A rat retinal damage model predicts for potential clinical visual disturbances induced by Hsp90 inhibitors

Functional analysis of retinal-binding protein in the visual system of the nocturnal marine shellfish Pacific abalone (Haliotis discus hannai)

The Pacific abalone (Haliotis discus hannai) is a nocturnal species that inhabits marine benthic ecosystems, characterized by its aversion to light and preference for darkness during daylight hours, with movement and feeding predominantly occurring at night. However, the morphology and structure of its visual organs and the mechanisms underlying its perception of cyclical light variations are unknown. This study analyzed the Retinal-binding protein (RALBP) gene to elucidate its role in the abalone's visual system. Using the rapid amplification of cDNA ends technique, the RALBP gene was cloned, revealing an open reading frame (ORF) of 1188 bp encoding 396 amino acids. A recombinant expression vector was subsequently constructed to produce a recombinant protein with a molecular weight of 45.3 kDa. This purified recombinant protein was used as an antigen to generate a polyclonal antibody, with enzyme-linked immunosorbent assay (ELISA) results indicating an antibody potency of ≥512 K. Immunofluorescence assays demonstrated strong RALBP signals in the pigment epithelial and photoreceptor cell layers of the retina, with no detection in other retinal layers. To evaluate circadian expression patterns of RALBP under different light spectra, including full-spectrum natural light, short-wavelength blue light (450 nm), and long-wavelength orange light (560 nm), western blotting and the Cosinor program were utilized. The results revealed significant cosine rhythmic expression of RALBP under all light conditions (P < 0.05), with higher expression levels during the day compared to the night (P < 0.05). This is the first study that provides insights into the morphological and structural characteristics of the abalone retina and demonstrates that the abalone's ability to detect cyclical light changes is determined by the diurnal expression of RALBP. These findings establish a theoretical basis for understanding the evolution of visual organs and circadian regulation mechanisms in marine shellfish.

Traditional Chinese Medicine-Based Nanoformulations for Enhanced Photothermal Therapy of Cancer

Photothermal therapy (PTT) has shown promise in the ablation of small, unresectable tumors by boosting the tumor's temperature above 50 °C. However, the high local temperature-induced cancer cell necrosis could create severe local inflammation, which may deteriorate normal tissues and increase tumor spreading. Although mild photothermal therapy (MPTT) at 42-45 °C could avoid the undesired side effect to some extent with minimal nonspecific heat diffusion, the self-protective behavior of tumors during MPTT results in an unsatisfactory therapeutic effect. Inspired by the widespread applications of traditional Chinese medicine (TCM) in various ailments, we also extensively explored the use of TCM in PTT and MPTT. In this Review, we summarize the application and function of TCM in PTT and MPTT, including the following: (1) TCM improves the performance of PTT and MPTT by elevating the photothermal conversion ability of photothermal agents (PTAs) and overcoming the self-protective effect of tumors, (2) PTT enhances TCM-based chemotherapy by improving the sensitivity and cellular uptake of TCM in tumors, and (3) natural TCM and metal-chelated TCM-based nanoparticles could directly act as PTAs for carrier-free combination therapy. We expect this Review will further illuminate TCM's utility and applicability in cancer treatment and create new combination strategies for theragnostic use.

Assessment of Hsp90β-selective inhibitor safety and on-target effects

The heat shock protein 90 (Hsp90) family of molecular chaperones mediates the folding and activation of ~ 400 client proteins, many of which contribute to oncogenesis. As a result, Hsp90 pan-inhibitors, which inhibit all four Hsp90 isoforms, have been investigated in the clinic for the treatment of cancer. Unfortunately, detrimental side effects were observed and hindered the clinical development of pan-Hsp90 inhibitors. The two most common on-target toxicities, cardio-toxicity and ocular-toxicity, have been attributed to inhibition of the Hsp90α isoform. As an alternative strategy, Hsp90β-selective inhibitors have been developed, which have shown promising anti-cancer activity in vitro and in vivo in combination with immune-checkpoint blockade therapy. This study aims to assess the potential risks of cardio-toxicity and ocular-toxicity exhibited by Hsp90β-selective inhibitors in vitro. In summary, the Hsp90β-selective NDNB1182 was found to avoid the cardio- and ocular-toxicity typical of Hsp90 pan-inhibitors (e.g. 17-AAG), providing a promising path toward the generation of isoform-selective Hsp90 inhibitors.

A novel combination therapy targets sonic hedgehog signaling by the dual inhibition of HMG-CoA reductase and HSP90 in rats with non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH) is characterized by liver inflammation, fat accumulation, and collagen deposition. Due to the limited availability of effective treatments, there is a pressing need to develop innovative strategies. Given the complex nature of the disease, employing combination approaches is essential. Hedgehog signaling has been recognized as potentially promoting NASH, and cholesterol can influence this signaling by modifying the conformation of PTCH1 and SMO activity. HSP90 plays a role in the stability of SMO and GLI proteins. We revealed significant positive correlations between Hedgehog signaling proteins (Shh, SMO, GLI1, and GLI2) and both cholesterol and HSP90 levels. Herein, we investigated the novel combination of the cholesterol-lowering agent lovastatin and the HSP90 inhibitor PU-H71 in vitro and in vivo. The combination demonstrated a synergy score of 15.09 and an MSA score of 22.85, as estimated by the ZIP synergy model based on growth inhibition rates in HepG2 cells. In a NASH rat model induced by thioacetamide and a high-fat diet, this combination therapy extended survival, improved liver function and histology, and enhanced antioxidant defense. Additionally, the combination exhibited anti-inflammatory and anti-fibrotic potential by influencing the levels of TNF-α, TGF-β, TIMP-1, and PDGF-BB. This effect was evident in the suppression of the Col1a1 gene expression and the levels of hydroxyproline and α-SMA. These favorable outcomes may be attributed to the combination's potential to inhibit key Hedgehog signaling molecules. In conclusion, exploring the applicability of this combination contributes to a more comprehensive understanding and improved management of NASH and other fibrotic disorders.

Co-targeting HSP90 alpha and CDK7 overcomes resistance against HSP90 inhibitors in BCR-ABL1+ leukemia cells

HSP90 has emerged as an appealing anti-cancer target. However, HSP90 inhibitors (HSP90i) are characterized by limited clinical utility, primarily due to the resistance acquisition via heat shock response (HSR) induction. Understanding the roles of abundantly expressed cytosolic HSP90 isoforms (α and β) in sustaining malignant cells' growth and the mechanisms of resistance to HSP90i is crucial for exploiting their clinical potential. Utilizing multi-omics approaches, we identified that ablation of the HSP90β isoform induces the overexpression of HSP90α and extracellular-secreted HSP90α (eHSP90α). Notably, we found that the absence of HSP90α causes downregulation of PTPRC (or CD45) expression and restricts in vivo growth of BCR-ABL1+ leukemia cells. Subsequently, chronic long-term exposure to the clinically advanced HSP90i PU-H71 (Zelavespib) led to copy number gain and mutation (p.S164F) of the HSP90AA1 gene, and HSP90α overexpression. In contrast, acquired resistance toward other tested HSP90i (Tanespimycin and Coumermycin A1) was attained by MDR1 efflux pump overexpression. Remarkably, combined CDK7 and HSP90 inhibition display synergistic activity against therapy-resistant BCR-ABL1+ patient leukemia cells via blocking pro-survival HSR and HSP90α overexpression, providing a novel strategy to avoid the emergence of resistance against treatment with HSP90i alone.

