An investigation into the potential use of serum Hsp70 as a novel tumour biomarker for Hsp90 inhibitors

Current status and breakthroughs in treating advanced non-small cell lung cancer with EGFR exon 20 insertion mutations

Recently, targeted therapy and immunotherapy have emerged as effective treatment options for non-small cell lung cancer (NSCLC). This progress has been facilitated by the rapid development of diagnostic and therapeutic technologies and the continuous research and development of new drugs, leading to a new era in precision medicine for NSCLC. This is a breakthrough for patients with common mutations in the human epidermal growth factor receptor (EGFR) gene in NSCLC. Consequently, the use of targeted drugs has significantly improved survival. Nevertheless, certain rare genetic mutations are referred to as EGFR exon 20 insertion (ex20ins) mutations, which differ in structure from conventional EGFR gene mutations, namely, exon 19 deletion mutations (19-Del) and exon 21 point mutations. Owing to their distinct structural characteristics, patients harboring these EGFR ex20ins mutations are unresponsive to traditional tyrosine kinase inhibitor (TKI) therapy. This particular group of patients did not fall within the scope of their applicability. However, the activating A763_Y764insFQEA mutation elicits a more pronounced response than mutations in the near and far regions of the C-helix immediately following it and should, therefore, be treated differently. Currently, there is a lack of effective treatments for EGFR ex20ins mutations NSCLC. The efficacy of chemotherapy has been relatively favorable, whereas the effectiveness of immunotherapy remains ambiguous owing to inadequate clinical data. In addition, the efficacy of the first- and second-generation targeted drugs remains limited. However, third-generation and novel targeted drugs have proven to be effective. Although novel EGFR-TKIs are expected to treat EGFR ex20ins mutations in patients with NSCLC, they face many challenges. The main focus of this review is on emerging therapies that target NSCLC with EGFR ex20ins and highlight major ongoing clinical trials while also providing an overview of the associated challenges and research advancements in this area.

Is It Still Possible to Think about HSP70 as a Therapeutic Target in Onco-Hematological Diseases?

The search for molecules to be targeted that are involved in apoptosis resistance/increased survival and pathogenesis of onco-hematological malignancies is ongoing since these diseases are still not completely understood. Over the years, a good candidate has been identified in the Heat Shock Protein of 70kDa (HSP70), a molecule defined as “the most cytoprotective protein ever been described”. HSP70 is induced in response to a wide variety of physiological and environmental insults, allowing cells to survive lethal conditions. This molecular chaperone has been detected and studied in almost all the onco-hematological diseases and is also correlated to poor prognosis and resistance to therapy. In this review, we give an overview of the discoveries that have led us to consider HSP70 as a therapeutic target for mono- or combination-therapies in acute and chronic leukemias, multiple myeloma and different types of lymphomas. In this excursus, we will also consider HSP70 partners, such as its transcription factor HSF1 or its co-chaperones whose druggability could indirectly affect HSP70. Finally, we will try to answer the question asked in the title of this review considering that, despite the effort made by research in this field, HSP70 inhibitors never reached the clinic.

PACE4-altCT isoform of proprotein convertase PACE4 as tissue and plasmatic biomarker for prostate cancer

The proprotein convertase PACE4 has demonstrated value as a viable therapeutic target in prostate cancer (PCa). A novel isoform named PACE4-altCT, which arises in neoplastic lesions, plays an important role in tumor progression and has been validated as a pharmacological target. With the discovery of its overexpression in PCa and the alternative splicing of its pre-RNA to generate an oncogenic C-terminally modified isoform named PACE4-altCT, understanding and validating its value as a potential biomarker is of great interest either from prognostic or targeted therapy intervention. Expression of ERG in LNCaP cells was used to investigate the relationship between ERG expression occurring in PCa cells and PACE4-altCT expression by Western blot and qPCR. Using immunohistochemistry, the expression levels of PACE4 isoforms in patient tissues were investigated and correlated with ERG tumor status and Gleason score. An ELISA method was developed using affinity purified recombinant protein and used for quantitative analysis of plasma concentrations of PACE4-altCT and used for correlation. In contrast with the consensual isoform, PACE4-altCT was only strongly overexpressed in prostate cancer patients, correlated with ERG expression levels. Despite its intracellular retention PACE4-altCT could be detected in the plasma of most patients with prostate cancer, whereas it was only found at low levels in normal patients whereas total plasmatic PACE4 levels did not vary significantly between groups. Our study demonstrates that PACE4-altCT is strongly overexpressed in prostate cancer using both immunohistochemical and ELISA techniques and may have some interesting potential as a biomarker.

The HSP Immune Network in Cancer

Heat shock proteins are molecular chaperones which support tumor development by regulating various cellular processes including unfolded protein response, mitochondrial bioenergetics, apoptosis, autophagy, necroptosis, lipid metabolism, angiogenesis, cancer cell stemness, epithelial-mesenchymal transition and tumor immunity. Apart from their intracellular activities, HSPs have also distinct extracellular functions. However, the role that HSP chaperones play in the regulation of immune responses inside and outside the cell is not yet clear. Herein, we explore the intracellular and extracellular immunologic functions of HSPs in cancer. A broader understanding of how HSPs modulate immune responses may provide critical insights for the development of effective immunotherapies.

