[Corrigendum] Hsp90 inhibitor 17‑AAG inhibits stem cell‑like properties and chemoresistance in osteosarcoma cells via the Hedgehog signaling pathway

Following the publication of the article, a concerned reader drew to the authors' attention that, in Fig. 1B and C on p. 316, two pairs of the data panels showing the results from invasion and migration assay experiments appeared to be overlapping, such that they would have been derived from the same original sources where they were intended to show the results from different experiments; moreover, on p. 1698, the '17‑AAG / MG‑63' data panels in Fig. 3B and C were also overlapping, albeit the images were presented at a different scale and in a slightly different orientation. After having examined their original data, the authors have realized that these figures were inadvertently assembled incorrectly. The corrected versions of Figs. 1 and 3, now showing the correct data in Fig. 1C (where the errors made in compiling the figure had occurred) and the correct data for the '17‑AAG / MG‑63' data panel in Fig. 3C, are shown on the next two pages. These corrections do not grossly affect either the results or the conclusions reported in this work. The authors all agree to the publication of this Corrigendum, and are grateful to the Editor of Oncology Reports for granting them the opportunity to correct the errors that were made during the assembly of these figures. Lastly, the authors apologize to the readership for any inconvenience these errors may have caused. [Oncology Reports 44: 313‑324, 2020; DOI: 10.3892/or.2020.7597].

TRPA1 activation and Hsp90 inhibition synergistically downregulate macrophage activation and inflammatory responses in vitro

BACKGROUND

Transient receptor potential ankyrin 1 (TRPA1) channels are known to be actively involved in various pathophysiological conditions, including neuronal inflammation, neuropathic pain, and various immunological responses. Heat shock protein 90 (Hsp90), a cytoplasmic molecular chaperone, is well-reported for various cellular and physiological processes. Hsp90 inhibition by various molecules has garnered importance for its therapeutic significance in the downregulation of inflammation and are proposed as anti-cancer drugs. However, the possible role of TRPA1 in the Hsp90-associated modulation of immune responses remains scanty.

RESULTS

Here, we have investigated the role of TRPA1 in regulating the anti-inflammatory effect of Hsp90 inhibition via 17-(allylamino)-17-demethoxygeldanamycin (17-AAG) in lipopolysaccharide (LPS) or phorbol 12-myristate 13-acetate (PMA) stimulation in RAW 264.7, a mouse macrophage cell lines and PMA differentiated THP-1, a human monocytic cell line similar to macrophages. Activation of TRPA1 with Allyl isothiocyanate (AITC) is observed to execute an anti-inflammatory role via augmenting Hsp90 inhibition-mediated anti-inflammatory responses towards LPS or PMA stimulation in macrophages, whereas inhibition of TRPA1 by 1,2,3,6-Tetrahydro-1,3-dimethyl-N-[4-(1-methylethyl)phenyl]-2,6-dioxo-7 H-purine-7-acetamide,2-(1,3-Dimethyl-2,6-dioxo-1,2,3,6-tetrahydro-7 H-purin-7-yl)-N-(4-isopropylphenyl)acetamide (HC-030031) downregulates these developments. LPS or PMA-induced macrophage activation was found to be regulated by TRPA1. The same was confirmed by studying the levels of activation markers (major histocompatibility complex II (MHCII), cluster of differentiation (CD) 80 (CD80), and CD86, pro-inflammatory cytokines (tumor necrosis factor (TNF) and interleukin 6 (IL-6)), NO (nitric oxide) production, differential expression of mitogen-activated protein kinase (MAPK) signaling pathways (p-p38 MAPK, phospho-extracellular signal-regulated kinase 1/2 (p-ERK 1/2), and phosphor-stress-activated protein kinase/c-Jun N-terminal kinase (p-SAPK/JNK)), and induction of apoptosis. Additionally, TRPA1 has been found to be an important contributor to intracellular calcium levels toward Hsp90 inhibition in LPS or PMA-stimulated macrophages.

CONCLUSION

This study indicates a significant role of TRPA1 in Hsp90 inhibition-mediated anti-inflammatory developments in LPS or PMA-stimulated macrophages. Activation of TRPA1 and inhibition of Hsp90 has synergistic roles towards regulating inflammatory responses associated with macrophages. The role of TRPA1 in Hsp90 inhibition-mediated modulation of macrophage responses may provide insights towards designing future novel therapeutic approaches to regulate various inflammatory responses.

Molecular docking and dynamics simulation study of quinones and pyrones from Alternaria solani and Alternaria alternata with HSP90: an important therapeutic target of cancer

Although cancer continues to be one of the world's major causes of death, current cancer drugs have many serious side effects. There remains a need for new anticancer agents to overcome these shortcomings. Alternaria is one of the most widespread fungal genera, many species of which produce several classes of metabolites with potential polypharmacological activities. A few quinones and pyrones from Alternaria spp. have proven to exert cytotoxic effects against certain cancer cell lines, but their molecular mode of action is not known. The current study aimed to investigate the potential mechanisms that underlie the anticancer activity of a few selected quinones and pyrones from Alternaria solani and Alternaria alternata by molecular docking and dynamic simulation approaches. The selected metabolites were screened for their binding affinity to Heat shock protein 90 (HSP90), which is a known anticancer drug target. Molecular docking studies have revealed that Macrosporin, Altersolanol B, Fonsecin, and Neoaltenuene have good binding affinities with the target protein and the stabilities of the formed complexes were evaluated through molecular dynamics simulations. By analyzing the Root Mean Square Distance (RMSD), Root Mean Square Fluctuation (RMSF), and Principal Component Analysis (PCA) plots obtained from molecular dynamics simulations, this study shows that the complexes of all 4 lead molecules with target protein are stable over a 100 ns period. Molecular Mechanics Poisson-Boltzmann Surface Area (MM-PBSA) calculations were used to compute the binding free energies. The lead molecules were studied using in-silico analysis to determine their drug-likeness based on their Absorption, Distribution, Metabolism, Excretion and Toxicity (ADMET) and physicochemical properties. The results demonstrate that Macrosporin, Fonsecin, and Neoaltenuene could become promising anticancer molecules that target HSP90.Communicated by Ramaswamy H. Sarma.

In vivo antitumor efficacy of 17-AAG loaded PMMA in a human multiple myeloma xenograft mouse model

Multiple myeloma (MM) is a monoclonal malignancy characterized by abnormal proliferation of plasma cells. The disease clinically manifests as anemia, hypercalcemia, renal insufficiencies, and osteolytic damage. Osteolytic damage goes with severe bone pain, spinal instability, and pathological fracture, symptoms that are collectively referred to as multiple myeloma bone disease (MMBD). Polymethylmethacrylate (PMMA) bone cement is widely used for bone repair after MMBD surgery, owing to its excellent biomechanical properties and fast curing. To date, however, efficacy of drug-loading PMMA in inhibition of tumor growth and angiogenesis remains unknown. Here, we report that 17-AAG-loaded PMMA bone cement inhibits MM growth in vivo and suppresses tumor diffusion to peripheral tissues. In addition, 17-AAG-loaded PMMA promotes MM apoptosis by downregulating Bax and active Caspase-3.

HSP90β chaperoning SMURF1-mediated LATS proteasomal degradation in the regulation of bone formation

Heat shock protein 90 (HSP90) molecular chaperone is responsible for the stabilization and biological activity of a diverse set of client proteins. We have previously demonstrated that inhibition of HSP90 by 17-Demethoxy-17-allyaminogeldanmycin (17-AAG) not only reverses the glucocorticoid-induced bone loss but also enhances the basal level of bone mass in mice. Here, we investigate the potential mechanism underlying HSP90-associated osteoblast differentiation and bone formation. Knockdown of HSP90β but not HSP90α or inhibition of HSP90 by 17-AAG or NVP-BEP800 negates the protein levels of large tumor suppressor (LATS), the core kinases of Hippo signaling, resulting in the inactivation of LATS and activation of Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ), in the enhancement of osteoblastic differentiation. In contrast, genetic ablation of Lats1 in mesenchymal stem cells is sufficient to abolish the HSP90 inhibition-induced osteoblastic differentiation and bone formation. Mechanistically, HSP90β but not HSP90α chaperones and prevents the SMAD specific E3 ubiquitin protein ligase 1 (SMURF1)-mediated and ubiquitination-dependent LATS protein proteasomal degradation, whereas 17-AAG abolishes these effects of HSP90β. Thus, these results uncover the HSP90β chaperoning SMURF1-mediated LATS protein proteasomal degradation and the subsequent YAP/TAZ activation as a hitherto uncharacterized mechanism controlling osteoblastic differentiation and bone formation.

A Boolean-based machine learning framework identifies predictive biomarkers of HSP90-targeted therapy response in prostate cancer

Precision medicine has emerged as an important paradigm in oncology, driven by the significant heterogeneity of individual patients' tumour. A key prerequisite for effective implementation of precision oncology is the development of companion biomarkers that can predict response to anti-cancer therapies and guide patient selection for clinical trials and/or treatment. However, reliable predictive biomarkers are currently lacking for many anti-cancer therapies, hampering their clinical application. Here, we developed a novel machine learning-based framework to derive predictive multi-gene biomarker panels and associated expression signatures that accurately predict cancer drug sensitivity. We demonstrated the power of the approach by applying it to identify response biomarker panels for an Hsp90-based therapy in prostate cancer, using proteomic data profiled from prostate cancer patient-derived explants. Our approach employs a rational feature section strategy to maximise model performance, and innovatively utilizes Boolean algebra methods to derive specific expression signatures of the marker proteins. Given suitable data for model training, the approach is also applicable to other cancer drug agents in different tumour settings.

