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The rational installation of pharmacophores targeting HSP90 and LSD1 axes has achieved significant anti-cancer capacity in prostate and colorectal cancer. Among the series of hybrids, inhibitor 6 exhibited remarkable anti-proliferative activity against prostate cancer cell lines PC-3 and DU145, with GI 50 values of 0.24 and 0.30 μM, respectively. It demonstrated notable efficacy in combinatorial attack and cell death initiation towards apoptosis. The cell death process was mediated by PARP induction and γH2AX signaling, and was also characterized as caspase-dependent and Bcl-xL/Bax-independent. Notably, no difference in eye size or morphology was observed in the zebrafish treated with compound 6 compared to the reference group (AUY922). The profound treatment response in docetaxel-resistant PC-3 cells highlighted the dual inhibitory ability in improving docetaxel sensitivity. Additionally, at a minimum concentration of 1.25 μM, compound 6 effectively inhibited the growth of patient-derived colorectal cancer (CRC) organoids for up to 10 days in vitro. Together, the designed HSP90/LSD1 inhibitors present a novel route and significant clinical value for anti-cancer drug therapy., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Jing-Ping Liou reports financial support was provided by National Science and Technology, Taiwan. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Masson SAS.)

The correction of protein folding is fundamental for cellular functionality and its failure can lead to severe diseases. In this context, molecular chaperones are crucial players involved in the tricky process of assisting in protein folding, stabilization, and degradation. Chaperones, such as heat shock proteins (HSP) 90, 70, and 60, operate within complex systems, interacting with co-chaperones both to prevent protein misfolding and direct to the correct folding. Chaperone targeting drugs could represent a challenging approach for the treatment of cystic fibrosis (CF), an autosomal recessive genetic disease caused by mutations in the CFTR gene, encoding for the CFTR chloride channel. In this review, we discuss the potential role of molecular chaperones as proteostasis modulators affecting CFTR biogenesis. In particular, we focused on HSP90 and HSP70, for their key role in CFTR folding and trafficking, as well as on HSP60 for its involvement in the inflammation process., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.)

Heat shock protein 90 (Hsp90), a molecular chaperone, contributes to the preservation of folding, structure, stability, and function proteins. In this study, novel compounds comprising isoxazole structure were designed, synthesized and their potential ability as Hsp90 inhibitors was validated through docking studies. The active site-based compounds were prepared through a multi-step synthesis process and their chemical structures were characterized employing FT-IR, NMR, and mass spectrometry analysis. Cytotoxic and Hsp90 inhibition activities of synthesized compounds were assessed by MTT assay and ELISA kit, respectively. Based on the obtained results, compound 5 exhibited the highest cytotoxicity (IC 50 ; 14 µM) against cancer cells and reduced Hsp90 expression from 5.54 ng/mL in untreated (normal cells) to 1.56 ng/mL in cancer cells. Moreover, molecular dynamics (MD) simulation results indicated its high affinity to target protein and approved its excellent stability which is essential for exerting an inhibitory effect on cancer cell proliferation., Competing Interests: Declarations Competing interests The authors declare no competing interests. Institutional review board statement The project was found to be in accordance to the ethical principle and national norms and standards for conducting medical research in Iran (Approval ID IR.MUI.RESEARCH.REC.1398.425 and Approval date 2019-11-02)., (© 2024. The Author(s).)

The central role of the chaperome in maintaining cellular proteostasis has seen numerous viral families evolve to parasitically exploit host chaperones in their life cycle. The HSP90 chaperone protein and its cochaperone Hop have both individually been shown to be essential factors for Kaposi sarcoma-associated herpesvirus (KSHV) lytic replication. Given the fundamental regulatory role that protein-protein interactions (PPIs) play in cellular biology, we reasoned that disrupting the Hop-HSP90 PPI may provide a new host-based target for inhibiting KSHV lytic replication. This study expands upon a previous report of non-natural peptides, which were found to disrupt the association between the Hop TPR2A domain and its interacting HSP90 CTD . Here, in addition to providing insight into the structure-activity relationships of PPI inhibition, we show disruption of the full-length Hop-HSP90 PPI. The inhibitory peptides selectively engaged the Hop TPR2A domain in cell lysates and when tethered to a cell-penetrating peptide acted as noncytotoxic inhibitors of KSHV lytic replication by lowering the viral load, preventing the production of infectious virions, and reducing the expression of KSHV lytic genes. In addition to tentative evidence of Hop-HSP90 PPI as a much-needed target for KSHV drug discovery, this study represents an important step in understanding viral interactions with the host proteostasis machinery.

Heat shock protein 90 alpha (Hsp90α) is an abundantly expressed and evolutionarily conserved molecular chaperone. Hsp90α is the inducible Hsp90 isoform, and its expression and secretion extracellularly (eHsp90α) can be triggered in response to a variety of cellular stresses to protect/activate client proteins and to facilitate cellular adjustment to the stress. As a result, cancers often have high expression levels of intracellular and extracellular (plasma) Hsp90α, allowing them to support their oncogenesis and progression. In fact, (e)Hsp90α has been implicated in regulating processes such as cell signaling transduction, DNA repair, promotion of the Epithelial-to-Mesenchymal Transition (EMT), promotion of angiogenesis, immune response, and cell migration. Hsp90α levels have been correlated with cancer progression and severity in several cancers, indicating that it may be a useful biomarker or drug-target for cancer. To date, the development of intracellular Hsp90α-targeted therapies include standard N-terminal ATP-competitive inhibitors and allosteric regulators that bind to Hsp90α's middle or C-terminal domain. On-target toxicities and dosing complications as a result of Hsp90α inhibition has driven the development of eHsp90α-targeted therapies. Examples include anti-Hsp90α monoclonal antibodies and cell-impermeable Hsp90α small molecule inhibitors. This review aims to discuss the many roles Hsp90α plays in cancer progression with a focus on the current development of Hsp90α-targeted therapies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.)

Lytic induction therapy was devised to selectively combat malignancies associated with Epstein-Barr virus (EBV) by triggering viral reactivation from latency. At present, the major challenges of lytic induction therapy are to maximize reactivating efficiencies and meanwhile minimize infectious virion production. C210, a novel curcumin derivative with potent Hsp90 inhibitory activity, was explored for EBV-reactivating and virion-producing effects in EBV-positive nasopharyngeal carcinoma (NPC) and gastric carcinoma (GC) cell lines. And the molecular mechanisms underlying these effects were determined. Follow C210 treatment, EBV lytic RNAs and proteins were upregulated, but infectious virions were not produced. Knockdown of heat shock protein 90 (Hsp90) induced expression of lytic RNAs and proteins, and diminished C210-driven EBV lytic induction. Pretreatment with an X box binding protein 1 (XBP1) inhibitor reduced C210-induced EBV lytic RNA. Furthermore, we demonstrated that C210 inhibited the binding of Hsp90 with its clients, signal transducer and activator of transcription 3 (STAT3) and xeroderma pigmentosum group B-complementing protein (XPB), which subsequently promoted their proteasomal degradation. Degradation of STAT3 by C210 enhanced the EBV-reactivating and anticancer capacity of suberoylanilide hydroxamic acid (SAHA). Depletion of XPB blocked SAHA-induced expression of late viral genes and production of infectious virions. These results elucidate a novel Hsp90 inhibitor targeting EBV lytic phase and extend the research on lytic induction strategy, which may offer reference value in the treatment of EBV-positive malignancies., (© 2024. The Author(s).)

Five active compounds, daidzein, luteolin, alpinumisoflavone (AI), 6,8-diprenylgenistein (DG), and warangalone (WA), were identified from the fruits of Maclura tricuspidata via LC-Q/TOF-MS. WA and DG were shown to reverse the high glucose (HG)-induced injury in human umbilical vein endothelial cells (HUVECs), indicating their potential protective effects in alleviating diabetic symptoms. Network pharmacology was conducted to reveal the potential mechanisms of action of the compounds, and Hsp90α (degree: 47), Src (degree: 49), Akt (degree: 69) and p53 (degree: 60) were shown as the core targets related to antidiabetic properties. Further experimental verification suggested that the compounds could enhance phosphorylation of Src and Akt, increase p53 expression act as Hsp90 inhibitors, and protect against HG induced endothelial dysfunction. Our findings will provide a comprehensive understanding of the active substances of M. tricuspidata , which will be helpful for their utilisation.

Geldanamycin remains a driver in the medicinal chemistry of heat shock protein 90 (Hsp90) inhibition, even half a century after its original isolation from nature. This Perspective focuses on the properties of the benzoquinone ring of the natural product that enable a range of functionalization reactions to take place. Therefore, inherent reactivity at C-17, where the methoxy group serves as a vinylogous ester, and at C-19 that demonstrates nucleophilic, enamide-type character toward electrophiles, and also as a conjugate acceptor to react with nucleophiles, has facilitated the synthesis of semisynthetic derivatives. Thus, a range of C-17-substituted amine derivatives has been investigated in oncology applications, with a number of compounds in this series reaching clinical trials. In contrast, the 19-position of geldanamycin has received less attention, although 19-substituted derivatives offer promise with markedly reduced toxicity compared to geldanamycin itself, while retaining Hsp90 inhibitory activity albeit with diminished potency in cellular studies.

