Development Of Hsp90 Inhibitors Research Articles

Targeting HSP90 as a Novel Therapy for Cancer: Mechanistic Insights and Translational Relevance.

Heat shock protein (HSP90), a highly conserved molecular chaperon, is indispensable for the maturation of newly synthesized poly-peptides and provides a shelter for the turnover of misfolded or denatured proteins. In cancers, the client proteins of HSP90 extend to the entire process of oncogenesis that are associated with all hallmarks of cancer. Accumulating evidence has demonstrated that the client proteins are guided for proteasomal degradation when their complexes with HSP90 are disrupted. Accordingly, HSP90 and its co-chaperones have emerged as viable targets for the development of cancer therapeutics. Consequently, a number of natural products and their analogs targeting HSP90 have been identified. They have shown a strong inhibitory effect on various cancer types through different mechanisms. The inhibitors act by directly binding to either HSP90 or its co-chaperones/client proteins. Several HSP90 inhibitors—such as geldanamycin and its derivatives, gamitrinib and shepherdin—are under clinical evaluation with promising results. Here, we review the subcellular localization of HSP90, its corresponding mechanism of action in the malignant phenotypes, and the recent progress on the development of HSP90 inhibitors. Hopefully, this comprehensive review will shed light on the translational potential of HSP90 inhibitors as novel cancer therapeutics.

Hsp90 as Drug Target Against Bacterial and Fungal Infections

Heat shock proteins (Hsps) are a group of proteins that serve to improve cell survival in response to a variety of environmental stresses of the host. In recent years, Hsps gained interest in cancer therapy and as drug target against microbial infections. The antimicrobial resistance especially by Gram-negative pathogens poses a threat to mankind. The pathogen proteins of Hsp family yield Hsp90 inhibitor antibiotic reveal mechanisms that interact with the ADP/ATP-sites of Hsp90. For the present review, we used the databases and websites PubMed, SciFinder, Scopus, ProQuest, Google and Google Scholar. The review discusses the development of Hsp90 inhibitors for bacterial as well as fungal infections and how these inhibitors are being used for clinical trials. A systematic web search analysis was conducted from April to November 2019.

Design, synthesis, and biological evaluation of truncated deguelin derivatives as Hsp90 inhibitors

A series of novel B and C-rings truncated deguelin derivatives have been designed and synthesized in the present study as heat shock protein 90 (Hsp90) inhibitors. The synthesized compounds exhibited micromolar antiproliferative potency toward a panel of human cancer cell lines. Their structure-activity relationships (SARs) were investigated in a systematic manner. Compound 21c was identified to have high Hsp90 binding potency (60 nM) and caused degradation of client proteins through ubiquitin proteasome system. Further biological studies showed that compound 21c induced a dose-dependent S and G2-phase cell cycle arrest on human breast cancer MCF-7 cells. Flow cytometry and Western blot analyses confirmed that compound 21c caused apoptosis of MCF-7 cells. In addition, compound 21c showed much potent inhibition on the migration and invasion of MCF-7 cells. Taken together, these results suggest that 21c might be a promising lead compound for further development of Hsp90 inhibitors.

X-linked inhibitor of apoptosis protein (XIAP) is a client of heat shock protein 70 (Hsp70) and a biomarker of its inhibition

Heat shock protein 70 (Hsp70) and Hsp90 are molecular chaperones that play essential roles in tumor growth by stabilizing pro-survival client proteins. However, although the development of Hsp90 inhibitors has benefited from the identification of clients, such as Raf-1 proto-oncogene, Ser/Thr kinase (RAF1), that are particularly dependent on this chaperone, no equivalent clients for Hsp70 have been reported. Using chemical probes and MDA-MB-231 breast cancer cells, we found here that the inhibitors of apoptosis proteins, including c-IAP1 and X-linked inhibitor of apoptosis protein (XIAP), are obligate Hsp70 clients that are rapidly (within ∼3-12 h) lost after inhibition of Hsp70 but not of Hsp90. Mutagenesis and pulldown experiments revealed multiple Hsp70-binding sites on XIAP, suggesting that it is a direct, physical Hsp70 client. Interestingly, this interaction was unusually tight (∼260 nm) for an Hsp70-client interaction and involved non-canonical regions of the chaperone. Finally, we also found that Hsp70 inhibitor treatments caused loss of c-IAP1 and XIAP in multiple cancer cell lines and in tumor xenografts, but not in healthy cells. These results are expected to significantly accelerate Hsp70 drug discovery by providing XIAP as a pharmacodynamic biomarker. More broadly, our findings further suggest that Hsp70 and Hsp90 have partially non-overlapping sets of obligate protein clients in cancer cells.

