Intracellular Heat Shock Protein Research Articles

Enhanced Intracellular Heat Shock Protein 70 Expression of Leukocytes and Serum Interleukins Release: Comparison of On‐pump and Off‐pump Coronary Artery Surgery

Coronary artery bypass grafting (CABG) employing cardiopulmonary bypass (CPB; "on-pump" technique) is known to induce a systemic inflammatory response and heat-shock protein 70 kDa (HSP70) expression. The objective of the present study was to investigate the perioperative intracellular HSP70 expression of leukocytes and serum interleukin (IL) release in CABG conducted with both on-pump and off-pump techniques. Thirty-seven patients referred for elective CABG were enrolled in this study. These patients were categorized into the following three groups: on-pump cardioplegic arrest (n = 12); on-pump beating heart (n = 13); and off-pump (n = 12). Blood samples were collected at four time points during the perioperative period. Enzyme-linked immunosorbent assay (ELISA) was used to determine the serum level of IL-8, IL-10, IL-12, and HSP70. Flow cytometric analysis of intracellular HSP70 was performed in populations of lymphocytes, monocytes, and granulocytes. The clinical outcomes were comparable among the three groups. Elevated serum IL-8, IL-10, IL-12 were found in all three groups during the perioperative period. Serum HSP70 was elevated in all three groups and was significantly lower in the off-pump group than in the on-pump cardioplegic arrest and on-pump beating-heart groups. Heat shock protein-70 expression was found in leukocytes and showed a faster response in monocytes and granulocytes than in lymphocytes. The inflammatory response in the off-pump group was less than in either of the on-pump groups. During the perioperative period, activation of inflammatory response was associated with enhanced expression of HSP70 within leukocytes in CABG patients.

Idesolide, an Isolate of Idesia polycarpa, Inhibits Apoptosis through Induction of Intracellular Heat Shock Protein 70 in C2C12 Muscle Cells

Muscle disorders, such as muscular dystrophy, are associated with an increase in oxidative stress. Proposed treatments for muscular dystrophy, some in clinical trials, include gene therapy and muscle cell transplantation. In this study, we investigated the effects of idesolide, isolated from the fruits of Idesia polycarpa, on changes that occur in muscle disuse atrophy. We noted protective effects on oxidative stress response and HSP70 regulation. Pre-treatment with idesolide for 24 h maintained cell viability and decreased apoptosis in H(2)O(2)-treated C(2)C(12) muscle cells. The idesolide pretreatment also increased intracellular HSP70 protein. Our results suggest that idesolide inhibits cell death through induction of HSP70 in C(2)C(12) muscle cells. This work is the first to report that idesolide can regulate the decrease in HSP70 that occurs during skeletal muscle atrophy.

Extracellular Heat Shock Protein 60, Cardiac Myocytes, and Apoptosis

Previously, we have found that changes in the location of intracellular heat shock protein (HSP)60 are associated with apoptosis. HSP60 has been reported to be a ligand of toll-like receptor (TLR)-4. We hypothesized that extracellular HSP60 (exHSP60) would mediate apoptosis via TLR4. Adult rat cardiac myocytes were treated with HSP60, either recombinant human or with HSP60 purified from the media of injured rat cardiac myocytes. ExHSP60 induced apoptosis in cardiac myocytes, as detected by increased caspase 3 activity and increased DNA fragmentation. Apoptosis could be reduced by blocking antibodies to TLR4 and by nuclear factor kappaB binding decoys, but not completely inhibited, even though similar treatment blocked lipopolysaccharide-induced apoptosis. Three distinct controls showed no evidence for involvement of a ligand other than exHSP60 in the mediation of apoptosis. This is the first report of HSP60-induced apoptosis via the TLRs. HSP60-mediated activation of TLR4 may be a mechanism of myocyte loss in heart failure, where HSP60 has been detected in the plasma.

