Acquired resistance to 17-allylamino-17-demethoxygeldanamycin (17-AAG, tanespimycin) in glioblastoma cells

Pan-cancer analysis of SERPINE family genes as biomarkers of cancer prognosis and response to therapy

Background: Serine protease inhibitor E (SERPINE) family genes participate in the tumor growth, cancer cell survival and metastasis. However, the SERPINE family members role in the prognosis and their clinical therapeutic potentials in various human cancer types have not been elaborately explored. Methods: We preliminarily analyzed expression levels and prognostic values of SERPINE family genes, and investigated the correlation between SERPINEs expression and tumor microenvironment (TME), Stemness score, clinical characteristic, immune infiltration, tumor mutational burden (TMB), immune subtype, and drug sensitivity in pan-cancer, which based on updated public databases and integrated some bioinformatics analysis methods. In addition, we conducted the enrichment analysis of SERPINEs from DAVID and KOBAS databases. Results: SERPINE1, SERPINE2, and SERPINE3 expression were upregulated in nine cancers, twelve cancers, and six cancers, respectively. The expression of SERPINE family genes was associated with the prognosis in several cancers from The Cancer Genome Atlas (TCGA). Furthermore, SERPINE family genes expression also had a significant relation to stromal and immune scores, and RNA stemness score and DNA stemness score in pan-cancer. SERPINE1 and SERPINE2 expression significantly increased in tumor advanced stage in colon adenocarcinoma (COAD). Results showed that SERPINE1 and SERPINE2 expression were negatively related with B cells and Monocytes, respectively. SERPINE2 expression had a significantly positive relation with B cells and Macrophages. In terms of TMB, SERPINE1, SERPINE2, and SERPINE3 were found to associated with TMB in seven cancers, fourteen cancers, and four cancers, respectively. Moreover, all SERPINE gene family members were significantly correlated with immune subtypes. SERPINE1 expression had a significantly positive or negative correlation with drug sensitivity. Conclusion: The study indicated the great potential of SERPINE family genes as biomarkers for prognosis and provided valuable strategies for further investigation of SERPINE family genes as potential targets in cancer.

Impact of NQO1 dysregulation in CNS disorders

NAD(P)H Quinone Dehydrogenase 1 (NQO1) plays a pivotal role in the regulation of neuronal function and synaptic plasticity, cellular adaptation to oxidative stress, neuroinflammatory and degenerative processes, and tumorigenesis in the central nervous system (CNS). Impairment of the NQO1 activity in the CNS can result in abnormal neurotransmitter release and clearance, increased oxidative stress, and aggravated cellular injury/death. Furthermore, it can cause disturbances in neural circuit function and synaptic neurotransmission. The abnormalities of NQO1 enzyme activity have been linked to the pathophysiological mechanisms of multiple neurological disorders, including Parkinson's disease, Alzheimer's disease, epilepsy, multiple sclerosis, cerebrovascular disease, traumatic brain injury, and brain malignancy. NQO1 contributes to various dimensions of tumorigenesis and treatment response in various brain tumors. The precise mechanisms through which abnormalities in NQO1 function contribute to these neurological disorders continue to be a subject of ongoing research. Building upon the existing knowledge, the present study reviews current investigations describing the role of NQO1 dysregulations in various neurological disorders. This study emphasizes the potential of NQO1 as a biomarker in diagnostic and prognostic approaches, as well as its suitability as a target for drug development strategies in neurological disorders.

Macrophage migration inhibitory factor as a therapeutic target in neuro-oncology: A review

Primary central nervous system (CNS) tumors affect tens of thousands of patients each year, and there is a significant need for new treatments. Macrophage migration inhibitory factor (MIF) is a cytokine implicated in multiple tumorigenic processes such as cell proliferation, vascularization, and immune evasion and is therefore a promising therapeutic target in primary CNS tumors. There are several MIF-directed treatments available, including small-molecule inhibitors, peptide drugs, and monoclonal antibodies. However, only a small number of these drugs have been tested in preclinical models of primary CNS tumors, and even fewer have been studied in patients. Moreover, the brain has unique therapeutic requirements that further make effective targeting challenging. In this review, we summarize the latest functions of MIF in primary CNS tumor initiation and progression. We also discuss advances in MIF therapeutic development and ongoing preclinical studies and clinical trials. Finally, we discuss potential future MIF therapies and the strategies required for successful clinical translation.

GTP Cyclohydrolase Drives Breast Cancer Development and Promotes EMT in an Enzyme-Independent Manner

GTP cyclohydrolase (GCH1) is the rate-limiting enzyme for tetrahydrobiopterin (BH4) biosynthesis. The catalysis of BH4 biosynthesis is tightly regulated for physiological neurotransmission, inflammation, and vascular tone. Paradoxically, BH4 has emerged as an oncometabolite regulating tumor growth, but the effects on tumor development remain controversial. Here, we found that GCH1 potentiated the growth of triple-negative breast cancer (TNBC) and HER2+ breast cancer and transformed nontumor breast epithelial cells. Independent of BH4 production, GCH1 protein induced epithelial-to-mesenchymal transition by binding to vimentin (Vim), which was mediated by HSP90. Conversely, GCH1 ablation impaired tumor growth, suppressed Vim in TNBC, and inhibited EGFR/ERK signaling while activating the p53 pathway in estrogen receptor-positive tumor cells. GCH1 deficiency increases tumor cell sensitivity to HSP90 inhibition and endocrine treatments. In addition, high GCH1 correlated with poor breast cancer survival. Together, this study reveals an enzyme-independent oncogenic role of GCH1, presenting it as a potential target for therapeutic development.

SIGNIFICANCE

GTP cyclohydrolase functions as an oncogene in breast cancer and binds vimentin to induce epithelial-to-mesenchymal transition independently of its enzyme activity, which confers targetable vulnerabilities for developing breast cancer treatment strategies.

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

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

Novel Drugs with High Efficacy against Tumor Angiogenesis

Angiogenesis is involved in physiological and pathological processes in the body. Tumor angiogenesis is a key factor associated with tumor growth, progression, and metastasis. Therefore, there is great interest in developing antiangiogenic strategies. Hypoxia is the basic initiating factor of tumor angiogenesis, which leads to the increase of vascular endothelial growth factor (VEGF), angiopoietin (Ang), hypoxia-inducible factor (HIF-1), etc. in hypoxic cells. The pathways of VEGF and Ang are considered to be critical steps in tumor angiogenesis. A number of antiangiogenic drugs targeting VEGF/VEGFR (VEGF receptor) or ANG/Tie2, or both, are currently being used for cancer treatment, or are still in various stages of clinical development or preclinical evaluation. This article aims to review the mechanisms of angiogenesis and tumor angiogenesis and to focus on new drugs and strategies for the treatment of antiangiogenesis. However, antitumor angiogenic drugs alone may not be sufficient to eradicate tumors. The molecular chaperone heat shock protein 90 (HSP90) is considered a promising molecular target. The VEGFR system and its downstream signaling molecules depend on the function of HSP90. This article also briefly introduces the role of HSP90 in angiogenesis and some HSP90 inhibitors.

Positive regulation of ataxia-telangiectasia-mutated protein (ATM) by E2F transcription Factor 1 (E2F-1) in cisplatin-resistant nasopharyngeal carcinoma cells

Objective

To explore the mechanism of E2F transcription Factor 1 (E2F-1)-mediated ataxia-telangiectasia-mutated protein (ATM) in cisplatin (DDP)-resistant nasopharyngeal carcinoma (NPC).

Methods

E2F-1 and ATM expression was assessed in DDP-resistant NPC cell lines (CNE2/DDP and HNE1/DDP) and parental cells. Then, DDP-resistant NPC cells were transfected with control shRNA (short hairpin RNA) or E2F-1 shRNAs with or without ATM lentiviral activation particles. The half maximal inhibitory concentration (IC50) was evaluated by 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay, and the cell cycle and cell proliferation were measured by flow cytometry and EdU staining, respectively. In addition, the expression of genes and proteins was quantified by quantitative reverse-transcription polymerase chain reaction (qRT–PCR) and western blotting, respectively.

Results

Both E2F-1 and ATM expression in DDP-resistant NPC cells was much higher than that in parental cells. E2F-1 shRNA reduced ATM expression in DDP-resistant NPC cells, but ATM overexpression had no significant effect on E2F-1. ATM overexpression enhanced DDP resistance in DDP-resistant NPC cells with increased IC50 values, which was reversed by E2F-1 inhibition. Meanwhile, ATM overexpression resulted in upregulation of ABCA2 and ABCA5 in DDP-resistant NPC cells, induced elevations in the transition of the cells into S-phase, and increased cell proliferation with enhanced expression of cyclin E1, CDK2, and Ki67, which was reversed by E2F-1 shRNAs.

