Inhibiting protein-protein interactions of Hsp90 as a novel approach for targeting cancer

Hiding in plain sight: Optimizing topoisomerase IIα inhibitors into Hsp90β selective binders

Due to their impact on several oncogenic client proteins, the Hsp90 family of chaperones has been widely studied for the development of potential anticancer agents. Although several Hsp90 inhibitors have entered clinical trials, most were unsuccessful because they induced a heat shock response (HSR). This issue can be circumvented by using isoform-selective inhibitors, but the high similarity in the ATP-binding sites between the isoforms presents a challenge. Given that Hsp90 shares a conserved Bergerat fold with bacterial DNA gyrase B and human topoisomerase IIα, we repurposed our ATP-competitive inhibitors of these two proteins for Hsp90 inhibition. We virtually screened a library of in-house inhibitors and identified eleven hits for evaluation of Hsp90 binding. Among these, compound 11 displayed low micromolar affinity for Hsp90 and demonstrated a 12-fold selectivity for Hsp90β over its closest isoform, Hsp90α. Out of 29 prepared analogs, 16 showed a preference for Hsp90β over Hsp90α. Furthermore, eleven of these compounds inhibited the growth of several cancer cell lines in vitro. Notably, compound 24e reduced intracellular levels of Hsp90 client proteins in MCF-7 cells, leading to cell cycle arrest in the G0/G1 phase without inducing HSR. This inhibitor exhibited at least a 27-fold preference for Hsp90β and was selective against topoisomerase IIα, a panel of 22 representative protein kinases, and proved to be non-toxic in a zebrafish larvae toxicology model. Finally, molecular modeling, corroborated by STD NMR studies, and the binding of 24e to the S52A mutant of Hsp90α confirmed that the serine to alanine switch drives the selectivity between the two cytoplasmic isoforms.

Discovery of indazole inhibitors for heat shock protein 90 as anti-cancer agents

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 IC50 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.

Targeting HSP90 for Cancer Therapy: Current Progress and Emerging Prospects

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.

Small molecule inhibitors targeting heat shock protein 90: An updated review

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.

Discovery of new Hsp90-Cdc37 protein-protein interaction inhibitors: in silico screening and optimization of anticancer activity

The interaction between heat shock protein 90 (Hsp90) and Hsp90 co-chaperone cell-division cycle 37 (Cdc37) is crucial for the folding and maturation of several oncogenic proteins, particularly protein kinases. This makes the inhibition of this protein-protein interaction (PPI) an interesting target for developing new anticancer compounds. However, due to the large interaction surface, developing PPI inhibitors is challenging. In this work, we describe the discovery of new Hsp90-Cdc37 PPI inhibitors using a ligand-based virtual screening approach. Initial hit compounds showed Hsp90 binding, resulting in anticancer activity in the MCF-7 breast cancer cell line. To optimize their antiproliferative effect, 35 analogs were prepared. Binding affinity for Hsp90 was determined for the most promising compounds, 8c (K d = 70.8 μM) and 13g (K d = 73.3 μM), both of which interfered with the binding of Cdc37 to Hsp90. This resulted in anticancer activity against Ewing sarcoma (SK-N-MC), breast cancer (MCF-7), and leukemia (THP-1) cell lines in vitro. Furthermore, compounds 8c and 13g demonstrated the ability to induce apoptosis in the Ewing sarcoma cell line and caused a decrease in the levels of several known Hsp90 client proteins in MCF-7 cells, all without inducing the heat shock response.

Heat shock proteins as hallmarks of cancer: insights from molecular mechanisms to therapeutic strategies

Heat shock proteins are essential molecular chaperones that play crucial roles in stabilizing protein structures, facilitating the repair or degradation of damaged proteins, and maintaining proteostasis and cellular functions. Extensive research has demonstrated that heat shock proteins are highly expressed in cancers and closely associated with tumorigenesis and progression. The "Hallmarks of Cancer" are the core features of cancer biology that collectively define a series of functional characteristics acquired by cells as they transition from a normal state to a state of tumor growth, including sustained proliferative signaling, evasion of growth suppressors, resistance to cell death, enabled replicative immortality, the induction of angiogenesis, and the activation of invasion and metastasis. The pivotal roles of heat shock proteins in modulating the hallmarks of cancer through the activation or inhibition of various signaling pathways has been well documented. Therefore, this review provides an overview of the roles of heat shock proteins in vital biological processes from the perspective of the hallmarks of cancer and summarizes the small-molecule inhibitors that target heat shock proteins to regulate various cancer hallmarks. Moreover, we further discuss combination therapy strategies involving heat shock proteins and promising dual-target inhibitors to highlight the potential of targeting heat shock proteins for cancer treatment. In summary, this review highlights how targeting heat shock proteins could regulate the hallmarks of cancer, which will provide valuable information to better elucidate and understand the roles of heat shock proteins in oncology and the mechanisms of cancer occurrence and development and aid in the development of more efficacious and less toxic novel anticancer agents.

Hsp90 Promotes Gastric Cancer Cell Metastasis and Stemness by Regulating the Regional Distribution of Glycolysis-Related Metabolic Enzymes in the Cytoplasm

Heat-shock protein 90 (Hsp90) plays a crucial role in tumorigenesis and tumor progression; however, its mechanism of action in gastric cancer (GC) remains unclear. Here, the role of Hsp90 in GC metabolism is the focus of this research. High expression of Hsp90 in GC tissues can interact with glycolysis, collectively affecting prognosis in clinical samples. Both in vitro and in vivo experiments demonstrate that Hsp90 is able to regulate the migration and stemness properties of GC cells. Metabolic phenotype analyses indicate that Hsp90 influences glycolytic metabolism. Mechanistically, Hsp90 interacts with glycolysis-related enzymes, forming multienzyme complexes to enhance glycolysis efficiency and yield. Additionally, Hsp90 binds to cytoskeleton-related proteins, regulating the regional distribution of glycolytic enzymes at the cell margin and lamellar pseudopods. This effect could lead to a local increase in efficient energy supply from glycolysis, further promoting epithelial-mesenchymal transition (EMT) and metastasis. In summary, Hsp90, through its interaction with metabolic enzymes related to glycolysis, forms multi-enzyme complexes and regulates regional distribution of glycolysis by dynamic cytoskeletal adjustments, thereby promoting the migration and stemness of GC cells. These conclusions also support the potential for a combined targeted approach involving Hsp90, glycolysis, and the cytoskeleton in clinical therapy.