STA9090 as a Potential Therapeutic Agent for Liver Fibrosis by Modulating the HSP90/TβRII/Proteasome Interplay: Novel Insights from In Vitro and In Vivo Investigations

Liver fibrosis is a progressive condition characterized by the build-up of fibrous tissue resulting from long-term liver injury. Although there have been advancements in research and treatment, there is still a need for effective antifibrotic medication. HSP90 plays a crucial role in the development of fibrosis. It acts as a molecular chaperone that assists in the proper folding and stability of TβRII, potentially regulating the signaling of TGF-β1. It has been established that TβRII can be degraded through the proteasome degradation system, either via ubiquitination-dependent or -independent pathways. In the present study, STA9090 demonstrated promising effects in both in vitro and in vivo models. It reduced LDH leakage, prolonged the survival rate of hepatocytes in rats with liver fibrosis, and improved liver function. Importantly, STA9090 exerted pleiotropic effects by targeting proteins involved in limiting collagen production, which resulted in improved microscopic features of the rat livers. Our findings suggest that STA9090-induced inhibition of HSP90 leads to the degradation of TβRII, a fibrogenic client protein of HSP90, through the activation of the 20S proteasomal degradation system. We also revealed that this degradation mechanism is not dependent on the autophagy-lysosomal pathway. Additionally, STA9090 was found to destabilize HIF-1α and facilitate its degradation, leading to the reduced transcription of VEGF. Moreover, STA9090's ability to deactivate the NFκB signaling pathway highlights its potential as an anti-inflammatory and antifibrotic agent. However, further research is necessary to fully elucidate the underlying mechanisms and fully capitalize on the therapeutic benefits of targeting HSP90 and associated pathways.

Ganetespib (STA-9090) augments sorafenib efficacy via necroptosis induction in hepatocellular carcinoma: Implications from preclinical data for a novel therapeutic approach

Sorafenib, a multikinase inhibitor, is a first-line treatment for advanced hepatocellular carcinoma, but its long-term effectiveness is limited by the emergence of resistance mechanisms. One such mechanism is the reduction of microvessel density and intratumoral hypoxia caused by prolonged sorafenib treatment. Our research has demonstrated that HSP90 plays a critical role in conferring resistance to sorafenib in HepG2 cells under hypoxic conditions and N-Nitrosodiethylamine-exposed mice as well. This occurs through the inhibition of necroptosis on the one hand and the stabilization of HIF-1α on the other hand. To augment the effects of sorafenib, we investigated the use of ganetespib, an HSP90 inhibitor. We found that ganetespib activated necroptosis and destabilized HIF-1α under hypoxia, thus enhancing the effectiveness of sorafenib. Additionally, we discovered that LAMP2 aids in the degradation of MLKL, which is the mediator of necroptosis, through the chaperone-mediated autophagy pathway. Interestingly, we observed a significant negative correlation between LAMP2 and MLKL. These effects resulted in a reduction in the number of surface nodules and liver index, indicating a regression in tumor production rates in mice with HCC. Furthermore, AFP levels decreased. Combining ganetespib with sorafenib showed a synergistic cytotoxic effect and resulted in the accumulation of p62 and inhibition of macroautophagy. These findings suggest that the combined therapy of ganetespib and sorafenib may offer a promising approach for the treatment of hepatocellular carcinoma by activating necroptosis, inhibiting macroautophagy, and exhibiting a potential antiangiogenic effect. Overall, continued research is critical to establish the full therapeutic potential of this combination therapy.

Chronic heat stress induces the expression of HSP genes in the retina of chickens (Gallus gallus)

Introduction: Chronic heat stress during summer is a major challenge imposed by global warming. Chickens are more sensitive to heat stress than mammals because they lack sweat glands. Thus, chickens are more susceptible to heat stress during summer than other seasons. Induction of heat shock protein (HSP) genes is one of the primary defense mechanisms against heat stress. Tissue-specific responses exhibited by different classes of HSPs upon exposure to heat stress have been reported previously in different tissues including the heart, kidney, intestine, blood, and muscle, but not in the retina. Therefore, this study aimed to investigate the expression levels of HSP27, HSP40, HSP60, HSP70, and HSP90 in the retina under chronic heat stress.

Methods: This study was conducted during the summers of 2020 and 2021 in Kuwait. Chickens (Gallus gallus) were divided into control and heat-treated groups and sacrificed at different developmental stages. Retinas were extracted and analyzed by using Real Time quantitative Polymerase Chain Reaction (RT-qPCR).

Results: Our results from the summer of 2021 were similar to that from the summer of 2020, regardless of whether GAPDH or RPL5 was used as a gene normalizer. All five HSP genes were upregulated in the retina of 21-day-old heat-treated chickens and stayed upregulated until 35 days of age, with the exception of HSP40, which was downregulated. The addition of two more developmental stages in the summer of 2021 showed that at 14 days, all HSP genes were upregulated in the retina of heat-treated chickens. In contrast, at 28 days, HSP27 and HSP40 were downregulated, whereas HSP60, HSP70, and HSP90 were upregulated. Furthermore, our results showed that under chronic heat stress, the highest upregulation of HSP genes was seen at the earliest developmental stages.

Discussion: To the best of our knowledge, this is the first study to report the expression levels of HSP27, HSP40, HSP60, HSP70, and HSP90 in the retina under chronic heat stress. Some of our results match the previously reported expression levels of some HSPs in other tissues under heat stress. These results suggest that HSP gene expression can be used as a biomarker for chronic heat stress in the retina.

The downregulation of HSP90-controlled CRALBP expression is associated with age-related vision attenuation

The dysfunction of CRALBP, a key regulator of the visual cycle, is associated with retinitis punctata albescens characterized by night vision loss and retinal degeneration. In this paper, we find that the expression of CRALBP is regulated by heat shock protein 90 (HSP90). Inhibition of HSP90α or HSP90β expression by using the CRISPR-Cas9 technology downregulates CRALBP's mRNA and protein expression in ARPE-19 cells by triggering the degradation of transcription factor SP1 in the ubiquitin-proteasome pathway. SP1 can bind to CRALBP's promoter, and inhibition of SP1 by its inhibitor plicamycin or siRNA downregulates CRALBP's mRNA expression. In the zebrafish, inhibition of HSP90 by the intraperitoneal injection of IPI504 reduces the thickness of the retinal outer nuclear layer and Rlbp1b mRNA expression. Interestingly, the expression of HSP90, SP1, and CRALBP is correlatedly downregulated in the senescent ARPE-19 and Pig primary RPE cells in vitro and in the aged zebrafish and mouse retinal tissues in vivo. The aged mice exhibit the low night adaption activity. Taken together, these data indicate that the HSP90-SP1 is a novel regulatory axis of CRALBP transcriptional expression in RPE cells. The age-mediated downregulation of the HSP90-SP1-CRALBP axis is a potential etiology for the night vision reduction in senior people.