Conclusion

Downregulation of E2F-1, possibly by regulating ATM, could block the cell cycle in the G1 phase and reduce the proliferation of CNE2/DDP cells, thereby reversing the resistance of human NPC cells to DDP.

Preferential radiosensitization to glioblastoma cancer stem cell‑like cells by a Hsp90 inhibitor, N‑vinylpyrrolidone‑AUY922

The present study examined the radiosensitization induced by a heat shock protein 90 inhibitor, N-vinylpyrrolidone (NVP)-AUY922, in CD133-positive cells in a hypoxic area of T98G spheroids. CD133-positive cells that are induced in the hypoxic microenvironment of spheroids have previously been reported to exhibit cancer stem cell-like properties. The present study used CD133-positive cells from a glioblastoma cell line (T98G) as cancer stem cell-like cells. CD133-positive and negative cells were sorted from T98G spheroids using fluorescence-activated cell sorting and used for colony formation assay. Colony formation assay results indicated that NVP-AUY922 enhanced radiosensitivity more strongly in CD133-positive cells compared with CD133-negative cells. This result showed that NVP-AUY922 was a preferential radiosensitization candidate targeting glioblastoma cancer stem cells. The mechanisms underlying radiosensitization by NVP-AUY922 are discussed in relation to the properties of cancer stem cells. Overall, HIF-1α inhibition by NVP-AUY922 may induce higher sensitization of cancer stem cells to radiation.

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.

Robust metabolic transcriptional components in 34,494 patient-derived cancer-related samples and cell lines

Background

Patient-derived bulk expression profiles of cancers can provide insight into the transcriptional changes that underlie reprogrammed metabolism in cancer. These profiles represent the average expression pattern of all heterogeneous tumor and non-tumor cells present in biopsies of tumor lesions. Hence, subtle transcriptional footprints of metabolic processes can be concealed by other biological processes and experimental artifacts. However, consensus independent component analyses (c-ICA) can capture statistically independent transcriptional footprints of both subtle and more pronounced metabolic processes.

Methods

We performed c-ICA with 34,494 bulk expression profiles of patient-derived tumor biopsies, non-cancer tissues, and cell lines. Gene set enrichment analysis with 608 gene sets that describe metabolic processes was performed to identify the transcriptional components enriched for metabolic processes (mTCs). The activity of these mTCs was determined in all samples to create a metabolic transcriptional landscape.

Results

A set of 555 mTCs was identified of which many were robust across different datasets, platforms, and patient-derived tissues and cell lines. We demonstrate how the metabolic transcriptional landscape defined by the activity of these mTCs in samples can be used to explore the associations between the metabolic transcriptome and drug sensitivities, patient outcomes, and the composition of the immune tumor microenvironment.

Conclusions

To facilitate the use of our transcriptional metabolic landscape, we have provided access to all data via a web portal (www.themetaboliclandscapeofcancer.com). We believe this resource will contribute to the formulation of new hypotheses on how to metabolically engage the tumor or its (immune) microenvironment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40170-021-00272-7.

TMEM45A Affects Proliferation, Apoptosis, Epithelial-Mesenchymal Transition, Migration, Invasion and Cisplatin Resistance of HPV-Positive Cervical Cancer Cell Lines

To investigate the effects of transmembrane protein 45A (TMEM45A) on biological characteristics and cisplatin (DDP) resistance of cervical cancer cells. TMEM45A in cervical cancer cells and normal cervical epithelial cells (HCerEpiC) were quantified by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting. HPV genotypes were identified by multiplex PCR. SiHa and HeLa cells were divided into Blank, shCTL, shTMEM45A-1, and shTMEM45A-2 groups, followed by Cell Counting Kit-8 (CCK-8), EdU, Annexin V-FITC/PI staining, Wound healing, and Transwell invasion assays, as well as qRT-PCR and Western blotting. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide) was employed to evaluate the impact of TMEM45A shRNA on cisplatin-resistant cervical cancer cells (SiHa/DDP and HeLa/DDP). Compared with HcerEpic cell, cervical cancer cells exhibited the upregulation of TMEM45A expression, especially in HPV-positive cell lines (CaSki, SiHa, HeLa). TMEM45A shRNA suppressed the proliferation of SiHa and HeLa cells, arrested cells at the S phase, and promoted cell apoptosis. TMEM45A shRNA inhibited the epithelial-mesenchymal transition (EMT), invasion, migration of SiHa and HeLa cells, accompanying by the downregulated Vimentin and N-cadherin with the upregulated E-cadherin. Moreover, SiHa/DDP and HeLa/DDP had higher TMEM45A expression than their parental SiHa and HeLa cells, respectively. And inhibiting TMEM45A can reduce the IC50 of SiHa/DDP cells and HeLa/DDP cells to cisplatin. Silencing TMEM45A can inhibit cell proliferation, invasion, migration and EMT, regulate cell cycle distribution, promote cell apoptosis, and reverse cisplatin resistance of HPV-positive cervical cancer cells, highlighting that inhibition of TMEM45A may be a therapeutic strategy for HPV-positive cervical cancer.

Predicting tumor response to drugs based on gene-expression biomarkers of sensitivity learned from cancer cell lines

Background

Human cancer cell line profiling and drug sensitivity studies provide valuable information about the therapeutic potential of drugs and their possible mechanisms of action. The goal of those studies is to translate the findings from in vitro studies of cancer cell lines into in vivo therapeutic relevance and, eventually, patients’ care. Tremendous progress has been made.

Results

In this work, we built predictive models for 453 drugs using data on gene expression and drug sensitivity (IC₅₀) from cancer cell lines. We identified many known drug-gene interactions and uncovered several potentially novel drug-gene associations. Importantly, we further applied these predictive models to ~ 17,000 bulk RNA-seq samples from The Cancer Genome Atlas (TCGA) and the Genotype-Tissue Expression (GTEx) database to predict drug sensitivity for both normal and tumor tissues. We created a web site for users to visualize and download our predicted data (https://manticore.niehs.nih.gov/cancerRxTissue). Using trametinib as an example, we showed that our approach can faithfully recapitulate the known tumor specificity of the drug.

Conclusions

We demonstrated that our approach can predict drugs that 1) are tumor-type specific; 2) elicit higher sensitivity from tumor compared to corresponding normal tissue; 3) elicit differential sensitivity across breast cancer subtypes. If validated, our prediction could have relevance for preclinical drug testing and in phase I clinical design.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07581-7.

Inhibitors of HSP90 in melanoma

HSP90 (heat shock protein 90) is an ATP-dependent molecular chaperone involved in a proper folding and maturation of hundreds of proteins. HSP90 is abundantly expressed in cancer, including melanoma. HSP90 client proteins are the key oncoproteins of several signaling pathways controlling melanoma development, progression and response to therapy. A number of natural and synthetic compounds of different chemical structures and binding sites within HSP90 have been identified as selective HSP90 inhibitors. The majority of HSP90-targeting agents affect N-terminal ATPase activity of HSP90. In contrast to N-terminal inhibitors, agents interacting with the middle and C-terminal domains of HSP90 do not induce HSP70-dependent cytoprotective response. Several inhibitors of HSP90 were tested against melanoma in pre-clinical studies and clinical trials, providing evidence that these agents can be considered either as single or complementary therapeutic strategy. This review summarizes current knowledge on the role of HSP90 protein in cancer with focus on melanoma, and provides an overview of structurally different HSP90 inhibitors that are considered as potential therapeutics for melanoma treatment.

17-Aminogeldanamycin selectively diminishes IRE1α-XBP1s pathway activity and cooperatively induces apoptosis with MEK1/2 and BRAFV600E inhibitors in melanoma cells of different genetic subtypes

Outcomes of melanoma patient treatment remain unsatisfactory despite accessibility of oncoprotein-targeting drugs and immunotherapy. Here, we reported that 17-aminogeldanamycin more potently activated caspase-3/7 in BRAF^V600E melanoma cells than geldanamycin, another inhibitor of heat shock protein 90 (HSP90). 17-aminogeldanamycin alleviated self-triggered compensatory increase in HSP70 mRNA level and induced endoplasmic reticulum (ER) stress, which was followed by selective diminution of cytoprotective IRE1α-XBP1s pathway activity of unfolded protein response (UPR), inhibition of ERK1/2 activity and induction of apoptosis. Concomitantly, ATF6/p50 level and expression of PERK-dependent genes, CHOP and BIM, remained unaltered. This might result from an inframe deletion in EIF2AK3 leading to a PERK^L21del variant revealed by whole-exome sequencing in melanoma cell lines. 17-aminogeldanamycin exhibited similar activity in NRAS^Q61R melanoma cells that harbored a heterozygous inactivating variant of NAD(P)H:quinone oxidoreductase 1 (NQO1^P187S). In addition, 17-aminogeldanamycin acted cooperatively with trametinib (an inhibitor of MEK1/2) and vemurafenib (an inhibitor of BRAF^V600E) in induction of apoptosis in melanoma cell lines as evidenced by in-cell caspase-3/7 activation and PARP cleavage that occurred earlier compared with either drug used alone. As trametinib and vemurafenib did not significantly affect HSP70 and GRP78 transcript levels, cooperation of MEK/BRAF^V600E inhibitors and 17-aminogeldanamycin might result from a concurrent inhibition of the RAS/RAF/MEK/ERK cascade and IRE1α-dependent signaling, and cell-intrinsic ER homeostasis can determine the extent of the drug cooperation. Our study indicates that 17-aminogeldanamycin takes several advantages compared with other HSP90-targeting compounds, and can complement activity of BRAF/MEK inhibitors in melanoma cells of different genetic subtypes.