Proteomic analysis reveals significant elevation of heat shock protein 70 in patients with chronic heart failure due to arrhythmogenic right ventricular cardiomyopathy

As proteins are the ultimate biological determinants of phenotype of disease, we screened altered proteins associated with heart failure due to arrhythmogenic right ventricular cardiomyopathy (ARVC) to identify biomarkers potential for rapid diagnosis of heart failure. By 2-dimensional gel electrophoresis and mass spectrometry, we identified five commonly altered proteins with more than 1.5 fold changes in eight ARVC failing hearts using eight non-failing hearts as reference. Noticeably, one of the altered proteins, heat shock protein 70 (HSP70), was increased by 1.64 fold in ARVC failing hearts compared with non-failing hearts. The increase of cardiac HSP70 was further validated by Western blot, immunochemistry, and enzyme-linked immunosorbent assay (ELISA) in failing hearts due to not only ARVC, but also dilated (DCM, n = 18) and ischemic cardiomyopathy (ICM, n = 8). Serum HSP70 was also observed to be significantly increased in heart failure patients derived from the three forms of cardiomyopathies. In addition, we observed hypoxia/serum depletion stimulation induced significantly elevation of intracellular and extracellular HSP70 in cultured neonatal rat cardiomyocytes. For the first time to our knowledge, we revealed and clearly demonstrated significant up-regulation of cardiac and serum HSP70 in ARVC heart failure patients. Our results indicate that elevated HSP70 is the common feature of heart failure due to ARVC, DCM, and ICM, which suggests that HSP70 may be used as a biomarker for the presence of heart failure due to cardiomyopathies of different etiologies and may hold diagnostic/prognostic potential in clinical practice.

Effect of Delta-Sleep-Inducing Peptide on Expression of Heat Shock Protein 70 kDa in K562 Cells

For evaluation of the stress-protective influence of delta-sleep inducing peptide we studied its effects on the system of heat-shock proteins in immune cells using the method of flow cytometry. The peptide affected the expression of heat-shock protein 70 kDa in cultured human myeloleukemia K562 cells. Delta-sleep-inducing peptide reduces accumulation of intracellular heat shock proteins 70 kDa in cells cultured under conditions of high density.

Activation of natural killer cells by heat shock protein 70

Intracellular heat shock proteins (HSP) function as molecular chaperones, they support folding and transport mechanisms of other proteins under physiological conditions and following physical or chemical stress. More recently, extracellular localized HSP have been found to play key roles in the induction of a cellular immune response. Either they act as carrier molecules for immunogenic peptides that are presented on Antigen Presenting Cells (APC) to cytotoxic T-cells or they themselves act as activatory molecules for the innate immune system. Binding of uncomplexed HSP to HSP-receptors on APC has been found to induce the secretion of inflammatory cytokines. Furthermore, an unusual tumor-selective membrane-localization of non-conserved regions of the 72 000 Da HSP (Hsp70) has been found to act as a recognition structure for natural killer (NK) cells. In this review the interaction of NK cells with Hsp70 or peptides derived thereof will be eluciated in more detail.

THE ROLE OF ENDOGENOUSLY PRODUCED EXTRACELLULAR HSP72 IN MONONUCLEAR CELL REPROGRAMMING

Intracellular heat shock protein 72 (Hsp72) is known to serve a broad cytoprotective role. Recent data indicate that stressed cells can release Hsp72 into the extracellular compartment, although the biological function of extracellular Hsp72 remains to be fully elucidated. Because extracellular Hsp72 has been demonstrated to interact with Toll-like receptor 4, we hypothesized that endogenously produced and released Hsp72 would reprogram the mononuclear cell responses to LPS. THP-1 cells treated with LPS were used as a model for nuclear factor (NF)-kappaB activation. Heat shock conditions consisted of incubation at 43 degrees C for 1 h. Control cells were incubated at 37 degrees C. Twenty four hours after incubation, heat shock conditioned media (HSCM) and control media (CM) were centrifuged, and the respective cells were discarded. A separate group of naive THP-1 cells were then incubated with either HSCM or CM for 18 h and then stimulated with LPS (1 mug/mL). Heat shock significantly increased Hsp72 in HSCM compared with CM. In THP-1 cells transfected with an NF-kappaB luciferase reporter plasmid, the addition of HSCM attenuated subsequent LPS-mediated luciferase activity compared with cells incubated in CM. The addition of HSCM also attenuated LPS-mediated NF-kappaB-DNA binding and IkappaBalpha degradation. Heat shock protein 72-mediated inhibition of NF-kappaB activation was further corroborated by a significant decrease in TNF-alpha production. When HSCM and CM were subjected to Hsp72 depletion via adenosine triphosphate-agarose binding, LPS-mediated activation of NF-kappaB was partially restored, suggesting that Hsp72 is partially responsible for cellular reprogramming in response to HSCM. These data demonstrate that endogenously produced and released extracellular Hsp72 has the ability to reprogram the in vitro response to endotoxin in cultured human mononuclear cells.

