Human heat shock protein 70 enhances tumor antigen presentation through complex formation and intracellular antigen delivery without innate immune signaling

Diversity of extracellular HSP70 in cancer: advancing from a molecular biomarker to a novel therapeutic target

Heat shock protein 70 (HSP70) is a highly conserved protein functioning as a "molecular chaperone", which is integral to protein folding and maturation. In addition to its high expression within cells upon stressful challenges, HSP70 can be translocated to the cell membrane or released from cells in free form or within extracellular vesicles (EVs). Such trafficking of HSP70 is also present in cancer cells, as HSP70 is overexpressed in various types of patient samples across a range of common malignancies, signifying that extracellular HSP70 (eHSP70) can serve as a tumor biomarker. eHSP70 is involved in a broad range of cancer-related events, including cell proliferation and apoptosis, extracellular matrix (ECM) remodeling, epithelial-mesenchymal transition (EMT), angiogenesis, and immune response. eHSP70 can also induce cancer cell resistance to various treatments, such as chemotherapy, radiotherapy, and anti-programmed death-1 (PD-1) immunotherapy. Though the role of eHSP70 in tumors is contradictory, characterized by both pro-tumor and anti-tumor effects, eHSP70 serves as a promising target in cancer treatment. In this review, we comprehensively summarized the current knowledge about the role of eHSP70 in cancer progression and treatment resistance and discussed the feasibility of eHSP70 as a cancer biomarker and therapeutic target.

Harnessing Hyperthermia: Molecular, Cellular, and Immunological Insights for Enhanced Anticancer Therapies

Hyperthermia, the raising of tumor temperature (≥39°C), holds great promise as an adjuvant treatment for cancer therapy. This review focuses on 2 key aspects of hyperthermia: its molecular and cellular effects and its impact on the immune system. Hyperthermia has profound effects on critical biological processes. Increased temperatures inhibit DNA repair enzymes, making cancer cells more sensitive to chemotherapy and radiation. Elevated temperatures also induce cell cycle arrest and trigger apoptotic pathways. Furthermore, hyperthermia modifies the expression of heat shock proteins, which play vital roles in cancer therapy, including enhancing immune responses. Hyperthermic treatments also have a significant impact on the body's immune response against tumors, potentially improving the efficacy of immune checkpoint inhibitors. Mild systemic hyperthermia (39°C-41°C) mimics fever, activating immune cells and raising metabolic rates. Intense heat above 50°C can release tumor antigens, enhancing immune reactions. Using photothermal nanoparticles for targeted heating and drug delivery can also modulate the immune response. Hyperthermia emerges as a cost-effective and well-tolerated adjuvant therapy when integrated with immunotherapy. This comprehensive review serves as a valuable resource for the selection of patient-specific treatments and the guidance of future experimental studies.

Association of elevated extracellular HSP72 in albuminuria with systemic inflammation and disease progression in type 2 diabetic kidney disease

BACKGROUND

Sub-clinical inflammation in hyperglycemia is tied to the pathogenesis of diabetic kidney disease (DKD). Though well known for its immunostimulatory function, the significance of extracellular heat shock protein 72 (eHSP72) in DKD is not well studied. We aimed to determine the association of extracellular HSP72 with systemic inflammation and the progression of DKD, and explore its possible clinical significance in DKD.

METHODS

160 type 2 diabetic individuals were enrolled in the study. Their anthropometric data, routine biochemical parameters, urinary renal function parameters, and blood count parameters were estimated. Plasma from patients' blood samples were used to estimate HSP72 and interleukin 1β (IL-1β) using sandwich immunoassays.

RESULTS

Plasma eHSP72 is elevated in DKD. Pairwise comparisons showed the drastic elevation of eHSP72 in the presence of albuminuria. A significant positive relationship was observed between plasma levels of eHSP72 and IL-1β. eHSP72 levels did not statistically differ between micro and macro-albuminuric DKD. However, it was inversely associated with estimated glomerular filtration rate, the index of disease severity, independent of age, gender, diabetes duration and absolute monocyte count. At a cutoff of 0.52 ng/ml, with sensitivity of 64.1 % and specificity of 69.2 %, plasma eHSP72 differentiated the presence of DKD in type 2 diabetics with statistical significance.

CONCLUSION

The positive relationship of eHSP72 and IL-1β with worsening DKD likely indicates their participation in immunostimulatory pathways of renal fibrosis. eHSP72 may be closely linked to albuminuria-induced tubular injury and likely contributes to fibrotic changes in the progression of DKD. From our study, we infer the possible clinical significance of eHSP72 as a marker of sub-clinical renal damage in DKD, and the implication of IL-1β-associated mechanisms in DKD progression.

Polymeric nanoparticle-based nanovaccines for cancer immunotherapy

Therapeutic cancer vaccines, which are designed to amplify tumor-specific T cell responses, have been envisioned as one of the most powerful tools for effective cancer immunotherapy. However, increasing the potency, quality and durability of the vaccine response remains a big challenge. In recent years, materials-based delivery systems focusing on the co-delivery of antigens and adjuvants to enhance cancer vaccination therapy have attracted increasing interest. Among various materials, polymeric nanoparticles (NPs) with different physicochemical properties which can incorporate multiple immunological cues are of great interest. In this review, the recent progress in the design and construction of both ex vivo subunit and in situ cancer vaccines using polymeric NPs is summarized. Especially, we will focus on how these NPs improve the adjuvanticity of vaccines. The design principles of polymeric NPs for ex vivo subunit cancer vaccines and in situ cancer vaccination are also discussed. Finally, we want to briefly discuss molecular chaperones in cancer immunity and the applications of our unique self-assembly mixed shell polymeric micelle-based nanochaperones for cancer vaccines.

Evaluation of the Small Heat Shock Protein Family Members HSPB2 and HSPB3 in Bladder Cancer Prognosis and Progression

Bladder cancer (BlCa) represents the sixth most commonly diagnosed type of male malignancy. Due to the clinical heterogeneity of BlCa, novel markers would optimize treatment efficacy and improve prognosis. The small heat shock proteins (sHSP) family is one of the major groups of molecular chaperones responsible for the maintenance of proteome functionality and stability. However, the role of sHSPs in BlCa remains largely unknown. The present study aimed to examine the association between HSPB2 and HSPB3 expression and BlCa progression in patients, and to investigate their role in BlCa cells. For this purpose, a series of experiments including reverse transcription-quantitative PCR, Western blotting, MTT assay and flow cytometry were performed. Initial analyses revealed increased vs. human transitional carcinoma cells, expression levels of the HSPB2 and HSPB3 genes and proteins in high grade BlCa cell lines. Therefore, we then evaluated the clinical significance of the HSPB2 and HSPB3 genes expression levels in bladder tumor samples and matched adjusted normal bladder specimens. Total RNA from 100 bladder tumor samples and 49 paired non-cancerous bladder specimens were isolated, and an accurate SYBR-Green based real-time quantitative polymerase chain reaction (qPCR) protocol was developed to quantify HSPB2 and HSPB3 mRNA levels in the two cohorts of specimens. A significant downregulation of the HSPB2 and HSPB3 genes expression was observed in bladder tumors as compared to matched normal urothelium; yet, increased HSPB2 and HSPB3 levels were noted in muscle-invasive (T2-T4) vs. superficial tumors (TaT1), as well as in high-grade vs. low-grade tumors. Survival analyses highlighted the significantly higher risk for post-treatment disease relapse in TaT1 patients poorly expressing HSPB2 and HSPB3 genes; this effect tended to be inverted in advanced disease stages (muscle-invasive tumors) indicating the biphasic impact of HSPB2, HSPB3 genes in BlCa progression. The pro-survival role of HSPB2 and HSPB3 in advanced tumor cells was also evident by our finding that HSPB2, HSPB3 genes expression silencing in high grade BlCa cells enhanced doxorubicin toxicity. These findings indicate that the HSPB2, HSPB3 chaperone genes have a likely pro-survival role in advanced BlCa; thus, they can be targeted as novel molecular markers to optimize treatment efficacy in BlCa and to limit unnecessary interventions.