HSP90 inhibitor 17AAG attenuates sevoflurane-induced neurotoxicity in rats and human neuroglioma cells via induction of HSP70

Background

17AAG has been extensively studied for its antitumor effects that protect cells from lethal stress by maintaining protein stability. The role of 17AAG in sevoflurane-induced neuronal injury has never been studied. We aim to investigate the effect of 17AAG on sevoflurane-induced neurotoxicity in vivo and in vitro.

Methods

Sevoflurane-induced hippocampal neuron injury model was established in aged Sprague–Dawley rats. Pretreatment of vehicle or 17AAG was administered prior to sevoflurane inhalation. H4 neuroglioma cells were pretreated with vehicle or 17AAG and exposed to sevoflurane. Apoptosis, oxidative stress, expression of interleukin-6 (IL-6), and activation of the nuclear factor-κB (NF-κB) signaling pathway in H4 cells were examined by Hoechst assay, flow cytometry, Western blot, and immunofluorescent staining. RNA interference against HSPA1A was performed to test the function of HSP70 in neuroprotection.

Results

Exogenous 17AAG reduced sevoflurane-induced apoptosis and oxidative stress in rat hippocampal neurons and in H4 cells. In H4 cells, 17AAG suppressed sevoflurane-induced upregulation of IL-6 and activation of NF-κB signaling. 17AAG enhanced sevoflurane-induced upregulation of HSP70 in rat hippocampal neurons and in H4 cells. Conversely, silencing of HSPA1A in H4 cells blocked the cytoprotective effect of 17AAG against sevoflurane-induced apoptosis and oxidative stress, and prevented upregulation of IL-6 and activation of NF-κB signaling.

Conclusions

17AAG protects against sevoflurane-induced neurotoxicity in vivo and in vitro via HSP70-dependent inhibition of apoptosis, oxidative stress, and pro-inflammatory signaling pathway.

Heat Shock Proteins in Glioblastoma Biology: Where Do We Stand?

Heat shock proteins (HSPs) are evolutionary conserved proteins that work as molecular chaperones and perform broad and crucial roles in proteostasis, an important process to preserve the integrity of proteins in different cell types, in health and disease. Their function in cancer is an important aspect to be considered for a better understanding of disease development and progression. Glioblastoma (GBM) is the most frequent and lethal brain cancer, with no effective therapies. In recent years, HSPs have been considered as possible targets for GBM therapy due their importance in different mechanisms that govern GBM malignance. In this review, we address current evidence on the role of several HSPs in the biology of GBMs, and how these molecules have been considered in different treatments in the context of this disease, including their activities in glioblastoma stem-like cells (GSCs), a small subpopulation able to drive GBM growth. Additionally, we highlight recent works that approach other classes of chaperones, such as histone and mitochondrial chaperones, as important molecules for GBM aggressiveness. Herein, we provide new insights into how HSPs and their partners play pivotal roles in GBM biology and may open new therapeutic avenues for GBM based on proteostasis machinery.

Therapies targeting the signal pathways of pheochromocytoma and paraganglioma

Pheochromocytoma and paraganglioma (PCC/PGL) are rare tumors that originate from adrenal or extra-adrenal chromaffin cells. A significant clinical manifestation of PCC/PGL is that the tumors release a large number of catecholamines continuously or intermittently, causing persistent or paroxysmal hypertension and multiple organ functions and metabolic disorders. Though majority of the tumors are non-metastatic, about 10% are metastatic tumors. Others even have estimated that the rate of metastasis may be as high as 26%. The disease is most common in individuals ranging from 20 to 50 years old and the age of onset strongly depends on the genetic background: patients with germline mutations in susceptible genes have an earlier presentation. Besides, there are no significant differences in the incidence between men and women. At present, traditional treatments, such as surgical treatment, radionuclide therapy, and chemotherapy are still prior choices. However, they all have several deficiencies so that the effects are not extremely significant. Contemporary studies have shown that hypoxia-associated signal pathway, associated with the cluster 1 genes of PCC/PGL, and increased kinase signal pathways, associated with the cluster 2 genes of PCC/PGL, are the two major pathways involving the molecular pathogenesis of PCC/PGL, indicating that PCC/PGL can be treated with targeted therapies in emerging trends. This article reviews the progress of molecular-targeted therapies for PCC/PGL.

Overcoming acquired resistance to HSP90 inhibition by targeting JAK-STAT signalling in triple-negative breast cancer

Background

Due to the lack of effective therapies and poor prognosis in TNBC (triple-negative breast cancer) patients, there is a strong need to develop effective novel targeted therapies for this subtype of breast cancer. Inhibition of heat shock protein 90 (HSP90), a conserved molecular chaperone that is involved in the regulation of oncogenic client proteins, has shown to be a promising therapeutic approach for TNBC. However, both intrinsic and acquired resistance to HSP90 inhibitors (HSP90i) limits their effectiveness in cancer patients.

Methods

We developed models of acquired resistance to HSP90i by prolonged exposure of TNBC cells to HSP90i (ganetespib) in vitro. Whole transcriptome profiling and a 328-compound bioactive small molecule screen were performed on these cells to identify the molecular basis of acquired resistance to HSP90i and potential therapeutic approaches to overcome resistance.

Results

Among a panel of seven TNBC cell lines, the most sensitive cell line (Hs578T) to HSP90i was selected as an in vitro model to investigate acquired resistance to HSP90i. Two independent HSP90i-resistant clones were successfully isolated which both showed absence of client proteins degradation, apoptosis induction and G2/M cell cycle arrest after treatment with HSP90i. Gene expression profiling and pathway enrichment analysis demonstrate significant activation of the survival JAK-STAT signalling pathway in both HSP90i-resistant clones, possibly through IL6 autocrine signalling. A bioactive small molecule screen also demonstrated that the HSP90i-resistant clones showed selective sensitivity to JAK2 inhibition. Inhibition of JAK and HSP90 caused higher induction of apoptosis, despite prior acquired resistance to HSP90i.

Conclusions

Acquired resistance to HSP90i in TNBC cells is associated with an upregulated JAK-STAT signalling pathway. A combined inhibition of the JAK-STAT signalling pathway and HSP90 could overcome this resistance. The benefits of the combined therapy could be explored further for the development of effective targeted therapy in TNBC patients.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5295-z) contains supplementary material, which is available to authorized users.

The germline genetic component of drug sensitivity in cancer cell lines

Patients with seemingly the same tumour can respond very differently to treatment. There are strong, well-established effects of somatic mutations on drug efficacy, but there is at-most anecdotal evidence of a germline component to drug response. Here, we report a systematic survey of how inherited germline variants affect drug susceptibility in cancer cell lines. We develop a joint analysis approach that leverages both germline and somatic variants, before applying it to screening data from 993 cell lines and 265 drugs. Surprisingly, we find that the germline contribution to variation in drug susceptibility can be as large or larger than effects due to somatic mutations. Several of the associations identified have a direct relationship to the drug target. Finally, using 17-AAG response as an example, we show how germline effects in combination with transcriptomic data can be leveraged for improved patient stratification and to identify new markers for drug sensitivity.

Little is known about the contribution of germline genetic variants to cancer drug sensitivity. Here, the authors devise an approach for joint analysis of germline variants and somatic mutations, identifying substantial germline contributions to variation in drug sensitivity.

