The HSP90 inhibitor Onalespib exerts synergistic anti-cancer effects when combined with radiotherapy: an in vitro and in vivo approach

HSP90AA1 is an unfavorable prognostic factor for hepatocellular carcinoma and contributes to tumorigenesis and chemotherapy resistance

Hepatocellular carcinoma (HCC) is still one of the leading causes of tumor-related deaths. Accumulating evidence indicates that immunogenic cell death (ICD) could occur in tumor cells. However, ICD-related studies are limited in HCC. This study collected HCC RNA sequencing data from the Cancer Genome Atlas, International Cancer Genome Consortium, and Gene Expression Omnibus databases. R software was used to analyze the expression of ICD in HCC and to screen essential genes with prognostic value. qRT-PCR and WB determined the mRNA and protein expressions of hub gene. Cell viability assay, Clonal formation assay, and Live/dead staining assay were employed to determine the gene functions. After cross-analysis of differentially expressed genes (DEGs) and ICD-related genes (ICDRGs), 7 differentially expressed ICDRGs were identified in HCC. Of them, HSP90AA1, with the most excellent prognostic value in HCC, was selected, whose expression was also validated in public cohorts, cell lines, and clinical tissue samples. High HSP90AA1 expression indicated an inferior prognosis of HCC, and HSP90AA1 knockdown significantly suppressed cell viability and chemotherapy resistance of HCC. ICD-related gene HSP90AA1 was an unfavorable factor for HCC, and high HSP90AA1 expression contributed to tumor cell survival and chemotherapy resistance.

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

As a molecular chaperone, heat shock protein 90 (HSP90) plays important roles in the folding, stabilization, activation, and degradation of over 500 client proteins, and is extensively involved in cell signaling, proliferation, and survival. Thus, it has emerged as an important target in a variety of diseases, including cancer, neurodegenerative diseases, and viral infections. Therefore, targeted inhibition of HSP90 provides a valuable and promising therapeutic strategy for the treatment of HSP90-related diseases. This review aims to systematically summarize the progress of research on HSP90 inhibitors in the last five years, focusing on their structural features, design strategies, and biological activities. It will refer to the natural products and their derivatives (including novobiocin derivatives, deguelin derivatives, quinone derivatives, and terpenoid derivatives), and to synthetic small molecules (including resorcinol derivatives, pyrazoles derivatives, triazole derivatives, pyrimidine derivatives, benzamide derivatives, benzothiazole derivatives, and benzofuran derivatives). In addition, the major HSP90 small-molecule inhibitors that have moved into clinical trials to date are also presented here.

An update on the status of HSP90 inhibitors in cancer clinical trials

The evolutionary conserved molecular chaperone heat shock protein 90 (HSP90) plays an indispensable role in tumorigenesis by stabilizing client oncoproteins. Although the functionality of HSP90 is tightly regulated, cancer cells exhibit a unique dependence on this chaperone, leading to its overexpression, which has been associated with poor prognosis in certain malignancies. While various strategies targeting heat shock proteins (HSPs) involved in carcinogenesis have been explored, only inhibition of HSP90 has consistently and effectively resulted in proteasomal degradation of its client proteins. To date, a total of 22 HSP90 inhibitors (HSP90i) have been tested in 186 cancer clinical trials, as reported by clinicaltrials.gov. Among these trials, 60 % have been completed, 10 % are currently active, and 30 % have been suspended, terminated, or withdrawn. HSP90 inhibitors (HSP90i) have been used as single agents or in combination with other drugs for the treatment of various cancer types in clinical trials. Notably, improved clinical outcomes have been observed when HSP90i are used in combination therapies, as they exhibit a synergistic antitumor effect. However, as single agents, HSP90i have shown limited clinical activity due to drug-related toxicity or therapy resistance. Recently, active trials conducted in Japan evaluating TAS-116 (pimitespib) have demonstrated promising results with low toxicity as monotherapy and in combination with the immune checkpoint inhibitor nivolumab. Exploratory biomarker analyses performed in various trials have demonstrated target engagement that suggests the potential for identifying patient populations that may respond favorably to the therapy. In this review, we discuss the advances made in the past 5 years regarding HSP90i and their implications in anticancer therapeutics. Our focus lies in evaluating drug efficacy, prognosis forecast, pharmacodynamic biomarkers, and clinical outcomes reported in published trials. Through this comprehensive review, we aim to shed light on the progress and potential of HSP90i as promising therapeutic agents in cancer treatment.

