Advances in HSP27 and HSP90-targeting strategies for glioblastoma

Enhancing Magnetic Hyperthermia Efficacy through Targeted Heat Shock Protein 90 Inhibition: Unveiling Immune-Mediated Therapeutic Synergy in Glioma Treatment

The induction of heat stress response (HSR) mediated by the generation of heat shock proteins (HSPs) on exposure to magnetic hyperthermia-mediated cancer therapy (MHCT) decreases the efficacy of localized heat treatment at the tumor site, and thus therapy remains a significant challenge. Hence, the present study examined differential HSR elicited in glioma cells post-MHCT under different tumor microenvironment conditions (2D monolayers, 3D monoculture, and coculture spheroids) to recognize target genes that, when downregulated, could enhance the therapeutic effect of MHCT. Gene expression analysis following MHCT revealed that HSP90 was upregulated as compared to HSP70. Hence, to enhance the efficacy of the treatment, a combinatorial strategy using 17-DMAG as an inhibitor of HSP90 following MHCT was investigated. The effects of combinatorial therapy in terms of cell viability, HSP levels by immunofluorescence and gene expression analysis, oxidative stress generation, and alterations in cellular integrity were evaluated, where combinatorial therapy demonstrated an enhanced therapeutic outcome with maximum glioma cell death. Further, in the murine glioma model, a rapid tumor inhibition of 65 and 53% was observed within 8 days at the primary and secondary tumor sites, respectively, in the MCHT + 17-DMAG group, with abscopal effect-mediated complete tumor inhibition at both the tumor sites within 20 days of MHCT. The extracellularly released HSP90 from dying tumor cells further suggested the induction of immune response supported by the upregulation of IFN-γ and calreticulin genes in the MHCT + 17-DMAG group. Overall, our findings indicate that MHCT activates host immune systems and efficiently cooperates with the HSP90 blockade to inhibit the growth of distant metastatic tumors.

Exosomes released from U87 glioma cells treated with curcumin and/or temozolomide produce apoptosis in naive U87 cells

Glioblastoma (GBM) remains the most lethal brain tumor without any curative treatment. Exosomes can mediate cell-to-cell communication, and may function as a new type of targeted therapy. In this study, the therapeutic benefits of exosomes generated by U87 cells treated with curcumin and/or temozolomide were investigated. The cells were cultured and treated with temozolomide (TMZ), curcumin (Cur), or their combination (TMZ+Cur). Exosomes were isolated with a centrifugation kit and characterized using DLS, SEM, TEM, and Western blotting. The levels of exosomal BDNF and TNF-α were measured. Naïve U87 cells were treated with the isolated exosomes, and the effects on apoptosis-related proteins HSP27, HSP70, HSP90, and P53 were assessed. All exosomes, Cur-Exo, TMZ-Exo, and TMZ+Cur-Exo increased cleaved caspase 3, Bax, and P53 proteins, while reducing HSP27, HSP70, HSP90, and Bcl2 proteins. Moreover all treatment groups increased apoptosis in naïve U87 recipient cells. Exosomes released from treated U87 cells had less BDNF and more TNF-α compared to exosomes released from naive U87 cells. In conclusion, we showed for the first time that exosomes released from drug-treated U87 cells could be a new therapeutic approach in glioblastoma, and could reduce the side effects produced by drugs alone. This concept needs to be further examined in animal models before clinical trials could be considered.

Natural Products Targeting Hsp90 for a Concurrent Strategy in Glioblastoma and Neurodegeneration

Glioblastoma multiforme (GBM) is one of the most common aggressive, resistant, and invasive primary brain tumors that share neurodegenerative actions, resembling many neurodegenerative diseases. Although multiple conventional approaches, including chemoradiation, are more frequent in GBM therapy, these approaches are ineffective in extending the mean survival rate and are associated with various side effects, including neurodegeneration. This review proposes an alternative strategy for managing GBM and neurodegeneration by targeting heat shock protein 90 (Hsp90). Hsp90 is a well-known molecular chaperone that plays essential roles in maintaining and stabilizing protein folding to degradation in protein homeostasis and modulates signaling in cancer and neurodegeneration by regulating many client protein substrates. The therapeutic benefits of Hsp90 inhibition are well-known for several malignancies, and recent evidence highlights that Hsp90 inhibitors potentially inhibit the aggressiveness of GBM, increasing the sensitivity of conventional treatment and providing neuroprotection in various neurodegenerative diseases. Herein, the overview of Hsp90 modulation in GBM and neurodegeneration progress has been discussed with a summary of recent outcomes on Hsp90 inhibition in various GBM models and neurodegeneration. Particular emphasis is also given to natural Hsp90 inhibitors that have been evidenced to show dual protection in both GBM and neurodegeneration.