Benzothiazole derivatives in the design of antitumor agents

Benzothiazoles are a class of heterocycles with multiple applications as anticancer, antibiotic, antiviral, and anti-inflammatory agents. Benzothiazole is a privileged scaffold in drug discovery programs for modulating a variety of biological functions. This review focuses on the design and synthesis of new benzothiazole derivatives targeting hypoxic tumors. Cancer is a major health problem, being among the leading causes of death. Tumor-hypoxic areas promote proliferation, malignancy, and resistance to drug treatment, leading to the dysregulation of key signaling pathways that involve drug targets such as vascular endothelial growth factor, epidermal growth factor receptor, hepatocyte growth factor receptor, dual-specificity protein kinase, cyclin-dependent protein kinases, casein kinase 2, Rho-related coil formation protein kinase, tunica interna endothelial cell kinase, cyclooxygenase-2, adenosine kinase, lysophosphatidic acid acyltransferases, stearoyl-CoA desaturase, peroxisome proliferator-activated receptors, thioredoxin, heat shock proteins, and carbonic anhydrase IX/XII. In turn, they regulate angiogenesis, proliferation, differentiation, and cell survival, controlling the cell cycle, inflammation, the immune system, and metabolic alterations. A wide diversity of benzothiazoles were reported over the last years to interfere with various proteins involved in tumorigenesis and, more specifically, in hypoxic tumors. Many hypoxic targets are overexpressed as a result of the hypoxia-inducible factor activation cascade and may not be present in normal tissues, providing a potential strategy for selectively targeting hypoxic cancers.

Structural Characterization of Heat Shock Protein 90β and Molecular Interactions with Geldanamycin and Ritonavir: A Computational Study

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.

Targeted delivery of HSP90 inhibitors for efficient therapy of CD44-positive acute myeloid leukemia and solid tumor-colon cancer

Heat shock protein 90 (HSP90) is overexpressed in numerous cancers, promotes the maturation of numerous oncoproteins and facilitates cancer cell growth. Certain HSP90 inhibitors have entered clinical trials. Although less than satisfactory clinical effects or insurmountable toxicity have compelled these trials to be terminated or postponed, these results of preclinical and clinical studies demonstrated that the prospects of targeting therapeutic strategies involving HSP90 inhibitors deserve enough attention. Nanoparticulate-based drug delivery systems have been generally supposed as one of the most promising formulations especially for targeting strategies. However, so far, no active targeting nano-formulations have succeeded in clinical translation, mainly due to complicated preparation, complex formulations leading to difficult industrialization, incomplete biocompatibility or nontoxicity. In this study, HSP90 and CD44-targeted A6 peptide functionalized biomimetic nanoparticles (A6-NP) was designed and various degrees of A6-modification on nanoparticles were fabricated to evaluate targeting ability and anticancer efficiency. With no excipients, the hydrophobic HSP90 inhibitor G2111 and A6-conjugated human serum albumin could self-assemble into nanoparticles with a uniform particle size of approximately 200 nm, easy fabrication, well biocompatibility and avoidance of hepatotoxicity. Besides, G2111 encapsulated in A6-NP was only released less than 5% in 12 h, which may avoid off-target cell toxicity before entering into cancer cells. A6 peptide modification could significantly enhance uptake within a short time. Moreover, A6-NP continues to exert the broad anticancer spectrum of Hsp90 inhibitors and displays remarkable targeting ability and anticancer efficacy both in hematological malignancies and solid tumors (with colon tumors as the model cancer) both in vitro and in vivo. Overall, A6-NP, as a simple, biomimetic and active dual-targeting (CD44 and HSP90) nanomedicine, displays high potential for clinical translation.

Heat Shock Proteins, a Double-Edged Sword: Significance in Cancer Progression, Chemotherapy Resistance and Novel Therapeutic Perspectives

Heat shock proteins (Hsps) are involved in one of the adaptive mechanisms protecting cells against environmental and metabolic stress. Moreover, the large role of these proteins in the carcinogenesis process, as well as in chemoresistance, was noticed. This review aims to draw attention to the possibilities of using Hsps in developing new cancer therapy methods, as well as to indicate directions for future research on this topic. In order to discuss this matter, a thorough review of the latest scientific literature was carried out, taking into account the importance of selected proteins from the Hsp family, including Hsp27, Hsp40, Hsp60, Hsp70, Hsp90 and Hsp110. One of the more characteristic features of all Hsps is that they play a multifaceted role in cancer progression, which makes them an obvious target for modern anticancer therapy. Some researchers emphasize the importance of directly inhibiting the action of these proteins. In turn, others point to their possible use in the design of cancer vaccines, which would work by inducing an immune response in various types of cancer. Due to these possibilities, it is believed that the use of Hsps may contribute to the progress of oncoimmunology, and thus help in the development of modern anticancer therapies, which would be characterized by higher effectiveness and lower toxicity to the patients.

XQZ3, a Chlorella pyrenoidosa polysaccharide suppresses cancer progression by restraining mitochondrial bioenergetics via HSP90/AKT signaling pathway

The mitochondria are known to exert significant influence on various aspects of cancer cell physiology. The suppression of mitochondrial function represents a novel avenue for the advancement of anti-cancer pharmaceuticals. The heat shock protein HSP90 functions as a versatile regulator of mitochondrial metabolism in cancer cells, rendering as a promising target for anticancer interventions. In this work, a novel acid polysaccharide named as XQZ3 was extracted from Chlorella pyrenoidosa and purified by DEAE-cellulose and gel-filtration chromatography. The structural characteristic of XQZ3 was evaluated by monosaccharides composition, methylation analysis, TEM, FT-IR, and 2D-NMR. It was found that XQZ3 with a molecular weight of 29.13 kDa was a complex branched polysaccharide with a backbone mainly composed of galactose and mannose. It exhibited good antitumor activity in vitro and in vivo by patient-derived 3D organoid models and patient-derived xenografts models. The mechanistic investigations revealed that XQZ3 specifically interacted with HSP90, impeding the activation of the HSP90/AKT/mTOR signaling cascade. This, in turn, led to the induction of mitochondrial dysfunction, autophagy, and apoptosis, ultimately resulting in the demise of cancer cells due to nutrient deprivation. This study offers a comprehensive theoretical foundation for the advancement of XQZ3, a novel polysaccharide inhibitor targeting HSP90, with potential as an effective therapeutic agent against cancer.

Heat shock protein 90: biological functions, diseases, and therapeutic targets

Heat shock protein 90 (Hsp90) is a predominant member among Heat shock proteins (HSPs), playing a central role in cellular protection and maintenance by aiding in the folding, stabilization, and modification of diverse protein substrates. It collaborates with various co-chaperones to manage ATPase-driven conformational changes in its dimer during client protein processing. Hsp90 is critical in cellular function, supporting the proper operation of numerous proteins, many of which are linked to diseases such as cancer, Alzheimer's, neurodegenerative conditions, and infectious diseases. Recognizing the significance of these client proteins across diverse diseases, there is a growing interest in targeting Hsp90 and its co-chaperones for potential therapeutic strategies. This review described biological background of HSPs and the structural characteristics of HSP90. Additionally, it discusses the regulatory role of heat shock factor-1 (HSF-1) in modulating HSP90 and sheds light on the dynamic chaperone cycle of HSP90. Furthermore, the review discusses the specific contributions of HSP90 in various disease contexts, especially in cancer. It also summarizes HSP90 inhibitors for cancer treatment, offering a thoughtful analysis of their strengths and limitations. These advancements in research expand our understanding of HSP90 and open up new avenues for considering HSP90 as a promising target for therapeutic intervention in a range of diseases.