Geldanamycin, an ansa -macrolide composed of a rigid benzoquinone ring and an aliphatic ansa -bridge, was isolated from Streptomyces hygroscopicus . Geldanamycin is a potent heat shock protein inhibitor with remarkable antiproliferative activity. However, it shows pronounced hepatotoxicity in animal models and unfavorable pharmacokinetic properties. Four geldanamycin analogs have progressed through various phases of clinical trials, but none have yet completed clinical evaluation or received FDA approval. To enhance the efficacy of these Hsp90 inhibitors, strategies such as prodrug approaches or nanocarrier delivery systems could be employed to minimize systemic and organ toxicity. Furthermore, exploring new drug combinations may help overcome resistance, potentially improving therapeutic outcomes. This review discusses the mechanism of action of geldanamycin, its pharmacokinetic properties, and the various approaches employed to alleviate its toxicity and maximize its clinical efficacy. The main focus is on those derivatives that have progressed to clinical trials or that have shown important in vivo activity in preclinical models.

Heat shock protein 90 (Hsp90) is a promising target for cancer therapy and imaging. Accurate detection of Hsp90 levels in tumors via noninvasive PET imaging might be beneficial for management. To achieve this, the precursor compound Dimer-Sansalvamide A (Dimer-San A) was PEGylated and modified by conjugating it with the bifunctional chelator 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA). The 18 F-labeled PEGylated Dimer-SanA decapeptide ( 18 F-PEGylated San A) was completed within 30 min using a two-step process. In vitro stability and specificity were assessed, including competition studies with the Hsp90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG). MicroPET imaging was performed on PL45 tumor-bearing mice to evaluate probe accumulation and tumor-to-muscle ratios. Biodistribution studies determined the route of excretion. The probe resulted in a radiochemical yield of 23.11% with a purity exceeding 95%. In vitro , 18 F-PEGylated San A exhibited high stability and selectively accumulated in Hsp90-positive PL45 cells, with binding effectively blocked by the Hsp90 inhibitor 17AAG, confirming its specificity. MicroPET imaging of PL45 tumor-bearing mice showed significant probe accumulation in tumor tissues at 1 and 2 h postinjection (4.06 ± 0.30 and 3.72 ± 0.61%ID/g, respectively), with optimal tumor-to-muscle ratios observed at 2 h postinjection (6.09 ± 1.92). While 18 F-PEGylated San A demonstrates enhanced water solubility, as indicated by increased kidney uptake relative to liver accumulation. The study successfully incorporated PEG units to create the novel probe 18 F-PEGylated San A targeting to Hsp90 without affecting its targeting capability, aimed at improving the pharmacokinetics and PET imaging of Hsp90 expression noninvasively.

A series of indazole analogs, derived from the B,C-ring-truncated scaffold of deguelin, were designed to function as C-terminal inhibitors of heat shock protein 90 (HSP90) and investigated as novel antitumor agents against HER2-positive breast cancer. Among the synthesized compounds, compound 12d exhibited substantial inhibitory effects in trastuzumab-sensitive (BT474) and trastuzumab-resistant (JIMT-1) breast cancer cells, with IC 50 values of 6.86 and 4.42 μM, respectively. Notably, compound 12d exhibited no cytotoxicity in normal cells. Compound 12d markedly downregulated the expression of the major HSP90 client proteins in both cell types, attributing its cytotoxicity to the destabilization and inactivation of HSP90 client proteins. Molecular docking studies using the homology model of an HSP90 homodimer demonstrated that inhibitor 12d fit nicely into the C-terminal domain, boasting a higher electrostatic complementary score than ATP. In vivo pharmacokinetic study indicated the high oral bioavailability of compound 12 d at F = 66.9 %, while toxicological studies indicated its negligible impact on hERG channels and CYP isozymes. Genotoxicity tests further confirmed its safety profile. The findings collectively position compound 12d as a promising candidate for further development as an antitumor agent against HER2-positive breast cancer., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.)

Colorectal cancer (CRC) has been becoming one of the most common causes of cancer mortality worldwide. Accumulating studies suggest that the progressive up-regulation of Wnt/β-catenin signaling is a crucial hallmark of CRC, and suppressing it is a promising strategy to treat CRC. Herein, we reported our latest efforts in the discovery of novel fused tetrahydroisoquinoline derivatives with good anti-CRC activities by screening our in-house berberine-like library and further structure-activity relationship (SAR) studies, in which we identified compound 10 is a potent lead compound with significant antiproliferation potencies. By the biotinylated probe and LC-MS/MS study, Hsp90 was identified as its molecular target, which is a fully different mechanism of action from what we reported before. Further studies showed compound 10 directly engaged the N-terminal site of Hsp90 and promoted the degradation of β-catenin, thereby suppressing the Wnt/β-catenin signaling. More importantly, compound 10 exhibits favorable pharmacokinetic parameters and significant anti-tumor efficacies in the HCT116 xenograft model. Taken together, this study furnished the discovery of candidate drug compound 10 possessing a novel fused tetrahydroisoquinoline scaffold with excellent in vitro and in vivo anti-CRC activities by targeting Hsp90 to disturb Wnt/β-catenin signaling pathway, which lay a foundation for discovering more effective CRC-targeted therapies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.)

Background and Purpose: Ulcerative colitis (UC) is a refractory inflammatory disease associated with immune dysregulation. Elevated levels of heat shock protein (HSP) 90 in the β but not α subtype were positively associated with disease status in UC patients. This study validated the possibility that pharmacological inhibition or reduction of HSP90β would alleviate colitis, induced by dextran sulfate sodium, in mice and elucidated its mechanisms., Experimental Approach: Histopathological and biochemical analysis assessed disease severity, and bioinformatics and correlation analysis explained the association between the many immune cells and HSP90β. Flow cytometry was used to analyse the homeostasis and transdifferentiation of Th17 and Treg cells. In vitro inhibition and adoptive transfer assays were used to investigate functions of the phenotypically transformed Th17 cells. Metabolomic analysis, DNA methylation detection and chromatin immunoprecipitation were used to explore these mechanisms., Key Results: The selective pharmacological inhibitor (HSP90βi) and shHSP90β significantly mitigated UC in mice and promoted transformation of Th17 to Treg cell phenotype, via Foxp3 transcription. The phenotypically-transformed Th17 cells by HSP90βi or shHSP90β were able to inhibit lymphocyte proliferation and colitis in mice. HSP90βi and shHSP90β selectively weakened glycolysis by stopping the direct association of HSP90β and GLUT1, the key glucose transporter, to accelerate ubiquitination degradation of GLUT1, and enhance the methylation of Foxp3 CNS2 region. Then, the mediator path was identified as the "lactate-STAT5-TET2" cascade., Conclusion and Implications: HSP90β shapes the fate of Th17 cells via glycolysis-controlled methylation modification to affect UC progression, which provides a new therapeutic target for UC., (© 2024 British Pharmacological Society.)

