Combined BRAF, MEK, and heat-shock protein 90 inhibition in advanced BRAF V600-mutant melanoma.

BACKGROUND: Resistance to BRAF and MEK inhibitors in BRAF V600-mutant melanoma is common. Multiple resistance mechanisms involve heat-shock protein 90 (HSP90) clients, and a phase 1 study of vemurafenib with the HSP90 inhibitor XL888 in patients with advanced melanoma showed activity equivalent to that of BRAF and MEK inhibitors. METHODS: Vemurafenib (960 mg orally twice daily) and cobimetinib (60 mg orally once daily for 21 of 28 days) with escalating dose cohorts of XL888 (30, 45, 60, or 90 mg orally twice weekly) was investigated in a phase 1 trial of advanced melanoma, with a modified Ji dose-escalation design. RESULTS: Twenty-five patients were enrolled. After two dose-limiting toxicities (DLTs) (rash and acute kidney injury) in the first cohort, lower doses of vemurafenib (720 mg) and cobimetinib (40 mg) were investigated with the same XL888 doses. Three DLTs (rash) were observed in 12 patients in the XL888 60-mg cohort, and this was determined as the maximum tolerated dose. Objective responses were observed in 19 patients (76%), and the median progression-free survival was 7.6 months, with a 5-year progression-free survival rate of 20%. The median overall survival was 41.7 months, with a 5-year overall survival rate of 37%. Single-cell RNA sequencing was performed on baseline and on-treatment biopsies; treatment was associated with increased immune cell influx (CD4-positive and CD8-positive T cells) and decreased melanoma cells. CONCLUSIONS: Combined vemurafenib and cobimetinib plus XL888 had significant toxicity, requiring frequent dose reductions, which may have contributed to the relatively low progression-free survival despite a high tumor response rate. Given overlapping toxicities, caution must be used when combining HSP90 inhibitors with BRAF and MEK inhibitors.

Heat shock protein 90 inhibitors induce cell differentiation via the ubiquitin-dependent aurora kinase A degradation in a MPLW515L mouse model of primary myelofibrosis.

Primary myelofibrosis (PMF) is characterized by immature megakaryocytic hyperplasia, splenomegaly, extramedullary hematopoiesis and bone marrow fibrosis. Our preclinical study had demonstrated that aurora kinase A (AURKA) inhibitor MLN8237 reduced the mutation burden of PMF by inducing differentiation of immature megakaryocytes. However, it only slightly alleviated splenomegaly, reduced tissue fibrosis, and normalized megakaryocytes in PMF patients of the preliminary clinical study. So enhancing therapeutic efficacy of PMF is needed. In this study, we found that AURKA directly interacted with heat shock protein 90 (HSP90) and HSP90 inhibitors promoted the ubiquitin-dependent AURKA degradation. We demonstrated that HSP90 inhibitors 17-allylamino-17-demethoxygeldanamycin (17-AAG) and 17-dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG), normalized peripheral blood counts, improved splenomegaly, attenuated extramedullary hematopoiesis, decreased tissue fibrosis and reduced mutant burden in a MPLW515L mouse model of PMF. Importantly, both 17-AAG and 17-DMAG treatment at effective doses in vivo did not influence on hematopoiesis in healthy mice. Collectively, the study demonstrates that HSP90 inhibitors induce cell differentiation via the ubiquitin-dependent AURKA and also are safe and effective for the treatment of a MPLW515L mouse model of PMF, which may provide a new strategy for PMF therapy. Further, we demonstrate that combined therapy shows superior activity in acute megakaryocytic leukemia mouse model than single therapy.

Harnessing mitochondrial metabolism and drug resistance in non-small cell lung cancer and beyond by blocking heat-shock proteins.

