Phase I/II Study of HSP90 Inhibitor AUY922 and Erlotinib for EGFR-Mutant Lung Cancer With Acquired Resistance to Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors

Chaperonin-containing TCP-1 subunit genes are potential prognostic biomarkers and are correlated with Th2 cell infiltration in lung adenocarcinoma: An observational study

A family of molecular chaperone complexes called chaperonin-containing T-complex protein 1 (TCP-1) subunit genes (CCTs) aids in the folding of numerous proteins. With regard to lung adenocarcinoma (LUAD), this study provided a thorough understanding of the diagnostic and prognostic use of CCTs. The expression of CCTs in LUAD was evaluated by using databases including UALCAN and the Gene Expression Omnibus. Immunohistochemistry (IHC) was conducted to validate the expression of CCTs in LUAD. The mutation in the CCTs was identified through the cBioPortal database, while promoter methylation was measured by the UALCAN database. The prognostic value of CCTs was evaluated using the PrognoScan analysis. The GEPIA2.0 database was used to measure the prognostic value of CCTs and associated Hub genes. Correlation analysis between CCTs expression in LUAD was based on the GEPIA2.0 database. The ROC curves, clinical correlation analysis, gene ontology, Kyoto Encyclopedia of Genes and Genome analysis, and immune cell infiltration analysis were downloaded from The Cancer Genome Atlas database and then analyzed and visualized using the R language. The STRING database was used for protein-protein interaction analysis. Upregulation of CCTs expression in patients with LUAD indicated advanced diseases and a poor prognosis. ROC curve analysis revealed that the CCTs may serve as diagnostic indicators. The functional enrichment analysis showed that CCTs were involved in the mitosis-mediated cell cycle process. Additionally, 10 hub genes associated with CCTs that were linked to LUAD prognosis and tumor progression were identified. Immune cell infiltration analysis showed that CCTs expression in tumor tissues tends to be related to T helper type 2 cell infiltration. This study revealed that CCTs may serve as valuable biomarkers for the diagnosis and targeted therapy of LUAD.

Combined treatment with cetuximab and STA9090 has synergistic anticancer effects on human non-small cell lung cancer

Cetuximab (CET), a human murine chimeric IgG monoclonal antibody and an inhibitor of epidermal growth factor receptor (EGFR), has been shown to be effective in treating various types of cancer. However, its use is hindered by limitations such as resistance development, variability in patient response, side effects, and challenges in biomarker identification. Therefore, CET is often combined with other targeted therapies or chemotherapies to enhance its effectiveness. In this study, we investigate the anticancer effects and underlying mechanisms of the combination of CET, an EGFR inhibitor, and STA9090, an inhibitor of heat shock protein 90 (Hsp90), in both in vitro and in vivo models of non-small cell lung cancer (NSCLC). The results demonstrate significantly stronger effects on NSCLC cells in response to combination therapy than to treatment with either agent alone, indicating that the combination of CET and STA9090 has potential synergistic effects. Additionally, the combination therapy inhibits tumor growth in a xenograft nude mouse model more effectively than treatment with either agent alone, suggesting improved efficacy when used together. Furthermore, the synergistic effects of the combination therapy are likely due to inactivation of the receptor tyrosine kinase (RTK) pathway, which is overly activated in cancer and contributes to tumor growth, angiogenesis, and metastasis. Consequently, our findings suggest that STA9090 has potent direct antitumor activity and synergizes with CET against NSCLC tumors. It is highly likely that these synergistic effects are mediated through RTK pathway inactivation caused by the combination. Therefore, our findings strongly and consistently support the potential synergistic effect of STA9090, an RTK inhibitor, in combination with EGFR-targeting agents.

Molecular Pathways Governing the Termination of Liver Regeneration

The liver has the unique capacity to regenerate, and up to 70% of the liver can be removed without detrimental consequences to the organism. Liver regeneration is a complex process involving multiple signaling networks and organs. Liver regeneration proceeds through three phases: the initiation phase, the growth phase, and the termination phase. Termination of liver regeneration occurs when the liver reaches a liver-to-body weight that is required for homeostasis, the so-called "hepatostat." The initiation and growth phases have been the subject of many studies. The molecular pathways that govern the termination phase, however, remain to be fully elucidated. This review summarizes the pathways and molecules that signal the cessation of liver regrowth after partial hepatectomy and answers the question, "What factors drive the hepatostat?" SIGNIFICANCE STATEMENT: Unraveling the pathways underlying the cessation of liver regeneration enables the identification of druggable targets that will allow us to gain pharmacological control over liver regeneration. For these purposes, it would be useful to understand why the regenerative capacity of the liver is hampered under certain pathological circumstances so as to artificially modulate the regenerative processes (e.g., by blocking the cessation pathways) to improve clinical outcomes and safeguard the patient's life.

Combination of navitoclax (Bcl-2 and Bcl-xL inhibitor) and Debio-0932 (Hsp90 inhibitor) suppresses the viability of prostate cancer cells via induction of apoptotic signaling pathway

Prostate cancer is one of the most common cancers in men. Given the diverse nature of prostate cancer and its tendency to respond differently to various treatments, combination therapies are often employed to enhance outcomes. In this study, the synergetic efficiency of chemotherapeutic drug Navitoclax and heat shock protein 90 (Hsp90) inhibitor Debio-0932 was evaluated in human prostate cancer cell line (PC3). Our results indicated that Navitoclax-Debio-0932 combination exhibited synergistic activity in PC3 cells at concentrations lower than IC50 values. The combination of Navitoclax and Debio-0932 decreased PC3 cell viability in a dose dependent manner at 48 h. To investigate the apoptotic potential of the Navitoclax-Debio-0932 combination against prostate cancer cells, the mRNA and protein expression levels of apoptotic and antiapoptotic markers (Bax, Bcl-2, Bcl-xL, Cyt-c, Apaf-1, Casp-3, Casp-7, and Casp-9) were measured using RT-PCR and ELISA assay. Furthermore, the cleavage activity of Casp-3 was determined by colorimetric assay. The results revealed that Navitoclax-Debio-0932 combination potently induced intrinsic apoptotic pathway in PC3 cells rather than using drugs alone. The combined treatment of Navitoclax and Debio-0932 displayed synergistic cytotoxic and apoptotic effects on prostate cancer cells, presenting a promising approach for combination therapy in prostate cancer.

HSP90 inhibition suppresses tumor glycolytic flux to potentiate the therapeutic efficacy of radiotherapy for head and neck cancer

Glycolytic metabolism may account for antitumor immunity failure. Pyruvate kinase M2 (PKM2) and platelet phosphofructokinase (PFKP), two key enzymes involved in the glycolytic pathway, are hyperactivated in head and neck squamous cell carcinoma (HNSCC). Using ganetespib as a drug model for heat shock protein 90 (HSP90) inhibition and combining results from clinical trials and animal treatment, we demonstrated that HSP90 inhibition leads to a blockade of glycolytic flux in HNSCC cells by simultaneously suppressing PKM2 and PFKP at both the transcriptional and posttranslational levels. Down-regulation of tumor glycolysis facilitates tumor infiltration of cytotoxic T cells via suppression of glycolysis-dependent interleukin-8 signaling. The addition of ganetespib to radiation attenuates radiation-induced up-regulation of PKM2 and PFKP and potentiates T cell-mediated antitumor immunity, resulting in a more potent antitumor effect than either treatment alone, providing a molecular basis for exploring the combination of HSP90 inhibitors with radiotherapy to improve outcomes for patients with HNSCC.