The Role of Hsp90 in Retinal Proteostasis and Disease

Photoreceptors are sensitive neuronal cells with great metabolic demands, as they are responsible for carrying out visual phototransduction, a complex and multistep process that requires the exquisite coordination of a large number of signalling protein components. Therefore, the viability of photoreceptors relies on mechanisms that ensure a well-balanced and functional proteome that maintains the protein homeostasis, or proteostasis, of the cell. This review explores how the different isoforms of Hsp90, including the cytosolic Hsp90α/β, the mitochondrial TRAP1, and the ER-specific GRP94, are involved in the different proteostatic mechanisms of photoreceptors, and elaborates on Hsp90 function when retinal homeostasis is disturbed. In addition, several studies have shown that chemical manipulation of Hsp90 has significant consequences, both in healthy and degenerating retinae, and this can be partially attributed to the fact that Hsp90 interacts with important photoreceptor-associated client proteins. Here, the interaction of Hsp90 with the retina-specific client proteins PDE6 and GRK1 will be further discussed, providing additional insights for the role of Hsp90 in retinal disease.

TRAP1 in Oxidative Stress and Neurodegeneration

Tumor necrosis factor receptor-associated protein 1 (TRAP1), also known as heat shock protein 75 (HSP75), is a member of the heat shock protein 90 (HSP90) chaperone family that resides mainly in the mitochondria. As a mitochondrial molecular chaperone, TRAP1 supports protein folding and contributes to the maintenance of mitochondrial integrity even under cellular stress. TRAP1 is a cellular regulator of mitochondrial bioenergetics, redox homeostasis, oxidative stress-induced cell death, apoptosis, and unfolded protein response (UPR) in the endoplasmic reticulum (ER). TRAP1 has attracted increasing interest as a therapeutical target, with a special focus on the design of TRAP1 specific inhibitors. Although TRAP1 was extensively studied in the oncology field, its role in central nervous system cells, under physiological and pathological conditions, remains largely unknown. In this review, we will start by summarizing the biology of TRAP1, including its structure and related pathways. Thereafter, we will continue by debating the role of TRAP1 in the maintenance of redox homeostasis and protection against oxidative stress and apoptosis. The role of TRAP1 in neurodegenerative disorders will also be discussed. Finally, we will review the potential of TRAP1 inhibitors as neuroprotective drugs.

TAS-116 (pimitespib), a heat shock protein 90 inhibitor, shows efficacy in preclinical models of adult T-cell leukemia

Adult T‐cell leukemia/lymphoma (ATL) is a highly chemoresistant malignancy of peripheral T lymphocytes caused by human T‐cell leukemia virus type 1 infection, for which there is an urgent need for more effective therapeutic options. The molecular chaperone heat shock protein 90 (HSP90) plays a crucial role in nuclear factor‐κB (NF‐κB)‐mediated antiapoptosis in ATL cells, and HSP90 inhibitors are new candidate therapeutics for ATL. Accordingly, we investigated the anti‐ATL effects of a novel oral HSP90 inhibitor, TAS‐116 (pimitespib), and the mechanisms involved in ex vivo and in vivo preclinical models. TAS‐116 achieved IC₅₀ values of less than 0.5 μmol/L in 10 ATL‐related cell lines and less than 1 μmol/L in primary peripheral blood cells of nine ATL patients; no toxicity was observed toward CD4⁺ lymphocytes from healthy donors, indicating the safety of this agent. Given orally, TAS‐116 also showed significant inhibitory effects against tumor cell growth in ATL cell‐xenografted mice. Furthermore, gene expression profiling of TAS‐116‐treated Tax‐positive or ‐negative cell lines and primary ATL cells using DNA microarray and multiple pathway analysis revealed the significant downregulation of the NF‐κB pathway in Tax‐positive cells and cell‐cycle arrest in Tax‐negative cells and primary ATL cells. TAS‐116 suppressed the activator protein‐1 and tumor necrosis factor pathways in all examined cells. These findings strongly indicate the efficacy of TAS‐116, regardless of the stage of ATL progression, and its potential application as a novel clinical anti‐ATL therapeutic agent.

The Role of HSP70 in the Protective Effects of NVP-AUY922 on Multiple Organ Dysfunction Syndrome in Endotoxemic Rats

Sepsis is defined as a life-threatening organ dysfunction syndrome with high morbidity and mortality caused by bacterial infection. The major characteristics of sepsis are systemic inflammatory responses accompanied with elevated oxidative stress, leading to multiple organ dysfunction syndrome (MODS), and disseminated intravascular coagulation (DIC). As a molecular chaperon to repair unfolded proteins, heat shock protein 70 (HSP70) maintains cellular homeostasis and shows protective effects on inflammatory damage. HSP 90 inhibitors were reported to exert anti-inflammatory effects via activation of the heat shock factor-1 (HSF-1), leading to induction of HSP70. We evaluated the beneficial effect of HSP 90 inhibitor NVP-AUY 922 (NVP) on multiple organ dysfunction syndrome induced by lipopolysaccharide (LPS) and further explored the underlying mechanism. NVP (5 mg/kg, i.p.) was administered 20 h prior to LPS initiation (LPS 30 mg/kg, i.v. infusion for 4 h) in male Wistar rats. Results demonstrated that pretreatment with NVP significantly increased survival rate and prevented hypotension at 6 h after LPS injection. Plasma levels of ALT, CRE and LDH as well as IL-1β and TNF-α were significantly reduced by NVP at 6 h after LPS challenge. The induction of inducible NO synthase in the liver, lung and heart and NF-κB p-p65 and caspase 3 protein expression in the heart were also attenuated by NVP. In addition, NVP markedly induced HSP70 and HO-1 proteins in the liver, lung and heart after LPS injection. These results indicated that NVP possessed the anti-inflammatory and antioxidant effects on LPS-induced acute inflammation, which might be associated with HSP70 and HO-1, leading to prevent MODS in sepsis. NVP might be considered as a novel therapeutic strategy in the prevention of sepsis-induced MODS.

The molecular chaperone Hsp90 maintains Golgi organization and vesicular trafficking by regulating microtubule stability

Hsp90 is an abundant and special molecular chaperone considered to be the regulator of many transcription factors and signaling kinases. Its high abundance is indicative of its involvement in some more fundamental processes. In this study, we provide evidence that Hsp90 is required for microtubule stabilization, Golgi organization, and vesicular trafficking. We showed that Hsp90 is bound to microtubule-associated protein 4 (MAP4), which is essential for maintaining microtubule acetylation and stabilization. Hsp90 depletion led to the decrease in MAP4, causing microtubule deacetylation and destabilization. Furthermore, in Hsp90-depleted cells, the Golgi apparatus was fragmented and anterograde vesicle trafficking was impaired, with phenotypes similar to those induced by silencing MAP4. These disruptive effects of Hsp90 depletion could be rescued by the expression of exogenous MAP4 or the treatment of trichostatin A that increases microtubule acetylation as well as stability. Thus, microtubule stability is an essential cellular event regulated by Hsp90.