P53 protects against LPS-induced lung endothelial barrier dysfunction.

New therapies toward heart and blood vessel disorders may emerge from the development of Hsp90 inhibitors. Several independent studies suggest potent anti-inflammatory activities of those agents in human tissues. The molecular mechanisms responsible for their protective effects in the vasculature remain unclear. The present study demonstrates that the transcription factor p53, an Hsp90 client protein, is crucial for the maintenance of vascular integrity, protects again LPS-induced endothelial barrier dysfunction, and is involved in the mediation of the anti-inflammatory activity of Hsp90 inhibitors in lung tissues. p53 silencing by siRNA decreased transendothelial resistance (a measure of endothelial barrier function). A similar effect was induced by the p53 inhibitor pifithrin, which also potentiated the LPS-induced hyperpermeability in human lung microvascular endothelial cells (HLMVEC). On the other hand, p53 induction by nutlin suppressed the LPS-induced vascular barrier dysfunction. LPS decreased p53 expression in lung tissues and that effect was blocked by pretreatment with Hsp90 inhibitors both in vivo and in vitro. Furthermore, the Hsp90 inhibitor 17-allyl-amino-demethoxy-geldanamycin suppressed the LPS-induced overexpression of the p53 negative regulator MDMX as well as p53 and MDM2 (another p53 negative regulator) phosphorylation in HLMVEC. Both negative p53 regulators were downregulated by LPS in vivo. Chemically induced p53 overexpression resulted in the suppression of LPS-induced RhoA activation and MLC2 phosphorylation, whereas p53 suppression caused the opposite effects. These observations reveal new mechanisms for the anti-inflammatory actions of Hsp90 inhibitors, i.e., the induction of the transcription factor p53, which in turn can orchestrate robust vascular anti-inflammatory responses both in vivo and in vitro.

2,4-dihydroxy benzaldehyde derived Schiff bases as small molecule Hsp90 inhibitors: Rational identification of a new anticancer lead

Hsp90 is a molecular chaperone that heals diverse array of biomolecules ranging from multiple oncogenic proteins to the ones responsible for development of resistance to chemotherapeutic agents. Moreover they are over-expressed in cancer cells as a complex with co-chaperones and under-expressed in normal cells as a single free entity. Hence inhibitors of Hsp90 will be more effective and selective in destroying cancer cells with minimum chances of acquiring resistance to them. In continuation of our goal to rationally develop effective small molecule azomethines against Hsp90, we designed few more compounds belonging to the class of 2,4-dihydroxy benzaldehyde derived imines (1–13) with our validated docking protocol. The molecules exhibiting good docking score were synthesized and their structures were confirmed by IR, 1H NMR and mass spectral analysis. Subsequently, they were evaluated for their potential to suppress Hsp90 ATPase activity by Malachite green assay. The antiproliferative effect of the molecules were examined on PC3 prostate cancer cell lines by adopting 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay methodology. Finally, schiff base 13 emerged as the lead molecule for future design and development of Hsp90 inhibitors as anticancer agents.

Hsp90 Molecular Chaperone Inhibitors: Are We There Yet?

Heat shock protein (Hsp) 90 is an ATP-dependent molecular chaperone that is exploited by malignant cells to support activated oncoproteins, including many cancer-associated kinases and transcription factors, and it is essential for oncogenic transformation. Originally viewed with skepticism, Hsp90 inhibitors are now being actively pursued by the pharmaceutical industry, with 17 agents having entered clinical trials. Investigators established Hsp90's druggability using the natural products geldanamycin and radicicol, which mimic the unusual ATP structure adopted in the chaperone's N-terminal nucleotide-binding pocket and cause potent and selective blockade of ATP binding/hydrolysis, inhibit chaperone function, deplete oncogenic clients, and show antitumor activity. Preclinical data obtained with these natural products have heightened interest in Hsp90 as a drug target, and 17-allylamino-17-demethoxygeldanamycin (17-AAG, tanespimycin) has shown clinical activity (as defined by Response Evaluation Criteria in Solid Tumors) in HER2+ breast cancer. Many optimized synthetic, small-molecule Hsp90 inhibitors from diverse chemotypes are now in clinical trials. Here, we review the discovery and development of Hsp90 inhibitors and assess their potential. There has been significant learning from studies of the basic biology of Hsp90, as well as translational drug development involving this chaperone, enhanced by the use of Hsp90 inhibitors as chemical probes. Success will likely lie in treating cancers that are addicted to particular driver oncogene products (e.g., HER2, ALK, EGFR, and BRAF) that are sensitive Hsp90 clients, as well as malignancies (especially multiple myeloma) in which buffering of proteotoxic stress is critical for survival. We discuss approaches for enhancing the effectiveness of Hsp90 inhibitors and highlight new chaperone and stress-response pathway targets, including HSF1 and Hsp70.