HSP90α is needed for the survival of rod photoreceptors and regulates the expression of rod PDE6 subunits

Heat shock protein 90 (HSP90) is an abundant molecular chaperone that regulates the stability of a small set of proteins essential in various cellular pathways. Cytosolic HSP90 has two closely related paralogs: HSP90α and HSP90β. Due to the structural and sequence similarities of cytosolic HSP90 paralogs, identifying the unique functions and substrates in the cell remains challenging. In this article, we assessed the role of HSP90α in the retina using a novel HSP90α murine knockout model. Our findings show that HSP90α is essential for rod photoreceptor function but was dispensable in cone photoreceptors. In the absence of HSP90α, photoreceptors developed normally. We observed rod dysfunction in HSP90α knockout at 2 months with the accumulation of vacuolar structures, apoptotic nuclei, and abnormalities in the outer segments. The decline in rod function was accompanied by progressive degeneration of rod photoreceptors that was complete at 6 months. The deterioration in cone function and health was a "bystander effect" that followed the degeneration of rods. Tandem mass tag proteomics showed that HSP90α regulates the expression levels of <1% of the retinal proteome. More importantly, HSP90α was vital in maintaining rod PDE6 and AIPL1 cochaperone levels in rod photoreceptor cells. Interestingly, cone PDE6 levels were unaffected. The robust expression of HSP90β paralog in cones likely compensates for the loss of HSP90α. Overall, our study demonstrated the critical need for HSP90α chaperone in the maintenance of rod photoreceptors and showed potential substrates regulated by HSP90α in the retina.

Inhibition of Heat Shock Factor 1 Signaling Decreases Hepatoblastoma Growth via Induction of Apoptosis

Although rare compared with adult liver cancers, hepatoblastoma (HB) is the most common pediatric liver malignancy, and its incidence is increasing. Currently, the treatment includes surgical resection with or without chemotherapy, and in severe cases, liver transplantation in children. The effort to develop more targeted, HB-specific therapies has been stymied by the lack of fundamental knowledge about HB biology. Heat shock factor 1 (HSF1), a transcription factor, is a canonical inducer of heat shock proteins, which act as chaperone proteins to prevent or undo protein misfolding. Recent work has shown a role for HSF1 in cancer beyond the canonical heat shock response. The current study found increased HSF1 signaling in HB versus normal liver. It showed that less differentiated, more embryonic tumors had higher levels of HSF1 than more differentiated, more fetal-appearing tumors. Most strikingly, HSF1 expression levels correlated with mortality. This study used a mouse model of HB to test the effect of inhibiting HSF1 early in tumor development on cancer growth. HSF1 inhibition resulted in fewer and smaller tumors, suggesting HSF1 is needed for aggressive tumor growth. Moreover, HSF1 inhibition also increased apoptosis in tumor foci. These data suggest that HSF1 may be a viable pharmacologic target for HB treatment.

Evaluation of the Heat Shock Protein 90 Inhibitor Ganetespib as a Sensitizer to Hyperthermia-Based Cancer Treatments

Simple Summary

Hyperthermia boosts the effects of radio- and chemotherapy regimens, but its clinical potential is hindered by the ability of (cancer) cells to activate a protective mechanism known as the heat stress response. Strategies that inhibit its activation or functions have the potential, therefore, to improve the overall efficacy of hyperthermia-based treatments. In this study, we evaluated the efficacy of the HSP90 inhibitor ganetespib in promoting the effects of radiotherapy or cisplatin combined with hyperthermia in vitro and in a cervix cancer mouse model.

Abstract

Hyperthermia is being used as a radio- and chemotherapy sensitizer for a growing range of tumor subtypes in the clinic. Its potential is limited, however, by the ability of cancer cells to activate a protective mechanism known as the heat stress response (HSR). The HSR is marked by the rapid overexpression of molecular chaperones, and recent advances in drug development make their inhibition an attractive option to improve the efficacy of hyperthermia-based therapies. Our previous in vitro work showed that a single, short co-treatment with a HSR (HSP90) inhibitor ganetespib prolongs and potentiates the effects of hyperthermia on DNA repair, enhances hyperthermic sensitization to radio- and chemotherapeutic agents, and reduces thermotolerance. In the current study, we first validated these results using an extended panel of cell lines and more robust methodology. Next, we examined the effects of hyperthermia and ganetespib on global proteome changes. Finally, we evaluated the potential of ganetespib to boost the efficacy of thermo-chemotherapy and thermo-radiotherapy in a xenograft murine model of cervix cancer. Our results revealed new insights into the effects of HSR inhibition on cellular responses to heat and show that ganetespib could be employed to increase the efficacy of hyperthermia when combined with radiation.

Targeting Heat-Shock Protein 90 in Cancer: An Update on Combination Therapy

Heat-shock protein 90 (HSP90) is an important molecule chaperone associated with tumorigenesis and malignancy. HSP90 is involved in the folding and maturation of a wide range of oncogenic clients, including diverse kinases, transcription factors and oncogenic fusion proteins. Therefore, it could be argued that HSP90 facilitates the malignant behaviors of cancer cells, such as uncontrolled proliferation, chemo/radiotherapy resistance and immune evasion. The extensive associations between HSP90 and tumorigenesis indicate substantial therapeutic potential, and many HSP90 inhibitors have been developed. However, due to HSP90 inhibitor toxicity and limited efficiency, none have been approved for clinical use as single agents. Recent results suggest that combining HSP90 inhibitors with other anticancer therapies might be a more advisable strategy. This review illustrates the role of HSP90 in cancer biology and discusses the therapeutic value of Hsp90 inhibitors as complements to current anticancer therapies.

Synthesis and Evaluation of Simplified Cruentaren A Analogues

The 90 kDa heat shock protein (Hsp90) belongs to a group of molecular chaperones that regulate homeostasis via the folding of nascent polypeptides into their biologically active proteins, many of which are involved in cancer development and progression. As a result, inhibition of Hsp90 is an exciting area of research for the treatment of cancer. However, most of the 18 Hsp90 N-terminal inhibitors evaluated in clinical trials exhibited deleterious side effects and toxicities. Cruentaren A is a natural product that manifests potent anticancer activity against various human cancer cell lines via disruption of interactions between Hsp90α and F₁F_O ATP synthase, which does not induce the pro-survival, heat shock response, a major limitation associated with current Hsp90 inhibitors. However, the development of cruentaren A as a new anticancer agent has been hindered by its complex structure. Herein, we systematically removed the functionalities present in fragment 2 of cruentaren A and incorporated some key structural modifications from previous work, which produced 12 simplified analogues. Our studies determined that all functional groups present in fragment 2 are essential for cruentaren A's anticancer activity.

Complex Crystal Structure Determination of Hsp90N-NVP-AUY922 and In Vitro Anti-NSCLC Activity of NVP-AUY922

New targeted chemotherapy agents greatly improved five-year survival in NSCLC patients, but which were susceptible to drug resistance. NVP-AUY922, terminated in phase II clinical trials, exhibited promising anti-NSCLC (non-small-cell lung cancer) activity targeting to Hsp90^N (heat shock protein), which demonstrated advantages in overcoming drug resistance as a broad-spectrum anti-cancer target. It was expected to develop novel anti-NSCLC drugs to overcome drug resistance by the structural optimization of NVP-AUY922. However, the absence of high-resolution complex crystal structure of Hsp90^N-NVP-AUY922 blocked the way. Herein, 1.59 Å-resolution complex crystal structure of Hsp90^N-NVP-AUY922 (PDB ID 6LTI) was successfully determined by X-ray diffraction. Meanwhile, there was a strong binding capability between NVP-AUY922 and its target Hsp90^N verified by TSA (ΔTm, -15.56 ± 1.78°C) and ITC (K _d, 5.10 ± 2.10 nM). Results by the complex crystal structure, TSA and ITC verified that NVP-AUY922 well accommodated in the ATP-binding pocket of Hsp90^N to disable the molecular chaperone activity of Hsp90. Therefore, NVP-AUY922 exhibited approving inhibitory activity on NSCLC cell line H1299 (IC₅₀, 2.85 ± 0.06 μM) by inhibiting cell proliferation, inducing cell cycle arrest and promoting cell apoptosis. At the basis of the complex crystal structure and molecular interaction analysis, thirty-two new NVP-AUY922 derivatives were further designed, and among which twenty-eight new ones display enhanced binding force with Hsp90^N by molecular docking evaluation. The results would promote anti-NSCLC new drug development to overcome drug resistance based on the lead compound NVP-AUY922.