Lung cancer is the leading cause of cancer-related deaths worldwide, with non-small cell lung cancer (NSCLC) being the predominant histological subtype. Despite the emergence of targeted and immune-based therapies that have considerably improved the clinical outcomes of selected patients, the overall NSCLC survival rate remains poor. NSCLC patients experience clinical relapse mainly because of chemoresistance. One promising therapeutic approach is targeting specific molecular vulnerabilities that are associated with the metabolic reprogramming of cancer cells. This strategy relies on evidence that cancer cells rewire their metabolism to sustain their uncontrolled growth as well as invasive and metastatic properties, promoting adaptive resistance to chemo-radiotherapy. A critical component of this malignant transformation is the increased dependency on high levels of heat shock proteins (HSPs), which support the elevated protein folding demand and quality control of misfolded oncoproteins. Here, we provide an overview of the literature on metabolism reprogramming, deregulation of mitochondrion and on the role of HSPs in promoting malignancy in lung and other cancer types. A particular focus is dedicated to the role of mitochondrial HSP60 (HSPD1) in NSCLC metabolism and drug resistance for the potential development of new resistance-defying anti-HSP drugs.

Inflammatory Bowel Diseases: An Updated Overview on the Heat Shock Protein Involvement.

Inflammatory bowel diseases (IBDs) represent chronic idiopathic disorders, including Crohn's disease (CD) and ulcerative colitis (UC), in which one of the trigger factors is represented by aberrant immune interactions between the intestinal epithelium and the intestinal microbiota. The involvement of heat shock proteins (HSPs) as etiological and pathogenetic factors is becoming of increasing interest. HSPs were found to be differentially expressed in the intestinal tissues and sera of patients with CD and UC. It has been shown that HSPs can play a dual role in the disease, depending on the stage of progression. They can support the inflammatory and fibrosis process, but they can also act as protective factors during disease progression or before the onset of one of the worst complications of IBD, colorectal cancer. Furthermore, HSPs are able to mediate the interaction between the intestinal microbiota and intestinal epithelial cells. In this work, we discuss the involvement of HSPs in IBD considering their genetic, epigenetic, immune and molecular roles, referring to the most recent works present in the literature. With our review, we want to shed light on the importance of further exploring the role of HSPs, or even better, the role of the molecular chaperone system (CS), in IBD: various molecules of the CS including HSPs may have diagnostic, prognostic and therapeutic potential, promoting the creation of new drugs that could overcome the side-effects of the therapies currently used.

Cytokine-Induced Killer Cells in Combination with Heat Shock Protein 90 Inhibitors Functioning via the Fas/FasL Axis Provides Rationale for a Potential Clinical Benefit in Burkitt's lymphoma.

Constant efforts are being made to develop methods for improving cancer immunotherapy, including cytokine-induced killer (CIK) cell therapy. Numerous heat shock protein (HSP) 90 inhibitors have been assessed for antitumor efficacy in preclinical and clinical trials, highlighting their individual prospects for targeted cancer therapy. Therefore, we tested the compatibility of CIK cells with HSP90 inhibitors using Burkitt's lymphoma (BL) cells. Our analysis revealed that CIK cytotoxicity in BL cells was augmented in combination with independent HSP90 inhibitors 17-DMAG (17-dimethylaminoethylamino-17-demethoxygeldanamycin) and ganetespib. Interestingly, CIK cell cytotoxicity did not diminish after blocking with NKG2D (natural killer group 2, member D), which is a prerequisite for their activation. Subsequent analyses revealed that the increased expression of Fas on the surface of BL cells, which induces caspase 3/7-dependent apoptosis, may account for this effect. Thus, we provide evidence that CIK cells, either alone or in combination with HSP90 inhibitors, target BL cells via the Fas-FasL axis rather than the NKG2D pathway. In the context of clinical relevance, we also found that high expression of HSP90 family genes (HSP90AA1, HSP90AB1, and HSP90B1) was significantly associated with the reduced overall survival of BL patients. In addition to HSP90, genes belonging to the Hsp40, Hsp70, and Hsp110 families have also been found to be clinically significant for BL survival. Taken together, the combinatorial therapy of CIK cells with HSP90 inhibitors has the potential to provide clinical benefits to patients with BL.

Heat Shock Proteins as the Druggable Targets in Leishmaniasis: Promises and Perils.