Inhibition of HSP90 Preserves Blood-Brain Barrier Integrity after Cortical Spreading Depression

Cortical spreading depression (CSD) is a pathophysiological mechanism underlying headache disorders, including migraine. Blood-brain barrier (BBB) permeability is increased during CSD. Recent papers have suggested that heat shock proteins (HSP) contribute to the integrity of the blood-brain barrier. In this study, the possible role of HSP90 in CSD-associated blood-brain barrier leak at the endothelial cell was investigated using an in vitro model, for the blood-endothelial barrier (BEB), and an in vivo model with an intact BBB. We measured barrier integrity using trans endothelial electric resistance (TEER) across a monolayer of rodent brain endothelial cells (bEnd.3), a sucrose uptake assay, and in situ brain perfusion using female Sprague Dawley rats. CSD was induced by application of 60 mM KCl for 5 min in in vitro experiments or cortical injection of KCl (1 M, 0.5 µL) through a dural cannula in vivo. HSP90 was selectively blocked by 17-AAG. Our data showed that preincubation with 17-AAG (1 µM) prevented the reduction of TEER values caused by the KCl pulse on the monolayer of bEnd.3 cells. The elevated uptake of 14C-sucrose across the same endothelial monolayer induced by the KCl pulse was significantly reduced after preincubation with HSP90 inhibitor. Pre-exposure to 17-AAG significantly mitigated the transient BBB leak after CSD induced by cortical KCl injection as determined by in situ brain perfusion in female rats. Our results demonstrated that inhibition of HSP90 with the selective agent 17-AAG reduced CSD-associated BEB/BBB paracellular leak. Overall, this novel observation supports HSP90 inhibition mitigates KCl-induced BBB permeability and suggests the development of new therapeutic approaches targeting HSP90 in headache disorders.

Hsp90 Inhibitors Prevent HSV-1 Replication by Directly Targeting UL42-Hsp90 Complex

Herpes simplex virus type I (HSV-1) is a member of the Alphaherpesvirinae family, which could initiate labial herpes caused by the reactivation of HSV-1 primary infection, and secondary infection even causes herpes encephalitis. The study presented here demonstrates that Hsp90 inhibitors (AT-533 and 17-AAG) directly targeted the HSV-1 UL42-Hsp90 complex, and Hsp90 interacted with HSV-1 UL42 in silicon and experiment. Interestingly, Hsp90 inhibitors also reduced virus titers of ACV-resistant clinical HSV-1 strains (153 and blue strain), revealing that HSV-1 UL42 would be a new target against ACV-resistant HSV-1 strains. Altogether, this present study indicates that Hsp90 inhibitors prevent HSV-1 proliferation by regulating the interaction between Hsp90 and HSV-1 UL42, suggesting a promising target for anti-HSV-1 therapies in the replication.

HSP90 Inhibitor 17-AAG Attenuates Nucleus Pulposus Inflammation and Catabolism Induced by M1-Polarized Macrophages

Overactivated inflammation and catabolism induced by proinflammatory macrophages are involved in the pathological processes of intervertebral disc (IVD) degeneration (IVDD). Our previous study suggested the protective role of inhibiting heat shock protein 90 (HSP90) in IVDD, while the underlying mechanisms need advanced research. The current study investigated the effects of HSP90 inhibitor 17-AAG on nucleus pulposus (NP) inflammation and catabolism induced by M1-polarized macrophages. Immunohistochemical staining of degenerated human IVD samples showed massive infiltration of macrophages, especially M1 phenotype, as well as elevated levels of interleukin (IL)-1β, tumor necrosis factor (TNF)-α and matrix metalloproteinase (MMP)13. The conditioned medium (CM) of inflamed NP cells (NPCs) enhanced M1 polarization of macrophages, while the CM of M1 macrophages but not M2 macrophages promoted the expression of inflammatory factors and matrix proteases in NPCs. Additionally, we found that 17-AAG could represent anti-inflammatory and anti-catabolic effects by modulating both macrophages and NPCs. On the one hand, 17-AAG attenuated the pro-inflammatory activity of M1 macrophages via inhibiting nuclear factor-κB (NF-κB) pathway and mitogen-activated protein kinase (MAPK) pathways. On the other hand, 17-AAG dampened M1-CM-induced inflammation and catabolism in NPCs by upregulating HSP70 and suppressing the Janus kinase 2 (JAK2)-signal transducer and activator of transcription 3 (STAT3) pathway. Moreover, both in vitro IVD culture models and murine disc puncture models supported that 17-AAG treatment decreased the levels of inflammatory factors and matrix proteases in IVD tissues. In conclusion, HSP90 inhibitor 17-AAG attenuates NP inflammation and catabolism induced by M1 macrophages, suggesting 17-AAG as a promising candidate for IVDD treatment.

Modulation of FLT3-ITD Localization and Targeting of Distinct Downstream Signaling Pathways as Potential Strategies to Overcome FLT3-Inhibitor Resistance

OBJECTIVES: Internal tandem duplications (ITDs) of the Fms-like tyrosine kinase 3 (FLT3) represent the most frequent molecular aberrations in acute myeloid leukemia (AML) and are associated with an inferior prognosis. The pattern of downstream activation by this constitutively activated receptor tyrosine kinase is influenced by the localization of FLT3-ITD depending on its glycosylation status. Different pharmacological approaches can affect FLT3-ITD-driven oncogenic pathways by the modulation of FLT3-ITD localization. AIMS: The objective of this study was to investigate the effects of N-glycosylation inhibitors (tunicamycin or 2-deoxy-D-glucose) or the histone deacetylase inhibitor valproic acid (VPA) on FLT3-ITD localization and downstream activity. We sought to determine the potential differences between the distinct FLT3-ITD variants, particularly concerning their susceptibility towards combined treatment by addressing either N-glycosylation and the heat shock protein 90 (HSP90) by 17-AAG, or by targeting the PI3K/AKT/mTOR pathway by rapamycin after treatment with VPA. METHODS: Murine Ba/F3 leukemia cell lines were stably transfected with distinct FLT3-ITD variants resulting in IL3-independent growth. These Ba/F3 FLT3-ITD cell lines or FLT3-ITD-expressing human MOLM13 cells were exposed to tunicamycin, 2-deoxy-D-glucose or VPA, and 17-AAG or rapamycin, and characterized in terms of downstream signaling by immunoblotting. FLT3 surface expression, apoptosis, and metabolic activity were analyzed by flow cytometry or an MTS assay. Proteome analysis by liquid chromatography–tandem mass spectrometry was performed to assess differential protein expression. RESULTS: The susceptibility of FLT3-ITD-expressing cells to 17-AAG after pre-treatment with tunicamycin or 2-deoxy-D-glucose was demonstrated. Importantly, in Ba/F3 cells that were stably expressing distinct FLT3-ITD variants that were located either in the juxtamembrane domain (JMD) or in the tyrosine kinase 1 domain (TKD1), response to the sequential treatments with tunicamycin and 17-AAG varied between individual FLT3-ITD motifs without dependence on the localization of the ITD. In all of the FLT3-ITD cell lines that were investigated, incubation with tunicamycin was accompanied by intracellular retention of FLT3-ITD due to the inhibition of glycosylation. In contrast, treatment of Ba/F3-FLT3-ITD cells with VPA was associated with a significant increase of FLT3-ITD surface expression depending on FLT3 protein synthesis. The allocation of FLT3 to different cellular compartments that was induced by tunicamycin, 2-deoxy-D-glucose, or VPA resulted in the activation of distinct downstream signaling pathways. Whole proteome analyses of Ba/F3 FLT3-ITD cells revealed up-regulation of the relevant chaperone proteins (e.g., calreticulin, calnexin, HSP90beta1) that are directly involved in the stabilization of FLT3-ITD or in its retention in the ER compartment. CONCLUSION: The allocation of FLT3-ITD to different cellular compartments and targeting distinct downstream signaling pathways by combined treatment with N-glycosylation and HSP90 inhibitors or VPA and rapamycin might represent new therapeutic strategies to overcome resistance towards tyrosine kinase inhibitors in FLT3-ITD-positive AML. The treatment approaches addressing N-glycosylation of FLT3-ITD appear to depend on patient-specific FLT3-ITD sequences, potentially affecting the efficacy of such pharmacological strategies.

Cytosolic and Mitochondrial Hsp90 in Cytokinesis, Mitochondrial DNA Replication, and Drug Action in Trypanosoma brucei

Trypanosoma brucei subspecies cause African sleeping sickness in humans, an infection that is commonly fatal if not treated, and available therapies are limited. Previous studies have shown that heat shock protein 90 (Hsp90) inhibitors have potent and vivid activity against bloodstream-form trypanosomes. Hsp90s are phylogenetically conserved and essential catalysts that function at the crux of cell biology, where they ensure the proper folding of proteins and their assembly into multicomponent complexes. To assess the specificity of Hsp90 inhibitors and further define the role of Hsp90s in African trypanosomes, we used RNA interference (RNAi) to knock down cytosolic and mitochondrial Hsp90s (HSP83 and HSP84, respectively). Loss of either protein led to cell death, but the phenotypes were distinctly different. Depletion of cytosolic HSP83 closely mimicked the consequences of chemically depleting Hsp90 activity with inhibitor 17-AAG. In these cells, cytokinesis was severely disrupted, and segregation of the kinetoplast (the massive mitochondrial DNA structure unique to this family of eukaryotic pathogens) was impaired, leading to cells with abnormal kinetoplast DNA (kDNA) structures. Quite differently, knockdown of mitochondrial HSP84 did not impair cytokinesis but halted the initiation of new kDNA synthesis, generating cells without kDNA. These findings highlight the central role of Hsp90s in chaperoning cell cycle regulators in trypanosomes, reveal their unique function in kinetoplast replication, and reinforce their specificity and value as drug targets.

Co-Expression of CD34, CD90, OV-6 and Cell-Surface Vimentin Defines Cancer Stem Cells of Hepatoblastoma, Which Are Affected by Hsp90 Inhibitor 17-AAG

Cancer stem cells (CSCs) are nowadays one of the major focuses in tumor research since this subpopulation was revealed to be a great obstacle for successful treatment. The identification of CSCs in pediatric solid tumors harbors major challenges because of the immature character of these tumors. Here, we present CD34, CD90, OV-6 and cell-surface vimentin (csVimentin) as reliable markers to identify CSCs in hepatoblastoma cell lines. We were able to identify CSC characteristics for the subset of CD34⁺CD90⁺OV-6⁺csVimentin⁺-co-expressing cells, such as pluripotency, self-renewal, increased expression of EMT markers and migration. Treatment with Cisplatin as the standard chemotherapeutic drug in hepatoblastoma therapy further revealed the chemo-resistance of this subset, which is a main characteristic of CSCs. When we treated the cells with the Hsp90 inhibitor 17-AAG, we observed a significant reduction in the CSC subset. With our study, we identified CSCs of hepatoblastoma using CD34, CD90, OV-6 and csVimentin. This set of markers could be helpful to estimate the success of novel therapeutic approaches, as resistant CSCs are responsible for tumor relapses.

