but acting systemically for disseminated cells and metastatic lesions.

Integrated Multiomics Analysis of Salivary Exosomes to Identify Biomarkers Associated with Changes in Mood States and Fatigue

Fatigue and other deleterious mood alterations resulting from prolonged efforts such as a long work shift can lead to a decrease in vigilance and cognitive performance, increasing the likelihood of errors during the execution of attention-demanding activities such as piloting an aircraft or performing medical procedures. Thus, a method to rapidly and objectively assess the risk for such cognitive fatigue would be of value. The objective of the study was the identification in saliva-borne exosomes of molecular signals associated with changes in mood and fatigue that may increase the risk of reduced cognitive performance. Using integrated multiomics analysis of exosomes from the saliva of medical residents before and after a 12 h work shift, we observed changes in the abundances of several proteins and miRNAs that were associated with various mood states, and specifically fatigue, as determined by a Profile of Mood States questionnaire. The findings herein point to a promising protein biomarker, phosphoglycerate kinase 1 (PGK1), that was associated with fatigue and displayed changes in abundance in saliva, and we suggest a possible biological mechanism whereby the expression of the PGK1 gene is regulated by miR3185 in response to fatigue. Overall, these data suggest that multiomics analysis of salivary exosomes has merit for identifying novel biomarkers associated with changes in mood states and fatigue. The promising biomarker protein presents an opportunity for the development of a rapid saliva-based test for the assessment of these changes.

The interaction of heat shock proteins with cellular membranes: a historical perspective

The interaction of heat shock proteins (HSP) with cellular membranes has been an enigmatic process, initially observed by morphological studies, inferred during the purification of HSP70s, and confirmed after the detection of these proteins on the surface of cancer cells and their insertion into artificial lipid bilayers. Today, the association of several HSP with lipid membranes is well established. However, the mechanisms for membrane insertion have been elusive. There is conclusive evidence indicating that HSP70s have a great selectivity for negatively charged phospholipids, whereas other HSP have a broader spectrum of lipid specificity. HSP70 also oligomerizes upon membrane insertion, forming ion conductance channels. The functional role of HSP70 lipid interactions appears related to membrane stabilization that may play a role during cell membrane biogenesis. They could also play a role as membrane chaperones as well as during endocytosis, microautophagy, and signal transduction. Moreover, HSP membrane association is a key component in the extracellular export of these proteins. The presence of HSP70 on the surface of cancer cells and its interaction with lysosome membranes have been envisioned as potential therapeutic targets. Thus, the biology and function of HSP membrane association are reaching a new level of excitement. This review is an attempt to preserve the recollection of the pioneering contributions of many investigators that have participated in this endeavor.

A new antisarcoma strategy: multisubtype heat shock protein/peptide immunotherapy combined with PD-L1 immunological checkpoint inhibitors

Osteosarcoma, a common malignant tumor in orthopedics, often has a very poor prognosis after lung metastasis. Immunotherapy has not achieved much progress in the treatment because of the characteristics of solid tumors and immune environment of osteosarcoma. The tumor environment is rather essential for sarcoma treatment. Our previous study demonstrated that heat shock proteins could be used as antitumor vaccines by carrying tumor antigen peptides, and we hypothesize that an anti-osteosarcoma effect may be increased with an immune check point inhibitor (PD-L1 inhibitor) as a combination treatment strategy. The present study prepared a multisubtype mixed heat shock protein osteosarcoma vaccine (mHSP/peptide vaccine) and concluded that the mHSP/peptide vaccine was more effective than a single subtype heat shock protein, like Grp94. Therefore, we used the mHSP/peptide vaccine in combination with a PD-L1 inhibitor to treat osteosarcoma, and the deterioration of osteosarcoma was effectively hampered. The mechanism of combined therapy was investigated, and AKT expression participates with sarcoma lung metastasis. This study proposed an antisarcoma strategy via stimulation of the immune system as a further alternative approach for sarcoma treatment and elucidated the mechanism of combined therapy.

Hsp70 in Liquid Biopsies-A Tumor-Specific Biomarker for Detection and Response Monitoring in Cancer

In contrast to normal cells, tumor cells of multiple entities overexpress the Heat shock protein 70 (Hsp70) not only in the cytosol, but also present it on their plasma membrane in a tumor-specific manner. Furthermore, membrane Hsp70-positive tumor cells actively release Hsp70 in small extracellular vesicles with biophysical characteristics of exosomes. Due to conformational changes of Hsp70 in a lipid environment, most commercially available antibodies fail to detect membrane-bound and vesicular Hsp70. To fill this gap and to assess the role of vesicular Hsp70 in circulation as a potential tumor biomarker, we established the novel complete (comp)Hsp70 sandwich ELISA, using two monoclonal antibodies (mAbs), that is able to recognize both free and lipid-associated Hsp70 on the cell surface of viable tumor cells and on small extracellular vesicles. The epitopes of the mAbs cmHsp70.1 (aa 451-461) and cmHsp70.2 (aa 614-623) that are conserved among different species reside in the substrate-binding domain of Hsp70 with measured affinities of 0.42 nM and 0.44 nM, respectively. Validation of the compHsp70 ELISA revealed a high intra- and inter-assay precision, linearity in a concentration range of 1.56 to 25 ng/mL, high recovery rates of spiked liposomal Hsp70 (>84%), comparable values between human serum and plasma samples and no interference by food intake or age of the donors. Hsp70 concentrations in the circulation of patients with glioblastoma, squamous cell or adeno non-small cell lung carcinoma (NSCLC) at diagnosis were significantly higher than those of healthy donors. Hsp70 concentrations dropped concomitantly with a decrease in viable tumor mass upon irradiation of patients with approximately 20 Gy (range 18-22.5 Gy) and after completion of radiotherapy (60-70 Gy). In summary, the compHsp70 ELISA presented herein provides a sensitive and reliable tool for measuring free and vesicular Hsp70 in liquid biopsies of tumor patients, levels of which can be used as a tumor-specific biomarker, for risk assessment (i.e., differentiation of grade III vs. IV adeno NSCLC) and monitoring of therapeutic outcomes.

Human heat shock cognate protein (HSC70/HSPA8) interacts with negatively charged phospholipids by a different mechanism than other HSP70s and brings HSP90 into membranes

Heat shock proteins (HSP) are critical elements for the preservation of cellular homeostasis by participating in an array of biological processes. In addition, HSP play an important role in cellular protection from various environmental stresses. HSP are part of a large family of different molecular mass polypeptides, displaying various expression patterns, subcellular localizations, and diversity functions. An unexpected observation was the detection of HSP on the cell surface. Subsequent studies have demonstrated that HSP have the ability to interact and penetrate lipid bilayers by a process initiated by the recognition of phospholipid heads, followed by conformational changes, membrane insertion, and oligomerization. In the present study, we described the interaction of HSPA8 (HSC70), the constitutive cytosolic member of the HSP70 family, with lipid membranes. HSPA8 showed high selectivity for negatively charged phospholipids, such as phosphatidylserine and cardiolipin, and low affinity for phosphatidylcholine. Membrane insertion was mediated by a spontaneous process driven by increases in entropy and diminished by the presence of ADP or ATP. Finally, HSPA8 was capable of driving into the lipid bilayer HSP90 that does not display any lipid biding capacity by itself. This observation suggests that HSPA8 may act as a membrane chaperone.