Combination therapy involving HSP90 inhibitors for combating cancer: an overview of clinical and preclinical progress

The molecular chaperone heat shock protein 90 (HSP90) regulates multiple crucial signalling pathways in cancer by driving the maturation of key signalling components, thereby playing a crucial role in tumorigenesis and drug resistance in cancer. Inhibition of HSP90 results in metastable conformational collapse of its client proteins and their proteasomal degradation. Considerable efforts have been devoted to the development of small-molecule inhibitors targeting HSP90, and more than 20 inhibitors have been evaluated in clinical trials for cancer therapy. However, owing to disadvantages such as organ toxicity and drug resistance, only one HSP90 inhibitor has been approved for use in clinical settings. In recent years, HSP90 inhibitors used in combination with other anti-cancer therapies have shown remarkable potential in the treatment of cancer. HSP90 inhibitors work synergistically with various anti-cancer therapies, including chemotherapy, targeted therapy, radiation therapy and immunotherapy. HSP90 inhibitors can improve the pharmacological effects of the above-mentioned therapies and reduce treatment resistance. This review provides an overview of the use of combination therapy with HSP90 inhibitors and other anti-cancer therapies in clinical and preclinical studies reported in the past decade and summarises design strategies and prospects for these combination therapies. Altogether, this review provides a theoretical basis for further research and application of these combination therapies in the treatment of cancer.

Multiomic-Based Molecular Landscape of FaDu Xenograft Tumors in Mice after a Combinatorial Treatment with Radiation and an HSP90 Inhibitor Identifies Adaptation-Induced Targets of Resistance and Therapeutic Intervention

Treatments involving radiation and chemotherapy alone or in combination have improved patient survival and quality of life. However, cancers frequently evade these therapies due to adaptation and tumor evolution. Given the complexity of predicting response based solely on the initial genetic profile of a patient, a predetermined treatment course may miss critical adaptation that can cause resistance or induce new targets for drug and immunotherapy. To address the timescale for these evasive mechanisms, using a mouse xenograft tumor model, we investigated the rapidity of gene expression (mRNA), molecular pathway, and phosphoproteome changes after radiation, an HSP90 inhibitor, or combination. Animals received radiation, drug, or combination treatment for 1 or 2 weeks and were then euthanized along with a time-matched untreated group for comparison. Changes in gene expression occur as early as 1 week after treatment initiation. Apoptosis and cell death pathways were activated in irradiated tumor samples. For the HSP90 inhibitor and combination treatment at weeks 1 and 2 compared with Control Day 1, gene-expression changes induced inhibition of pathways including invasion of cells, vasculogenesis, and viral infection among others. The combination group included both drug-alone and radiation-alone changes. Our data demonstrate the rapidity of gene expression and functional pathway changes in the evolving tumor as it responds to treatment. Discovering these phenotypic adaptations may help elucidate the challenges in using sustained treatment regimens and could also define evolving targets for therapeutic efficacy.

HSP90: A promising target for NSCLC treatments

The emergence of targeted therapies and immunotherapies has improved the overall survival of patients with nonsmall cell lung cancer (NSCLC), but the 5-year survival rate remains low. New drugs are needed to overcome this dilemma. Moreover, the significant correlation between various client proteins of heat-shock protein (HSP) 90 and tumor occurrence, progression, and drug resistance suggests that HSP90 is a potential therapeutic target for NSCLC. However, the outcomes of clinical trials for HSP90 inhibitors have been disappointing, indicating significant toxicity of these drugs and that further screening of the beneficiary population is required. NSCLC patients with oncogenic-driven gene mutations or those at advanced stages who are resistant to multi-line treatments may benefit from HSP90 inhibitors. Enhancing the therapeutic efficacy and reducing the toxicity of HSP90 inhibitors can be achieved via the optimization of their drug structure, using them in combination therapies with low-dose HSP90 inhibitors and other drugs, and via targeted administration to tumor lesions. Here, we provide a review of the recent research on the role of HSP90 in NSCLC and summarize relevant studies of HSP90 inhibitors in NSCLC.

Drugs in the GIST Field (Therapeutic Targets and Clinical Trial Staging)

BACKGROUND

Molecular targeted therapies are the most important type of medical treatment for GIST, but the development of GIST drugs and their targets have not been summarized.