Heat Shock Proteins in Urine as Cancer Biomarkers

Heat shock proteins (HSPs) are a large family of molecular chaperones, which have shown to be implicated in various hallmarks of cancer such as resistance to apoptosis, invasion, angiogenesis, induction of immune tolerance, and metastasis. Several studies reported aberrant expression of HSPs in liquid biopsies of cancer patients and this has opened new perspectives on the use of HSPs as biomarkers of cancer. However, no specific diagnostic, predictive, or prognostic HSP chaperone-based urine biomarker has been yet discovered. On the other hand, divergent expression of HSPs has also been observed in other pathologies, including neurodegenerative and cardiovascular diseases, suggesting that new approaches should be employed for the discovery of cancer-specific HSP biomarkers. In this study, we propose a new strategy in identifying cancer-specific HSP-based biomarkers, where HSP networks in urine can be used to predict cancer. By analyzing HSPs present in urine, we could predict cancer with approximately 90% precision by machine learning approach. We aim to show that coupling the machine learning approach and the understanding of how HSPs operate, including their functional cycles, collaboration with and within networks, is effective in defining patients with cancer, which may provide the basis for future discoveries of novel HSP-based biomarkers of cancer.

A novel dual HDAC and HSP90 inhibitor, MPT0G449, downregulates oncogenic pathways in human acute leukemia in vitro and in vivo

Acute leukemia is a highly heterogeneous disease; therefore, combination therapy is commonly used for patient treatment. Drug–drug interaction is a major concern of combined therapy; hence, dual/multi-target inhibitors have become a dominant approach for cancer drug development. HDACs and HSP90 are involved in the activation of various oncogenic signaling pathways, including PI3K/AKT/mTOR, JAK/STAT, and RAF/MEK/ERK, which are also highly enriched in acute leukemia gene expression profiles. Therefore, we suggest that dual HDAC and HSP90 inhibitors could represent a novel therapeutic approach for acute leukemia. MPT0G449 is a dual effect inhibitor, and it showed cytotoxic effectiveness in acute leukemia cells. Molecular docking analysis indicated that MPT0G449 possessed dual HDAC and HSP90 inhibitory abilities. Furthermore, MPT0G449 induced G₂ arrest and caspase-mediated cell apoptosis in acute leukemia cells. The oncogenic signaling molecules AKT, mTOR, STAT3, STAT5, MEK, and ERK were significantly downregulated after MPT0G449 treatment in HL-60 and MOLT-4 cells. In vivo xenograft models confirmed the antitumor activity and showed the upregulation of acetyl-histone H3 and HSP70, biomarkers of pan-HDAC and HSP90 inhibition, with MPT0G449 treatment. These findings suggest that the dual inhibition of HDAC and HSP90 can suppress the expression of oncogenic pathways in acute leukemia, and MPT0G449 represents a novel therapeutic for anticancer treatment.

Cell Surface GRP94 as a Novel Emerging Therapeutic Target for Monoclonal Antibody Cancer Therapy

Glucose-regulated protein 94 (GRP94) is an endoplasmic reticulum (ER)-resident member of the heat shock protein 90 (HSP90) family. In physiological conditions, it plays a vital role in regulating biological functions, including chaperoning cellular proteins in the ER lumen, maintaining calcium homeostasis, and modulating immune system function. Recently, several reports have shown the functional role and clinical relevance of GRP94 overexpression in the progression and metastasis of several cancers. Therefore, the current review highlights GRP94’s physiological and pathophysiological roles in normal and cancer cells. Additionally, the unmet medical needs of small chemical inhibitors and the current development status of monoclonal antibodies specifically targeting GRP94 will be discussed to emphasize the importance of cell surface GRP94 as an emerging therapeutic target in monoclonal antibody therapy for cancer.

Extracellular heat shock proteins and cancer: New perspectives

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High expression of extracellular heat shock proteins (HSPs) indicates highly aggressive tumors.

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HSP profiling of extracellular vesicles (EVs) derived from various biological fluids and released by immune cells may open new perspectives for an identification of diagnostic, prognostic and predictive biomarkers of cancer.

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Identification of specific microRNAs targeting HSPs in EVs may be a promising strategy for the discovery of novel biomarkers of cancer.

Heat shock proteins (HSPs) are a large family of molecular chaperones aberrantly expressed in cancer. The expression of HSPs in tumor cells has been shown to be implicated in the regulation of apoptosis, immune responses, angiogenesis and metastasis. Given that extracellular vesicles (EVs) can serve as potential source for the discovery of clinically useful biomarkers and therapeutic targets, it is of particular interest to study proteomic profiling of HSPs in EVs derived from various biological fluids of cancer patients. Furthermore, a divergent expression of circulating microRNAs (miRNAs) in patient samples has opened new opportunities in exploiting miRNAs as diagnostic tools. Herein, we address the current literature on the expression of extracellular HSPs with particular interest in HSPs in EVs derived from various biological fluids of cancer patients and different types of immune cells as promising targets for identification of clinical biomarkers of cancer. We also discuss the emerging role of miRNAs in HSP regulation for the discovery of blood-based biomarkers of cancer. We outline the importance of understanding relationships between various HSP networks and co-chaperones and propose the model for identification of HSP signatures in cancer. Elucidating the role of HSPs in EVs from the proteomic and miRNAs perspectives may provide new opportunities for the discovery of novel biomarkers of cancer.

Circulating and Synovial Fluid Heat Shock Protein 70 Are Correlated with Severity in Knee Osteoarthritis

OBJECTIVE

Heat shock proteins are molecules rapidly produced under conditions of environmental stress, and involve in protecting the cells structural integrity and function. Osteoarthritis (OA) is a chronic destructive disorder of the joints manifested by the ongoing deterioration and loss of articular cartilage. The present study aimed to analyze circulating and synovial heat shock protein (Hsp70) values in knee osteoarthritis patients and healthy controls and to determine their relationship with the radiographic grading of the severity of knee OA.

DESIGN

Seventy-two subjects with knee OA and 30 control participants were recruited. Circulating and joint fluid Hsp70 values were quantified by commercially available enzyme-linked immunosorbent assay.