Heat Shock Proteins and Their Role in Pregnancy: Redefining the Function of "Old Rum in a New Bottle"

Pregnancy in humans is a multi-step complex physiological process comprising three discrete events, decidualization, implantation and placentation. Its overall success depends on the incremental advantage that each of the preceding stages passes on to the next. The success of these synchronized sequels of events is an outcome of timely coordination between them. The pregnancy events are coordinated and governed primarily by the ovarian steroid hormones, estrogen and progesterone, which are essentially ligand-activated transcription factors. It's well known that intercellular signaling of steroid hormones engages a plethora of adapter proteins that participate in executing the biological functions. This involves binding of the hormone receptor complex to the DNA response elements in a sequence specific manner. Working with Drosophila melanogaster, the heat shock proteins (HSPs) were originally described by Ferruccio Ritossa back in the early 1960s. Over the years, there has been considerable advancement of our understanding of these conserved families of proteins, particularly in pregnancy. Accumulating evidence suggests that endometrial and uterine cells have an abundance of HSP27, HSP60, HSP70 and HSP90, implying their possible involvement during the pregnancy process. HSPs have been found to be associated with decidualization, implantation and placentation, with their dysregulation associated with implantation failure, pregnancy loss and other feto-maternal complications. Furthermore, HSP is also associated with stress response, specifically in modulating the ER stress, a critical determinant for reproductive success. Recent advances suggest a therapeutic role of HSPs proteins in improving the pregnancy outcome. In this review, we summarized our latest understanding of the role of different members of the HSP families during pregnancy and associated complications based on experimental and clinical evidences, thereby redefining and exploring their novel function with new perspective, beyond their prototype role as molecular chaperones.

ANO7: Insights into topology, function, and potential applications as a biomarker and immunotherapy target

Anoctamin 7 (ANO7) is a member of the transmembrane protein TMEM16 family. It has a conservative topology similar to other members in this family, such as the typical eight-transmembrane domain, but it also has unique features. Although the ion channel role of ANO7 has been well accepted, evolutionary analyses and relevant studies suggest that ANO7 may be a multi-facet protein in function. Studies have shown that ANO7 may also function as a scramblase. ANO7 is highly expressed in prostate cancer as well as normal prostate tissues. A considerable amount of evidence has confirmed that ANO7 is associated with human physiology and pathology, particularly with the development of prostate cancer, which makes ANO7 a good candidate as a diagnostic and prognostic biomarker. In addition, ANO7 may be a potential target for prostate cancer immunotherapy. Antibody-based or T cell-mediated immunotherapies against prostate cancer by targeting ANO7 have been highly anticipated. ANO7 may also correlate with several other types of cancers or diseases, where further studies are warranted.

The interactome of the prostate-specific protein Anoctamin 7

BACKGROUND

Elevated Anoctamin 7 (ANO7) expression is associated with poor survival in prostate cancer patients.

OBJECTIVE

The aim was to discover proteins that interact with ANO7 to understand its functions and regulatory mechanisms.

METHODS

The proximity-dependent biotin identification (BioID) method was utilized. ANO7 fused to biotin ligase was transiently transfected into LNCaP cells, and the biotinylated proteins were collected and analysed by mass spectrometry. Four identified proteins were stained with dual fluorescent immunostaining and visualized using Stimulated emission depletion microscopy (STED).

RESULTS

After bioinformatic filtering steps, 64 potentially ANO7-interacting proteins were identified and analysed with the GO enrichment analysis tool. One of the most prominently enriched cellular components was cellular vesicle. Co-localization was showed for staphylococcal nuclease and tudor domain containing 1 (SND1), heat shock protein family A (Hsp70) member 1A (HSPA1A), adaptor related protein complex 2 subunit beta 1 (AP2B1) and coatomer protein complex subunit gamma 2 (COPG2).

CONCLUSIONS

This is the first study in which ANO7 interacting proteins have been identified. Although further studies are needed, the findings reported here expand our understanding of the role and regulation of ANO7 in prostate cancer cells. Furthermore, these results are likely to introduce new targets for the novel cancer therapies.

Intravenous Immunoglobulin G Suppresses Heat Shock Protein (HSP)-70 Expression and Enhances the Activity of HSP90 and Proteasome Inhibitors

Intravenous immunoglobulin G (IVIgG) is approved for primary immunodeficiency syndromes but may induce anti-cancer effects, and while this has been attributed to its anti-inflammatory properties, IgG against specific tumor targets may play a role. We evaluated IVIgG alone, and with a Heat shock protein (HSP)-90 or proteasome inhibitor, using multiple myeloma and mantle cell lymphoma (MCL) cells in vitro, and with the proteasome inhibitor bortezomib in vivo. IVIgG inhibited the growth of all cell lines tested, induced G₁ cell cycle arrest, and suppressed pro-tumor cytokines including Interleukin (IL)-6, IL-8, and IL-10. Genomic and proteomic studies showed that IVIgG reduced tumor cell HSP70-1 levels by suppressing the ability of extracellular HSP70-1 to stimulate endogenous HSP70-1 promoter activity, and reduced extracellular vesicle uptake. Preparations of IVIgG were found to contain high titers of anti-HSP70-1 IgG, and recombinant HSP70-1 reduced the efficacy of IVIgG to suppress HSP70-1 levels. Combining IVIgG with the HSP90 inhibitor AUY922 produced superior cell growth inhibition and correlated with HSP70-1 suppression. Also, IVIgG with bortezomib or carfilzomib was superior to each single agent, and enhanced bortezomib's activity in bortezomib-resistant myeloma cells. Moreover, IVIgG reduced transfer of extracellular vesicles (EVs) to cells, and blocked transfer of bortezomib resistance through EVs. Finally, IVIgG with bortezomib were superior to the single agents in an in vivo myeloma model. These studies support the possibility that anti-HSP70-1 IgG contained in IVIgG can inhibit myeloma and MCL growth by interfering with a novel mechanism involving uptake of exogenous HSP70-1 which then induces its own promoter.

Time- and Dose-Dependent Effects of Ionizing Irradiation on the Membrane Expression of Hsp70 on Glioma Cells

The major stress-inducible protein Hsp70 (HSPA1A) is overexpressed in the cytosol of many highly aggressive tumor cells including glioblastoma multiforme and presented on their plasma membrane. Depending on its intracellular or membrane localization, Hsp70 either promotes tumor growth or serves as a target for natural killer (NK) cells. The kinetics of the membrane Hsp70 (mHsp70) density on human glioma cells (U87) was studied after different irradiation doses to define the optimal therapeutic window for Hsp70-targeting NK cells. To maintain the cells in the exponential growth phase during a cultivation period of 7 days, different initial cell counts were seeded. Although cytosolic Hsp70 levels remained unchanged on days 4 and 7 after a sublethal irradiation with 2, 4 and 6 Gy, a dose of 2 Gy resulted in an upregulated mHsp70 density in U87 cells which peaked on day 4 and started to decline on day 7. Higher radiation doses (4 Gy, 6 Gy) resulted in an earlier and more rapid onset of the mHsp70 expression on days 2 and 1, respectively, followed by a decline on day 5. Membrane Hsp70 levels were higher on cells in G2/M than in G1; however, an irradiation-induced cell cycle arrest on days 4 and 7 was not associated with an increase in the mHsp70 density. Extracellular Hsp70 concentrations in the supernatant of irradiated cells were significantly higher than sham (0 Gy) irradiated cells on days 4 and 7, but not on day 1. Functionally, elevated mHsp70 densities were associated with a significantly better lysis by Hsp70-targeting NK cells. In summary, the kinetics of changes in the mHsp70 density upon irradiation on tumor cells is time- and dose-dependent.