METHODS

Drugs in the field of GIST were analyzed and collated through Pharmaprojects, ClinicalTrials. gov and PharmaGO databases.

RESULTS

As of 2021, there are 75 drugs that have appeared in the GIST clinical trials. The six most frequent targets in GIST clinical trials, in descending order of frequency, were KIT, PDGFRA, KDR (VEGFR2), FLT3, FLT1 (VEGFR1), and FLT4/VEGFR3. Only 8 drugs are in preclinical research. There are challenges in the development of new drugs for GIST.

CONCLUSION

This article analyzes and summarizes the general situation of GIST drugs, the target distribution of GIST drugs, and the trends in GIST drug-related clinical trials.

Combination therapy of tyrosine kinase inhibitor sorafenib with the HSP90 inhibitor onalespib as a novel treatment regimen for thyroid cancer

Thyroid cancer is the most common endocrine malignancy, affecting nearly 600,000 new patients worldwide. Treatment with the BRAF inhibitor sorafenib partially prolongs progression-free survival in thyroid cancer patients, but fails to improve overall survival. This study examines enhancing sorafenib efficacy by combination therapy with the novel HSP90 inhibitor onalespib. In vitro efficacy of sorafenib and onalespib monotherapy as well as in combination was assessed in papillary (PTC) and anaplastic (ATC) thyroid cancer cells using cell viability and colony formation assays. Migration potential was studied in wound healing assays. The in vivo efficacy of sorafenib and onalespib therapy was evaluated in mice bearing BHT-101 xenografts. Sorafenib in combination with onalespib significantly inhibited PTC and ATC cell proliferation, decreased metabolic activity and cancer cell migration. In addition, the drug combination approach significantly inhibited tumor growth in the xenograft model and prolonged the median survival. Our results suggest that combination therapy with sorafenib and onalespib could be used as a new therapeutic approach in the treatment of thyroid cancer, significantly improving the results obtained with sorafenib as monotherapy. This approach has the potential to reduce treatment adaptation while at the same time providing therapeutic anti-cancer benefits such as reducing tumor growth and metastatic potential.

HSP90 expression is associated with outcome in pulmonary carcinoid tumor patients

Background

Pulmonary carcinoids (PCs) are rare tumors that account for <2% of all lung cancer cases. Patients who undergo resection for PC tumors generally have a favorable prognosis, but there is a risk for late recurrence and distant metastasis. The objective of this study was to identify biomarkers for PC tumors using RNA sequencing and immunohistochemistry.

Methods

A total of 128 formalin-fixed, paraffin-embedded PC tumor samples from patients surgically treated at Helsinki University Hospital between 1990 and 2013 were analyzed in the study. RNA sequencing was first used to detect genes with higher expression in specific histological subtypes and metastatic and nonmetastatic tumors than in adjacent lung tissue. The diagnostic potential of the biomarkers was assessed using immunohistochemistry.

Results

Through gene expression analysis, HSP90AB1 expression was found to be significantly elevated in metastatic PC tumors (P<0.0001). The paralog of the gene, HSP90AA1, was also overexpressed, but the finding was not statistically significant. Through immunohistochemical analysis, HSP90 protein expression was found to be associated with shorter disease-specific survival (DSS) (P=0.009) and increased risk of disease-specific death [hazard ratio (HR) 6.4, 95% confidence interval (CI): 1.3-31.8].

Conclusions

This study confirms that HSP90 has a prognostic role in PC tumors and that inhibition of HSP90 may possess therapeutic potential in the management of PC tumor patients in the future.

Enhanced Therapeutic Effects of 177Lu-DOTA-M5A in Combination with Heat Shock Protein 90 Inhibitor Onalespib in Colorectal Cancer Xenografts