Targeting the heat shock protein-90 (Hsp90) chaperone machinery in various cancers with 200 monotherapy or combined-therapy clinical trials since 1999 has not yielded any success of food and drug administration approval. Blames for the failures were unanimously directed at the Hsp90 inhibitors or tumors or both. However, analyses of recent cellular and genetic studies together with the Hsp90 data from the Human Protein Atlas database suggest that the vast variations in Hsp90 expression among different organs in patients might have been the actual cause. It is evident now that Hsp90β is the root of dose-limiting toxicity (DLT), whereas Hsp90α is a buffer of penetrated Hsp90 inhibitors. The more Hsp90α, the safer Hsp90β, and the lower DLT are for the host. Unfortunately, the dramatic variations of Hsp90, from total absence in the eye, muscle, pancreas, and heart to abundance in reproduction organs, lung, liver, and gastrointestinal track, would cause the selection of any fair toxicity biomarker and an effective maximum tolerable dose (MTD) of Hsp90 inhibitor extremely challenging. In theory, a safe MTD for the organs with high Hsp90 could harm the organs with low Hsp90. In reverse, a safe MTD for organs with low or undetectable Hsp90 would have little impact on the tumors, whose cells exhibit average 3-7% Hsp90 over the average 2-3% Hsp90 in normal cells. Moreover, not all tumor cell lines tested follow the "inhibitor binding-client protein degradation" paradigm. It is likely why the oral Hsp90 inhibitor TAS-116 (Pimitespib), which bypasses blood circulation and other organs, showed some beneficiary efficacy by conveniently hitting tumors along the gastrointestinal track. The critical question is what the next step will be for the Hsp90 chaperone as a cancer therapeutic target., Competing Interests: Declarations of interest The authors declare the following financial interests/personal relationships, which may be considered as potential competing interests. Wei Li reports financial support was provided by the National Institutes of Health. Mei Chen reports financial support was provided by the National Institutes of Health. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Glucose-regulated protein 94 (Grp94) is an isoform of the heat shock protein 90 kDa (Hsp90) family of molecular chaperones. Inhibiting Grp94 has been implicated for many diseases. Co-crystal structures of two generations of Grp94 inhibitors revealed the importance of investigating the ester group, which is projected into the site 2 pocket unique to Grp94. Therefore, a series of KUNG65 benzamide analogs was designed and synthesized to evaluate their impact on the affinity and selectivity for Grp94. The data demonstrated that substituents with small and saturated ring systems that contain hydrogen bond acceptors exhibited increased affinity for Grp94, whereas larger saturated ring system manifested increased selectivity for Grp94 over Hsp90α., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Objective: Multiple factors contribute to the development of perioperative neurocognitive disorders (PND). This study was designed to investigate whether Histone Deacetylase 6 (HDAC6) was involved in the formation of postoperative cognitive dysfunction in elderly mice by regulating the degree of acetylation of heat shock protein (HSP90) and related protein functions and quantities., Methods: C57BL/6 J male mice were randomly divided into six groups: control naive (group Control), anesthesia (group Anesthesia), splenectomy surgery (group Surgery), splenectomy surgery plus dissolvent (group Vehicles), splenectomy surgery plus the inhibitor ACY-1215 (group Ricolinostat), and splenectomy surgery plus the inhibitor RU-486(group Mifepristone). After the mice were trained for Morris Water Maze (MWM) test for five days, anesthesia and operational surgery were carried out the following day. Cognitive function was assessed on the 1st, 3rd and 7th days post-surgery. The hippocampi were harvested on days 1, 3, and 7 post-surgeries for Western blots and ELISA assays., Results: Mice with the splenectomy surgery displayed the activation of the hypothalamic-pituitary-adrenal axis (HPA-axis), marked an increase in adrenocorticotropic hormone (ACTH), glucocorticoid, mineralocorticoid at the molecular level and impaired spatial memory in the MWM test. The hippocampus of surgical groups showed a decrease in acetylated HSP90, a rise in glucocorticoid receptor (GR)-HSP90 association, and an increase in GR phosphorylation and translocation. HDAC6 was increased after the surgical treated. Using two specific inhibitors, HDAC6 inhibitor Ricolinostat (ACY-1215) and GR inhibitor Mifepristone (RU-486), can partially mitigate the effects caused by surgical operation., Conclusions: Abdominal surgery may impair hippocampal spatial memory, possibly through the HDAC6-triggered increase in the function of HSP90, consequently strengthening the negative role of steroids in cognitive function. Targeting HDAC6- HSP90/GR signaling may provide a potential avenue for the treatment of the impairment of cognitive function after surgery., Competing Interests: Declaration of competing interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Tumor-associated macrophages (TAMs) originating from monocytes are crucial for cancer progression; however, the mechanism of TAM differentiation is unclear. We investigated factors involved in the differentiation of monocytes into TAMs within the tumor microenvironment of triple-negative breast cancer (TNBC). We screened 172 compounds and found that a heat shock protein 90 (HSP90) inhibitor blocked TNBC-induced monocyte-to-TAM differentiation in human monocytes THP-1. TNBC-derived conditional medium (CM) activated cell signaling pathways, including MAP kinase, AKT and STAT3, and increased the expression of TAM-related genes and proteins. These inductions were suppressed by HSP90 inhibition or by knockdown of HSP90 in TNBC. Additionally, we confirmed that TNBC secreted HSP90 extracellularly and that HSP90 itself promoted TAM differentiation. In a mouse tumor model, treatment with an HSP90 inhibitor suppressed tumor growth and reduced TAMs in the tumor microenvironment. Our findings demonstrate the role of HSP90 in TAM differentiation, suggesting HSP90 as a potential target for TNBC immunotherapy due to its regulatory role in monocyte-to-TAM differentiation., (© 2024. The Author(s).)

The inhibition of heat shock protein 90 (HSP90), a molecular chaperone, has been proposed to be a potential novel treatment strategy for Coronavirus disease 2019 (COVID-19). In contrast to other studies, our data demonstrated that RGRN-305, a HSP90 inhibitor, exacerbated the cytopathic effect and did not reduce the viral shedding in VeroE6-hTMPRSS2 cells infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Likewise in a murine model of SARS-CoV-2, transgenic mice treated orally with RGRN-305 exhibited reduced survival by the end of the experiment (day 12) as 14% (1/7) survived compared to 63% (5/8) of those treated with drug-vehicle. Animal weight was not reduced by the RGRN-305 treatment. Interestingly, we demonstrated that inhibition of HSP90 by RGRN-305 significantly dampened the inflammatory response induced by SARS-CoV-2 spike protein in human macrophage-like cells (U937) and human lung epithelial cells (A549). Measured by quantitative real-time PCR, the mRNA expression of the proinflammatory cytokines TNF, IL1B and IL6 were significantly reduced. Together, these data suggest that HSP90 inhibition by RGRN-305 exacerbates the SARS-CoV-2 infection in vitro and reduces the survival of mice infected with SARS-CoV-2, but exhibits strong anti-inflammatory properties. This data shows that while RGRN-305 may be helpful in a 'cytokine storm', it has no beneficial impact on viral replication or survival in animals as a monotherapy. Further animal studies with HSP90 inhibitors in combination with an anti-viral drug may provide additional insights into its utility in viral infections and whether HSP90 inhibition may continue to be a potential treatment strategy for COVID-19 disease., Competing Interests: I have read the journal’s policy and the authors of this manuscript have the following competing interests: H.B.A has received research grants from Aage Bangs Fund and participated in clinical trials sponsored by Galderma, Regranion and UCB. C.J. has served as a paid speaker for LEO Pharma, Eli Lilly and L’Oréal This does not alter our adherence to PLOS ONE policies on sharing data and materials., (Copyright: © 2024 Ben Abdallah et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Heat shock protein 90 (HSP90), a highly conserved member of the heat shock protein family, regulates various proteins and signaling pathways involved in cancer, making it a promising target for cancer therapy. Traditional HSP90 inhibitors have demonstrated significant antitumor potential in preclinical trials, with over 20 compounds advancing to clinical trials and showing promising results. However, the limited clinical efficacy and shared toxicity of these inhibitors restrict their further clinical use. Encouragingly, developing novel inhibitors using conventional medicinal chemistry approaches─such as selective inhibitors, dual inhibitors, protein-protein interaction inhibitors, and proteolysis-targeting chimeras─is expected to address these challenges. Notably, the selective inhibitor TAS-116 has already been successfully marketed. In this Perspective, we summarize the structure, biological functions, and roles of HSP90 in cancer, analyze the clinical status of HSP90 inhibitors, and highlight the latest advancements in novel strategies, offering insights into their future development.

Targeted protein degradation (TPD) is an emerging therapeutic paradigm aimed at eliminating the disease-causing protein with aberrant expression. Herein, we report a new approach to inducing intracellular glutathione peroxidase 4 (GPX4) protein degradation to trigger ferroptosis by bridging the target protein to heat shock protein 90 (HSP90), termed HSP90 interactome-mediated proteolysis targeting chimera (HIM-PROTAC). Different series of HIM-PROTACs were synthesized and evaluated, and two of them, GDCNF-2/GDCNF-11 potently induced ferroptosis via HSP90-mediated ubiquitin-proteasomal degradation of GPX4 in HT-1080 cells with DC 50 values of 0.18 and 0.08 μM, respectively. In particular, GDCNF-11 showed 15-fold more ferroptosis selectivity over GPX4 inhibitor ML162. Moreover, these two degraders effectively suppress tumor growth in the mice model with relatively low toxicity as compared to the combination therapy of GPX4 and HSP90 inhibitors. In general, this study demonstrated the feasibility of degrading GPX4 via HSP90 interactome, and thus provided a significant complement to existing TPD strategies.

The activation of PP5 is essential for a variety of cellular processes, as it participates in a variety of biological pathways by dephosphorylating substrates. However, activation of PP5 by small molecules has been a challenge due to its native "self-inhibition" mechanism, which is controlled by the N-terminal TPR domain and the C-terminal αJ helix. Here, we reported the discovery of DDO-3733 , a well-identified TPR-independent PP5 allosteric activator, which facilitates the dephosphorylation process of downstream substrates. Considering the negative regulatory effect of PP5 on heat shock transcription factor HSF1, pharmacologic activation of PP5 by DDO-3733 was found to reduce the HSP90 inhibitor-induced heat shock response. These results provide a chemical tool to advance the exploration of PP5 as a potential therapeutic target and highlight the value of pharmacological activation of PP5 to reduce heat shock toxicity of HSP90 inhibitors.