Leishmania, the causative agent of leishmaniasis, is an intracellular pathogen that thrives in the insect gut and mammalian macrophages to complete its life cycle. Apart from temperature difference (26 to 37°C), it encounters several harsh conditions, including oxidative stress, inflammatory reactions, and low pH. Heat shock proteins (HSPs) play essential roles in cell survival by strategically reprogramming cellular processes and signaling pathways. HSPs assist cells in multiple functions, including differentiation, adaptation, virulence, and persistence in the host cell. Due to cyclical epidemiological patterns, limited chemotherapeutic options, drug resistance, and the absence of a vaccine, control of leishmaniasis remains a far-fetched dream. The essential roles of HSPs in parasitic differentiation and virulence and increased expression in drug-resistant strains highlight their importance in combating the disease. In this review, we highlighted the diverse physiological importance of HSPs present in Leishmania, emphasizing their significance in disease pathogenesis. Subsequently, we assessed the potential of HSPs as a chemotherapeutic target and underlined the challenges associated with it. Furthermore, we have summarized a few ongoing drug discovery initiatives that need to be explored further to develop clinically successful chemotherapeutic agents in the future.

Therapeutic perspectives of heat shock proteins and their protein-protein interactions in myocardial infarction.

Myocardial infarction (MI) is one of major causes of human death around the world. Heat shock proteins (HSPs) are a large family of conserved proteins, which can promote correct protein folding, maintain protein stability, and regulate cell metabolism, cellular homeostasis and other biological processes as molecular chaperones. Notable, HSPs are involved in MI-related pathophysiology, such as apoptosis, inflammatory response and oxidative stress. Here, we review recent studies and systematically summarize the role of HSPs in MI and myocardial ischemia/reperfusion injury (MIRI) and discuss the role of direct and indirect protein-protein interactions (PPI) of HSP complexes in the pathophysiology and therapeutic strategies of myocardial infarction. A comprehensive understanding of the cardioprotective role of PPIs of HSP complexes in myocardial infarction can provide new insights for MI or MIRI therapy.

HSP-Target of Therapeutic Agents in Sepsis Treatment.

Sepsis is a syndrome characterized by a dysregulated inflammatory response, cellular stress, and organ injury. Sepsis is the main cause of death in intensive care units worldwide, creating need for research and new therapeutic strategies. Heat shock protein (HSP) analyses have recently been developed in the context of sepsis. HSPs have a cytoprotection role in stress conditions, signal to immune cells, and activate the inflammatory response. Hence, HSP analyses have become an important focus in sepsis research, including the investigation of HSPs targeted by therapeutic agents used in sepsis treatment. Many therapeutic agents have been tested, and their HSP modulation showed promising results. Nonetheless, the heterogeneity in experimental designs and the diversity in therapeutic agents used make it difficult to understand their efficacy in sepsis treatment. Therefore, future investigations should include the analysis of parameters related to the early and late immune response in sepsis, HSP localization (intra or extracellular), and time to the onset of treatment after sepsis. They also should consider the differences in experimental sepsis models. In this review, we present the main results of studies on therapeutic agents in targeting HSPs in sepsis treatment. We also discuss limitations and possibilities for future investigations regarding HSP modulators.

Autoantibodies against the cell surface-associated chaperone GRP78 stimulate tumor growth via tissue factor.

Tumor cells display on their surface several molecular chaperones that normally reside in the endoplasmic reticulum. Because this display is unique to cancer cells, these chaperones are attractive targets for drug development. Previous epitope-mapping of autoantibodies (AutoAbs) from prostate cancer patients identified the 78-kDa glucose-regulated protein (GRP78) as one such target. Although we previously showed that anti-GRP78 AutoAbs increase tissue factor (TF) procoagulant activity on the surface of tumor cells, the direct effect of TF activation on tumor growth was not examined. In this study, we explore the interplay between the AutoAbs against cell surface-associated GRP78, TF expression/activity, and prostate cancer progression. First, we show that tumor GRP78 expression correlates with disease stage and that anti-GRP78 AutoAb levels parallel prostate-specific antigen concentrations in patient-derived serum samples. Second, we demonstrate that these anti-GRP78 AutoAbs target cell-surface GRP78, activating the unfolded protein response and inducing tumor cell proliferation through a TF-dependent mechanism, a specific effect reversed by neutralization or immunodepletion of the AutoAb pool. Finally, these AutoAbs enhance tumor growth in mice bearing human prostate cancer xenografts, and heparin derivatives specifically abrogate this effect by blocking AutoAb binding to cell-surface GRP78 and decreasing TF expression/activity. Together, these results establish a molecular mechanism in which AutoAbs against cell-surface GRP78 drive TF-mediated tumor progression in an experimental model of prostate cancer. Heparin derivatives counteract this mechanism and, as such, represent potentially appealing compounds to be evaluated in well-designed translational clinical trials.