Lectin-like and bacterial-agglutinating activities of heat shock proteins Hsp5 and Hsp90α from amphioxus Branchiostoma japonicum

Previous studies have shown that heat shock proteins (Hsps) are broadly associated in immune responses in a variety of animals. However, it remains largely unknown about the direct roles of Hsps during a bacterial infection. In this study, we have cloned and characterized the cDNAs of two Hsp genes in the amphioxus Branchiostoma japonicum, termed Bjhsp5 and Bjhsp90α, the first ones in this evolutionarily important animal. Both Bjhsp5 and Bjhsp90α showed distinct tissue expression patterns, and were inducible by challenge with lipopolysaccharide (LPS) and lipoteichoic acid (LTA), suggesting they may be involved in anti-infectious responses. We also showed that both BjHsp5 and BjHsp90α displayed lectin-like property with affinity to both the Gram-negative and -positive bacteria as well as their signature molecules LPS and LTA, hinting they may both act as a pattern recognition receptor, capable of identifying pathogens. In addition, we found that BjHsp5 and BjHsp90α were both able to agglutinate the Gram-negative and -positive bacteria in the presence of Ca²⁺, suggesting they may be able to trap the invading pathogens together in vivo, avoiding them moving around and thereby protecting the host from pathogenic attack. These data provide a new angle to the roles of Hsps in immune defense.

Heat shock proteins in the physiology and pathophysiology of epidermal keratinocytes

Heat shock proteins (HSPs), a large group of highly evolutionary conserved proteins, are considered to be main elements of the cellular proteoprotection system. HSPs are encoded by genes activated during the exposure of cells to proteotoxic factors, as well as by genes that are expressed constitutively under physiological conditions. HSPs, having properties of molecular chaperones, are involved in controlling/modulation of multiple cellular and physiological processes. In the presented review, we summarize the current knowledge on HSPs in the biology of epidermis, the outer skin layer composed of stratified squamous epithelium. This tissue has a vital barrier function preventing from dehydratation due to passive diffusion of water out of the skin, and protecting from infection and other environmental insults. We focused on HSPB1 (HSP27), HSPA1 (HSP70), HSPA2, and HSPC (HSP90), because only these HSPs have been studied in the context of physiology and pathophysiology of the epidermis. The analysis of literature data shows that HSPB1 plays a role in the regulation of final steps of keratinization; HSPA1 is involved in the cytoprotection, HSPA2 contributes to the early steps of keratinocyte differentiation, while HSPC is essential in the re-epithelialization process. Since HSPs have diverse functions in various types of somatic tissues, in spite of multiple investigations, open questions still remain about detailed roles of a particular HSP isoform in the biology of epidermal keratinocytes.

GRP78 regulates CD44v membrane homeostasis and cell spreading in tamoxifen-resistant breast cancer

GRP78 conducts protein folding and quality control in the ER and shows elevated expression and cell surface translocation in advanced tumors. However, the underlying mechanisms enabling GRP78 to exert novel signaling functions at cell surface are just emerging. CD44 is a transmembrane protein and an important regulator of cancer metastasis, and isoform switch of CD44 through incorporating additional variable exons to the extracellular juxtamembrane region is frequently observed during cancer progression. Using super-resolution dual-color single-particle tracking, we report that GRP78 interacts with CD44v in plasma membrane nanodomains of breast cancer cells. We further show that targeting cell surface GRP78 by the antibodies can effectively reduce cell surface expression of CD44v and cell spreading of tamoxifen-resistant breast cancer cells. Our results uncover new functions of GRP78 as an interacting partner of CD44v and as a regulator of CD44v membrane homeostasis and cell spreading. This study also provides new insights into anti-CD44 therapy in tamoxifen-resistant breast cancer.

Increasing Levels of Serum Heat Shock Protein 70 Precede the Development of AIDS-Defining Non-Hodgkin Lymphoma Among Carriers of HLA-B8-DR3

BACKGROUND

We hypothesized that carriage of presumably high Hsp70-producing gene variants on a specific human major histocompatibility complex haplotype, the 8.1 ancestral haplotype (8.1AH), may predispose HIV-infected individuals to AIDS-non-Hodgkin lymphoma (NHL).

SETTING

We compared serum Hsp70 levels in the years preceding the diagnosis of AIDS-NHL in a matched case-control study (n = 151 pairs) nested in the Multicenter AIDS Cohort Study.

METHODS

We tested the impact of 8.1AH-specific single-nucleotide polymorphism (SNP) and joint SNP-human leukocyte antigen extended haplotypes previously associated with AIDS-NHL in the Multicenter AIDS Cohort Study on the circulating Hsp70 levels in mixed linear models.

RESULTS

We report elevated serum levels of Hsp70 in the 4 years preceding the diagnosis of AIDS-NHL in cases that carry 8.1AH, but not in noncarrier cases and not in carrier- or non-carrier-matched controls. The strongest predictor of higher serum Hsp70 was the haplotype A-G-A-C formed by SNPs rs537160(A) and rs1270942(G) in the complement factor CFB gene cluster, and rs2072633(A) and rs6467(C) in nearby RDBP and CYP21A2 located 70 Kb apart from the Hsp70 gene cluster. The association with A-G-A-C haplotype (beta = 0.718; standard error = 0.182; P = 0.0002) and with other 8.1AH-specific haplotypes including the high-producing tumor necrosis factor-alpha haplotype rs909253(G)-rs1800629(A) (beta = 0.308; standard error = 0.140; P = 0.032) were observed only with NHL identified as an AIDS-defining condition, but not as a post-AIDS condition, nor in combined AIDS and post-AIDS cases.

CONCLUSION

Our combined genetic and functional approach suggests that the altered level of Hsp70 is a correlate of 8.1AH-mediated AIDS-NHL. Further investigation of the Hsp70 gene cluster and nearby loci that are tagged by A-G-A-C could better elucidate the genetic determinants of the malignancy.

Membrane Hsp70-supported cell-to-cell connections via tunneling nanotubes revealed by live-cell STED nanoscopy

Heat shock protein Hsp70 (Hsp70) is found on the cell surface of a large variety of human and mouse tumor cell types including U87, GL261 glioblastoma, and 4T1 mammary carcinoma cells. We studied the role of membrane-bound Hsp70 (mHsp70) in the formation of cell-to-cell connections via tunneling nanotubes (TNTs) using live-cell STED nanoscopy. This technique allows the visualization of microstructures in the 100-nm range in the living cells. We could show that the presence of tumor-derived mHsp70 in TNTs with a diameter ranging from 120 to 140 nm predominantly originates from cholesterol-rich-microdomains containing the lipid compound globoyltriaosylceramide (Gb3). Under non-stress conditions, Hsp70 and Gb3 are structurally clustered in the membrane of TNTs of tumor cells that showed tumor type specific variations in the amount of cell-to-cell connection networks. Furthermore depletion of cholesterol and ionizing radiation as a stress factor results in a complete loss of Hsp70-containing TNTs.

CD56bright cells respond to stimulation until very advanced age revealing increased expression of cellular protective proteins SIRT1, HSP70 and SOD2

BACKGROUND

NK cells are cytotoxic lymphocytes of innate immunity composed of: cytotoxic CD56dim and immunoregulatory CD56bright cells. The study aimed to analyze the expression of cellular protective proteins: sirtuin 1 (SIRT1), heat shock protein 70 (HSP70) and manganese superoxide dismutase (SOD2) in CD56dim and CD56bright NK cells of the young, seniors aged under 85 ('the old') and seniors aged over 85 ('the oldest'). We studied both non-stimulated NK cells and cells stimulated by IL-2, LPS or PMA with ionomycin. The expression level of proinflammatory cytokines TNF and IFN-γ was also assessed in NK cell subsets and some relationships between the studied parameters were analyzed.