Small-molecule dual inhibitors targeting heat shock protein 90 for cancer targeted therapy

Heat shock protein 90, also known as Hsp90, is an extensively preserved molecular chaperone that performs a critical function in organizing various biological pathways and cellular operations. As a potential drug target, Hsp90 is closely linked to cancer. Hsp90 inhibitors are a class of drugs that have been extensively studied in preclinical models and have shown promise in a variety of diseases, especially cancer. However, Hsp90 inhibitors have encountered several challenges in clinical development, such as low efficacy, toxicity, or drug resistance, few Hsp90 small molecule inhibitors have been approved worldwide. Nonetheless, combining Hsp90 inhibitors with other tumor inhibitors, such as HDAC inhibitors, tubulin inhibitors, and Topo II inhibitors, has been shown to have synergistic antitumor effects. Consequently, the development of Hsp90 dual-target inhibitors is an effective strategy in cancer treatment, as it enhances potency while reducing drug resistance. This article provides an overview of Hsp90's domain structure and biological functions, as well as a discussion of the design, discovery, and structure-activity relationships of Hsp90 dual inhibitors, aiming to provide insights into clinical drug research from a medicinal chemistry perspective and discover novel Hsp90 dual inhibitors.

Development of VER-50589 analogs as novel Hsp90 inhibitors

As an important target for tumor therapy, heat shock protein 90 has attracted tremendous attention. Through structure analysis, we rationally designed three analogs of VER-50589 which is a known and potent Hsp90 inhibitor. Target inhibitory activity result showed that one compound dubbed as 12-1 exhibited strong inhibitory activity against Hsp90 with an IC50 value of 9 nM. In tumor cell viability experiment, compound 12-1 robustly repressed the proliferation against six human tumor cells with IC50 values all in nanomolar range scoring over VER-50589 and geldanamycin. 12-1 was able to induce apoptosis of tumor cells and arrest the tumor cell cycle in G0/G1 phase. Meanwhile, western blot results showed that 12-1 could significantly downregulated the expression of two Hsp90 client proteins CDK4 and HER2. Finally, molecular dynamic simulation showed that compound 12-1 could fit well with ATP binding site on N-terminal of Hsp90.

2-Aminobenzothiazoles in anticancer drug design and discovery

Cancer is one of the major causes of mortality and morbidity worldwide. Substantial research efforts have been made to develop new chemical entities with improved anticancer efficacy. 2-Aminobenzothiazole is an important class of heterocycles containing one sulfur and two nitrogen atoms, which is associated with a broad spectrum of medical and pharmacological activities, including antitumor, antibacterial, antimalarial, anti-inflammatory, and antiviral activities. In recent years, an extraordinary collection of potent and low-toxicity 2-aminobenzothiazole compounds have been discovered as new anticancer agents. Herein, we provide a comprehensive review of this class of compounds based on their activities against tumor-related proteins, including tyrosine kinases (CSF1R, EGFR, VEGFR-2, FAK, and MET), serine/threonine kinases (Aurora, CDK, CK, RAF, and DYRK2), PI3K kinase, BCL-XL, HSP90, mutant p53 protein, DNA topoisomerase, HDAC, NSD1, LSD1, FTO, mPGES-1, SCD, hCA IX/XII, and CXCR. In addition, the anticancer potentials of 2-aminobenzothiazole-derived chelators and metal complexes are also described here. Moreover, the design strategies, mechanism of actions, structure-activity relationships (SAR) and more advanced stages of pre-clinical development of 2-aminobenzothiazoles as new anticancer agents are extensively reviewed in this article. Finally, the examples that 2-aminobenzothiazoles showcase an advantage over other heterocyclic systems are also highlighted.

Targeting cellular senescence with senotherapeutics: senolytics and senomorphics

The concept of geroscience is that since ageing is the greatest risk factor for many diseases and conditions, targeting the ageing process itself will have the greatest impact on human health. Of the hallmarks of ageing, cellular senescence has emerged as a druggable therapeutic target for extending healthspan in model organisms. Cellular senescence is a cell state of irreversible proliferative arrest driven by different types of stress, including oncogene-induced stress. Many senescent cells (SnCs) develop a senescent-associated secretory phenotype (SASP) comprising pro-inflammatory cytokines, chemokines, proteases, bioactive lipids, inhibitory molecules, extracellular vesicles, metabolites, lipids and other factors, able to promote chronic inflammation and tissue dysfunction. SnCs up-regulate senescent cell anti-apoptotic pathways (SCAPs) that prevent them from dying despite the accumulation of damage to DNA and other organelles. These SCAPs and other pathways altered in SnCs represent therapeutic targets for the development of senotherapeutic drugs that induce selective cell death of SnCs, specifically termed senolytics or suppress markers of senescence, in particular the SASP, termed senomorphics. Here, we review the current state of the development of senolytics and senomorphics for the treatment of age-related diseases and disorders and extension of healthy longevity. In addition, the challenges of documenting senolytic and senomorphic activity in pre-clinical models and the current state of the clinical application of the different senotherapeutics will be discussed.

Hsp70/Hsp90 Organising Protein (Hop): Coordinating Much More than Chaperones

The Hsp70/Hsp90 organising protein (Hop, also known as stress-inducible protein 1/STI1/STIP1) has received considerable attention for diverse cellular functions in both healthy and diseased states. There is extensive evidence that intracellular Hop is a co-chaperone of the major chaperones Hsp70 and Hsp90, playing an important role in the productive folding of Hsp90 client proteins, although recent evidence suggests that eukaryotic Hop is regulatory within chaperone complexes rather than essential. Consequently, Hop is implicated in many key signalling pathways, including aberrant pathways leading to cancer. Hop is also secreted, and it is now well established that Hop interacts with the prion protein, PrP^C, to mediate multiple signalling events. The intracellular and extracellular forms of Hop most likely represent two different isoforms, although the molecular determinants of these divergent functions are yet to be identified. There is also a growing body of research that reports the involvement of Hop in cellular activities that appear independent of either chaperones or PrP^C. While the various cellular functions of Hop have been described, its biological function remains elusive. However, recent knockout studies in mammals suggest that Hop has an important role in embryonic development. This review provides a critical overview of the latest molecular, cellular and biological research on Hop, critically evaluating its function in healthy systems and how this function is adapted in diseased states.