RESULTS

Circulating Hsp70 was markedly higher in knee OA patients compared with that of healthy volunteers (P = 0.01). Correspondingly, synovial fluid Hsp70 was 3-fold greater than paired circulating Hsp70 samples (P < 0.001). Further analysis revealed that circulating and joint fluid Hsp70 values were significantly related with the radiographic severity of knee OA (r = 0.413, P < 0.001 and r = 0.658, P < 0.001, respectively). Subsequently, circulating Hsp70 value was directly associated with joint fluid Hsp70 value (r = 0.704, P < 0.001).

CONCLUSIONS

Circulating and synovial Hsp70 levels were positively correlated with the radiographic severity of knee OA. Hsp70 could represent a potential biochemical marker for predicting the severity and may play a fundamental part in the pathogenic mechanism of knee OA.

Camel whey protein protects lymphocytes from apoptosis via the PI3K–AKT, NF-κB, ATF-3, and HSP-70 signaling pathways in heat-stressed male mice

Heat stress (HS) is an environmental factor that depresses the immune systems that mediate dysfunctional immune cells. Camel whey protein (CWP) can scavenge free radicals and enhance immunity. This study investigated the impact of dietary supplementation with CWP on immune dysfunction induced by exposure to HS. Male mice (n = 45) were distributed among 3 groups: control group; HS group; and HS mice that were orally administered CWP (HS + CWP group). The HS group exhibited elevated levels of reactive oxygen species (ROS) and pro-inflammatory cytokines (interleukin (IL)-1β, IL-6, tumor necrosis factor-α) as well as a significant reduction in the IL-2 and IL-4 levels. Exposure to HS resulted in impaired phosphorylation of AKT and IκB-α (nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha); increased expression of activating transcription factor 3 (ATF-3) and 70 kDa heat shock proteins (HSP70); and aberrant distribution of CD3+ T cells and CD20+ B cells in the thymus and spleen. Interestingly, HS mice treated with CWP presented significantly restored levels of reactive oxygen species and pro-inflammatory cytokines near the levels observed in the control mice. Furthermore, supplementation of HS mice with CWP enhanced the phosphorylation of AKT and IκB-α; attenuated the expression of ATF-3, HSP70, and HSP90; and improved T and B cell distributions in the thymus and spleen. Our findings reveal a potential immunomodulatory effect of CWP in attenuating immune dysfunction induced by exposure to thermal stress.

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

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

Identification of Novel Response and Predictive Biomarkers to Hsp90 Inhibitors Through Proteomic Profiling of Patient-derived Prostate Tumor Explants

Inhibition of the heat shock protein 90 (Hsp90) chaperone is a promising therapeutic strategy to target expression of the androgen receptor (AR) and other oncogenic drivers in prostate cancer cells. However, identification of clinically-relevant responses and predictive biomarkers is essential to maximize efficacy and treatment personalization. Here, we combined mass spectrometry (MS)-based proteomic analyses with a unique patient-derived explant (PDE) model that retains the complex microenvironment of primary prostate tumors. Independent discovery and validation cohorts of PDEs (n = 16 and 30, respectively) were cultured in the absence or presence of Hsp90 inhibitors AUY922 or 17-AAG. PDEs were analyzed by LC-MS/MS with a hyper-reaction monitoring data independent acquisition (HRM-DIA) workflow, and differentially expressed proteins identified using repeated measure analysis of variance (ANOVA; raw p value <0.01). Using gene set enrichment, we found striking conservation of the most significantly AUY922-altered gene pathways between the discovery and validation cohorts, indicating that our experimental and analysis workflows were robust. Eight proteins were selectively altered across both cohorts by the most potent inhibitor, AUY922, including TIMP1, SERPINA3 and CYP51A (adjusted p < 0.01). The AUY922-mediated decrease in secretory TIMP1 was validated by ELISA of the PDE culture medium. We next exploited the heterogeneous response of PDEs to 17-AAG in order to detect predictive biomarkers of response and identified PCBP3 as a marker with increased expression in PDEs that had no response or increased in proliferation. Also, 17-AAG treatment led to increased expression of DNAJA1 in PDEs that exhibited a cytostatic response, revealing potential drug resistance mechanisms. This selective regulation of DNAJA1 was validated by Western blot analysis. Our study establishes "proof-of-principle" that proteomic profiling of drug-treated PDEs represents an effective and clinically-relevant strategy for identification of biomarkers that associate with certain tumor-specific responses.

Intracellular antigens as targets for antibody based immunotherapy of malignant diseases

This review discusses the potential use of intracellular tumor antigens as targets of antibody-based immunotherapy for the treatment of solid tumors. In addition, it describes the characteristics of the intracellular tumor antigens targeted with antibodies which have been described in the literature and have been identified in the authors' laboratory. Finally, the mechanism underlying the trafficking of the intracellular tumor antigens to the plasma membrane of tumor cells are reviewed.

Magnetic nanoparticle clusters radiosensitise human nasopharyngeal and lung cancer cells after alternating magnetic field treatment

PURPOSE

Heat generated by magnetic nanoparticle clusters (MNCs) in an alternating magnetic field (AMF) can be used for hyperthermia cancer treatment. Here, we have synthesised polyacrylic acid-coated MNCs according to previous report, with the ability to increase particle stability in suspension. Radiosensitisation effects of the MNCs under an AMF were investigated in vitro and in vivo.

MATERIALS AND METHODS

MTT assay, flow cytometry, clone formation assay, Western blotting, and a γ-H2AX experiment were used to explore the biocompatibility and radiosensitisation effect of the MNCs and their putative radiosensitisation mechanism. An NCI-H460 mouse xenograft model was used to investigate the anti-tumour effect under an AMF in vivo.