Prospective identification of resistance mechanisms to HSP90 inhibition in KRAS mutant cancer cells

Inhibition of the HSP90 chaperone results in depletion of many signaling proteins that drive tumorigenesis, such as downstream effectors of KRAS, the most commonly mutated human oncogene. As a consequence, several small-molecule HSP90 inhibitors are being evaluated in clinical trials as anticancer agents. To prospectively identify mechanisms through which HSP90-dependent cancer cells evade pharmacologic HSP90 blockade, we generated multiple mutant KRAS-driven cancer cell lines with acquired resistance to the purine-scaffold HSP90 inhibitor PU-H71. All cell lines retained dependence on HSP90 function, as evidenced by sensitivity to short hairpin RNA-mediated suppression of HSP90AA1 or HSP90AB1 (also called HSP90α and HSP90β, respectively), and exhibited two types of genomic alterations that interfere with the effects of PU-H71 on cell viability and proliferation: (i) a Y142N missense mutation in the ATP-binding domain of HSP90α that co-occurred with amplification of the HSP90AA1 locus, (ii) genomic amplification and overexpression of the ABCB1 gene encoding the MDR1 drug efflux pump. In support of a functional role for these alterations, exogenous expression of HSP90α Y142N conferred PU-H71 resistance to HSP90-dependent cells, and pharmacologic MDR1 inhibition with tariquidar or lowering ABCB1 expression restored sensitivity to PU-H71 in ABCB1-amplified cells. Finally, comparison with structurally distinct HSP90 inhibitors currently in clinical development revealed that PU-H71 resistance could be overcome, in part, by ganetespib (also known as STA9090) but not tanespimycin (also known as 17-AAG). Together, these data identify potential mechanisms of acquired resistance to small molecules targeting HSP90 that may warrant proactive screening for additional HSP90 inhibitors or rational combination therapies.

Cdc7-Dbf4-mediated phosphorylation of HSP90-S164 stabilizes HSP90-HCLK2-MRN complex to enhance ATR/ATM signaling that overcomes replication stress in cancer

Cdc7-Dbf4 kinase plays a key role in the initiation of DNA replication and contributes to the replication stress in cancer. The activity of human Cdc7-Dbf4 kinase remains active and acts as an effector of checkpoint under replication stress. However, the downstream targets of Cdc7-Dbf4 contributed to checkpoint regulation and replication stress-support function in cancer are not fully identified. In this work, we showed that aberrant Cdc7-Dbf4 induces DNA lesions that activate ATM/ATR-mediated checkpoint and homologous recombination (HR) DNA repair. Using a phosphoproteome approach, we identified HSP90-S164 as a target of Cdc7-Dbf4 in vitro and in vivo. The phosphorylation of HSP90-S164 by Cdc7-Dbf4 is required for the stability of HSP90-HCLK2-MRN complex and the function of ATM/ATR signaling cascade and HR DNA repair. In clinically, the phosphorylation of HSP90-S164 indeed is increased in oral cancer patients. Our results indicate that aberrant Cdc7-Dbf4 enhances replication stress tolerance by rewiring ATR/ATM mediated HR repair through HSP90-S164 phosphorylation and by promoting recovery from replication stress. We provide a new solution to a subtyping of cancer patients with dominant ATR/HSP90 expression by combining inhibitors of ATR-Chk1, HSP90, or Cdc7 in cancer combination therapy.

The small-molecule kinase inhibitor D11 counteracts 17-AAG-mediated up-regulation of HSP70 in brain cancer cells

Many types of cancer express high levels of heat shock proteins (HSPs) that are molecular chaperones regulating protein folding and stability ensuring protection of cells from potentially lethal stress. HSPs in cancer cells promote survival, growth and spreading even in situations of growth factors deprivation by associating with oncogenic proteins responsible for cell transformation. Hence, it is not surprising that the identification of potent inhibitors of HSPs, notably HSP90, has been the primary research focus, in recent years. Exposure of cancer cells to HSP90 inhibitors, including 17-AAG, has been shown to cause resistance to chemotherapeutic treatment mostly attributable to induction of the heat shock response and increased cellular levels of pro-survival chaperones. In this study, we show that treatment of glioblastoma cells with 17-AAG leads to HSP90 inhibition indicated by loss of stability of the EGFR client protein, and significant increase in HSP70 expression. Conversely, co-treatment with the small-molecule kinase inhibitor D11 leads to suppression of the heat shock response and inhibition of HSF1 transcriptional activity. Beside HSP70, Western blot and differential mRNA expression analysis reveal that combination treatment causes strong down-regulation of the small chaperone protein HSP27. Finally, we demonstrate that incubation of cells with both agents leads to enhanced cytotoxicity and significantly high levels of LC3-II suggesting autophagy induction. Taken together, results reported here support the notion that including D11 in future treatment regimens based on HSP90 inhibition can potentially overcome acquired resistance induced by the heat shock response in brain cancer cells.

NVP-AUY922, a novel HSP90 inhibitor, inhibits the progression of malignant pheochromocytoma in vitro and in vivo

Purpose

Malignant pheochromocytoma (PCC) is a rare tumor with a very poor prognosis and no effective treatments. The aim of this study was to assess the efficacy of a novel second-generation synthetic heat-shock protein 90 (HSP90) inhibitor, NVP-AUY922, to treat malignant PCC in vitro and in vivo.

Materials and methods

Cell Counting Kit-8 (CCK-8) and Transwell assays were used to assess the effects of NVP-AUY922 on the proliferation and migration of the PCC cell line PC12. Flow cytometry was used to determine the effects of NVP-AUY922 on apoptosis and cell-cycle progression. Activation of phosphatidylinositol-3-kinase (PI3K)/protein kinase B (PKB/AKT) and mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) signaling was measured using a Western blot analysis. In vivo, a mouse xenograft model was used to test the effects of intraperitoneal injection of NVP-AUY922 on tumor growth.

Results

NVP-AUY922 was found to be cytotoxic in PC12 cells at lower concentrations compared with 17-allylamino-17-demethoxygeldanamcyin (17-AAG). NVP-AUY922 inhibited the proliferation of PC12 cells in a time- and concentration-dependent manner and decreased the rate of migration of PC12 cells. Furthermore, we found that HSP90 inhibition induced cell-cycle arrest and apoptosis. In vivo, administration of NVP-AUY922 reduced PCC tumor growth without significant weight loss. Finally, we observed the modulation of MEK/ERK and PI3K/AKT signaling in response to NVP-AUY922 exposure.

Conclusion

NVP-AUY922 exhibits potent anti-PCC activities in vitro and in vivo and represents a promising therapeutic small molecule for treating malignant PCC.

Histone deacetylase activity mediates acquired resistance towards structurally diverse HSP90 inhibitors

Heat shock protein 90 (HSP90) regulates multiple signalling pathways critical for tumour growth. As such, HSP90 inhibitors have been shown to act as effective anticancer agents in preclinical studies but, for a number of reasons, the same effect has not been observed in the clinical trials to date. One potential reason for this may be the presence of de novo or acquired resistance within the tumours. To investigate mechanisms of resistance, we generated resistant cell lines through gradual dose escalation of the HSP90 inhibitor 17‐allylamino‐17‐demethoxygeldanamycin (17‐AAG). The resultant resistant cell lines maintained their respective levels of resistance (7–240×) in the absence of 17‐AAG and were also cross‐resistant with other benzoquinone ansamycin HSP90 inhibitors. Expression of members of the histone deacetylase family (HDAC 1, 5, 6) was altered in the resistant cells. To determine whether HDAC activity contributed to resistance, pan‐HDAC inhibitors (TSA and LBH589) and the class II HDAC‐specific inhibitor SNDX275 were found to resensitize resistant cells towards 17‐AAG and 17‐dimethylaminoethylamino‐17‐demethoxygeldanamycin. Most significantly, resistant cells were also identified as cross‐resistant towards structurally distinct HSP90 inhibitors such as radicicol and the second‐generation HSP90 inhibitors CCT018159, VER50589 and AUY922. HDAC inhibition also resensitized resistant cells towards these classes of HSP90 inhibitors. In conclusion, we report that prolonged 17‐AAG treatment results in acquired resistance of cancer cells towards not just 17‐AAG but also to a spectrum of structurally distinct HSP90 inhibitors. This acquired resistance can be inhibited using clinically relevant HDAC inhibitors. This work supports the potential benefit of using HSP90 and HDAC inhibitors in combination within the clinical setting.