Synergistic Action between PfHsp90 Inhibitor and PfRad51 Inhibitor Induces Elevated DNA Damage Sensitivity in the Malaria Parasite

The DNA recombinase Rad51 from the human malaria parasite Plasmodium falciparum has emerged as a potential drug target due to its central role in the homologous recombination (HR)-mediated double-strand break (DSB) repair pathway. Inhibition of the ATPase and strand exchange activity of P. falciparum Rad51 (PfRad51) by a small-molecule inhibitor, B02 [3-(phenylmethyl)-2-[(1E)-2-(3-pyridinyl)ethenyl]-4(3H)-quinazolinone], renders the parasite more sensitive to genotoxic agents. Here, we investigated whether the inhibition of the molecular chaperone PfHsp90 potentiates the antimalarial action of B02. We found that the PfHsp90 inhibitor 17-AAG [17-(allylamino)-17-demethoxygeldanamycin] exhibits strong synergism with B02 in both drug-sensitive (strain 3D7) and multidrug-resistant (strain Dd2) P. falciparum parasites. 17-AAG causes a greater than 200-fold decrease in the half-maximal inhibitory concentration (IC₅₀) of B02 in 3D7 parasites. Our results provide mechanistic insights into such profound synergism between 17-AAG and B02. We report that PfHsp90 physically interacts with PfRad51 and promotes the UV irradiation-induced DNA repair activity of PfRad51 by controlling its stability. We find that 17-AAG reduces PfRad51 protein levels by accelerating proteasomal degradation. Consequently, PfHsp90 inhibition renders the parasites more susceptible to the potent DNA-damaging agent methyl methanesulfonate (MMS) in a dose-dependent manner. Thus, our study provides a rationale for targeting PfHsp90 along with the recombinase PfRad51 for controlling malaria propagation.

Regulation of ClC-2 Chloride Channel Proteostasis by Molecular Chaperones: Correction of Leukodystrophy-Associated Defect

The ClC-2 channel plays a critical role in maintaining ion homeostasis in the brain and the testis. Loss-of-function mutations in the ClC-2-encoding human CLCN2 gene are linked to the white matter disease leukodystrophy. Clcn2-deficient mice display neuronal myelin vacuolation and testicular degeneration. Leukodystrophy-causing ClC-2 mutant channels are associated with anomalous proteostasis manifesting enhanced endoplasmic reticulum (ER)-associated degradation. The molecular nature of the ER quality control system for ClC-2 protein remains elusive. In mouse testicular tissues and Leydig cells, we demonstrated that endogenous ClC-2 co-existed in the same protein complex with the molecular chaperones heat shock protein 90β (Hsp90β) and heat shock cognate protein (Hsc70), as well as the associated co-chaperones Hsp70/Hsp90 organizing protein (HOP), activator of Hsp90 ATPase homolog 1 (Aha1), and FK506-binding protein 8 (FKBP8). Further biochemical analyses revealed that the Hsp90β-Hsc70 chaperone/co-chaperone system promoted mouse and human ClC-2 protein biogenesis. FKBP8 additionally facilitated membrane trafficking of ClC-2 channels. Interestingly, treatment with the Hsp90-targeting small molecule 17-allylamino-17-demethoxygeldanamycin (17-AAG) substantially boosted ClC-2 protein expression. Also, 17-AAG effectively increased both total and cell surface protein levels of leukodystrophy-causing loss-of-function ClC-2 mutant channels. Our findings highlight the therapeutic potential of 17-AAG in correcting anomalous ClC-2 proteostasis associated with leukodystrophy.

Heat Shock Protein 90 Chaperones E1A Early Protein of Adenovirus 5 and Is Essential for Replication of the Virus

Adenovirus infections tend to be mild, but they may pose a serious threat for young and immunocompromised individuals. The treatment is complicated because there are no approved safe and specific drugs for adenovirus infections. Here, we present evidence that 17-(Allylamino)-17-demethoxygeldanamycin (17-AAG), an inhibitor of Hsp90 chaperone, decreases the rate of human adenovirus 5 (HAdV-5) replication in cell cultures by 95%. 17-AAG inhibited the transcription of early and late genes of HAdV-5, replication of viral DNA, and expression of viral proteins. 6 h after infection, Hsp90 inhibition results in a 6.3-fold reduction of the newly synthesized E1A protein level without a decrease in the E1A mRNA level. However, the Hsp90 inhibition does not increase the decay rate of the E1A protein that was constitutively expressed in the cell before exposure to the inhibitor. The co-immunoprecipitation proved that E1A protein interacted with Hsp90. Altogether, the presented results show, for the first time. that Hsp90 chaperones newly synthesized, but not mature, E1A protein. Because E1A serves as a transcriptional co-activator of adenovirus early genes, the anti-adenoviral activity of the Hsp90 inhibitor might be explained by the decreased E1A level.

A Novel Mechanism of 17-AAG Therapeutic Efficacy on HSP90 Inhibition in MYCN-Amplified Neuroblastoma Cells

Background

Neuroblastoma is the most common pediatric extra-cranial nervous system tumor, originating from neural crest elements and giving rise to tumors in the adrenal medulla and sympathetic chain ganglia. Amplification of MYCN confers increased malignancy and poorer prognosis in high-risk neuroblastoma. Our SILAC proteomics analysis revealed over-expression of HSP90 in MYCN-amplified IMR-32 compared to the non-MYCN amplified SK-N-SH human neuroblastoma cells, rendering them highly resistant to therapeutic intervention.

Methods

We used cellular bio-functional (proliferation, migration/invasion, apoptosis, viability and stem-cell self-renewal) assays and Western blot analysis to elucidate the therapeutic efficacy of HSP90 inhibition with 17-AAG.

Results

17-AAG treatment significantly inhibited cellular proliferation, viability and migration/invasion and increased apoptosis in both cell lines. Moreover, drug treatment significantly abrogated stem-cell self-renewal potential in the MYCN-amplified IMR-32 cells. Differential tumorigenic protein expression revealed a novel mechanism of therapeutic efficacy after 17-AAG treatment with a significant downregulation of HMGA1, FABP5, Oct4, MYCN, prohibitin and p-L1CAM in SK-N-SH cells. However, we observed a significant up-regulation of p-L1CAM, MYCN and prohibitin, and significant down-regulation of Oct4, FABP5, HMGA1, p-ERK, cleaved/total caspase-3 and PARP1 in IMR-32 cells.

Conclusions

HSP90 inhibition revealed a novel therapeutic mechanism of antitumor activity in MYCN-amplified neuroblastoma cells that may enhance therapeutic sensitivity.

Fabrication of Paclitaxel and 17AAG-loaded Poly-ε-Caprolactone Nanoparticles for Breast Cancer Treatment

OBJECTIVE

The aim of this study is to design, fabricate and determine the cytotoxic effects of dual loaded paclitaxel and 17-AAG in stealth polymeric nanoparticles. The nanoparticles were fabricated by dispersion polymerization.

METHODS

Two breast cancer cell lines (MCF-7 and SKBR-3) were cultured and treated with media only, blank nanoparticles, paclitaxel (as a free drug), 17-AAG (free drug), paclitaxel + 17-AAG combination (as free drugs), and paclitaxel + 17-AAG combination loaded in poly-ε-caprolactone stealth nanoparticles. Each drug in the combination was half the concentration of the single free drug.

RESULTS

The cytotoxic effects of the paclitaxel treatment and that of the combination (free drug) were found to be similar in both SKBR3 and MCF7 cell lines. Similar cytotoxic effects were observed for the drug combination both in the drug loaded nanoparticles formulation and in free drug form for both cell lines.

CONCLUSION

Both paclitaxel and 17-AAG were effectively loaded and released from the polymeric nanoparticles. Paclitaxel (free drug), paclitaxel-17AAG combination (free drug), and dual drug-loaded nanoparticles had similar cytotoxic effects on both cell lines. Paclitaxel and 17-AAG combination resulted in synergistic effect: paclitaxel in the combination with 17-AAG was half its original concentration and yielded similar cytotoxic effect. The dose of paclitaxel was reduced without lowering its therapeutic efficacy.

The HSP90 Inhibitor, 17-AAG, Influences the Activation and Proliferation of T Lymphocytes via AKT/GSK3β Signaling in MRL/lpr Mice

Objective

To explore the molecular mechanism of 17-AAG in the treatment of systemic lupus erythematosus (SLE), and the effects of the heat shock protein 90 (HSP90) inhibitor 17-AAG on the activation and proliferation of lymphocytes and the AKT/GSK3β signaling pathway in MRL/lpr mice were detected.

Methods

MRL/lpr mice were randomly divided into the control group and the experimental group. The experimental group was injected intraperitoneally with 17-AAG, and T lymphocytes were separated by magnetic beads. Lymphocyte proliferation was detected by MTT and flow cytometry (FCM), and the expression of the HSP90 protein and PI3K/AKT signaling pathway-related proteins was detected by Western blotting. Renal histopathology and immune complex deposition were also observed in both groups.

Results

Immune complex deposition and inflammation decreased in kidneys from MRL/lpr mice in the experimental group. HSP90 protein expression, T lymphocyte proliferation and phosphorylated AKT and GSK3β levels also decreased in the experimental group.

Conclusion

17-AAG can inhibit the activation and proliferation of T lymphocytes and downregulate the AKT/GSK3β signaling pathway, which may be relevant for the treatment of SLE.