RESULTS

The temperature of MNC fluids at different concentrations (200 μg/mL to 2 mg/mL) increased rapidly. The MNCs were endocytosed by the cells and were found to be biocompatible. Hsp70 and caspase-3 were found to be up-regulated upon MNCs under an AMF, radiation, and combination of both treatments. MNCs under an AMF efficiently radiosensitised both CNE-2 cells and NCI-H460 cells. Finally, the tumour inhibition rate after treatment with MNCs under an AMF and radiation was significantly higher than that after either treatment alone. The mechanism of radiosensitisation putatively involves inhibition of DNA repair and induction of apoptosis.

CONCLUSIONS

The MNC fluids under an AMF enhanced the radiosensitivity of tumour cells both in vitro and in vivo.

Role of membrane Hsp70 in radiation sensitivity of tumor cells

BACKGROUND

The major stress-inducible heat shock protein 70 (Hsp70) is frequently overexpressed in the cytosol and integrated in the plasma membrane of tumor cells via lipid anchorage. Following stress such as non-lethal irradiation Hsp70 synthesis is up-regulated. Intracellular located Hsp70 is known to exert cytoprotective properties, however, less is known about membrane (m)Hsp70. Herein, we investigate the role of mHsp70 in the sensitivity towards irradiation in tumor sublines that differ in their cytosolic and/or mHsp70 levels.

METHODS

The isogenic human colon carcinoma sublines CX(+) with stable high and CX(-) with stable low expression of mHsp70 were generated by fluorescence activated cell sorting, the mouse mammary carcinoma sublines 4 T1 (4 T1 ctrl) and Hsp70 knock-down (4 T1 Hsp70 KD) were produced using the CRISPR/Cas9 system, and the Hsp70 down-regulation in human lung carcinoma sublines H1339 ctrl/H1339 HSF-1 KD and EPLC-272H ctrl/EPLC-272H HSF-1 KD was achieved by small interfering (si)RNA against Heat shock factor 1 (HSF-1). Cytosolic and mHsp70 was quantified by Western blot analysis/ELISA and flow cytometry; double strand breaks (DSBs) and apoptosis were measured by flow cytometry using antibodies against γH2AX and real-time PCR (RT-PCR) using primers and antibodies directed against apoptosis related genes; and radiation sensitivity was determined using clonogenic cell surviving assays.

RESULTS

CX(+)/CX(-) tumor cells exhibited similar cytosolic but differed significantly in their mHsp70 levels, 4 T1 ctrl/4 T1 Hsp70 KD cells showed significant differences in their cytosolic and mHsp70 levels and H1339 ctrl/H1339 HSF-1 KD and EPLC-272H ctrl/EPLC-272H HSF-1 KD lung carcinoma cell sublines had similar mHsp70 but significantly different cytosolic Hsp70 levels. γH2AX was significantly up-regulated in irradiated CX(-) and 4 T1 Hsp70 KD with low basal mHsp70 levels, but not in their mHsp70 high expressing counterparts, irrespectively of their cytosolic Hsp70 content. After irradiation γH2AX, Caspase 3/7 and Annexin V were up-regulated in the lung carcinoma sublines, but no significant differences were observed in H1339 ctrl/H1339 HSF-1 KD, and EPLC-272H ctrl/EPLC-272H HSF-1 KD that exhibit identical mHsp70 but different cytosolic Hsp70 levels. Clonogenic cell survival was significantly lower in CX(-) and 4 T1 Hsp70 KD cells with low mHsp70 expression, than in CX+ and 4 T1 ctrl cells, whereas no difference in clonogenic cell survival was observed in H1339 ctrl/H1339 HSF-1 KD and EPLC-272H ctrl/ EPLC-272H HSF-1 KD sublines with identical mHsp70 but different cytosolic Hsp70 levels.

CONCLUSION

In summary, our results indicate that mHsp70 has an impact on radiation resistance.

Extracellular cell stress proteins as biomarkers of human disease

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

A first-in-human phase I, dose-escalation, multicentre study of HSP990 administered orally in adult patients with advanced solid malignancies

BACKGROUND

Heat-shock protein 990 (HSP990) is a potent and selective synthetic small-molecule HSP90 inhibitor. The primary objectives of this phase I first-in-human study were to determine dose-limiting toxicities (DLTs), maximum-tolerated dose (MTD) and recommended phase II dose (RP2D). Secondary objectives included characterisation of the safety profile, pharmacokinetics (PKs) and pharmacodynamics (PDs).

METHODS

Heat-shock protein 990 was administered orally once or two times weekly on a 28-day cycle schedule in patients with advanced solid tumours. Dose escalation was guided by a Bayesian logistic regression model with overdose control.

RESULTS

A total of 64 patients were enrolled. Fifty-three patients received HSP990 once weekly at 2.5, 5, 10, 20, 30, 50 or 60 mg, whereas 11 patients received HSP990 two times weekly at 25 mg. Median duration of exposure was 8 weeks (range 1-116 weeks) and 12 patients remained on treatment for >16 weeks. Dose-limiting toxicities occurred in seven patients and included diarrhoea, QTc prolongation, ALT/AST elevations and central neurological toxicities. The most common drug-related adverse events were diarrhoea, fatigue and decreased appetite. Further dose escalation beyond 60 mg once weekly was not possible owing to neurological toxicity. Rapid absorption, no drug accumulation and large interpatient variability in PK exposures were observed. No objective responses were seen; 25 patients had a best overall response of stable disease.

CONCLUSIONS

Heat-shock protein 990 is relatively well tolerated, with neurological toxicity being the most relevant DLT. The single agent MTD/RP2D of HSP990 was declared at 50 mg once weekly.