Development of Hsp90 inhibitors as anticancer compounds

Development of Hsp90 inhibitors as anticancer compounds

Binding of Natural and Synthetic Inhibitors to Human Heat Shock Protein 90 and Their Clinical Application

This review describes the recent progress in the field of heat shock protein 90 (Hsp90) inhibitor design. Hsp90 is a heat shock protein with a molecular weight of approximately 90 kDa. Hsp90 is considered a good anticancer target because its inhibition leads to inactivation of its numerous client proteins participating in various signaling and other processes involved in cancer progression. Numerous Hsp90 inhibitors-leads currently tested in clinical trials are presented in this review. Furthermore, this review emphasizes the application of biophysical binding assays in the development of Hsp90 inhibitors. The binding of designed lead compounds to various Hsp90 constructs is measured by isothermal titration calorimetry and thermal shift assay. These assays provide a detailed energetic insight of the binding reaction, including the enthalpy, entropy, heat capacity, and the Gibbs free energy. A detailed description of the binding energetics helps to extend our knowledge of structure-activity relationships in the design of more potent inhibitors. The most active compounds are then tested for their absorption, distribution, metabolism, elimination, toxicity, and activity against cancer cell lines.

Heat-shock protein 90 inhibitors as antitumor agents: a survey of the literature from 2005 to 2010

Introduction: Heat-shock protein 90 (Hsp90) is a validated novel anticancer target with unique features. As a molecular chaperone, Hsp90 is implicated in maintaining the conformation, stability, activity and cellular localization of several key oncogenic client proteins that are involved in signal transduction pathways leading to proliferation, cell-cycle progression, apoptosis, angiogenesis and metastasis. As a result, inhibitors of Hsp90 achieve their promising anticancer activity through disruption of the Hsp90 protein function, thereby freezing the chaperone cycle; this in turn decreases the affinity of Hsp90 for client proteins, thus leading to proteasome-mediated degradation of oncogenic client proteins within cancer cells.Areas covered: This review provides recent background information on Hsp90 inhibitors. It also highlights a panel of compounds of interest reported in patents and discusses the clinical results of the promising drug candidates.Expert opinion: In the past 5 years, Hsp90 inhibitors have remained the focus of much interest as new potential anticancer agents. A large variety of scaffolds were studied in both academia and industry. Consequently, these significant research efforts have provided several promising drug candidates for further clinical development. Further progress in the development of Hsp90 inhibitors, combined with a deeper understanding of the chaperon characteristics, strengthens their promise in cancer therapy.

Abstract 2605: Identification and development of NVP-HSP990, a potent and orally active Hsp90 inhibitor for cancer treatment

Abstract Hsp90 is recognized as a potential target for the treatment of cancer, due to its chaperone functions that are required for maintaining the stability and/or active conformation of signalling molecules essential for tumorigenesis. The development of small molecule Hsp90 inhibitors has become an extremely competitive field of research. Here for the first time we present biological and pharmacological properties of NVP-HSP990, a potent oral Hsp90 inhibitor discovered by Novartis. In vitro, NVP-HSP990 potently inhibits all 4 isoforms of Hsp90 (Hsp90α, Hsp90β, TRAP-1 and GRP94) and has no major activities in a safety pharmacology panel of kinases, receptors and enzymes evaluated. NVP-HSP990 demonstrates broad-spectrum anti-tumor activities in tumor cell lines (IC 50s ranging from 4-35 nM) and primary patient samples (mean IC50 =49 nM). In vivo, NVP-HSP990 is highly bioavailable across species and a single oral administration of 15 mg/kg induces sustained target inhibition up to 7 days as indicated by downregulation of client protein (c-Met) and upregulation of Hsp70 in a cMet overexpressing gastric GTL16 xenograft tumor model. Weekly administration of NVP-HSP990 was efficacious in a broad range of mouse and rat human tumor xenograft models driven by well defined oncogenic Hsp90 client proteins. In summary, NVP-HSP990 represents a novel class of oral Hsp90 inhibitors with unique and superior pharmacological and drug-like properties. NVP-HSP990 is currently being evaluated in Phase I clinical trial in advanced solid tumors. In addition, we will present multiple secreted biomarkers for Hsp90 that were identified through a novel in-silico data mining approach. Several of these biomarkers have been validated both in vitro and in vivo, and have the potential to be utilized as clinical pharmaco-dynamic markers in the development of Hsp90 inhibitors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2605. doi:10.1158/1538-7445.AM2011-2605