RESULTS

CD56bright cells showed sensitivity to most of the applied stimulatory agents until very advanced age in regards to the expression of SIRT1 and intracellular HSP70. On the contrary, CD56dim cells, sensitive to stimulation by most of the stimulatory agents in the young and the old, in the oldest lost this sensitivity and presented rather high, constant expression of SIRT1 and HSP70, resistant to further stimulation. With reference to SOD2 expression, CD56dim cells were insensitive to stimulation in the young, but their sensitivity increased with ageing. CD56bright cells were sensitive to most of the applied agents in the young and the old but in the oldest they responded to all of the stimulatory agents used in the study. Similarly, both NK cell subsets were sensitive to stimulation until very advanced age in regards to the expression of TNF and IFN-γ.

CONCLUSIONS

CD56bright cells maintained sensitivity to stimulation until very advanced age presenting also an increased expression of SIRT1 and HSP70. CD56dim cells showed a constantly increased expression of these cellular protective proteins in the oldest, insensitive for further stimulation. The oldest, however, did not reveal an increased level of SOD2 expression, but it was significantly elevated in both NK cell subsets after stimulation.The pattern of expression of the studied cellular protective proteins in ageing process revealed the adaptation of NK cells to stress response in the oldest seniors which might accompany the immunosenescence and contribute to the long lifespan of this group of the elderly.

Heat Shock Proteins as Immunomodulants

Heat shock proteins (Hsps) are conserved molecules whose main role is to facilitate folding of other proteins. Most Hsps are generally stress-inducible as they play a particularly important cytoprotective role in cells exposed to stressful conditions. Initially, Hsps were generally thought to occur intracellulary. However, recent work has shown that some Hsps are secreted to the cell exterior particularly in response to stress. For this reason, they are generally regarded as danger signaling biomarkers. In this way, they prompt the immune system to react to prevailing adverse cellular conditions. For example, their enhanced secretion by cancer cells facilitate targeting of these cells by natural killer cells. Notably, Hsps are implicated in both pro-inflammatory and anti-inflammatory responses. Their effects on immune cells depends on a number of aspects such as concentration of the respective Hsp species. In addition, various Hsp species exert unique effects on immune cells. Because of their conservation, Hsps are implicated in auto-immune diseases. Here we discuss the various metabolic pathways in which various Hsps manifest immune modulation. In addition, we discuss possible experimental variations that may account for contradictory reports on the immunomodulatory function of some Hsps.

Circulating Heat Shock Protein 70 Is a Novel Biomarker for Early Diagnosis of Lung Cancer

Heat shock protein 70 (HSP70) was a highly conserved protein which was significantly induced in response to cellular stresses. HSP70 played an important role in the pathogenesis of cancer which stabilized the production of large amount of oncogenic proteins and finally supported growth and survival of tumor. However, there was no report about the diagnosis of circulating HSP70 in lung cancer patients. In this study, a total of 297 participants (lung cancer: 197, healthy control: 100) were enrolled in the detection of circulating HSP70 level in plasma by ELISA assay. The results indicated that circulating HSP70 significantly decreased in lung cancer patients compared to healthy controls (P < 0.0001). Receiver operating characteristic (ROC) analysis showed that HSP70 (AUC: 82.2%, SN: 74.1%, SP: 80.0%) had higher diagnosis value than clinical existing biomarkers CEA (AUC: 80.1%, SN: 76.8%, SP: 67.3%) and CA 19-9 (AUC: 63.7%, SN: 64.2%, SP: 54.0%). In the analysis of early lung cancer patients, ROC results also revealed that HSP70 (AUC: 83.8%, SN: 71.2%, SP: 84.0%) have higher sensitivity, specificity, and AUC than CEA (AUC: 73.7%, SN: 73.2%, SP: 69.1%) and CA 19-9 (AUC: 61.5%, SN: 69.4%, SP: 53.4%). In analysis of specific histological classifications, HSP70 showed more valuable in the diagnosis of SCC (AUC: 85.9%, SN: 86.1.9%, SP: 81.0%) than ADC (AUC: 81.0%, SN: 69.1%, SP: 81.0%). Combined analysis of HSP70 and existing biomarker: CEA and CA 19-9 exhibited that HSP70 combined CEA and CA 19-9 showed the highest AUC (0.945, 95% CI, 0.855–1.000). The importance of our results was that we found decreased circulating HSP70, in combination with elevated CEA and CA 19-9, could be utilized in the diagnosis of early (stage I and II) lung cancer.

Immunohistochemical and Flow Cytometric Analysis of Intracellular and Membrane-Bound Hsp70, as a Putative Biomarker of Glioblastoma Multiforme, Using the cmHsp70.1 Monoclonal Antibody

The major stress-inducible 70 kDa heat shock (stress) protein 70 (Hsp70) is frequently overexpressed in highly aggressive tumor cells and thus might serve as a tumor-specific biomarker of aggressive disease. We have previously shown that, in contrast to normal cells, tumor cells present Hsp70 on their plasma membrane. In order to elucidate the role of intracellular and membrane-bound Hsp70 as a potential tumor biomarker in glioblastoma multiforme, herein, we describe protocols for the staining of cytosolic Hsp70 in tumor formalin fixed paraffin-embedded (FFPE) sections using immunohistochemistry, and for plasma membrane-bound Hsp70 by multi-parametric flow cytometry using the cmHsp70.1 monoclonal antibody (mAb).

Molecular AFM imaging of Hsp70-1A association with dipalmitoyl phosphatidylserine reveals membrane blebbing in the presence of cholesterol

Hsp70-1A-the major stress-inducible member of the HSP70 chaperone family-is being implicated in cancer diseases with the development of resistances to standard therapies. In normal cells, the protein is purely cytosolic, but in a growing number of tumor cells, a significant fraction can be identified on to the cell surface. The anchoring mechanism is still under debate, as Hsp70-1A lacks conventional signaling sequences for translocation from the cytosol to exoplasmic leaflet of the plasma membrane and common membrane binding domains. Recent reports propose a lipid-mediated anchoring mechanism based on a specific interaction with charged, saturated lipids such as dipalmitoyl phosphatidylserine (DPPS). Here, we prepared planar supported lipid bilayers (SLBs) to visualize the association of Hsp70-1A directly and on the single molecule level by atomic force microscopy (AFM). The single molecule sensitivity of our approach allowed us to explore the low concentration range of 0.05 to 1.0 μg/ml of Hsp70-1A which was not studied before. We compared the binding of the protein to bilayers with 20% DPPS lipid content both in the absence and presence of cholesterol. Hsp70-1A inserted exclusively into DPPS domains and assembled in clusters with increasing protein density. A critical density was reached for incubation with 0.5 μg/ml (7 nM); at higher concentrations, membrane defects were observed that originated from cluster centers. In the presence of cholesterol, this critical concentration leads to the formation of membrane blebs, which burst at higher concentrations supporting a previously proposed non-classical pathway for the export of Hsp70-1A by tumor cells. In the discussion of our data, we attempt to link the lipid-mediated plasma membrane localization of Hsp70-1A to its potential involvement in the development of resistances to radiation and chemotherapy based on our own findings and the current literature.