A Randomized Phase 2 Study of ADXS11-001 Listeria monocytogenes-Listeriolysin O Immunotherapy With or Without Cisplatin in Treatment of Advanced Cervical Cancer.

OBJECTIVES: A global unmet medical need exists for effective treatments for persistent, recurrent, or metastatic cervical cancer, as patients have a short life expectancy. Recently, immunotherapies have shown promising survival benefits for patients with advanced forms of cancer. Axalimogene filolisbac (ADXS11-001), a Listeria monocytogenes immunotherapy with a broad effect on the immune system, is under investigation for treatment of human papillomavirus-associated cancers including cervical cancer. METHODS: This phase 2 study evaluated the safety and efficacy of ADXS11-001, administered with or without cisplatin, in patients with recurrent/refractory cervical cancer following prior chemotherapy and/or radiotherapy. A total of 109 patients were treated, and 69 were evaluable for tumor response at equal to or more than 3 months postbaseline. RESULTS: Median overall survival (OS) was comparable between treatment groups (ADXS11-001: 8.28 months; 95% confidence interval [CI], 5.85-10.5 months; ADXS11-001 + cisplatin: 8.78 months; 95% CI, 7.4-13.3 months). The 12- and 18-month milestone OS rates were 30.9% versus 38.9%, and 23.6% versus 25.9% for each group, respectively (34.9% and 24.8% combined). Median progression-free survival (6.10 vs 6.08 months) and the overall response rate (17.1% vs 14.7%) were similar for both groups. ADXS11-001 was generally well tolerated; adverse events were predominantly mild to moderate in severity and not related to treatment. More adverse events were reported in the combination group (429 vs 275). CONCLUSIONS: These promising safety and efficacy results, including the encouraging 12-month 34.9% combined OS rate, warrant further investigation of ADXS11-001 for treatment of recurrent/refractory cervical cancer.

Radiofrequency ablation (RFA)-induced systemic tumor growth can be reduced by suppression of resultant heat shock proteins.

PURPOSE: To determine the role of hepatic radiofrequency ablation (RFA) heating parameters and their activation of heat shock proteins (HSPs) in modulating distant tumor growth. METHODS AND MATERIALS: First, to study the effects of RFA dose on distant tumor growth, rats with subcutaneous R3230 adenocarcinoma (10 ± 1 mm) were assigned to 3 different hepatic RF doses (60 °C × 10 min, 70 °C × 5 min or 90 °C × 2 min) that induced identical sized ablation or sham (n = 6/arm). Post-RFA tumor growth rates, cellular proliferation (Ki-67) and microvascular density (MVD) were compared at 7d. Next, the effect of low and high power doses on local HSP70 expression and cellular infiltration (α-SMA + myofibroblasts and CD68 + macrophages), cytokine (IL-6) and growth factor (HGF and VEGF) expression was assessed. Finally, 60 °C × 10 min and 90 °C × 2 min RFA were combined with anti-HSP micellar quercetin (MicQ, 2 mg/ml). A total of 150 animals were used. RESULTS: Lower RF heating (70 °C × 5 min and 60 °C × 10 min) resulted in larger distant tumors at 7d (19.2 ± 0.8 mm for both) while higher RF heating (90 °C × 2) led to less distant tumor growth (16.7 ± 1.5 mm, p < .01 for both), though increased over sham (13.5 ± 0.5 mm, p < .01). Ki-67 and MVD correlated with tumor growth (p < .01 for all). Additionally, lower dose 60 °C × 10 min hepatic RFA had more periablational HSP70 compared to 90 °C × 2 min (rim: 1.106 ± 163 µm vs. 360 ± 18 µm, p < .001), with similar trends for periablational α-SMA, CD68 and CDC47 (p < .01 for all). Anti-HSP70 MicQ blocked distant tumor growth for lower dose (60 °C × 10: RF/MicQ 14.6 ± 0.4 mm vs. RF alone: 18.1 ± 0.4 mm, p < .01) and higher dose RFA (90 °C × 2 min: RF/MicQ 14.6 ± 0.5 mm vs. RF alone: 16.4 ± 0.7 mm, p < .01). CONCLUSION: Hepatic RF heating parameters alter periablational HSP70, which can influence and stimulate distant tumor growth. Modulation of RF heating parameters alone or in combination with adjuvant HSP inhibition can reduce unwanted, off-target systemic tumorigenic effects.