Hsp90 function is required for stable transcription of the baculovirus transactivator ie-1 gene

A molecular chaperone heat shock protein 90 (Hsp90) is required for efficient infection by several viruses. Hsp90 has been recently implicated in baculovirus infection, but its exact role remains obscure. This study investigated the effect of 17-N-allylamino-17-demethoxygeldanamycin (17-AAG), an Hsp90-specific inhibitor, on Bombyx mori nucleopolyhedrovirus (BmNPV) infection. The 17-AAG treatment significantly decreased the production of budded viruses and occlusion bodies in BmNPV-infected Bombyx mori cultured cells. Immunoblot and SDS-PAGE analyses showed that the expression of early and delayed early gene products, DBP and BRO, was delayed and dysregulated, and the very late gene product POLH was almost completely diminished. RT-qPCR experiments revealed that 17-AAG treatment did not affect initiation of the immediate early gene ie-1 expression, but the expression decreased by ∼50 % during the late stage of infection. 17-AAG treatment also decreased ie-1 promoter activity by ∼50 %. In addition, the expression of delayed early and late genes was dysregulated and inhibited, respectively. These results indicated that Hsp90 function is required for stable ie-1 transcription. Inhibiting Hsp90 function negatively affects ie-1 expression, resulting in dysregulation of delayed early genes and a severe decrease in late and very late gene expression.

Enzymatic biosynthesis and biological evaluation of novel 17-AAG glucoside as potential anti-cancer agents

A novel 17-allylamino-17-demethoxygeldanamycin (17-AAG) glucoside (1) was obtained from in vitro enzymatic glycosylation using a UDP-glycosyltransferase (YjiC). The water-solubility of compound 1 was approximately 10.5 times higher than that of the substrate, 17-AAG. Compound 1 showed potential anti-proliferative activities against five human cancer cell lines, with IC₅₀ values ranging from 5.26 to 28.52 μM. Further studies also indicated that compound 1 could inhibit the growth of CNE-2Z cells by inducing the degradation of Hsp90 client proteins (Akt, c-Raf, Bcl-2, and HIF-1α). In addition, compound 1 showed greater potential anti-tumor efficacy than 17-AAG in nude mice xenografted with CNE-2Z cells. Therefore, we suggest that in vitro enzymatic glycosylation is a powerful approach for the structural optimization of 17-AAG.

Hsp90β positively regulates μ-opioid receptor function

AIMS

Many μ-opioid receptor (MOR)-associated proteins can regulate the MOR signaling pathway. Using a bacterial two-hybrid screen, we found that the C-terminal of the MOR associated with heat shock protein 90 isoform β (Hsp90β). Here, we explored the effect of Hsp90β on MOR signaling transduction and function.

MAIN METHODS

The interaction of Hsp90β with MOR was detected by co-immunoprecipitation and immunofluorescence. The effects of Hsp90β on MOR signaling induced by opioids were studied in vitro and in vivo. The effects of the Hsp90β inhibitor 17-N-allylamino-17-demethoxygeldanamycin (17-AAG) on morphine tolerance and dependence were studied via a hot plate test and CPP test.

KEY FINDINGS

Hsp90β, instead of Hsp90α, interacted with the MOR in HEK293 cells and SH-SY5Y cells, and the interaction was augmented after morphine pretreatment. The interaction of Hsp90β and MOR increased the inhibition of cAMP and decreased PKA activity under opioid treatment. The functional Hsp90β-MOR complex also promoted the phosphorylation and internalization of the MOR induced by DAMGO in MOR-CHO cells. 17-AAG blocked Hsp90β-MOR interactions and decreased the effect of Hsp90β on the MOR signal transduction. In C57BL/6 mice, 17-AAG decreased morphine-induced acute anti-nociception in the hot plate test, with an increase in phosphorylated PKA and phosphorylated JNK and a decrease in phosphorylated CREB and phosphorylated ERK in murine brains. Chronic morphine treatment induced tolerance, and dependence was inhibited by 17-AAG co-administration.

SIGNIFICANCE

Hsp90β is a positive co-regulator of the MOR via the activation of a G-protein-dependent and β-arrestin-dependent pathway. Hsp90β has the potential to improve the pharmacologic profile of existing opiates. It is conceivable that in future clinical treatments, the Hsp90β inhibitor, 17-AAG, could decrease the tolerance and dependence in cancer patients induced by opioids.

17-Allylamino-Demethoxygeldanamycin Ameliorate Microthrombosis Via HSP90/RIP3/NLRP3 Pathway After Subarachnoid Hemorrhage in Rats

BACKGROUND

Subarachnoid hemorrhage (SAH) is a severe and emergent cerebrovascular disease, the prognosis of which usually very poor. Microthrombi formation highlighted with inflammation occurs early after SAH. As the main cause of DCI, microthrombosis associated with the prognosis of SAH. The aim of this study was to show HSP90 inhibitor 17-AAG effect on microthrombosis after SAH in rats.

METHODS

Ninety-five SD rats were used for the experiment. For time course study, the rats were randomly divided into five groups: sham group and SAH group with different time point (1d, 2d, 3d, 5d). Endovascular perforation method was conducted for SAH model. Neurological score, SAH grade, and mortality were measured after SAH. The samples of the left hemisphere brain were collected. The expression of HSP90 was detected by Western blot. The microthrombosis after SAH in rats' brain was detected by immunohistochemistry. For mechanism study, rats were randomly divided into three groups: sham, SAH + vehicle, and SAH +17-AAG (n = 6/group). 17-AAG was given by intraperitoneal injection (80 mg/kg) 1 h after SAH. Neurological function were measured at 24 h after SAH. The expression of RIP3, NLRP3, ASC, and IL-1β was measured by Western blot. Microthrombosis was detected by immunohistochemistry.

RESULTS

Our results showed that the HSP90 protein level increased and peaked at 2 days after SAH. Microthrombosis caused by SAH was increased in 1 day and peaked at 2 days after SAH. Administration HSP90 specific inhibitor 17-AAG reduced expression of RIP3, NLRP3, ASC, and IL-1β, reduced microthrombosis after SAH, and improved neurobehavior when compared to vehicle group.

CONCLUSIONS

17-AAG can ameliorate microthrombosis via HSP90/RIP3/NLRP3 pathway and improve neurobehavior after SAH.

Dihydropyrimidine Dehydrogenase Levels in Colorectal Cancer Cells Treated with a Combination of Heat Shock Protein 90 Inhibitor and Oxaliplatin or Capecitabine

Purpose: Dihydropyrimidine dehydrogenase (DPD) is the principal enzyme in the catabolism of fluoropyrimidine drugs including capecitabine. A recent report has suggested that oxaliplatin chemotherapy is associated with elevated DPD levels and chemoresistance pattern. As a newly developed chemotherapeutic agent, 17-allyloamino-17-demethoxy-geldanamycin (17-AAG) can be effective in combination therapy with oxaliplatin and capecitabine in colorectal cancer (CRC). DPD expression level can be a predictive factor in oxaliplatin and capecitabine-based chemotherapy. We evaluated DPD in mRNA and protein levels with new treatments: 17-AAG in combination with oxaliplatin and capecitabine in HT-29 and HCT-116 cell lines. Methods: Drug sensitivity was determined by the water-soluble tetrazolium-1 assay in a previous survey. Then, we evaluated the expression levels of DPD and its relationship with the chemotherapy response in capecitabine, oxaliplatin, and 17-AAG treated cases in single and combination cases in two panels of CRC cell lines. DPD gene and protein expression levels were determined by real-time polymerase chain reaction and western blotting assay, respectively. Results: DPD gene expression levels insignificantly increased in single-treated cases versus untreated controls in both cell lines versus controls. Then, the capecitabine and oxaliplatin were added in double combinations, where DPD gene and protein expression increased in combination cases compared to pre-chemotherapy and single drug treatments. Conclusion: The elevated levels of cytotoxicity in more effective combinations could be related to a different mechanism apart from DPD mediating effects or high DPD level in the remaining resistance cells (drug-insensitive cells), which should be investigated in subsequent studies.

Establishment of three-dimensional canine osteosarcoma cell lines showing vasculogenic mimicry and evaluation of biological properties after treatment with 17-AAG

Vasculogenic mimicry (VM) is an alternative type of blood perfusion characterized by formation of non-endothelial cell-lined microcirculatory channels and is responsible for aggressive tumour biology and increased tumour-related mortality. VM-correlated genes are associated with vascular endothelial grown factor receptor 1 (VEGFR1), and hypoxia-related (hypoxia inducible factor 1 α-HIF1α) signalling pathways, whose molecules are client proteins of Hsp90 (heat shock protein 90) and are potential therapeutic targets. This pilot study was aimed to investigate vasculogenic mimicry in a three-dimensional (3D) cell culture system of two aggressive canine osteosarcoma (OSA) cell lines (D22 and D17), and to evaluate the response of these cells to 17-AAG (17-N-allylamino-17-demethoxygeldanamycin) treatment in relation to tubular-like structure formation in vitro. Only D17 cell line formed hollow matrix channels in long-term 3D cultures and assumed endothelial morphology, with cells expressing both Hsp90 and VEGFR1, but lacking expression of endothelial marker CD31. 17-AAG treatment inhibited migration of D17 OSA cells, also decreasing VM markers in vitro and inducing a reduction of HIF1α transcript and protein in this cell line. Taken together, these preliminary data indicate that the biological effects of 17-AAG on D17 3D culture and on HIF1α regulation can provide interesting information to translate these findings from the basic research to clinical approach for the treatment of canine OSA as a model in comparative oncology.

The possible role of heat shock protein-70 induction in collagen-induced arthritis in rats

AIM

This study aimed to evaluate the possible role of heat shock protein-70 (HSP70) induction by 17-allylaminodemethoxygeldanamycin (17-AAG) in collagen-induced arthritis in rats.

MATERIAL AND METHODS

Male Wistar rats were divided into five groups (n = 10/group) and were treated intraperitoneally twice a week for 4 weeks, namely normal control (saline), arthritis control (AR; saline), AR + 17-AAG, AR + methotrexate (MTX), and AR + 17-AAG + MTX. At the end of the treatments, arthritic score was determined and then the animals were sacrificed. Erythrocyte sedimentation rate (ESR), serum levels of HSP70, interleukin-17 (IL-17), tumor necrosis factor-alpha (TNF-α), rheumatic factor (RF), C-reactive protein (CRP), malondialdehyde (MDA), glutathione peroxidase (GPx), and matrix metalloproteinase-9 (MMP-9) were determined.