Extracellular cell stress (heat shock) proteins-immune responses and disease: an overview

Extracellular cell stress proteins are highly conserved phylogenetically and have been shown to act as powerful signalling agonists and receptors for selected ligands in several different settings. They also act as immunostimulatory 'danger signals' for the innate and adaptive immune systems. Other studies have shown that cell stress proteins and the induction of immune reactivity to self-cell stress proteins can attenuate disease processes. Some proteins (e.g. Hsp60, Hsp70, gp96) exhibit both inflammatory and anti-inflammatory properties, depending on the context in which they encounter responding immune cells. The burgeoning literature reporting the presence of stress proteins in a range of biological fluids in healthy individuals/non-diseased settings, the association of extracellular stress protein levels with a plethora of clinical and pathological conditions and the selective expression of a membrane form of Hsp70 on cancer cells now supports the concept that extracellular cell stress proteins are involved in maintaining/regulating organismal homeostasis and in disease processes and phenotype. Cell stress proteins, therefore, form a biologically complex extracellular cell stress protein network having diverse biological, homeostatic and immunomodulatory properties, the understanding of which offers exciting opportunities for delivering novel approaches to predict, identify, diagnose, manage and treat disease.This article is part of the theme issue 'Heat shock proteins as modulators and therapeutic targets of chronic disease: an integrated perspective'.

NK cells of the oldest seniors represent constant and resistant to stimulation high expression of cellular protective proteins SIRT1 and HSP70

Background

Natural killer cells (NK cells) are cytotoxic lymphocytes of innate immunity that reveal some immunoregulatory properties, however, their role in the process of ageing is not completely understood. The study aimed to analyze the expression of proteins involved in cellular stress response: sirtuin 1 (SIRT1), heat shock protein 70 (HSP70) and manganese superoxide dismutase (SOD2) in human NK cells with reference to the process of ageing. Non-stimulated and stimulated with IL-2, LPS or PMA with ionomycin cells originated from peripheral blood samples of: seniors aged over 85 (‘the oldest’; n = 25; 88.5 ± 0.5 years, mean ± SEM), seniors aged under 85 (‘the old’; n = 30; 75.6 ± 0.9 years) and the young (n = 31; 20.9 ± 0.3 years). The relationships between the levels of expression of cellular protective proteins in the studied population were also analyzed. The concentrations of carbonyl groups and 8-isoprostanes, markers of oxidative stress, in both stimulated and non-stimulated cultured NK cells were measured to assess the level of the oxidative stress in the cells.

Results

The oldest seniors varied from the other age groups by significantly higher expression of SIRT1 and HSP70 both in non-stimulated and stimulated NK cells. These cells also appeared to be resistant to further stimulations with IL-2, LPS or PMA with ionomycin. Highly positive correlations between SIRT1 and intracellular HSP70 in both stimulated and non-stimulated NK cells were observed. SOD2 presented low expression in non-stimulated cells, whereas its sensitivity to stimulation increased with age of donors. High positive correlations between SOD2 and surface HSP70 were observed. We found that the markers of oxidative stress in NK cells did not change with ageing.

Conclusions

The oldest seniors revealed well developed adaptive stress response in NK cells with increased, constant levels of SIRT1 and intracellular HSP70. They presented also very high positive correlations between expression of these cellular protective proteins both in stimulated and non-stimulated cells. These phenomena may contribute to the long lifespan of this group of elderly. Interestingly, in NK cells SOD2 revealed a distinct role in cellular stress response since it showed sensitivity to stimulation increasing with age of participants. These observations provide novel data concerning the role of NK cells in the process of ageing.

Selection of an Anticalin® against the membrane form of Hsp70 via bacterial surface display and its theranostic application in tumour models

We describe the selection of Anticalins against a common tumour surface antigen, human Hsp70, using functional display on live Escherichia coli cells as fusion with a truncated EspP autotransporter. While found intracellularly in normal cells, Hsp70 is frequently exposed in a membrane-bound state on the surface of tumour cells and, even more pronounced, in metastases or after radiochemotherapy. Employing a recombinant Hsp70 fragment comprising residues 383-548 as the target, Anticalins were selected from a naïve bacterial library. The Anticalin with the highest affinity (K D=13 nm), as determined towards recombinant full-length Hsp70 by real-time surface plasmon resonance analysis, was improved to K D=510 pm by doped random mutagenesis and another cycle of E. coli surface display, followed by rational combination of mutations. This Anticalin, which recognises a linear peptide epitope located in the interdomain linker of Hsp70, was demonstrated to specifically bind Hsp70 in its membrane-associated form in immunofluorescence microscopy and via flow cytometry using the FaDu cell line, which is positive for surface Hsp70. The radiolabelled and PASylated Anticalin revealed specific tumour accumulation in xenograft mice using positron emission tomography (PET) imaging. Furthermore, after enzymatic coupling to the protein toxin gelonin, the Anticalin showed potent cytotoxicity on FaDu cells in vitro.

Heart irradiation reduces microvascular density and accumulation of HSPA1 in mice

PURPOSE

Improvement of radiotherapy techniques reduces the exposure of normal tissues to ionizing radiation. However, the risk of radiation-related late effects remains elevated. In the present study, we investigated long-term effects of radiation on heart muscle morphology.

MATERIALS AND METHODS

We established a mouse model to study microvascular density (MVD), deposition of collagen fibers, and changes in accumulation of heat shock 70 kDa protein 1 (HSPA1) in irradiated heart tissue. Hearts of C57BL/6 mice received a single dose of X‑ray radiation in the range 0.2-16 Gy. Analyses were performed 20, 40, and 60 weeks after irradiation.

RESULTS

Reduction in MD was revealed as a long-term effect observed 20-60 weeks after irradiation. Moreover, a significant and dose-dependent increase in accumulation of HSPA1, both cytoplasmic and nuclear, was observed in heart tissues collected 20 weeks after irradiation. We also noticed an increase in collagen deposition in hearts treated with higher doses.

CONCLUSIONS

This study shows that some changes induced by radiation in the heart tissue, such as reduction in microvessel density, increase in collagen deposition, and accumulation of HSPA1, are observed as long-term effects which might be associated with late radiation cardiotoxicity.

Interplay between recombinant Hsp70 and proteasomes: proteasome activity modulation and ubiquitin-independent cleavage of Hsp70

The heat shock protein 70 (Hsp70, human HSPA1A) plays indispensable roles in cellular stress responses and protein quality control (PQC). In the framework of PQC, it cooperates with the ubiquitin-proteasome system (UPS) to clear damaged and dysfunctional proteins in the cell. Moreover, Hsp70 itself is rapidly degraded following the recovery from stress. It was demonstrated that its fast turnover is mediated via ubiquitination and subsequent degradation by the 26S proteasome. At the same time, the effect of Hsp70 on the functional state of proteasomes has been insufficiently investigated. Here, we characterized the direct effect of recombinant Hsp70 on the activity of 20S and 26S proteasomes and studied Hsp70 degradation by the 20S proteasome in vitro. We have shown that the activity of purified 20S proteasomes is decreased following incubation with recombinant human Hsp70. On the other hand, high concentrations of Hsp70 activated 26S proteasomes. Finally, we obtained evidence that in addition to previously reported ubiquitin-dependent degradation, Hsp70 could be cleaved independent of ubiquitination by the 20S proteasome. The results obtained reveal novel aspects of the interplay between Hsp70 and proteasomes.

Anti-heat Shock 70 kDa Protein Antibody Induced Neuronal Cell Death

Heat shock protein 70 (Hsp70) is not only a molecular chaperone in cytosol, but also presents in synaptic plasma membranes. To detect plasmalemmal Hsp70 (pl-Hsp70), neurons were immunostained with anti-Hsp70 antibody without permeabilization and fixation. Dotted immunofluorescent signals at neuronal cell bodies and neurites indicated the localization of Hsp70 on the neuronal cell surface. To target only pl-Hsp70, but not cytosolic Hsp70, the anti-Hsp70 antibody was applied without permeabilization in the primary culture of rat cortical neurons. The antibody induced neuronal cell death in a concentration-dependent manner. The anti-Hsp70 antibody activated ubiquitin-proteasome pathway, but inactivated caspase-3. A lag time was required for the neurotoxicity of anti-Hsp70 antibody. Hydrogen peroxide was increased in the anti-Hsp70 antibody-treated neurons during the lag time. Catalase suppressed the anti-Hsp70 antibody-reduced cell viability via the plausible inhibition of hydrogen peroxide generation. One of down-streams of hydrogen peroxide exposure is activation of the mitogen-activated protein kinase (MAPK) signaling cascade. The neurotoxicity of anti-Hsp70 antibody was partially ascribed to c-Jun N-terminal kinase among MAPKs. In conclusion, the anti-Hsp70 antibody targeted pl-Hsp70 on the neuronal cell surface and induced neuronal cell death without complement. Furthermore, hydrogen peroxide appeared to mediate the neuronal cell death, which was accompanied with the enhancement of the ubiquitin-proteasome pathway and the suppression of caspase in a different fashion from the known cell death.