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.

The heat shock response and small molecule regulators

The heat shock response (HSR) is a highly conserved cellular pathway that is responsible for stress relief and the refolding of denatured proteins [1]. When a host cell is exposed to conditions such as heat shock, ischemia, or toxic substances, heat shock factor-1 (HSF-1), a transcription factor, activates the genes that encode for the heat shock proteins (Hsps), which are a family of proteins that work alongside other chaperones to relieve stress and refold proteins that have been denatured (Burdon, 1986) [2]. Along with the refolding of denatured proteins, Hsps facilitate the removal of misfolded proteins by escorting them to degradation pathways, thereby preventing the accumulation of misfolded proteins [3]. Research has indicated that many pathological conditions, such as diabetes, cancer, neuropathy, cardiovascular disease, and aging have a negative impact on HSR function and are commonly associated with misfolded protein aggregation [4,5]. Studies indicate an interplay between mitochondrial homeostasis and HSF-1 levels can impact stress resistance, proteostasis, and malignant cell growth, which further support the role of Hsps in pathological and metabolic functions [6]. On the other hand, Hsp activation by specific small molecules can induce the heat shock response, which can afford neuroprotection and other benefits [7]. This review will focus on the modulation of Hsps and the HSR as therapeutic options to treat these conditions.

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.

AUY922 induces retinal toxicity through attenuating TRPM1

Background

Ocular adverse events are common dose-limiting toxicities in cancer patients treated with HSP90 inhibitors, such as AUY922; however, the pathology and molecular mechanisms that mediate AUY922-induced retinal toxicity remain undescribed.

Methods

The impact of AUY922 on mouse retinas and cell lines was comprehensively investigated using isobaric tags for relative and absolute quantitation (iTRAQ)‑based proteomic profiling and pathway enrichment analysis, immunohistochemistry and immunofluorescence staining, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, MTT assay, colony formation assay, and western blot analysis. The effect of AUY922 on the Transient Receptor Potential cation channel subfamily M member 1 (TRPM1)-HSP90 chaperone complex was characterized by coimmunoprecipitation. TRPM1-regulated gene expression was analyzed by RNAseq analysis and gene set enrichment analysis (GSEA). The role of TRPM1 was assessed using both loss-of-function and gain-of-function approaches.

Results

Here, we show that the treatment with AUY922 induced retinal damage and cell apoptosis, dysregulated the photoreceptor and retinal pigment epithelium (RPE) layers, and reduced TRPM1 expression. Proteomic profiling and functional annotation of differentially expressed proteins reveals that those related to stress responses, protein folding processes, regulation of apoptosis, cell cycle and growth, reactive oxygen species (ROS) response, cell junction assembly and adhesion regulation, and proton transmembrane transport were significantly enriched in AUY922-treated cells. We found that AUY922 triggered caspase-3-dependent cell apoptosis, increased ROS production and inhibited cell growth. We determined that TRPM1 is a bona fide HSP90 client and characterized that AUY922 may reduce TRPM1 expression by disrupting the CDC37-HSP90 chaperone complex. Additionally, GSEA revealed that TRPM1-regulated genes were associated with retinal morphogenesis in camera-type eyes and the JAK-STAT cascade. Finally, gain-of-function and loss-of-function analyses validated the finding that TRPM1 mediated the cell apoptosis, ROS production and growth inhibition induced by AUY922.

Conclusions

Our study demonstrates the pathology of AUY922-induced retinal toxicity in vivo. TRPM1 is an HSP90 client, regulates photoreceptor morphology and function, and mediates AUY922-induced cytotoxicity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12929-021-00751-5.

Heat-activated nanomedicine formulation improves the anticancer potential of the HSP90 inhibitor luminespib in vitro

The heat shock protein 90 inhibitor, luminespib, has demonstrated potent preclinical activity against numerous cancers. However, clinical translation has been impeded by dose-limiting toxicities that have necessitated dosing schedules which have reduced therapeutic efficacy. As such, luminespib is a prime candidate for reformulation using advanced drug delivery strategies that improve tumor delivery efficiency and limit off-target side effects. Specifically, thermosensitive liposomes are proposed as a drug delivery strategy capable of delivering high concentrations of drug to the tumor in combination with other chemotherapeutic molecules. Indeed, this work establishes that luminespib exhibits synergistic activity in lung cancer in combination with standard of care drugs such as cisplatin and vinorelbine. While our research team has previously developed thermosensitive liposomes containing cisplatin or vinorelbine, this work presents the first liposomal formulation of luminespib. The physico-chemical properties and heat-triggered release of the formulation were characterized. Cytotoxicity assays were used to determine the optimal drug ratios for treatment of luminespib in combination with cisplatin or vinorelbine in non-small cell lung cancer cells. The formulation and drug combination work presented in this paper offer the potential for resuscitation of the clinical prospects of a promising anticancer agent.

Erlotinib and Onalespib Lactate Focused on EGFR Exon 20 Insertion Non-Small Cell Lung Cancer (NSCLC): A California Cancer Consortium Phase I/II Trial (NCI 9878)

This study examined the safety and tolerability of erlotinib and the heat shock protein 90 inhibitor onalespib in EGFR-mutant non–small cell lung cancer (NSCLC). The phase II component examined preliminary efficacy in epidermal growth factor receptor exon 20 insertion (EGFRex20ins) NSCLC. Overlapping toxicities, mainly diarrhea, limited the tolerability of the combination. EGFRex20ins circulating tumor DNA (ctDNA) was detected in the majority of patients; failure to clear ctDNA was consistent with lack of tumor response.

Erythrocyte-Membrane-Enveloped Biomineralized Metal-Organic Framework Nanoparticles Enable Intravenous Glucose-Responsive Insulin Delivery

A "closed-loop" insulin delivery system that can mimic the dynamic and glucose-responsive insulin secretion as islet β-cells is desirable for the therapy of type 1 and advanced type 2 diabetes mellitus (T1DM and T2DM). Herein, we introduced a kind of "core-shell"-structured glucose-responsive nanoplatform to achieve intravenous "smart" insulin delivery. A finely controlled one-pot biomimetic mineralization method was utilized to coencapsulate insulin, glucose oxidase (GOx), and catalase (CAT) into the ZIF-8 nanoparticles (NPs) to construct the "inner core", where an efficient enzyme cascade system (GOx/CAT group) served as an optimized glucose-responsive module that could rapidly catalyze glucose to yield gluconic acid to lower the local pH and effectively consume the harmful byproduct hydrogen peroxide (H₂O₂), inducing the collapse of pH-sensitive ZIF-8 NPs to release insulin. The erythrocyte membrane, a sort of natural biological derived lipid bilayer membrane which has intrinsic biocompatibility, was enveloped onto the surface of the "inner core" as the "outer shell" to protect them from elimination by the immune system, thus making the NPs intravenously injectable and could stably maintain a long-term existence in blood circulation. The in vitro and in vivo results indicate that our well-designed nanoplatform possesses an excellent glucose-responsive property and can maintain the blood glucose levels of the streptozocin (STZ)-induced type 1 diabetic mice at the normoglycemic state for up to 24 h after being intravenously administrated, confirming an intravenous insulin delivery strategy to overcome the deficits of conventional daily multiple subcutaneous insulin administration and offering a potential candidate for long-term T1DM treatment.