Hsp90 blockade modulates bullous pemphigoid IgG-induced IL-8 production by keratinocytes

Bullous pemphigoid (BP) is the most common subepidermal autoimmune blistering skin disease characterized by autoantibodies against the hemidesmosomal proteins BP180 and BP230. The cell stress chaperone heat shock protein 90 (Hsp90) has been implicated in inflammatory responses, and recent evidence suggests that it represents a novel treatment target in autoimmune bullous diseases. The aim of the study was to investigate the contribution of Hsp90 to the proinflammatory cytokine production in keratinocytes induced by autoantibodies to BP180 from BP patient serum. HaCaT cells were treated with purified human BP or normal IgG in the absence or presence of the Hsp90 blocker 17-DMAG and effects on viability, interleukin 6 (IL-6) and IL-8 (cytokines critical for BP pathology), NFκB (their major transcription factor), and Hsp70 (marker of effective Hsp90 inhibition and potent negative regulator of inflammatory responses) were investigated. We found that BP IgG stimulated IL-6 and IL-8 release from HaCaT cells and that non-toxic doses of 17-DMAG inhibited this IL-8, but not IL-6 secretion in a dose- and time-dependent fashion. Inhibition of this IL-8 production was also observed at the transcriptional level. In addition, 17-DMAG treatment blunted BP IgG-mediated upregulation of NFκB activity and was associated with Hsp70 induction. This study provides important insights that Hsp90 is involved as crucial regulator in anti-BP180 IgG-induced production of keratinocyte-derived IL-8. By adding to the knowledge of the multimodal anti-inflammatory effects of Hsp90 blockade, our data further support the introduction of Hsp90 inhibitors into the clinical setting for treatment of autoimmune diseases, especially for BP.

Visualising dual downregulation of insulin-like growth factor receptor-1 and vascular endothelial growth factor-A by heat shock protein 90 inhibition effect in triple negative breast cancer

PURPOSE

Triple negative breast cancer (TNBC) is biologically characterised by heterogeneous presence of molecular pathways underlying it. Insulin-like growth factor receptor-1 (IGF-1R) expression and vascular endothelial growth factor-A (VEGF-A) have been identified as key factors in these pathways in TNBC. In this study, we aimed at in vivo PET imaging the effect of heat shock protein (Hsp) 90 inhibition by means of NVP-AUY922 on these pathways, with zirconium-89 ((89)Zr) labelled antibodies targeting IGF-1R and VEGF-A.

MATERIALS AND METHODS

In vitro NVP-AUY922 effects on cellular IGF-1R expression and VEGF-A secretion were determined in MCF-7 and MDA-MB-231 cell lines. Moreover human TNBC bearing MDA-MB-231 mice received 50mg/kg NVP-AUY922 or vehicle q3d intraperitoneally for 21days. PET scans with (89)Zr-MAB391 and (89)Zr-bevacizumab for visualisation of IGF-1R and VEGF-A were performed before and during treatment. Ex vivo biodistribution and correlative tissue analyses were performed.

RESULTS

NVP-AUY922 treatment reduced IGF-1R expression and VEGF-A excretion in both cell lines. Hsp90 inhibition lowered tumour uptake on (89)Zr-MAB391-PET by 37.3% (P<0.01) and on (89)Zr-bevacizumab-PET by 44.4% (P<0.01). This was confirmed by ex vivo biodistribution with a reduction of 41.3% injected dose (ID)/g for (89)Zr-MAB391 and 37.8% ID/g for (89)Zr-bevacizumab, while no differences were observed for other tissues. This coincided with reduced IGF-1R expression and mean vessel density in the NVP-AUY922 treated tumours.

CONCLUSION

(89)Zr-MAB391 and (89)Zr-bevacizumab PET reflect effect of Hsp90 inhibitors and can therefore potentially be used to monitor therapeutic effects of Hsp90 inhibitor therapy in TNBC.

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

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

Hsp70--a biomarker for tumor detection and monitoring of outcome of radiation therapy in patients with squamous cell carcinoma of the head and neck

BACKGROUND

Tumor but not normal cells frequently overexpress heat shock protein 70 (Hsp70) and present it on their cell surface (mHsp70) from where it can be actively released. Therefore, membrane (mHsp70) and soluble Hsp70 (sHsp70) were investigated as potential tumor biomarkers and for monitoring the outcome of radiation therapy.

METHODS

Biopsies and blood were collected from patients with squamous cell carcinoma of the head and neck (SCCHN) at different time points (before, during therapy and in the follow-up period). Hsp70 membrane expression was determined on single cell suspensions of tumor biopsies and reference tissues by flow cytometry, sHsp70 protein and antibody levels were determined in the serum of patients and healthy donors by ELISA and NK cell markers that are related to the presence of sHsp70 were analyzed in the patient's peripheral blood lymphocytes (PBL).

RESULTS

Tumor biopsies exhibited significantly increased mHsp70 expression levels compared to the reference tissue. Soluble Hsp70 levels were significantly higher in SCCHN patients compared to healthy human volunteers and high mHsp70 expression levels on tumor cells were associated with high sHsp70 levels in the serum of patients. Following surgery and radiotherapy sHsp70 levels in patients dropped in patients without tumor relapse in the follow-up period. In contrast to sHsp70 protein, anti-Hsp70 antibody levels remained nearly unaltered in the serum of SCCHN patients before and after therapy. Furthermore, sHsp70 protein but not anti-Hsp70 antibody levels were found to be associated with the tumor volume in SCCHN patients before start of therapy. The expression densities of the activatory NK cell markers CD56, CD94, NKG2D, NKp30, Nkp44, and NKp46 differed in patients following therapeutic intervention. A significant increase in the density of NKG2D was observed in SCCHN patients in the follow-up period after surgery and radiotherapy.

CONCLUSION

We suggest sHsp70 as a potential biomarker for detecting tumors and for monitoring the clinical outcome of radiotherapy in SCCHN patients.