Discovery and development of Hsp90 inhibitors: a promising pathway for cancer therapy

The Hsp90 chaperone is a master regulator of the stability and activity of multiple oncoproteins such as Her2, Akt, Bcr-Abl, c-Kit, EGFR and mutant BRAF. The promise of inhibition of such a master regulator for cancer therapy is the potential to cause combinatorial inhibition of multiple oncogenic signaling pathways simultaneously. With the recent discovery of feedback loops that effectively negate the efficacy of selectively targeted anti-cancer agents, there is renewed interest in such a multi-pronged approach. There are now 14 drug candidates that target Hsp90 undergoing clinical trials in multiple indications as single agents or combination therapy. These compounds represent a diverse array of chemical matter stemming from natural product scaffolds to synthetic structure-based design. Although the compounds fall into distinct classes with unique properties, each inhibitor binds in the N-terminal ATP pocket and accumulates in tumor tissue while being rapidly cleared from circulation and normal tissue. The most advanced candidates are now in Phase 2 clinical trials and defining the therapeutic window, dosing schedule, and indication are the primary challenges for these potential first-in-class inhibitors.

Update on Hsp90 inhibitors in clinical trial.

Twenty-five years ago the first small molecule inhibitors of Hsp90 were identified. In the intervening years there has been dramatic progress in basic scientific understanding of the Hsp90 chaperone machinery and in the role of Hsp90 in malignancy. The first-in-class Hsp90 inhibitor 17-AAG entered into Phase I clinical trials in 1999. There are now 13 Hsp90 inhibitors in clinical trial, representing multiple drug classes, and hundreds of patients have been treated in adult oncology and pediatric oncology trials. This review will provide an overview of the clinical trial results thus far. In addition, pivotal issues in further development of Hsp90 inhibitors as anticancer drugs will be discussed.

HSP90 Inhibitors: Multi-Targeted Antitumor Effects and Novel Combinatorial Therapeutic Approaches in Cancer Therapy

With the rapid rise of tumor resistance, combinatorial anticancer therapies have gained favor over single-molecule inhibition to maximize the suppression of oncogenic pathways. In this regard, HSP90 inhibitors have rapidly emerged as a class of promising drugs that can target multiple oncogenic pathways simultaneously. HSP90 is a highly conserved protein chaperone involved in essential cellular functions such as protein folding and cell signaling in both stressed and unstressed cells. In the last decade, a large number of oncogenic client proteins have been identified to associate with HSP90 and contribute to malignant transformation. Development of HSP90 inhibitors, derived from the natural compound geldanamycin that mimics the ATP binding site of HSP90, was designed to target HSP90 and allow degradation of these client proteins. Preclinical and clinical data with HSP90 inhibitors in various cancer models are promising, and evidences also hint at the potential for tumor-selective cytotoxicity as well as enhanced sensitization to chemo- and radiotherapy. This review will discuss the effects of HSP90 inhibition in cancer, the known mechanistic basis for the oncogenic toxicity and selectivity, as well as the current progress on single or combinatorial therapies with HSP90 inhibitors.

Human 90 kDa Heat Shock Protein Hsp90 as a Target for Cancer Therapeutics

Protein misfolding causes a phenotype of disorders that is modulated by the action of multi-complexes formed by molecular chaperones and the proteasome machine. Hsp90 is a molecular chaperone involved in maintaining folding, stability and function of many proteins involved in apoptosis, signal-transduction pathways and cell-cycle regulation. Many of these proteins are usually deregulated in cancers and by keeping them active Hsp90 helps the stabilization of tumorogenic cells. Therefore, inhibition of Hsp90 will result in degradation of its client proteins via the proteasome followed by a down regulation of several properties of the malignant phenotype. As a consequence, Hsp90 has been considered to be an appealing target for cancer therapeutics because its inhibition can affect multiple oncogenic pathways simultaneously. Major efforts have generated Hsp90 inhibitors that passed Phase I clinical trials and have entered Phase II trials. Furthermore, other compounds are in development to improve efficacy as antitumor agents. In conclusion, the development of Hsp90 inhibitors is considered to be a good example of medicinal chemistry. Specific important aspects of Hsp90 structure and function, the role of the chaperone in cancer and the development of Hsp90 inhibitors that causes growth arrest and apoptosis in cancer cells are discussed. Keywords: medicinal chemistry, antitumor drugs, geldanamycin, cancer therapeutics, molecular chaperone, Hsp90 inhibitors