Lectin, Galactoside-Binding Soluble 3 Binding Protein Promotes 17-N-Allylamino-17-demethoxygeldanamycin Resistance through PI3K/Akt Pathway in Lung Cancer Cell Line

Heat shock protein 90 (HSP90) stabilizing oncoproteins has been an attractive target in cancer therapy. 17-N-Allylamino-17-demethoxygeldanamycin (17-AAG), an HSP90 inhibitor, was tested in phase II/III clinical trials, but due to lack of efficacy, clinical evaluation of 17-AAG has achieved limited success, which led to resistance to 17-AAG. However, the mechanism of 17-AAG resistance has not clearly been identified. Here, we identified LGALS3BP (Lectin, galactoside-binding soluble 3 binding protein), a secretory glycoprotein, as a 17-AAG resistance factor. In the clinical reports, it was suggested that LGALS3BP was associated with low survival rate, development of cancer progression, and enhancement of metastasis in human cancers. As we confirmed that the LGALS3BP level was increased in 17-AAG-resistant cells (H1299_17R) compared with that of the parental cell line (H1299_17P), knockdown of LGALS3BP expression increased sensitivity to 17-AAG in H1299_17R cells. Overexpression of LGALS3BP also augmented PI3K/Akt and ERK signaling pathways. Furthermore, we determined that the PI3K/Akt signaling pathway was involved in LGALS3BP-mediated 17-AAG resistance in vitro and in vivo, demonstrating that LGALS3BP mediates the resistance against 17-AAG through PI3K/Akt activation rather than ERK activation. These findings suggest that LGALS3BP would be a target to overcome resistance to 17-AAG in lung cancer. For example, the combination of 17-AAG and PI3K/Akt inhibitor would effectively suppress acquired resistance to 17-AAG. In conclusion, targeting of LGALS3BP-mediated-specific survival signaling pathway in resistant cells may provide a novel therapeutic model for the cancer therapy. Mol Cancer Ther; 16(7); 1355-65. ©2017 AACR.

Re-examining HSPC1 inhibitors

HSPC1 is a critical protein in cancer development and progression, including colorectal cancer (CRC). However, clinical trial data reporting the effectiveness of HSPC1 inhibitors on several cancer types has not been as successful as predicted. Furthermore, some N-terminal inhibitors appear to be much more successful than others despite similar underlying mechanisms. This study involved the application of three N-terminal HSPC1 inhibitors, 17-DMAG, NVP-AUY922 and NVP-HSP990 on CRC cells. The effects on client protein levels over time were examined. HSPC1 inhibitors were also applied in combination with chemotherapeutic agents commonly used in CRC treatment (5-fluorouracil, oxaliplatin and irinotecan). As HSPA1A and HSPB1 have anti-apoptotic activity, gene-silencing techniques were employed to investigate the significance of these proteins in HSPC1 inhibitor and chemotherapeutic agent resistance. When comparing the action of the three HSPC1 inhibitors, there are distinct differences in the time course of important client protein degradation events. The differences between HSPC1 inhibitors were also reflected in combination treatment-17-DMAG was more effective compared with NVP-AUY922 in potentiating the cytotoxic effects of 5-fluorouracil, oxaliplatin and irinotecan. This study concludes that there are distinct differences between N-terminal HSPC1 inhibitors, despite their common mode of action. Although treatment with each of the inhibitors results in significant induction of the anti-apoptotic proteins HSPA1A and HSPB1, sensitivity to HSPC1 inhibitors is not improved by gene silencing of HSPA1A or HSPB1. HSPC1 inhibitors potentiate the cytotoxic effects of chemotherapeutic agents in CRC, and this approach is readily available to enter clinical trials. From a translational point of view, there may be great variability in sensitivity to the inhibitors between individual patients.

Azoreductases in drug metabolism

Azoreductases are flavoenzymes that have been characterized in a range of prokaryotes and eukaryotes. Bacterial azoreductases are associated with the activation of two classes of drug, azo drugs for the treatment of inflammatory bowel disease and nitrofuran antibiotics. The mechanism of reduction of azo compounds is presented; it requires tautomerisation of the azo compound to a quinoneimine and provides a unifying mechanism for the reduction of azo and quinone substrates by azoreductases. The importance of further work in the characterization of azoreductases from enteric bacteria is highlighted to aid in the development of novel drugs for the treatment of colon related disorders. Human azoreductases are known to play a crucial role in the metabolism of a number of quinone-containing cancer chemotherapeutic drugs. The mechanism of hydride transfer to quinones, which is shared not only between eukaryotic and prokaryotic azoreductases but also the wider family of NAD(P)H quinone oxidoreductases, is outlined. The importance of common single nucleotide polymorphisms (SNPs) in human azoreductases is described not only in cancer prognosis but also with regard to their effects on the efficacy of quinone drug-based cancer chemotherapeutic regimens. This highlights the need to screen patients for azoreductase SNPs ahead of treatment with these regimens.

LINKED ARTICLES

This article is part of a themed section on Drug Metabolism and Antibiotic Resistance in Micro-organisms. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.14/issuetoc.

Acquired resistance to HSP90 inhibitor 17-AAG and increased metastatic potential are associated with MUC1 expression in colon carcinoma cells

Heat shock protein 90 (HSP90) is a molecular chaperone required for the stability and function of many proteins. The chaperoning of oncoproteins by HSP90 enhances the survival, growth, and invasive potential of cancer cells. HSP90 inhibitors are promising new anticancer agents, in which the benzoquinone ansamycin 17-allylamino-17-demethoxygeldanamycin (17-AAG) is currently in clinical evaluation. However, the implications of acquired resistance to this class of drug remain largely unexplored. In the present study, we have generated isogenic human colon cancer cell lines that are resistant to 17-AAG by continued culturing in the compound. Cross-resistance was found with another HSP90 inhibitor 17-dimethylaminoethylamino-17-demethoxygeldanamycin. The resistant cells showed obvious morphology changes with a metastatic phenotype and significant increases in migration and adhesion to collagens. Western blotting analysis of epithelial-mesenchymal transition molecular markers found that expression of E-cadherin downregulated, whereas expression of N-cadherin and β-catenin upregulated in the resistant cells. Mucin 1 (MUC1) has been reported to mediate metastasis as well as chemical resistance in many cancers. Here, we found that MUC1 expression was significantly elevated in the acquired drug resistance cells. 17-AAG treatment could decrease MUC1 more in parental cells than in acquired 17-AAG-resistant cells. Further study found that knockdown of MUC1 expression by small interfering RNA could obviously re-sensitize the resistant cells to 17-AAG treatment, and decrease the cell migration and adhesion. These were coupled with a downregulation in N-cadherin and β-catenin. The results indicate that HSP90 inhibitor therapies in colon carcinomas could generate resistance and increase metastatic potential that might mediated by upregulation of MUC1 expression. Findings from this study further our understanding of the potential clinical effects of HSP90-directed therapies in colon carcinomas.

Second-Generation HSP90 Inhibitor Onalespib Blocks mRNA Splicing of Androgen Receptor Variant 7 in Prostate Cancer Cells

Resistance to available hormone therapies in prostate cancer has been associated with alternative splicing of androgen receptor (AR) and specifically, the expression of truncated and constitutively active AR variant 7 (AR-V7). The transcriptional activity of steroid receptors, including AR, is dependent on interactions with the HSP90 chaperone machinery, but it is unclear whether HSP90 modulates the activity or expression of AR variants. Here, we investigated the effects of HSP90 inhibition on AR-V7 in prostate cancer cell lines endogenously expressing this variant. We demonstrate that AR-V7 and full-length AR (AR-FL) were depleted upon inhibition of HSP90. However, the mechanisms underlying AR-V7 depletion differed from those for AR-FL. Whereas HSP90 inhibition destabilized AR-FL and induced its proteasomal degradation, AR-V7 protein exhibited higher stability than AR-FL and did not require HSP90 chaperone activity. Instead, HSP90 inhibition resulted in the reduction of AR-V7 mRNA levels but did not affect total AR transcript levels, indicating that HSP90 inhibition disrupted AR-V7 splicing. Bioinformatic analyses of transcriptome-wide RNA sequencing data confirmed that the second-generation HSP90 inhibitor onalespib altered the splicing of at least 557 genes in prostate cancer cells, including AR. These findings indicate that the effects of HSP90 inhibition on mRNA splicing may prove beneficial in prostate cancers expressing AR-V7, supporting further clinical investigation of HSP90 inhibitors in malignancies no longer responsive to androgen deprivation. Cancer Res; 76(9); 2731-42. ©2016 AACR.

Localization of MRP-1 to the outer mitochondrial membrane by the chaperone protein HSP90β

Overexpression of plasma membrane multidrug resistance-associated protein 1 (MRP-1) in Ewing's sarcoma (ES) predicts poor outcome. MRP-1 is also expressed in mitochondria, and we have examined the submitochondrial localization of MRP-1 and investigated the mechanism of MRP-1 transport and role of this organelle in the response to doxorubicin. The mitochondrial localization of MRP-1 was examined in ES cell lines by differential centrifugation and membrane solubilization by digitonin. Whether MRP-1 is chaperoned by heat shock proteins (HSPs) was investigated by immunoprecipitation, immunofluorescence microscopy, and HSP knockout using small hairpin RNA and inhibitors (apoptozole, 17-AAG, and NVPAUY). The effect of disrupting mitochondrial MRP-1-dependent efflux activity on the cytotoxic effect of doxorubicin was investigated by counting viable cell number. Mitochondrial MRP-1 is glycosylated and localized to the outer mitochondrial membrane, where it is coexpressed with HSP90. MRP-1 binds to both HSP90 and HSP70, although only inhibition of HSP90β decreases expression of MRP-1 in the mitochondria. Disruption of mitochondrial MRP-1-dependent efflux significantly increases the cytotoxic effect of doxorubicin (combination index, <0.9). For the first time, we have demonstrated that mitochondrial MRP-1 is expressed in the outer mitochondrial membrane and is a client protein of HSP90β, where it may play a role in the doxorubicin-induced resistance of ES.-Roundhill, E., Turnbull, D., Burchill, S. Localization of MRP-1 to the outer mitochondrial membrane by the chaperone protein HSP90β.