Inhibitory effects of heat shock protein 90 blockade on proinflammatory human Th1 and Th17 cell subpopulations

Background

Heat shock protein 90 (Hsp90), a chaperone that regulates activity of many client proteins responsible for cellular growth, differentiation, and apoptosis, has been proposed as an important clinical and preclinical therapeutic target in a number of malignancies and autoimmune diseases, respectively. In this study, we evaluated the effects of pharmacological Hsp90 inhibition on human proinflammatory T cell responses.

Findings

Using anti-CD3 antibody-stimulated human peripheral blood mononuclear cell cultures, we observed that Hsp90 inhibition by non-toxic concentrations of the geldanamycin derivative 17-DMAG significantly blocked T cell proliferation, reduced IFN-γ and IL-17 expression on CD4⁺ T lymphocytes, and arrested secretion of proinflammatory IFN-γ, TNF-α, and IL-17, cytokines characteristic of Th1 and Th17 cells, respectively. These effects were associated with inhibition of NF-kB activity, upregulation of Hsp70 protein expression, and disruption of T cell-specific nonreceptor tyrosine kinase Lck activation.

Conclusions

Our results further support the potential use of Hsp90 inhibitors in patients with autoimmune diseases where uncontrolled Th1 or Th17 activation frequently occurs.

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

PURPOSE

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

METHODS AND MATERIALS

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

RESULTS

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

CONCLUSION

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

Phase I study of BIIB028, a selective heat shock protein 90 inhibitor, in patients with refractory metastatic or locally advanced solid tumors

PURPOSE

Heat shot protein 90 (Hsp90) is a ubiquitous molecular chaperone involved in protein folding, activation, and assembly, including key mediators of signal transduction, cell-cycle control, and transcriptional regulation. We conducted a phase I dose-finding and pharmacokinetic/pharmacodynamic study of BIIB028, a prodrug designed to inhibit Hsp90 activity.

EXPERIMENTAL DESIGN

Patients with advanced solid tumors were enrolled and received escalating doses of BIIB028 intravenously twice a week in 21-day cycles (3+3 design). Response was evaluated after two cycles.

RESULTS

Forty-one patients received doses of 6 to 192 mg/m2. The maximum tolerated dose was 144 mg/m2. Dose-limiting toxicities were syncope (n=1) and fatigue (n=1). Common toxicities at least possibly related to drug were grades 1 to 2, including fatigue (46%), diarrhea (44%), nausea (44%), vomiting (29%), hot flushes (29%), and abnormal dreams (17%). The concentration-time curves for day 1 and day 18 for both prodrug and active metabolite (CF2772) showed a negligible difference. There was a dose-dependent increase in plasma exposure for BIIB028 (CF3647) and CF2772 with plasma half-life of 0.5 and 2.1 hours, respectively. Pharmacodynamic analyses showed significant increases in Hsp70 in peripheral blood mononuclear cells and significantly decreased circulating human EGF receptor-2 extracellular domain in all patients who received BIIB028 at dose levels of 48 mg/m2 or more. Stable disease for at least eight cycles (24 weeks) was achieved in 5 (12%) patients (for durations of 6, 6, 8, 12.5, and 19 months).

CONCLUSION

BIIB028 is a well-tolerated molecule that showed target impact and was associated with prolonged stable disease in two patients.

Identification and characterization of a novel human methyltransferase modulating Hsp70 protein function through lysine methylation

Hsp70 proteins constitute an evolutionarily conserved protein family of ATP-dependent molecular chaperones involved in a wide range of biological processes. Mammalian Hsp70 proteins are subject to various post-translational modifications, including methylation, but for most of these, a functional role has not been attributed. In this study, we identified the methyltransferase METTL21A as the enzyme responsible for trimethylation of a conserved lysine residue found in several human Hsp70 (HSPA) proteins. This enzyme, denoted by us as HSPA lysine (K) methyltransferase (HSPA-KMT), was found to catalyze trimethylation of various Hsp70 family members both in vitro and in vivo, and the reaction was stimulated by ATP. Furthermore, we show that HSPA-KMT exclusively methylates 70-kDa proteins in mammalian protein extracts, demonstrating that it is a highly specific enzyme. Finally, we show that trimethylation of HSPA8 (Hsc70) has functional consequences, as it alters the affinity of the chaperone for both the monomeric and fibrillar forms of the Parkinson disease-associated protein α-synuclein.

Mini-review: Foldosome regulation of androgen receptor action in prostate cancer

Steroid hormone receptors play diverse roles in many aspects of human physiology including cell division, apoptosis and homeostasis, tissue differentiation, sexual development and response to stress. These ligand-activated transcription factors require the functional activity of numerous chaperone and chaperone-associated proteins, collectively termed the foldosome, at the crucial step of ligand recognition and binding. Since the initial isolation of foldosome components and pioneering research by Pratt, Toft and colleagues we understand much regarding cytosolic receptor function. The classical view, that the role of foldosome components is restricted to the cytosol, has been modified over recent years by research highlighting additional roles of chaperone proteins in nuclear translocation and target gene expression. Further, dysregulation of chaperone activity and expression has been implicated in various cancers, including breast and prostate cancer. Consequently, the foldosome provides an attractive therapeutic target in steroid hormone receptor-driven malignancies. This review summarises current knowledge of how the foldosome impacts upon androgen receptor signalling, which is the key therapeutic target on prostate cancer, and how foldosome components may be used as biomarkers or therapeutic targets in this disease.

A first in human, safety, pharmacokinetics, and clinical activity phase I study of once weekly administration of the Hsp90 inhibitor ganetespib (STA-9090) in patients with solid malignancies

Background

This phase I study investigated the maximum tolerated dose (MTD), safety, pharmacokinetics and antitumor activity of ganetespib in patients with solid malignancies.

