New molecular and biological mechanism of antitumor activities of KW-2478, a novel nonansamycin heat shock protein 90 inhibitor, in multiple myeloma cells

Functional transcriptome analysis revealed upregulation of MAPK-SMAD signalling pathways in chronic heat stress in crossbred cattle

Animal geneticists and breeders have the impending challenge of enhancing the resilience of Indian livestock to heat stress through better selection strategies. Climate change's impact on livestock is more intense in tropical countries like India where dairy cattle crossbreeds are more sensitive to heat stress. The main reason for this study was to find the missing relative changes in transcript levels in thermo-neutral and heat stress conditions in crossbred cattle through whole-transcriptome analysis of RNA-Seq data. Differentially expressed genes (DEGs) identified based on the minimum log twofold change value and false discovery rate 0.05 revealed 468 up-regulated genes and 2273 down-regulated significant genes. Functional annotation and pathway analysis of these significant DEGs were compared based on Gene Ontology (Biological process), Kyoto Encyclopedia of Genes and Genome (KEGG), and Reactome pathways using g: Profiler, ShinyGO v0.76, and iDEP.951 web tools. On finding network visualization, the most over-represented and correlated pathways were neuronal and sensory organ development, calcium signalling pathway, Mitogen-activated protein kinase (MAPK) and Smad signalling pathway, Ras-proximate-1, or Ras-related protein 1 (Rap 1) signalling pathway, apoptosis, and oxidative stress. Similarly, down-regulated genes were most expressed in mRNA processing, immune system, B-cell receptor signalling pathway, Nucleotide oligomerization domain (NOD)-like receptors (NLRs) signalling pathway and nonsense-mediated decay (NMD) pathway. The heat stress-responsive genes identified in this study will facilitate our understanding of the molecular basis for climate resilience and heat tolerance in Indian dairy crossbreeds.

Prospects and challenges of noncoding-RNA-mediated inhibition of heat shock protein 90 for cancer therapy

Heat Shock Protein 90 (HSP90) is a potential drug target for cancer therapy as it is often dysregulated in several cancers, including lung, breast, pancreatic, and prostate cancers. In cancer, HSP90 fails to maintain the structural and functional integrity of its several client proteins which are involved in the hallmarks of cancer such as cell proliferation, invasion, migration, angiogenesis, and apoptosis. Several small molecule inhibitors of HSP90 have been shown to exhibit anticancer effects in vitro and in vivo animal models. However, a few of them are currently under clinical studies. The status and potential limitations of these inhibitors are discussed here. Studies demonstrate that several noncoding RNAs (ncRNAs) such as microRNAs (miRNAs) and long noncoding RNAs (lncRNAs) regulate HSP90 and its client proteins to modulate cellular processes to exhibit oncogenic or tumor suppressing properties. Over the last decade, miRNAs and lncRNAs have drawn significant interest from the scientific community as therapeutic agents or targets for clinical applications. Here, we discuss the detailed mechanistic regulation of HSP90 and its client proteins by ncRNAs. Moreover, we highlight the significance of these ncRNAs as potential therapeutic agents/targets, and the challenges associated with ncRNA-based therapies. This article aims to provide a holistic view on HSP90-regulating ncRNAs for the development of novel therapeutic strategies to combat cancer.

The Interplay between Heat Shock Proteins and Cancer Pathogenesis: A Novel Strategy for Cancer Therapeutics

Heat shock proteins (HSPs) are developmentally conserved families of protein found in both prokaryotic and eukaryotic organisms. HSPs are engaged in a diverse range of physiological processes, including molecular chaperone activity to assist the initial protein folding or promote the unfolding and refolding of misfolded intermediates to acquire the normal or native conformation and its translocation and prevent protein aggregation as well as in immunity, apoptosis, and autophagy. These molecular chaperonins are classified into various families according to their molecular size or weight, encompassing small HSPs (e.g., HSP10 and HSP27), HSP40, HSP60, HSP70, HSP90, and the category of large HSPs that include HSP100 and ClpB proteins. The overexpression of HSPs is induced to counteract cell stress at elevated levels in a variety of solid tumors, including anticancer chemotherapy, and is closely related to a worse prognosis and therapeutic resistance to cancer cells. HSPs are also involved in anti-apoptotic properties and are associated with processes of cancer progression and development, such as metastasis, invasion, and cell proliferation. This review outlines the previously mentioned HSPs and their significant involvement in diverse mechanisms of tumor advancement and metastasis, as well as their contribution to identifying potential targets for therapeutic interventions.

HSP90AB1 Is a Host Factor Required for Transmissible Gastroenteritis Virus Infection

Transmissible gastroenteritis virus (TGEV) is an important swine enteric coronavirus causing viral diarrhea in pigs of all ages. Currently, the development of antiviral agents targeting host proteins to combat viral infection has received great attention. The heat shock protein 90 (HSP90) is a critical host factor and has important regulatory effects on the infection of various viruses. However, its roles in porcine coronavirus infection remain unclear. In this study, the effect of HSP90 on TGEV infection was evaluated. In addition, the influence of its inhibitor VER-82576 on proinflammatory cytokine (IL-6, IL-12, TNF-α, CXCL10, and CXCL11) production induced by TGEV infection was further analyzed. The results showed that the knockdown of HSP90AB1 and HSP90 inhibitor VER-82576 treatment resulted in a reduction in TGEV M gene mRNA levels, the N protein level, and virus titers in a dose-dependent manner, while the knockdown of HSP90AA1 and KW-2478 treatment had no significant effect on TGEV infection. A time-of-addition assay indicated that the inhibitory effect of VER-82576 on TGEV infection mainly occurred at the early stage of viral replication. Moreover, the TGEV-induced upregulation of proinflammatory cytokine (IL-6, IL-12, TNF-α, CXCL10, and CXCL11) expression was significantly inhibited by VER-82576. In summary, these findings indicated that HSP90AB1 is a host factor enhancing TGEV infection, and the HSP90 inhibitor VER-82576 could reduce TGEV infection and proinflammatory cytokine production, providing a new perspective for TGEV antiviral drug target design.