Heterocyclic Compounds as Hsp90 Inhibitors: A Perspective on Anticancer Applications

Heat shock proteins (Hsps) have garnered special attention in cancer therapy as molecular chaperones with regulatory/mediatory effects on folding, maintenance/stability, maturation, and conformation of proteins as well as their effects on prevention of protein aggregation. Hsp90 ensures the stability of various client proteins needed for the growth of cells or the survival of tumor cells; therefore, they are overexpressed in tumor cells and play key roles in carcinogenesis. Accordingly, Hsp90 inhibitors are recognized as attractive therapeutic agents for investigations pertaining to tumor suppression. Natural Hsp90 inhibitors comprising geldanamycin (GM), reclaimed analogs of GM including 17-AAG and DMAG, and radicicol, a natural macrocyclic antifungal, are among the first potent Hsp90 inhibitors. Herein, recently synthesized heterocyclic compounds recognized as potent Hsp90 inhibitors are reviewed along with the anticancer effects of heterocyclic compounds, comprising purine, pyrazole, triazine, quinolines, coumarin, and isoxazoles molecules.

Heat Shock Protein 90 as Therapeutic Target for CVDs and Heart Ageing

Cardiovascular diseases (CVDs) are the leading cause of death globally, representing approximately 32% of all deaths worldwide. Molecular chaperones are involved in heart protection against stresses and age-mediated accumulation of toxic misfolded proteins by regulation of the protein synthesis/degradation balance and refolding of misfolded proteins, thus supporting the high metabolic demand of the heart cells. Heat shock protein 90 (HSP90) is one of the main cardioprotective chaperones, represented by cytosolic HSP90a and HSP90b, mitochondrial TRAP1 and ER-localised Grp94 isoforms. Currently, the main way to study the functional role of HSPs is the application of HSP inhibitors, which could have a different way of action. In this review, we discussed the recently investigated role of HSP90 proteins in cardioprotection, atherosclerosis, CVDs development and the involvements of HSP90 clients in the activation of different molecular pathways and signalling mechanisms, related to heart ageing.

A small-molecule compound D6 overcomes EGFR-T790M-mediated resistance in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is a deadly and highly prevalent malignancy. Targeting activated-EGFR mutations in NSCLC via EGFR tyrosine kinase inhibitor (EGFR-TKI) initially achieves a profound therapeutic response, but resistance frequently evolves, reducing treatment options. Here, we present a small-molecule compound D6 which selectively inhibits tumor cell growth and migration in NSCLC cells with EGFR-TKI-resistant T790M-EGFR-activated mutations (T790M-EGFR-AM), e.g., L858R/T790M, 19Del/T790M and L858R/T790M/C797S. D6 mimics a natural product isolated from the roots of Codonopsis pilosula and selectively competes with T790M-EGFR-AM to bind to HSP90, thus facilitating the ubiquitination dependent proteasomal degradation of T790M-EGFR-AM. By contrast, D6 has little impact on typical HSP90 chaperone activity, suggesting low systemic toxicity. Promisingly, D6 combined with erlotinib or osimertinib shows efficacy in overcoming the EGFR-TKIs-resistance in NSCLCs. Our study raises an alternative strategy to overcome T790M-mediated EGFR-TKI resistance in NSCLC via targeting the protein-protein interaction of HSP90 and T790M-EGFR by intervention with D6.

Development of Computational Approaches with a Fragment-Based Drug Design Strategy: In Silico Hsp90 Inhibitors Discovery

A semi-exhaustive approach and a heuristic search algorithm use a fragment-based drug design (FBDD) strategy for designing new inhibitors in an in silico process. A deconstruction reconstruction process uses a set of known Hsp90 ligands for generating new ones. The deconstruction process consists of cutting off a known ligand in fragments. The reconstruction process consists of coupling fragments to develop a new set of ligands. For evaluating the approaches, we compare the binding energy of the new ligands with the known ligands.

Pseudocedrela kotschyi: a review of ethnomedicinal uses, pharmacology and phytochemistry

CONTEXT

Pseudocedrela kotschyi (Schweinf) Harms (Meliaceae) is an important medicinal plant found in tropical and subtropical countries of Africa. Traditionally, P. kotschyi is used in the treatment of various diseases including diabetes, malaria, abdominal pain and diarrhoea.

OBJECTIVE

To provide an overview of traditional medicinal claims, pharmacological properties, and phytochemical principles of P. kotschyi as a basis for its clinical applications and further research and development of new drugs.

METHODS

Through interpreting already published scientific manuscripts retrieved from different scientific search engines, namely, Medline, PubMed, EMBASE, Science Direct and Google scholar databases, an up-to-date review on the medicinal potentials of P. kotschyi from inception until September, 2020 was compiled. 'Pseudocedrela kotschyi', 'traditional uses', 'pharmacological properties' and 'chemical constituents' were used as search words.

RESULTS

At present, more than 30 chemical constituents have been isolated and identified from the root and stem bark of P. kotschyi, among which limonoids and triterpenes are the main active constituents. Based on prior research, P. kotschyi has been reported to possess anti-inflammatory, analgesic, antipyretic, anthelminthic, antimalaria, anti-leishmaniasis, anti-trypanosomiasis, hepatoprotective, antioxidant, antidiabetic, antidiarrheal, antimicrobial, and anticancer effects.

CONCLUSIONS

P. kotschyi is reported to be effective in treating a variety of diseases. Current phytochemical and pharmacological studies mainly focus on antimalaria, anti-leishmaniasis, anti-trypanosomiasis and anticancer potential of the root and stem bark of P. kotschyi. Although experimental data support the beneficial medicinal properties of this plant, there is still a paucity of information on its toxicity profile. Nonetheless, this review provides the basis for future research work.

Review of the development of BTK inhibitors in overcoming the clinical limitations of ibrutinib

Bruton's tyrosine kinase (BTK) regulates multiple important signaling pathways and plays a key role in the proliferation, survival, and differentiation of B-lineage cells and myeloid cells. BTK is a promising target for the treatment of hematologic malignancies. Ibrutinib, the first-generation BTK inhibitor, was approved to treat several B-cell malignancies. Despite the remarkable potency and efficacy of ibrutinib against various lymphomas and leukemias in the clinics, there are also some clinical limitations, such as off-target toxicities and primary/acquired drug resistance. As strategies to overcome these challenges, second- and third-generation BTK inhibitors, BTK-PROTACs, as well as combination therapies have been explored. In this review, we summarize clinical developments of the first-, second- and third-generation BTK inhibitors, as well as recent advances in BTK-PROTACs and ibrutinib-based combination therapies.

Recent advances in the discovery of senolytics

The demonstration in model organisms that cellular senescence drives aging and age-related diseases has led to widespread efforts to identify compounds able to selectively kill senescent cells, termed senolytics. Approaches used to identify senolytics include bioinformatic analysis of senescent cell anti-apoptotic pathways (SCAPs) for drug development and screening of drugs libraries on different senescent cell types in culture. Alternatively, cytotoxic compounds can be made specific to senescent cells through a prodrug strategy such as linking the compound to a galactose moiety where toxicity is activated by lysosomal β-galactosidase. Identified senolytics can then be optimized through medicinal chemistry or linking to E3 targeting moieties to facilitate proteolysis of their targets. This review will provide an overview of approaches to identify senolytics and an update of the classes of senolytics identified to date.