Heat shock protein 72 : release and biological significance during exercise

The cumulative stressors of exercise manifest themselves at a cellular level by threatening the protein homeostasis of the cell. In these conditions, Heat Shock Proteins (HSP) are synthesised to chaperone mis-folded and denatured proteins. As such, the intracellular HSP response is thought to aid cell survival in the face of otherwise lethal cellular stress. Recently, the inducible isoform of the 70 Kda heat shock protein family, Hsp72 has been detected in the extracellular environment. Furthermore, the release of this protein into the circulation has been shown to occur in response to a range of exercise bouts. The present review summarises the current research on the exercise Hsp72 response, the possible mediators and mechanisms of extracellular (e)Hsp72 release, and the possible biological significance of this systemic response. In particular, the possible role of eHsp72 in the modulation of immunity during exercise is discussed.

Effects of active and passive hyperthermia on heat shock protein 70 (HSP70)

The purpose of this study was to delineate the effects of hyperthermia and physical exercise on the heat shock protein 70 (HSP70) response in circulating peripheral blood mononuclear cells (PBMCs). Six healthy, young (age: 24 +/- 3 yrs), moderately trained males (VO(2max): 48.9 +/- 2.7 ml x kg x min(-1)) undertook two experimental trials in a randomised fashion in which the core temperature (T (c)) was increased and then maintained at 39 degrees C during a 90 min bout by either active (AH) or passive (PH) means. AH involved subjects cycling at 90% of their lactate threshold in attire designed to impede heat loss mechanisms. In the PH trial, subjects were immersed up to the neck in a hot bath (40.2 +/- 0.4 degrees C), once the critical T (c) was achieved, intermittent cycling and water immersions were prescribed for the AH and PH conditions, respectively, to maintain the T (c) at 39 degrees C. HSP70 was measured intracellularly pre, post and 4 h after trials, from circulating PBMCs using an ELISA technique. T (c) reached 39 degrees C quicker in PH than during AH trials (PH: 21 +/- 4 min vs. AH: 39 +/- 6 min; P < 0.01), thereafter T (c) was maintained around 39 degrees C (PH: 39.1 +/- 0.2 degrees C; AH: 38.8 +/- 0.3 degrees C; P > 0.05). AH induced a marked leukocytosis in all sub-sets (P < 0.05). PH generated significant monocytosis and granulocytosis (P < 0.05), without changes in lymphocyte counts (P > 0.05). There were no significant increases in intracellular HSP70 at 0 h (AH: Delta - 21.1 +/- 44.8; PH: Delta + 12.5 +/- 32.4 ng/mg TP/10(3)/microl PBMCs; P > 0.05) and 4 h (AH: Delta - 30.0 +/- 40.1; PH: Delta + 36.3 +/- 70.4 ng/mg TP/10(3)/microl PBMCs; P > 0.05) post active and passive heating. Peak HSP70 expressed as a fold-change from rest was also not increased by AH (1.1 +/- 0.9; P > 0.05) or PH (3.2 +/- 4.8; P > 0.05). There were no significant differences between the AH and PH trials at any time-point, and the HSP70 response appeared to be individual specific. These results did not allow us to delineate the effects of hyperthermia and other exercise associated stressors on the heat shock response and therefore further work is warranted.