RESULTS

In the AR group, all parameters increased significantly, except for GPx, which showed a pronounced decrease. The 17-AAG and/or MTX treatments significantly reduced arthritic score, ESR, IL-17, TNF-α, RF, CRP, MDA, and MMP-9 with significant increase in GPx compared to the AR group. The HSP70 level was significantly higher in the AR + 17-AAG and the AR + 17-AAG + MTX groups but significantly lower in the AR + MTX group as compared to the AR group. Also, it was significantly lower in the AR + MTX group as compared to the AR + 17-AAG group.

CONCLUSION

We concluded that HSP70 induction by 17-AAG attenuated the inflammatory process in a rheumatoid arthritis (RA) model induced by collagen, which suggested that HSP70 inducers can be promising agents in the treatment of RA.

HSP90 inhibitor 17-AAG prevents apoptosis of cardiomyocytes via miR-93-dependent mitigation of endoplasmic reticulum stress

Heart failure accounts for substantial morbidity and mortality worldwide. Accumulating evidence suggests that aberrant cardiac cell death caused by endoplasmic reticulum stress (ERS) is often associated with structural or functional cardiac abnormalities that lead to insufficient cardiac output. The detailed molecular mechanism underlying the pathological death of cardiomyocytes still remains poorly understood. We found that 17-AAG (tanespimycin), an HSP90 (heat shock protein 90) inhibitor often used to kill cancer cells, could potently inhibit tunicamycin-induced ERS and the downstream nuclear factor kappa B activity in neonatal rat cardiomyocytes, leading to diminished apoptotic signaling and thus enhanced cell survival. Interestingly, the antiapoptotic effect of 17-AAG on cardiomyocytes required normal expression of miR-93, an oncogenic microRNA known to promote cell survival and growth. Our study implicated a new pharmacological role of 17-AAG in supporting the miR-93-associated oncogenic signaling to prevent the pathological death of cardiomyocytes. The results opened opportunities for exploring new strategies in the development of therapeutic agents.

Gold nanoparticles loaded with cullin-5 DNA increase sensitivity to 17-AAG in cullin-5 deficient breast cancer cells

HSP90 inhibitors have the potential to treat many types of cancer due to the dependence of tumor cells on HSP90 for cell growth and proliferation. The Cullin-5 (Cul5) E3 ubiquitin ligase is required for HSP90 inhibitors to induce client protein degradation and subsequent cell death. Cul5 is expressed at low levels in breast cancer cells compared to patient matched controls. This observed low Cul5 expression may play a role in the reported decreased efficacy of 17-AAG and related HSP90 inhibitors as a monotherapy. We have developed a method for delivery of 17-AAG plus Cul5 DNA to cells via gold nanoparticles (AuNPs). Delivery of AuNPs containing Cul5 DNA increases the sensitivity of Cul5 deficient AU565 cells to 17-AAG. Characterization of AuNPs by UV-vis spectrum, TEM, gel electrophoresis assay and ¹H NMR indicate attachment of both 17-AAG and DNA payload as well as AuNP stability. Studies in Cul5 deficient AU565 cells reveal that delivery of Cul5 and 17-AAG together increase cytotoxicity. Our results provide evidence that delivery of DNA with drug may serve as a method to sensitize drug resistant tumor cells.

Anti-cancer effects of chemotherapeutic agent; 17-AAG, in combined with gold nanoparticles and irradiation in human colorectal cancer cells

OBJECTIVE

The present study evaluated the anti-cancer effects of irradiation (Ir) alone, Ir after heat shock protein 90 inhibitor; 17-allylamino-17-demethoxygeldanamycin (17-AAG) and gold nanoparticle (GNP) treatments in human colorectal cancer cell line (HCT-116), with the targeting of related mechanisms.

METHODS

Water-soluble tetrazolium salt-1 assay was utilized to study the cytotoxic effects of 17-AAG, GNP, Ir in single and combination cases on the cell viability of HCT-116 cells. The cells were examined with DNA fragmentation electrophoresis and evaluated for apoptosis induction. Caspase-3 expression as a critical apoptosis element in protein level was detected by western blotting.

RESULTS

Treatment with 17-AAG in a dose dependent manner for 24 h inhibited the cellular viability of HCT-116 cells. GNP at a dose of 70 μM had the lowest cytotoxic effects and was thus selected for combination treatment studies. Based on the results, GNP at a dose of 70 μM did not have a significant effect on cellular viability of HCT-116. In contrast, the evaluation of double and triple combinations, GNP with Ir (2 Gy of 6 MV X-ray radiation) and 17-AAG in double combinations induced significant cytotoxicity. Both DNA damage pattern and caspase-3 protein upregulation were present in Ir,GNP/17-AAG,GNP and Ir,17-AAG combinations compared to single treatments. Furthermore, in the three combination of GNP,Ir,17-AAG, radiosensitization effects (increased caspase-3 expression) occurred with a minimum concentration of 17-AAG.

CONCLUSION

According to the results of this study, 17-AAG as chemotherapeutic agent in combination with Ir and GNP exerts noticeable anti-cancer effects, inhibited cell viability, and increased apoptosis occurrence by upregulating caspase-3 expression. It is suggested that these combinations should be more evaluated as a promising candidate for colorectal cancer treatment. Graphical abstract Anti-cancer effects of chemotherapeutic agent; 17-AAG, in combined with gold nanoparticles and irradiation in human colorectal cancer cells.

Spotlight on 17-AAG as an Hsp90 inhibitor for molecular targeted cancer treatment

Hsp90 is a ubiquitous chaperone with important roles in the organization and maturation of client proteins that are involved in the progression and survival of cancer cells. Multiple oncogenic pathways can be affected by inhibition of Hsp90 function through degradation of its client proteins. That makes Hsp90 a therapeutic target for cancer treatment. 17-allylamino-17-demethoxy-geldanamycin (17-AAG) is a potent Hsp90 inhibitor that binds to Hsp90 and inhibits its chaperoning function, which results in the degradation of Hsp90's client proteins. There have been several preclinical studies of 17-AAG as a single agent or in combination with other anticancer agents for a wide range of human cancers. Data from various phases of clinical trials show that 17-AAG can be given safely at biologically active dosages with mild toxicity. Even though 17-AAG has suitable pharmacological potency, its low water solubility and high hepatotoxicity could significantly restrict its clinical use. Nanomaterials-based drug delivery carriers may overcome these drawbacks. In this paper, we review preclinical and clinical research on 17-AAG as a single agent and in combination with other anticancer agents. In addition, we highlight the potential of using nanocarriers and nanocombination therapy to improve therapeutic effects of 17-AAG.

Targeting the MYC Oncogene in Burkitt Lymphoma through HSP90 Inhibition

Overexpression of the MYC oncogene is a key feature of many human malignancies including Burkitt lymphoma. While MYC is widely regarded to be a promising therapeutic target, a clinically effective MYC inhibitor is still elusive. Here, we report an alternative strategy, targeting MYC indirectly through inhibition of the HSP90 machinery. We found that inhibition of HSP90 function reduces MYC expression in human Burkitt lymphoma through suppression of MYC transcription and destabilization of MYC protein, thereby diminishing the proliferation of tumor cells. Consistently, treatment of Burkitt lymphoma cell lines with HSP90 inhibitors (17-AAG or 17-DMAG) was accompanied by downregulation of canonical MYC target genes. Combination treatment with 17-DMAG and the proteasome inhibitor, MG-132, led to accumulation of MYC protein, indicating that upon HSP90 inhibition, MYC is degraded by the proteasome. Using co-immunoprecipitation, we furthermore demonstrated a direct interaction between MYC and HSP90, indicating that MYC is an HSP90 client protein in Burkitt lymphoma. Together, we report here the use of HSP90 inhibitors as an alternative approach to target the MYC oncogene and its network in Burkitt lymphoma.

Inhibition of Heat Shock Protein 90 by 17-AAG Reduces Inflammation via P2X7 Receptor/NLRP3 Inflammasome Pathway and Increases Neurogenesis After Subarachnoid Hemorrhage in Mice

Subarachnoid hemorrhage (SAH) is a life-threatening cerebrovascular disease that usually has a poor prognosis. Heat shock proteins (HSPs) have been implicated in the mechanisms of SAH-associated damage, including increased inflammation and reduced neurogenesis. The aim of this study was to investigate the effects of HSP90 inhibition on inflammation and neurogenesis in a mouse model of experimental SAH induced by endovascular surgery. Western blotting showed HSP90 levels to be decreased, while neurogenesis, evaluated by 5-bromo-2'-deoxyuridine (BrdU) immunohistochemistry, was decreased in the hippocampuses of SAH mice. SAH also induced pro-inflammatory factors such as interleukin-1β (IL-1β), capase-1 and the NLRP3 inflammasome. However, intraperitoneal administration of the specific HSP90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG) reduced the levels of HSP90, NLRP3, ASC, caspase-1 and IL-1β, while increasing the levels of brain-derived neurotrophic factor and doublecortin (DCX), as well as the number of BrdU-positive cells in SAH mice. In addition, 17-AGG improved short- and long-term neurobehavioral outcomes. The neuroprotective and anti-inflammatory effects of 17-AGG were reversed by recombinant HSP90 (rHSP90); this detrimental effect of HSP90 was inhibited by the specific P2X7 receptor (P2X7R) inhibitor A438079, indicating that SAH-induced inflammation and inhibition of neurogenesis were likely mediated by HSP90 and the P2X7R/NLRP3 inflammasome pathway. HSP90 inhibition by 17-AAG may be a promising therapeutic strategy for the treatment of SAH.