The Macrophage Activation Induced by Bacillus thuringiensis Cry1Ac Protoxin Involves ERK1/2 and p38 Pathways and the Interaction with Cell-Surface-HSP70

Here, we aimed to further characterize the mechanisms involved in protoxin (p) Cry1Ac-induced macrophage activation. We demonstrated that pCry1Ac induces MAPK ERK1/2, p38, and JNK phosphorylation in RAW264.7 macrophages. Because MAPK activation is mainly triggered via ligand-receptor interactions, we focused on the identification of potential pCry1Ac-receptor proteins. Flow cytometry and confocal analysis showed specific saturable pCry1Ac-binding to the macrophage surface and evidenced its internalization via the clathrin-pathway. We performed immunoprecipitation assays and identified by MALDI-TOF-TOF several possible pCry1Ac-binding proteins, such as heat shock proteins (HSPs), vimentin, α-enolase, and actin; whose interaction and presence was confirmed, respectively, by ligand blot and Western blot assays. We also detected cell-surface (cs) pCry1Ac-HSP70 colocalization, so HSP70 was chosen for further characterization. Co-immunoprecipitation with HSP70 antibodies followed by Western blot confirmed the pCry1Ac-HSP70 interaction. Furthermore, pretreatment of RAW264.7 cells with HSP70 antibodies reduced pCry1Ac-induced ERK1 phosphorylation and MCP-1 production; thus suggest the functional participation of csHSP70 in pCry1Ac-induced macrophage activation. csHSP70 also was evaluated in peritoneal-cavity (PerC) macrophages of untreated BALB/c mice, interestingly it was found that the predominant population namely large-peritoneal-macrophages (LPM) displayed csHSP70 + hi. Furthermore, the dynamics of PerC macrophage subsets, LPM, and small-peritoneal macrophages (SPM) were evaluated in response to in vivo pCry1Ac stimuli in presence or not of phenylethynesulfonamide (PES) a functional HSP70 inhibitor. It was found that pCry1Ac increased the proportion of SPM CD11b + F4/80 + lowMHCII + csHSP70 + low and markedly reduced the amount of LPM CD11b + F4/80 + hiMHCII-csHSP70 + hi; while PES, partially suppressed this pCry1Ac-induced effect, further suggesting the participation of HSP70 in macrophage activation process. J. Cell. Biochem. 119: 580-598, 2018. © 2017 Wiley Periodicals, Inc.

Pro-invasive stimuli and the interacting protein Hsp70 favour the route of alpha-enolase to the cell surface

Cell surface expression of alpha-enolase, a glycolytic enzyme displaying moonlighting activities, has been shown to contribute to the motility and invasiveness of cancer cells through the protein non-enzymatic function of binding plasminogen and enhancing plasmin formation. Although a few recent records indicate the involvement of protein partners in the localization of alpha-enolase to the plasma membrane, the cellular mechanisms underlying surface exposure remain largely elusive. Searching for novel interactors and signalling pathways, we used low-metastatic breast cancer cells, a doxorubicin-resistant counterpart and a non-tumourigenic mammary epithelial cell line. Here, we demonstrate by a combination of experimental approaches that epidermal growth factor (EGF) exposure, like lipopolysaccharide (LPS) exposure, promotes the surface expression of alpha-enolase. We also establish Heat shock protein 70 (Hsp70), a multifunctional chaperone distributed in intracellular, plasma membrane and extracellular compartments, as a novel alpha-enolase interactor and demonstrate a functional involvement of Hsp70 in the surface localization of alpha-enolase. Our results contribute to shedding light on the control of surface expression of alpha-enolase in non-tumourigenic and cancer cells and suggest novel targets to counteract the metastatic potential of tumours.

Expression of cellular protective proteins SIRT1, HSP70 and SOD2 correlates with age and is significantly higher in NK cells of the oldest seniors

Background

NK cells are key effector lymphocytes of innate immunity provided with constitutive cytolytic activity, however, their role in human ageing is not entirely understood. The study aimed to analyze the expression of proteins involved in cellular stress response sirtuin 1 (SIRT1), heat shock protein 70 (HSP70) and manganese superoxide dismutase (SOD2) in non-stimulated NK cells of the oldest seniors (n = 25; aged over 85; mean age 88 years) and compare with NK cells of the old (n = 30; aged under 85; mean age 76 years) and the young (n = 32; mean age 21 years) to find potential relationships between the level of expression of these proteins in NK cells and longevity. The concentration of carbonyl groups and 8-isoprostanes in NK cell lysates reflecting the level of oxidative stress was also measured.

Results

The group of the oldest seniors differed from the other age groups by significantly higher percentage of NK cells expressing SIRT1, HSP70 and SOD2. The concentration of both carbonyl groups and 8-isoprostanes in NK cell extracts remained within the normal range in all age groups. The percentage of NK cells with the expression of, respectively, SIRT1, HSP70 and SOD2 correlated positively with age. Some correlations between expression levels of particular protective proteins SIRT1, HSP70 and SOD2 were observed in the study population.

Conclusions

The increased expression of cellular protective proteins SIRT1, HSP70 and SOD2 in NK cells of the oldest seniors seems to correspond to longevity and the observed correlations may suggest the involvement of these proteins in establishing NK cell homeostasis specific for healthy ageing process.

Encapsulated Hsp70 decreases endotoxin-induced production of ROS and TNFα in human phagocytes

Human heat shock protein Hsp70 was experimentally inserted into polyelectrolyte microcapsules. Encapsulated recombinant Hsp70 was studied in terms of its effects on neutrophil apoptosis, the production of reactive oxygen species, and the secretion of tumor necrosis factor alpha by promonocytic THP-1 cells. It was found that encapsulated Hsp70 effectively inhibits neutrophil apoptosis, unlike free exogenous protein used in solution. In THP-1 cells, encapsulated and free Hsp70 reduced LPS-induced tumor necrosis factor alpha production with a similar efficiency. Encapsulated Hsp70 reduces LPS-induced reactive oxygen species production by neutrophils in the course of its release from the microcapsules but not as much as free Hsp70. Thus, the polyelectrolyte microcapsules can be used as containers for the effective delivery of Hsp70 to neutrophils and monocytes to significantly improve the functioning of the innate immune system.

The development of modified human Hsp70 (HSPA1A) and its production in the milk of transgenic mice

The production of major human heat shock protein Hsp70 (HSPA1A) in a eukaryotic expression system is needed for testing and possible medical applications. In this study, transgenic mice were produced containing wild-type human Hsp70 allele in the vector providing expression in the milk. The results indicated that human Hsp70 was readily expressed in the transgenic animals but did not apparently preserve its intact structure and, hence, it was not possible to purify the protein using conventional isolation techniques. It was suggested that the protein underwent glycosylation in the process of expression, and this quite common modification for proteins expressed in the milk complicated its isolation. To check this possibility, we mutated all presumptive sites of glycosylation and tested the properties of the resulting modified Hsp70 expressed in E. coli. The investigation demonstrated that the modified protein exhibited all beneficial properties of the wild-type Hsp70 and was even superior to the latter for a few parameters. Based on these results, a transgenic mouse strain was obtained which expressed the modified Hsp70 in milk and which was easy to isolate using ATP columns. Therefore, the developed construct can be explored in various bioreactors for reliable manufacture of high quality, uniform, and reproducible human Hsp70 for possible medical applications including neurodegenerative diseases and cancer.