A Drug Screening Reveals Minocycline Hydrochloride as a Therapeutic Option to Prevent Breast Cancer Cells Extravasation across the Blood-Brain Barrier

Among breast cancer (BC) patients, 15-25% develop BC brain metastases (BCBM), a severe condition due to the limited therapeutic options, which points to the need for preventive strategies. We aimed to find a drug able to boost blood-brain barrier (BBB) properties and prevent BC cells (BCCs) extravasation, among PI3K, HSP90, and EGFR inhibitors and approved drugs. We used BCCs (4T1) and BBB endothelial cells (b.End5) to identify molecules with toxicity to 4T1 cells and safe for b.End5 cells. Moreover, we used those cells in mixed cultures to perform a high-throughput microscopy screening of drugs' ability to ameliorate BBB properties and prevent BCCs adhesion and migration across the endothelium, as well as to analyse miRNAs expression and release profiles. KW-2478, buparlisib, and minocycline hydrochloride (MH) promoted maximal expression of the junctional protein β-catenin and induced 4T1 cells nucleus changes. Buparlisib and MH further decreased 4T1 adhesion. MH was the most promising in preventing 4T1 migration and BBB disruption, tumour and endothelial cytoskeleton-associated proteins modifications, and miRNA deregulation. Our data revealed MH's ability to improve BBB properties, while compromising BCCs viability and interaction with BBB endothelial cells, besides restoring miRNAs' homeostasis, paving the way for MH repurposing for BCBM prevention.

The HSP90 inhibitor KW-2478 depletes the malignancy of BCR/ABL and overcomes the imatinib-resistance caused by BCR/ABL amplification

BACKGROUND

With the widespread clinical application of tyrosine kinase inhibitors (TKIs), an increasing number of chronic myeloid leukaemia (CML) patients have developed resistance or intolerance to TKIs. BCR/ABL is the oncoprotein of CML. HSP90 is an essential chaperone of BCR/ABL and plays an important role in protein folding and the function of BCR/ABL. Therefore, inhibiting the chaperone function of HSP90 may be an effective strategy for CML treatment and to overcome TKI resistance.

METHODS

The effect of KW-2478 on CML cell viability, apoptosis and cell cycle progression was detected by CCK-8 assay or flow cytometry. The levels of BCR/ABL, HSP90 and other signalling proteins were detected by western blots. The mitochondrial membrane potential was detected by flow cytometry combined with JC-1 staining. The interaction between BCR/ABL and HSP90α was detected by coimmunoprecipitation. The effect of KW-2478 on BCR/ABL carcinogenesis in vivo was investigated in CML-like mouse models.

RESULTS

KW-2478 inhibited growth and induced apoptosis of CML cells. KW-2478 inhibited the chaperone function of HSP90α and then weakened the BCR/ABL and MAPK signalling pathways. This treatment also caused an increase in p27 and p21 expression and a decrease in cyclin B1 expression, which led to G2/M phase arrest. The mitochondrial pathway was primarily responsible for KW-2478-induced apoptosis. KW-2478 had a synergistic effect with imatinib in growth inhibition. Notably, KW-2478 had a stronger effect on growth inhibition, apoptosis induction and cell cycle arrest of K562/G01 cells than K562 cells. KW-2478 could effectively prolong the mouse lifespan and alleviate disease symptoms in CML-like mouse models.

CONCLUSIONS

This finding demonstrated that KW-2478 had anticancer properties in imatinib-sensitive and imatinib-resistant CML cells and illustrated the possible mechanisms. This study provides an alternative choice for CML treatment, especially for TKI-resistant patients with BCR/ABL amplification and TKI-intolerant patients.

Indolethylamine-N-Methyltransferase Inhibits Proliferation and Promotes Apoptosis of Human Prostate Cancer Cells: A Mechanistic Exploration

Indolethylamine-N-methyltransferase (INMT) is a methyltransferase downregulated in lung cancer, meningioma, and prostate cancer; however, its role and mechanism in prostate cancer remain unclear. By analyzing The Cancer Genome Atlas (TCGA)-PRAD, we found that the expression of INMT in prostate cancer was lower than that of adjacent non-cancerous prostate tissues and was significantly correlated with lymph node metastasis Gleason score, PSA expression, and survival. Combined with the GSE46602 cohorts for pathway enrichment analysis, we found that INMT was involved in regulating the MAPK, TGFβ, and Wnt signaling pathways. After overexpression of INMT in prostate cancer cell lines 22Rv1 and PC-3, we found an effect of INMT on these tumor signal pathways; overexpression of INMT inhibited the proliferation of prostate cancer cells and promoted apoptosis. Using the ESTIMATE algorithm, we found that with the increase of INMT expression, immune and stromal scores in the tumor microenvironment increased, immune response intensity increased, and tumor purity decreased. The difference in INMT expression affected the proportion of several immune cells. According to PRISM and CTRP2.0, the potential therapeutic agents associated with the INMT expression subgroup in TCGA were predicted. The area under the curve (AUC) values of 26 compounds positively correlated with the expression of INMT, while the AUC values of 14 compounds were negatively correlated with the expression of INMT. These findings suggest that INMT may affect prostate cancer’s occurrence, development, and drug sensitivity via various tumor signaling pathways and tumor microenvironments.

Discovery of BP3 as an efficacious proteolysis targeting chimera (PROTAC) degrader of HSP90 for treating breast cancer

Heat shock protein 90 (HSP90) is involved in the stabilization and activation of oncoproteins, rendering it essential for oncogenic transformation. However, the HSP90 inhibitors evaluated to date have not led to the expected effects in cancer therapy. Herein, we systematically described the design, synthesis, and evaluation of HSP90 degraders based upon the proteolysis-targeting chimera (PROTAC) strategy. The results showed that the candidate compound 16b (BP3) potently degraded HSP90 and effectively inhibited the growth of human breast cancer cells. When used as a single agent, BP3 led to effective tumor suppression in mice. These findings demonstrate that our HSP90-targeting PROTAC strategy has potential novel applications in breast cancer therapy.

HSP90 inhibitors 17-AAG and VER-82576 inhibit porcine deltacoronavirus replication in vitro

Porcine deltacoronavirus (PDCoV) is highly pathogenic to piglets, and no specific drugs or vaccines are available for the prevention and treatment of PDCoV infection, the need for antiviral therapies is pressing. HSP90 inhibitors have potent inhibitory effects against the replication of numerous viruses, hence we evaluated three HSP90 inhibitors, 17-AAG, VER-82576, and KW-2478, for their effects on PDCoV infection in vitro. We evaluated their effectivenesses at suppressing PDCoV by qRT-PCR, western blot, and TCID₅₀ assay, and found that 17-AAG and VER-82576 inhibited PDCoV at the early stage of replication, while KW-2478 showed no significant antiviral activity at any stage of infection. These results indicated that the PDCoV-inhibitory effects of 17-AAG and VER-82576 might be exerted by targeting host cell factor HSP90AB1 but not HSP90AA1. Further study showed that HSP90AB1 mRNA and protein levels were not significantly different in 17-AAG and VER-82576-treated cells versus control cells. 17-AAG and VER-82576 were also evaluated for their effects on the expressions of TNF-α, IL-6, and IL-12, which are PDCoV-induced proinflammatory cytokines. We found that both 17-AAG and VER-82576 inhibited the expressions of TNF-α, IL-6, and IL-12 to varying degrees, but in a dose dependent manner. From our data we can conclude that the HSP90 inhibitors 17-AAG and VER-82576 are promising candidates for the treatment of PDCoV infection.