Encapsulation of the HSP-90 Chaperone Inhibitor 17-AAG in Stable Liposome Allow Increasing the Therapeutic Index as Assessed, in vitro, on Leishmania (L) amazonensis Amastigotes-Hosted in Mouse CBA Macrophages

The current long-term treatment for leishmaniasis causes severe side effects and resistance in some cases. An evaluation of the anti-leishmanial potential of an HSP90-inhibitor, 17-allylamino-17-demethoxygeldanamycin (17-AAG), demonstrated its potent effect against Leishmania spp. in vitro and in vivo. We have previously shown that 17-AAG can kill L. (L) amazonensis promastigotes with an IC₅₀ of 65 nM and intracellular amastigote at concentrations as low as 125 nM. As this compound presents low solubility and high toxicity in human clinical trials, we prepared an inclusion complex containing hydroxypropyl-β-cyclodextrin and 17-AAG (17-AAG:HPβCD) to improve its solubility. This complex was characterized by scanning electron microscopy, and X-ray diffraction. Liposomes-containing 17-AAG:HPβCD was prepared and evaluated for encapsulation efficiency (EE%), particle size, polydispersity index (PDI), pH, and zeta potential, before and after accelerated and long-term stability testing. An evaluation of leishmanicidal activity against promastigotes and intracellular amastigotes of L. (L) amazonensis was also performed. The characterization techniques utilized confirmed the formation of the inclusion complex, HPβCD:17-AAG, with a resulting 33-fold-enhancement in compound water solubility. Stability studies revealed that 17-AAG:HPβCD-loaded liposomes were smaller than 200 nm, with 99% EE. Stability testing detected no alterations in PDI that was 0.295, pH 7.63, and zeta potential +22.6, suggesting liposome stability, and suitability for evaluating leishmanicidal activity. Treatment of infected macrophages with 0.006 nM of 17-AAG:HPβCD or 17-AAG:HPβCD-loaded liposomes resulted in almost complete amastigote clearance inside macrophages after 48 h. This reduction is similar to the one observed in infected macrophages treated with 2 μM amphotericin B. Our results showed that nanotechnology and drug delivery systems could be used to increase the antileishmanial efficacy and potency of 17-AAG in vitro, while also resulting in reduced toxicity that indicates these formulations may represent a potential therapeutic strategy against leishmaniasis.

In vitro interactions between 17-AAG and azoles against Exophiala dermatitidis

BACKGROUND

Exophiala dermatitidis causes a variety of illnesses in humans which are always refractory to available treatment modalities. Hsp90 governs crucial stress responses, cell wall repair mechanisms and antifungal resistance in pathogenic fungi. Thus, targeting Hsp90 with specific inhibitors holds considerable promise as combination strategy.

OBJECTIVES

To investigate the antifungal effect of 17-AAG alone or combined with azoles against E. dermatitidis.

METHODS

In vitro interactions of 17-AAG, a Hsp90 inhibitor, and azoles including itraconazole, voriconazole and posaconazole against E. dermatitidis were evaluated via broth microdilution chequerboard technique, adapted from the CLSI M38-A2 method. A total of 18 clinical strains were studied. Candida parapsilosis (ATCC22019) was included to ensure quality control.

RESULTS AND CONCLUSIONS

17-AAG alone exhibited minimal antifungal activity against all tested isolates. However, synergistic effects between 17-AAG and posaconazole, itraconazole or voriconazole were observed against 15 (83.3%), 12 (66.7%) and 1 (5.6%) isolates of E. dermatitidis, respectively. The effective working ranges of 17-AAG in synergistic combinations were mostly within 2-8 μg/mL. No antagonism was observed. In conclusion, harnessing fungal Hsp90 with 17-AAG might prove a potential antifungal regimen for E. dermatitidis infections. However, due to the host toxicity of 17-AAG, more efforts are needed to develop fungal specific Hsp90 inhibitors.

Synergistic effects of rmhTRAIL and 17-AAG on the proliferation and apoptosis of multiple myeloma cells

OBJECTIVE

This study aimed to investigate synergistic effects of recombinant mutant human tumor necrosis factor-related apoptosis-inducing ligand (rmhTRAIL) and heat-shock protein 90 (HSP90) inhibitor (geldanamycin derivative 17 -allylamino- 17-demethoxy -geldanamycin, 17-AAG) on the proliferation and apoptosis of multiple myeloma (MM) cells.

METHODS

MTT assays evaluated inhibitory effects of rmhTRAIL and 17-AAG in different concentrations and treatment durations on the proliferation of RPMI8226 and U266 cells. The half maximal inhibitory concentration was calculated using OriginPro7.5. Synergistic effects of rmhTRAIL and 17-AAG on apoptosis of MM cells were detected using flow cytometry at 24 and 48 h post-treatment. To evaluate synergistic effects of rmhTRAIL and 17-AAG, the Q-value was calculated using King's formula.

RESULTS

rmhTRAIL exhibited significant inhibitory effects on the proliferation of RPMI8226 cells in a dose- and time-dependent manner (>50%), whereas U266 cells were not sensitive to rmhTRAIL (<50%). 17-AAG inhibited the proliferation of RPMI8226 and U266 cells in a dose-dependent manner (>80%). Significant synergistic effects of rmhTRAIL and 17-AAG on the proliferation of RPMI8226 cells were revealed (Q-value > 1.15), whereas synergistic effects were not evident on the proliferation of U266 cells (Q-value < 1.15). rmhTRAIL and 17-AAG exhibited significant synergistic effects on apoptosis of RPMI8226 and U266 cells (Q-value > 1.15).

CONCLUSION

The combined application of rmhTRAIL and 17-AAG revealed favorable synergistic effects in the treatment of MM.

Targeting the hypoxia pathway in malignant plasma cells by using 17-allylamino-17-demethoxygeldanamycin

Multiple myeloma (MM) is characterized as a clonal expansion of malignant plasma cells in the bone marrow, which is often associated with pancytopenia and osteolytic bone disease. Interestingly, myeloma-infiltrated bone marrow is considered to be hypoxic, providing selection pressure for a developing tumour. Since HSP90 was shown to participate in stabilization of the subunit of the key transcription factor HIF-1, which controls the hypoxic response, the aim of this study was to investigate the influence of a HSP90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG), on MM cells cultured under low oxygenation conditions. We confirmed that 17-AAG inhibits hypoxic induction of the HIF-1 target genes in malignant plasma cells and demonstrate the concentration range of severe hypoxia-specific cytotoxicity. Next, we selected the malignant plasma cells under severe hypoxia/re-oxygenation culture conditions in the presence or absence of 17-AAG and subsequently, the cells which survived were further expanded and analyzed. Interestingly, we have noticed significant changes in the survival and the response to anti-MM drugs between the parental cell lines and those selected in cyclic severe hypoxia in the presence and absence of 17-AAG. Importantly, we also observed that the lack of oxygen itself, irrespectively of HIF-1 inhibition, is the main/pivotal factor driving the selection process in the experiments presented here.

Small molecule inhibitor screening identifified HSP90 inhibitor 17-AAG as potential therapeutic agent for gallbladder cancer

Gallbladder cancer (GBC) is a lethal cancer with poor prognosis associated with high invasiveness and poor response to chemotherapy and radiotherapy. New therapeutic approaches are urgently needed in order to improve survival and response rates of GBC patients. We screened 130 small molecule inhibitors on a panel of seven GBC cell lines and identified the HSP90 inhibitor 17-AAG as one of the most potent inhibitory drugs across the different lines. We tested the antitumor efficacy of 17-AAG and geldanamycin (GA) in vitro and in a subcutaneous preclinical tumor model NOD-SCID mice. We also evaluated the expression of HSP90 by immunohistochemistry in human GBC tumors.In vitro assays showed that 17-AAG and GA significantly reduced the expression of HSP90 target proteins, including EGFR, AKT, phospho-AKT, Cyclin B1, phospho-ERK and Cyclin D1. These molecular changes were consistent with reduced cell viability and cell migration and promotion of G2/M cell cycle arrest and apoptosis observed in our in vitro studies.In vivo, 17-AAG showed efficacy in reducing subcutaneous tumors size, exhibiting a 69.6% reduction in tumor size in the treatment group compared to control mice (p < 0.05).The HSP90 immunohistochemical staining was seen in 182/209 cases of GBC (87%) and it was strongly expressed in 70 cases (33%), moderately in 58 cases (28%), and weakly in 54 cases (26%).Our pre-clinical observations strongly suggest that the inhibition of HSP90 function by HSP90 inhibitors is a promising therapeutic strategy for gallbladder cancer that may benefit from new HSP90 inhibitors currently in development.

Quiescence Promotes Latent HIV Infection and Resistance to Reactivation from Latency with Histone Deacetylase Inhibitors

Human immunodeficiency virus type 1 (HIV-1) establishes transcriptionally silent latent infections in resting memory T cells and hematopoietic stem and progenitor cells (HSPCs), which allows the virus to persist in infected individuals despite antiretroviral therapy. Developing in vitro models of HIV-1 latency that recapitulate the characteristics of latently infected cells in vivo is crucial to identifying and developing effective latency-reversing therapies. HSPCs exist in a quiescent state in vivo, and quiescence is correlated with latent infections in T cells. However, current models for culturing HSPCs and for infecting T cells in vitro require that the cells be maintained in an actively proliferating state. Here we describe a novel culture system in which primary human HSPCs cultured under hypothermic conditions are maintained in a quiescent state. We show that these quiescent HSPCs are susceptible to predominantly latent infection with HIV-1, while actively proliferating and differentiating HSPCs obtain predominantly active infections. Furthermore, we demonstrate that the most primitive quiescent HSPCs are more resistant to spontaneous reactivation from latency than more differentiated HSPCs and that quiescent HSPCs are resistant to reactivation by histone deacetylase inhibitors or P-TEFb activation but are susceptible to reactivation by protein kinase C (PKC) agonists. We also demonstrate that inhibition of HSP90, a known regulator of HIV transcription, recapitulates the quiescence and latency phenotypes of hypothermia, suggesting that hypothermia and HSP90 inhibition may regulate these processes by similar mechanisms. In summary, these studies describe a novel model for studying HIV-1 latency in human primary cells maintained in a quiescent state.IMPORTANCE Human immunodeficiency virus type 1 (HIV-1) establishes a persistent infection for which there remains no feasible cure. Current approaches are unable to clear the virus despite decades of therapy due to the existence of latent reservoirs of integrated HIV-1, which can reactivate and contribute to viral rebound following treatment interruption. Previous clinical attempts to reactivate the latent reservoirs in an individual so that they can be eliminated by the immune response or viral cytopathic effect have failed, indicating the need for a better understanding of the processes regulating HIV-1 latency. Here we characterize a novel in vitro model of HIV-1 latency in primary hematopoietic stem and progenitor cells isolated from human cord blood that may better recapitulate the behavior of latently infected cells in vivo This model can be used to study mechanisms regulating latency and potential therapeutic approaches to reactivate latent infections in quiescent cells.