Effect of heat acclimation on heat shock protein 72 and interleukin-10 in humans

Heat acclimation (HA) results in whole body adaptations that increase heat tolerance, and in addition, HA may also result in protective cellular adaptations. We hypothesized that, after HA, basal intracellular heat shock protein (HSP) 72 and extracellular IL-10 levels would increase, while extracellular HSP72 levels decrease. Ten male and two female subjects completed a 10-day exercise/HA protocol (100-min exercise bout at 56% of maximum O(2) uptake in a 42.5 degrees C DB, 27.9% RH environment); subjects exhibited classic adaptations that accompany HA. Peripheral blood mononuclear cells (PBMCs) were isolated before and after each acclimation session on days 1, 6, and 10; plasma and serum were collected before and after exercise on the 1st and 10th day of HA. SDS-PAGE was used to determine PBMC HSP72 levels during HA, and ELISA was used to measure plasma IL-10 and serum HSP72 concentrations. The increase in PBMC HSP72 from pre- to postexercise on the 1st day of HA was not significant (mean +/- SD, 1.0 +/- 0 vs. 1.6 +/- 0.6 density units). Preexercise HSP72 levels on day 1 were significantly lower compared with the pre- and postexercise samples on days 6 and 10 (mean +/- SD, day 6: 2.1 +/- 1.0 and 2.2 +/- 1.0, day 10: 2.0 +/- 1.3 and 2.2 +/- 1.0 density units, respectively, P < 0.05). There were no differences in plasma IL-10 and serum HSP72 postexercise or after 10 days of HA. The sustained elevation of HSP72 from days 6 to 10 may be evidence of a cellular adaptation to HA that contributes to improved heat tolerance and reduced heat illness risk.

An imbalance in antioxidant enzymes and stress proteins in childhood asthma

Objectives: The study was undertaken to examine antioxidant status and level of the major intracellular heat shock proteins (Hsps) in healthy children and children with mild and moderate asthma. Design and methods: Native gel assays were performed to estimate activities of copper/zinc (CuZn) and manganese (Mn) superoxide dismutase (SOD), and catalase (CAT) in peripheral blood mononuclear cells (PBMC) of healthy and asthmatic children. Hsp70 and Hsp90 protein levels in PBMCs were assessed by Western blot analysis. Results: Moderate asthmatics displayed higher CuZnSOD/CAT activity ratio compared to healthy children, and increased Hsp90 level compared to mild asthmatics and healthy children. Conclusions: With regard to the imbalance in the antioxidant enzyme activities children with moderate asthma differ from healthy children, while an increased Hsp90 expression could be associated with the disease severity, as well.

Sensitivity of Flow Cytometric Assay for Measurement of Human Intracellular Heat Shock Protein 27

Increased expression of heat shock protein 27 (hsp27) is related to enhanced resistance of breast tumor cells to cytotoxic drugs and radiation therapy. Therefore, development of a rapid and sensitive method for detection of hsp27 may be useful for correlating tumor cell expression of hsp27 to breast cancer patients' clinical outcome. We have simultaneously assessed hsp27 levels in three different human cell lines (MCF‐7, MDA‐MB‐231, and Jurkat) by both Western blotting and flow cytometry. MCF‐7 hsp27 levels were consistently detected at higher levels, while MDA‐MB‐231 hsp27 levels were detected at very low levels when immunoblotting was performed. Hsp27 was not detected in Jurkat cells by immunoblotting. In contrast, hsp27 levels were detected by flow cytometry in all the cell lines, indicating a better sensitivity of this method. Although hsp27 was expressed in almost equal percentage of MCF‐7 (93±3.4%), MDA‐MB‐231 (97±1%), and Jurkat (95.5±1.9) cells, the fluorescence intensity of intracellular hsp27 protein was significantly lower in MDA‐MB‐231 and Jurkat cells as compared to MCF‐7 cells. The flow cytometry data further demonstrated that reduced hsp27 expression in both MDA‐MB‐231 and Jurkat cells was not due to a lack of hsp27 expression in a subset of cells, but rather due to reduced expression of hsp27 in all individual cells.

Diverse regulatory activity of human heat shock proteins 60 and 70 on endotoxin-induced inflammation

Tissue injury is often associated with bacterial infection. Intracellular heat shock proteins (HSPs) are released from damaged tissue, come in contact with cells of the immune system, and might affect the immune response against bacteria. In the present study, we investigated the capacity of highly purified human HSP60 and HSP70 to modulate the response of human peripheral blood-derived mononuclear cells (PBMC) to lipopolysaccharide (LPS). HSP70 but not HSP60 decreased the LPS-induced secretion of TNF-α when added simultaneously with LPS. In contrast, HSP60 and HSP70 primed PBMC for enhanced secretion of TNF-α when added 24h prior to the stimulation with LPS. Neither HSP60 nor HSP70 alone induced the release of TNF-α. The capacity of LPS to bind to monocytes was not affected by HSPs, but HSP70 increased the expression of Toll-like receptor 4. Thus, HSP60 and HSP70 released upon tissue damage might play a role in the regulation of bacteria-induced inflammation.