Regulation of Mitogen-Activated Protein Kinase Signaling Pathways by the Ubiquitin-Proteasome System and Its Pharmacological Potential

Mitogen-activated protein kinase (MAPK) cascades are evolutionarily conserved signaling pathways that play essential roles in transducing extracellular environmental signals into diverse cellular responses to maintain homeostasis. These pathways are classically organized into an architecture of three sequentially acting protein kinases: a MAPK kinase kinase that phosphorylates and activates a MAPK kinase, which in turn phosphorylates and activates the effector MAPK. The activity of MAPKs is tightly regulated by phosphorylation of their activation loop, which can be modulated by positive and negative feedback mechanisms to control the amplitude and duration of the signal. The signaling outcomes of MAPK pathways are further regulated by interactions of MAPKs with scaffolding and regulatory proteins. Accumulating evidence indicates that, in addition to these mechanisms, MAPK signaling is commonly regulated by ubiquitin-proteasome system (UPS)-mediated control of the stability and abundance of MAPK pathway components. Notably, the biologic activity of some MAPKs appears to be regulated mainly at the level of protein turnover. Recent studies have started to explore the potential of targeted protein degradation as a powerful strategy to investigate the biologic functions of individual MAPK pathway components and as a new therapeutic approach to overcome resistance to current small-molecule kinase inhibitors. Here, we comprehensively review the mechanisms, physiologic importance, and pharmacological potential of UPS-mediated protein degradation in the control of MAPK signaling. SIGNIFICANCE STATEMENT: Accumulating evidence highlights the importance of targeted protein degradation by the ubiquitin-proteasome system in regulating and fine-tuning the signaling output of mitogen-activated protein kinase (MAPK) pathways. Manipulating protein levels of MAPK cascade components may provide a novel approach for the development of selective pharmacological tools and therapeutics.

Therapeutic Potential for CFTR Correctors in Autosomal Recessive Polycystic Kidney Disease

BACKGROUND & AIMS

Autosomal recessive polycystic kidney disease (ARPKD) is caused by mutations in PKHD1, encoding fibrocystin/polyductin (FPC). Severe disease occurs in perinates. Those who survive the neonatal period face a myriad of comorbidities, including systemic and portal hypertension, liver fibrosis, and hepatosplenomegaly. The goal here was to uncover therapeutic strategies for ARPKD.

METHODS

We used wild-type and an FPC-mutant cholangiocyte cell line in 3-dimenional cysts and in confluent monolayers to evaluate protein expression using western blotting and protein trafficking using confocal microscopy.

RESULTS

We found that the protein level of the cystic fibrosis transmembrane conductance regulator (CFTR) was downregulated. The levels of heat shock proteins (HSPs) were altered in the FPC-mutant cholangiocytes, with HSP27 being downregulated and HSP90 and HSP70 upregulated. FPC-mutant cholangiocytes formed cysts, but normal cells did not. Cyst growth could be reduced by increasing HSP27 protein levels, by HSP90 and HSP70 inhibitor treatments, by silencing HSP90 through messenger RNA inhibition, or by the novel approach of treating the cysts with the CFTR corrector VX-809. In wild-type cholangiocytes, CFTR is present in both apical and basolateral membranes. FPC malfunction resulted in altered colocalization of CFTR with both apical and basolateral membranes. Whereas, treatment with VX-809, increasing HSP27 or inhibiting HSP70 or HSP90 restored CFTR localization toward normal values.

CONCLUSIONS

FPC malfunction induces the formation of cysts, which are fueled by alterations in HSPs and in CFTR protein levels and miss-localization. We suggest that CFTR correctors, already in clinical use to treat cystic fibrosis, could also be used as a treatment for ARPKD.

Targeting heat shock protein 90 for anti-cancer drug development

INTRODUCTION

Heat shock proteins (HSPs) constitute a large family of proteins involved in protein folding and maturation. HSP expression is induced by heat shock or other stressors including cellular damage and hypoxia. The major groups, which are classified based on their molecular weight, include HSP27, HSP40, HSP60, HSP70, HSP90, and large HSP (HSP110 and glucose-regulated protein 170). HSPs play a significant role in cellular proliferation, differentiation, survival, apoptosis, and carcinogenesis. The human HSP90 family consists of five members and has a strong association with cancer.

OBJECTIVES

The primary objective is to review the important functions of heat shock protein 90 in cancer, especially as an anti-cancer drug target.

RESULTS

The HSP90 proteins not only play important roles in cancer development, progression, and metastasis, but also have potential clinical use as biomarkers for cancer diagnosis or assessing disease progression, and as therapeutic targets for cancer therapy. In this chapter, we discuss the roles of HSP90 in cancer biology and pharmacology, focusing on HSP90 as an anti-cancer drug target. An understanding of the functions and molecular mechanisms of HSP90 is critical for enhancing the accuracy of cancer diagnosis as well as for developing more effective and less toxic chemotherapeutic agents.

CONCLUSION

We have provided an overview of the complex relationship between cancer and HSP90. HSP90 proteins play an important role in tumorigenesis and may be used as potential clinical biomarkers for the diagnosis and predicting prognostic outcome of patients with cancer. HSP90 proteins may be used as therapeutic targets for cancer therapy, prompting discovery and development of novel chemotherapeutic agents.

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.

Old and New Approaches to Target the Hsp90 Chaperone

The 90-kDa heat shock protein (Hsp90) is a molecular chaperone that ensures cellular proteostasis by maintaining the folding, stabilization, activation, and degradation of over 400 client proteins. Hsp90 is not only critical for routine protein maintenance in healthy cells, but also during states of cellular stress, such as cancer and neurodegenerative diseases. Due to its ability to affect phosphorylation of numerous client proteins, inhibition of Hsp90 has been an attractive anticancer approach since the early 1990's, when researchers identified a druggable target on the amino terminus of Hsp90 for a variety of cancers. Since then, 17 Hsp90 inhibitors that target the chaperone's Nterminal domain, have entered clinical trials. None, however, have been approved thus far by the FDA as a cancer monotherapy. In these trials, a major limitation observed with Hsp90 inhibition at the N-terminal domain was dose-limiting toxicities and relatively poor pharmacokinetic profiles. Despite this, preclinical and clinical research continues to show that Hsp90 inhibitors effectively target cancer cell death and decrease tumor progression supporting the rationale for the development of novel Hsp90 inhibitors. Here, we present an in-depth overview of the Hsp90 inhibitors used in clinical trials. Finally, we present current shifts in the field related to targeting the carboxy-terminal domain of Hsp90 as well as to the development of isoform-selective inhibitors as a means to bypass the pitfalls of current Hsp90 inhibitors and improve clinical trial outcomes.