Methods

Patients were enrolled in cohorts of escalating ganetespib doses, given as 1 hour IV infusion, once weekly for 3 weeks, followed by a 1-week rest until disease progression or unacceptable toxicity. Endpoints included safety, pharmacokinetic and pharmacodynamic parameters and preliminary clinical activity.

Results

Fifty-three patients were treated at doses escalating from 7 to 259 mg/m². The most common adverse events were Grade 1 and 2 diarrhea, fatigue, nausea or vomiting. Dose-limiting toxicities (DLT) observed were: one Grade 3 amylase elevation (150 mg/m²), one Grade 3 diarrhea and one Grade 3 and one Grade 4 asthenia (259 mg/m²). The MTD was 216 mg/m² and the recommended phase 2 dose was established at 200 mg/m² given IV at Days 1, 8, and 15 every 4 weeks. There was a linear relationship between dose and exposure. Plasma HSP70 protein levels remained elevated for over a week post treatment. Disease control rate (objective response and stable disease at ≥ 16 weeks) was 24.4%.

Conclusions

Ganetespib is well tolerated as a weekly infusion for 3 of every 4 weeks cycle. The recommended phase II dose is 200 mg/m², and is associated with an acceptable tolerability profile.

Trial registration

NCT00687934

Hsp90: still a viable target in prostate cancer

Heat shock protein 90 (Hsp90) is a molecular chaperone that regulates the maturation, activation and stability of critical signaling proteins that drive the development and progression of prostate cancer, including the androgen receptor. Despite robust preclinical data demonstrating anti-tumor activity of first-generation Hsp90 inhibitors in prostate cancer, poor clinical responses initially cast doubt over the clinical utility of this class of agent. Recent advances in compound design and development, use of novel preclinical models and further biological insights into Hsp90 structure and function have now stimulated a resurgence in enthusiasm for these drugs as a therapeutic option. This review highlights how the development of new-generation Hsp90 inhibitors with improved physical and pharmacological properties is unfolding, and discusses the potential contexts for their use either as single agents or in combination, for men with metastatic prostate cancer.

Phase II study of the HSP90-inhibitor BIIB021 in gastrointestinal stromal tumors

BACKGROUND

HSP90 inhibition leads to proteosomal degradation of activated KIT and has in vitro activity against gastrointestinal stromal tumors (GIST). BIIB021 is an oral non-ansamycin HSP90 inhibitor. We carried out a phase II study of BIIB021 in patients with GIST refractory to imatinib and sunitinib.

PATIENTS AND METHODS

The primary end-point was metabolic partial response (mPR) as assessed by fluorodeoxyglucose positron emission tomography (FDG-PET). The secondary end-points were pharmacokinetic assessments of BIIB021 and pharmacodynamic assessments of HSP70. Twenty-three patients were treated on two schedules: 12 pts received 600 mg twice a week (BIW) and 11 patients received 400 mg three times a week (TIW). All had prior imatinib and sunitinib but stopped>14 days before starting BIIB021.

RESULTS

The median age was 59 years (33-88 years), 61% male, 44% Eastern Cooperative Oncology Group 1 (ECOG1). The best response was PR by FDG-PET for five patients (3/12 at 600 mg BIW and 2/9 at 400 TIW) for an overall response rate of 22%. The response duration was 25-138 days. Adverse events (AEs) were mild to moderate. The mean Cmax was 1.5 µmol and the mean AUC was 2.9 µmol h. Cmax>1.5 µmol was associated with a decrease in standardized uptake value (SUVmax). HSP70 increased substantially following treatment.

CONCLUSIONS

This study met its primary end-point. BIIB021 leads to objective responses in refractory GIST patients. Pharmacodynamic studies confirmed HSP90 inhibition. Further evaluation of BIIB021 in GIST is warranted.

Evidence for efficacy of new Hsp90 inhibitors revealed by ex vivo culture of human prostate tumors

PURPOSE

Targeting Hsp90 has significant potential as a treatment for prostate cancer, but prototypical agents such as 17-allylamino-17 demethoxygeldanamycin (17-AAG) have been ineffective in clinical trials. Recently, a phase I study aimed at defining a biologically active dose reported the first response to an Hsp90 inhibitor in a patient with prostate cancer, which supports the development of new generation compounds for this disease.

EXPERIMENTAL DESIGN

The biological actions of two new synthetic Hsp90 inhibitors, NVP-AUY922 and NVP-HSP990, were evaluated in the prostate cancer cell lines PC-3, LNCaP, and VCaP and in an ex vivo culture model of human prostate cancer.

RESULTS

In cell lines, both NVP-AUY922 and NVP-HSP990 showed greater potency than 17-AAG with regard to modulation of Hsp90 client proteins, inhibition of proliferation, and induction of apoptotic cell death. In prostate tumors obtained from radical prostatectomy that were cultured ex vivo, treatment with 500 nmol/L of NVP-AUY922, NVP-HSP990, or 17-AAG caused equivalent target modulation, determined by the pharmacodynamic marker Hsp70, but only NVP-AUY922 and NVP-HSP990 showed antiproliferative and proapoptotic activity.

CONCLUSIONS

This study provides some of the first evidence that new generation Hsp90 inhibitors are capable of achieving biologic responses in human prostate tumors, with both NVP-AUY922 and NVP-HSP990 showing potent on-target efficacy. Importantly, the ex vivo culture technique has provided information on Hsp90 inhibitor action not previously observed in cell lines or animal models. This approach, therefore, has the potential to enable more rational selection of therapeutic agents and biomarkers of response for clinical trials.