Targeting Chaperone/Co-Chaperone Interactions with Small Molecules: A Novel Approach to Tackle Neurodegenerative Diseases

The dysfunction of the proteostasis network is a molecular hallmark of neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and amyotrophic lateral sclerosis. Molecular chaperones are a major component of the proteostasis network and maintain cellular homeostasis by folding client proteins, assisting with intracellular transport, and interfering with protein aggregation or degradation. Heat shock protein 70 kDa (Hsp70) and 90 kDa (Hsp90) are two of the most important chaperones whose functions are dependent on ATP hydrolysis and collaboration with their co-chaperones. Numerous studies implicate Hsp70, Hsp90, and their co-chaperones in neurodegenerative diseases. Targeting the specific protein–protein interactions between chaperones and their particular partner co-chaperones with small molecules provides an opportunity to specifically modulate Hsp70 or Hsp90 function for neurodegenerative diseases. Here, we review the roles of co-chaperones in Hsp70 or Hsp90 chaperone cycles, the impacts of co-chaperones in neurodegenerative diseases, and the development of small molecules modulating chaperone/co-chaperone interactions. We also provide a future perspective of drug development targeting chaperone/co-chaperone interactions for neurodegenerative diseases.

Lamin-A interacting protein Hsp90 is required for DNA damage repair and chemoresistance of ovarian cancer cells

Ovarian cancer is the most malignant gynecologic cancer. Previous studies found that lamin-A was associated with DNA damage repair proteins but the underlying mechanism remains unclear. We speculate that this may be related to its interacting proteins, such as Hsp90. The aim of this study is to investigate the effects of Hsp90 on DNA damage repair and chemoresistance of ovarian cancer cells. In our research, co-immunoprecipitation (co-IP) and mass spectrometry (MS) were used to identify proteins interacting with lamin-A and the interaction domain. Next, the relationship between lamin-A and Hsp90 was explored by Western blotting (WB) and immunofluorescence staining. Then, effect of Hsp90 inhibition on DNA damage repair was assessed through detecting Rad50 and Ku80 by WB. Furthermore, to test the roles of 17-AAG on cell chemosensitivity, CCK-8 and colony formation assay were carried out. Meanwhile, IC50 of cells were calculated, followed by immunofluorescence to detect DNA damage. At last, the mouse xenograft model was used in determining the capacity of 17-AAG and DDP to suppress tumor growth and metastatic potential. The results showed that lamin-A could interact with Hsp90 via the domain of lamin-A1-430. Besides, the distribution of Hsp90 could be affected by lamin-A. After lamin-A knockdown, Hsp90 decreased in the cytoplasm and increased in the nucleus, suggesting that the interaction between lamin-A and Hsp90 may be related to the nucleocytoplasmic transport of Hsp90. Moreover, inhibition of Hsp90 led to an obvious decrease in the expression of DSBs (DNA double-strand break) repair proteins, as well as cell proliferation ability upon DDP treatment and IC50 of DDP, causing more serious DNA damage. In addition, the combination of 17-AAG and DDP restrained the growth of ovarian cancer efficiently in vivo and prolonged the survival time of tumor-bearing mice.

Discovery of a simplified deguelin analog as an HSP90 C-terminal inhibitor for HER2-positive breast cancer

A series of O-substituted analogs of the C-ring-truncated scaffold of deguelin designed as heat shock protein 90 (HSP90) C-terminal inhibitors were investigated as novel antitumor agents against human epidermal growth factor receptor 2 (HER2)-positive breast cancer. Among the synthesized compounds, compound 37 displayed significant inhibition in both trastuzumab-sensitive and trastuzumab-resistant breast cancer cells with little cytotoxicity to normal cells. Mechanistic studies of compound 37 carried out by HSP90α C-terminal inhibitor screening, the induction of the heat shock response and downregulation of HSP90 client proteins indicated that the antitumor activity of 37 in breast cancer cells could be attributed to the destabilization and inactivation of HSP90 client proteins by the binding of 37 to the C-terminal domain of HSP90. A molecular docking study of compound 37 with a HSP90 homology model indicated that its S-isomer fit well in the ATP binding site of the C-terminal domain, forming key interactions.

Ring-opening of five-membered heterocycles conjugated 4-isopropylresorcinol scaffold-based benzamides as HSP90 inhibitors suppressing tumor growth in vitro and in vivo

A series of ring-opened dihydroxybenzamides have been designed and synthesized as heat shock protein 90 inhibitors. One of derivatives, compound 6b ((N-ethyl-2,4-dihydroxy-5-isopropyl-N-(pyridin-3-yl)benzamide)) demonstrated remarkable antiproliferative activity against in human KRAS mutant A549 and EGFR T790 M mutant H1975 lung cancer cell lines with GI₅₀ values of 0.07 and 0.05 μM, respectively. It is also active against in other cancer cell lines, such as colorectal HCT116 (GI₅₀ = 0.09 μM), liver Hep3B (GI₅₀ = 0.20 μM) and breast MDA-MB-231 (GI₅₀ = 0.09 μM), and shows no evidence of toxicity in normal cell line. Compound 6b has an IC₅₀ of 110.18 nM in HSP90α inhibitory activity, slightly better than reference compound 1 (17-AAG, IC₅₀ = 141.62 nM) and achieves the degradation of multiple HSP90 client proteins in a dose- and time-dependent manner and downstream signaling of Akt in a concentration- and time-dependent manner in the human A549 lung cancer cell line. In the Boyden chamber assay, compound 6b can efficiently inhibit the migration of A549 cells when compared to the reference compound 1. It also induce significant activity through the apoptotic pathway. Treatment with 6b showed no vision toxicity (IC₅₀ > 10 μM) on 661w photoreceptor cells as compared to AUY922 (3a) with a 0.04 μM values of IC₅₀ and has no effect in hERG test. In a bidirectional Caco-2 permeability assay, compound 6b was classified as a highly permeable compound which is not a substrate of efflux transporters. In a pharmacokinetic study in rats, 6b showed an F = 17.8% of oral bioavailability. The effect of metabolic stability of compound 6b in human hepatocytes showed a T_1/2 of 67.59 min. Compound 6b (50 mg/kg, po, daily) exhibits antitumor activity with a 72% TGD (tumor growth delay) in human A549 lung xenograft. The combination of 6b and afatinib, orally administered, showed tumor growth suppression with 67.5% of TGI in lung H1975 xenograft model. Thus compound 6b is a lead compound for further development of potential agents to treat lung cancer.