Effect of Hsp90 Inhibitor KW-2478 on HepG2 Cells

OBJECTIVE

The objectives of this study were to investigate the effects of proliferation, apoptosis, cell cycle, invasion, and senescence of KW-2478 on HepG2 cells, and to explore the related mechanism of apoptosis and the cell cycle.

METHODS

HepG2 cells (hepatocellular carcinoma cells) were cultured with KW-2478, at different doses and for different times, in vitro. The MTT assay was used to detect the effect of KW-2478 on proliferation of HepG2 cells. Flow cytometry was used to determine the effects of KW-2478 on the cell cycle and apoptosis of HepG2 cells. The Transwell assay was used to determine the effect of KW-2478 on cell invasion. The β-galactosidase assay tested the effect of low-dose KW-2478 on the senescence of HepG2 cells. Western blotting and the quantitative polymerase chain reaction were used respectively to assess changes in protein and mRNA levels of related factors in HepG2 cells after the KW-2478 treatment.

RESULTS

KW-2478 significantly inhibited proliferation of HepG2 cells. KW-2478 induced apoptosis and cell cycle arrest of HepG2 cells, and inhibited the invasion of HepG2 cells; low dose KW-2478 promoted HepG2 senescence.

CONCLUSION

KW-2478 inhibited the proliferation of HepG2 cells, induced apoptosis and cell cycle arrest, inhibited invasion, and promoted senescence. KW-2478 affected the expression of related factors in the mitochondrial apoptotic signaling and cell cycle-related regulatory pathways. KW-2478 downregulated the expression of STAT3, which is a key factor in the JAK-STAT pathway, indicating that KW-2478 may affect the function of HepG2 cells by downregulating STAT3.

Design and Synthesis of Fungal-Selective Resorcylate Aminopyrazole Hsp90 Inhibitors

The molecular chaperone Hsp90, essential in all eukaryotes, plays a multifaceted role in promoting survival, virulence, and drug resistance across diverse pathogenic fungal species. The chaperone is also critically important, however, to the pathogen's human host, preventing the use of known clinical Hsp90 inhibitors in antifungal applications due to concomitant host toxicity issues. With the goal of developing Hsp90 inhibitors with acceptable therapeutic indices for the treatment of invasive fungal infections, we initiated a program to design and synthesize potent inhibitors with selective activity against fungal Hsp90 isoforms over their human counterparts. Building on our previously reported derivatization of resorcylate natural products to produce fungal-selective compounds, we have developed a series of synthetic aminopyrazole-substituted resorcylate amides with broad, potent, and fungal-selective Hsp90 inhibitory activity. Herein we describe the synthesis of this series, as well as biochemical structure-activity relationships driving selectivity for the Hsp90 isoforms expressed by Cryptococcus neoformans and Candida albicans, two pathogenic fungi of major clinical importance.

Inhibition of HSP90 overcomes melphalan resistance through downregulation of Src in multiple myeloma cells

Multiple myeloma (MM) is the second most common hematologic malignancy. In spite of the development of new therapeutic agents, MM remains incurable due to multidrug resistance (MDR) and the 5-year survival rate is approximately 50%. Thus, further study is needed to investigate the mechanism of MDR and improve MM prognosis. Heat shock protein 90 (HSP90) is a molecular chaperone that is responsible for the stability of a number of client proteins, most of which are involved in tumor progression. Therefore, HSP90 inhibitors represent potential new therapeutic agents for cancer. Furthermore, inhibition of HSP90 leads to degradation of client proteins, overcoming acquired anti-cancer drug resistance. In this study, we assessed the role of HSP90 in MDR using established melphalan-resistant MM cells. We found that expression of HSP90 was higher in melphalan-resistant MM cells than in parent cells and that HSP90 inhibitors KW-2478 and NUV-AUY922 restored drug sensitivity to the level observed in parent cells. Activation of the unfolded protein response is a hallmark of MM, and expression of endoplasmic reticulum stress signaling molecules is reduced in melphalan-resistant cells; however, KW-2478 did not affect endoplasmic reticulum stress signaling. We demonstrated that treatment with KW-2478 decreased expression of Src, a client of HSP90, and suppressed the activity of ERK, Akt, and NF-κB. Our findings indicate that inhibition of HSP90 results in suppression of Src and its downstream effectors, including ERK, Akt, and NF-κB, and therefore that HSP90 inhibitors could be useful for treatment of MDR MM.

Bortezomib promotes apoptosis of multiple myeloma cells by regulating HSP27

The aim of the present study was to investigate the effect of bortezomib on heat shock protein 27 (HSP27) in multiple myeloma (MM) and provide a potential new target for clinical treatment. Peripheral blood was collected from 50 normal subjects and 50 patients with newly diagnosed MM and the expression of HSP27 was detected by ELISA. The changes of HSP27 after conventional vincristine, doxorubicin and dexamethasone (VAD) chemotherapy, and bortezomib plus VAD were compared. The effect of bortezomib on U266 cell proliferation and apoptosis was detected using a Cell Counting Kit‑8 assay and Annexin V‑FITC/propidium iodide double staining with flow cytometry. The content of HSP27 following bortezomib treatment was determined by ELISA. Western blot analysis and reverse transcription‑quantitative PCR were used to detect the mRNA and protein expression of HSP27, Bax and Bcl‑2. HSP27 expression was increased in patients with MM compared with healthy control subjects, and the expression was increased as the cancer progressed (P<0.05). Compared with the VAD chemotherapy group, the bortezomib plus VAD chemotherapy regimen significantly inhibited the expression of HSP27 (P<0.05), and the content of HSP27 was decreased in patients in which treatment was effective compared to those patients that exhibited disease progression (P<0.05). The efficacy of the treatment regimes was not associated with age or gender. Compared with the control group, bortezomib or OGX‑427 (HSP27 inhibitor) treatment inhibited U266 cell proliferation, promoted U266 cell apoptosis (P<0.05) and significantly decreased HSP27 expression (P<0.05). Furthermore, the expression of HSP27 and Bcl‑2 was significantly decreased, while the expression of Bax was increased by bortezomib and OGX‑427 (P<0.05). There was no significant difference between the bortezomib and OGX‑427 group in the in vitro analysis. HSP27 was positively correlated with Bcl‑2 expression and negatively correlated with Bax expression in U266 cells. In conclusion, bortezomib promotes the apoptosis of MM cells, potentially by downregulating the expression of HSP27, providing a potential novel target for the clinical treatment of multiple myeloma.