Immunotherapy for malignant gliomas.

Cancer immunotherapy aims to harness the innate ability of the immune system to recognize and destroy malignant cells. Immunotherapy for malignant gliomas is an emerging field that promises the possibility of highly specific and less toxic treatment compared to conventional chemotherapy. In addition, immunotherapy has the added benefit of sustained efficacy once immunologic memory is induced. Although there are numerous therapeutic agents that boost general immune function and facilitate improved antitumor immunity, to date, immunotherapy for gliomas has focused primarily on active vaccination against tumor-specific antigens. The results of numerous early phase clinical trials demonstrate promising results for vaccine therapy, but no therapy has yet proven to improve survival in a randomized, controlled trial. The major barrier to immunotherapy in malignant gliomas is tumor-induced immunosuppression. The mechanisms of immunosuppression are only now being elucidated, but clearly involve a combination of factors including regulatory T cells, tumor-associated PD-L1 expression, and CTLA-4 signaling. Immunomodulatory agents have been developed to combat these immunosuppressive factors and have demonstrated efficacy in other cancers. The future of glioma immunotherapy likely lies in a combination of active vaccination and immune checkpoint inhibition.

Roles of heat-shock proteins in innate and adaptive immunity.

Heat-shock proteins (HSPs) are the most abundant and ubiquitous soluble intracellular proteins. In single-cell organisms, invertebrates and vertebrates, they perform a multitude of housekeeping functions that are essential for cellular survival. In higher vertebrates, their ability to interact with a wide range of proteins and peptides--a property that is shared by major histocompatibility complex molecules--has made the HSPs uniquely suited to an important role in organismal survival by their participation in innate and adaptive immune responses. The immunological properties of HSPs enable them to be used in new immunotherapies of cancers and infections.

Immunoglobulin heavy-chain-binding protein (BiP): a stress protein that has the potential to be a novel therapy for rheumatoid arthritis.

Immunoglobulin heavy-chain-binding protein (BiP) or glucose-regulated protein 78 (Grp78) is a vital ubiquitous resident of the endoplasmic reticulum (ER). As an intracellular chaperone, BiP correctly folds nascent polypeptides within the ER and regulates the unfolded protein response ensuring protection of the cell from denatured protein and reinforcing its anti-apoptotic role, when the cell is under stress. Additionally, BiP is a member of the heat-shock protein (HSP) 70 family and, as a stress protein, is up-regulated by conditions of reduced oxygen and glucose. Cell stress induces surface expression and secretion of BiP. Consequently, BiP is detectable in several bodily fluids including serum, synovial fluid (SF) and oviductal fluid. However, as an extracellular protein, BiP has additional properties that are quite distinct from the intracellular functions. Extracellular BiP is immunoregulatory and anti-inflammatory causing development of tolerogenic dendritic cells (DCs), induction of regulatory T-cells, abrogation of osteoclast development and function, induction of anti-inflammatory cytokine production, including interleukin (IL)-10, IL-1 receptor antagonist and soluble tumour necrosis factor (TNF)-receptor type II, and attenuation of TNFα and IL-6. Together, these functions help drive the resolution of inflammation. Disease models of inflammatory arthritis have helped to demonstrate the novel mode of action of BiP in which the pharmacokinetics and pharmacodynamics are dissociated. The three murine models to be discussed each show BiP induced long-term therapeutic protection and therefore has potential for long-lasting drug-free therapy in rheumatoid arthritis (RA).

Active-specific immunotherapy of human cancers with the heat shock protein Gp96-revisited.