National Institute on Aging Workshop: Repurposing Drugs or Dietary Supplements for Their Senolytic or Senomorphic Effects: Considerations for Clinical Trials

BACKGROUND

Cell senescence is implicated in numerous age-related conditions. Drugs and nutritional supplements developed for a variety of purposes kill senescent cells (senolytics) or suppress their secretions (senomorphics). There is interest in repurposing such drugs to treat or prevent age-related diseases. To date, only small-scale preliminary trials have been conducted.

METHOD

At a workshop convened by the National Institute on Aging in August 2019, academic, industry, and government scientists reviewed issues for phase II trials of potentially repurposable drugs, or dietary supplements, to assess benefits and risks of their senolytic (killing senescent cells) or senomorphic (altering senescent cells' phenotypes) effects in treating or preventing age-related conditions.

RESULTS

Participants reviewed mechanisms and effects of cellular senescence, senolytics, and senomorphics of several classes and their potential role in treating or preventing disease, modulators of the senescence-associated secretory phenotype, needs for senescence markers, data and specimen resources, infrastructure for planning trials, and potential effects on outcomes in older patients with multimorbidity and polypharmacy.

CONCLUSIONS

Participants noted the importance of considering potential effects of candidate drugs on multiple aging outcomes. It is important to assess drugs' specificity for killing senescent cells and the balance between senolytic and cytotoxic effects. Markers of specific senescent cell types are needed to assess intervention responses. There are potential interactions with coexisting diseases and their treatments in older persons. Standardized measures could enhance comparisons and pooling of data. Additional characterization of human cell senescent phenotypes is needed for developing better and more specific senolytics and senomorphics.

A novel dual HDAC and HSP90 inhibitor, MPT0G449, downregulates oncogenic pathways in human acute leukemia in vitro and in vivo

Acute leukemia is a highly heterogeneous disease; therefore, combination therapy is commonly used for patient treatment. Drug–drug interaction is a major concern of combined therapy; hence, dual/multi-target inhibitors have become a dominant approach for cancer drug development. HDACs and HSP90 are involved in the activation of various oncogenic signaling pathways, including PI3K/AKT/mTOR, JAK/STAT, and RAF/MEK/ERK, which are also highly enriched in acute leukemia gene expression profiles. Therefore, we suggest that dual HDAC and HSP90 inhibitors could represent a novel therapeutic approach for acute leukemia. MPT0G449 is a dual effect inhibitor, and it showed cytotoxic effectiveness in acute leukemia cells. Molecular docking analysis indicated that MPT0G449 possessed dual HDAC and HSP90 inhibitory abilities. Furthermore, MPT0G449 induced G₂ arrest and caspase-mediated cell apoptosis in acute leukemia cells. The oncogenic signaling molecules AKT, mTOR, STAT3, STAT5, MEK, and ERK were significantly downregulated after MPT0G449 treatment in HL-60 and MOLT-4 cells. In vivo xenograft models confirmed the antitumor activity and showed the upregulation of acetyl-histone H3 and HSP70, biomarkers of pan-HDAC and HSP90 inhibition, with MPT0G449 treatment. These findings suggest that the dual inhibition of HDAC and HSP90 can suppress the expression of oncogenic pathways in acute leukemia, and MPT0G449 represents a novel therapeutic for anticancer treatment.

The molecular chaperone Hsp90α deficiency causes retinal degeneration by disrupting Golgi organization and vesicle transportation in photoreceptors

Heat shock protein 90 (Hsp90) is an abundant molecular chaperone with two isoforms, Hsp90α and Hsp90β. Hsp90β deficiency causes embryonic lethality, whereas Hsp90α deficiency causes few abnormities except male sterility. In this paper, we reported that Hsp90α was exclusively expressed in the retina, testis, and brain. Its deficiency caused retinitis pigmentosa (RP), a disease leading to blindness. In Hsp90α-deficient mice, the retina was deteriorated and the outer segment of photoreceptor was deformed. Immunofluorescence staining and electron microscopic analysis revealed disintegrated Golgi and aberrant intersegmental vesicle transportation in Hsp90α-deficient photoreceptors. Proteomic analysis identified microtubule-associated protein 1B (MAP1B) as an Hsp90α-associated protein in photoreceptors. Hspα deficiency increased degradation of MAP1B by inducing its ubiquitination, causing α-tubulin deacetylation and microtubule destabilization. Furthermore, the treatment of wild-type mice with 17-DMAG, an Hsp90 inhibitor of geldanamycin derivative, induced the same retinal degeneration as Hsp90α deficiency. Taken together, the microtubule destabilization could be the underlying reason for Hsp90α deficiency-induced RP.

Human embryonic stem cell-derived extracellular vesicles alleviate retinal degeneration by upregulating Oct4 to promote retinal Müller cell retrodifferentiation via HSP90

Objective

Retinal degenerative diseases remain the dominant causes of blindness worldwide, and cell replacement is viewed as a promising therapeutic direction. However, the resources of seed cells are hard to obtain. To further explore this therapeutic approach, human embryonic stem extracellular vesicles (hESEVs) were extracted from human embryonic stem cells (hESCs) to inspect its effect and the possible mechanism on retinal Müller cells and retinal function.

Methods

hESEVs were extracted by multi-step differential centrifugation, whose morphologies and specific biomarkers (TSG101, CD9, CD63, and CD81) were observed and measured. After hESEVs were injected into the vitreous cavity of RCS rats, the retinal tissues and retinal functions of rats were assessed. The alteration of Müller cells and retinal progenitor cells was also recorded. Microvesicles (MVs) or exosomes (EXOs) were extracted from hESCs transfected with sh-HSP90 or pcDNA3.1-HSP9, and then incubated with Müller cells to measure the uptake of EVs, MVs, or EXOs in Müller cells by immunofluorescence. The retrodifferentiation of Müller cells was determined by measuring Vimentin and CHX10. qRT-PCR and western blot were used to detect HSP90 expression in MVs and evaluate Oct4 level in Müller cells, and Co-IP to inspect the interaction of HSP90 and Oct4.

Results

RCS rats at the postnatal 30 days had increased retinal progenitor cells which were dedifferentiated from Müller cells. hESEVs were successfully extracted from hESCs, evidenced by morphology observation and positive expressions of specific biomarkers (TSG101, CD9, CD63, and CD81). hESEVs promoted Müller cells dedifferentiated and retrodifferentiated into retinal progenitor cells evidenced by the existence of a large amount of CHX10-positive cells in the retinal inner layer of RCS rats in response to hESEV injection. The promotive role of hESEVs was exerted by MVs demonstrated by elevated fluorescence intensity of CHX10 and suppressed Vimentin fluorescence intensity in MVs rather than in EXOs. HSP90 in MVs inhibited the retrodifferentiation of Müller cells and suppressed the expression level of Oct4 in Müller cells. Co-IP revealed that HSP90 can target Oct4 in Müller cells.

Conclusion

hESEVs could promote the retrodifferentiation of Müller cells into retinal progenitor cells by regulating the expression of Oct4 in Müller cells by HSP90 mediation in MVs.