Traditional and Novel Mechanisms of Heat Shock Protein 90 (HSP90) Inhibition in Cancer Chemotherapy Including HSP90 Cleavage

HSP90 is a molecular chaperone that increases the stability of client proteins. Cancer cells show higher HSP90 expression than normal cells because many client proteins play an important role in the growth and survival of cancer cells. HSP90 inhibitors mainly bind to the ATP binding site of HSP90 and inhibit HSP90 activity, and these inhibitors can be distinguished as ansamycin and non-ansamycin depending on the structure. In addition, the histone deacetylase inhibitors inhibit the activity of HSP90 through acetylation of HSP90. These HSP90 inhibitors have undergone or are undergoing clinical trials for the treatment of cancer. On the other hand, recent studies have reported that various reagents induce cleavage of HSP90, resulting in reduced HSP90 client proteins and growth suppression in cancer cells. Cleavage of HSP90 can be divided into enzymatic cleavage and non-enzymatic cleavage. Therefore, reagents inducing cleavage of HSP90 can be classified as another class of HSP90 inhibitors. We discuss that the cleavage of HSP90 can be another mechanism in the cancer treatment by HSP90 inhibition.

Design, Synthesis and Pharmacological Evaluation of Novel Hsp90N-terminal Inhibitors Without Induction of Heat Shock Response

Heat shock protein 90 (Hsp90) is a potential oncogenic target. However, Hsp90 inhibitors in clinical trial induce heat shock response, resulting in drug resistance and inefficiency. In this study, we designed and synthesized a series of novel triazine derivatives (A1‐26, B1‐13, C1‐23) as Hsp90 inhibitors. Compound A14 directly bound to Hsp90 in a different manner from traditional Hsp90 inhibitors, and degraded client proteins, but did not induce the concomitant activation of Hsp72. Importantly, A14 exhibited the most potent anti‐proliferation ability by inducing autophagy, with the IC₅₀ values of 0.1 μM and 0.4 μM in A549 and SK‐BR‐3 cell lines, respectively. The in  vivo study demonstrated that A14 could induce autophagy and degrade Hsp90 client proteins in tumor tissues, and exhibit anti‐tumor activity in A549 lung cancer xenografts. Therefore, the compound A14 with potent antitumor activity and unique pharmacological characteristics is a novel Hsp90 inhibitor for developing anticancer agent without heat shock response.

A phase I/II study of KW-2478, an Hsp90 inhibitor, in combination with bortezomib in patients with relapsed/refractory multiple myeloma

Background:

KW-2478 is a novel non-ansamycin Hsp90 inhibitor with modest single-agent activity in relapsed/refractory myeloma but which shows synergistic antimyeloma activity with bortezomib (BTZ) in preclinical studies. This study determined the safety, preliminary clinical activity, and pharmacokinetics of KW-2478, an Hsp90 inhibitor, in combination with BTZ in patients with relapsed/refractory multiple myeloma (MM).

Methods:

Phase I dose escalation determined the recommended phase II dose (RP2D) of KW-2478 plus BTZ, which was then used during phase II.

Results:

The maximum tolerated dose was not reached during phase I and the RP2D was KW-2478 175 mg m⁻² plus BTZ 1.3 mg m⁻² on days 1, 4, 8, and 11 every 3 weeks. In the efficacy evaluable phase I/II population treated at the RP2D (n=79), the objective response rate was 39.2% (95% confidence interval: 28.4–50.9%), clinical benefit rate 51.9% (40.4–63.3%), median progression-free survival 6.7 (5.9-not reached (NR)) months, and median duration of response 5.5 (4.9-NR) months. In the phase I/II safety population (n=95), the most frequently observed treatment-related grade 3/4 adverse events were diarrhoea, fatigue, and neutropenia (each in 7.4% of patients), and nausea and thrombocytopenia (each in 5.3%).

Conclusions:

KW-2478 plus BTZ was well tolerated with no apparent overlapping toxicity in patients with relapsed/refractory MM. The antimyeloma activity of KW-2478 in combination with BTZ as scheduled in this trial appeared relatively modest; however, the good tolerability of the combination would support further exploration of alternate dosing schedules and combinations.

A lowered 26S proteasome activity correlates with mantle lymphoma cell lines resistance to genotoxic stress

Background

Mantle cell lymphoma (MCL) is a B-cell hemopathy characterized by the t(11;14) translocation and the aberrant overexpression of cyclin D1. This results in an unrestrained cell proliferation. Other genetic alterations are common in MCL cells such as SOX11 expression, mutations of ATM and/or TP53 genes, activation of the NF-κB signaling pathway and NOTCH receptors. These alterations lead to the deregulation of the apoptotic machinery and resistance to drugs. We observed that among a panel of MCL cell lines, REC1 cells were resistant towards genotoxic stress. We studied the molecular basis of this resistance.

Methods

We analyzed the cell response regarding apoptosis, senescence, cell cycle arrest, DNA damage response and finally the 26S proteasome activity following a genotoxic treatment that causes double strand DNA breaks.

Results

MCL cell lines displayed various sensitivity/resistance towards genotoxic stress and, in particular, REC1 cells did not enter apoptosis or senescence after an etoposide treatment. Moreover, the G2/M cell cycle checkpoint was deficient in REC1 cells. We observed that three main actors of apoptosis, senescence and cell cycle regulation (cyclin D1, MCL1 and CDC25A) failed to be degraded by the proteasome machinery in REC1 cells. We ruled out a default of the βTrCP E3-ubiquitine ligase but detected a lowered 26S proteasome activity in REC1 cells compared to other cell lines.

Conclusion

The resistance of MCL cells to genotoxic stress correlates with a low 26S proteasome activity. This could represent a relevant biomarker for a subtype of MCL patients with a poor response to therapies and a high risk of relapse.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-017-3530-z) contains supplementary material, which is available to authorized users.

Design and synthesis of neolamellarin a derivatives targeting heat shock protein 90

In this study, we designed and synthesized a novel family of neolamellarin A derivatives that showed high inhibitory activity toward heat shock protein 90 (Hsp90), a kinase associated with cell proliferation. The 3,4-bis(catechol)pyrrole scaffold and the benzyl group with methoxy modification at N position of pyrrole are essential to the Hsp90 inhibitory activity and cytotoxicity of these compounds. Western blot analysis demonstrated that these compounds induced dramatic depletion of the examined client proteins of Hsp90, and accelerated cancer cell apoptosis. Docking simulations suggested that the binding mode of 9p was similar to that of the VER49009, a potent inhibitor of Hsp90. Further molecular dynamics simulation indicated that the hydrophobic interactions as well as the hydrogen bonds contributed to the high affinity of 9p to Hsp90.