Carcinoembryonic antigen (CEA) has emerged as an attractive target for theranostic applications in colorectal cancers (CRCs). In the present study, the humanized anti-CEA antibody hT84.66-M5A (M5A) was labeled with 177Lu for potential CRC therapy. Moreover, the novel combination of 177Lu-DOTA-M5A with the heat shock protein 90 inhibitor onalespib, suggested to mediate radiosensitizing properties, was assessed in vivo for the first time. M5A antibody uptake and therapeutic effects, alone or in combination with onalespib, were assessed in human CRC xenografts and visualized using SPECT/CT imaging. Although both 177Lu-DOTA-M5A and onalespib monotherapies effectively reduced tumor growth rates, the combination therapy demonstrated the most substantial impact, achieving a fourfold reduction in tumor growth compared to the control group. Median survival increased by 33% compared to 177Lu-DOTA-M5A alone, and tripled compared to control and onalespib groups. Importantly, combination therapy yielded comparable or superior effects to the double dose of 177Lu-DOTA-M5A monotherapy. 177Lu-DOTA-M5A increased apoptotic cell levels, indicating its potential to induce tumor cell death. These findings show promise for 177Lu-DOTA-M5A as a CRC therapeutic agent, and its combination with onalespib could significantly enhance treatment efficacy. Further in vivo studies are warranted to validate these findings fully and explore the treatment's potential for clinical use.

Newly Developed Targeted Therapies Against the Androgen Receptor in Triple-Negative Breast Cancer: A Review

Among different types of breast cancers (BC), triple-negative BC (TNBC) amounts to 15% to 20% of breast malignancies. Three principal characteristics of TNBC cells are (i) extreme aggressiveness, (ii) absence of hormones, and (iii) growth factor receptors. Due to the lack or poor expression of the estrogen receptor, human epidermal growth factor receptor 2, and progesterone receptor, TNBC is resistant to hormones and endocrine therapies. Consequently, chemotherapy is currently used as the primary approach against TNBC. Expression of androgen receptor (AR) in carcinoma cells has been observed in a subset of patients with TNBC; therefore, inhibiting androgen signaling pathways holds promise for TNBC targeting. The new AR inhibitors have opened up new therapy possibilities for BC patients carrying AR-positive TNBC cells. Our group provides a comprehensive review of the structure and function of the AR and clinical evidence for targeting the cell's nuclear receptor in TNBC. We updated AR agonists, inhibitors, and antagonists. We also presented a new era of genetic manipulating CRISPR/Cas9 and nanotechnology as state-of-the-art approaches against AR to promote the efficiency of targeted therapy in TNBC. SIGNIFICANCE STATEMENT: The lack of effective treatment for triple-negative breast cancer is a health challenge. The main disadvantages of existing treatments are their side effects, due to their nonspecific targeting. Molecular targeting of cellular receptors, such as androgen receptors, increased expression in malignant tissues, significantly improving the survival rate of breast cancer patients.

Natural Baicalein-Rich Fraction as Radiosensitizer in Combination with Bismuth Oxide Nanoparticles and Cisplatin for Clinical Radiotherapy

Purpose

Methods

Results

Conclusion

Advances in the study of HSP70 inhibitors to enhance the sensitivity of tumor cells to radiotherapy

The 70 kDa heat shock protein (HSP70) is one of the most conserved proteins and a ubiquitous molecular chaperone that plays a role in the folding, remodeling, and degradation of various proteins to maintain proteostasis. It has been shown that HSP70 is abundantly expressed in cancer and enhances tumor resistance to radiotherapy by inhibiting multiple apoptotic pathways, such as interfering with the cellular senescence program, promoting angiogenesis, and supporting metastasis. Thus, HSP70 provides an effective target for enhancing the effects of radiation therapy in the clinical management of cancer patients. Inhibition of HSP70 enhances the radiation-induced tumor-killing effect and thus improves the efficacy of radiotherapy. This article reviews the sensitivity of Hsp70 and its related inhibitors to radiotherapy of tumor cells.

In Vitro Characterization of 177Lu-DOTA-M5A Anti-Carcinoembryonic Antigen Humanized Antibody and HSP90 Inhibition for Potentiated Radioimmunotherapy of Colorectal Cancer