In Situ Antigen-Capturing Nanochaperone Toward Personalized Nanovaccine for Cancer Immunotherapy

Personalized cancer vaccination using nanomaterials holds great potential for cancer immunotherapy. Here, a nanochaperone (PBA-nChap) is tailored for in situ capture of tumor-associated antigens (TAAs) to improve cancer immunotherapy. The PBA-nChap is capable of i) efficiently capturing TAAs in situ; ii) protecting TAAs from degradation; iii) transporting TAAs to antigen-presenting cells and promoting cross-presentation. Intratumor injection of PBA-nChap in combination with pretreatment with photodynamic therapy (PDT) significantly enhances immune response and exhibits excellent antitumor efficacy. Moreover, nanovaccine prepared by simply co-culturing PBA-nChap with tumor cell fragments from surgery resected primary tumor in vitro synergized with immune checkpoint blockade (ICB) therapy can effectively inhibit tumor recurrence and metastasis after an operation. This work provides a promising platform for personalized cancer vaccination.

The Formation of Melanocyte Apoptotic Bodies in Vitiligo and the Relocation of Vitiligo Autoantigens under Oxidative Stress

Background

Oxidative stress has a vital role in the early stages of vitiligo. Autoantigens released from apoptotic melanocytes (MC) under oxidative stress are involved in the presentation and recognition of antigens. However, the transport of autoantigens to the cell surface and their release to the extracellular environment are still unclear. Apoptotic bodies (ABs) have always been considered as a key source of immunomodulators and autoantigens. Yet, the role of ABs in the immune mechanism of vitiligo is still unknown.

Purpose

To explore whether MC's autoantigens translocate into ABs during oxidative stress-induced apoptosis and study the molecular mechanisms underlying autoantigen migration and AB formation.

Methods

PIG3V (an immortalized human vitiligo melanocyte cell line) were treated with H₂O₂, and ABs were separated. Transmission electron microscopy, flow cytometry, Western blot, mass spectrometry, and other methods were used to determine the relocation of specific antigens in PIG3V cells to ABs. After pretreatment with specific inhibitors (Rho kinase (Y-27632), myosin light chain kinase (MLCK, ML-9), pan-caspase (zVAD-FMK), and JNK (SP600125)), the pathway of autoantigen translocation into ABs and the formation of apoptotic bodies were determined.

Results

When treated with 0.8 mM H₂O₂, ABs were released from these cells. Autoantigens such as tyrosinase-related protein 1 (TYRP-1) and cleavage nuclear membrane antigen Lamin A/C (Asp230) were concentrated in ABs. The expression of autoantigens and the formation of ABs increased in a time- and dose-dependent manner after treatment with H₂O₂, while the application of specific inhibitors inhibited the formation of apoptotic bodies, i.e., the expression of antigens.

Conclusion

Vitiligo autoantigens translocate into ABs in the process of apoptosis induced by oxidative stress. The cytoskeletal protein activation pathway and the JNK-related apoptosis pathway are involved in the transport of autoantigens and the formation of ABs. ABs may be the key bridge between MC cell apoptosis and cellular immunity.

The Role of Extracellular HSP70 in the Function of Tumor-Associated Immune Cells

Simple Summary

The intracellular heat shock protein 70 (HSP70) is essential for cells to respond to stress, for instance, by refolding damaged proteins or inhibiting apoptosis. However, in cancer, HSP70 is overexpressed and can translocate to the extracellular milieu, where it emerged as an important modulator of tumor-associated immune cells. By targeting the tumor microenvironment (TME) through different mechanisms, extracellular HSP70 can trigger pro- or anti-tumorigenic responses. Therefore, understanding the pathways and their consequences is crucial for therapeutically targeting cancer and its surrounding microenvironment. In this review, we summarize current knowledge on the translocation of extracellular HSP70. We further elucidate its functions within the TME and provide an overview of potential therapeutic options.

Abstract

Extracellular vesicles released by tumor cells (T-EVs) are known to contain danger-associated molecular patterns (DAMPs), which are released in response to cellular stress to alert the immune system to the dangerous cell. Part of this defense mechanism is the heat shock protein 70 (HSP70), and HSP70-positive T-EVs are known to trigger anti-tumor immune responses. Moreover, extracellular HSP70 acts as an immunogen that contributes to the cross-presentation of major histocompatibility complex (MHC) class I molecules. However, the release of DAMPs, including HSP70, may also induce chronic inflammation or suppress immune cell activity, promoting tumor growth. Here, we summarize the current knowledge on soluble, membrane-bound, and EV-associated HSP70 regarding their functions in regulating tumor-associated immune cells in the tumor microenvironment. The molecular mechanisms involved in the translocation of HSP70 to the plasma membrane of tumor cells and its release via exosomes or soluble proteins are summarized. Furthermore, perspectives for immunotherapies aimed to target HSP70 and its receptors for cancer treatment are discussed and presented.

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.

Local hyperthermia combined with CTLA-4 blockade induces both local and abscopal effects in a murine breast cancer model

PURPOSE

To evaluate the antitumor efficacy in local and distant tumors induced by local hyperthermia with CTLA-4 blockade.

METHODS

A mouse breast cancer cell line was inoculated into both sides of the legs of mice. The mice were treated with three administrations of CTLA-4 blockade, a single application of local hyperthermia (42.5 °C for 20 min) to the tumor on one side of the leg, or the combination of the two. Tumor growth in locally heated tumors (HT tumors) and unheated distant tumors (UnHT tumors) and overall survival were evaluated.

RESULTS

In the combination group, tumor volume significantly decreased for both HT and UnHT tumors compared with the tumors in the untreated and local hyperthermia monotherapy groups. Remarkable efficacy was only observed in the combination therapy group, in which 7 of 18 mice responded to HT and UnHT tumors, with significant prolonged overall survival.

CONCLUSIONS

Combination therapy enhanced the antitumor response not only in HT tumors but also in UnHT tumors and prolonged overall survival.

Lymph node-targeted immune-activation mediated by imiquimod-loaded mesoporous polydopamine based-nanocarriers

Toll-like receptor (TLR) agonists are the potent stimulants of innate immune system and hold promises as an adjuvant for anticancer immunotherapy. Unfortunately, most of them are limited by a prompt dissemination, and thus caused "wasted inflammation". Hence, how to restrict their action radius into lymphoid tissues is of great relevance to enhance their efficacy and concomitantly alleviates the side effects. Here, imiquimod (R837), a TLR 7 agonist, was loaded into mesoporous polydopamine (MPDA) nanocarriers with high efficiency. Moreover, its surface was modified by polyvinyl pyrrolidone (PVP) to enhance their lymphatic drainage ability. These nano-adjuvants have obvious advantages in promoting dendritic cell (DC) maturation in comparison to free R837. Moreover, their transportation and retention ability in proximal lymph nodes (LNs) were also confirmed, by which lymphatic drug exposure can be maximized to a great extent. Consequently, effective DC activation and CD8⁺ T cell responses were observed as expected by R837 released in draining LNs. This effect was further enhanced by the presence of endogenous tumor antigens from apoptosis debris induced by MPDA-based photothermal effect, and thus led to the growth inhibition of subcutaneous B16 melanomas. The results demonstrated the great potency against melanoma of the designed PVP-MPDA@R837 nano-adjuvants by combining photothermal conversion property of MPDA with lymphatic-focused immune-activation.