Complex Crystal Structure Determination and in vitro Anti-non-small Cell Lung Cancer Activity of Hsp90 N Inhibitor SNX-2112

SNX-2112, as a promising anticancer lead compound targeting heat shock protein 90 (Hsp90), absence of complex crystal structure of Hsp90^N-SNX-2112 hindered further structural optimization and understanding on molecular interaction mechanism. Herein, a high-resolution complex crystal structure of Hsp90^N-SNX-2112 was successfully determined by X-ray diffraction, resolution limit, 2.14 Å, PDB ID 6LTK, and their molecular interaction was analyzed in detail, which suggested that SNX-2112 was well accommodated in the ATP-binding pocket to disable molecular chaperone activity of Hsp90, therefore exhibiting favorable inhibiting activity on three non–small cell lung cancer (NSCLC) cell lines (IC₅₀, 0.50 ± 0.01 μM for A549, 1.14 ± 1.11 μM for H1299, 2.36 ± 0.82 μM for H1975) by inhibited proliferation, induced cell cycle arrest, and aggravated cell apoptosis. SNX-2112 exhibited high affinity and beneficial thermodynamic changes during the binding process with its target Hsp90^N confirmed by thermal shift assay (TSA, ΔTm, and −9.51 ± 1.00°C) and isothermal titration calorimetry (K_d, 14.10 ± 1.60 nM). Based on the complex crystal structure and molecular interaction analysis, 32 novel SNX-2112 derivatives were designed, and 25 new ones displayed increased binding force with the target Hsp90^N verified by molecular docking evaluation. The results would provide new references and guides for anti-NSCLC new drug development based on the lead compound SNX-2112.

Anti-NSCLC activity in vitro of Hsp90N inhibitor KW-2478 and complex crystal structure determination of Hsp90N-KW-2478

KW-2478 is a promising anti-cancer lead compound targeting to the molecular chaperone heat shock protein 90 ^N (Hsp90^N). Absence of complex crystal structure of Hsp90^N-KW-2478, however, hampered further structure optimization of KW-2478 and understanding on the molecular interaction mechanism. Herein, a high-resolution complex crystal structure of Hsp90^N-KW-2478 was determined by X-ray diffraction (XRD, resolution limit: 1.59 Å; PDB ID: 6LT8) and their molecular interaction was analyzed in detail, which suggested that KW-2478 perfectly bound in the N-terminal ATP-binding pocket of Hsp90 to disable its molecular chaperone function, therefore suppressed or killed cancer cells. The results from thermal shift assay (TSA, ΔTm, 18.82 ± 0.51 °C) and isothermal titration calorimetry (ITC, K_d, 7.30 ± 2.20 nM) suggested that there is an intense binding force and favorable thermodynamic changes during the process of KW-2478 binding with Hsp90^N. Additionally, KW-2478 exhibited favorable anti-NSCLC activity in vitro, as it inhibited cell proliferation (IC₅₀, 8.16 μM for A549; 14.29 μM for H1975) and migration, induced cell cycle arrest and promoted apoptosis. Thirty-six novel KW-2478 derivatives were designed, based on the complex crystal structure and molecular interaction analysis of Hsp90^N-KW-2478 complex. Among them, twenty-two derivatives exhibited increased binding force with Hsp90^N evaluated by molecular docking assay. The results would provide new guidance for anti-NSCLC new drug development based on the lead compound KW-2478.

Priming with HDAC Inhibitors Sensitizes Ovarian Cancer Cells to Treatment with Cisplatin and HSP90 Inhibitors

Ovarian cancer is the fifth leading cause of cancer deaths. Chemoresistance, particularly against platinum compounds, contributes to a poor prognosis. Histone deacetylase inhibitors (HDACi) and heat shock protein 90 inhibitors (HSP90i) are known to modulate pathways involved in chemoresistance. This study investigated the effects of HDACi (panobinostat, LMK235) and HSP90i (luminespib, HSP990) on the potency of cisplatin in ovarian cancer cell lines (A2780, CaOV3, OVCAR3 and cisplatin-resistant sub-clones). Preincubation with HDACi increased the cytotoxic potency of HSP90i, whereas preincubation with HSP90i had no effect. Preincubation with HSP90i or HDACi 48h prior to cisplatin enhanced the cisplatin potency significantly in all cell lines via apoptosis induction and affected the expression of apoptosis-relevant genes and proteins. For CaOV3CisR and A2780CisR, a preincubation with HDACi for 48–72 h led to complete reversal of cisplatin resistance. Furthermore, permanent presence of HDACi in sub-cytotoxic concentrations prevented the development of cisplatin resistance in A2780. However, triple combinations of HDACi, HSP90i and cisplatin were not superior to dual combinations. Overall, priming with HDACi sensitizes ovarian cancer cells to treatment with HSP90i or cisplatin and has an influence on the development of cisplatin resistance, both of which may contribute to an improved ovarian cancer treatment.

2-((1-Phenyl-1H-1,2,3-triazol-4-yl)methyl)-2-azabicyclo[3.2.1]octan-3-one derivatives: Simplification and modification of aconitine scaffold for the discovery of novel anticancer agents

The molecular chaperone heat shock protein 90 (Hsp90) is a promising target for cancer therapy. Natural product aconitine is a potential Hsp90 inhibitor reported in our previous work. In this study, we designed and synthesized a series of 2-((1-phenyl-1H-1,2,3-triazol-4-yl)methyl)-2-azabicyclo[3.2.1]octan-3-one derivatives as potent Hsp90 inhibitors by simplifying and modifying aconitine scaffold. Among these compounds, 14t exhibited an excellent antiproliferative activity against LoVo cells with an IC₅₀ value of 0.02 μM and a significant Hsp90α inhibitory activity with an IC₅₀ value of 0.71 nM. Molecular docking studies provided a rational binding model of 14t in complex with Hsp90α. The following cell cycle and apoptosis assays revealed that compound 14t could arrest cell cycle at G1/S phase and induce cell apoptosis via up-regulation of bax and cleaved-caspase 3 protein expressions while inhibiting the expressions of bcl-2. Moreover, 14t could inhibit cell migration in LoVo and SW620 cell lines. Consistent with in vitro results, 14t significantly repressed tumor growth in the SW620 xenograft mouse model.

Nonredundant functions of Mycobacterium tuberculosis chaperones promote survival under stress

Bacterial chaperones ClpB and DnaK, homologs of the respective eukaryotic heat shock proteins Hsp104 and Hsp70, are essential in the reactivation of toxic protein aggregates that occur during translation or periods of stress. In the pathogen Mycobacterium tuberculosis (Mtb), the protective effect of chaperones extends to survival in the presence of host stresses, such as protein-damaging oxidants. However, we lack a full understanding of the interplay of Hsps and other stress response genes in mycobacteria. Here, we employ genome-wide transposon mutagenesis to identify the genes that support clpB function in Mtb. In addition to validating the role of ClpB in Mtb's response to oxidants, we show that HtpG, a homolog of Hsp90, plays a distinct role from ClpB in the proteotoxic stress response. While loss of neither clpB nor htpG is lethal to the cell, loss of both through genetic depletion or small molecule inhibition impairs recovery after exposure to host-like stresses, especially reactive nitrogen species. Moreover, defects in cells lacking clpB can be complemented by overexpression of other chaperones, demonstrating that Mtb's stress response network depends upon finely tuned chaperone expression levels. These results suggest that inhibition of multiple chaperones could work in concert with host immunity to disable Mtb.