The development of effective drugs for cervical cancer is urgently required because of its high mortality rate and the limited treatment options. Herein, we report the design, synthesis, and evaluation of a series of novel and effective Hsp90-targeting PROTACs. These compounds exhibited potent anti-proliferative activity against cervical cancer cells with low IC 50 values. Compound lw13 effectively degraded Hsp90 at a concentration of only 0.05 μM. In addition, it can inhibit the metastasis of cancer cells and induce significant cell cycle arrest and apoptosis. Furthermore, lw13 demonstrated remarkable antitumor activity both in vitro and in vivo, and has a synergistic effect in combination with cisplatin. Moreover, lw13 can prevent the activation of the HER2/AKT/mTOR signaling pathway by indirectly reducing the levels of HER2 and AKT. This study paves the way for cancer treatment and provides valuable insights into the combination therapy of cervical cancer., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Masson SAS.)

As a molecular chaperone, heat shock protein 90 (HSP90) plays important roles in the folding, stabilization, activation, and degradation of over 500 client proteins, and is extensively involved in cell signaling, proliferation, and survival. Thus, it has emerged as an important target in a variety of diseases, including cancer, neurodegenerative diseases, and viral infections. Therefore, targeted inhibition of HSP90 provides a valuable and promising therapeutic strategy for the treatment of HSP90-related diseases. This review aims to systematically summarize the progress of research on HSP90 inhibitors in the last five years, focusing on their structural features, design strategies, and biological activities. It will refer to the natural products and their derivatives (including novobiocin derivatives, deguelin derivatives, quinone derivatives, and terpenoid derivatives), and to synthetic small molecules (including resorcinol derivatives, pyrazoles derivatives, triazole derivatives, pyrimidine derivatives, benzamide derivatives, benzothiazole derivatives, and benzofuran derivatives). In addition, the major HSP90 small-molecule inhibitors that have moved into clinical trials to date are also presented here., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.)

Objective: This study aimed to assess linagliptin's inhibitory effects on the proliferation of cervical cancer cell lines and investigate its potential for targeting human heat shock protein 90., Methods: Linagliptin's cytotoxicity was assessed on a cervical cancer cell line (Hela cancer cell line) at two different incubation periods, 24 and 72 hours. The molecular docking between linagliptin and the receptor protein human Hsp 90 (PDB code: 5XRE) was performed using the Biovia Discovery Studio and AutoDock tool software. The Discovery Studio visualizer generated three-dimensional (3D) and two-dimensional (2D) interactive images., Results: The study's cytotoxicity results demonstrated that linagliptin can inhibit the proliferation of cervical cancer cells. The cytotoxicity exhibited a time-dependent pattern (cell cycle specific). The molecular docking study was conducted to investigate the interaction between linagliptin and human Hsp90. The study identified 11 sites where linagliptin can bind to Hsp90 amino acid residues. The total docking score for this interaction was -10.3 kcal/mol. The most potent binding occurred through conventional hydrogen bonds with the ASP:54 amino acid residues at a distance of 2.93 Å. The docking scores for linagliptin were comparable to those of the reference drug geldanamycin, indicating a strong interaction between linagliptin and Hsp90., Conclusion: The study has found that linagliptin successfully reduces the growth of cervical cancer cells with a time-dependent cytotoxic pattern. The potential anticancer mechanism of linagliptin can be inferred by analyzing the docking score and docking pattern between linagliptin and Hsp90, suggesting that linagliptin targets human Hsp 90.

Heat shock protein 90 (HSP90) plays a crucial role in cancer cell growth and metastasis by stabilizing overexpressed signaling proteins. Inhibiting HSP90 has emerged as a promising anti-cancer strategy. In this study, we aimed to develop and characterize a HSP90-targeted molecular imaging probe, [ 64 Cu]Cu-DOTA-BDA-GM, based on a specific HSP90 inhibitor, geldanamycin (GM), for PET imaging of cancers. GM is modified at the C-17 position with 1,4-butane-diamine (BDA) and linked to 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) for 64 Cu radiolabeling. We evaluated the probe's specific binding to HSP90-expressing cells using Chinese hamster ovary (CHO) cells and breast cancer cells including MDA-MB-231, MDA-MB-435S, MCF7, and KR-BR-3 cell lines. A competition study with non-radioactive GM-BDA yielded an IC50 value of 1.35 ± 0.14 nM, underscoring the probe's affinity for HSP90. In xenograft models of MDA-MB-231 breast cancer, [ 64 Cu]Cu-DOTA-BDA-GM showcased targeted tumor localization, with significant radioactivity observed up to 18 h post-injection. Blocking studies using unlabeled GM-BDA and treatment with the anticancer drug Vorinostat (SAHA), which can affect the expression and activity of numerous proteins, such as HSPs, confirmed the specificity and sensitivity of the probe in cancer targeting. Additionally, PET/CT imaging in a lung metastasis mouse model revealed increased lung uptake of [ 64 Cu]Cu-DOTA-BDA-GM in metastatic sites, significantly higher than in non-metastatic lungs, illustrating the probe's ability to detect metastatic breast cancer. In conclusion, [ 64 Cu]Cu-DOTA-BDA-GM represents a sensitive and specific approach for identifying HSP90 expression in breast cancer and metastases, offering promising implications for clinical diagnosis and monitoring., Competing Interests: Declaration of competing interest All authors report no conflicts of interest or relationships relevant to the contents of this manuscript to disclose. This work was prepared while Dr. Zheng Li was employed at Houston Methodist Hospital Research Institute. The opinions expressed in this article are the author's own and do not reflect the view of the National Institutes of Health, the Department of Health and Human Services, or the United States government., (Copyright © 2024 Elsevier Inc. All rights reserved.)

New derivatives of tropane scaffold were prepared from the reaction of their thione or thioamide derivatives with α-halocarbonyl compounds. The structures of all new derivatives were assured and proved with their spectral data. The novel tropane derivatives were examined for their cytotoxicity on two colon tumor cell lines; Caco2 and HCT116 cells. The most active compounds 3, 4, 5, 9d and 14a displayed significant antitumor activities with IC 50 range of 9.50 - 30.15 μM compared to doxorubicin. Moreover, they revealed reduced cytotoxic effect on WI-38 normal ones, signifying their great safety. With the aim of better understanding the inhibitory potential of such compounds on heat-shock protein 90 (Hsp90), there activities were assessed against such enzyme demonstrating high inhibitory activities with IC 50 range of 56.58-78.85 nM. Western blotting was carried out to ensure the inhibitory activity on Hsp90, results showed that 3 markedly suppressed Hsp90 expression on Caco2 cell line. Additionally, a molecular docking analysis of the most potent derivatives at the Hsp90 binding site was carried out in order to approve the performed in vitro assays., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The precise delivery of drugs to tumor sites and the thermoresistance of tumors remain major challenges in photothermal therapy (PTT). Somatostatin receptor 2 (SSTR2) is proposed as an ideal target for the precise treatment of SCLC. We developed a targeting nano-drug delivery system comprising anti-SSTR2 monoclonal antibody (MAb) surface-modified nanoparticles co-encapsulating Cypate and gambogic acid (GA). The formed SGCPNs demonstrated excellent monodispersity, physiological stability, preferable biocompatibility, and resultant efficient photothermal conversion efficacy. SGCPNs were quickly internalized by SSTR2-overexpressing SCLC cells, triggering the release of GA under acidic and near-infrared (NIR) laser irradiation environments, leading to their escape from lysosomes to the cytosol and then diffusion into the nucleus. SGCPNs can not only decrease the cell survival rate but also inhibit the activity of heat shock protein 90 (HSP90). SGCPNs can be precisely delivered to xenograft tumors of SSTR2-positive SCLC in vivo. Upon NIR laser irradiation, therapy of SGCPNs showed significant tumor regression. In conclusion, SGCPNs provide a new chemo-photothermal synergistic treatment strategy for targeting SCLC., (© 2024 UICC.)