Persistence of myelofibrosis treated with ruxolitinib: biology and clinical implications

Activation of JAK-STAT signaling is one of the hallmarks of myelofibrosis, a myeloproliferative neoplasm that leads to inflammation, progressive bone marrow failure, and a risk of leukemic transformation. Around 90% of patients with myelofibrosis have a mutation in JAK2, MPL, or CALR: so-called 'driver' mutations that lead to activation of JAK2. Ruxolitinib, and other JAK2 inhibitors in clinical use, provide clinical benefit but do not have a major impact on the abnormal hematopoietic clone. This phenomenon is termed 'persistence', in contrast to usual patterns of resistance. Multiple groups have shown that type 1 inhibitors of JAK2, which bind the active conformation of the enzyme, lead to JAK2 becoming resistant to degradation with consequent accumulation of phospho-JAK2. In turn, this can lead to exacerbation of inflammatory manifestations when the JAK inhibitor is discontinued, and it may also contribute to disease persistence. The ways in which JAK2 V617F and CALR mutations lead to activation of JAK-STAT signaling are incompletely understood. We summarize what is known about pathological JAK-STAT activation in myelofibrosis and how this might lead to future novel therapies for myelofibrosis with greater disease-modifying potential.

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.

Identification of Predictive Biomarkers of Response to HSP90 Inhibitors in Lung Adenocarcinoma

Heat shock protein 90 (HSP90) plays an essential role in lung adenocarcinoma, acting as a key chaperone involved in the correct functioning of numerous highly relevant protein drivers of this disease. To this end, HSP90 inhibitors have emerged as promising therapeutic strategies, even though responses to them have been limited to date. Given the need to maximize treatment efficacy, the objective of this study was to use isobaric tags for relative and absolute quantitation (iTRAQ)-based proteomic techniques to identify proteins in human lung adenocarcinoma cell lines whose basal abundances were correlated with response to HSP90 inhibitors (geldanamycin and radicicol derivatives). From the protein profiles identified according to response, the relationship between lactate dehydrogenase B (LDHB) and DNA topoisomerase 1 (TOP1) with respect to sensitivity and resistance, respectively, to geldanamycin derivatives is noteworthy. Likewise, rhotekin (RTKN) and decaprenyl diphosphate synthase subunit 2 (PDSS2) were correlated with sensitivity and resistance to radicicol derivatives. We also identified a relationship between resistance to HSP90 inhibition and the p53 pathway by glucose deprivation. In contrast, arginine biosynthesis was correlated with sensitivity to HSP90 inhibitors. Further study of these outcomes could enable the development of strategies to improve the clinical efficacy of HSP90 inhibition in patients with lung adenocarcinoma.

DCZ5248, a novel dual inhibitor of Hsp90 and autophagy, exerts antitumor activity against colon cancer

Hsp90 is a potential therapeutic target for tumor, as it maintains the stability of a variety of proteins related to tumor development and progression. Autophagy is a self-degradation process to maintain cellular homeostasis and autophagy inhibitors can suppress tumor growth. In this study, we identified DCZ5248, a triazine derivative, was a dual inhibitor of both Hsp90 and late-autophagy with potent antitumor activity against colon cancer cells in vitro and in vivo. We showed that DCZ5248 (0.1-10 μM) induced dose-dependent degradation of Hsp90 client proteins (AKT, CDK4, CDK6 and RAF-1) in HCT 116 colon cancer cells through a proteasome-dependent pathway. Meanwhile, DCZ5248 (0.3 μM) induced cytoplasmic vacuole formation, LC3 II conversion, p62 protein upregulation, and inhibited autophagy at the late stage in the colon cancer cell lines tested. We further revealed that the inhibition of autophagy was achieved by impairing lysosomal functions through induction of lysosomal acidification and attenuation of lysosomal cathepsin activity. The modulation of autophagy by DCZ5248 was independent of Hsp90 inhibition as the autophagy inhibition was not blocked by Hsp90 knockdown. Importantly, inhibition of both Hsp90 function and autophagy by DCZ5248 induced G1-phase cell cycle arrest, apoptosis, and exerted potent antitumor activity against colon cancer cells both in vitro and in vivo. These findings demonstrate that DCZ5248 is a novel dual inhibitor of Hsp90 and autophagy with potential for colon cancer therapy.

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.

Combination Strategies to Improve Targeted Radionuclide Therapy

In recent years, targeted radionuclide therapy (TRT) has emerged as a promising strategy for cancer treatment. In contrast to conventional radiotherapy, TRT delivers ionizing radiation to tumors in a targeted manner, reducing the dose that healthy tissues are exposed to. Existing TRT strategies include the use of 177Lu-DOTATATE, 131I-metaiodobenzylguanidine, Bexxar, and Zevalin, clinically approved agents for the treatment of neuroendocrine tumors, neuroblastoma, and non-Hodgkin lymphoma, respectively. Although promising results have been obtained with these agents, clinical evidence acquired to date suggests that only a small percentage of patients achieves complete response. Consequently, there have been attempts to improve TRT outcomes through combinations with other therapeutic agents; such strategies include administering concurrent TRT and chemotherapy, and the use of TRT with known or putative radiosensitizers such as poly(adenosine diphosphate ribose) polymerase and mammalian-target-of-rapamycin inhibitors. In addition to potentially achieving greater therapeutic effects than the respective monotherapies, these strategies may lead to lower dosages or numbers of cycles required and, in turn, reduce unwanted toxicities. As of now, several clinical trials have been conducted to assess the benefits of TRT-based combination therapies, sometimes despite limited preclinical evidence being available in the public domain to support their use. Although some clinical trials have yielded promising results, others have shown no clear survival benefit from particular combination treatments. Here, we present a comprehensive review of combination strategies with TRT reported in the literature to date and evaluate their therapeutic potential.

An updated patent review of anticancer Hsp90 inhibitors (2013-present)

INTRODUCTION

Heat shock protein 90 (Hsp90) is one of the most critical chaperones amenable to mediating the folding and maturation of more than 300 client proteins. In normal cells, Hsp90 chaperone cycle is required for regulating multiple cellular processes to maintain homeostasis. However, extremely overexpressed Hsp90 in neoplastic cells results in the dysregulation of client proteins, many of which are indispensable to the accumulation of cancer hallmarks, such as infinite proliferation and increased invasiveness. Consequently, modulation of Hsp90 activity has been considered as a potential strategy for cancer treatment.

AREAS COVERED

This review recapitulated recent patents' progress in the development of Hsp90 inhibitors with potent antitumor activities during 2013 to present. Besides, the structural-activity relationships of the patented inhibitors and their structural similarity were also discussed.

EXPERT OPINION

Hsp90, as an anticancer target, has been investigated for several decades. The first generation of Hsp90 inhibitors exhibited potent antitumor activities in preclinical trials but were trapped in different phases of clinical trials. The second generation of Hsp90 inhibitors has been identified with increased specificity and security through structure modification. Moreover, these inhibitors may offer opportunities for studies of Hsp90 chaperone and development of Hsp90 inhibition therapy.

Low-Dose Hsp90 Inhibitor Selectively Radiosensitizes HNSCC and Pancreatic Xenografts

PURPOSE

Treatment approaches using Hsp90 inhibitors at their maximum tolerated doses (MTDs) have not produced selective tumor toxicity. Inhibition of Hsp90 activity causes degradation of client proteins including those involved in recognizing and repairing DNA lesions. We hypothesized that if DNA repair proteins were degraded by concentrations of an Hsp90 inhibitor below those required to cause nonspecific cytotoxicity, significant tumor-selective radiosensitization might be achieved.