Carcinoembryonic antigen (CEA) is an antigen that is highly expressed in colorectal cancers and widely used as a tumor marker. ¹³¹I and ⁹⁰Y-radiolabeled anti-CEA monoclonal antibodies (mAbs) have previously been assessed for radioimmunotherapy in early clinical trials with promising results. Moreover, the heat shock protein 90 inhibitor onalespib has previously demonstrated radiotherapy potentiation effects in vivo. In the present study, a ¹⁷⁷Lu-radiolabeled anti-CEA hT84.66-M5A mAb (M5A) conjugate was developed and the potential therapeutic effects of ¹⁷⁷Lu-DOTA-M5A and/or onalespib were investigated. The ¹⁷⁷Lu radiolabeling of M5A was first optimized and characterized. Binding specificity and affinity of the conjugate were then evaluated in a panel of gastrointestinal cancer cell lines. The effects on spheroid growth and cell viability, as well as molecular effects from treatments, were then assessed in several three-dimensional (3D) multicellular colorectal cancer spheroid models. Stable and reproducible radiolabeling was obtained, with labeling yields above 92%, and stability was retained at least 48 h post-radiolabeling. Antigen-specific binding of the radiolabeled conjugate was demonstrated on all CEA-positive cell lines. Dose-dependent therapeutic effects of both ¹⁷⁷Lu-DOTA-M5A and onalespib were demonstrated in the spheroid models. Moreover, effects were potentiated in several dose combinations, where spheroid sizes and viabilities were significantly decreased compared to the corresponding monotherapies. For example, the combination treatment with 350 nM onalespib and 20 kBq ¹⁷⁷Lu-DOTA-M5A resulted in 2.5 and 2.3 times smaller spheroids at the experimental endpoint than the corresponding monotreatments in the SNU1544 spheroid model. Synergistic effects were demonstrated in several of the more effective combinations. Molecular assessments validated the therapy results and displayed increased apoptosis in several combination treatments. In conclusion, the combination therapy of anti-CEA ¹⁷⁷Lu-DOTA-M5A and onalespib showed enhanced therapeutic effects over the individual monotherapies for the potential treatment of colorectal cancer. Further in vitro and in vivo studies are warranted to confirm the current study findings.

Novel regulators of airway epithelial barrier function during inflammation: potential targets for drug repurposing

INTRODUCTION

Endogenous inflammatory signaling molecules resulting from deregulated immune responses, can impair airway epithelial barrier function and predispose individuals with airway inflammatory diseases to exacerbations and lung infections. Targeting the specific endogenous factors disrupting the airway barrier therefore has the potential to prevent disease exacerbations without affecting the protective immune responses.

AREAS COVERED

Here, we review the endogenous factors and specific mechanisms disrupting airway epithelial barrier during inflammation and reflect on whether these factors can be specifically targeted by repurposed existing drugs. Literature search was conducted using PubMed, drug database of US FDA and European Medicines Agency until and including September 2021.

EXPERT OPINION

IL-4 and IL-13 signaling are the major pathways disrupting the airway epithelial barrier during airway inflammation. However, blocking IL-4/IL-13 signaling may adversely affect protective immune responses and increase susceptibility of host to infections. An alternate approach to modulate airway epithelial barrier function involves targeting specific downstream component of IL-4/IL-13 signaling or different inflammatory mediators responsible for regulation of airway epithelial barrier. Airway epithelium-targeted therapy using inhibitors of HDAC, HSP90, MIF, mTOR, IL-17A and VEGF may be a potential strategy to prevent airway epithelial barrier dysfunction in airway inflammatory diseases.

A heat shock protein 90 inhibitor reduces oncoprotein expression and induces cell death in heterogeneous glioblastoma cells with EGFR, PDGFRA, CDK4, and NF1 aberrations

AIMS

Glioblastoma (GBM) is a highly malignant brain tumor. After treatment with the first-line drug temozolomide, only 50% of patients are responsive. Recent literature shows that the difficulty in treating GBM is mainly due to the heterogeneity of its four major cellular states, which are characterized by differences in EGFR, PDGFRA, CDK4, and NF1. Therefore, development of a multitarget drug is a potential strategy for treating heterogeneous GBM.

MAIN METHODS

In this study, the antitumor ability of a potent heat shock protein 90 inhibitor, NVP-AUY922 (AUY922), was evaluated in GBM cell lines (U-87 MG and T98G cells) and patient-derived GBM cell lines [P#5 and P#5 temozolomide-resistant (TMZ-R) cells].

KEY FINDINGS

We found that AUY922 significantly reduced cell viability and colony formation in four GBM cell lines. AUY922 also significantly induced apoptosis by increasing PARP1 cleavage and the number of annexin V-positive cells. The autophagy indicators as MAP1LC3B cleavage and MAP1LC3B puncta were increased after AUY922 treatment. AUY922-induced cell death could be partially reversed by pharmacological inhibition of either apoptotic inhibitor or autophagy inhibitor. Moreover, AUY922 reduced the mRNA and protein expressions of EGFR, PDGFRA, CDK4, and NF1, which contribute to the four cellular state subtypes in GBM cells. In addition, the downstream signaling proteins of these four proteins, AKT/p-AKT, MAPK/p-MAPK, and BRAF, were downregulated after AUY922 treatment.