Background: The surplus cytokines remaining after use in the early stages of the inflammatory response stimulate immune cells even after the response is over, causing a secondary inflammatory response and ultimately damaging the host, which is called a cytokine storm. Inhibiting heat shock protein 90 (Hsp90), which has recently been shown to play an important role in regulating inflammation in various cell types, may help control excessive inflammatory responses and cytokine storms., Methods: We discovered an anti-inflammatory compound by measuring the inhibitory effect of CD86 expression on spleen DCs (sDCs) using the chemical compounds library of Hsp90 inhibitors. Subsequently, to select the hit compound, the production of cytokines and expression of surface molecules were measured on the bone marrow-derived DCs (BMDCs) and peritoneal macrophages. Then, we analyzed the response of antigen-specific Th1 cells. Finally, we confirmed the effect of the compound using acute lung injury (ALI) and delayed-type hypersensitivity (DTH) models., Results: We identified Be01 as the hit compound, which reduced CD86 expression the most in sDCs. Treatment with Be01 decreased the production of pro-inflammatory cytokines (IL-6, TNF-α, and IL-1β) in BMDC and peritoneal macrophages stimulated by LPS. Under the DTH model, Be01 treatment reduced ear swelling and pro-inflammatory cytokines in the spleen. Similarly, Be01 treatment in the ALI model decreased neutrophil infiltration and lower levels of secreted cytokines (IL-6, TNF-α)., Conclusions: Reduction of CD80 and CD86 expression on DCs by Be01 indicates reduced secondary inflammatory response by Th1 cells, and reduced release of pro-inflammatory cytokines by peritoneal macrophages may initially control the cytokine storm., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Background: Gastric cancer (GC) is a prevalent malignancy with limited therapeutic options for advanced stages. This study aimed to identify novel therapeutic targets for GC by profiling HSP90 client kinases., Methods: We used mass spectrometry-based activity-based protein profiling (ABPP) with a desthiobiotin-ATP probe, combined with sensitivity analysis of HSP90 inhibitors, to profile kinases in a panel of GC cell lines. We identified kinases regulated by HSP90 in inhibitor-sensitive cells and investigated the impact of MASTL knockdown on GC cell behavior. Global proteomic analysis following MASTL knockdown was performed, and bioinformatics tools were used to analyze the resulting data., Results: Four kinases-MASTL, STK11, CHEK1, and MET-were identified as HSP90-regulated in HSP90 inhibitor-sensitive cells. Among these, microtubule-associated serine/threonine kinase-like (MASTL) was upregulated in GC and associated with poor prognosis. MASTL knockdown decreased migration, invasion, and proliferation of GC cells. Global proteomic profiling following MASTL knockdown revealed NEDD4-1 as a potential downstream mediator of MASTL in GC progression. NEDD4-1 was also upregulated in GC and associated with poor prognosis. Similar to MASTL inhibition, NEDD4-1 knockdown suppressed migration, invasion, and proliferation of GC cells., Conclusions: Our multi-proteomic analyses suggest that targeting MASTL could be a promising therapy for advanced gastric cancer, potentially through the reduction of tumor-promoting proteins including NEDD4-1. This study enhances our understanding of kinase signaling pathways in GC and provides new insights for potential treatment strategies., (© 2024. The Author(s).)

Drug repositioning is an important therapeutic strategy for treating breast cancer. Hsp90β chaperone is an attractive target for inhibiting cell progression. Its structure has a disordered and flexible linker region between the N-terminal and central domains. Geldanamycin was the first Hsp90β inhibitor to interact specifically at the N-terminal site. Owing to the toxicity of geldanamycin, we investigated the repositioning of ritonavir as an Hsp90β inhibitor, taking advantage of its proven efficacy against cancer. In this study, we used molecular modeling techniques to analyze the contribution of the Hsp90β linker region to the flexibility and interaction between the ligands geldanamycin, ritonavir, and Hsp90β. Our findings indicate that the linker region is responsible for the fluctuation and overall protein motion without disturbing the interaction between the inhibitors and the N-terminus. We also found that ritonavir established similar interactions with the substrate ATP triphosphate, filling the same pharmacophore zone.

Triple-negative breast cancer (TNBC) remains a treatment challenge and requires innovative therapies. Hsp90, crucial for the stability of numerous oncogenic proteins, has emerged as a promising therapeutic target. In this study, we present the optimization of the Hsp90 C-terminal domain (CTD) inhibitor TVS21 . Biochemical methods, NMR binding studies, and molecular modeling were employed to investigate the binding of representative analogs to Hsp90. The newly synthesized analogs showed increased antiproliferative activity in breast cancer cell lines, including the MDA-MB-231 TNBC cell line. Compounds 89 and 104 proved to be the most effective, inducing apoptosis, slowing proliferation, and degrading key oncogenic proteins without inducing a heat shock response. In vivo, compound 89 showed comparable efficacy to the clinical candidate AUY922 and a better safety profile in a TNBC xenograft model. These results highlight the promise of Hsp90 CTD inhibitors for TNBC therapy, potentially filling a significant treatment gap.

The discovery of antimicrobials with novel mechanisms of action is crucial to tackle the foreseen global health crisis due to antimicrobial resistance. Bacterial two-component signaling systems (TCSs) are attractive targets for the discovery of novel antibacterial agents. TCS-encoding genes are found in all bacterial genomes and typically consist of a sensor histidine kinase (HK) and a response regulator. Due to the conserved Bergerat fold in the ATP-binding domain of the TCS HK and the human chaperone Hsp90, there has been much interest in repurposing inhibitors of Hsp90 as antibacterial compounds. In this study, we explore the chemical space of the known Hsp90 inhibitor scaffold 3,4-diphenylpyrazole (DPP), building on previous literature to further understand their potential for HK inhibition. Six DPP analogs inhibited HK autophosphorylation in vitro and had good antimicrobial activity against Gram-positive bacteria. However, mechanistic studies showed that their antimicrobial activity was related to damage of bacterial membranes. In addition, DPP analogs were cytotoxic to human embryonic kidney cell lines and induced the cell arrest phenotype shown for other Hsp90 inhibitors. We conclude that these DPP structures can be further optimized as specific disruptors of bacterial membranes providing binding to Hsp90 and cytotoxicity are lowered. Moreover, the X-ray crystal structure of resorcinol, a substructure of the DPP derivatives, bound to the HK CheA represents a promising starting point for the fragment-based design of novel HK inhibitors., Importance: The discovery of novel antimicrobials is of paramount importance in tackling the imminent global health crisis of antimicrobial resistance. The discovery of novel antimicrobials with novel mechanisms of actions, e.g., targeting bacterial two-component signaling systems, is crucial to bypass existing resistance mechanisms and stimulate pharmaceutical innovations. Here, we explore the possible repurposing of compounds developed in cancer research as inhibitors of two-component systems and investigate their off-target effects such as bacterial membrane disruption and toxicity. These results highlight compounds that are promising for further development of novel bacterial membrane disruptors and two-component system inhibitors., Competing Interests: The authors declare no conflict of interest.

Objectives: GL-V9 exhibited anti-tumour effects on various types of tumours. This study aimed to verify if GL-V9 synergized with oxaliplatin in suppressing colorectal cancer (CRC) and to explore the synergistic mechanism., Methods: The synergy effect was tested by MTT assays and the mechanism was examined by comet assay, western blotting and immunohistochemistry (IHC). Xenograft model was constructed to substantiated the synergy effect and its mechanism in vivo., Results: GL-V9 was verified to enhance the DNA damage effect of oxaliplatin, so as to synergistically suppress colon cancer cells in vitro and in vivo. In HCT-116 cells, GL-V9 accelerated the degradation of Wee1 and induced the abrogation of cell cycle arrest and mis-entry into mitosis, bypassing the DNA damage response caused by oxaliplatin. Our findings suggested that GL-V9 binding to HSP90 was responsible for the degradation of Wee1 and the vulnerability of colon cancer cells to oxaliplatin. Functionally, overexpression of either HSP90 or WEE1 annulled the synergistic effect of GL-V9 and oxaliplatin., Conclusions: Collectively, our findings revealed that GL-V9 synergized with oxaliplatin to suppress CRC and displayed a promising strategy to improve the efficacy of oxaliplatin., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Royal Pharmaceutical Society. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Background/aim: Most clear cell renal cell carcinomas (ccRCCs) have a dysfunctional von Hippel-Lindau tumor suppressor protein (VHL). Hypoxia-inducible factors 1 and 2 alpha (HIF1α and HIF2α) accumulate in ccRCC with dysfunctional VHL and up-regulate the vascular endothelial growth factor (VEGF) pathway and tumor angiogenesis. Recently, pimitespib (PIM), a potent ATP-competitive inhibitor of heat shock protein 90 (HSP90), was developed. PIM down-regulates the expression of HIF, a key protein in ccRCC progression, with anti-angiogenic effects. This study aimed to examine the effectiveness of PIM in ccRCC and the underlying mechanisms., Materials and Methods: The efficacy and mechanism of PIM against ccRCCs was evaluated using ccRCC cell lines., Results: PIM inhibited the VEGFR pathway by down-regulating VEGFR 2, phosphorylated VEGFR 2, and protein levels in downstream signaling pathways. The growth of ccRCC cell lines was inhibited by PIM. Furthermore, PIM inhibits HIF1α, HIF2α, and VEGF expression, suggesting that PIM may suppress angiogenesis in addition to the VEGFR pathway., Conclusion: PIM provides a novel approach for treating ccRCC and holds promise for future clinical strategies. Further in vivo and clinical research is required to elucidate the detailed relationship between the effects of PIM and ccRCC., (Copyright © 2024 International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

24 C3'-focused hybrids of aryl/penta-1,4-dien-3-one/amine (APDA) were designed and synthesized. Of these hybrids, 2 n demonstrated improved antiproliferative effects on HER2-positive breast cancer cells (SKBr3 and BT474) and triple-negative breast cancer (TNBC) cells (MDA-MB-231 and MDA-MB-468) with IC 50 values ranging from 7.45 to 10.75 μM, but less toxicity to normal breast cells MCF-10A than the first generation of hybrid 1. Additionally, 2 n retained its ability to inhibit HSP90C-terminus, leading to the degradation of HSP90 client proteins HER2, EGFR, pAKT, AKT, and CDK4, without inducing a heat-shock response. Notably, 2 n also demonstrated improved thermostability compared to 1 and maintained in vitro metabolic stability in simulated intestinal fluid. These findings will provide a scientific basis for developing HSP90C-terminal inhibitors in the future., (© 2024 Wiley-VHCA AG, Zurich, Switzerland.)