Advances in the clinical development of heat shock protein 90 (Hsp90) inhibitors in cancers

Hsp90 is an ATP dependent molecular chaperone protein which integrates multiple oncogenic pathways. As such, Hsp90 inhibition is a promising anti-cancer strategy. Several inhibitors that act on Hsp90 by binding to its N-terminal ATP pocket have entered clinical evaluation. Robust pre-clinical data suggested anti-tumor activity in multiple cancer types. Clinically, encouraging results have been demonstrated in melanoma, acute myeloid leukemia, castrate refractory prostate cancer, non-small cell lung carcinoma and multiple myeloma. In breast cancer, proof-of-concept was demonstrated by first generation Hsp90 inhibitors in combination with trastuzumab mainly in human epidermal growth factor receptor 2 (HER2)+metastatic breast cancer. There are a multitude of second generation Hsp90 inhibitors currently under investigation. To date, however, there is no FDA approved Hsp90 inhibitor nor standardized assay to ascertain Hsp90 inhibition. This review summarizes the current status of both first and second generation Hsp90 inhibitors based on their chemical classification and stage of clinical development. It also discusses the pharmacodynamic assays currently implemented in clinic as well as other novel strategies aimed at enhancing the effectiveness of Hsp90 inhibitors. Ultimately, these efforts will aid in maximizing the full potential of this class of agents. This article is part of a Special Issue entitled: Heat Shock Protein 90 (HSP90).

Soluble HSPB1 regulates VEGF-mediated angiogenesis through their direct interaction

Endothelial cell function is critical for angiogenic balance in both physiological and pathological conditions, such as wound healing and cancer, respectively. We report here that soluble heat shock protein beta-1 (HSPB1) is released primarily from endothelial cells (ECs), and plays a key role in regulating angiogenic balance via direct interaction with vascular endothelial growth factor (VEGF). VEGF-mediated phosphorylation of intracellular HSPB1 inhibited the secretion of HSPB1 and their binding activity in ECs. Interestingly, co-culture of tumor ECs with tumor cells decreased HSPB1 secretion from tumor ECs, suggesting that inhibition of HSPB1 secretion allows VEGF to promote angiogenesis. Additionally, neutralization of HSPB1 in a primary mouse sarcoma model promoted tumor growth, indicating the anti-angiogenic role of soluble HSPB1. Overexpression of HSPB1 by HSPB1 adenovirus was sufficient to suppress lung metastases of CT26 colon carcinoma in vivo, while neutralization of HSPB1 promoted in vivo wound healing. While VEGF-induced regulation of angiogenesis has been studied extensively, these findings illustrate the key contribution of HSPB1-VEGF interactions in the balance between physiological and pathological angiogenesis.

Phase I evaluation of STA-1474, a prodrug of the novel HSP90 inhibitor ganetespib, in dogs with spontaneous cancer

BACKGROUND

The novel water soluble compound STA-1474 is metabolized to ganetespib (formerly STA-9090), a potent HSP90 inhibitor previously shown to kill canine tumor cell lines in vitro and inhibit tumor growth in the setting of murine xenografts. The purpose of the following study was to extend these observations and investigate the safety and efficacy of STA-1474 in dogs with spontaneous tumors.

METHODS AND FINDINGS

This was a Phase 1 trial in which dogs with spontaneous tumors received STA-1474 under one of three different dosing schemes. Pharmacokinetics, toxicities, biomarker changes, and tumor responses were assessed. Twenty-five dogs with a variety of cancers were enrolled. Toxicities were primarily gastrointestinal in nature consisting of diarrhea, vomiting, inappetence and lethargy. Upregulation of HSP70 protein expression was noted in both tumor specimens and PBMCs within 7 hours following drug administration. Measurable objective responses were observed in dogs with malignant mast cell disease (n = 3), osteosarcoma (n = 1), melanoma (n = 1) and thyroid carcinoma (n = 1), for a response rate of 24% (6/25). Stable disease (>10 weeks) was seen in 3 dogs, for a resultant overall biological activity of 36% (9/25).

CONCLUSIONS

This study provides evidence that STA-1474 exhibits biologic activity in a relevant large animal model of cancer. Given the similarities of canine and human cancers with respect to tumor biology and HSP90 activation, it is likely that STA-1474 and ganetespib will demonstrate comparable anti-cancer activity in human patients.

Co-Inhibition of HSP70/HSP90 Synergistically Sensitizes Nasopharyngeal Carcinoma Cells to Thermotherapy

The upregulation of both HSP70 and HSP90 frequently compromises the effects of thermotherapy. The co-inhibition of HSP70/HSP90 may be preferable to enhance the effects of thermotherapy on nasopharyngeal carcinoma cells. The changes of HSP70 and HSP90 were detected after thermotherapy in human nasopharyngeal cancer cell HNE1. 17-Dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG) and quercetin were used to inhibit the activity of HSP90 and HSP70. The enhanced effects were evaluated in vitro and in vivo. Both HSP70 and HSP90 were upregulated promptly in HNE1 after thermotherapy. Single inhibition of HSP70 resulted in overexpression and delayed descent of HSP90. The co-inhibition of HSP70/HSP90 with quercetin plus 17-DMAG significantly increased apoptosis in hyperthermia-treated HNE1 cells both in vitro and in vivo. The co-inhibition of HSP70/HSP90 synergistically sensitizes nasopharyngeal carcinoma cells to hyperthermia.

Targeting the dynamic HSP90 complex in cancer

The molecular chaperone heat shock protein 90 (HSP90) has been used by cancer cells to facilitate the function of numerous oncoproteins, and it can be argued that cancer cells are 'addicted' to HSP90. However, although recent reports of the early clinical efficacy of HSP90 inhibitors are encouraging, the optimal use of HSP90-targeted therapeutics will depend on understanding the complexity of HSP90 regulation and the degree to which HSP90 participates in both neoplastic and normal cellular physiology.