SIGNIFICANCE

Taken together, AUY922 led to GBM cell death via apoptosis and autophagy, and reduced the mRNA and protein expression of EGFR, PDGFRA, CDK4, and NF1in heterogeneous GBM cells.

Inhibitors of the Plasmodium falciparum Hsp90 towards Selective Antimalarial Drug Design: The Past, Present and Future

Malaria is still one of the major killer parasitic diseases in tropical settings, posing a public health threat. The development of antimalarial drug resistance is reversing the gains made in attempts to control the disease. The parasite leads a complex life cycle that has adapted to outwit almost all known antimalarial drugs to date, including the first line of treatment, artesunate. There is a high unmet need to develop new strategies and identify novel therapeutics to reverse antimalarial drug resistance development. Among the strategies, here we focus and discuss the merits of the development of antimalarials targeting the Heat shock protein 90 (Hsp90) due to the central role it plays in protein quality control.

Rapamycin and trametinib: a rational combination for treatment of NSCLC

Mammalian target of rapamycin (mTOR) is one of the most commonly activated pathways in human cancers, including lung cancer. Targeting mTOR with molecule inhibitors is considered as a useful therapeutic strategy. However, the results obtained from the clinical trials with the inhibitors so far have not met the original expectations, largely because of the drug resistance. Thus, combined or multiple drug therapy can bring about more favorable clinical outcomes. Here, we found that activation of ERK pathway was responsible for rapamycin drug resistance in non-small-cell lung cancer (NSCLC) cells. Accordingly, rapamycin-resistant NSCLC cells were more sensitive to ERK inhibitor (ERKi), trametinib, and in turn, trametinib-resistant NSCLC cells were also susceptible to rapamycin. Combining rapamycin with trametinib led to a potent synergistic antitumor efficacy, which induced G1-phase cycle arrest and apoptosis. In addition, rapamycin synergized with another ERKi, MEK162, and in turn, trametinib synergized with other mTORi, Torin1 and OSI-027. Mechanistically, rapamycin in combination with trametinib resulted in a greater decrease of phosphorylation of AKT, ERK, mTOR and 4EBP1. In xenograft mouse model, co-administration of rapamycin and trametinib caused a substantial suppression in tumor growth without obvious drug toxicity. Overall, our study identifies a reasonable combined strategy for treatment of NSCLC.

Inhibition of the Human Hsc70 System by Small Ligands as a Potential Anticancer Approach

Simple Summary

High levels of Heat shock proteins (Hsps) in specific cancers are usually linked to a poor prognosis, tumor progression, invasiveness, and resistance to treatment. Chaperone inhibition could therefore be toxic for cancer cells due to their high dependence on chaperone activity to survive. This study shows the potential to repurpose the small chemical compound pinaverium bromide, currently used to treat functional gastrointestinal disorders, as a possible antitumor drug since it displays a marked toxicity against two melanoma cell lines without affecting the viability of fibroblast and primary melanocytes. This compound interacts with structural regions shared by representatives of the Hsp70 and Hsp110 families, inhibiting the substrate remodeling ability of the Hsp70 system in vitro and in a cellular context.

Abstract

Heat shock protein (Hsp) synthesis is upregulated in a wide range of cancers to provide the appropriate environment for tumor progression. The Hsp110 and Hsp70 families have been associated to cancer cell survival and resistance to chemotherapy. In this study, we explore the strategy of drug repurposing to find new Hsp70 and Hsp110 inhibitors that display toxicity against melanoma cancer cells. We found that the hits discovered using Apg2, a human representative of the Hsp110 family, as the initial target bind also to structural regions present in members of the Hsp70 family, and therefore inhibit the remodeling activity of the Hsp70 system. One of these compounds, the spasmolytic agent pinaverium bromide used for functional gastrointestinal disorders, inhibits the intracellular chaperone activity of the Hsp70 system and elicits its cytotoxic activity specifically in two melanoma cell lines by activating apoptosis. Docking and molecular dynamics simulations indicate that this compound interacts with regions located in the nucleotide-binding domain and the linker of the chaperones, modulating their ATPase activity. Thus, repurposing of pinaverium bromide for cancer treatment appears as a promising novel therapeutic approach.