The aim of this study was to investigate histone deacetylase 6 (HDAC6) modifies the heat shock protein 90 (HSP90) and heat shock transcription factor 1 (HSF1) affect the levels of pathological markers such as Aβ oligomers (Aβo) and Tau phosphorylation (p-Tau) in APP/PS1 double transgenic mice hippocampal tissues or HT22 neurons as well as the changes in cognitive behavioral functions of mice. (1) APP/PS1 transgenic mice (6 months old, 25 ~ 30 g) were randomly assigned to 5 experimental groups, C57BL/6J mice (6 months old, 25 ~ 30 g) were used as 4 control groups, with 8 mice in each group. All mice underwent intracerebroventricular (i.c.v.) cannulation, and the experimental groups were administered with normal saline (APP + NS group), HDAC6 agonist tubastatin A hydrochloride (TSA) (APP + TSA group) or HDAC6 agonist theophylline (Theo) (APP + Theo group), HSP90 inhibitor Ganetespib (Gane) (APP + Gane group), or a combination of pre-injected Gane by TSA (APP + Gane + TSA group); the control group received i.c.v. injections of Gane (Gane group), TSA (TSA group), Theo (Theo group) or NS (NS group), respectively. (2) Mouse hippocampal neurons HT22 were randomly divided into a control group (Control) and an Aβ 1-42 intervention group (Aβ). Within the Aβ group, further divisions were made for knockdown HSP90 (Aβ + siHSP90 group), overexpression HSP90 (Aβ + OE-HSP90 group), knockdown HSF1(Aβ + siHSF1 group) and knockdown HSF1 followed by overexpression HSP90 (Aβ + siHSF1 + OE-HSP90 group), resulting in a total of 6 groups. Morris water maze test was used to evaluate the cognitive behavior of the mice. Western blot and immunohistochemistry or immunofluorescence were performed to detect the levels of HDAC6, HSP90, HSF1, Aβ 1-42 , Tau protein, and p-Tau in the hippocampal tissue or HT22 cells. qRT-PCR was used to measure the levels of hdac6, hsp90, and hsf1 mRNA in the hippocampus or nerve cells. (1) The levels of HDAC6, Aβ 1-42 and p-Tau were elevated, while HSP90 and HSF1 were decreased in the hippocampal tissue of APP/PS1 transgenic mice (all P < 0.01). Inhibiting HDAC6 upregulated the expressions of HSP90 and HSF1 in the hippocampal tissue of APP/PS1 mice, while decreasing the levels of Aβ 1-42 and p-Tau as well as improving the spatial cognitive behavior in mice (P < 0.05 or P < 0.01). The opposite effects were observed upon HDAC6 activation. However, inhibiting HSP90 reduced the expression of HSF1 (P < 0.01) and increased the levels of Aβ 1-42 and p-Tau (P < 0.05 or P < 0.01) but did not significantly affect the expression of HDAC6 (P > 0.05). No significant changes were observed in the aforementioned indicators in the 4 control groups (P > 0.05). (2) In the Aβ 1-42 intervention group, HDAC6 and Aβ 1-42 , p-Tau expression levels were elevated, while HSP90 and HSF1 expressions were all decreased, and cell viability was reduced (P < 0.05 or P < 0.01). Overexpression of HSP90 upregulated HSF1 expression, decreased the levels of Aβ 1-42 and p-Tau, and increased cell viability (P < 0.05 or P < 0.01). Knocking down HSP90 had the opposite effect; and knocking down HSF1 increased the levels of Aβ 1-42 and p-Tau and decreased cells viability (all P < 0.01), but did not result in significant changes in the expression levels of HSP90 (P > 0.05). Inhibiting HDAC6 can upregulate the expressions of HSP90 and HSF1 but reduce the levels of Aβ 1-42 and p-Tau in the hippocampus of APP/PS1 mice and improvement of cognitive behavioral function in mice; Overexpression of HSP90 can increase HSF1 but decrease Aβ 1-42 and p-Tau levels in the hippocampal neurons and increase cell activity. It is suggested that HDAC6 may affect the formation of Aβ oligomers and the changes in Tau protein phosphorylation levels in the hippocampus of AD transgenic mouse as well as the alterations in cognitive behavioral functions by regulating the HSP90-HSF1 pathway., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The development of new anticancer agents is one of the most urgent topics in drug discovery. Inhibition of molecular chaperone Hsp90 stands out as an approach that affects various oncogenic proteins in different types of cancer. These proteins rely on Hsp90 to obtain their functional structure, and thus Hsp90 is indirectly involved in the pathophysiology of cancer. However, the most studied ATP-competitive inhibition of Hsp90 at the N-terminal domain has proven to be largely unsuccessful clinically. Therefore, research has shifted towards Hsp90 C-terminal domain (CTD) inhibitors, which are also the focus of this study. Our recent discovery of compound C has provided us with a starting point for exploring the structure-activity relationship and optimising this new class of triazole-based Hsp90 inhibitors. This investigation has ultimately led to a library of 33 analogues of C that have suitable physicochemical properties and several inhibit the growth of different cancer types in the low micromolar range. Inhibition of Hsp90 was confirmed by biophysical and cellular assays and the binding epitopes of selected inhibitors were studied by STD NMR. Furthermore, the most promising Hsp90 CTD inhibitor 5x was shown to induce apoptosis in breast cancer (MCF-7) and Ewing sarcoma (SK-N-MC) cells while inducing cause cell cycle arrest in MCF-7 cells. In MCF-7 cells, it caused a decrease in the levels of ERα and IGF1R, known Hsp90 client proteins. Finally, 5x was tested in zebrafish larvae xenografted with SK-N-MC tumour cells, where it limited tumour growth with no obvious adverse effects on normal zebrafish development., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

The evolutionary conserved molecular chaperone heat shock protein 90 (HSP90) plays an indispensable role in tumorigenesis by stabilizing client oncoproteins. Although the functionality of HSP90 is tightly regulated, cancer cells exhibit a unique dependence on this chaperone, leading to its overexpression, which has been associated with poor prognosis in certain malignancies. While various strategies targeting heat shock proteins (HSPs) involved in carcinogenesis have been explored, only inhibition of HSP90 has consistently and effectively resulted in proteasomal degradation of its client proteins. To date, a total of 22 HSP90 inhibitors (HSP90i) have been tested in 186 cancer clinical trials, as reported by clinicaltrials.gov. Among these trials, 60 % have been completed, 10 % are currently active, and 30 % have been suspended, terminated, or withdrawn. HSP90 inhibitors (HSP90i) have been used as single agents or in combination with other drugs for the treatment of various cancer types in clinical trials. Notably, improved clinical outcomes have been observed when HSP90i are used in combination therapies, as they exhibit a synergistic antitumor effect. However, as single agents, HSP90i have shown limited clinical activity due to drug-related toxicity or therapy resistance. Recently, active trials conducted in Japan evaluating TAS-116 (pimitespib) have demonstrated promising results with low toxicity as monotherapy and in combination with the immune checkpoint inhibitor nivolumab. Exploratory biomarker analyses performed in various trials have demonstrated target engagement that suggests the potential for identifying patient populations that may respond favorably to the therapy. In this review, we discuss the advances made in the past 5 years regarding HSP90i and their implications in anticancer therapeutics. Our focus lies in evaluating drug efficacy, prognosis forecast, pharmacodynamic biomarkers, and clinical outcomes reported in published trials. Through this comprehensive review, we aim to shed light on the progress and potential of HSP90i as promising therapeutic agents in cancer treatment., Competing Interests: Declarations of interest The authors have no conflict of interest to disclose., (Copyright © 2024. Published by Elsevier Inc.)