A Three-in-One Immunotherapy Nanoweapon via Cascade-Amplifying Cancer-Immunity Cycle against Tumor Metastasis, Relapse, and Postsurgical Regrowth

The antitumor immune response involves a cascade of three phases, namely, antigen presentation (Phase I), lymphocyte activation and proliferation/differentiation (Phase II), and tumor elimination (Phase III). Therefore, an ideal immunotherapy nanoplatform is one that can simultaneously execute these three phases. However, it is of great challenge to develop a single immunotherapy nanoplatform which can deliver individual immunoagent to their on-demand target sites for simultaneously tailoring three phases because of the different target sites restricted by three phases. Herein, for the first time we reported a three-in-one immunotherapy nanoplatform that can simultaneously execute these three phases. Chlorin e6 (Ce6)-conjugated hyaluronic acid (HC), dextro-1-methyl tryptophan (1-mt)-conjugated polylysine (PM) and anti-PD-L1 monoclonal antibodies (aPD-L1) were rationally designed as aPD-L1@HC/PM NPs via an assembling strategy. The step-by-step detachment of the antigen from near-infrared light irradiated HC component, the indoleamine-pyrrole 2,3-dioxygenase (IDO) pathway inhibitor 1-mt, and the anti-PD-L1 toward their on-demand target sites demonstrated the simultaneous tailoring of Phase I, Phase II, and Phase III, respectively, of the immunotherapy. The aPD-L1@HC/PM NPs were verified to be an excellent immunotherapy nanoplatform against tumor metastasis, relapse, and postsurgical regrowth because of the cascade-amplifying cancer-immunity cycle. The present all-immunity-phase-boosted immunotherapy strategy is of great interest for designing excellent immunotherapy treatments.

Immunosurveillance of cancer cell stress

Cancer development is tightly controlled by effector immune responses that recognize and eliminate malignantly transformed cells. Nonetheless, certain immune subsets, such as tumor-associated macrophages, have been described to promote tumor growth, unraveling a double-edge role of the immune system in cancer. Cell stress can modulate the crosstalk between immune cells and tumor cells, reshaping tumor immunogenicity and/or immune function and phenotype. Infiltrating immune cells are exposed to the challenging conditions typically present in the tumor microenvironment. In return, the myriad of signaling pathways activated in response to stress conditions may tip the balance toward stimulation of antitumor responses or immune-mediated tumor progression. Here, we explore how distinct situations of cellular stress influence innate and adaptive immunity and the consequent impact on cancer establishment and progression.

Heat shock proteins: A dual carrier-adjuvant for an anti-drug vaccine against heroin

Heroin is a highly abused opioid that has reached epidemic status within the United States. Yet, existing therapies to treat addiction are inadequate and frequently result into rates of high recidivism. Vaccination against heroin offers a promising alternative therapeutic option but requires further development to enhance the vaccine's performance. Hsp70 is a conserved protein with known immunomodulatory properties and is considered an excellent immunodominant antigen. Within an antidrug vaccine context, we envisioned Hsp70 as a potential dual carrier-adjuvant, wherein immunogenicity would be increased by co-localization of adjuvant and antigenic drug hapten. Recombinant Mycobacterium tuberculosis Hsp70 was appended with heroin haptens and the resulting immunoconjugate granted anti-heroin antibody production and blunted heroin-induced antinociception. Moreover, Hsp70 as a carrier protein surpassed our benchmark Her-KLH cocktail through antibody-mediated blockade of 6-acetylmorphine, the main mediator of heroin's psychoactivity. The work presents a new avenue for exploration in the use of hapten-Hsp70 conjugates to elicit anti-drug immune responses.

Heat shock proteins 60 and 70 are associated with long-term outcome of T1-stage high-grade urothelial tumors of the bladder treated with intravesical Bacillus Calmette-Guérin immunotherapy

OBJECTIVES

High-grade nonmuscle-invasive urothelial tumors of the bladder that fail intravesical Bacillus Calmette-Guérin (BCG) immunotherapy are at the highest risk of progression. Initial evidence links heat shock protein expression levels and outcome of bladder cancer after BCG treatment. We aimed to determine the association between HSP60, 70, and 90 expression levels and long-term outcomes of T1 high-grade (T1HG) urothelial bladder tumors treated with BCG immunotherapy.

MATERIALS AND METHODS

Data of 54 consecutive patients with primary T1HG bladder tumors who underwent transurethral resection between 2002 and 2008 and received at least an induction course of BCG were reviewed. Immunohistochemical staining for heat shock protein (HSP)60, 70, and 90 were performed on resected specimens. Study outcomes included disease recurrence and progression. The association between HSP expression levels and outcomes were evaluated with univariable and multivariable Cox proportional hazards models.

RESULTS

During a median follow-up of 9.6 years, 25 patients had a disease recurrence and 14 patients a disease progression. Estimated 5-year recurrence and progression-free survival were 59% and 81%, respectively. On multivariable analyses, HSP60 staining >65% was associated with a higher risk for progression (hazard ratio [HR] = 3.96, 95% confidence interval [CI] 1.35-11.58, P = 0.012), and HSP70 staining >5% was associated with a decreased risk for progression (HR = 0.33, 95% CI 0.11-0.98, P = 0.045), and recurrence (HR = 0.29, 95% CI 0.13-0.65, P = 0.003). HSP90 expression was not associated with disease recurrence or progression. Five patients had both a HSP60 staining >65% and a HSP70 staining ≤5% all of whom recurred at a median time of 6 months (interquartile range 3, 16) and 80% of whom progressed at a median time of 26 months (interquartile range 5, 60).

CONCLUSIONS

HSP60 and 70 cellular expression levels are associated with long-term outcome following BCG treatment of T1HG urothelial bladder tumors. These findings, if further validated, may be used to better stratify the risk of disease recurrence and progression in this group of patients.

Construction and Characterization of Adenovirus Vectors Encoding Aspartate-β-Hydroxylase to Preliminary Application in Immunotherapy of Hepatocellular Carcinoma

Dendritic cells (DCs) harboring tumor-associated antigen are supposed to be a potential immunotherapy for hepatocellular carcinoma (HCC). Aspartate-β-hydroxylase (AAH), an overexpressed tumor-associated cell surface protein, is considered as a promising biomarker and therapeutic target for HCC. In this study, we constructed adenovirus vector encoding AAH gene by gateway recombinant cloning technology and preliminarily explored the antitumor effects of DC vaccines harboring AAH. Firstly, the total AAH mRNA was extracted from human HCC tissues; the cDNA was amplified by RT-PCR, verified, and sequenced after TA cloning. Gateway technology was used and the obtained 18T-AAH was used as a substrate, to yield the final expression vector Ad-AAH-IRES2-EGFP. Secondly, bone marrow-derived DCs were infected by Ad-AAH-IRES2-EGFP to yield AAH-DC vaccines. Matured DCs were demonstrated by increased expression of CD11c, CD80, and MHC-II costimulatory molecules. A dramatically cell-killing effect of T lymphocytes coculturing with AAH-DCs on HepG2 HCC cell line was demonstrated by CCK-8 and FCM assays in vitro. More importantly, in an animal experiment, the lysis effect of cytotoxic T lymphocytes (CTLs) on HepG2 cells in the AAH-DC group was stronger than that in the control groups. In conclusion, the gateway recombinant cloning technology is a powerful method of constructing adenovirus vector, and the product Ad-AAH-IRES2-EGFP may present as a potential candidate for DC-based immunotherapy of HCC.