The passive administration of specific antibodies that selectively target tumors is a well-known strategy in cancer treatment. Active immunotherapy using peptide vaccines, in contrast, is expected to induce specific, cytolytic T cells in the patient, which react against tumor antigens and destroy malignant cells. Although several concepts exist, the identification and low immunogenicity of tumor-specific peptides remain a serious problem. Heat shock proteins (HSPs), notably glycoprotein (Gp) 96, are of special interest, because they are able to take molecular peptide-fingerprints of the protein array characteristic for a particular cell. Association of Gp96 with peptides has been shown to be essential for crosspresentation and activation of T cells. Consequently, Gp96-peptide complexes extracted from cancer cells harbor the tumor-specific peptides and are immunogenic, thus offering a tool for active immunization against the tumor. Already, several immunotherapy studies of human cancers have been carried out, showing no severe adverse effects but unfortunately only limited improvement in the clinical outcome. Vitespen, a commercial HSP-peptide complex vaccine based on tumor-derived Gp96, seems to induce an improved overall survival for subsets of early stage melanoma and kidney cancer patients. The limited access to vaccine material derived from the autologous tumor requires the development of alternative protocols. Moreover, counteracting immunosuppressive mechanisms induced by the malignancy might further improve the efficacy of vaccinations. This review critically analyzes the current state of clinical immunotherapy with Gp96, with special attention to Vitespen.

6-Shogaol Exhibits a Promoting Effect with Tax via Binding HSP60 in Non-Small-Cell Lung Cancer.

Non-small-cell lung cancer (NSCLC) is a prevalent malignant tumor with high morbidity and mortality rates worldwide. Although surgical resection, adjuvant radiotherapy/chemotherapy, and targeted molecular therapy are the cornerstones of NSCLC treatment, NSCLC is associated with high recurrence rates and drug resistance. This study analyzed the potential targets and pathways of 6-Shogaol (6-SH) in NSCLC, showing that 6-SH binds to heat-shock 60 kDa protein (HSP60) in A549 cells, induces cell apoptosis, and arrests the cell cycle possibly by disrupting the mitochondrial function. HSP60 was identified as the target of 6-SH and 6-SH-induced HSP60 degradation which was mediated by the proteasome. The binding of 6-SH with HSP60 altered its stability, inhibited the ERK, Stat3, PI3K, Akt, and mTOR signaling pathways, and Tax acted synergistically with 6-SH, indicating that 6-SH could be developed as a potential therapeutic agent for an NSCLC treatment.

Parkinson's Disease-Specific Autoantibodies against the Neuroprotective Co-Chaperone STIP1.

Parkinson's disease (PD) is a debilitating movement disorder characterised by the loss of dopaminergic neurons in the substantia nigra. As neuroprotective agents mitigating the rate of neurodegeneration are unavailable, the current therapies largely focus only on symptomatic relief. Here, we identified stress-inducible phosphoprotein 1 (STIP1) as a putative neuroprotective factor targeted by PD-specific autoantibodies. STIP1 is a co-chaperone with reported neuroprotective capacities in mouse Alzheimer's disease and stroke models. With human dopaminergic neurons derived from induced pluripotent stem cells, STIP1 was found to alleviate staurosporine-induced neurotoxicity. A case-control study involving 50 PD patients (average age = 62.94 ± 8.48, Hoehn and Yahr >2 = 55%) and 50 age-matched healthy controls (HCs) (average age = 63.1 ± 8) further revealed high levels of STIP1 autoantibodies in 20% of PD patients compared to 10% of HCs. Using an overlapping peptide library covering the STIP1 protein, we identified four PD-specific B cell epitopes that were not recognised in HCs. All of these epitopes were located within regions crucial for STIP1's chaperone function or prion protein association. Our clinical and neuro-immunological studies highlight the potential of the STIP1 co-chaperone as an endogenous neuroprotective agent in PD and suggest the possible involvement of autoimmune mechanisms via the production of autoantibodies in a subset of individuals.

Liposome-templated gold nanoparticles for precisely temperature-controlled photothermal therapy based on heat shock protein expression.