Heat Shock Protein (HSP) Drug Discovery and Development: Targeting Heat Shock Proteins in Disease

Heat shock proteins (HSPs) present as a double edged sword. While they play an important role in maintaining protein homeostasis in a normal cell, cancer cells have evolved to co-opt HSP function to promote their own survival. As a result, HSPs such as HSP90 have attracted a great deal of interest as a potential anticancer target. These efforts have resulted in over 20 distinct compounds entering clinical evaluation for the treatment of cancer. However, despite the potent anticancer activity demonstrated in preclinical models, to date no HSP90 inhibitor has obtained regulatory approval. In this review we discuss the unique challenges faced in targeting HSPs that have likely contributed to their lack of progress in the clinic and suggest ways to overcome these so that the enormous potential of these compounds to benefit patients can finally be realized. We also provide a guideline for the future development of HSP-targeted agents based on the many lessons learned during the last two decades in developing HSP90 inhibitors.

Targeting the entry region of Hsp90's ATP binding pocket with a novel 6,7-dihydrothieno[3,2-c]pyridin-5(4H)-yl amide

The molecular chaperone Hsp90 plays an important role in cancer cell survival and proliferation by regulating the maturation and stabilization of numerous oncogenic proteins. Due to its potential to simultaneously disable multiple signaling pathways, Hsp90 has emerged as an attractive therapeutic target for cancer treatment. In this study, the design, synthesis, and biological evaluation of a series of Hsp90 inhibitors are described. Among the synthetic compounds, 6,7-dihydrothieno [3,2-c]pyridin-5(4H)-yl amide 19 exhibits a remarkable binding affinity to the N-terminus of Hsp90 in a fluorescence polarization (FP) binding assay (IC₅₀ = 50.3 nM). Furthermore, it effectively inhibits the proliferation of H1975 non-small cell lung cancer (NSCLC) and Skbr3 breast cancer cell lines with GI₅₀ values of 0.31 μM and 0.11 μM, respectively. Compound 19 induces the degradation of the Hsp90 client proteins including EGFR, Her2, Met, c-Raf, and Akt, and consequently promotes apoptotic cancer cell death. Compound 19 also inhibits the growth of H1975 xenografts in NOD-scid IL2R gamma^null mice without any apparent body-weight loss. The immunohistologic evaluation indicates that compound 19 decreases the expression of Akt in xenograft tumor tissue via an inhibition of the Hsp90 chaperon function. Additionally, the cytochrome P450 assay indicates that compound 19 has no effect on the activities of five major P450 isoforms (IC₅₀ > 50 μM for 1A2, 2C9, 2C19, 2D6, and 3A), suggesting that clinical interactions between compound 19 and the substrate drugs of the five major P450 isoforms are not expected. Overall, compound 19 represents a new class of Hsp90 inhibitor with its 6,7-dihydrothieno[3,2-c]pyridin-5(4H)-yl-amide structure, and it has the therapeutic potential to overcome drug resistance in cancer chemotherapy.

Targeting Cell Survival Proteins for Cancer Cell Death

Escaping from cell death is one of the adaptations that enable cancer cells to stave off anticancer therapies. The key players in avoiding apoptosis are collectively known as survival proteins. Survival proteins comprise the Bcl-2, inhibitor of apoptosis (IAP), and heat shock protein (HSP) families. The aberrant expression of these proteins is associated with a range of biological activities that promote cancer cell survival, proliferation, and resistance to therapy. Several therapeutic strategies that target survival proteins are based on mimicking BH3 domains or the IAP-binding motif or competing with ATP for the Hsp90 ATP-binding pocket. Alternative strategies, including use of nutraceuticals, transcriptional repression, and antisense oligonucleotides, provide options to target survival proteins. This review focuses on the role of survival proteins in chemoresistance and current therapeutic strategies in preclinical or clinical trials that target survival protein signaling pathways. Recent approaches to target survival proteins-including nutraceuticals, small-molecule inhibitors, peptides, and Bcl-2-specific mimetic are explored. Therapeutic inventions targeting survival proteins are promising strategies to inhibit cancer cell survival and chemoresistance. However, complete eradication of resistance is a distant dream. For a successful clinical outcome, pretreatment with novel survival protein inhibitors alone or in combination with conventional therapies holds great promise.

Targeting Cell Survival Proteins for Cancer Cell Death

Escaping from cell death is one of the adaptations that enable cancer cells to stave off anticancer therapies. The key players in avoiding apoptosis are collectively known as survival proteins. Survival proteins comprise the Bcl-2, inhibitor of apoptosis (IAP), and heat shock protein (HSP) families. The aberrant expression of these proteins is associated with a range of biological activities that promote cancer cell survival, proliferation, and resistance to therapy. Several therapeutic strategies that target survival proteins are based on mimicking BH3 domains or the IAP-binding motif or competing with ATP for the Hsp90 ATP-binding pocket. Alternative strategies, including use of nutraceuticals, transcriptional repression, and antisense oligonucleotides, provide options to target survival proteins. This review focuses on the role of survival proteins in chemoresistance and current therapeutic strategies in preclinical or clinical trials that target survival protein signaling pathways. Recent approaches to target survival proteins-including nutraceuticals, small-molecule inhibitors, peptides, and Bcl-2-specific mimetic are explored. Therapeutic inventions targeting survival proteins are promising strategies to inhibit cancer cell survival and chemoresistance. However, complete eradication of resistance is a distant dream. For a successful clinical outcome, pretreatment with novel survival protein inhibitors alone or in combination with conventional therapies holds great promise.

CPUY201112, a novel synthetic small-molecule compound and inhibitor of heat shock protein Hsp90, induces p53-mediated apoptosis in MCF-7 cells

Heat-shock protein 90 (Hsp90) is highly expressed in many tumor cells and is associated with the maintenance of malignant phenotypes. Targeting Hsp90 has had therapeutic success in both solid and hematological malignancies, which has inspired more studies to identify new Hsp90 inhibitors with improved clinical efficacy. Using a fragment-based approach and subsequent structural optimization guided by medicinal chemistry principles, we identified the novel compound CPUY201112 as a potent Hsp90 inhibitor. It binds to the ATP-binding pocket of Hsp90 with a kinetic dissociation (K_d) constant of 27 ± 2.3 nM. It also exhibits potent in vitro antiproliferative effects in a range of solid tumor cells. In MCF-7 cells with high Hsp90 expression, CPUY201112 induces the degradation of Hsp90 client proteins including HER-2, Akt, and c-RAF. We prove that treating MCF-7 cells with CPUY201112 results in cell cycle arrest and apoptosis through the wild-type (wt) p53 pathway. CPUY201112 also synergizes with Nutlin-3a to induce cancer cell apoptosis. CPUY201112 significantly inhibited the growth of MCF-7 xenografts in nude mice without apparent body weight loss. These results demonstrate that CPUY201112 is a novel Hsp90 inhibitor with potential use in treating wild-type p53 related cancers.