Maximizing the Therapeutic Potential of HSP90 Inhibitors

HSP90 is required for maintaining the stability and activity of a diverse group of client proteins, including protein kinases, transcription factors, and steroid hormone receptors involved in cell signaling, proliferation, survival, oncogenesis, and cancer progression. Inhibition of HSP90 alters the HSP90-client protein complex, leading to reduced activity, misfolding, ubiquitination, and, ultimately, proteasomal degradation of client proteins. HSP90 inhibitors have demonstrated significant antitumor activity in a wide variety of preclinical models, with evidence of selectivity for cancer versus normal cells. In the clinic, however, the efficacy of this class of therapeutic agents has been relatively limited to date, with promising responses mainly observed in breast and lung cancer, but no major activity seen in other tumor types. In addition, adverse events and some significant toxicities have been documented. Key to improving these clinical outcomes is a better understanding of the cellular consequences of inhibiting HSP90 that may underlie treatment response or resistance. This review considers the recent progress that has been made in the study of HSP90 and its inhibitors and highlights new opportunities to maximize their therapeutic potential.

Deoxynyboquinones as NQO1-Activated Cancer Therapeutics

One of the major goals of cancer therapy is the selective targeting of cancer cells over normal cells. Unfortunately, even with recent advances, the majority of chemotherapeutics still indiscriminately kill all rapidly dividing cells. Although these drugs are effective in certain settings, their inability to specifically target cancer results in significant dose-limiting toxicities. One way to avoid such toxicities is to target an aspect of the cancer cell that is not shared by normal cells. A potential cancer-specific target is the enzyme NAD(P)H quinone oxidoreductase 1 (NQO1). NQO1 is a 2-electron reductase responsible for the detoxification of quinones. Its expression is typically quite low in normal tissue, but it has been found to be greatly overexpressed in many types of solid tumors, including lung, breast, pancreatic, and colon cancers. This overexpression is thought to be in response to the higher oxidative stress of the cancer cell, and it is possible that NQO1 contributes to tumor progression. The overexpression of NQO1 and its correlation with poor patient outcome make it an intriguing target. Although some have explored inhibiting NQO1 as an anticancer strategy, this has generally been unsuccessful. A more promising strategy is to utilize NQO1 substrates that are activated upon reduction by NQO1. For example, in principle, reduction of a quinone can result in a hydroquinone that is a DNA alkylator, protein inhibitor, or reduction-oxidation cycler. Although there are many proposed NQO1 substrates, head-to-head assays reveal only two classes of compounds that convincingly induce cancer cell death through NQO1-mediated activation. In this Account, we describe the discovery and development of one of these compounds, the natural product deoxynyboquinone (DNQ), an excellent NQO1 substrate and anticancer agent. A modular synthesis of DNQ was developed that enabled access to the large compound quantities needed to conduct extensive mechanistic evaluations and animal experiments. During these evaluations, we found that DNQ is an outstanding NQO1 substrate that is processed much more efficiently than other putative NQO1 substrates. Importantly, its anticancer activity is strictly dependent on the overexpression of active NQO1. Using previous crystal structures of NQO1, novel DNQ derivatives were designed that are also excellent NQO1 substrates and possess properties that make them more attractive than the parent natural product for translational development. Given their selectivity, potency, outstanding pharmacokinetic properties, and the ready availability of diagnostics to assess NQO1 in patients, DNQ and its derivatives have considerable potential as personalized medicines for the treatment of cancer.

P-glycoprotein confers acquired resistance to 17-DMAG in lung cancers with an ALK rearrangement

BACKGROUND

Because anaplastic lymphoma kinase (ALK) is dependent on Hsp90 for protein stability, Hsp90 inhibitors are effective in controlling growth of lung cancer cells with ALK rearrangement. We investigated the mechanism of acquired resistance to 17-(Dimethylaminoethylamino)-17-demethoxygeldanamycin (17-DMAG), a geldanamycin analogue Hsp90 inhibitor, in H3122 and H2228 non-small cell lung cancer cell lines with ALK rearrangement.

METHODS

Resistant cell lines (H3122/DR-1, H3122/DR-2 and H2228/DR) were established by repeated exposure to increasing concentrations of 17-DMAG. Mechanisms for resistance by either NAD(P)H/quinone oxidoreductase 1 (NQO1), previously known as a factor related to 17-DMAG resistance, or P-glycoprotein (P-gp; ABCB1/MDR1) were queried using RT-PCR, western blot analysis, chemical inhibitors, the MTT cell proliferation/survival assay, and cellular efflux of rhodamine 123.

RESULTS

The resistant cells showed no cross-resistance to AUY922 or ALK inhibitors, suggesting that ALK dependency persists in cells with acquired resistance to 17-DMAG. Although expression of NQO1 was decreased in H3122/DR-1 and H3122/DR-2, NQO1 inhibition by dicumarol did not affect the response of parental cells (H2228 and H3122) to 17-DMAG. Interestingly, all resistant cells showed the induction of P-gp at the protein and RNA levels, which was associated with an increased efflux of the P-gp substrate rhodamine 123 (Rho123). Transfection with siRNA directed against P-gp or treatment with verapamil, an inhibitor of P-gp, restored the sensitivity to the drug in all cells with acquired resistance to 17-DMAG. Furthermore, we also observed that the growth-inhibitory effect of 17-DMAG was decreased in A549/PR and H460/PR cells generated to over-express P-gp by long-term exposure to paclitaxel, and these cells recovered their sensitivity to 17-DMAG through the inhibition of P-gp.

CONCLUSION

P-gp over-expression is a possible mechanism of acquired resistance to 17-DMAG in cells with ALK rearrangement.

Stimulation of electroporation-induced inward currents in glioblastoma cell lines by the heat shock protein inhibitor AUY922

Membrane electroporation (MEP) increases the electrical conductivity of the plasma membrane by addition of an external electrical field. Combining MEP-induced current (IMEP ) with antineoplastic agents has been increasingly considered as a new therapeutic manoeuvre, especially in the treatment of malignant gliomas. Thus, the aim of the present study was to evaluate the effect of AUY922 (AUY), a potent inhibitor of heat-shock protein 90 (HSP90), on IMEP in glioblastoma cells. The IMEP in glioblastoma cells (U373) was generated by repetitive hyperpolarization from -80 to -200 mV. The amplitude of IMEP was increased by AUY in a concentration-dependent manner, with an EC50 of 0.32 μmol/L. In addition AUY shortened the latency to IMEP generation. Before depolarization to +50 mV, hyperpolarization to -200 mV for 50 msec produced Ca(2+) influx and subsequently increased the amplitude of the Ca(2+) -activated K(+) current (IK(Ca) ). The amplitude of IK(Ca) and Ca(2+) influx was further increased by AUY through its ability to activate IMEP . Other HSP90 inhibitors, namely 17-(allylamino)-17-demethoxygeldanamycin (17-AAG; 1 μmol/L) and 6-chloro-9-[(4-methoxy-3,5-dimethylpyridin-2-yl)methyl]-9H-purin-2-amine (BIIB021; 1 μmol/L), only slightly (albeit significantly) increased the amplitude of IMEP in glioblastoma cells. A 50 msec depolarizing step elevated Ca(2+) influx and subsequently increased the amplitude of IK(Ca) in the presence of these three inhibitors. These data indicate that the AUY-mediated stimulation of IMEP and IK(Ca) in glioblastoma cells is independent of HSP90 inhibition. Moreover, these results indicate that AUY-stimulated IMEP and the subsequent activation of IK(Ca) may create important signalling events in glioblastoma cells. Thus, AUY is a drug that could potentially be used to augment the effectiveness of electrochemotherapy.