In silico identification of small molecule modulators for disruption of Hsp90-Cdc37 protein-protein interaction interface for cancer therapeutic application

The protein-protein interactions (PPIs) in the biological systems are important to maintain a number of cellular processes. Several disorders including cancer may be developed due to dysfunction in the assembly of PPI networks. Hence, targeting intracellular PPIs can be considered as a crucial drug target for cancer therapy. Among the enormous and diverse group of cancer-enabling PPIs, the Hsp90-Cdc37 is prominent for cancer therapeutic development. The successful inhibition of Hsp90-Cdc37 PPI interface can be an important therapeutic option for cancer management. In the current study, a set of more than sixty thousand compounds belong to four databases were screened through a multi-steps molecular docking study in Glide against the Hsp90-Cdc37 interaction interface. The Glide-score and Prime-MM-GBSA based binding free energy of DCZ3112, standard Hsp90-Cdc37 inhibitor were found to be -6.96 and -40.46 kcal/mol, respectively. The above two parameters were used as cut-off score to reduce the chemical space from all successfully docked molecules. Furthermore, the in-silico pharmacokinetics parameters, common-feature pharmacophore analyses and the molecular binding interactions were used to wipe out the inactive molecules. Finally, four molecules were found to be important to modulate the Hsp90-Cdc37 interface. The potentiality of the final four molecules was checked through several drug-likeness characteristics. The molecular dynamics (MD) simulation study explained that all four molecules retained inside the interface of Hsp90-Cdc37. The binding free energy of each molecule obtained from the MD simulation trajectory was clearly explained the strong affection towards the Hsp90-Cdc37. Hence, the proposed molecule might be crucial for successful inhibition of the Hsp90-Cdc37 interface.Communicated by Ramaswamy H. Sarma.

Solution structure of the Hop TPR2A domain and investigation of target druggability by NMR, biochemical and in silico approaches

Heat shock protein 90 (Hsp90) is a molecular chaperone that plays an important role in tumour biology by promoting the stabilisation and activity of oncogenic 'client' proteins. Inhibition of Hsp90 by small-molecule drugs, acting via its ATP hydrolysis site, has shown promise as a molecularly targeted cancer therapy. Owing to the importance of Hop and other tetratricopeptide repeat (TPR)-containing cochaperones in regulating Hsp90 activity, the Hsp90-TPR domain interface is an alternative site for inhibitors, which could result in effects distinct from ATP site binders. The TPR binding site of Hsp90 cochaperones includes a shallow, positively charged groove that poses a significant challenge for druggability. Herein, we report the apo, solution-state structure of Hop TPR2A which enables this target for NMR-based screening approaches. We have designed prototype TPR ligands that mimic key native 'carboxylate clamp' interactions between Hsp90 and its TPR cochaperones and show that they block binding between Hop TPR2A and the Hsp90 C-terminal MEEVD peptide. We confirm direct TPR-binding of these ligands by mapping 1H-15N HSQC chemical shift perturbations to our new NMR structure. Our work provides a novel structure, a thorough assessment of druggability and robust screening approaches that may offer a potential route, albeit difficult, to address the chemically challenging nature of the Hop TPR2A target, with relevance to other TPR domain interactors.

Identification of the naphthoquinone derivative inhibitors binding site in heat shock protein 90: an induced-fit docking, molecular dynamics and 3D-QSAR study

The combination of molecular modeling methods to identify the putative binding site of inhibitors constitutes an important tool in drug discovery. In this work, we used these analyses to understand the potent inhibitory effect of naphthoquinone derivatives on heat shock protein 90 (Hsp90), one of the proteins involved in many types of cancer. Molecular docking results indicated that some favorable interactions of key amino acid residues at the binding site of Hsp90 with these quinones would be responsible for the inhibition of Hsp90 activity. Molecular docking and molecular dynamics simulation were carried out to further understand the binding modes and the interactions between the protein and these inhibitors. The main residues of the internal cavity were Val136, Phe138, Tyr139, Val150, Trp162 and Val186. The high concordance between the docking results and 3D-QSAR contour maps gives us helpful information about the environment of the binding site. Our results provide the bases for a rational modification of new molecules based in quinone scaffold, in order to design more potent Hsp90 inhibitors, which would exhibit highly potent antitumor activity.Communicated by Ramaswamy H. Sarma.

A Brain-Penetrating Hsp90 Inhibitor NXD30001 Inhibits Glioblastoma as a Monotherapy or in Combination With Radiation

Glioblastoma multiforme (GBM) is a highly heterogeneous disease, which is initiated and sustained by various molecular alterations in an array of signal transduction pathways. Heat-shock protein 90 (Hsp90) is a molecular chaperone and is critically implicated in folding and activation of a diverse group of client proteins, many of which are key regulators for glioblastoma biology. We here assessed the anti-neoplastic efficacy of a novel brain-penetrating Hsp90 inhibitor NXD30001 as a monotherapy and combined with radiation in vitro and in vivo. Our results demonstrated that NXD30001 potently inhibited neurosphere formation, growth, and survival of CD133+ GBM cells with the half maximal inhibitory concentration at low nanomolar range, but CD133- GBM cells were less sensitive to NXD30001. NXD30001 also increased radio-sensitivity in glioblastoma stem cells (GSCs) at suboptimal concentrations. Moreover, NXD30001 dose-dependently decreased phosphorylation levels of multiple Hsp90 client proteins which play key roles in GBM, such as EGFR, Akt, c-Myc, and Notch1. In addition, NXD30001 could impair DNA damage response and endoplasmic reticulum stress response after radiotherapy by alteration of the related proteins expression. In a murine orthotopic model of human glioblastoma, NXD30001 marvelously induced tumor regression and extended median survival of tumor-bearing mice by approximately 20% when compared with the vehicle group (37 d vs 31 d, P<0.05). Radiotherapy solely increased median survival of tumor-bearing mice from 31 d to 38 d (P<0.05), while NXD30001 combined with radiation further extended survival to 43 d (P<0.05). We concluded that GSCs are more sensitive to NXD30001 than non-stem GBM cells, and NXD30001 in combination with radiation exerts better inhibitive effect in GBM progression than monotherapy.