Immunotherapy based on dendritic cells pulsed with CTPFoxM1 fusion protein protects against the development of hepatocellular carcinoma

Application of dendritic cells (DCs) pulsed with tumor-associated antigens is considered attractive in immunotherapy for hepatocellular carcinoma (HCC). In order to efficiently prime tumor-associated antigens specific for cytotoxic T lymphocytes (CTLs), it is important that DCs present tumor-associated antigens on MHC class I. MHC class I generally present endogenous antigens expressed in the cytosol. In this study, we developed a new antigen delivery tool based on cross presentation of exogenous antigens in DCs by using cytoplasmic transduction peptide (CTP). CTP protein could transduce FoxM1 tumor antigen into the cytosol of DCs, and CTP-FoxM1 fusion protein could stimulate activation and maturation of DCs. DCs pulsed with CTP-FoxM1 could induce specific CTLs. More importantly, the immunity induced by DCs loaded with CTP-FoxM1 could significantly inhibit tumor growth and metastasis in HCC-bearing mice, which was more potent than that induced by DCs loaded with FoxM1 or CTP, alone. Our results indicate that DCs pulsed with CTP-FoxM1 might be a promising vaccine candidate for HCC therapy and provide new insight into the design of DC-based immunotherapy.

Hsp70: A Cancer Target Inside and Outside the Cell

Heat shock protein 70 (Hsp70) is the most ubiquitous stress-inducible chaperone. It accumulates in the cells in response to a wide variety of physiological and environmental insults including anticancer chemotherapy, thus allowing the cell to survive to lethal conditions. Intracellular Hsp70 is viewed as a cytoprotective protein. Indeed, this protein can inhibit key effectors of the apoptotic and autophagy machineries. In cancer cells, the expression of Hsp70 is abnormally high, and Hsp70 may participate in oncogenesis and in resistance to chemotherapy. In rodent models, Hsp70 overexpression increases tumor growth and metastatic potential. Depletion or inhibition of Hsp70 frequently reduces the size of the tumors and can even cause their complete involution. However, HSP70 is also found in the extra-cellular space where it may signal via membrane receptors or endosomes to alter gene transcription and cellular function. Overall, Hsp70 extracellular function is believed to be immnunogenic and the term chaperokine to define the extracellular chaperones such as Hsp70 has been advanced. In this chapter the knowledge to date, as well as some emerging paradigms about the intra- and extra-cellular functions of Hsp70, are presented. The strategies targeting Hsp70 that are being developed in cancer therapy will also be discussed.

Human DKK1 and human HSP70 fusion DNA vaccine induces an effective anti-tumor efficacy in murine multiple myeloma

Dickkopf-1 (DKK1) is an ideal target for the immunotherapy of multiple myeloma. Heat Shock protein70 (HSP70) is a class of important molecular chaperone to promote antigen presentation. Homologous xenogeneic antigens can enhance immunogenicity and induce stronger anti-tumor immune response than that of allogeneic ones. Therefore, we constructed human DKK1 and human HSP70 DNA fusion vaccine (hDKK1-hHSP70), and then determined its anti-tumor immuno- genicity and anti-tumor effects on immunizing BALB/c mice already inoculated with NS-1 murine multiple myeloma cells in prophylactic and therapeutic models using cytotoxic T lymphocytes, enzyme-lined immunosorbent assay, flow cytometry, immunohistochemistry and Hochest staining. The side effects of vaccines were also monitored. We found that hDKK1-hHSP70 fusion vaccine could significantly inhibit tumor growth and prolonged the survival of the mice, whether prophylactic or therapeutic immunotherapy in vivo, by eliciting both humoral and cellular tumor-specific immune responses. A significant decrease of proliferation and increase of apoptosis were also observed in the tumor tissues injected with hDKK1-hHSP70 vaccine. These findings showed the xenogeneic homologous vaccination had stronger immunogenicity and minimal toxicity. Our study may provide an effective and safety immonutheraphy strategy for multiple myeloma.

Endogenous Heat-Shock Protein Induction with or Without Radiofrequency Ablation or Cryoablation in Patients with Stage IV Melanoma

Lessons Learned.

Percutaneous thermal ablation combined with in situ granulocyte‐macrophage colony‐stimulating factor cytokine therapy was technically feasible and well tolerated.

No significant clinical or immunologic responses were seen.

Background.

Melanoma tumor‐derived heat‐shock proteins (HSPs) and HSP‐peptide complexes can elicit protective antitumor responses. The granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) chemokine can also promote uptake and processing by professional antigen presenting cells (APCs). On this basis, we designed a pilot study of percutaneous thermal ablation as a means to induce heat‐shock protein vaccination plus GM‐CSF to determine safety and preliminary antitumor activity of this combination.

Materials and Methods.

This study was designed to assess overall safety of percutaneous ablation combined with GM‐CSF for unresectable, metastatic melanoma including uveal and mucosal types. All patients received heat‐shock therapy (42°C for 30 minutes), then received one of three treatments: (a) intralesional GM‐CSF (500 mcg standard dose); (b) radiofrequency ablation (RFA) + GM‐CSF; or (c) cryoablation plus GM‐CSF. The primary endpoint of the study was the induction of endogenous HSP70 and melanoma‐specific cytotoxic T lymphocytes (CTL).

Results.

Nine patients (three per study arm) were enrolled. No dose‐limiting toxicity was observed as specified per protocol. All patients developed progressive disease and went on to receive alternative therapy. Median overall survival (OS) was 8.2 months (95% confidence interval [CI] 2–17.2). The study was not powered to detect a difference in clinical outcome among treatment groups.

Conclusion.

Percutaneous thermal ablation plus GM‐CSF was well tolerated, technically feasible, and demonstrated an acceptable adverse event profile comparable to conventional RFA and cryoablation. While HSP70 was induced following therapy, the degree of HSP70 elevation was not associated with clinical outcome or induced CTL responses. While percutaneous thermal ablation plus GM‐CSF combinations including checkpoint inhibitors could be considered in future studies, the use of GM‐CSF remains experimental and for use in the context of clinical trials.

Human monocyte-derived dendritic cells exposed to hyperthermia show a distinct gene expression profile and selective upregulation of IGFBP6

Fever plays a role in activating innate immunity while its relevance in activating adaptive immunity is less clear. Even brief exposure to elevated temperatures significantly impacts on the immunostimulatory capacity of dendritic cells (DCs), but the consequences on immune response remain unclear. To address this issue, we analyzed the gene expression profiles of normal human monocyte-derived DCs from nine healthy adults subjected either to fever-like thermal conditions (39°C) or to normal temperature (37°C) for 180 minutes. Exposure of DCs to 39°C caused upregulation of 43 genes and downregulation of 24 genes. Functionally, the up/downregulated genes are involved in post-translational modification, protein folding, cell death and survival, and cellular movement. Notably, when compared to monocytes, DCs differentially upregulated transcription of the secreted protein IGFBP-6, not previously known to be specifically linked to hyperthermia. Exposure of DCs to 39°C induced apoptosis/necrosis and resulted in accumulation of IGFBP-6 in the conditioned medium at 48 h. IGFBP-6 may have a functional role in the hyperthermic response as it induced chemotaxis of monocytes and T lymphocytes, but not of B lymphocytes. Thus, temperature regulates complex biological DC functions that most likely contribute to their ability to induce an efficient adaptive immune response.