Human Hsp90 chaperones are implicated in various aspects of cancer. Due to this, Hsp90 has been explored as potential target in cancer treatment. Initial attempts to use Hsp90 inhibitors in drug trials failed due to toxicity and inefficacy. The next generation of drugs were less toxic but still insufficiently effective in a clinical setting. Recently, a lot of effort is being put into understanding the consequences of Hsp90 isoform selective inhibition, expecting that this might hold the key in targeting Hsp90 for disease treatment. Here we investigate a series of compounds containing the aryl-resorcinol scaffold with a 5-membered ring as a promising class of new human Hsp90 inhibitors, reaching nanomolar affinity. We compare how the replacement of 5-membered ring, from thiadiazole to imidazole, as well as a variety of their substituents, influences the potency of these inhibitors for Hsp90 alpha and beta isoforms. To further elucidate the dissimilarity in ligand selectivity between the isoforms, a mutant protein was constructed and tested against the ligand library. In addition, we performed a series of molecular dynamics (MD) and docking simulations to further explain our experimental findings as well as evaluated key compounds in cell assays. Our results deepen the understanding of Hsp90 isoform ligand selectivity and serve as an informative base for further Hsp90 inhibitor optimization., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: DM and EK have patents on Hsp90 inhibitors that are not the focus of this study (EP2268626; US2011/0046387). The other authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.)

Extracellular HSP90α (eHSP90α) is a promoter of tumor development and malignant progression. Patients with malignancies, including pancreatic ductal adenocarcinoma (PDAC), have generally shown 5~10-fold increases in serum/plasma eHSP90α levels. In this study, we developed a humanized antibody HH01 to target eHSP90α and evaluated its anticancer efficacy. HH01, with novel complementarity-determining regions, exhibits high binding affinity toward HSP90α. It recognizes HSP90α epitope sites 235 AEEKEDKEEE 244 and 251 ESEDKPEIED 260 , with critical amino acid residues E237, E239, D240, K241, E253, and K255. HH01 effectively suppressed eHSP90α-induced invasive and spheroid-forming activities of colorectal cancer and PDAC cell lines by blocking eHSP90α's ligation with the cell-surface receptor CD91. In mouse models, HH01 potently inhibited the tumor growth of PDAC cell grafts/xenografts promoted by endothelial-mesenchymal transition-derived cancer-associated fibroblasts while also reducing serum eHSP90α levels, reflecting its anticancer efficacy. HH01 also modulated tumor immunity by reducing M2 macrophages and reinvigorating immune T-cells. Additionally, HH01 showed low aggregation propensity, high water solubility, and a half-life time of >18 days in mouse blood. It was not cytotoxic to retinal pigmented epithelial cells and showed no obvious toxicity in mouse organs. Our data suggest that targeting eHSP90α with HH01 antibody can be a promising novel strategy for PDAC therapy.

Neuroblastoma is a common nervous system tumor in childhood, and current treatments are not adequate. HSP90 is a molecular chaperone protein that plays a critical role in the regulation of cancer-related proteins. HSP90 inhibition may exert anticancer effects by targeting cancer-related processes such as tumor growth, cell proliferation, metastasis, and apoptosis. Therefore, HSP90 inhibition is a promising strategy in the treatment of various types of cancer, and the development of next-generation inhibitors could potentially lead to more effective and safer treatments. XL-888 and Debio0932 is a next-generation HSP90 inhibitor and can inhibit the correct folding and stabilization of client proteins that cancer-associated HSP90 helps to fold correctly. In this study, we aimed to investigate the comprehensive molecular pathways of the anticancer activity of XL-888 and Debio0932 in human neuroblastoma cells SH-SY5Y. The cytotoxic effects of XL-888 and Debio0932 on the neuroblastoma cell line SH-SY5Y cells were evaluated by MTT assay. Then, the effect of these HSP90 inhibitors on the expression of important genes in cancer was revealed by Quantitative Real Time Polymerase Chain Reaction (qRT-PCR) method. The qRT-PCR data were evaluated using Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) biological process tools. Finally, the effect of HSP90 inhibitors on HSP27, HSP70 and HSP90 protein expression was investigated by Western blotting analysis. The results revealed that XL-888 and Debio0932 had a role in regulating many cancer-related pathways such as migration, invasion, metastasis, angiogenesis, and apoptosis in SH-SY5Y cells. In conclusion, it shows that HSP90 inhibitors can be considered as a promising candidate in the treatment of neuroblastoma and resistance to chemotherapy., (© 2024. The Author(s).)

The induction of heat stress response (HSR) mediated by the generation of heat shock proteins (HSPs) on exposure to magnetic hyperthermia-mediated cancer therapy (MHCT) decreases the efficacy of localized heat treatment at the tumor site, and thus therapy remains a significant challenge. Hence, the present study examined differential HSR elicited in glioma cells post-MHCT under different tumor microenvironment conditions (2D monolayers, 3D monoculture, and coculture spheroids) to recognize target genes that, when downregulated, could enhance the therapeutic effect of MHCT. Gene expression analysis following MHCT revealed that HSP90 was upregulated as compared to HSP70. Hence, to enhance the efficacy of the treatment, a combinatorial strategy using 17-DMAG as an inhibitor of HSP90 following MHCT was investigated. The effects of combinatorial therapy in terms of cell viability, HSP levels by immunofluorescence and gene expression analysis, oxidative stress generation, and alterations in cellular integrity were evaluated, where combinatorial therapy demonstrated an enhanced therapeutic outcome with maximum glioma cell death. Further, in the murine glioma model, a rapid tumor inhibition of 65 and 53% was observed within 8 days at the primary and secondary tumor sites, respectively, in the MCHT + 17-DMAG group, with abscopal effect-mediated complete tumor inhibition at both the tumor sites within 20 days of MHCT. The extracellularly released HSP90 from dying tumor cells further suggested the induction of immune response supported by the upregulation of IFN-γ and calreticulin genes in the MHCT + 17-DMAG group. Overall, our findings indicate that MHCT activates host immune systems and efficiently cooperates with the HSP90 blockade to inhibit the growth of distant metastatic tumors.

The efficacy of photodynamic therapy (PDT)-related cancer therapies is significantly restricted by two irreconcilable obstacles, i.e., low reactive oxygen species (ROS) generation capability and hypoxia which constrains the immune response. Herein, this work develops a self-assembled clinical photosensitizer indocyanine green (ICG) and the HSP90 inhibitor 17-dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG) nanoparticles (ISDN) without any excipient. This work discovers that the hydrophobic interaction forces between ICG and 17-DMAG promote the photostability of ICG and its intersystem crossing (ISC) process, thereby improving the ROS quantum yield from 0.112 to 0.46. Augmented ROS generation enhances PDT efficacy and further enhances immunogenic cell death (ICD) effects. 17-DMAG inhibits the HSP90/hypoxia-inducible factor 1α (HIF-1α) axis to dramatically reverse the immunosuppressive tumor microenvironment caused by PDT-aggravated hypoxia. In a mouse model of pancreatic cancer, ISDN markedly improve cytotoxic T lymphocyte infiltration and MHC I and MHC II activation, demonstrating the superior ICD effects in situ tumor and the powerful systematic antitumor immunity generation, eventually achieving vigorous antitumor and recurrence resistance. This study proposes an unsophisticated and versatile strategy to significantly improve PDT efficacy for enhancing systemic antitumor immunity and potentially extending it to multiple cancers., (© 2024 Wiley‐VCH GmbH.)

Bladder cancer is a type of urologic malignancy that exhibits significant morbidity, mortality, and treatment costs. Inhibition of heat shock protein 90 (HSP90) activity has been a promising pharmacological strategy for blocking of bladder cancer pathogenesis. BIIB021 is a next-generation HSP90 inhibitor which interrupts ATP hydrolysis process of HSP90 and inhibits the stabilization and correct folding of client proteins. In current study, we aimed to investigate the molecular mechanism of the anticancer activity of BIIB021 in human bladder cancer T24 cells. Our results revealed that nanomolar concentration of BIIB021 decreased viability of T24 cell. BIIB021 downregulated HSP90 expression in T24 cells and inhibited the refolding activity of luciferase in the presence of T24 cell lysate. PCR array data indicated a significant alteration in transcript levels of cancer-related genes involved in metastases, apoptotic cell death, cell cycle, cellular senescence, DNA damage and repair mechanisms, epithelial-to-mesenchymal transition, hypoxia, telomeres and telomerase, and cancer metabolism pathways in T24 cells. All findings hypothesize that BIIB021 could exhibit as effective HSP90 inhibitor in the future for treatment of bladder cancer patients., (© 2024. The Author(s).)