Direct targeting of HSP90 with daurisoline destabilizes β-catenin to suppress lung cancer tumorigenesis

Lung cancer is the most frequent cancer worldwide with a poor prognosis. Identification of novel cancer targets and useful therapeutic strategies without toxicity are urgently needed. In this study, we screened natural products for anticancer bioactivity in a library consisting of 429 small molecules. We demonstrated for the first time that daurisoline, a constituent of Rhizoma Menispermi, repressed lung cancer cell proliferation by inducing cell cycle arrest at the G1 phase. Furthermore, daurisoline was found not only to suppress the growth of lung tumor xenografts in animals without obvious side effects, but also to inhibit cell migration and invasion. Mechanistically, quantitative proteomics and bioinformatics analyses, Western blotting and qRT-PCR confirmed that daurisoline exerted its anticancer effects by inhibiting the expression levels of β-catenin and its downstream targets c-myc and cyclin D1. Furthermore, our data from Drug Affinity Responsive Target Stability (DARTS), isothermal titration calorimetry (ITC) and a series of functional assays demonstrated that daurisoline could target HSP90 directly and disrupt its interaction with β-catenin, therefore increasing the ubiquitin-mediated proteasomal degradation of β-catenin. This study reveals that daurisoline could be a promising therapeutic strategy for the treatment of lung cancer.

HSP90 and Co-chaperones: Impact on Tumor Progression and Prospects for Molecular-Targeted Cancer Therapy

Heat shock protein 90 (HSP90), a highly and unique chaperone, presents as a double-edged sword. It plays an essential role in many physiological and pathological processes, including tumor development. The current review highlights a recent understanding of the roles of HSP90 in molecular mechanisms underlying cancer survival and progression. HSP90 and its client proteins through the regulation of oncoproteins including signaling proteins, receptors, and transcriptional factors involved in tumorigenesis. It also has potential clinical application as diagnostic and prognostic biomarkers for assessing cancer progression. In this way, using HSP90 to develop new anticancer therapeutic agents including HSP90 inhibitors, anti-HSP90 antibody, and HSP90-based vaccines has been promising.

Anticancer properties and mechanism of action of the quassinoid ailanthone

Ailanthone (AIT) is a quassinoid natural product isolated from the worldwide-distributed plant Ailanthus altissima. The drug displays multiple pharmacological properties, in particular significant antitumor effects against a variety of cancer cell lines in vitro. Potent in vivo activities have been evidenced in mice bearing hepatocellular carcinoma, nonsmall cell lung cancer and castration-resistant prostate cancer. This review focusses on the mechanism of action of AIT, notably to highlight the capacity of the drug to activate DNA damage responses, to inhibit the Hsp90 co-chaperone p23 and to modulate the expression of several microRNA. The interconnexion between these effects is discussed. The unique capacity of AIT to downregulate oncogenic miR-21 and to upregulate the tumor suppressor miRNAs miR-126, miR-148a, miR-195, and miR-449a is presented. AIT exploits several microRNAs to exert its anticancer effects in distinct tumor types. AIT is one of the rare antitumor natural products that binds to and strongly inhibits cochaperone p23, opening interesting perspectives to treat cancers. However, the toxicity profile of the molecule may limit its development as an anticancer drug, unless it can be properly formulated to prevent AIT-induced gastro-intestinal damages in particular. The antitumor properties of AIT and analogs are underlined, with the aim to encourage further pharmacological studies with this underexplored natural product and related quassinoids. HIGHLIGHTS: Ailanthone (AIT) is an anticancer quassinoid isolated from Ailanthus altissima It inhibits proliferation and induces cell death of many cancer cell types The drug activates DNA damage response and targets p23 cochaperone Up or downregulation of several microRNA by AIT contributes to the anticancer activity Analogs or specific formulations must be developed to prevent the toxicity of AIT.

Biological Activities of Gedunin-A Limonoid from the Meliaceae Family

Gedunin is an important limonoid present in several genera of the Meliaceae family, mainly in seeds. Several biological activities have been attributed to gedunin, including antibacterial, insecticidal, antimalarial, antiallergic, anti-inflammatory, anticancer, and neuroprotective effects. The discovery of gedunin as a heat shock protein (Hsp) inhibitor represented a very important landmark for its application as a biological therapeutic agent. The current study is a critical literature review based on the several biological activities so far described for gedunin, its therapeutic effect on some human diseases, and future directions of research for this natural compound.

USP22-dependent HSP90AB1 expression promotes resistance to HSP90 inhibition in mammary and colorectal cancer

As a member of the 11-gene “death-from-cancer” gene expression signature, overexpression of the Ubiquitin-Specific Protease 22 (USP22) was associated with poor prognosis in various human malignancies. To investigate the function of USP22 in cancer development and progression, we sought to detect common USP22-dependent molecular mechanisms in human colorectal and breast cancer cell lines. We performed mRNA-seq to compare gene expression profiles of various colorectal (SW837, SW480, HCT116) and mammary (HCC1954 and MCF10A) cell lines upon siRNA-mediated knockdown of USP22. Intriguingly, while USP22 depletion had highly heterogeneous effects across the cell lines, all cell lines displayed a common reduction in the expression of Heat Shock Protein 90 Alpha Family Class B Member 1 (HSP90AB1). The downregulation of HSP90AB1 was confirmed at the protein level in these cell lines as well as in colorectal and mammary tumors in mice with tissue-specific Usp22 deletions. Mechanistically, we detected a significant reduction of H3K9ac on the HSP90AB1 gene in USP22-deficient cells. Interestingly, USP22-deficient cells displayed a high dependence on HSP90AB1 expression and diminishing HSP90 activity further using the HSP90 inhibitor Ganetespib resulted in increased therapeutic vulnerability in both colorectal and breast cancer cells in vitro. Accordingly, subcutaneously transplanted CRC cells deficient in USP22 expression displayed increased sensitivity towards Ganetespib treatment in vivo. Together, we discovered that HSP90AB1 is USP22-dependent and that cooperative targeting of USP22 and HSP90 may provide an effective approach to the treatment of colorectal and breast cancer.

Medium-Throughput Detection of Hsp90/Cdc37 Protein-Protein Interaction Inhibitors Using a Split Renilla Luciferase-Based Assay

The protein-folding chaperone Hsp90 enables the maturation and stability of various oncogenic signaling proteins and is thus pursued as a cancer drug target. Folding in particular of protein kinases is assisted by the co-chaperone Cdc37. Several inhibitors against the Hsp90 ATP-binding site have been developed. However, they displayed significant toxicity in clinical trials. By contrast, the natural product conglobatin A has an exceptionally low toxicity in mice. It targets the protein-protein interface (PPI) of Hsp90 and Cdc37, suggesting that interface inhibitors have an interesting drug development potential. In order to identify inhibitors of the Hsp90/Cdc37 PPI, we have established a mammalian cell lysate-based, medium-throughput amenable split Renilla luciferase assay. This assay employs N-terminal and C-terminal fragments of Renilla luciferase fused to full-length human Hsp90 and Cdc37, respectively. We expect that our assay will allow for the identification of novel Hsp90/Cdc37 interaction inhibitors. Such tool compounds will help to evaluate whether the toxicity profile of Hsp90/Cdc37 PPI inhibitors is in general more favorable than that of ATP-competitive Hsp90 inhibitors. Further development of such tool compounds may lead to new classes of Hsp90 inhibitors with applications in cancer and other diseases.