Acid-Activatable Versatile Micelleplexes for PD-L1 Blockade-Enhanced Cancer Photodynamic Immunotherapy

Photodynamic therapy (PDT) has emerged as a promising clinical modality for cancer therapy due to its ability to initiate an antitumor immune response. However, PDT-mediated cancer immunotherapy is severely impaired by tumor-cell immunosuppression of host T cell antitumor activity through the programmed cell death 1 ligand (PD-L1) and programmed cell death receptor 1 (PD-1) (PD-L1-PD-1) immune checkpoint pathway. Here, we demonstrate that PDT-mediated cancer immunotherapy can be augmented by PD-L1 knockdown (KD) in tumor cells. We rationally designed a versatile micelleplex by integrating an acid-activatable cationic micelle, photosensitizer (PS), and small interfering RNA (siRNA). The micelleplex was inert at physiological pH conditions and activated only upon internalization in the acidic endocytic vesicles of tumor cells for fluorescence imaging and PDT. Compared to PDT alone, the combination of PDT and PD-L1 KD showed significantly enhanced efficacy for inhibiting tumor growth and distant metastasis in a B16-F10 melanoma xenograft tumor model. These results suggest that acid-activatable micelleplexes utilizing PDT-induced cancer immunotherapy are more effective when combined with siRNA-mediated PD-L1 blockade. This study could provide a general strategy for enhancing the therapy efficacy of photodynamic cancer therapy.

Cryo-thermal therapy elicits potent anti-tumor immunity by inducing extracellular Hsp70-dependent MDSC differentiation

Achieving control of metastatic disease is a long-sought goal in cancer therapy. Treatments that encourage a patient’s own immune system are bringing new hopes in reaching such a goal. In clinic, local hyperthermia and cryoablation have been explored to induce anti-tumor immune responses against tumors. We have also developed a novel therapeutic modality of cryo-thermal treatment by alternating liquid nitrogen (LN2) cooling and radio frequency (RF) heating, and better therapeutic effect was achieved in treating metastatic cancer in animal model. In this study, we investigated the mechanism of systemic immune response elicited by cryo-thermal therapy. In the 4T1 murine mammary carcinoma model, we found that local cryo-thermal therapy resulted in a considerable reduction of distant lung metastases, and improved long-term survival. Moreover, results of tumor re-challenge experiments indicated generation of a strong tumor-specific immune memory after the local treatment of primary tumors. Our further study indicated that cryo-thermal therapy caused an elevated extracellular release of Hsp70. Subsequently, Hsp70 induced differentiation of MDSCs into mature DCs, contributing to the relief of MDSCs-mediated immunosuppression and ultimately the activation of strong anti-tumor immune response. Our findings reveal new insight into the mechanism of robust therapeutic effects of cryo-thermal therapy against metastatic cancers.

Spatiotemporal Regulation of Hsp90-Ligand Complex Leads to Immune Activation

Although heat shock proteins (HSPs) primarily play a pivotal role in the maintenance of cellular homeostasis while reducing extracellular as well as intracellular stresses, their role in immunologically relevant scenarios, including activation of innate immunity as danger signals, antitumor immunity, and autoimmune diseases, is now gaining much attention. The most prominent feature of HSPs is that they function both in their own and as an HSP–ligand complex. We here show as a unique feature of extracellular HSPs that they target chaperoned molecules into a particular endosomal compartment of dendritic cells, thereby inducing innate and adaptive immune responses via spatiotemporal regulation.

Transcatheter arterial embolization combined with radiofrequency ablation activates CD8(+) T-cell infiltration surrounding residual tumors in the rabbit VX2 liver tumors

Purpose

To evaluate the effect of transcatheter arterial embolization (TAE) combined with radiofrequency ablation (RFA) treatment (TAE + RFA) on the expression of heat shock protein 70 (HSP70) in residual tumors and explore the relationship between the HSP70 and CD8⁺ T-cell infiltrate surrounding residual tumors in the rabbit VX2 liver tumor model.

Materials and methods

Animals with VX2 liver tumors were randomized into four groups (control, TAE, RFA, and TAE + RFA) with 15 rabbits in each group. Five rabbits in each group were sacrificed on days 1, 3, and 7 after treatment. HSP70 expression and infiltration of CD8⁺ T-cells in the liver and residual tumors surrounding the necrosis zone were detected by immunohistochemistry staining. The maximal diameters of tumor necrosis, numbers of metastases, and tumor growth rate were compared on day 7 after treatment.

Results

TAE + RFA achieved larger maximal diameter of tumor necrosis, lower tumor growth rate, and fewer metastatic lesions, compared with other treatments on day 7. The number of CD8⁺ T-cells in the TAE + RFA group was significantly higher than in other groups on days 1, 3, and 7. There was a positive correlation between HSP70 expression level and infiltration of CD8⁺ T-cells surrounding the residual tumor on day 1 (r=0.9782, P=0.012), day 3 (r=0.93, P=0.021), and day 7 (r=0.8934, P=0.034).

Conclusion

In the rabbit VX2 liver tumor model, TAE + RFA activated the highest number of CD8⁺ T-cells surrounding residual tumors. TAE + RFA appears to be a beneficial therapeutic modality for tumor control and antitumor immune response in this model.

Targeting Hsp70: A possible therapy for cancer

In all organisms, heat-shock proteins (HSPs) provide an ancient defense system. These proteins act as molecular chaperones by assisting proper folding and refolding of misfolded proteins and aid in the elimination of old and damaged cells. HSPs include Hsp100, Hsp90, Hsp70, Hsp40, and small HSPs. Through its substrate-binding domains, Hsp70 interacts with wide spectrum of molecules, ranging from unfolded to natively folded and aggregated proteins, and provides cytoprotective role against various cellular stresses. Under pathophysiological conditions, the high expression of Hsp70 allows cells to survive with lethal injuries. Increased Hsp70, by interacting at several points on apoptotic signaling pathways, leads to inhibition of apoptosis. Elevated expression of Hsp70 in cancer cells may be responsible for tumorigenesis and for tumor progression by providing resistance to chemotherapy. In contrast, inhibition or knockdown of Hsp70 reduces the size of tumors and can cause their complete regression. Moreover, extracellular Hsp70 acts as an immunogen that participates in cross presentation of MHC-I molecules. The goals of this review are to examine the roles of Hsp70 in cancer and to present strategies targeting Hsp70 in the development of cancer therapeutics.

The limited capacity of malignant glioma-derived exosomes to suppress peripheral immune effectors

Tumor-derived microvesicular exosomes permit intercellular communication both locally and systemically by delivering a snapshot of the tumor cell's constituents. We thus investigated whether exosomes mediate malignant glioma's facility for inducing peripheral immunosuppression. In Western blot and RT-PCR analyses, glioma-derived exosomes displayed exosome-specific markers, but failed to recapitulate the antigen-presentation machinery, surface co-modulatory signals, or immunosuppressive mediator status of their parent tumor cells. Treatment with glioma-derived exosomes promoted immunosuppressive HLA-DR(low) monocytic phenotypes, but failed to induce monocytic PD-L1 expression or alter the activation of cytotoxic T-cells from patients' peripheral blood by FACS and RT-PCR analyses. Our results suggest that malignant glioma-derived exosomes are restricted in their capacity to directly prime peripheral immunosuppression.