Heat shock protein 90 (HSP90) is one of the most attractive targets for research on cancer treatment, and nowadays, many studies carried out for the development of effective HSP90 inhibitors. In the current study, recently published ten natural compounds have been investigated using computer aided drug design (CADD) approach. The study consists of three parts; (1) density functional theory (DFT) calculations including geometry optimizations, vibrational analyses, and molecular electrostatic potential (MEP) map calculations, (2) molecular docking and molecular dynamics (MD) simulations, and (3) binding energy calculations. In DFT calculations, Becke three-parameter hybrid functional with Lee-Yang-Parr correlation functional (B3LYP) and 6-31 + G(d,p) basis set were used. After performing molecular docking calculations, top-scoring ligand-receptor complexes were subjected to MD simulations for 100 ns to investigate the stability of the ligand-receptor complexes and the interactions in more detail. Finally, in binding energy calculations molecular mechanics with Poisson-Boltzmann surface area (MM-PBSA) method was used. The results showed that five of the investigated ten natural compounds have higher binding affinity to HSP90α than that of reference drug Geldanamycin, and could be promising compounds for future studies.Communicated by Ramaswamy H. Sarma.

Non-alcoholic steatohepatitis (NASH) is characterized by liver inflammation, fat accumulation, and collagen deposition. Due to the limited availability of effective treatments, there is a pressing need to develop innovative strategies. Given the complex nature of the disease, employing combination approaches is essential. Hedgehog signaling has been recognized as potentially promoting NASH, and cholesterol can influence this signaling by modifying the conformation of PTCH1 and SMO activity. HSP90 plays a role in the stability of SMO and GLI proteins. We revealed significant positive correlations between Hedgehog signaling proteins (Shh, SMO, GLI1, and GLI2) and both cholesterol and HSP90 levels. Herein, we investigated the novel combination of the cholesterol-lowering agent lovastatin and the HSP90 inhibitor PU-H71 in vitro and in vivo. The combination demonstrated a synergy score of 15.09 and an MSA score of 22.85, as estimated by the ZIP synergy model based on growth inhibition rates in HepG2 cells. In a NASH rat model induced by thioacetamide and a high-fat diet, this combination therapy extended survival, improved liver function and histology, and enhanced antioxidant defense. Additionally, the combination exhibited anti-inflammatory and anti-fibrotic potential by influencing the levels of TNF-α, TGF-β, TIMP-1, and PDGF-BB. This effect was evident in the suppression of the Col1a1 gene expression and the levels of hydroxyproline and α-SMA. These favorable outcomes may be attributed to the combination's potential to inhibit key Hedgehog signaling molecules. In conclusion, exploring the applicability of this combination contributes to a more comprehensive understanding and improved management of NASH and other fibrotic disorders., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Deep penetration and downregulation of heat shock protein (HSP) expression in multimodal synergistic therapy are promising approaches for curing cancer in clinical trials. However, free small-molecule drugs and most drug vehicles have a low delivery efficiency deep into the tumor owing to poor drug penetration and hypoxic conditions at the tumor site. In this study, the objective is to use reactive oxygen species (ROS)-responsive supramolecular gels co-loaded with the photosensitizer Zn(II) phthalocyanine tetrasulfonic acid (ZnPCS 4 ) and functionalized tetrahedral DNA (TGSAs) (G@P/TGSAs) to enhance deep tissue and cell penetration and block the HSP90 pathway for chemo- photodynamic therapy (PDT) - photothermal therapy (PTT) trimodal synergistic therapy. The (G@P/TGSAs) are injected in situ into the tumor to release ZnPCS 4 and TGSAs under high ROS concentrations originating from both the tumor and PDT. TGSAs penetrate deeply into tumor tissues and augment photothermal therapy by inhibiting the HSP90 pathway. Proteomics show that HSP-related proteins and molecular chaperones are inhibited/activated, inhibiting the HSP90 pathway. Simultaneously, the TGSA-regulated apoptotic pathway is activated. In vivo study demonstrates efficient tumor penetration and excellent trimodal synergistic therapy (45% tumor growth inhibition)., (© 2024 The Authors. Advanced Science published by Wiley‐VCH GmbH.)

Opioids are the gold standard for the treatment of chronic pain but are limited by adverse side effects. In our earlier work, we showed that Heat shock protein 90 (Hsp90) has a crucial role in regulating opioid signaling in spinal cord; Hsp90 inhibition in spinal cord enhances opioid anti-nociception. Building on these findings, we injected the non-selective Hsp90 inhibitor KU-32 by the intrathecal route into male and female CD-1 mice, showing that morphine anti-nociceptive potency was boosted by 1.9-3.5-fold in acute and chronic pain models. At the same time, tolerance was reduced from 21-fold to 2.9 fold and established tolerance was rescued, while the potency of constipation and reward was unchanged. These results demonstrate that spinal Hsp90 inhibition can improve the therapeutic index of morphine. However, we also found that systemic non-selective Hsp90 inhibition blocked opioid pain relief. To avoid this effect, we used selective small molecule inhibitors and CRISPR gene editing to identify 3 Hsp90 isoforms active in spinal cord (Hsp90α, Hsp90β, and Grp94) while only Hsp90α was active in brain. We thus hypothesized that a systemically delivered selective inhibitor to Hsp90β or Grp94 could selectively inhibit spinal cord Hsp90 activity, resulting in enhanced opioid therapy. We tested this hypothesis using intravenous delivery of KUNB106 (Hsp90β) and KUNG65 (Grp94), showing that both drugs enhanced morphine anti-nociceptive potency while rescuing tolerance. Together, these results suggest that selective inhibition of spinal cord Hsp90 isoforms is a novel, translationally feasible strategy to improve the therapeutic index of opioids., (© 2024. The Author(s).)

Introduction: Activated hepatic stellate cells (HSCs) are the primary effector cells in hepatic fibrosis, over depositing extracellular matrix (ECM) proteins. Our previous work found oridonin analog CYD0682 attenuates proliferation, Transforming Growth Factor β (TGFβ)-induced signaling, and ECM production in immortalized HSCs. The underlying mechanism behind these reductions is unclear. The Signal Transduction and Activator of Transcription 3 (STAT3) pathway plays a central role in HSC activation and has been found to be overexpressed in models of hepatic injury. In this study, we will examine the effect of CYD0682 on STAT3 signaling., Methods: Immortalized human (LX-2) and rat (HSC-T6) HSC lines were treated with CYD0682 or Tanespimycin (17-AAG) with or without TGF-β. Nuclear and cytosolic proteins were extracted. Protein expression was analyzed with Western blot. DNA binding activity was assessed with STAT3 DNA Binding ELISA. Cell viability was assessed with Alamar blue assay., Results: CYD0682 treatment inhibited STAT3 phosphorylation at tyrosine 705 in a dose-dependent manner in LX-2 and HSC-T6 cells. STAT3 DNA binding activity and STAT3 regulated protein c-myc were significantly decreased by CYD0682. Notably, TGFβ-induced STAT3 phosphorylation and ECM protein expression were inhibited by CYD0682. STAT3 is reported to be a Heat Shock Protein 90 (HSP90) client protein. Notably, CYD0682 attenuated the expression of endogenous STAT3 and other HSP90 client proteins FAK, IKKα, AKT and CDK9. HSP90 specific inhibitor 17-AAG suppressed endogenous and TGFβ-induced STAT3 phosphorylation and ECM protein production., Conclusions: CYD0682 attenuates endogenous and TGFβ-induced STAT3 activation and ECM production via an HSP90 dependent pathway in HSCs. Further study of this pathway may present new targets for therapeutic intervention in hepatic fibrosis., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background/aim: Breast cancer is the most prevalent form of cancer among women worldwide, with a high mortality rate. While the most common cause of breast cancer death is metastasis, there is currently no potential treatment for patients at the metastatic stage. The present study investigated the potential of using a combination of HSP90 and mTOR inhibitor in the treatment of breast cancer cell growth, migration, and invasion., Materials and Methods: Gene Expression Profiling Interactive Analysis (GEPIA) was used to investigate the gene expression profiles. Western blot analysis and fluorescence staining were used for protein expression and localization, respectively. MTT, wound healing, and transwell invasion assays were used for cell proliferation, migration, and invasion, respectively., Results: GEPIA demonstrated that HSP90 expression was significantly higher in breast invasive carcinoma compared to other tumor types, and this expression correlated with mTOR levels. Treatment with 17-AAG, an HSP90 inhibitor, and Torkinib, an mTORC1/2 inhibitor, significantly inhibited cell proliferation. Moreover, combination treatment led to down-regulation of AKT. Morphological changes revealed a reduction in F-actin intensity, a marked reduction of YAP, with interference in nuclear localization., Conclusion: Targeting HSP90 and mTOR has the potential to suppress breast cancer cell growth and progression by disrupting AKT signaling and inhibiting F-actin polymerization. This combination treatment may hold promise as a therapeutic strategy for breast cancer treatment that ameliorates adverse effects of a single treatment., (Copyright © 2024 International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)