EXPERIMENTAL DESIGN

Tandem mass tagged-mass spectrometry was performed to determine the effect of a subcytotoxic concentration of the Hsp90 inhibitor, AT13387 (onalespib), on global protein abundance. The effect of AT13387 on in vitro radiosensitization was assessed using a clonogenic assay. Pharmacokinetics profiling was performed in mice bearing xenografts. Finally, the effect of low-dose AT13387 on the radiosensitization of three tumor models was assessed.

RESULTS

A subcytotoxic concentration of AT13387 reduced levels of DNA repair proteins, without affecting the majority of Hsp90 clients. The pharmacokinetics study using one-third of the MTD showed 40-fold higher levels of AT13387 in tumors compared with plasma. This low dose enhanced Hsp70 expression in peripheral blood mononuclear cells (PBMCs), which is a biomarker of Hsp90 inhibition. Low dose monotherapy was ineffective, but when combined with radiotherapy, produced significant tumor growth inhibition.

CONCLUSIONS

This study shows that a significant therapeutic ratio can be achieved by a low dose of Hsp90 inhibitor in combination with radiotherapy. Hsp90 inhibition, even at a low dose, can be monitored by measuring Hsp70 expression in PBMCs in human studies.

Heat Shock Protein 90 (Hsp90)-Inhibitor-Luminespib-Loaded-Protein-Based Nanoformulation for Cancer Therapy

Drugs targeting heat shock protein 90 (Hsp90) have been extensively explored for their anticancer potential in advanced clinical trials. Nanoformulations have been an important drug delivery platform for the anticancer molecules like Hsp90 inhibitors. It has been reported that bovine serum albumin (BSA) nanoparticles (NPs) serve as carriers for anticancer drugs, which have been extensively explored for their therapeutic efficacy against cancers. Luminespib (also known as NVP-AUY922) is a new generation Hsp90 inhibitor that was introduced recently. It is one of the most studied Hsp90 inhibitors for a variety of cancers in Phase I and II clinical trials and is similar to its predecessors such as the ansamycin class of molecules. To our knowledge, nanoformulations for luminespib remain unexplored for their anticancer potential. In the present study, we developed aqueous dispensable BSA NPs for controlled delivery of luminespib. The luminespib-loaded BSA NPs were characterized by SEM, TEM, FTIR, XPS, UV-visible spectroscopy and fluorescence spectroscopy. The results suggest that luminespib interacts by non-covalent reversible interactions with BSA to form drug-loaded BSA NPs (DNPs). Our in vitro evaluations suggest that DNP-based aqueous nanoformulations can be used in both pancreatic (MIA PaCa-2) and breast (MCF-7) cancer therapy.

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.

Isoindoline scaffold-based dual inhibitors of HDAC6 and HSP90 suppressing the growth of lung cancer in vitro and in vivo

This study reports the synthesis of a series of 2-aroylisoindoline hydroxamic acids employing N-benzyl, long alkyl chain and acrylamide units as diverse linkers. In-vitro studies led to the identification of N-benzyl linker-bearing compound (10) and long chain linker-containing compound (17) as dual selective HDAC6/HSP90 inhibitors. Compound 17 displays potent inhibition of HDAC6 isoform (IC₅₀ = 4.3 nM) and HSP90a inhibition (IC₅₀ = 46.8 nM) along with substantial cell growth inhibitory effects with GI₅₀ = 0.76 μM (lung A549) and GI₅₀ = 0.52 μM (lung EGFR resistant H1975). Compound 10 displays potent antiproliferative activity against lung A549 (GI₅₀ = 0.37 μM) and lung H1975 cell lines (GI₅₀ = 0.13 μM) mediated through selective HDAC6 inhibition (IC₅₀ = 33.3 nM) and HSP90 inhibition (IC₅₀ = 66 nM). In addition, compound 17 also modulated the expression of signatory biomarkers associated with HDAC6 and HSP90 inhibition. In the in vivo efficacy evaluation in human H1975 xenografts, 17 induced slightly remarkable suppression of tumor growth both in monotherapy as well as the combination therapy with afatinib (20 mg/kg). Moreover, compound 17 could effectively reduce programmed death-ligand 1 (PD-L1) expression in IFN-γ treated lung H1975 cells in a dose dependent manner suggesting that dual inhibition of HDAC6 and HSP90 can modulate immunosuppressive ability of tumor area.

Advancing Aptamers as Molecular Probes for Cancer Theranostic Applications-The Role of Molecular Dynamics Simulation

Theranostics cover emerging technologies for cell biomarking for disease diagnosis and targeted introduction of drug ingredients to specific malignant sites. Theranostics development has become a significant biomedical research endeavor for effective diagnosis and treatment of diseases, especially cancer. An efficient biomarking and targeted delivery strategy for theranostic applications requires effective molecular coupling of binding ligands with high affinities to specific receptors on the cancer cell surface. Bioaffinity offers a unique mechanism to bind specific target and receptor molecules from a range of non-targets. The binding efficacy depends on the specificity of the affinity ligand toward the target molecule even at low concentrations. Aptamers are fragments of genetic materials, peptides, or oligonucleotides which possess enhanced specificity in targeting desired cell surface receptor molecules. Aptamer-target binding results from several inter-molecular interactions including hydrogen bond formation, aromatic stacking of flat moieties, hydrophobic interaction, electrostatic, and van der Waals interactions. Advancements in Systematic Evolution of Ligands by Exponential Enrichment (SELEX) assay has created the opportunity to artificially generate aptamers that specifically bind to desired cancer and tumor surface receptors with high affinities. This article discusses the potential application of molecular dynamics (MD) simulation to advance aptamer-mediated receptor targeting in targeted cancer therapy. MD simulation offers real-time analysis of the molecular drivers of the aptamer-receptor binding and generate optimal receptor binding conditions for theranostic applications. The article also provides an overview of different cancer types with focus on receptor biomarking and targeted treatment approaches, conventional molecular probes, and aptamers that have been explored for cancer cells targeting.

Epigenetic polypharmacology: A new frontier for epi-drug discovery

Recently, despite the great success achieved by the so-called "magic bullets" in the treatment of different diseases through a marked and specific interaction with the target of interest, the pharmacological research is moving toward the development of "molecular network active compounds," embracing the related polypharmacology approach. This strategy was born to overcome the main limitations of the single target therapy leading to a superior therapeutic effect, a decrease of adverse reactions, and a reduction of potential mechanism(s) of drug resistance caused by robustness and redundancy of biological pathways. It has become clear that multifactorial diseases such as cancer, neurological, and inflammatory disorders, may require more complex therapeutic approaches hitting a certain biological system as a whole. Concerning epigenetics, the goal of the multi-epi-target approach consists in the development of small molecules able to simultaneously and (often) reversibly bind different specific epi-targets. To date, two dual histone deacetylase/kinase inhibitors (CUDC-101 and CUDC-907) are in an advanced stage of clinical trials. In the last years, the growing interest in polypharmacology encouraged the publication of high-quality reviews on combination therapy and hybrid molecules. Hence, to update the state-of-the-art of these therapeutic approaches avoiding redundancy, herein we focused only on multiple medication therapies and multitargeting compounds exploiting epigenetic plus nonepigenetic drugs reported in the literature in 2018. In addition, all the multi-epi-target inhibitors known in literature so far, hitting two or more epigenetic targets, have been included.

Regulation of the EGFR Pathway by HSP90 Is Involved in the Pathogenesis of Cushing's Disease

PURPOSE

To investigate the role of heat-shock protein Hsp90 in adrenocorticotropic hormone (ACTH)-secreting cells, and to explore the potential clinical application of an inhibitor of Hsp90, 17-N-allylamino-17-demethoxygeldanamycin(17-AAG) in corticotropinomas [also known as "Cushing's disease" (CD)].