Sulfatide-Hsp70 interaction promotes Hsp70 clustering and stabilizes binding to unfolded protein

The 70-kDa heat shock protein (Hsp70), one of the major stress-inducible molecular chaperones, is localized not only in the cytosol, but also in extracellular milieu in mammals. Hsp70 interacts with various cell surface glycolipids including sulfatide (3'-sulfogalactosphingolipid). However, the molecular mechanism, as well as the biological relevance, underlying the glycolipid-Hsp70 interaction is unknown. Here we report that sulfatide promotes Hsp70 oligomerization through the N-terminal ATPase domain, which stabilizes the binding of Hsp70 to unfolded protein in vitro. We find that the Hsp70 oligomer has apparent molecular masses ranging from 440 kDa to greater than 669 kDa. The C-terminal peptide-binding domain is dispensable for the sulfatide-induced oligomer formation. The oligomer formation is impaired in the presence of ATP, while the Hsp70 oligomer, once formed, is unable to bind to ATP. These results suggest that sulfatide locks Hsp70 in a high-affinity state to unfolded proteins by clustering the peptide-binding domain and blocking the binding to ATP that induces the dissociation of Hsp70 from protein substrates.

Oncolytic vaccines

Oncolytic viruses are ideal platforms for tumor vaccination because they can mediate the direct in situ killing of tumor cells that release a broad array of tumor antigens and alarmins or danger signals thereby cross-priming antitumor cytotoxic T lymphocytes (CTLs), which mediate the indirect killing of uninfected cells. The balance between the direct and indirect killing phases of oncolytic virotherapy is the key to its success and can be manipulated by incorporating various immunomodulatory genes into the oncolytic virus genome. Recently, the interim analysis of a large multicenter Phase III clinical trial for Talimogene laherparepvec, a granulocyte-macrophage colony stimulating factor-armed oncolytic herpes simplex virus, revealed significant improvement in objective response and durable response rates over control arm and a trend toward improved overall survival. Meanwhile, newer oncolytics are being developed expressing additional immunomodulatory transgenes to further enhance cross-priming and the generation of antitumor CTLs and to block the immunosuppressive actions of the tumor microenvironment. Since oncolytic vaccines can be engineered to kill tumor cells directly, modulate the kinetics of the antitumor immune response and reverse the immunosuppressive actions of the tumor, they are predicted to emerge as the preferred immunotherapeutic anticancer weapons of the future.

The complex function of hsp70 in metastatic cancer

Elevated expression of the inducible heat shock protein 70 (Hsp70) is known to correlate with poor prognosis in many cancers. Hsp70 confers survival advantage as well as resistance to chemotherapeutic agents, and promotes tumor cell invasion. At the same time, tumor-derived extracellular Hsp70 has been recognized as a "chaperokine", activating antitumor immunity. In this review we discuss localization dependent functions of Hsp70 in the context of invasive cancer. Understanding the molecular principles of metastasis formation steps, as well as interactions of the tumor cells with the microenvironment and the immune system is essential for fighting metastatic cancer. Although Hsp70 has been implicated in different steps of the metastatic process, the exact mechanisms of its action remain to be explored. Known and potential functions of Hsp70 in controlling or modulating of invasion and metastasis are discussed.

Fusion of Hsp70 to Mage-a1 enhances the potency of vaccine-specific immune responses

Background

Heat shock proteins (HSPs) are capable of promoting antigen presentation of chaperoned peptides through interactions with receptors on antigen presenting cells. This property of HSPs suggests a potential function as an adjuvant-free carrier to stimulate immune responses against a covalently linked fusion partner. MAGE-A1 is a likely candidate for tumor immunotherapy due to its abundant immunogenic epitopes and strict tumor specificity. To analyze the influence of HSP70 conjugation to MAGE-A1, towards developing a novel effective vaccine against MAGE-expressing tumors, we cloned the murine counterpart of the human HSP70 and MAGE-A1 genes.

Methods

Recombinant proteins expressing Mage-a1 (aa 118–219), Hsp70, and Mage-a1-Hsp70 fusion were purified and used to immunize C57BL/6 mice. The humoral and cellular responses elicited against Mage-a1 were measured by ELISA, IFN-γ ELISPOT assay, and cytotoxicity assay.

Results

Immunization of mice with Mage-a1-Hsp70 fusion protein elicited significantly higher Mage-a1-specific antibody titers than immunization with either Mage-a1 alone or a combination of Mage-a1 + Hsp70. The frequency of IFN-γ-producing cells and the cytotoxic T lymphocyte (CTL) activity was also elevated. Consistent with the elevated immune response, immunization with fusion protein induced potent in vivo antitumor immunity against MAGE-a1-expressing tumors.

Conclusions

These results indicate that the fusion of Hsp70 to Mage-a1 can enhance immune responses and anti-tumor effects against Mage-a1-expressing tumors. Fusion of HSP70 to a tumor antigen may greatly enhance the potency of protein vaccines and can potentially be applied to other cancer systems with known tumor-specific antigens. These findings provide a scientific basis for the development of a novel HSP70 and MAGE fusion protein vaccine against MAGE-expressing tumors.

Antitumor immune responses mediated by dendritic cells: How signals derived from dying cancer cells drive antigen cross-presentation

Dendritic cells (DCs) are essential for the induction of adaptive immune responses against malignant cells by virtue of their capacity to effectively cross-present exogenous antigens to T lymphocytes. Dying cancer cells are indeed a rich source of antigens that may be harnessed for the development of DC-based vaccines. In particular, malignant cells succumbing to apoptosis, rather than necrosis, appear to release antigens in a manner that allows for the elicitation of adaptive immune responses. In this review, we describe the processes that mediate the cross-presentation of antigens released by apoptotic cancer cells to CD8⁺ T lymphocytes, resulting in the activation of protective tumor-specific immune responses.

HSP70 and modified HPV 16 E7 fusion gene without the addition of a signal peptide gene sequence as a candidate therapeutic tumor vaccine

Millions of women are currently infected with high-risk human papillomavirus (HPV), which is considered to be a major risk factor for cervical cancer. Thus, it is urgent to develop therapeutic vaccines to eliminate the established infections or HPV-related diseases. In the present study, using the mycobacterium tuberculosis heat shock protein 70 (MtHSP70) gene linked to the modified HPV 16 E7 (mE7) gene, we generated two potential therapeutic HPV DNA vaccines, mE7/MtHSP70 and SigmE7/MtHSP70, the latter was linked to the signal peptide gene sequence of human CD33 at the upstream of the fusion gene. We found that vaccination with the mE7/MtHSP70 DNA vaccine induced a stronger E7-specific CD8+ T cell response and resulted in a more significant therapeutic effect against E7-expressing tumor cells in mice. Our results demonstrated that HSP70 can play a more important role in mE7 and MtHSP70 fusion DNA vaccine without the help of a signal peptide. This may facilitate the use of HSP70 and serve as a significant reference for future study.