Quality control of mislocalized and orphan proteins

A healthy and functional proteome is essential to cell physiology. However, this is constantly being challenged as most steps of protein metabolism are error-prone and changes in the physico-chemical environment can affect protein structure and function, thereby disrupting proteome homeostasis. Among a variety of potential mistakes, proteins can be targeted to incorrect compartments or subunits of protein complexes may fail to assemble properly with their partners, resulting in the formation of mislocalized and orphan proteins, respectively. Quality control systems are in place to handle these aberrant proteins, and to minimize their detrimental impact on cellular functions. Here, we discuss recent findings on quality control mechanisms handling mislocalized and orphan proteins. We highlight common principles involved in their recognition and summarize how accumulation of these aberrant molecules is associated with aging and disease.

Pharmacological Inhibition of HSP90 Radiosensitizes Head and Neck Squamous Cell Carcinoma Xenograft by Inhibition of DNA Damage Repair, Nucleotide Metabolism, and Radiation-Induced Tumor Vasculogenesis

PURPOSE

Recent preclinical studies suggest combining the HSP90 inhibitor AT13387 (Onalespib) with radiation (IR) against colon cancer and head and neck squamous cell carcinoma (HNSCC). These studies emphasized that AT13387 downregulates HSP90 client proteins involved in oncogenic signaling and DNA repair mechanisms as major drivers of enhanced radiosensitivity. Given the large array of client proteins HSP90 directs, we hypothesized that other key proteins or signaling pathways may be inhibited by AT13387 and contribute to enhanced radiosensitivity. Metabolomic analysis of HSP90 inhibition by AT13387 was conducted to identify metabolic biomarkers of radiosensitization and whether modulations of key proteins were involved in IR-induced tumor vasculogenesis, a process involved in tumor recurrence.

METHODS AND MATERIALS

HNSCC and non-small cell lung cancer cell lines were used to evaluate the AT13387 radiosensitization effect in vitro and in vivo. Flow cytometry, immunofluorescence, and immunoblot analysis were used to evaluate cell cycle changes and HSP90 client protein's role in DNA damage repair. Metabolic analysis was performed using liquid chromatography-Mass spectrometry. Immunohistochemical examination of resected tumors post-AT13387 and IR treatment were conducted to identify biomarkers of IR-induced tumor vasculogenesis.

RESULTS

In agreement with recent studies, AT13387 treatment combined with IR resulted in a G2/M cell cycle arrest and inhibited DNA repair. Metabolomic profiling indicated a decrease in key metabolites in glycolysis and tricarboxylic acid cycle by AT13387, a reduction in Adenosine 5'-triphosphate levels, and rate-limiting metabolites in nucleotide metabolism, namely phosphoribosyl diphosphate and aspartate. HNSCC xenografts treated with the combination exhibited increased tumor regrowth delay, decreased tumor infiltration of CD45 and CD11b+ bone marrow-derived cells, and inhibition of HIF-1 and SDF-1 expression, thereby inhibiting IR-induced vasculogenesis.

CONCLUSIONS

AT13387 treatment resulted in pharmacologic inhibition of cancer cell metabolism that was linked to DNA damage repair. AT13387 combined with IR inhibited IR-induced vasculogenesis, a process involved in tumor recurrence postradiotherapy. Combining AT13387 with IR warrants consideration of clinical trial assessment.

Overcoming Limitations of Cisplatin Therapy by Additional Treatment With the HSP90 Inhibitor Onalespib

Rational

Cisplatin based cancer therapy is an affordable and effective standard therapy for several solid cancers, including lung, ovarian and head and neck cancers. However, the clinical use of cisplatin is routinely limited by the development of drug resistance and subsequent therapeutic failure. Therefore, methods of circumventing cisplatin resistance have the potential to increase therapeutic efficiency and dramatically increase overall survival. Cisplatin resistance can be mediated by alterations to the DNA damage response, where multiple components of the repair machinery have been described to be client proteins of HSP90. In the present study, we have investigated whether therapy with the novel HSP90 inhibitor onalespib can potentiate the efficacy of cisplatin and potentially reverse cisplatin resistance in ovarian and head and neck cancer cells.