METHODS

Culture of mouse pituitary tumor [AtT-20/D16v-F2 (ATCC^® CRL-1795™)] cells and human pituitary ACTH-secreting tumor cells were employed. Hepatocellular carcinoma cell line (HLE) was used to evaluate EGFR inhibition by 17-AAG. Cell viability was evaluated using a commercial kit. The ACTH level was measured by a radioimmunoassay. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) was used to measure expression of proopiomelanocortin (POMC) mRNA. Western blotting was done to measure protein levels.

RESULTS

17-AAG suppressed the viability and proliferation, and promoted the apoptosis, of AtT-20/D16v-F2 cells. 17-AAG suppressed the synthesis and secretion of ACTH in AtT-20/D16v-F2 cells and down-regulated POMC transcription. 17-AAG acted in a similar pattern upon treatment with human pituitary ACTH-secreting tumor cells. Inhibition by 17-AAG was stronger in human pituitary ACTH-secreting tumor cells carrying the ubiquitin-specific protease-8 (USP8) mutant in comparison with cells carrying wild-type USP8.

CONCLUSIONS

The HSP90 inhibitor 17-AAG reduced the viability and secretory function of human pituitary ACTH-secreting tumor cells, and tumor cells carrying the USP8 mutant were more sensitive to 17-AAG than tumor cells carrying wild-type USP8. 17-AAG could be a potential treatment option for CD.

Chaperoning STAT3/5 by Heat Shock Proteins: Interest of Their Targeting in Cancer Therapy

While cells from multicellular organisms are dependent upon exogenous signals for their survival, growth, and proliferation, commitment to a specific cell fate requires the correct folding and maturation of proteins, as well as the degradation of misfolded or aggregated proteins within the cell. This general control of protein quality involves the expression and the activity of molecular chaperones such as heat shock proteins (HSPs). HSPs, through their interaction with the STAT3/STAT5 transcription factor pathway, can be crucial both for the tumorigenic properties of cancer cells (cell proliferation, survival) and for the microenvironmental immune cell compartment (differentiation, activation, cytokine secretion) that contributes to immunosuppression, which, in turn, potentially promotes tumor progression. Understanding the contribution of chaperones such as HSP27, HSP70, HSP90, and HSP110 to the STAT3/5 signaling pathway has raised the possibility of targeting such HSPs to specifically restrain STAT3/5 oncogenic functions. In this review, we present how HSPs control STAT3 and STAT5 activation, and vice versa, how the STAT signaling pathways modulate HSP expression. We also discuss whether targeting HSPs is a valid therapeutic option and which HSP would be the best candidate for such a strategy.

Chaperone biomarkers of lifespan and penetrance track the dosages of many other proteins

Many traits vary among isogenic individuals in homogeneous environments. In microbes, plants and animals, variation in the protein chaperone system affects many such traits. In the animal model C. elegans, the expression level of hsp-16.2 chaperone biomarkers correlates with or predicts the penetrance of mutations and lifespan after heat shock. But the physiological mechanisms causing cells to express different amounts of the biomarker were unknown. Here, we used an in vivo microscopy approach to dissect different contributions to cell-to-cell variation in hsp-16.2 expression in the intestines of young adult animals, which generate the most lifespan predicting signal. While we detected both cell autonomous intrinsic noise and signaling noise, we found both contributions were relatively unimportant. The major contributor to cell-to-cell variation in biomarker expression was general differences in protein dosage. The hsp-16.2 biomarker reveals states of high or low effective dosage for many genes.

Emerging insights of tumor heterogeneity and drug resistance mechanisms in lung cancer targeted therapy

The biggest hurdle to targeted cancer therapy is the inevitable emergence of drug resistance. Tumor cells employ different mechanisms to resist the targeting agent. Most commonly in EGFR-mutant non-small cell lung cancer, secondary resistance mutations on the target kinase domain emerge to diminish the binding affinity of first- and second-generation inhibitors. Other alternative resistance mechanisms include activating complementary bypass pathways and phenotypic transformation. Sequential monotherapies promise to temporarily address the problem of acquired drug resistance, but evidently are limited by the tumor cells' ability to adapt and evolve new resistance mechanisms to persist in the drug environment. Recent studies have nominated a model of drug resistance and tumor progression under targeted therapy as a result of a small subpopulation of cells being able to endure the drug (minimal residual disease cells) and eventually develop further mutations that allow them to regrow and become the dominant population in the therapy-resistant tumor. This subpopulation of cells appears to have developed through a subclonal event, resulting in driver mutations different from the driver mutation that is tumor-initiating in the most common ancestor. As such, an understanding of intratumoral heterogeneity-the driving force behind minimal residual disease-is vital for the identification of resistance drivers that results from branching evolution. Currently available methods allow for a more comprehensive and holistic analysis of tumor heterogeneity in that issues associated with spatial and temporal heterogeneity can now be properly addressed. This review provides some background regarding intratumoral heterogeneity and how it leads to incomplete molecular response to targeted therapies, and proposes the use of single-cell methods, sequential liquid biopsy, and multiregion sequencing to discover the link between intratumoral heterogeneity and early adaptive drug resistance. In summary, minimal residual disease as a result of intratumoral heterogeneity is the earliest form of acquired drug resistance. Emerging technologies such as liquid biopsy and single-cell methods allow for studying targetable drivers of minimal residual disease and contribute to preemptive combinatorial targeting of both drivers of the tumor and its minimal residual disease cells.

Activity of the Hsp90 inhibitor luminespib among non-small-cell lung cancers harboring EGFR exon 20 insertions

Background

There are currently no approved targeted therapies for non-small-cell lung cancer (NSCLC) patients with EGFR exon 20 insertions (ins20), a subgroup of EGFR mutations that are generally refractory to first/second generation EGFR inhibitors. We report the final results of a phase II trial evaluating the activity of the Hsp90 inhibitor luminespib (AUY922) in NSCLC patients with EGFR ins20.

Patients and methods

Twenty-nine patients with stage IV NSCLC with EGFR ins20 identified on local testing and at least one prior therapy were enrolled on the trial between August 2013 and October 2016. The primary end point was objective response rate (ORR), with a pre-determined target rate of effectiveness [defined as the rate of partial response (PR) plus stable disease (SD) lasting ≥3 months] of 20%. Secondary end points were PFS, overall survival (OS), safety and response by EGFR ins20 subtype.

Results

Among the 29 patients (18 females, median age 60 years) the ORR was 17%, median progression-free survival was 2.9 months (95% CI 1.4-5.6) and median OS (mOS) was 13 months (95% CI 4.9-19.5). The results exceeded the pre-determined target rate of effectiveness with 11/29 (38%) patients having a PR or an SD ≥3 months. The most common luminespib-related toxicities were diarrhea (83%), visual changes (76%) and fatigue (45%). All study treatment was stopped on 28 February 2017 due to dissolution of study drug availability; 3 patients were on treatment at study termination.

Conclusion

The study met its primary end point, suggesting that luminespib may be an active therapy for advanced NSCLC patients with EGFR ins20. Luminespib is generally well-tolerated, though reversible low-grade ocular toxicity is common. Further study of luminespib and other hsp90 inhibitors in this population is warranted.

Study registration (ClinicalTrials.gov)

NCT01854034.