Mild temperature photothermal therapy is gaining more and more attention due to high safety, high specificity and moderate efficacy. However, the therapeutical outcome of mild photothermal therapy is limited due to the overexpression of heat shock proteins (HSPs). Therefore, the precise management of HSP expression is the key to improvement of mild temperature photothermal therapy. However, the correlation between HSP expression and photothermal temperature in vivo is still unclear. To precisely control the photothermal temperature by managing the HSP expression, we quantified the HSP expression at different photothermal temperatures after irradiation on liposome-templated gold nanoparticles, which have high photostability, high photothermal conversion efficiency and low temperature fluctuation (smaller than 1 â„ƒ). We found that the expression of HSP70 was least at 47 â„ƒ, which was the optimal temperature for HSP management. We chose to co-administrate HSP70 inhibitor during 47 â„ƒ photothermal therapy, leading to greatly enhanced tumor inhibition. Our precise temperature-controlled photothermal therapy based on HSP expression offers a new strategy for clinical tumor photothermal therapy.

HSP60 in cancer: a promising biomarker for diagnosis and a potentially useful target for treatment.

Heat shock proteins (HSPs), most of which are molecular chaperones, are highly conserved proteins produced by cells under physiological stress or pathological conditions. HSP60 (57-69 kDa) can promote or inhibit cell apoptosis through different mechanisms, and its abnormal expression is also related to tumour cell metastasis and drug resistance. In recent years, HSP60 has received increasing attention in the field of cancer research due to its potential as a diagnostic and prognostic biomarker or therapeutic target. However, in different types of cancer, the specific mechanisms of abnormally expressed HSP60 in tumour carcinogenesis and drug resistance are complicated and still require further study. In this article, we comprehensively review the regulative mechanisms of HSP60 on apoptosis, its applications as a cancer diagnostic biomarker and a therapeutic target, evidence of involvement in tumour resistance and the applications of exosomal HSP60 in liquid biopsy. By evaluating the current findings of HSP60 in cancer research, we highlight some core issues that need to be addressed for the use of HSP60 as a diagnostic or prognostic biomarker and therapeutic target in certain types of cancer.

HSP90α induces immunosuppressive myeloid cells in melanoma via TLR4 signaling.

BACKGROUND: Tumor cells modulate host immunity by secreting extracellular vesicles (EV) and soluble factors. Their interactions with myeloid cells lead to the generation of myeloid-derived suppressor cells (MDSC), which inhibit the antitumor function of T and NK cells. We demonstrated previously that EV derived from mouse and human melanoma cells induced immunosuppressive activity via increased expression of programmed cell death ligand 1 (PD-L1) on myeloid cells that was dependent on the heat-shock protein 90α (HSP90α) in EV. Here, we investigated whether soluble HSP90α could convert monocytes into MDSC. METHODS: CD14 monocytes were isolated from the peripheral blood of healthy donors, incubated with human recombinant HSP90α (rHSP90α) alone or in the presence of inhibitors of TLR4 signaling and analyzed by flow cytometry. Inhibition of T cell proliferation assay was applied to assess the immunosuppressive function of rHSP90α-treated monocytes. HSP90α levels were measured by ELISA in plasma of patients with advanced melanoma and correlated with clinical outcome. RESULTS: We found that the incubation of monocytes with rHSP90α resulted in a strong upregulation of PD-L1 expression, whereas reactive oxygen species (ROS) and nitric oxide (NO) production as well as the expression of arginase-1, ectoenzymes CD39 and CD73 remained unchanged. The PD-L1 upregulation was blocked by anti-TLR4 antibodies and a nuclear factor-κB inhibitor. rHSP90α-treated monocytes displayed the downregulation of HLA-DR expression and acquired the resistance to apoptosis. Moreover, these monocytes were converted into MDSC as indicated by their capacity to inhibit T cell proliferation, which was mediated by TLR4 signaling as well as PD-L1 and indoleamine 2,3-dioxygenase (IDO) 1 expression. Higher levels of HSP90α in plasma of patients with melanoma correlated with augmented PD-L1 expression on circulating monocytic (M)-MDSC. Patients with melanoma with high levels of HSP90α displayed shorter progression-free survival (PFS) on the treatment with immune checkpoint inhibitors (ICIs). CONCLUSION: Our findings demonstrated that soluble rHSP90α increased the resistance of normal human monocytes to apoptosis and converted them into immunosuppressive MDSC via TLR4 signaling that stimulated PD-L1 and IDO-1 expression. Furthermore, patients with melanoma with high concentrations of HSP90α displayed increased PD-L1 expression on M-MDSC and reduced PFS after ICI therapy, suggesting HSP90α as a promising therapeutic target for overcoming immunosuppression in melanoma.