Nanoscale Extracellular Vesicle Analysis in Alzheimer's Disease Diagnosis and Therapy

Diagnostic assays that leverage bloodborne neuron-derived (neuronal) nanoscale extracellular vesicles (nsEVs) as “windows into the brain” can predict incidence of Alzheimer's Disease (AD) many years prior to onset. Beyond diagnostics, bloodborne neuronal nsEVs analysis may have substantial translational impact by revealing mechanisms of AD pathology; such knowledge could enlighten new drug targets and lead to new therapeutic approaches. The potential to establish three-dimensional nsEV analysis methods that characterize highly purified bloodborne nsEV populations in method of enrichment, cell type origin, and protein or RNA abundance dimensions could bring this promise to bear by yielding nsEV “omics” datasets that uncover new AD biomarkers and enable AD therapeutic development. In this review we provide a survey of both the current status of and new developments on the horizon in the field of neuronal nsEV analysis. This survey is supplemented by a discussion of the potential to translate such neuronal nsEV analyses to AD clinical diagnostic applications and drug development.

Correlation of Hsp70 Serum Levels with Gross Tumor Volume and Composition of Lymphocyte Subpopulations in Patients with Squamous Cell and Adeno Non-Small Cell Lung Cancer

Heat-shock protein 70 (Hsp70) is frequently found on the plasma membrane of a large number of malignant tumors including non-small cell lung cancer (NSCLC) and gets released into the blood circulation in lipid vesicles. On the one hand, a membrane (m)Hsp70-positive phenotype correlates with a high aggressiveness of the tumor; on the other hand, mHsp70 serves as a target for natural killer (NK) cells that had been pre-stimulated with Hsp70-peptide TKD plus low-dose interleukin-2 (TKD/IL-2). Following activation, NK cells show an up-regulated expression of activatory C-type lectin receptors, such as CD94/NKG2C, NKG2D, and natural cytotoxicity receptors (NCRs; NKp44, NKp46, and NKp30) and thereby gain the capacity to kill mHsp70-positive tumor cells. With respect to these results, the efficacy of ex vivo TKD/IL-2 stimulated, autologous NK cells is currently tested in a proof-of-concept phase II clinical trial in patients with squamous cell NSCLC after radiochemotherapy (RCT) at the TUM. Inclusion criteria are histological proven, non-resectable NSCLC in stage IIIA/IIIB, clinical responses to RCT and a mHsp70-positive tumor phenotype. The mHsp70 status is determined in the serum of patients using the lipHsp70 ELISA test, which enables the quantification of liposomal and free Hsp70. Squamous cell and adeno NSCLC patients had significantly higher serum Hsp70 levels than healthy controls. A significant correlation of serum Hsp70 levels with the gross tumor volume was shown for adeno and squamous cell NSCLC. However, significantly elevated ratios of activated CD69(+)/CD94(+) NK cells that are associated with low serum Hsp70 levels were observed only in patients with squamous cell lung cancer. These data might provide a first hint that squamous cell NSCLC is more immunogenic than adeno NSCLC.

Extracellular cell stress proteins as biomarkers of human disease

Although heat-shock (cell stress) proteins are commonly considered as being intracellular molecular chaperones that undertake a number of cytoprotective and cellular housekeeping functions, there is now a wealth of evidence to indicate that these proteins can be released by cells via active processes. Many molecular chaperones are secreted, or exist as cell surface proteins which can act as powerful signalling agonists and also as receptors for selected ligands. Levels of heat-shock (cell stress) proteins in biological fluids are now being associated with a plethora of clinical conditions, and these proteins therefore have potential utility as biomarkers of disease and/or response to therapeutic intervention. The present article summarizes current knowledge relating to extracellular cell stress proteins as biomarkers of human disease.

Construction of an aptamer modified liposomal system targeted to tumor endothelial cells

We describe herein the development of a high affinity and specific DNA aptamer as a new ligand for use in liposomal nanoparticles to target cultured mouse tumor endothelial cells (mTECs). Active targeted nanotechnology based drug delivery systems are currently of great interest, due to their potential for reducing side effects and facilitating the delivery of cytotoxic drugs or genes in a site specific manner. In this study, we report on a promising aptamer candidate AraHH036 that shows selective binding towards mTECs. The aptamer does not bind to normal cells, normal endothelial cells or tumor cells. Therefore, we synthesized an aptamer-polyethylene glycol (PEG) lipid conjugate and prepared aptamer based liposomes (ALPs) by the standard lipid hydration method. First, we quantified the higher capacity of ALPs to internalize into mTECs by incubating ALPs containing 1 mol%, 5 mol% and 10 mol% aptamer of total lipids and compared the results to those for unmodified PEGylated liposomes (PLPs). A confocal laser scanning microscope (CLSM) uptake study indicated that the ALPs were taken up more efficiently than PLPs. The measured Kd value of the ALPs was 142 nM. An intracellular trafficking study confirmed that most of the rhodamine labeled ALPs were taken up and co-localized with the green lysotracker, thus confirming that they were located in lysosomes. Finally, using an aptamer based proteomics approach, the molecular target protein of the aptamer was identified as heat shock protein 70 (HSP70). The results suggest that these ALPs offer promise as a new carrier molecule for delivering anti-angiogenesis drugs to tumor vasculature.

Analysis of serum heat shock protein 70 (HSPA1A) concentrations for diagnosis and disease activity monitoring in patients with rheumatoid arthritis

Heat shock proteins (HSPs) have been repeatedly implicated in the pathogenesis of rheumatoid arthritis (RA). The authors aimed to study applicability of heat shock protein 70 (HSPA1A) serum levels as a diagnostic factor and a severity indicator in patients with RA and to quantify cut-off point that predicts status of RA with highest specificity. A total of 76 patients with RA and 36 healthy adults were studied in this case-control analysis. Patients had a higher HSPA1A level than the control group (0.78 ± 0.13 vs. 0.12 ± 0.02 ng/mL, p = 0.006), irrespective of presence of absence of rheumatoid factor or anti-citrullinated cyclic peptide. Next, diagnostic accuracy of the HSPA1A in diagnosis of RA was evaluated (area under curve 0.71; p < 0.05). HSPA1A predicted status of having RA in levels above 0.42 ng/mL with more than 90 % specificity. In addition to diagnostic value, HSPA1A can distinguish between high disease activity (1.66 ± 0.75 ng/mL) and low (0.49 ± 0.1 ng/mL), moderate (0.52 ± 0.12 ng/mL), or remission phase (0.48 ± 0.11 ng/mL). Moreover, patients in remission still had a higher HSPA1A level compared to normal subject (0.48 ± 0.11 vs. 0.12 ± 0.02 ng/mL, p < 0.05). Our results showed that serum HSPA1A could be implemented as a specific tool to facilitate diagnosis and monitoring disease activity in patients with rheumatoid arthritis.