Transcriptional regulation of Runx2 by HSP90 controls osteosarcoma apoptosis via the AKT/GSK-3β/β-catenin signaling

Osteosarcoma (OS) is the most malignant primary bone tumor in children and adolescents with limited treatment options and poor prognosis. Recently, aberrant expression of Runx2 has been found in OS, thereby contributing to the development, and progression of OS. However, the upstream signaling molecules that regulate its expression in OS remain largely unknown. In the present study, we first confirmed that the inhibition of HSP90 with 17-AAG caused significant apoptosis of OS cells via a caspase-3-dependent mechanism, and that inhibition or knockdown of HSP90 by 17-AAG or siRNAs significantly suppressed mRNA and protein expression of Runx2. Furthermore, we provided evidence that Runx2 was transcriptionally regulated by HSP90 when using MG132 and CHX chase assay. We also demonstrated that β-catenin was overexpressed in OS tissue, and that knockdown of β-catenin induced pronounced apoptosis of OS cells in the presence or absence of 17-AAG. Interestingly, this phenomenon was accompanied with a significant reduction of Runx2 and Cyclin D1 expression, indicating an essential role of Runx2/Cyclin D1 in 17-AAG-induced cells apoptosis. Moreover, we demonstrated that the apoptosis of OS cells induced by 17-AAG did require the involvement of the AKT/GSK-3β/β-catenin signaling pathway by using pharmacological inhibitor GSK-3β (LiCl) or siGSK-3β. Our findings reveal a novel mechanism that Runx2 is transcriptionally regulated by HSP90 via the AKT/GSK-3β/β-catenin signaling pathway, and by which leads to apoptosis of OS cells.

Hsp90α regulates ATM and NBN functions in sensing and repair of DNA double-strand breaks

The molecular chaperone heat shock protein 90 (Hsp90α) regulates cell proteostasis and mitigates the harmful effects of endogenous and exogenous stressors on the proteome. Indeed, the inhibition of Hsp90α ATPase activity affects the cellular response to ionizing radiation (IR). Although the interplay between Hsp90α and several DNA damage response (DDR) proteins has been reported, its role in the DDR is still unclear. Here, we show that ataxia-telangiectasia-mutated kinase (ATM) and nibrin (NBN), but not 53BP1, RAD50, and MRE11, are Hsp90α clients as the Hsp90α inhibitor 17-(allylamino)-17-demethoxygeldanamycin (17-AAG) induces ATM and NBN polyubiquitination and proteosomal degradation in normal fibroblasts and lymphoblastoid cell lines. Hsp90α-ATM and Hsp90α-NBN complexes are present in unstressed and irradiated cells, allowing the maintenance of ATM and NBN stability that is required for the MRE11/RAD50/NBN complex-dependent ATM activation and the ATM-dependent phosphorylation of both NBN and Hsp90α in response to IR-induced DNA double-strand breaks (DSBs). Hsp90α forms a complex also with ph-Ser1981-ATM following IR. Upon phosphorylation, NBN dissociates from Hsp90α and translocates at the DSBs, while phThr5/7-Hsp90α is not recruited at the damaged sites. The inhibition of Hsp90α affects nuclear localization of MRE11 and RAD50, impairs DDR signaling (e.g., BRCA1 and CHK2 phosphorylation), and slows down DSBs repair. Hsp90α inhibition does not affect DNA-dependent protein kinase (DNA-PK) activity, which possibly phosphorylates Hsp90α and H2AX after IR. Notably, Hsp90α inhibition causes H2AX phosphorylation in proliferating cells, this possibly indicating replication stress events. Overall, present data shed light on the regulatory role of Hsp90α on the DDR, controlling ATM and NBN stability and influencing the DSBs signaling and repair.

Apoptosis of colon cancer cells under the effect of geldanamycin derivate

AIM

The apoptotic effect of geldanamycin derivative may be important for the colorectal cancer therapy. The mechanisms of apoptosis require understanding of the behavior of colon cancer cell line Colo-205 which mimics colon adenocarcinoma. Therefore, the effect of IC50 dose of 17-allylamino-17-demethoxygeldanamycin (17-AAG) on the colon cancer cells in vitro was studied for its anti-apoptotic activity.

METHOD

Apoptotic ratio of the Colo-205 cells was determined after 17-AAG application with terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining and apoptosis related genes. Apoptosis signal path related key mitochondrial proteins, cytochrome c, bcl-2, caspase 9 and Apaf-1 expression were examined with RT-PCR method.

RESULTS

17-AAG caused induction of cell death. Apoptotic related genes such as cytochrome-c, Apaf-1 and caspase-9 protein expressions were increased significantly (p < 0.05) and anti-apoptotic bcl-2 expression was decreased significantly (p < 0.05). Our results indicated that the application of 17-AAG on Colo-205 cells showed anticancer effect by the apoptosis due to alteration of apoptotic genes.

CONCLUSION

The apoptotic effect of 17-AAG as an natural product for alternative medicine would be very important for the success and quality of life during the treatment of colon carcinoma with the combination of anticancer drugs (Tab. 1, Fig. 2, Ref. 32).

Heat-shock protein 90 (Hsp90) promotes opioid-induced anti-nociception by an ERK mitogen-activated protein kinase (MAPK) mechanism in mouse brain

Recent advances in developing opioid treatments for pain with reduced side effects have focused on the signaling cascades of the μ-opioid receptor (MOR). However, few such signaling targets have been identified for exploitation. To address this need, we explored the role of heat-shock protein 90 (Hsp90) in opioid-induced MOR signaling and pain, which has only been studied in four previous articles. First, in four cell models of MOR signaling, we found that Hsp90 inhibition for 24 h with the inhibitor 17-N-allylamino-17-demethoxygeldanamycin (17-AAG) had different effects on protein expression and opioid signaling in each line, suggesting that cell models may not be reliable for predicting pharmacology with this protein. We thus developed an in vivo model using CD-1 mice with an intracerebroventricular injection of 17-AAG for 24 h. We found that Hsp90 inhibition strongly blocked morphine-induced anti-nociception in models of post-surgical and HIV neuropathic pain but only slightly blocked anti-nociception in a naive tail-flick model, while enhancing morphine-induced precipitated withdrawal. Seeking a mechanism for these changes, we found that Hsp90 inhibition blocks ERK MAPK activation in the periaqueductal gray and caudal brain stem. We tested these signaling changes by inhibiting ERK in the above-mentioned pain models and found that ERK inhibition could account for all of the changes in anti-nociception induced by Hsp90 inhibition. Taken together, these findings suggest that Hsp90 promotes opioid-induced anti-nociception by an ERK mechanism in mouse brain and that Hsp90 could be a future target for improving the therapeutic index of opioid drugs.

Histone deacetylase activity mediates acquired resistance towards structurally diverse HSP90 inhibitors

Heat shock protein 90 (HSP90) regulates multiple signalling pathways critical for tumour growth. As such, HSP90 inhibitors have been shown to act as effective anticancer agents in preclinical studies but, for a number of reasons, the same effect has not been observed in the clinical trials to date. One potential reason for this may be the presence of de novo or acquired resistance within the tumours. To investigate mechanisms of resistance, we generated resistant cell lines through gradual dose escalation of the HSP90 inhibitor 17‐allylamino‐17‐demethoxygeldanamycin (17‐AAG). The resultant resistant cell lines maintained their respective levels of resistance (7–240×) in the absence of 17‐AAG and were also cross‐resistant with other benzoquinone ansamycin HSP90 inhibitors. Expression of members of the histone deacetylase family (HDAC 1, 5, 6) was altered in the resistant cells. To determine whether HDAC activity contributed to resistance, pan‐HDAC inhibitors (TSA and LBH589) and the class II HDAC‐specific inhibitor SNDX275 were found to resensitize resistant cells towards 17‐AAG and 17‐dimethylaminoethylamino‐17‐demethoxygeldanamycin. Most significantly, resistant cells were also identified as cross‐resistant towards structurally distinct HSP90 inhibitors such as radicicol and the second‐generation HSP90 inhibitors CCT018159, VER50589 and AUY922. HDAC inhibition also resensitized resistant cells towards these classes of HSP90 inhibitors. In conclusion, we report that prolonged 17‐AAG treatment results in acquired resistance of cancer cells towards not just 17‐AAG but also to a spectrum of structurally distinct HSP90 inhibitors. This acquired resistance can be inhibited using clinically relevant HDAC inhibitors. This work supports the potential benefit of using HSP90 and HDAC inhibitors in combination within the clinical setting.

Regulation of Viral Replication, Apoptosis and Pro-Inflammatory Responses by 17-AAG during Chikungunya Virus Infection in Macrophages

Chikungunya virus (CHIKV) infection has re-emerged as a major public health concern due to its recent worldwide epidemics and lack of control measures. Although CHIKV is known to infect macrophages, regulation of CHIKV replication, apoptosis and immune responses towards macrophages are not well understood. Accordingly, the Raw264.7 cells, a mouse macrophage cell line, were infected with CHIKV and viral replication as well as new viral progeny release was assessed by flow cytometry and plaque assay, respectively. Moreover, host immune modulation and apoptosis were studied through flow cytometry, Western blot and ELISA. Our current findings suggest that expression of CHIKV proteins were maximum at 8 hpi and the release of new viral progenies were remarkably increased around 12 hpi. The induction of Annexin V binding, cleaved caspase-3, cleaved caspase-9 and cleaved caspase-8 in CHIKV infected macrophages suggests activation of apoptosis through both intrinsic and extrinsic pathways. The pro-inflammatory mediators (TNF and IL-6) MHC-I/II and B7.2 (CD86) were also up-regulated during infection over time. Further, 17-AAG, a potential HSP90 inhibitor, was found to regulate CHIKV infection, apoptosis and pro-inflammatory cytokine/chemokine productions of host macrophages significantly. Hence, the present findings might bring new insight into the therapeutic implication in CHIKV disease biology.