Heat Shock Proteins - Two Sides of a Coin

Heat Shock Proteins (HSPs) are intracellular molecular chaperones, which preserve protein folding and protect cells from injury. Intracellularly, their normal location, HSPs are protective. HSPs can also be found in the extracellular compartment, either after necrotic cell death or independent of cell death. The physiologic function of exogenous HSPs remains elusive. However, extracellular as well as membrane- localized HSPs have been implicated in the pathogenesis of a number of diseases including type I diabetes, Crohns, atherosclerosis and juvenile chronic arthritis. It is thought that HSPs can provoke an immune response either by directly activating the innate immune system, or through the adaptive immune response leading to production of antibodies, possibly as a result of prior exposure to the bacterial HSPs, which have great sequence similarity. Extracellular HSPs can activate Toll-like receptors (TLR), and induce the production of cytokines; but, intracellular HSPs can downregulate cytokine production and mediate myocardial protection. Production of nitric oxide may trigger HSPs, ameliorating cardiotoxic effects of cytokines. Apoptosis has come into focus as a contributing factor for ischemia/reperfusion injury, and conflicting data exist about a potentially beneficial or deleterious role of HSPs. Although novel therapeutic strategies include elevation of specific HSPs, the interplay of HSPs in the clinical setting is poorly understood.

Heat-shock proteins: new keys to the development of cytoprotective therapies

As molecular chaperones, heat-shock proteins (HSPs) function to limit protein aggregation, facilitate protein refolding and chaperone other proteins. Under conditions of cellular stress, intracellular HSP levels increase in order to provide cellular protection and maintain homeostasis. Evidence exists that the HSP family may be secreted into the circulation via lipid raft-mediated, granule-mediated or exosome-mediated exocytosis in haematopoietic and tumour cells. Extracellular HSPs exert immunomodulatory activities and play an important role in innate immune activation against pathogen infection. Membrane-bound Hsp70 in tumour cells or released chaperone-tumour associated antigen complex represent a target structure for the cytolytic attack by natural killer cells or T lymphocytes. Cellular stresses induce stress granule formation to evade detrimental cellular effects, mediating preconditioning phenotype. Therefore, induction of cellular stress tolerance by preconditioning (e.g., heat shock) might be potential therapeutic targets.

Intracellular and extracellular functions of heat shock proteins: repercussions in cancer therapy

Stress or heat shock proteins (HSPs) are the most conserved proteins present in both prokaryotes and eukaryotes. Their expression is induced in response to a wide variety of physiological and environmental insults. These proteins play an essential role as molecular chaperones by assisting the correct folding of nascent and stress-accumulated misfolded proteins, and preventing their aggregation. HSPs have a dual function depending on their intracellular or extracellular location. Intracellular HSPs have a protective function. They allow the cells to survive lethal conditions. Various mechanisms have been proposed to account for the cytoprotective functions of HSPs. Several HSPs have also been demonstrated to directly interact with various components of the tightly regulated programmed cell death machinery, upstream and downstream of the mitochondrial events. On the other hand, extracellular located or membrane-bound HSPs mediate immunological functions. They can elicit an immune response modulated either by the adaptive or innate immune system. This review will focus on HSP27, HSP70, and HSP90. We will discuss the dual role of these HSPs, protective vs. immunogenic properties, making a special emphasis in their utility as targets in cancer therapy.

Initiation of the Immune Response by Extracellular Hsp72: Chaperokine Activity of Hsp72

Heat shock proteins exert their beneficial effects via basically two modes of action depending on their relative location within the host. Intracellular heat shock proteins found within cells serve a cytoprotective role by chaperoning naïve, misfolded and/or denatured proteins in response to stressful stimuli by a process known as the stress response. However, stressful stimuli also induce the release of intracellular heat shock proteins into the extracellular milieu and circulation. The extracellular heat shock protein proteins serve a cytostimulatory role by initiating immune responses designed to fend off microbial infection and destroy neoplastic transformed cells. This review will briefly cover recent advances into elucidating the mechanism(s) by which stress induces the release of heat shock proteins into the circulation, how it initiates immune responses and suggest the possible biological significance of circulating Hsp to the host.