The Hsp90 molecular chaperone: an open and shut case for treatment

The molecular chaperone Hsp90 (90 kDa heat-shock protein) is a remarkably versatile protein involved in the stress response and in normal homoeostatic control mechanisms. It interacts with 'client proteins', including protein kinases, transcription factors and others, and either facilitates their stabilization and activation or directs them for proteasomal degradation. By this means, Hsp90 displays a multifaceted ability to influence signal transduction, chromatin remodelling and epigenetic regulation, development and morphological evolution. Hsp90 operates as a dimer in a conformational cycle driven by ATP binding and hydrolysis at the N-terminus. The cycle is also regulated by a group of co-chaperones and accessory proteins. Here we review the biology of the Hsp90 molecular chaperone, emphasizing recent progress in our understanding of structure-function relationships and the identification of new client proteins. In addition we describe the exciting progress that has been made in the development of Hsp90 inhibitors, which are now showing promise in the clinic for cancer treatment. We also identify the gaps in our current understanding and highlight important topics for future research.

HSP90: A Rising Star on the Horizon of Anticancer Targets

Over the past decade, heat-shock protein (HSP)90 has begun to draw increasing attention as a novel anticancer target with unique features. As a molecular chaperone, HSP90 promotes the maturation and maintains the stability of a large number of conformationally labile client proteins, most of which are involved in biologic processes that are often deranged within tumor cells, such as signal transduction, cell-cycle progression and apoptosis. As a result, and in contrast to other molecular targeted therapeutics, inhibitors of HSP90 achieve their promising anticancer activity through simultaneous disruption of many oncogenic substrates within cancer cells. This review provides a brief summary of HSP90 biology and its association with cancer. It describes the discovery and development of HSP90 inhibitors as anticancer agents and their current status in the clinic. Finally, it closes with a discussion of the unique challenges confronting the further development of these agents and their prospects for the future.

The opportunities and challenges of personalized genome-based molecular therapies for cancer: targets, technologies, and molecular chaperones.

There are now unprecedented opportunities for the development of improved drugs for cancer treatment. Following on from the Human Genome Project, the Cancer Genome Project and related activities will define most of the genes in the majority of common human cancers over the next 5 years. This will provide the opportunity to develop a range of drugs targeted to the precise molecular abnormalities that drive various human cancers and opens up the possibility of personalized therapies targeted to the molecular pathology and genomics of individual patients and their malignancies. The new molecular therapies should be more effective and have less-severe side effects than cytotoxic agents. To develop the new generation of molecular cancer therapeutics as rapidly as possible, it is essential to harness the power of a range of new technologies. These include: genomic and proteomic methodologies (particularly gene expression microarrays); robotic high-throughput screening of diverse compound collections, together with in silico and fragment-based screening techniques; new structural biology methods for rational drug design (especially high-throughput X-ray crystallography and nuclear magnetic resonance); and advanced chemical technologies, including combinatorial and parallel synthesis. Two major challenges to cancer drug discovery are: (1) the ability to convert potent and selective lead compounds with activity by the desired mechanism on tumor cells in culture into agents with robust, drug-like properties, particularly in terms of pharmacokinetic and metabolic properties; and (2) the development of validated pharmacodynamic endpoints and molecular markers of drug response, ideally using noninvasive imaging technologies. The use of various new technologies will be exemplified. A major conceptual and practical issue facing the development and use of the new molecular cancer therapeutics is whether a single drug that targets one of a series of key molecular abnormalities in a particular cancer (e.g. BRAF) will be sufficient on its own to deliver clinical benefit ("house of cards" and tumor addiction models). The alternative scenario is that it will require either a combination of agents or a class of drug that has downstream effects on a range of oncogenic targets. Inhibitors of the heat-shock protein (HSP) 90 molecular chaperone are of particular interest in the latter regard, because they offer the potential of inhibiting multiple oncogenic pathways and simultaneous blockade of all six "hallmark traits" of cancer through direct interaction with a single molecular drug target. The first-in-class HSP90 inhibitor 17AAG exhibited good activity in animal models and is now showing evidence of molecular and clinical activity in ongoing clinical trials. Novel HSP90 inhibitors are also being sought. The development of HSP90 inhibitors is used to exemplify the application of new technologies in drug discovery against a novel molecular target, and in particular the need for innovative pharmacodynamic endpoints is emphasized as an essential component of hypothesis-testing clinical trials.