Phase I study of KW-2478, a novel Hsp90 inhibitor, in patients with B-cell malignancies

BACKGROUND

KW-2478 is a novel, non-ansamycin, non-purine heat-shock protein 90 (Hsp90) inhibitor.

METHODS

In this phase I, multicentre study, KW-2478 was administered intravenously over 1 h at doses ranging from 14 to 176 mg m(-2) once daily on days 1-5 of a 14-day cycle in a standard 3+3 design in 27 patients (22 with multiple myeloma and 5 with non-Hodgkin lymphoma). Patients enrolled had relapsed/refractory disease previously treated with ⩾2 regimens.

RESULTS

There were no dose-limiting toxicities, thus the maximum-tolerated dose was not reached. KW-2478 was well tolerated and did not manifest significant retinal or ocular toxicity. The most common treatment-related adverse events were diarrhoea (33.3%), fatigue (29.6%), headache (25.9%), hypertension (22.2%), nausea (14.8%), vomiting (7.4%), and dizziness (7.4%). Plasma concentrations peaked at the end of infusion and decayed in a biphasic manner with a terminal half-life of ∼6 h. Target inhibition was inferred from the increase in Hsp70 levels in peripheral blood mononuclear cells at doses ⩾71 mg m(-2). Twenty-four of 25 (96%) evaluable patients showed stable disease, with five being free of disease progression for ⩾6 months.

CONCLUSIONS

Preliminary clinical response data were encouraging and warrant further investigation of KW-2478 in combination regimens for relapsed/refractory B-cell malignancies.

Combination of a Selective HSP90α/β Inhibitor and a RAS-RAF-MEK-ERK Signaling Pathway Inhibitor Triggers Synergistic Cytotoxicity in Multiple Myeloma Cells

Heat shock protein (HSP)90 inhibitors have shown significant anti-tumor activities in preclinical settings in both solid and hematological tumors. We previously reported that the novel, orally available HSP90α/β inhibitor TAS-116 shows significant anti-MM activities. In this study, we further examined the combination effect of TAS-116 with a RAS-RAF-MEK-ERK signaling pathway inhibitor in RAS- or BRAF-mutated MM cell lines. TAS-116 monotherapy significantly inhibited growth of RAS-mutated MM cell lines and was associated with decreased expression of downstream target proteins of the RAS-RAF-MEK-ERK signaling pathway. Moreover, TAS-116 showed synergistic growth inhibitory effects with the farnesyltransferase inhibitor tipifarnib, the BRAF inhibitor dabrafenib, and the MEK inhibitor selumetinib. Importantly, treatment with these inhibitors paradoxically enhanced p-C-Raf, p-MEK, and p-ERK activity, which was abrogated by TAS-116. TAS-116 also enhanced dabrafenib-induced MM cytotoxicity associated with mitochondrial damage-induced apoptosis, even in the BRAF-mutated U266 MM cell line. This enhanced apoptosis in RAS-mutated MM triggered by combination treatment was observed even in the presence of bone marrow stromal cells. Taken together, our results provide the rationale for novel combination treatment with HSP90α/β inhibitor and RAS-RAF-MEK-ERK signaling pathway inhibitors to improve outcomes in patients with in RAS- or BRAF-mutated MM.

MYC-driven aggressive B-cell lymphomas: biology, entity, differential diagnosis and clinical management

MYC, a potent oncogene located at chromosome locus 8q24.21, was identified initially by its involvement in Burkitt lymphoma with t(8;14)(q24;q32). MYC encodes a helix-loop-helix transcription factor that accentuates many cellular functions including proliferation, growth and apoptosis. MYC alterations also have been identified in other mature B-cell neoplasms and are associated with aggressive clinical behavior. There are several regulatory factors and dysregulated signaling that lead to MYC up-regulation in B-cell lymphomas. One typical example is the failure of physiological repressors such as Bcl6 or BLIMP1 to suppress MYC over-expression. In addition, MYC alterations are often developed concurrently with other genetic alterations that counteract the proapoptotic function of MYC. In this review, we discuss the physiologic function of MYC and the role that MYC likely plays in the pathogenesis of B-cell lymphomas. We also summarize the role MYC plays in the diagnosis, prognostication and various strategies to detect MYC rearrangement and expression.

The 26S proteasome is a multifaceted target for anti-cancer therapies

Proteasomes play a critical role in the fate of proteins that are involved in major cellular processes, including signal transduction, gene expression, cell cycle, replication, differentiation, immune response, cellular response to stress, etc. In contrast to non-specific degradation by lysosomes, proteasomes are highly selective and destroy only the proteins that are covalently labelled with small proteins, called ubiquitins. Importantly, many diseases, including neurodegenerative diseases and cancers, are intimately connected to the activity of proteasomes making them an important pharmacological target. Currently, the vast majority of inhibitors are aimed at blunting the proteolytic activities of proteasomes. However, recent achievements in solving structures of proteasomes at very high resolution provided opportunities to design new classes of small molecules that target other physiologically-important enzymatic activities of proteasomes, including the de-ubiquitinating one. This review attempts to catalog the information available to date about novel classes of proteasome inhibitors that may have important pharmacological ramifications.

Natural Product Inspired N-Terminal Hsp90 Inhibitors: From Bench to Bedside?

The 90 kDa heat shock proteins (Hsp90) are responsible for the conformational maturation of nascent polypeptides and the rematuration of denatured proteins. Proteins dependent upon Hsp90 are associated with all six hallmarks of cancer. Upon Hsp90 inhibition, protein substrates are degraded via the ubiquitin-proteasome pathway. Consequentially, inhibition of Hsp90 offers a therapeutic opportunity for the treatment of cancer. Natural product inhibitors of Hsp90 have been identified in vitro, which have served as leads for the development of more efficacious inhibitors and analogs that have entered clinical trials. This review highlights the development of natural product analogs, as well as the development of clinically important inhibitors that arose from natural products.

Heat shock proteins in multiple myeloma

Heat shock proteins are molecular chaperones with a central role in protein folding and cellular protein homeostasis. They also play major roles in the development of cancer and in recent years have emerged as promising therapeutic targets. In this review, we discuss the known molecular mechanisms of various heat shock protein families and their involvement in cancer and in particular, multiple myeloma. In addition, we address the current progress and challenges in pharmacologically targeting these proteins as anti-cancer therapeutic strategies.