Sulfoxythiocarbamate S-4 inhibits HSP90 in human cutaneous squamous cell carcinoma cells

Cancer cells rely heavily on molecular chaperones, such as heat shock protein 90 (HSP90), and their co-chaperones. The development of HSP90 inhibitors is an attractive therapeutic approach that has the potential to affect multiple hallmarks of cancer. Such approach is particularly needed for tumors that carry large mutational burdens, including cutaneous squamous cell carcinomas (cSCC). We previously identified sulfoxythiocarbamate S-4 as an HSP90 inhibitor. In this study, we investigated the mechanism(s) by which S-4 compromises the viability of human cSCC cells. S-4 inhibits HSP90 and causes depletion of its clients HER2, a tyrosine kinase oncoprotein, and Bcl-2, an anti-apoptotic protein. The decrease in Bcl-2 is accompanied by cytochrome c release from mitochondria into the cytoplasm, suggesting apoptosis. In the surviving cells, depletion of the HSP90 clients cyclin D and CDK4 by S-4 prevents phosphorylation of the retinoblastoma protein Rb and the release of transcription factor E2F, inhibiting G1-S cell cycle progression and cell division. These findings illustrate the comprehensive effectiveness of S-4 and encourage future development of compounds of this type for cancer prevention and treatment.

Phase 1 study of the HSP90 inhibitor onalespib in combination with AT7519, a pan-CDK inhibitor, in patients with advanced solid tumors

PURPOSE

We conducted a phase 1 trial of the HSP90 inhibitor onalespib in combination with the CDK inhibitor AT7519, in patients with advanced solid tumors to determine the safety profile and maximally tolerated dose, pharmacokinetics, preliminary antitumor activity, and to assess the pharmacodynamic (PD) effects on HSP70 expression in patient-derived PBMCs and plasma.

METHODS

This study followed a 3 + 3 trial design with 1 week of intravenous (IV) onalespib alone, followed by onalespib/AT7519 (IV) on days 1, 4, 8, and 11 of a 21-days cycle. PK and PD samples were collected at baseline, after onalespib alone, and following combination therapy.

RESULTS

Twenty-eight patients were treated with the demonstration of downstream target engagement of HSP70 expression in plasma and PBMCs. The maximally tolerated dose was onalespib 80 mg/m² IV + AT7519 21 mg/m² IV. Most common drug-related adverse events included Grade 1/2 diarrhea (79%), fatigue (54%), mucositis (57%), nausea (46%), and vomiting (50%). Partial responses were seen in a palate adenocarcinoma and Sertoli-Leydig tumor; a colorectal and an endometrial cancer patient both remained on study for ten cycles with stable disease as the best response. There were no clinically relevant PK interactions for either drug.

CONCLUSIONS

Combined onalespib and AT7519 is tolerable, though below monotherapy RP2D. Promising preliminary clinical activity was seen. Further benefit may be seen with the incorporation of molecular signature pre-selection. Further biomarker development will require the assessment of the on-target impact on relevant client proteins in tumor tissue.

Natural heat shock protein 90 inhibitors in cancer and inflammation

Heat shock protein (HSP)90 is the most abundant HSPs, which are chaperone molecules whose major roles are cell protection and maintenance by means of aiding the folding, the stabilization and the remodeling of a wide range of proteins. A few hundreds of proteins depend on HSP90 chaperone activity, including kinases and transcriptional factors that play essential roles in cancer and inflammation, so that HSP90-targeted therapies have been considered as a potential strategy for the treatment of cancer and inflammatory-associated diseases. HSP90 inhibition by natural, semi-synthetic and synthetic compounds have yield promising results in pre-clinical studies and clinical trials for different types of cancers and inflammation. Natural products are a huge source of biologically active compounds widely used in drug development due to the great diversity of their metabolites which are capable to modulate several protein functions. HSP90 inhibitors have been isolated from bacteria, fungi and vegetal species. These natural compounds have a noteworthy ability to modulate HSP90 activity as well as serve as scaffolds for the development of novel synthetic or semi-synthetic inhibitors. Over a hundred clinical trials have evaluated the effect of HSP90 inhibitors as adjuvant treatment against different types of tumors and, currently, new studies are being developed to gain sight on novel promising and more effective approaches for cancer treatment. In this review, we present the naturally occurring HSP90 inhibitors and analogues, discussing their anti-cancer and anti-inflammatory effects.

Part I of GANNET53: A European Multicenter Phase I/II Trial of the Hsp90 Inhibitor Ganetespib Combined With Weekly Paclitaxel in Women With High-Grade, Platinum-Resistant Epithelial Ovarian Cancer-A Study of the GANNET53 Consortium

Background: Stabilized mutant p53 protein (mutp53) is a novel target in epithelial ovarian cancer. Due to aberrant conformation, mutp53 proteins depend on folding support by the Hsp90 chaperone. Hsp90 blockade induces degradation of mutp53, resulting in tumor cell cytotoxicity and increased sensitivity to chemotherapeutics. Preclinical synergy of the Hsp90 inhibitor ganetespib combined with paclitaxel provided the rationale for testing the combination in platinum-resistant ovarian cancer (PROC) patients in the GANNET53 trial (NCT02012192). Methods: Eligible patients had high-grade PROC with ≤ 4 prior lines of chemotherapy. Weekly paclitaxel (80 mg/m²) and increasing doses of ganetespib (100, 150 mg/m²) were given i.v. on days 1, 8, 15 in a 28 days cycle until disease progression or unacceptable toxicity. Endpoints were safety and determination of phase II dose. Dose limiting toxicity (DLT) was defined as grade 4 toxicity (with exceptions) occurring in cycles 1&2. Results: Ten patients (median age 59 years; range 43-70) were enrolled. No DLT occurred in cohort 1 (4 patients treated with paclitaxel + ganetespib 100 mg/m²), nor in cohorts 2 and 3 (6 patients treated with paclitaxel + ganetespib 150 mg/m²). The most common adverse event (AE) related to ganetespib was transient grade 1/2 diarrhea (n = 6). Related grade 1/2 AEs in >2 patients included QTc prolongation (n = 4), nausea (n = 3), anemia (n = 3), headache (n = 3), fatigue (n = 3), and dyspnoea (n = 3). Most frequently related grade 3/4 AEs were diarrhea (n = 3) and neutropenia (n = 2). There was 1 death on study due to hemorrhage from a duodenal ulcer. Three patients discontinued study treatment due to serious AEs (digestive hemorrhage n = 1, cardiac failure n = 1, abdominal pain and vomiting n = 1), 6 due to progressive disease, one due to investigator and patient decision. Two patients achieved a partial response (ORR 20%) and 4 patients a stable disease (disease control rate of 60%). Median PFS was 2.9 months (1.6 months in cohort 1 at 100 mg/m² ganetespib, 5.1 months in cohorts 2+3 at 150 mg/m² ganetespib). Conclusions: The combination of ganetespib 150 mg/m² with paclitaxel 80 mg/m² once weekly for 3 out of 4 weeks was generally well-tolerated with no DLTs, and therefore chosen for the randomized phase II trial.