Sexual dimorphism of the intracellular heat shock protein 72 response

The majority of previous work examining stress responses has been done in males. Recently, it has become clear that the impact of stressor exposure is modulated by sex. One stress response that may be affected by sex is the induction of intracellular heat shock protein (HSP) 72, which is a stress- responsive molecular chaperone that refolds denatured proteins and promotes cellular survival. The following study compared HSP72 in males and females and also examined whether the estrous cycle altered HSP72 induction in females. We hypothesized that females compared with males would have a constrained HSP72 response after an acute stressor and that the stress-induced HSP72 response in females would fluctuate with the estrous cycle. Male and female F344 rats were either left in their home cage or exposed to acute tail-shock stress (8-10/group). Immediately following stressor, trunk blood was collected and tissues were flash frozen. Vaginal smear and estrogen enzyme immunoassay were used to categorize the phase of estrous. Results show that female rats had a greater corticosterone response than males, that both males and females exhibit a stress-induced release of progesterone, and that males and females had equal levels of stress-induced circulating norepinephrine. Sexual dimorphism of the HSP72 (ELISA) response existed in pituitary gland, mesenteric lymph nodes, and liver such that female rats had an attenuated HSP72 response compared with males after stress. The adrenal glands, spleen, and heart did not exhibit sexual dimorphism of the HSP72 response. The estrous cycle did not have a significant effect on basal or stress-induced HSP72 in females.

Peripheral leukocyte response to oncological radiotherapy: Expression of heat shock proteins

Purpose:To study Heat Shock Proteins (HSP) expression in patients subjected to radiotherapy and their potential use as biomarkers for radiation tolerance. An evaluation is also made of whether irradiated volume is critical to the outcome of normal tissue injury using polymorphonuclear neutrophils as biosensors, and whether HSP antibodies (Ab) may be involved in post-radiotherapy disease.Material and methods:Twelve patients receiving the same total dose of radiotherapy, but in three different volumes, and four healthy volunteers used as controls were analysed. hsp27 and 70i mRNA were determined by Reverse Transcription-Polymerase Chain Reaction (RT-PCR) and Southern-blot, HSP by flow cytometry, and HSP-Ab by Enzyme-linked Immnoadsorbent Assay (ELISA). The clinical protocol included radiation related toxicity based on clinical and analytical scales.Results:Radiotherapy caused hsp downregulation, maximum in patients with the largest irradiated volumes, and a decrease in intracellular HSP content. Patients with greatest intraleukocyte HSP levels before treatment suffered more severe radiation morbidity. Patients with endocrine neoplasms presented the highest HSP-Ab titers.Conclusions:Radiotherapy downregulates hsp27 and 70i, which would enhance radiosensitivity. HSP content prior to treatment is suggested as a prognostic biomarker for radiation tolerance, with circulating leukocytes as biosensors. HSP-Ab may be biomarkers of tumor disease, but do not seem to be involved in the morbidity of acute post-radiotherapy disease, which is closely related to the volumes irradiated.

Message in a bottle: Role of the 70‐kDa heat shock protein family in anti‐tumor immunity

Extracellular heat shock protein 70 (HSP70) is a potent agent for tumor immunotherapy, which can break tolerance to tumor-associated antigens and cause specific tumor cell killing by cytotoxic CD8+ T cells. The pro-immune effects of extracellular HSP70 are, to some extent, extensions of its molecular properties as an intracellular stress protein. The HSP70 are characterized by massive inducibility after stress, preventing cell death by inhibiting aggregation of cell proteins and directly antagonizing multiple cell death pathways. HSP70 family members possess a domain in the C terminus that chaperones unfolded proteins and peptides, and a N-terminal ATPase domain that controls the opening and closing of the peptide binding domain. These properties not only enable intracellular HSP70 to inhibit tumor apoptosis, but also promote formation of stable complexes with cytoplasmic tumor antigens that can then escape intact from dying cells to interact with antigen-processing cells (APC) and stimulate anti-tumor immunity. HSP70 may be released from tumors undergoing therapy at high local extracellular concentrations, and send a danger signal to the host leading to APC activation. Extracellular HSP70 bind to high-affinity receptors on APC, leading to activation of maturation and re-presentation of the peptide antigen cargo of HSP70 by the APC. The ability of HSP70-peptide complexes (HSP70-PC) to break tolerance and cause tumor regression employs these dual properties as signaling ligand and antigen transporter. HSP70-PC thus coordinately activate innate immune responses and deliver antigens for re-presentation by MHC class I and II molecules on the APC cell surface, leading to specific anti-tumor immunity.