Understanding biology to tackle the disease: Multiple myeloma from bench to bedside, and back

Multiple myeloma (MM) is a cancer of antibody-producing plasma cells. The pathognomonic laboratory finding is a monoclonal immunoglobulin or free light chain in the serum and/or urine in association with bone marrow infiltration by malignant plasma cells. MM develops from a premalignant condition, monoclonal gammopathy of undetermined significance (MGUS), often via an intermediate stage termed smoldering multiple myeloma (SMM), which differs from active myeloma by the absence of disease-related end-organ damage. Unlike MGUS and SMM, active MM requires therapy. Over the past 6 decades, major advancements in the care of MM patients have occurred, in particular, the introduction of novel agents (ie, proteasome inhibitors, immunomodulatory agents) and the implementation of hematopoietic stem cell transplantation in suitable candidates. The effectiveness and good tolerability of novel agents allowed for their combined use in induction, consolidation, and maintenance therapy, resulting in deeper and more sustained clinical response and extended progression-free and overall survival. Previously a rapidly lethal cancer with few therapeutic options, MM is the hematologic cancer with the most novel US Food and Drug Administration-approved drugs in the past 15 years. These advances have resulted in more frequent long-term remissions, transforming MM into a chronic illness for many patients.

Progress in the discovery and development of heat shock protein 90 (Hsp90) inhibitors

The discovery and clinical development of heat shock protein 90 (Hsp90) inhibitors continue to progress. A number of Hsp90 inhibitors are in clinical trials, and preclinical discoveries of new chemotypes that bind to distinct regions in the protein as well as isoform selective compounds are active areas of research. This review will highlight progress in the field since 2010.

FGFR3 translocations in bladder cancer: differential sensitivity to HSP90 inhibition based on drug metabolism

Activating mutations and/or overexpression of FGFR3 are common in bladder cancer, making FGFR3 an attractive therapeutic target in this disease. In addition, FGFR3 gene rearrangements have recently been described that define a unique subset of bladder tumors. Here, a selective HSP90 inhibitor, ganetespib, induced loss of FGFR3-TACC3 fusion protein expression and depletion of multiple oncogenic signaling proteins in RT112 bladder cells, resulting in potent cytotoxicity comparable with the pan-FGFR tyrosine kinase inhibitor BGJ398. However, in contrast to BGJ398, ganetespib exerted pleiotropic effects on additional mitogenic and survival pathways and could overcome the FGFR inhibitor-resistant phenotype of FGFR3 mutant-expressing 97-7 and MHG-U3 cells. Combinatorial benefit was observed when ganetespib was used with BGJ398 both in vitro and in vivo. Interestingly, two additional FGFR3 fusion-positive lines (RT4 and SW480) retained sensitivity to HSP90 inhibitor treatment by the ansamycins 17-AAG and 17-DMAG yet displayed intrinsic resistance to ganetespib or AUY922, both second-generation resorcinol-based compounds. Both cell lines, compared with RT112, expressed considerably higher levels of endogenous UGT1A enzyme; this phenotype resulted in a rapid glucuronidation-dependent metabolism and subsequent efflux of ganetespib from SW780 cells, thus providing a mechanism to account for the lack of bioactivity.

IMPLICATIONS

Pharmacologic blockade of the molecular chaperone HSP90 represents a promising approach for treating bladder tumors driven by oncogenic gene rearrangements of FGFR3. Furthermore, UDP-glucuronosyltransferase enzyme expression may serve as a predictive factor for clinical response to resorcinol-based HSP90 inhibitors.

Discovery and Bioevaluation of Novel Pyrazolopyrimidine Analogs as Competitive Hsp90 Inhibitors Through Shape-Based Similarity Screening

Hsp90 as a promising therapeutic target for the treatment of cancer has received great attention. Many Hsp90 inhibitors such as BIIB021 and CUDC-305 have been in clinical. In this paper shape-based similarity screening through ROCS overlays on the basis of CUDC-305, BIIB021, PU-H71 and PU-3 were performed to discover HSP90 inhibitors. A set of 19 novel pyrazolopyrimidine analogues was identified and evaluated on enzyme level and cell-based level as Hsp90 inhibitors. The compound HDI4-04 with IC50 0.35 µM in the Hsp90 ATP hydrolysis assay exhibited potent cytotoxicity against five human cancer cell lines. Western blot analysis and Hsp70 luciferase reporter assay further confirmed that HDI4-04 targeted the Hsp90 protein folding machinery. And according to the biological assay, the SAR was discussed and summarized, which will guide us for further optimization of these compounds.

Contributions of co-chaperones and post-translational modifications towards Hsp90 drug sensitivity

Hsp90 is a molecular chaperone and important driver of stabilization and activation of several oncogenic proteins that are involved in the malignant transformation of tumor cells. Therefore, it is not surprising that Hsp90 has been reported to be a promising target for the treatment of several neoplasias, such as non-small-cell lung cancer and HER2-positive breast cancer. Hsp90 chaperone function depends on its ability to bind and hydrolyze ATP and Hsp90 inhibitors have been shown to compete with nucleotides for binding to Hsp90. Multiple factors, such as co-chaperones and post-translational modification, are involved in regulating Hsp90 ATPase activity. Here, the impact of post-translational modifications and co-chaperones on the efficacy of Hsp90 inhibitors are reviewed.

A preclinical assay for chemosensitivity in multiple myeloma

Accurate preclinical predictions of the clinical efficacy of experimental cancer drugs are highly desired but often haphazard. Such predictions might be improved by incorporating elements of the tumor microenvironment in preclinical models by providing a more physiological setting. In generating improved xenograft models, it is generally accepted that the use of primary tumors from patients are preferable to clonal tumor cell lines. Here we describe an interdisciplinary platform to study drug response in multiple myeloma, an incurable cancer of the bone marrow. This platform uses microfluidic technology to minimize the number of cells per experiment, while incorporating three-dimensional extracellular matrix and mesenchymal cells derived from the tumor microenvironment. We used sequential imaging and a novel digital imaging analysis algorithm to quantify changes in cell viability. Computational models were used to convert experimental data into dose-exposure-response "surfaces," which offered predictive utility. Using this platform, we predicted chemosensitivity to bortezomib and melphalan, two clinical multiple myeloma treatments, in three multiple myeloma cell lines and seven patient-derived primary multiple myeloma cell populations. We also demonstrated how this system could be used to investigate environment-mediated drug resistance and drug combinations that target it. This interdisciplinary preclinical assay is capable of generating quantitative data that can be used in computational models of clinical response, demonstrating its utility as a tool to contribute to personalized oncology.