Balancing the Photoreceptor Proteome: Proteostasis Network Therapeutics for Inherited Retinal Disease

The light sensing outer segments of photoreceptors (PRs) are renewed every ten days due to their high photoactivity, especially of the cones during daytime vision. This demands a tremendous amount of energy, as well as a high turnover of their main biosynthetic compounds, membranes, and proteins. Therefore, a refined proteostasis network (PN), regulating the protein balance, is crucial for PR viability. In many inherited retinal diseases (IRDs) this balance is disrupted leading to protein accumulation in the inner segment and eventually the death of PRs. Various studies have been focusing on therapeutically targeting the different branches of the PR PN to restore the protein balance and ultimately to treat inherited blindness. This review first describes the different branches of the PN in detail. Subsequently, insights are provided on how therapeutic compounds directed against the different PN branches might slow down or even arrest the appalling, progressive blinding conditions. These insights are supported by findings of PN modulators in other research disciplines.

Chemical proteasome inhibition as a novel animal model of inner retinal degeneration in rats

Chemical proteasome inhibition has been a valuable animal model of neurodegeneration to uncover roles for the ubiquitin-proteasome system in the central nervous system. However, little is known about the effects of chemical proteasome inhibitors on retinal integrity. Therefore, we characterized the effects of structurally different chemical proteasome inhibitors on the retinal morphology and the mechanisms of their action in the normal adult rat eyes. Intravitreal injection of MG-262 and other proteasome inhibitors led to inner retinal degeneration. MG-262-induced inner retinal degeneration was accompanied by reduced proteasome activity, increased poly-ubiquitinated protein levels, and increased positive immunostaining of ubiquitin, 20S proteasome subunit and GADD153/CHOP in the retina. Its retinal degenerative effect was also associated with reduced retinal neurofilament light chain gene expression, reflecting retinal ganglion cell death. MG-262-induced neurofilament light chain downregulation was largely resistant to pharmacological modulation including endoplasmic reticulum stress, apoptosis or MAP kinase inhibitors. Thus, this study provides further evidence of roles for the ubiquitin-proteasome system in the maintenance of the retinal structural integrity. Chemical proteasome inhibition may be used as a novel animal model of inner retinal degeneration, including retinal ganglion cell loss, which warrants further analysis of the molecular mechanisms underlying its retinal degenerative effect.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

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

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.

Chaperome heterogeneity and its implications for cancer study and treatment

The chaperome is the collection of proteins in the cell that carry out molecular chaperoning functions. Changes in the interaction strength between chaperome proteins lead to an assembly that is functionally and structurally distinct from each constituent member. In this review, we discuss the epichaperome, the cellular network that forms when the chaperome components of distinct chaperome machineries come together as stable, functionally integrated, multimeric complexes. In tumors, maintenance of the epichaperome network is vital for tumor survival, rendering them vulnerable to therapeutic interventions that target critical epichaperome network components. We discuss how the epichaperome empowers an approach for precision medicine cancer trials where a new target, biomarker, and relevant drug candidates can be correlated and integrated. We introduce chemical biology methods to investigate the heterogeneity of the chaperome in a given cellular context. Lastly, we discuss how ligand-protein binding kinetics are more appropriate than equilibrium binding parameters to characterize and unravel chaperome targeting in cancer and to gauge the selectivity of ligands for specific tumor-associated chaperome pools.

Discovery of a Potent Grp94 Selective Inhibitor with Anti-Inflammatory Efficacy in a Mouse Model of Ulcerative Colitis

As the endoplasmic reticulum paralogue of Hsp90, Grp94 chaperones a small set of client proteins associated with some diseases, including cancer, primary open-angle glaucoma, and inflammatory disorders. Grp94-selective inhibition has been a potential therapeutic strategy for these diseases. In this study, inspired by the conclusion that ligand-induced "Phe199 shift" effect is the structural basis of Grp94-selective inhibition, a series of novel Grp94 selective inhibitors incorporating "benzamide" moiety were developed, among which compound 54 manifested the most potent Grp94 inhibitory activity with an IC₅₀ value of 2 nM and over 1000-fold selectivity to Grp94 against Hsp90α. In a DSS-induced mouse model of ulcerative colitis (UC), compound 54 exhibited significant anti-inflammatory efficacy. This work provides a potent Grp94 selective inhibitor as probe compound for the biological study of Grp94 and represents the first study that confirms the potential therapeutic efficacy of Grp94-selective inhibitors against UC.

Adapting to stress - chaperome networks in cancer

In this Opinion article, we aim to address how cells adapt to stress and the repercussions chronic stress has on cellular function. We consider acute and chronic stress-induced changes at the cellular level, with a focus on a regulator of cellular stress, the chaperome, which is a protein assembly that encompasses molecular chaperones, co-chaperones and other co-factors. We discuss how the chaperome takes on distinct functions under conditions of stress that are executed in ways that differ from the one-on-one cyclic, dynamic functions exhibited by distinct molecular chaperones. We argue that through the formation of multimeric stable chaperome complexes, a state of chaperome hyperconnectivity, or networking, is gained. The role of these chaperome networks is to act as multimolecular scaffolds, a particularly important function in cancer, where they increase the efficacy and functional diversity of several cellular processes. We predict that these concepts will change how we develop and implement drugs targeting the chaperome to treat cancer.

Model System Identifies Kinetic Driver of Hsp90 Inhibitor Activity against African Trypanosomes and Plasmodium falciparum

Hsp90 inhibitors, well studied in the laboratory and clinic for antitumor indications, have promising activity against protozoan pathogens, including Trypanosoma brucei which causes African sleeping sickness, and the malaria parasite, Plasmodium falciparum To progress these experimental drugs toward clinical use, we adapted an in vitro dynamic hollow-fiber system and deployed artificial pharmacokinetics to discover the driver of their activity: either concentration or time. The activities of compounds from three major classes of Hsp90 inhibitors in development were evaluated against trypanosomes. In all circumstances, the activities of the tested Hsp90 inhibitors were concentration driven. By optimally deploying the drug to match its kinetic driver, the efficacy of a given dose was improved up to 5-fold, and maximal efficacy was achieved with a significantly lower drug exposure. The superiority of concentration-driven regimens was evident in vitro over several logs of drug exposure and was predictive of efficacy in a mouse model of African trypanosomiasis. In studies with P. falciparum, antimalarial activity was similarly concentration driven. This experimental strategy offers an expedient and versatile translational tool to assess the impact of pharmacokinetics on antiprotozoal activity. Knowing kinetic governance early in drug development provides an additional metric for judging lead compounds and allows the incisive design of animal efficacy studies.