Heat shock transcription factor 1 is activated as a consequence of lymphocyte activation and regulates a major proteostasis network in T cells critical for cell division during stress

Heat shock transcription factor 1 (HSF1) is a major transcriptional regulator of the heat shock response in eukaryotic cells. HSF1 is evoked in response to a variety of cellular stressors, including elevated temperatures, oxidative stress, and other proteotoxic stressors. Previously, we demonstrated that HSF1 is activated in naive T cells at fever range temperatures (39.5°C) and is critical for in vitro T cell proliferation at fever temperatures. In this study, we demonstrated that murine HSF1 became activated to the DNA-binding form and transactivated a large number of genes in lymphoid cells strictly as a consequence of receptor activation in the absence of apparent cellular stress. Microarray analysis comparing HSF1(+/+) and HSF1(-/-) gene expression in T cells activated at 37°C revealed a diverse set of 323 genes significantly regulated by HSF1 in nonstressed T cells. In vivo proliferation studies revealed a significant impairment of HSF1(-/-) T cell expansion under conditions mimicking a robust immune response (staphylococcal enterotoxin B-induced T cell activation). This proliferation defect due to loss of HSF1 is observed even under nonfebrile temperatures. HSF1(-/-) T cells activated at fever temperatures show a dramatic reduction in cyclin E and cyclin A proteins during the cell cycle, although the transcription of these genes was modestly affected. Finally, B cell and hematopoietic stem cell proliferation from HSF1(-/-) mice, but not HSF1(+/+) mice, were also attenuated under stressful conditions, indicating that HSF1 is critical for the cell cycle progression of lymphoid cells activated under stressful conditions.

Heat-shock proteins as dendritic cell-targeting vaccines--getting warmer

Heat-shock proteins (hsp) provide a natural link between innate and adaptive immune responses by combining the ideal properties of antigen carriage (chaperoning), targeting and activation of antigen-presenting cells (APC), including dendritic cells (DC). Targeting is achieved through binding of hsp to distinct cell surface receptors and is followed by antigen internalization, processing and presentation. An improved understanding of the interaction of hsp with DC has driven the development of numerous hsp-containing vaccines, designed to deliver antigens directly to DC. Studies in mice have shown that for cancers, such vaccines generate impressive immune responses and protection from tumour challenge. However, translation to human use, as for many experimental immunotherapies, has been slow partly because of the need to perform trials in patients with advanced cancers, where demonstration of efficacy is challenging. Recently, the properties of hsp have been used for development of prophylactic vaccines against infectious diseases including tuberculosis and meningitis. These hsp-based vaccines, in the form of pathogen-derived hsp-antigen complexes, or recombinant hsp combined with selected antigens in vitro, offer an innovative approach against challenging diseases where broad antigen coverage is critical.

Combination therapy with local radiofrequency ablation and systemic vaccine enhances antitumor immunity and mediates local and distal tumor regression

Purpose

Radiofrequency ablation (RFA) is a minimally invasive energy delivery technique increasingly used for focal therapy to eradicate localized disease. RFA-induced tumor-cell necrosis generates an immunogenic source of tumor antigens known to induce antitumor immune responses. However, RFA-induced antitumor immunity is insufficient to control metastatic progression. We sought to characterize (a) the role of RFA dose on immunogenic modulation of tumor and generation of immune responses and (b) the potential synergy between vaccine immunotherapy and RFA aimed at local tumor control and decreased systemic progression.

Experimental Design

Murine colon carcinoma cells expressing the tumor-associated (TAA) carcinoembryonic antigen (CEA) (MC38-CEA⁺) were studied to examine the effect of sublethal hyperthermia in vitro on the cells’ phenotype and sensitivity to CTL-mediated killing. The effect of RFA dose was investigated in vivo impacting (a) the phenotype and growth of MC38-CEA⁺ tumors and (b) the induction of tumor-specific immune responses. Finally, the molecular signature was evaluated as well as the potential synergy between RFA and poxviral vaccines expressing CEA and a TRIad of COstimulatory Molecules (CEA/TRICOM).

Results

In vitro, sublethal hyperthermia of MC38-CEA⁺ cells (a) increased cell-surface expression of CEA, Fas, and MHC class I molecules and (b) rendered tumor cells more susceptible to CTL-mediated lysis. In vivo, RFA induced (a) immunogenic modulation on the surface of tumor cells and (b) increased T-cell responses to CEA and additional TAAs. Combination therapy with RFA and vaccine in CEA-transgenic mice induced a synergistic increase in CD4⁺ T-cell immune responses to CEA and eradicated both primary CEA⁺ and distal CEA^– s.c. tumors. Sequential administration of low-dose and high-dose RFA with vaccine decreased tumor recurrence compared to RFA alone. These studies suggest a potential clinical benefit in combining RFA with vaccine in cancer patients, and augment support for this novel translational paradigm.

Phagocytes mediate targeting of iron oxide nanoparticles to tumors for cancer therapy

Nanotechnology has great potential to produce novel therapeutic strategies that target malignant cells through the ability of nanoparticles to get access to and be ingested by living cells. However its specificity for accumulation in tumors, which is the key factor that determines its efficacy, has always been a challenge. Here we tested a novel strategy to target and treat ovarian cancer, a representative peritoneal cancer, using iron oxide nanoparticles (IONPs) and an alternating magnetic field (AMF). Peritoneal tumors in general are directly accessible to nanoparticles administered intraperitoneally (IP), as opposed to the more commonly attempted intravenous (IV) administration. In addition, tumor-associated immunosuppressive phagocytes, a predominant cell population in the tumor microenvironment of almost all solid tumors, and cells that are critical for tumor progression, are constantly recruited to the tumor, and therefore could possibly function to bring nanoparticles to tumors. Here we demonstrate that tumor-associated peritoneal phagocytes ingest and carry IONPs specifically to tumors and that these specifically delivered nanoparticles can damage tumor cells after IONP-mediated hyperthermia generated by AMF. This illustrates therapeutic possibilities of intraperitoneal (IP) injection of nanoparticles and subsequent ingestion by tumor-associated phagocytes, to directly impact tumors or stimulate antitumor immune responses. This approach could use IONPs combined with AMF as done here, or other nanoparticles with cytotoxic potential. Overall, the data presented here support IP injection of nanoparticles to utilize peritoneal phagocytes as a delivery vehicle in association with IONP-mediated hyperthermia as therapeutic strategies for ovarian and other peritoneal cancers.

Human hsp70 and HPV16 oE7 fusion protein vaccine induces an effective antitumor efficacy

The persistent infection by human papilloma virus (HPV) is considered to be the major risk factor of cervical cancer, which is one of the most common cancers in women worldwide. Millions of women are currently infected with high-risk HPV. Thus, it is urgent to develop therapeutic vaccines to eliminate established infection or HPV-related diseases. In the present study, we constructed a very promising therapeutic HPV16 protein vaccine of optimized E7 (oE7)/huhsp70 using human hsp70 linked to HPV16 oE7. Our results demonstrated that vaccination with the oE7/huhsp70 protein vaccine induced a very strong E7-specific CD8(+) T cell immune response and resulted in a significant therapeutic effect against E7-expressing tumor cells. Our study verifies that huhsp70 is an effective immune adjuvant in the development of tumor therapeutic protein vaccines, and emphasizes that homologous huhsp70 is a promising tool in future human clinical applications.

The immunosuppressive activity of heat shock protein 70

Heat shock protein 70 (HSP70) has previously been described as a potent antitumour vaccine. The mechanism relied on the ability of tumour derived HSP70 to associate with antigenic peptides, which, when cross presented, elicited a T cell mediated antitumour response. Subsequently, HSP70 was incorrectly described as a potent adjuvant of innate immunity, and although mistakes in the experimental approaches were exposed and associated with endotoxin contamination in the recombinant HSP70 specimen, questions still remain regarding this matter. Here we review only publications that have cautiously addressed the endotoxin contamination problem in HSP70 in order to reveal the real immunological function of the protein. Accordingly, “endotoxin free” HSP70 stimulates macrophages and delivers antigenic peptides to APCs, which effectively prime T cells mediating an antitumour reaction. Conversely, HSP70 has potent anti-inflammatory functions as follows: regulating T cell responses, reducing stimulatory capacity of DCs, and inducing development of immunosuppressive regulatory T cells. These activities were further associated with the immune evasive mechanism of tumours and implicated in the modulation of immune reactivity in autoimmune diseases and transplant-related clinical conditions. Consequently, the role of HSP70 in immune regulation is newly emerging and contrary to what was previously anticipated.