Upregulation of heat shock proteins and the promotion of damage-associated molecular pattern signals in a colorectal cancer model by modulated electrohyperthermia

In modulated electrohyperthermia (mEHT) the enrichment of electric field and the concomitant heat can selectively induce cell death in malignant tumors as a result of elevated glycolysis, lactate production (Warburg effect), and reduced electric impedance in cancer compared to normal tissues. Earlier, we showed in HT29 colorectal cancer xenografts that the mEHT-provoked programmed cell death was dominantly caspase independent and driven by apoptosis inducing factor activation. Using this model here, we studied the mEHT-related cell stress 0-, 1-, 4-, 8-, 14-, 24-, 48-, 72-, 120-, 168- and 216-h post-treatment by focusing on damage-associated molecular pattern (DAMP) signals. Significant cell death response upon mEHT treatment was accompanied by the early upregulation (4-h post-treatment) of heat shock protein (Hsp70 and Hsp90) mRNA levels. In situ, the treatment resulted in spatiotemporal occurrence of a DAMP protein signal sequence featured by the significant cytoplasmic to cell membrane translocation of calreticulin at 4 h, Hsp70 between 14 and 24 h and Hsp90 between 24- and 216-h post-treatment. The release of high-mobility group box1 protein (HMGB1) from tumor cell nuclei from 24-h post-treatment and its clearance from tumor cells by 48 h was also detected. Our results suggest that mEHT treatment can induce a DAMP-related signal sequence in colorectal cancer xenografts that may be relevant for promoting immunological cell death response, which need to be further tested in immune-competent animals.

Rapid isolation of extracellular vesicles from cell culture and biological fluids using a synthetic peptide with specific affinity for heat shock proteins

Recent studies indicate that extracellular vesicles are an important source material for many clinical applications, including minimally-invasive disease diagnosis. However, challenges for rapid and simple extracellular vesicle collection have hindered their application. We have developed and validated a novel class of peptides (which we named venceremin, or Vn) that exhibit nucleotide-independent specific affinity for canonical heat shock proteins. The Vn peptides were validated to specifically and efficiently capture HSP-containing extracellular vesicles from cell culture growth media, plasma, and urine by electron microscopy, atomic force microscopy, sequencing of nucleic acid cargo, proteomic profiling, immunoblotting, and nanoparticle tracking analysis. All of these analyses confirmed the material captured by the Vn peptides was comparable to those purified by the standard ultracentrifugation method. We show that the Vn peptides are a useful tool for the rapid isolation of extracellular vesicles using standard laboratory equipment. Moreover, the Vn peptides are adaptable to diverse platforms and therefore represent an excellent solution to the challenge of extracellular vesicle isolation for research and clinical applications.

Heat shock protein 70 serum levels differ significantly in patients with chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma

Members of the heat shock protein 70 (HSP70) family play an important role in assisting protein folding, preventing protein aggregation and transport of proteins across membranes under physiological conditions. Following environmental (i.e., irradiation, chemotherapy), physiological (i.e., cell growth, differentiation), and pathophysiological (i.e., inflammation, tumorigenesis) stress, the synthesis of heat shock proteins (HSPs) is highly up-regulated, whereas protein synthesis in general is reduced. In contrast to normal cells, many tumor entities including hepatocellular carcinoma (HCC) overexpress HSP70, the major-stress-inducible member of the HSP70 family, present it on their cell surface and secrete it into the extracellular milieu. Herein, the prognostic relevance of serum HSP70 levels in patients with chronic hepatitis (CH; n = 50), liver cirrhosis (LC; n = 46), and HCC (n = 47) was analyzed. Similar to other tumor entities, HSP70 is also present on the surface of primary HCC cells. The staining intensity of intracellular HSP70 in HCC tissue is stronger compared to control and cirrhotic liver sections. HSP70 serum levels in all HCC patients were significantly higher compared to a control group without liver disease (n = 40). No significant age- and gender-related differences in HSP70 serum levels were observed in male and female healthy human volunteers (n = 86). Patients with CH (n = 50) revealed significantly higher HSP70 serum levels compared to the control group, however, these values were significantly lower than those of HCC patients (n = 47). Furthermore, a subgroup of patients with LC who subsequently developed HCC (LC-HCC, n = 13) revealed higher HSP70 serum levels than patients with LC (n = 46, p = 0.05). These data indicate that serum HSP70 levels are consecutively increased in patients with CH, LC and liver carcinomas and thus might have a prognostic value.

Alcohol stress, membranes, and chaperones

Ethanol, which affects all body organs, exerts a number of cytotoxic effects, most of them independent of cell type. Ethanol treatment leads to increased membrane fluidity and to changes in membrane protein composition. It can also interact directly with membrane proteins, causing conformational changes and thereby influencing their function. The cytotoxic action may include an increased level of oxidative stress. Heat shock protein molecular chaperones are ubiquitously expressed evolutionarily conserved proteins which serve as critical regulators of cellular homeostasis. Heat shock proteins can be induced by various forms of stresses such as elevated temperature, alcohol treatment, or ischemia, and they are also upregulated in certain pathological conditions. As heat shock and ethanol stress provoke similar responses, it is likely that heat shock protein activation also has a role in the protection of membranes and other cellular components during alcohol stress.

Heat-shock proteins-based immunotherapy for advanced melanoma in the era of target therapies and immunomodulating agents

INTRODUCTION

Heat-shock proteins (HSPs) are highly conserved, stress-induced proteins that function as chaperones, stabilizing proteins and delivering peptides. Tumor-derived HSP peptide complexes (HSPPCs) induced immunity against several malignancies in preclinical models, exhibiting activity across tumor types.

AREAS COVERED

HSPPC-based vaccination showed clinical activity in subsets of patients with different malignancies (e.g., gastric, colorectal, pancreatic, ovarian cancer, and glioblastoma). In Phase III clinical trials for advanced melanoma and renal cell carcinoma patients, HSPPC-based vaccine demonstrated an excellent safety profile, thus emerging as a flexible tumor- and patient-specific therapeutic approach.

EXPERT OPINION

Melanoma, renal clear cell carcinoma, and glioblastoma are among suitable targets for HSP-based treatment as demonstrated by immune responses and clinical activity observed in subsets of patients, mainly those with early stage of disease and limited tumor burden. In order to further improve clinical activity, combinations of HSPPC-based vaccines with mutation-driven therapies, antiangiogenic agents, or immunomodulating monoclonal antibodies should be tested in controlled clinical trials.

Validation of heat shock protein 70 as a tumor-specific biomarker for monitoring the outcome of radiation therapy in tumor mouse models

PURPOSE

Tumor cells, in contrast to normal cells, frequently overexpress heat shock protein 70 (Hsp70) in the cytosol, present it on their cell surface, and actively release it. Therefore, soluble Hsp70 (sHsp70) was investigated as a potential tumor biomarker for monitoring the outcome of radiation therapy.

METHODS AND MATERIALS

Plasma from mice bearing membrane Hsp70 (mHsp70)-positive FaDu human squamous cell carcinoma of the head and neck and spontaneous pancreatic ductal adenocarcinoma (PDAC) was investigated. A cohort of mice with FaDu tumors (0.32 cm(3)) was irradiated with 30 Gy, and plasma was collected 24 hours after irradiation, after the tumors had shrunk to 50% of their starting volume and after complete remission. sHsp70 levels in the plasma were quantified by enzyme-linked immunosorbent assay.

RESULTS

sHsp70 levels were significantly higher in the blood of tumor-bearing mice than that of control animals. A correlation between increasing sHsp70 plasma levels and tumor volume in the range of 0.01 cm(3) to 0.66 cm(3) was observed. Radiation-induced regression of the tumors was associated with significantly decreased sHsp70 levels, which returned to the level of control animals after complete remission.

CONCLUSION

We propose sHsp70 as an innovative biomarker for detecting tumors and for monitoring the clinical outcome of radiation therapy in cancer patients.