Methods

Cell viability, cancer cell proliferation and migration capacity were evaluated in vitro on models of ovarian and head and neck cancer cells. Western blotting was used to assess the downregulation of HSP90 client proteins and alterations in downstream signaling proteins after exposure to cisplatin and/or onalespib. Induction of apoptosis and DNA damage response were evaluated in both monotherapy and combination therapy groups.

Results

Results demonstrate that onalespib enhances the efficiency of cisplatin in a dose-dependent manner. Tumor cells treated with both drugs displayed lower viability and a decreased migration rate compared to vehicle-control cells and cells treated with individual compounds. An increase of DNA double strand breaks was observed in both cisplatin and onalespib treated cells. The damage was highest and most persistent in the combination group, delaying the DNA repair machinery. Further, the cisplatin and onalespib co-treated cells had greater apoptotic activity compared to controls.

Conclusion

The results of this study demonstrate that the reduced therapeutic efficacy of cisplatin due to drug-resistance could be overcome by combination treatment with onalespib. We speculate that the increased apoptotic signaling, DNA damage as well as the downregulation of HSP90 client proteins are important mechanisms promoting increased sensitivity to cisplatin treatment.

Priming of Anti-tumor Immune Mechanisms by Radiotherapy Is Augmented by Inhibition of Heat Shock Protein 90

Radiotherapy is an essential part of multi-modal cancer therapy. Nevertheless, for certain cancer entities such as colorectal cancer (CRC) the indications of radiotherapy are limited due to anatomical peculiarities and high radiosensitivity of the surrounding normal tissue. The development of molecularly targeted, combined modality approaches may help to overcome these limitations. Preferably, such strategies should not only enhance radiation-induced tumor cell killing and the abrogation of tumor cell clonogenicity, but should also support the stimulation of anti-tumor immune mechanisms – a phenomenon which moved into the center of interest of preclinical and clinical research in radiation oncology within the last decade. The present study focuses on inhibition of heat shock protein 90 (HSP90) whose combination with radiotherapy has previously been reported to exhibit convincing therapeutic synergism in different preclinical cancer models. By employing in vitro and in vivo analyses, we examined if this therapeutic synergism also applies to the priming of anti-tumor immune mechanisms in model systems of CRC. Our results indicate that the combination of HSP90 inhibitor treatment and ionizing irradiation induced apoptosis in colorectal cancer cells with accelerated transit into secondary necrosis in a hyperactive Kras-dependent manner. During secondary necrosis, dying cancer cells released different classes of damage-associated molecular patterns (DAMPs) that stimulated migration and recruitment of monocytic cells in vitro and in vivo. Additionally, these dying cancer cell-derived DAMPs enforced the differentiation of a monocyte-derived antigen presenting cell (APC) phenotype which potently triggered the priming of allogeneic T cell responses in vitro. In summary, HSP90 inhibition – apart from its radiosensitizing potential – obviously enables and supports the initial steps of anti-tumor immune priming upon radiotherapy and thus represents a promising partner for combined modality approaches. The therapeutic performance of such strategies requires further in-depth analyses, especially for but not only limited to CRC.

Molecular Alterations in Vaginal Melanomas: Report of 4 Cases and Literature Review

ABSTRACT

Melanomas of the female gynecological tract comprise approximately 18% of mucosal melanomas, a rare subtype of melanoma. Within the female genital tract, 70% of primary melanomas of the gynecological tract are from the vulva with the remainder occurring in the vagina and rarely, in the cervix. We investigate molecular alterations by next-generation sequencing-based molecular tests targeting 99 cancer genes and translocation/fusion assays in 4 and 3 vaginal melanomas, respectively. The ages of the 4 patients range from 65 to 90 years. Postmenopausal bleeding was the most common presenting symptom. Tumor size ranged from 0.5 to 6.6 cm. KIT L576P mutation was documented in case 1, whereas TP53 mutation was seen in cases 2 and 3 (L130F and Y163C). Case 2 also harbored NF2 E204Q and ATRX D1719H mutations. A number of gene copy alterations were noted in case 4, which included GNA11 loss, MYC gain, RET loss, SMO loss, SUFU loss, and TSC2 loss. No gene fusion was detected in any of the 3 tested cases. In conclusion, in addition to KIT, TP53, and ATRX mutations, which have been previously reported, our cases harbor NF2 mutation and multiple gene copy alterations that have not previously been documented in vaginal melanomas. These findings highlight the potential role of targeted therapy in this rare melanoma subtype.