Second-line treatment of EGFR T790M-negative non-small cell lung cancer patients

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are the currently recommended treatment for advanced EGFR mutation-positive non-small cell lung cancer (NSCLC). Acquired resistance inevitably develops, with the EGFR T790M mutation comprising approximately 55% of the mechanisms of resistance following first- or second-generation EGFR-TKI therapy (e.g. gefitinib, erlotinib, afatinib, and dacomitinib). Patients without T790M are a heterogeneous group for whom platinum-based chemotherapy is currently recommended as a second-line treatment. In addition to secondary mutations in EGFR (e.g. T790M), the currently known resistance mechanisms can be classified into the following three categories: bypass pathways, downstream signaling pathways, and histologic transformations. Given the evolving knowledge and convenience of diagnosing acquired resistance mechanisms by next-generation sequencing and liquid biopsy, exploratory studies targeting these resistance mechanisms and incorporating immunotherapy into the treatment paradigm have become the mainstream of future development. This review focuses on acquired resistance mechanisms other than T790M that develop after first- or second-generation EGFR-TKI therapy. Exploratory second-line treatments targeting resistance mechanisms as well as combination immunotherapy and chemotherapy in ongoing clinical trials are reviewed here. We also highlight the recent development of next-generation sequencing and liquid biopsy in this field.

PET Imaging of Receptor Tyrosine Kinases in Cancer

Overexpression and/or mutations of the receptor tyrosine kinase (RTK) subfamilies, such as epidermal growth factor receptors (EGFR) and vascular endothelial growth factor receptors (VEGFR), are closely associated with tumor cell growth, differentiation, proliferation, apoptosis, and cellular invasiveness. Monoclonal antibodies (mAb) and tyrosine kinase inhibitors (TKI) specifically inhibiting these RTKs have shown remarkable success in improving patient survival in many cancer types. However, poor response and even drug resistance inevitably occur. In this setting, the ability to detect and visualize RTKs with noninvasive diagnostic tools will greatly refine clinical treatment strategies for cancer patients, facilitate precise response prediction, and improve drug development. Positron emission tomography (PET) agents using targeted radioactively labeled antibodies have been developed to visualize tumor RTKs and are changing clinical decisions for certain cancer types. In the present review, we primarily focus on PET imaging of RTKs using radiolabeled antibodies with an emphasis on the clinical applications of these immunoPET probes. Mol Cancer Ther; 17(8); 1625-36. ©2018 AACR.

Roles of Extracellular HSPs as Biomarkers in Immune Surveillance and Immune Evasion

Extracellular heat shock proteins (ex-HSPs) have been found in exosomes, oncosomes, membrane surfaces, as well as free HSP in cancer and various pathological conditions, also known as alarmins. Such ex-HSPs include HSP90 (α, β, Gp96, Trap1), HSP70, and large and small HSPs. Production of HSPs is coordinately induced by heat shock factor 1 (HSF1) and hypoxia-inducible factor 1 (HIF-1), while matrix metalloproteinase 3 (MMP-3) and heterochromatin protein 1 are novel inducers of HSPs. Oncosomes released by tumor cells are a major aspect of the resistance-associated secretory phenotype (RASP) by which immune evasion can be established. The concepts of RASP are: (i) releases of ex-HSP and HSP-rich oncosomes are essential in RASP, by which molecular co-transfer of HSPs with oncogenic factors to recipient cells can promote cancer progression and resistance against stresses such as hypoxia, radiation, drugs, and immune systems; (ii) RASP of tumor cells can eject anticancer drugs, targeted therapeutics, and immune checkpoint inhibitors with oncosomes; (iii) cytotoxic lipids can be also released from tumor cells as RASP. ex-HSP and membrane-surface HSP (mHSP) play immunostimulatory roles recognized by CD91+ scavenger receptor expressed by endothelial cells-1 (SREC-1)+ Toll-like receptors (TLRs)+ antigen-presenting cells, leading to antigen cross-presentation and T cell cross-priming, as well as by CD94+ natural killer cells, leading to tumor cytolysis. On the other hand, ex-HSP/CD91 signaling in cancer cells promotes cancer progression. HSPs in body fluids are potential biomarkers detectable by liquid biopsies in cancers and tissue-damaged diseases. HSP-based vaccines, inhibitors, and RNAi therapeutics are also reviewed.

Impact of Heat Shock Protein 90 Inhibition on the Proteomic Profile of Lung Adenocarcinoma as Measured by Two-Dimensional Electrophoresis Coupled with Mass Spectrometry

Heat shock protein 90 (HSP90) is an important chaperone in lung adenocarcinoma, with relevant protein drivers such as EGFR (epidermal growth factor receptor) and EML4-ALK (echinoderm microtubule-associated protein-like protein4 fused to anaplastic lymphoma kinase) depending on it for their correct function, therefore HSP90 inhibitors show promise as potential treatments for lung adenocarcinoma. To study responses to its inhibition, HSP90 was pharmacologically interrupted by geldanamycin and resorcinol derivatives or with combined inhibition of HSP90 plus HSP70 in lung adenocarcinoma cell lines. Two-dimensional electrophoresis was performed to identify proteomic profiles associated with inhibition which will help to understand the biological basis for the responses. HSP90 inhibition resulted in altered protein profiles that differed according the treatment condition studied. Results revealed 254 differentially expressed proteins after treatments, among which, eukaryotic translation initiation factor3 subunit I (eIF3i) and citrate synthase demonstrated their potential role as response biomarkers. The differentially expressed proteins also enabled signalling pathways involved in responses to be identified; these included apoptosis, serine-glycine biosynthesis and tricarboxylic acid cycle. The proteomic profiles identified here contribute to an improved understanding of HSP90 inhibition and open possibilities for the detection of potential response biomarkers which will be essential to maximize treatment efficacy in lung adenocarcinoma.

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.

Luminespib plus pemetrexed in patients with non-squamous non-small cell lung cancer

BACKGROUND

Luminespib (AUY922) is a second-generation heat shock protein 90 (HSP90) inhibitor with demonstrated activity in non-small cell lung cancer (NSCLC). Since luminespib reduces levels of dihydrofolate reductase (DHFR), a key enzymatic target of pemetrexed, we assessed the safety and tolerability of luminespib in combination with pemetrexed in patients with previously treated metastatic non-squamous non-small cell lung cancer (NSCLC). We also sought to study the pharmacokinetics and correlate tumor dihydrofolate reductase (DHFR) expression with clinical response.

METHODS

Patients received weekly luminespib at either 40 mg/m², 55 mg/m², or 70 mg/m² according to a standard 3 + 3 dose-escalation design along with pemetrexed at 500 mg/m² followed by an expansion at the maximum tolerated dose (MTD).

RESULTS

Two-dose limiting toxicities (DLTs) were experienced in the 70 mg/m2 cohort, therefore the MTD was determined to be 55 mg/m². 69% (N = 9) of patients experienced ophthalmologic toxicity related to luminespib. Maximum serum concentration (Cmax) of luminespib was associated with increased grade 2 drug related adverse events (DRAEs) (r_s = 0.74, P <  0.01), with volume of distribution (V_D) inversely associated with the number of DRAEs (r_s = - 0.81, P =  0.004) and ophthalmologic related DRAEs (r_s = - 0.65, P =  0.04). The best response was partial response in one patient for 20 months, prior to expiration of all luminespib. Amongst patients treated at the MTD, the objective response rate was 14%.

CONCLUSION

In patients with previously treated metastatic NSCLC, the MTD of luminespib in combination with pemetrexed was 55 mg/m² per week. The combination of luminespib and pemetrexed demonstrated clinical activity. Tolerability of luminespib with pemetrexed is limited by ocular toxicity.