Cytotoxic effects of the newly-developed chemotherapeutic agents 17-AAG in combination with oxaliplatin and capecitabine in colorectal cancer cell lines

The use of heat shock protein 90 inhibitors like 17-allylamino-17-demethoxy-geldanamycin (17-AAG) has been recently introduced as an attractive anticancer therapy. It has been shown that 17-AAG may potentiate the inhibitory effects of some classical anticolorectal cancer (CRC) agents. In this study, two panels of colorectal carcinoma cell lines were used to evaluate the effects of 17-AAG in combination with capecitabine and oxaliplatin as double and triple combination therapies on the proliferation of CRC cell lines. HT-29 and all HCT-116 cell lines were seeded in culture media in the presence of different doses of the mentioned drugs in single, double, and triple combinations. Water-soluble tetrazolium-1 (WST-1) assay was used to investigate cell proliferation 24 h after treatments. Then, dose-response curves were plotted using WST-1outputs, and IC₅₀ values were determined. For double and triple combinations respectively 0.5 × IC₅₀ and 0.25 × IC₅₀ were used. Data was analyzed with the software CompuSyn. Drug interactions were analyzed using Chou-Talalay method to calculate the combination index (CI).The data revealed that 17-AAG shows a potent synergistic interaction (CI < 1) with oxaliplatin and capecitabine in double combinations (0.5 × IC₅₀) in both cell lines. In the case of triple combinations, the findings showed an antagonistic interaction (CI > 1) in HT-29 and a synergistic effect (CI < 1) in HCT-116 (0.25 × IC₅₀) cell lines. It was concluded that double combinations of 17-AAG with oxaliplatin or capecitabine might be effective against HCT-116 and HT-29 cell lines. However, in triple combinations, positive results were seen only against HCT-116. Further investigation is suggested to confirm the effectiveness of these combinations in clinical trials.

17-AAG and Apoptosis, Autophagy, and Mitophagy in Canine Osteosarcoma Cell Lines

Canine osteosarcoma is highly resistant to current chemotherapy; thus, clarifying the mechanisms of tumor cell resistance to treatments is an urgent need. We tested the geldanamycin derivative 17-AAG (17-allylamino-17-demethoxygeldanamycin) prototype of Hsp90 (heat shock protein 90) inhibitors in 2 canine osteosarcoma cell lines, D22 and D17, derived from primary and metastatic tumors, respectively. With the aim to understand the interplay between cell death, autophagy, and mitophagy, in light of the dual effect of autophagy in regulating cancer cell viability and death, D22 and D17 cells were treated with different concentrations of 17-AAG (0.5 μM, 1 μM) for 24 and 48 hours. 17-AAG-induced apoptosis, necrosis, autophagy, and mitophagy were assessed by transmission electron microscopy, flow cytometry, and immunofluorescence. A simultaneous increase in apoptosis, autophagy, and mitophagy was observed only in the D22 cell line, while D17 cells showed low levels of apoptotic cell death. These results reveal differential cell response to drug-induced stress depending on tumor cell type. Therefore, pharmacological treatments based on proapoptotic chemotherapy in association with autophagy regulators would benefit from a predictive in vitro screening of the target cell type.

The novel HSP90 inhibitor AT13387 potentiates radiation effects in squamous cell carcinoma and adenocarcinoma cells

Overexpression of heat shock protein 90 (HSP90) is associated with increased tumor cell survival and radioresistance. In this study we explored the efficacy of the novel HSP90 inhibitor AT13387 and examined its radiosensitizing effects in combination with gamma-radiation in 2D and 3D structures as well as mice-xenografts. AT13387 induced effective cytotoxic activity and radiosensitized cancer cells in monolayer and tumor spheroid models, where low drug doses triggered significant synergistic effects on cell survival together with radiation. Furthermore, AT13387 treatment resulted in G2/M-phase arrest and significantly reduced the migration capacity. The expression of selected client proteins involved in DNA repair, cell-signaling and cell growth was downregulated in vitro, though the expression of most investigated proteins recurred after 8–24 h. These results were confirmed in vivo where AT13387 treated tumors displayed effective downregulation of HSP90 and its oncogenic client proteins.

In conclusion, our results demonstrate that AT13387 is a potent new cancer drug and effective radiosensitizer in vitro with an excellent in vivo efficacy. AT13387 treatment has the potential to improve external beam therapy and radionuclide therapy outcomes and restore treatment efficacy in cancers that are resistant to initial therapeutic regimes.

17AAG-induced internalisation of HER2-specific Affibody molecules

The geldanamycin derivative 17-allylamino-17-demethoxygeldanamycin (17-AAG) is known to induce internalisation and degradation of the otherwise internalisation-resistant human epidermal growth factor receptor 2 (HER2) receptor. In the present study, 17-AAG was used to increase internalisation of the HER2-specific Affibody molecule ABY-025. The cellular redistribution of halogen-labelled ²¹¹At-ABY-025 and radiometal-labelled ¹¹¹In-ABY-025 following treatment with 17-AAG was studied. 17-AAG treatment of SKOV-3 human ovarian carcinoma and SKBR-3 human breast carcinoma cells to some extent shifted the localisation of ¹¹¹In-ABY-025 from the cell surface to intracellular compartments in the two cell lines. ABY-025 labelled with the high-linear energy transfer α emitter ²¹¹At was also internalised to a higher degree; however, due to its physiological properties, this nuclide was excreted faster. The results indicate that 17-AAG may be used to facilitate cell-specific intracellular localisation of a suitable cytotoxic or radioactive agent coupled to ABY-025 in HER2-overexpressing cells.

PI3K-independent mTOR activation promotes lapatinib resistance and IAP expression that can be effectively reversed by mTOR and Hsp90 inhibition

Although HER2 targeted therapies have substantially improved outcomes in HER2 overexpressing (HER2+) breast cancer, resistance to these therapies remains a clinical challenge. To better understand the mechanisms of resistance to lapatinib, a HER2 and EGFR dual kinase inhibitor, we treated HER2+ breast cancer cells with lapatinib for an extended period to generate a lapatinib-resistant (LapR) cell line model and examined cancer-promoting signaling activation in LapR cells. We found that LapR cells possess enhanced mTOR activation, which was independent of PI3K and other known mTOR activators. Lapatinib resistance could be reversed by mTOR kinase inhibition. Intriguingly, LapR cells had constitutive cytosolic cytochrome C, indicating that LapR cells suppress lapatinib-induced apoptosis downstream of cytochrome C release from mitochondria into the cytosol rather than by preventing its release into the cytosol. Consistent with this notion, LapR cells possessed increased levels of 2 of the inhibitors of apoptosis (IAPs), survivin and c-IAP-2, which are reported to block caspase activation downstream of cytosolic cytochrome C release. Further, treatment with the mTOR kinase inhibitor AZD8055 or the Hsp90 inhibitor 17-AAG reversed expression of IAPs and overcame lapatinib resistance in LapR cells. Together, these data suggest that suppression of apoptosis downstream of cytosolic cytochrome C release, possibly through increased expression of IAPs or other caspase-suppressing proteins, may promote lapatinib resistance. Further, PI3K is thought to be the main driver of lapatinib resistance, but our findings indicate that PI3K inhibitors may be ineffective in some lapatinib-resistant HER2+ breast cancers with PI3K-independent activation of mTOR kinase, which may instead benefit from mTOR or Hsp90 inhibitors.

Inhibition of heat-shock protein 90 sensitizes liver cancer stem-like cells to magnetic hyperthermia and enhances anti-tumor effect on hepatocellular carcinoma-burdened nude mice

PURPOSE

To explore the thermoresistance and expression of heat-shock protein 90 (HSP90) in magnetic hyperthermia-treated human liver cancer stem-like cells (LCSCs) and the effects of a heat-shock protein HSP90 inhibitor 17-allylamino-17-demethoxgeldanamycin (17-AAG) on hepatocellular carcinoma-burdened nude mice.

METHODS

CD90(+) LCSCs were isolated by magnetic-activated cell sorting from BEL-7404. Spheroid formation, proliferation, differentiation, drug resistance, and tumor formation assays were performed to identify stem cell characteristics. CD90-targeted thermosensitive magnetoliposomes (TMs)-encapsulated 17-AAG (CD90@17-AAG/TMs) was prepared by reverse-phase evaporation and its characteristics were studied. Heat tolerance in CD90(+) LCSCs and the effect of CD90@17-AAG/TMs-mediated heat sensitivity were examined in vitro and in vivo.

RESULTS

CD90(+) LCSCs showed significant stem cell-like properties. The 17-AAG/TMs were successfully prepared and were spherical in shape with an average size of 128.9±7.7 nm. When exposed to magnetic hyperthermia, HSP90 was up-regulated in CD90(+) LCSCs. CD90@17-AAG/TMs inhibited the activity of HSP90 and increased the sensitivity of CD90(+) LCSCs to magnetic hyperthermia.

CONCLUSION

The inhibition of HSP90 could sensitize CD90(+) LCSCs to magnetic hyperthermia and enhance its anti-tumor effects in vitro and in vivo.

Heat Shock Protein 90 (Hsp90) as a Molecular Target for the Development of Novel Drugs Against the Dermatophyte Trichophyton rubrum

Treatment of fungal infections is difficult due to several reasons, such as side effects of drugs, emergence of resistant strains, and limited number of molecular targets for the drug compounds. In fungi, heat shock proteins (Hsps) have been implicated in several processes with the conserved molecular chaperone Hsp90 emerging as a potential target for antifungal therapy. It plays key cellular roles by eliciting molecular response to environmental changes, morphogenesis, antifungal resistance, and fungal pathogenicity. Here, we evaluated the transcription profiles of hsp genes of the most prevalent dermatophyte Trichophyton rubrum in response to different environmental challenges including nutrient availability, interaction with cells and molecules of the host tissue, and drug exposure. The results suggest that each Hsp responds to a specific stress condition and that the cohort of Hsps facilitates fungal survival under various environmental challenges. Chemical inhibition of Hsp90 resulted in increased susceptibility of the fungus to itraconazole and micafungin, and decreased its growth in human nails in vitro. Moreover, some hsp and related genes were modulated by Hsp90 at the transcriptional level. We are suggesting a role of Hsp90 in the pathogenicity and drug susceptibility of T. rubrum as well as the regulation of other Hsps. The synergism observed between the inhibition of Hsp90 and the effect of itraconazole or micafungin in reducing the fungal growth is of great interest as a novel and potential strategy to treat dermatophytoses.