Glioblastoma multiforme: Pathogenesis and treatment

Each year, about 5-6 cases out of 100,000 people are diagnosed with primary malignant brain tumors, of which about 80% are malignant gliomas (MGs). Glioblastoma multiforme (GBM) accounts for more than half of MG cases. They are associated with high morbidity and mortality. Despite current multimodality treatment efforts including maximal surgical resection if feasible, followed by a combination of radiotherapy and/or chemotherapy, the median survival is short: only about 15months. A deeper understanding of the pathogenesis of these tumors has presented opportunities for newer therapies to evolve and an expectation of better control of this disease. Lately, efforts have been made to investigate tumor resistance, which results from complex alternate signaling pathways, the existence of glioma stem-cells, the influence of the blood-brain barrier as well as the expression of 0(6)-methylguanine-DNA methyltransferase. In this paper, we review up-to-date information on MGs treatment including current approaches, novel drug-delivering strategies, molecular targeted agents and immunomodulative treatments, and discuss future treatment perspectives.

Hsp90 inhibitor as a sensitizer of cancer cells to different therapies (review)

Hsp90 is a molecular chaperone that maintains the structural and functional integrity of various client proteins involved in signaling and many other functions of cancer cells. The natural inhibitors, ansamycins influence the Hsp90 chaperone function by preventing its binding to client proteins and resulting in their proteasomal degradation. N- and C-terminal inhibitors of Hsp90 and their analogues are widely tested as potential anticancer agents in vitro, in vivo as well as in clinical trials. It seems that Hsp90 competitive inhibitors target different tumor types at nanomolar concentrations and might have therapeutic benefit. On the contrary, some Hsp90 inhibitors increased toxicity and resistance of cancer cells induced by heat shock response, and through the interaction of survival signals, that occured as side effects of treatments, could be very effectively limited via combination of therapies. The aim of our review was to collect the data from experimental and clinical trials where Hsp90 inhibitor was combined with other therapies in order to prevent resistance as well as to potentiate the cytotoxic and/or antiproliferative effects.

Comparative Study of 17-AAG and NVP-AUY922 in Pancreatic and Colorectal Cancer Cells: Are There Common Determinants of Sensitivity?

The use of heat shock protein 90 (Hsp90) inhibitors is an attractive antineoplastic therapy. We wanted to compare the effects of the benzoquinone 17-allylamino-17-demethoxygeldanamycin (17-AAG, tanespimycin) and the novel isoxazole resorcinol–based Hsp90 inhibitor NVP-AUY922 in a panel of pancreatic and colorectal carcinoma cell lines and in colorectal primary cultures derived from tumors excised to patients. PANC-1, CFPAC-1, and Caco-2 cells were intrinsically resistant to 17-AAG but sensitive to NVP-AUY922. Other cellular models were sensitive to both inhibitors. Human epidermal growth factor receptor receptors and their downstream signaling pathways were downregulated in susceptible cellular models, and concurrently, Hsp70 was induced. Intrinsic resistance to 17-AAG did not correlate with expression of ATP-binding cassette transporters involved in multidrug resistance. Some 17-AAG-resistant, NVP-AUY922–sensitive cell lines lacked NAD(P)H:quinone oxidoreductase 1 (NQO1) enzyme and activity. However, colorectal LoVo cells still responded to both drugs in spite of having undetectable levels and activity of NQO1. Pharmacological and biologic inhibition of NQO1 did not confer resistance to 17-AAG in sensitive cell lines. Therefore, even though 17-AAG sensitivity is related to NQO1 protein levels and enzymatic activity, the absence of NQO1 does not necessarily convey resistance to 17-AAG in these cellular models. Moreover, NVP-AUY922 does not require NQO1 for its action and is a more potent inhibitor than 17-AAG in these cells. More importantly, we show in this report that NVP-AUY922 potentiates the inhibitory effects of chemotherapeutic agents, such as gemcitabine or oxaliplatin, and other drugs that are currently being evaluated in clinical trials as antitumor agents.

Phase I dose-escalation studies of SNX-5422, an orally bioavailable heat shock protein 90 inhibitor, in patients with refractory solid tumours

BACKGROUND

Orally administered SNX-5422, a novel, selective prodrug of the Heat shock protein 90 (Hsp90) inhibitor SNX-2112, was investigated in two sequential phase I studies to determine the safety, maximum tolerated doses (MTDs) and pharmacokinetic profile of SNX-5422.

METHODS

Using a dose-escalation design, 3-6 adults with advanced solid tumours received SNX-5422 every-other-day (QOD) or once-daily (QD) 3weeks on/1week off or QD continuously, with disease assessments every 8 weeks. Single-dose and steady-state pharmacokinetic parameters of SNX-2112 were determined.

RESULTS

In total, 56 patients were enrolled: QOD 3 weeks on/1 week off, n=36; QD 3weeks on/1 week off, n=17; QD continuous, n=3. Doses ranged from 4 to 133mg/m(2) QOD and 50 to 89 mg/m(2) QD. The MTDs were defined as 100mg/m(2) QOD and 67 mg/m(2) QD, respectively, with diarrhoea being dose-limiting on both 3 weeks on/1 week off schedules. Overall, treatment-related adverse events were mainly low grade, including diarrhoea (64%), nausea (39%), fatigue (28%), and vomiting (28%). Reversible grade 1-3 nyctalopia (night blindness) was reported by four patients (dose: 50-89mg/m(2) QD; 100mg/m(2) QOD). Exposure was generally linear, though greater than dose-proportional. Of 32 evaluable patients on QOD dosing, there was one durable complete response (prostate cancer), one confirmed (HER2+breast cancer) and one unconfirmed partial response (adrenal gland cancer). Three patients (QOD schedule) had stable disease for ⩾ 6 months.

CONCLUSIONS

The dose and schedule recommended for further study with SNX-5422 is 100mg/m(2) QOD 3 weeks on/1 week off based on improved tolerability and preliminary evidence of clinical activity.

UDP glucuronosyltransferase 1A expression levels determine the response of colorectal cancer cells to the heat shock protein 90 inhibitor ganetespib

HSP90 inhibition represents a promising route to cancer therapy, taking advantage of cancer cell-inherent proteotoxic stress. The HSP90-inhibitor ganetespib showed benefit in advanced clinical trials. This raises the need to identify the molecular determinants of treatment response. We tested the efficacy of ganetespib on a series of colorectal cancer (CRC)-derived cell lines and correlated their sensitivities with comprehensive gene expression analysis. Notably, the drug concentration required for 50% growth inhibition (IC₅₀) varied up to 70-fold (from 36 to 2500 nM) between different cell lines. Correlating cell line-specific IC₅₀s with the corresponding gene expression patterns revealed a strong association between ganetespib resistance (IC₅₀>500 nM) and high expression of the UDP glucuronosyltransferase 1A (UGT1A) gene cluster. Moreover, CRC tumor samples showed a comparable distribution of UGT1A expression levels. The members of the UGT1A gene family are known as drug-conjugating liver enzymes involved in drug excretion, but their function in tumor cells is hardly understood. Chemically unrelated HSP90 inhibitors, for example, 17-N-allylamino-17-demethoxygeldanamycin (17-AAG), did not show correlation of drug sensitivities with UGT1A levels, whereas the ganetespib-related compound NVP-AUY922 did. When the most ganetespib-resistant cell line, HT29, was treated with ganetespib, the levels of HSP90 clients were unaffected. However, HT29 cells became sensitized to the drug, and HSP90 client proteins were destabilized by ganetespib upon siRNA-mediated UGT1A knockdown. Conversely, the most ganetespib-sensitive cell lines HCT116 and SW480 became more tolerant toward ganetespib upon UGT1A overexpression. Mechanistically, ganetespib was rapidly glucuronidated and excreted in resistant but not in sensitive CRC lines. We conclude that CRC cell-expressed UGT1A inactivates ganetespib and other resorcinolic Hsp90 inhibitors by glucuronidation, which renders the drugs unable to inhibit Hsp90 and thereby abrogates their biological activity. UGT1A levels in tumor tissues may be a suitable predictive biomarker to stratify CRC patients for ganetespib treatment.

Synuclein gamma protects HER2 and renders resistance to Hsp90 disruption

Hsp90 is an important driver of stabilization and activation of several oncogenic proteins in many key pathways in oncogenesis, including HER2. The present study demonstrated that synuclein gamma (SNCG) prevents the protein degradation and protects the function of HER2 in the condition when the function of Hsp90 is blocked. Disruption of Hsp90 resulted in a significant degradation of HER2 and the loss of activity. However, SNCG completely recovered Hsp90 disruption-mediated losses of HER2 and the function. SNCG bound to HER2 in the presence and absence of Hsp90. Specifically, the C-terminal (Gln106-Asp127) of SNCG bound to the loop connecting αC helix and β4 sheet of the kinase domain of HER2. SNCG renders resistance to 17-AAG-induced tumor suppression in tumor xenograft. Crossing SNCG transgenic mice with HER2 mice stimulated HER2-induced tumor growth and rendered resistance to Hsp90 disruption. The present study indicates that SNCG protects Hsp90 client protein of HER2, and renders resistance to Hsp90 disruption.