Targeting HSP90 dimerization via the C terminus is effective in imatinib-resistant CML and lacks the heat shock response

Heat shock protein 90 (HSP90) stabilizes many client proteins, including the BCR-ABL1 oncoprotein. BCR-ABL1 is the hallmark of chronic myeloid leukemia (CML) in which treatment-free remission (TFR) is limited, with clinical and economic consequences. Thus, there is an urgent need for novel therapeutics that synergize with current treatment approaches. Several inhibitors targeting the N-terminal domain of HSP90 are under investigation, but side effects such as induction of the heat shock response (HSR) and toxicity have so far precluded their US Food and Drug Administration approval. We have developed a novel inhibitor (aminoxyrone [AX]) of HSP90 function by targeting HSP90 dimerization via the C-terminal domain. This was achieved by structure-based molecular design, chemical synthesis, and functional preclinical in vitro and in vivo validation using CML cell lines and patient-derived CML cells. AX is a promising potential candidate that induces apoptosis in the leukemic stem cell fraction (CD34+CD38-) as well as the leukemic bulk (CD34+CD38+) of primary CML and in tyrosine kinase inhibitor (TKI)-resistant cells. Furthermore, BCR-ABL1 oncoprotein and related pro-oncogenic cellular responses are downregulated, and targeting the HSP90 C terminus by AX does not induce the HSR in vitro and in vivo. We also probed the potential of AX in other therapy-refractory leukemias. Therefore, AX is the first peptidomimetic C-terminal HSP90 inhibitor with the potential to increase TFR in TKI-sensitive and refractory CML patients and also offers a novel therapeutic option for patients with other types of therapy-refractory leukemia because of its low toxicity profile and lack of HSR.

Delivery of HSP90 Inhibitor Using Water Soluble Polymeric Conjugates with High Drug Payload

PURPOSE

HSP90 (Heat shock protein 90kD) has been validated as a therapeutic target in Castrate Resistant Prostate Cancer. Unfortunately, HSP90 inhibitors suffer from dose-limiting toxicities that hinder their clinical applications. Previously developed polymeric delivery systems for HSP90 inhibitors had either low drug content or low biological activity suggesting the need for better delivery system for HSP90 inhibitors.

METHODS

We developed a simplified synthetic strategy to prepare polyethylene glycol based water-soluble polymeric system for model HSP90 inhibitor geldanamycin (GDM). We then investigated the effect of cathepsin B degradable linker and drug content in polymeric conjugates on their growth inhibitory property using DU145 (androgen independent) and LNCaP (androgen dependent) cell lines.

RESULTS

Water-soluble polymeric conjugates were synthesized with GDM content ranging from 9 to 30% wt/wt. We demonstrated the importance of cathepsin B degradable linker from the context of drug content and different prostate cancer cell lines. The most active conjugate against DU145 cells exhibited IC₅₀ value of 2.9 μM. This was similar to the IC₅₀ (2.1 μM) of small molecular drug aminohexane geldanamycin.

CONCLUSION

Water-soluble polymeric conjugate with high drug content was synthesized that exhibited in-vitro growth inhibitory activity similar to small molecular weight HSP90 inhibitor. Graphical Abstract Water soluble degradable polymeric conjugate for the delivery of Geldanamycin.

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

Background:

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

Methods:

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

Results:

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

Conclusions:

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

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

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

Hyperthermia enhances 17-DMAG efficacy in hepatocellular carcinoma cells with aggravated DNA damage and impaired G2/M transition

Due to the lack of effective treatment, hepatocellular carcinoma (HCC) is one of the malignancies with low survival rates worldwide. Combination of hyperthermia and chemotherapy has shown promising results in several abdominal tumours, but high expression of HSP90 in tumours attenuated the efficacy of hyperthermia. Thus a combination of hyperthermia and inhibition of HSP90 might be a feasible therapeutic strategy for HCC. One hepatic cell line (L02) and two HCC cell lines (Huh7 and HepG2) were heated at 42 °C for 0, 0.5 or 4 h with or without 100 nM 17-dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG). HCC cells of the combination group exhibited more G2/M arrest and higher apoptotic rates which might result from suffering from more reactive oxygen species and serious DNA damage. Heat shock/17-DMAG co-treatment of HCC cells also destabilized CDK1, Cyclin B1 and CDC25C with a concomitant decreased proportion of cells in the M phase. Furthermore, co-treatment impaired the interaction of HSP90α with CDC37 and with CDK1, accompanied with decreased soluble CDK1. Combination of 17-DMAG with a 1.5-h whole body hyperthermia treatment attenuated tumour growth in xenograft mice models. These results suggest hyperthermia sensitize HCC to 17-DMAG, and combination of hyperthermia with 17-DMAG might be a potential therapeutic strategy for HCC.

The central role of heat shock factor 1 in synaptic fidelity and memory consolidation

Networks of neuronal synapses are the fundamental basis for making and retaining memory. Reduced synapse number and quality correlates with loss of memory in dementia. Heat shock factor 1 (HSF1), the major transcription factor regulating expression of heat shock genes, plays a central role in proteostasis, in establishing and sustaining synaptic fidelity and function, and in memory consolidation. Support for this thesis is based on these observations: (1) heat shock induces improvements in synapse integrity and memory consolidation; (2) synaptic depolarization activates HSF1; (3) activation of HSF1 alone (independent of the canonical heat shock response) augments formation of essential synaptic elements-neuroligands, vesicle transport, synaptic scaffolding proteins, lipid rafts, synaptic spines, and axodendritic synapses; (4) HSF1 coalesces and activates memory receptors in the post-synaptic dendritic spine; (5) huntingtin or α-synuclein accumulation lowers HSF1 while HSF1 lowers huntingtin and α-synuclein aggregation-a potential vicious cycle; and (6) HSF1 agonists (including physical activity) can improve cognitive function in dementia models. Thus, via direct gene expression of synaptic elements, production of HSPs that assure high protein fidelity, and activation of other neuroprotective signaling pathways, HSF1 agonists could provide breakthrough therapy for dementia-associated disease.

Hsp90 Inhibitor Ganetespib Sensitizes Non-Small Cell Lung Cancer to Radiation but Has Variable Effects with Chemoradiation

PURPOSE

HSP90 inhibition is well known to sensitize cancer cells to radiation. However, it is currently unknown whether additional radiosensitization could occur in the more clinically relevant setting of chemoradiation (CRT). We used the potent HSP90 inhibitor ganetespib to determine whether it can enhance CRT effects in NSCLC.

EXPERIMENTAL DESIGN

We first performed in vitro experiments in various NSCLC cell lines combining radiation with or without ganetespib. Some of these experiments included clonogenic survival assay, DNA damage repair, and cell-cycle analysis, and reverse-phase protein array. We then determined whether chemotherapy affected ganetespib radiosensitization by adding carboplatin-paclitaxel to some of the in vitro and in vivo xenograft experiments.

RESULTS

Ganetespib significantly reduced radiation clonogenic survival in a number of lung cancer cell lines, and attenuated DNA damage repair with irradiation. Radiation caused G₂-M arrest that was greatly accentuated by ganetespib. Ganetespib with radiation also dose-dependently upregulated p21 and downregulated pRb levels that were not apparent with either drug or radiation alone. However, when carboplatin-paclitaxel was added, ganetespib was only able to radiosensitize some cell lines but not others. This variable in vitro CRT effect was confirmed in vivo using xenograft models.

CONCLUSIONS

Ganetespib was able to potently sensitize a number of NSCLC cell lines to radiation but has variable effects when added to platinum-based doublet CRT. For optimal clinical translation, our data emphasize the importance of preclinical testing of drugs in the context of clinically relevant therapy combinations. Clin Cancer Res; 22(23); 5876-86. ©2016 AACR.