CD91-Dependent Modulation of Immune Responses by Heat Shock Proteins: A Role in Autoimmunity

Heat shock proteins (HSPs) have been known for decades for their ability to protect cells under stressful conditions. In the 1980s a new role was ascribed for several HSPs given their ability to elicit specific immune responses in the setting of cancer and infectious disease. These immune responses have primarily been harnessed for the immunotherapy of cancer in the clinical setting. However, because of the ability of HSPs to prime diverse immune responses, they have also been used for modulation of immune responses during autoimmunity. The apparent dichotomy of immune responses elicited by HSPs is discussed here on a molecular and cellular level. The potential clinical application of HSP-mediated immune responses for therapy of autoimmune diseases is reviewed.

A new purification method for enhancing the immunogenicity of heat shock protein 70-peptide complexes

When purified from a tumor, certain heat shock protein 70 (HSP70)-peptide complexes (PCs) can function as effective vaccines against the tumor from which the complexes were isolated. The immunogenic mechanisms of HSP70 preparations imply that tumor-derived HSP70-PCs exhibit antigens associated with antigen-presenting cells such as dendritic cells (DCs), inducing antigen-specific cytotoxic CD8⁺ T cells. However, some important membrane-resident tumor-associated peptides, such as the HER-2/neu (c-erbB2) oncogenic protein, cannot be purified from HSP70 by traditional methods. In the present study, a new approach for the purification of HSP70-PCs from HER-2-overexpressing breast cancer cells was established. The detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) was used to obtain more effectual tumor peptides. The new purified product was named HSP70-HER-2-PC, and its immunological activities were determined. Traditionally purified HSP70-PCs (without CHAPS) and recombinant human HSP70-HER-2 protein complexes (recombined in vitro) were used as controls. These three HSP70-associated tumor antigenic complex pulsed dendritic cells (DCs) were used to stimulate an antitumor response. The mature DCs pulsed with HSP70-HER-2-PCs stimulated autologous T cells to secrete higher levels of type I cytokine compared to the two control groups. Moreover, DCs pulsed with HSP70-HER-2-PCs induced the most specific CD8⁺ T cells that specifically killed the same tumor cells. These findings provide a basis for new approaches in enhancing HSP70-based immunotherapy for HER-2-associated or other membrane antigenic peptide-related cancers.

Inhibition of HSP70: a challenging anti-cancer strategy

HSP70 is a chaperone that accumulates in the cells after many different stresses promoting cell survival in response to the adverse conditions. In contrast to normal cells, most cancer cells abundantly express HSP70 at the basal level to resist to various insults at different stages of tumorigenesis and during anti-cancer treatment. This cancer cells addiction for HSP70 is the rational for its targeting in cancer therapy. Much effort has been dedicated in the last years for the active search of HSP70 inhibitors. Additionally, the recent clinical trials on highly promising inhibitors of another stress protein, HSP90, showed compensatory increase in HSP70 levels and raised the question of necessity to combine HSP90 inhibitors with simultaneous inhibition of HSP70. Here we analyzed the recent advancement in creation of novel HSP70 inhibitors and different strategies for their use in anti-cancer therapy.

Trauma equals danger--damage control by the immune system

Traumatic injuries induce a complex host response that disrupts immune system homeostasis and predisposes patients to opportunistic infections and inflammatory complications. The response to injuries varies considerably by type and severity, as well as by individual variables, such as age, sex, and genetics. These variables make studying the impact of trauma on the immune system challenging. Nevertheless, advances have been made in understanding how injuries influence immune system function as well as the immune cells and pathways involved in regulating the response to injuries. This review provides an overview of current knowledge about how traumatic injuries affect immune system phenotype and function. We discuss the current ideas that traumatic injuries induce a unique type of a response that may be triggered by a combination of endogenous danger signals, including alarmins, DAMPs, self-antigens, and cytokines. Additionally, we review and propose strategies for redirecting injury responses to help restore immune system homeostasis.

The lid domain of Caenorhabditis elegans Hsc70 influences ATP turnover, cofactor binding and protein folding activity

Hsc70 is a conserved ATP-dependent molecular chaperone, which utilizes the energy of ATP hydrolysis to alter the folding state of its client proteins. In contrast to the Hsc70 systems of bacteria, yeast and humans, the Hsc70 system of C. elegans (CeHsc70) has not been studied to date.

We find that CeHsc70 is characterized by a high ATP turnover rate and limited by post-hydrolysis nucleotide exchange. This rate-limiting step is defined by the helical lid domain at the C-terminus. A certain truncation in this domain (CeHsc70-Δ545) reduces the turnover rate and renders the hydrolysis step rate-limiting. The helical lid domain also affects cofactor affinities as the lidless mutant CeHsc70-Δ512 binds more strongly to DNJ-13, forming large protein complexes in the presence of ATP. Despite preserving the ability to hydrolyze ATP and interact with its cofactors DNJ-13 and BAG-1, the truncation of the helical lid domain leads to the loss of all protein folding activity, highlighting the requirement of this domain for the functionality of the nematode's Hsc70 protein.

Heat shock proteins and cancer vaccines: developments in the past decade and chaperoning in the decade to come

Molecular chaperone-peptide complexes extracted from tumors (heat shock protein [HSP] vaccines) have been intensively studied in the preceding two decades, proving to be safe and effective in treating a number of malignant diseases. They offer personalized therapy and target a cross-section of antigens expressed in patients' tumors. Future advances may rely on understanding the molecular underpinnings of this approach to immunotherapy. One property common to HSP vaccines is the ability to stimulate antigen uptake by scavenger receptors on the antigen-presenting cell surface and trigger T-lymphocyte activation. HSPs can also induce signaling through Toll-Like receptors in a range of immune cells and this may mediate the effectiveness of vaccines.

Inducible heat shock protein 70 reduces T cell responses and stimulatory capacity of monocyte-derived dendritic cells

Heat shock protein 70 (Hsp70) has gained a lot of attention in the past decade due to its potential immunoregulatory functions. Some of the described proinflammatory functions of Hsp70 became controversial as they were based on recombinant Hsp70 proteins specimens, which were later shown to be endotoxin-contaminated. In this study we used low endotoxin inducible Hsp70 (also known as Hsp72, HSPA1A), and we observed that after a 24-h incubation of monocyte-derived immature dendritic cells (mo-iDCs) with 20 μg/ml of low endotoxin Hsp70, their ability to stimulate allogenic T cells was reduced. Interestingly, low endotoxin Hsp70 also significantly reduced T cell responses when they were simulated with either IL-2 or phytohemagglutinin, therefore showing that Hsp70 could alter T cell responses independently from its effect on mo-iDCs. We also reported a greater response of Hsp70 treatment when activated versus nonactivated T cells were used. This effect of Hsp70 was similar for all tested populations of T cells that included CD3(+), CD4(+), or CD8(+). Taken together, our observations strongly suggest that Hsp70 might dampen, rather than provoke, T cell-mediated inflammatory reactions in many clinical conditions where up-regulation of Hsp70 is observed.