Use of NQO1 status as a selective biomarker for oesophageal squamous cell carcinomas with greater sensitivity to 17-AAG

Background

Oesophageal squamous cell carcinoma (OSCC) is a major health burden in Sub-Saharan Africa, and novel chemotherapies are urgently required to combat this disease. The heat shock protein 90 (HSP90) inhibitor 17-N-allylamino-17-demethoxygeldanamycin (17-AAG) has previously been proposed as a possible candidate drug. NADPH quinone oxidoreductase 1 (NQO1) is known to increase the potency of 17-AAG, therefore we investigated the effects of 17-AAG in OSCC cell lines in the context of their NQO1 status.

Methods

We used MTT assays to compare the sensitivity of a panel of OSCC cell lines to 17-AAG. Western blotting, and RT-PCR were used to investigate NQO1 protein and mRNA levels, while an RFLP approach was used to investigate the NQO1 C609T SNP.

Results

Expression of NQO1 markedly increased sensitivity to 17-AAG in the OSCC cell lines, while normal fibroblasts, which expressed HSP90 at much lower levels, were more resistant to 17-AAG. In isolation, neither the C609T SNP, nor NQO1 mRNA levels was an accurate predictor of NQO1 protein levels.

Conclusions

Since NQO1 greatly enhances the anti-cancer effects of 17-AAG, this could be used as a selective marker for patients that would benefit most from 17-AAG chemotherapy at low doses. Testing for the presence of the C609T SNP in both alleles could be used as a screen to exclude potentially poor responders to 17-AAG treatment at low dosages.

A mutation in the catalytic loop of Hsp90 specifically impairs ATPase stimulation by Aha1p, but not Hch1p

Heat shock protein 90 (Hsp90) is a molecular chaperone that plays a central role in maintaining cellular homeostasis by facilitating activation of a large number of client proteins. ATP-dependent client activation by Hsp90 is tightly regulated by a host of co-chaperone proteins that control progression through the activation cycle. ATPase stimulation of Hsp90 by Aha1p requires a conserved RKxK motif that interacts with the catalytic loop of Hsp90. In this study, we explore the role of this RKxK motif in the biological and biochemical properties of Hch1p. We found that this motif is required for Hch1p-mediated ATPase stimulation in vitro, but mutations that block stimulation do not impair the action of Hch1p in vivo. This suggests that the biological function of Hch1p is not directly linked to ATPase stimulation. Moreover, a mutation in the catalytic loop of Hsp90 specifically impairs ATPase stimulation by Aha1p but not by Hch1p. Our work here suggests that both Hch1p and Aha1p regulate Hsp90 function through interaction with the catalytic loop but do so in different ways.

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

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

A purine scaffold HSP90 inhibitor BIIB021 has selective activity against KSHV-associated primary effusion lymphoma and blocks vFLIP K13-induced NF-κB

PURPOSE

Kaposi sarcoma-associated herpes virus (KSHV)-associated primary effusion lymphomas (PEL) have extremely poor prognosis when treated with conventional chemotherapy. KSHV-encoded viral FLICE-inhibitory protein (vFLIP) K13 binds to the IkappaB kinase (IKK) complex to constitutively activate the NF-κB pathway, which has been shown to be essential for the survival and proliferation of PEL cells. The molecular chaperone HSP90 is a component of the IKK complex and is required for its activity.

EXPERIMENTAL DESIGN

We have analyzed the effect of HSP90 inhibitors on the survival and proliferation of PEL cells and on the activity of the NF-κB pathway.

RESULTS

We show that BIIB021, a purine scaffold-based orally administrable HSP90 inhibitor, shows preferential cytotoxicity toward PEL cells as compared with non-PEL cells. The cytotoxic effect of BIIB021 against PEL was associated with induction of cell-cycle arrest and apoptosis. BIIB021 blocked the expression of a number of cellular proteins involved in the regulation of cell cycle and apoptosis. BIIB021 also blocked constitutive NF-κB activity present in PEL cells, in part, by blocking the interaction of vFLIP K13 with the IKK complex subunits. In a xenograft model of PEL, BIIB021 significantly reduced tumor growth.

CONCLUSION

BIIB021 blocks constitutive NF-κB activity in PEL and shows preferential antitumor activity against PEL in vitro and in vivo. BIIB021 may be a promising agent for treatment of PEL.

Targeted therapies for bone sarcomas

Bone sarcomas include a very large number of tumour subtypes, which originate form bone and more particularly from mesenchymal stem cell lineage. Osteosarcoma, Ewing's sarcoma and chondrosarcoma, the three main bone sarcoma entities develop in a favourable microenvironment composed by bone cells, blood vessels, immune cells, based on the 'seed and soil theory'. Current therapy associates surgery and chemotherapy, however, bone sarcomas remain diseases with high morbidity and mortality especially in children and adolescents. In the past decade, various new therapeutic approaches emerged and target the tumour niche or/and directly the tumour cells by acting on signalling/metabolic pathways involved in cell proliferation, apoptosis or drug resistance. The present review gives a brief overview from basic to clinical assessment of the main targeted therapies of bone sarcoma cells.

Aryl hydrocarbon receptor is a target of 17-Allylamino-17-demethoxygeldanamycin and enhances its anticancer activity in lung adenocarcinoma cells

We have demonstrated that aryl hydrocarbon receptor (AhR) is overexpressed in lung adenocarcinoma (AD). AhR is usually associated with heat shock protein 90 (Hsp90) in the cytoplasm. 17-Allylamino-17-demethoxygeldanamycin (17-AAG), an Hsp90 inhibitor, is currently under evaluation for its anticancer activity in clinical trials. Here we investigated whether AhR plays a role in 17-AAG-mediated anticancer activity by functioning as a downstream target or by modulating its anticancer efficacy. AhR expression in lung AD cells was modulated by siRNA interference or overexpression. Tumor growth was determined with colony formation in vitro or in vivo. Anticancer activity of 17-AAG was determined by measuring cell viability, cell cycle distribution, and expression of cell cycle regulators. Proteins and mRNA levels were examined by immunoblotting and the real-time reverse transcription-polymerase chain reaction, respectively. In this study, AhR overexpression positively modulated growth of lung AD cells, at least partially, via RelA-dependent mechanisms. Although treatment with 17-AAG reduced AhR levels and AhR-regulated gene expression in lung AD cells, AhR expression increased anticancer activity of 17-AAG. In addition, 17-AAG treatment reduced cell viability, CDK2, CDK4, cyclin E, cyclin D1, and phosphorylated Rb levels in AhR-expressing lung AD cells. NAD(P)H:quinone oxidoreductase (NQO1), which is regulated by AhR, was shown to increase anticancer activity of 17-AAG in cells. Knockdown of NQO1 expression attenuated the reduction of cell cycle regulators by 17-AAG treatment in AhR overexpressed cells. We demonstrated that AhR protein not only functions as a downstream target of 17-AAG, but also enhances anticancer activity of 17-AAG in lung AD cells.

Targeting β-tubulin:CCT-β complexes incurs Hsp90- and VCP-related protein degradation and induces ER stress-associated apoptosis by triggering capacitative Ca2+ entry, mitochondrial perturbation and caspase overactivation

We have previously demonstrated that interrupting the protein–protein interaction (PPI) of β-tubulin:chaperonin-containing TCP-1β (CCT-β) induces the selective killing of multidrug-resistant cancer cells due to CCT-β overexpression. However, the molecular mechanism has not yet been identified. In this study, we found that CCT-β interacts with a myriad of intracellular proteins involved in the cellular functions of the endoplasmic reticulum (ER), mitochondria, cytoskeleton, proteasome and apoptosome. Our data show that the targeted cells activate both the heat-shock protein 90 (Hsp90)-associated protein ubiquitination/degradation pathway to eliminate misfolded proteins in the cytoplasm and the valosin-containing protein (VCP)-centered ER-associated protein degradation pathway to reduce the excessive levels of unfolded polypeptides from the ER, thereby mitigating ER stress, at the onset of β-tubulin:CCT-β complex disruption. Once ER stress is expanded, ER stress-associated apoptotic signaling is enforced, as exhibited by cellular vacuolization and intracellular Ca²⁺ release. Furthermore, the elevated intracellular Ca²⁺ levels resulting from capacitative Ca²⁺ entry augments apoptotic signaling by provoking mitochondrial perturbation and caspase overactivation in the targeted cells. These findings not only provide a detailed picture of the apoptotic signaling cascades evoked by targeting the β-tubulin:CCT-β complex but also demonstrate a strategy to combat malignancies with chemoresistance to Hsp90- and VCP-related anticancer agents.