Phase 1B/2 study of the HSP90 inhibitor AUY922 plus trastuzumab in metastatic HER2-positive breast cancer patients who have progressed on trastuzumab-based regimen

This open-label, multicenter, phase 1B/2 trial assessed AUY922 plus trastuzumab in patients with locally advanced or metastatic HER2-positive breast cancer previously treated with chemotherapy and anti-HER2 therapy. This study was composed of a dose-escalation part with AUY922 administered weekly at escalating doses with trastuzumab 2 mg/kg/week (phase 1B), followed by a phase 2 part using the same regimen at recommended phase 2 dose (RP2D). The primary objectives were to determine the maximum tolerated dose (MTD) and/or RP2D (phase 1B), and to evaluate preliminary antitumor activity (phase 2) of AUY922 plus trastuzumab at MTD/RP2D. Forty-five patients were treated with AUY922 plus trastuzumab (4 in phase 1B with AUY922 at 55 mg/m2 and 41 in phase 1B/2 with AUY922 at 70 mg/m2 [7 in phase 1B and 34 in phase 2]). One patient in phase 1B (70 mg/m2) experienced a dose-limiting toxicity (grade 3 diarrhea); the RP2D was weekly AUY922 70 mg/m2 plus trastuzumab. Of the 41 patients in the 70 mg/m2 cohort, the overall response rate (complete or partial responses) was 22.0% and 48.8% patients had stable disease. Study treatment-related adverse events occurred in 97.8% of patients; of these, 31.1% were grade 3 or 4. Forty-one patients (91.1%) reported ocular events (82.3% had grade 1 or 2 events). Two patients (4.4%) had ocular events leading to the permanent discontinuation of study treatment. AUY922 at 70 mg/m2 plus trastuzumab standard therapy is well tolerated and active in patients with HER2-positive metastatic breast cancer who progressed on trastuzumab-based therapy.

Spontaneously occurring fundus findings observed using confocal scanning laser ophthalmoscopy in wild type Sprague Dawley rats

PURPOSE

Non-invasive in vivo imaging is an increasingly used component of pre-clinical research. However, to reliably interpret data, it may be necessary to identify and document pre-existent findings prior to initiating long-term or intensive protocols, particularly where toxicity or efficacy is under investigation. Here we report here spontaneously occurring findings from the Sprague Dawley (SD) rat eye using multi-modal confocal scanning laser ophthalmoscopy (cSLO).

METHODS

As part of ongoing studies, with the goal of excluding animals with abnormalities from further investigation, a total of 165 wild type SD rats (312 eyes) were assessed using cSLO imaging at baseline prior to initiating experiments to detect, describe, and determine the prevalence of spontaneous fundus findings.

RESULTS

Using fundus autofluorescence (FAF) as the primary screening modality, over 30% of analyzed eyes possessed some fundus finding that differed from the normal composite reference image. Unexpectedly, 100% of eyes demonstrated a diffuse hyperfluorescent region in the posterior pole that was ultimately considered normal, and formed part of the reference. Evaluated by three independent reviewers, five groups of FAF abnormalities were defined, based primarily on shape and size of the lesion. Of these, the most extensive lesions were further analyzed using infrared reflectance (IR) and red free (RF) imaging. White light and autofluorescent microscopy of excised tissue confirmed that the extensive lesions were derived from abnormalities in both the isolated retina and posterior eyecups.

CONCLUSIONS

Given the newly described hyperfluorescent glow that appears in all eyes, and the high basal rate of spontaneous lesions in the outbred SD rat, we suggest that investigators be aware of the variants of normal, and that baseline in vivo screening be considered prior to initiating intensive or expensive investigation.

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.

Misfolded proteins: from little villains to little helpers in the fight against cancer

The application of cytostatic drugs targeting the high proliferation rates of cancer cells is currently the most commonly used treatment option in cancer chemotherapy. However, severe side effects and resistance mechanisms may occur as a result of such treatment, possibly limiting the therapeutic efficacy of these agents. In recent years, several therapeutic strategies have been developed that aim at targeting not the genomic integrity and replication machinery of cancer cells but instead their protein homeostasis. During malignant transformation, the cancer cell proteome develops vast aberrations in the expression of mutated proteins, oncoproteins, drug- and apoptosis-resistance proteins, etc. A complex network of protein quality-control mechanisms, including chaperoning by heat shock proteins (HSPs), not only is essential for maintaining the extravagant proteomic lifestyle of cancer cells but also represents an ideal cancer-specific target to be tackled. Furthermore, the high rate of protein synthesis and turnover in certain types of cancer cells can be specifically directed by interfering with the proteasomal and autophagosomal protein recycling and degradation machinery, as evidenced by the clinical application of proteasome inhibitors. Since proteins with loss of their native conformation are prone to unspecific aggregations and have proved to be detrimental to normal cellular function, specific induction of misfolded proteins by HSP inhibitors, proteasome inhibitors, hyperthermia, or inducers of endoplasmic reticulum stress represents a new method of cancer cell killing exploitable for therapeutic purposes. This review describes drugs - approved, repurposed, or under investigation - that can be used to accumulate misfolded proteins in cancer cells, and particularly focuses on the molecular aspects that lead to the cytotoxicity of misfolded proteins in cancer cells.

Debio0932, a second-generation oral heat shock protein (HSP) inhibitor, in patients with advanced cancer-results of a first-in-man dose-escalation study with a fixed-dose extension phase

BACKGROUND

Objective was to determine maximum tolerated dose (MTD), recommended dose (RD) and schedule, safety, pharmacokinetic (PK) profile, pharmacodynamic (PD) effects, and antitumor activity of Debio0932, a new second-generation oral heat shock protein (HSP) inhibitor.

PATIENTS AND METHODS

This was a multicenter, uncontrolled, open-label, nonrandomized, dose-escalation study in adults with treatment-resistant advanced cancer. Groups of three patients received oral Debio0932 either daily or every other day. The starting dose of 50 mg was escalated until the MTD was reached, i.e. dose-limiting toxicity (DLT) occurred in ≥2 patients. Further 9 patients and an extension cohort of 30 patients were treated at the next lower dose (=RD). Adverse events (AEs), tumor response, PK, and HSP70 levels in peripheral blood mononuclear cells were recorded over 30 days.

RESULTS

Fifty patients were treated with doses up to 1600 mg, at which level three DLT occurred (febrile neutropenia, diarrhea, asthenia). In total, 39 patients were then treated at the RD of 1000 mg daily. Most common drug-related AEs were asthenia and gastrointestinal events. No ocular toxicities were observed. Debio0932 was rapidly absorbed and metabolized. Plasma steady state was reached within 9 days. Volume of distribution was high and elimination half-life was 9-11 h. Food had no effect on PK. PD showed large interpatient variability, but no dose-effect relationship. Partial tumor response was observed in 2 patients (NSCLC and breast cancer), stable disease (SD) in 12 patients (5 of 8 NSCLC patients). In the extension cohort, 9 patients had SD, and 1 patient a partial metabolic tumor response.

CONCLUSION

Debio0932 has limited clinical activity, together with manageable toxicity. Further development as adjunct treatment of NSCLC at daily doses of 1000 mg is warranted.

CLINICAL TRIAL

NCT01168752.