Heat shock factor 1 (HSF1)-targeted anticancer therapeutics: overview of current preclinical progress

INTRODUCTION

The heat shock factor 1 (HSF1) plays a pivotal role in guarding proteome stability or proteostasis by induction of heat shock proteins (HSPs). While HSF1 remains mostly latent in unstressed normal cells, it is constitutively active in malignant cells, rendering them addicted to HSF1 for their growth and survival. HSF1 affects tumorigenesis, cancer progression, and treatment resistance by preserving cancer proteostasis, thus suggesting disruption of HSF1 activity as a potential anticancer strategy. Areas covered: In this review, we focus on the HSF1 activation cycle and its interaction with HSPs, the role of HSF1 in oncogenesis, and development of HSF1-targeted drugs as a potential anticancer therapy for disrupting cancer proteostasis. Expert opinion: HSF1 systematically maintains proteostasis in malignant cancer cells. Although genomic instability is widely accepted as a hallmark of cancer, little is known about the role of proteostasis in cancer. Unveiling the complicated mechanism of HSF1 regulation, particularly in cancer cells, will enable further development of proteostasis-targeted anticancer therapy.

ABBREVIATIONS

AMPK: AMP-activated protein kinase; DBD: DNA-binding domain; HR-A/B; HR-C: heptad repeats; HSE: heat shock elements; HSF1: heat shock factor; HSPs: heat shock proteins; HSR: heat shock response; MEK: mitogen-activated protein kinase kinase; mTOR: mammalian target of rapamycin; NF1: neurofibromatosis type 1; P-TEFb: positive transcription elongation factor b; RD: regulatory domain; RNAi: RNA interference; TAD: transactivation domain; TRiC: TCP-1 ring complex.

Modulating protein-protein interaction networks in protein homeostasis

Protein-protein interactions (PPIs) occur in complex networks. These networks are highly dependent on cellular context and can be extensively altered in disease states such as cancer and viral infection. In recent years, there has been significant progress in developing inhibitors that target individual PPIs either orthosterically (at the interface) or allosterically. These molecules can now be used as tools to dissect PPI networks. Here, we review recent examples that highlight the use of small molecules and engineered proteins to probe PPIs within the complex networks that regulate protein homeostasis. Researchers have discovered multiple mechanisms to modulate PPIs involved in host/viral interactions, deubiquitinases, the ATPase p97/VCP, and HSP70 chaperones. However, few studies have evaluated the effect of such modulators on the target's network or have compared the biological implications of different modulation strategies. Such studies will have an important impact on next generation therapeutics.

HSP90: Enabler of Cancer Adaptation

The stability and function of many oncogenic mutant proteins depend on heat shock protein 90 (HSP90). This unique activity has inspired the exploration of HSP90 as an anticancer target for over two decades. Unfortunately, while clinical trials of highly optimized HSP90 inhibitors have demonstrated modest benefit for patients with advanced cancers, most commonly stabilization of disease, no HSP90 inhibitor has demonstrated sufficient efficacy to achieve FDA approval to date. This review discusses potential reasons for the limited success of these agents and how our increasingly sophisticated understanding of HSP90 suggests alternative, potentially more effective strategies for targeting it to treat cancers. First, we focus on insights gained from model organisms that suggest a fundamental role for HSP90 in supporting the adaptability and heterogeneity of cancers, key factors underlying their ability to evolve and acquire drug resistance. Second, we examine how HSP90’s role in promoting the stability of mutant proteins might be targeted in genetically unstable tumor cells to reveal their aberrant, foreign proteome to the immune system. Both of these emerging aspects of HSP90 biology suggest that the most effective use of HSP90 inhibitors may not be at high doses with the intent to kill cancer cells, but rather in combination with other molecularly targeted therapies at modest, non-heat shock-inducing exposures that limit the adaptive capacity of cancers.

First-in-Human Phase I Study of an Oral HSP90 Inhibitor, TAS-116, in Patients with Advanced Solid Tumors

HSP90 is involved in stability and function of cancer-related proteins. This study was conducted to define the MTD, safety, pharmacokinetics, pharmacodynamics, and preliminary antitumor efficacy of TAS-116, a novel class, orally available, highly selective inhibitor of HSP90. Patients with advanced solid tumors received TAS-116 orally once daily (QD, step 1) or every other day (QOD, step 2) in 21-day cycles. Each step comprised a dose escalation phase to determine MTD and an expansion phase at the MTD. In the dose escalation phase, an accelerated dose-titration design and a "3+3" design were used. Sixty-one patients were enrolled in Japan and the United Kingdom. MTD was determined to be 107.5 mg/m2/day for QD, and 210.7 mg/m2/day for QOD. In the expansion phase of step 1, TAS-116 was administered 5 days on/2 days off per week (QD × 5). The most common treatment-related adverse events included gastrointestinal disorders, creatinine increases, AST increases, ALT increases, and eye disorders. Eye disorders have been reported with HSP90 inhibitors; however, those observed with TAS-116 in the expansion phases were limited to grade 1. The systemic exposure of TAS-116 increased dose-proportionally with QD and QOD regimens. Two patients with non-small cell lung cancer and one patient with gastrointestinal stromal tumor (GIST) achieved a confirmed partial response. TAS-116 had an acceptable safety profile with some antitumor activity, supporting further development of this HSP90 inhibitor.This is a result from a first-in-human study, in which the HSP90 inhibitor TAS-116 demonstrated preliminary antitumor efficacy in patients with advanced solid tumors, including those with heavily pretreated GIST.

Prognostic value of the mRNA expression of members of the HSP90 family in non-small cell lung cancer

The aim of the present study was to investigate the potential prognostic value of members of the heat shock protein (HSP)90 family in non-small cell lung cancer (NSCLC) patients. The mRNA expression profiles of 1,926 NSCLC patients, which was available from the Kaplan-Meier plotter database, were included in the study. High expression of HSP90AA1 mRNA was significantly associated with a poorer rate of overall survival (OS) for all NSCLC patients [hazard ratio (HR), 1.21; 95% confidence interval (CI): 1.06–1.37; P=0.004], as well as for patients with adenocarcinoma (ADE; HR, 1.3; 95% CI: 1.02–1.65; P=0.034), but no significant correlation was identified for squamous cell carcinoma (SCC) patients (HR, 1.08; 95% CI: 0.85–1.38; P=0.51). High expression of HSP90AB1 and HSP90B1 mRNA was significantly associated with poorer rates of OS in lung SCC and ADE patients combined, as well as in lung ADE patients alone. By contrast, high expression of tumor necrosis factor receptor-associated protein 1 (TRAP1) mRNA was significantly associated with improved OS rates in all NSCLC patients combined (HR, 0.88; 95% CI: 0.77–0.99; P=0.041), as well as ADE patients. In stratified survival analysis, a high expression of HSP90AA1, HSP90AB1 and HSP90B1 predicted poor prognosis in stage I NSLCC patients, suggesting that these genes may serve as stage-independent prognostic indicators. As an elevated expression of HSP90AA1, HSP90AB1, HSP90B1 and TRAP1 was associated with poorer OS outcomes in patients with NSCLC, these HSP90 members may be potential prognostic biomarkers and drug targets for the treatment of NSCLC.

Combination therapies with HSP90 inhibitors against colorectal cancer

Oncogene stability and homeostasis mediated by the HSP90 chaperone is a crucial protection trait of cancer cells. Therefore, HSP90 represents an attractive therapeutic target for many cancers, including colorectal cancer. Although monotherapy has limited clinical efficacy, preclinical and early-phase clinical studies indicate improved antitumor activity when HSP90 inhibitors are combined with chemotherapies or targeted agents. This may be further improved with a biomarker-guided approach based on oncogenic HSP90 clients, or stratification based on the consensus molecular subtypes of colorectal cancer, suggesting a synergistic activity with 5-fluorouracil in preclinical models of the chemorefractory mesenchymal subtype. Furthermore, HSP90 inhibition may activate mechanisms to turn non-immunogenic tumors hot and improve their recognition by the immune system, suggesting synergy with immune checkpoint blockade.