Targeting Heat Shock Proteins in Malignant Brain Tumors: From Basic Research to Clinical Trials

Heat shock proteins (HSPs) are conservative and ubiquitous proteins that are expressed both in prokaryotic and eukaryotic organisms and play an important role in cellular homeostasis, including the regulation of proteostasis, apoptosis, autophagy, maintenance of signal pathways, protection from various stresses (e.g., hypoxia, ionizing radiation, etc.). Therefore, HSPs are highly expressed in tumor cells, including malignant brain tumors, where they also associate with cancer cell invasion, metastasis, and resistance to radiochemotherapy. In the current review, we aimed to assess the diagnostic and prognostic values of HSPs expression in CNS malignancies as well as the novel treatment approaches to modulate the chaperone levels through the application of inhibitors (as monotherapy or in combination with other treatment modalities). Indeed, for several proteins (i.e., HSP10, HSPB1, DNAJC10, HSPA7, HSP90), a direct correlation between the protein level expression and poor overall survival prognosis for patients was demonstrated that provides a possibility to employ them as prognostic markers in neuro-oncology. Although small molecular inhibitors for HSPs, particularly for HSP27, HSP70, and HSP90 families, were studied in various solid and hematological malignancies demonstrating therapeutic potential, still their potential was not yet fully explored in CNS tumors. Some newly synthesized agents (e.g., HSP40/DNAJ inhibitors) have not yet been evaluated in GBM. Nevertheless, reported preclinical studies provide evidence and rationale for the application of HSPs inhibitors for targeting brain tumors.

The Potential Role of Exosomal Proteins in Prostate Cancer

Prostate cancer is the most prevalent malignant tumor in men across developed countries. Traditional diagnostic and therapeutic methods for this tumor have become increasingly difficult to adapt to today’s medical philosophy, thus compromising early detection, diagnosis, and treatment. Prospecting for new diagnostic markers and therapeutic targets has become a hot topic in today’s research. Notably, exosomes, small vesicles characterized by a phospholipid bilayer structure released by cells that is capable of delivering different types of cargo that target specific cells to regulate biological properties, have been extensively studied. Exosomes composition, coupled with their interactions with cells make them multifaceted regulators in cancer development. Numerous studies have described the role of prostate cancer-derived exosomal proteins in diagnosis and treatment of prostate cancer. However, so far, there is no relevant literature to systematically summarize its role in tumors, which brings obstacles to the later research of related proteins. In this review, we summarize exosomal proteins derived from prostate cancer from different sources and summarize their roles in tumor development and drug resistance.

GPR17 signaling activation by CHBC agonist induced cell death via modulation of MAPK pathway in glioblastoma

AIM

Glioblastoma multiforme (GBM) is the most common and aggressive primary adult brain tumor. GBM is characterized by a heterogeneous population of cells that are resistant to chemotherapy. Recently, we have synthesized CHBC, a novel indole derivative targeted to GBM biomarker G-protein-coupled receptor 17 and inhibitor of GBM cells. In this study, CHBC was further investigated to characterize the efficiency of this agonist at the molecular level and its underlying mechanism in GBM cell death induction.

MATERIALS AND METHODS

The effect of CHBC and TMZ was determined using time dependent inhibitor assay in glioblastoma cells, LN229 and SNB19. Drug induced cell cycle arrest was measured using PI staining followed by image analysis. The induction of apoptosis and mechanism of action of CHBC was studied using apoptosis, caspase 3/7 and mitochondrial membrane permeability assays. Modulation of the key genes involved in MAPK signaling pathway was also measured using immunoblotting array.

KEY FINDINGS

The inhibitory kinetic study has revealed that CHBC inhibited SNB19 and LN229 cell growth in a time-dependent manner. Furthermore, CHBC with the IC50 of 85 μM, mediated cell death through an apoptosis mechanism in both studied cell lines. The study also has revealed that CHBC targets GPR17 leading to the induction of apoptosis via the activation of Caspase 3/7 and dysfunction of mitochondrial membrane potential. In addition, CHBC treatment led to marked G2/M cell cycle arrest. The protein array has confirmed the anticancer effect of CHBC by the disruption of the mitogen-activated protein kinase pathway (MAPK).

SIGNIFICANCE

Taken together, these results demonstrated that CHBC induced G2/M cell cycle arrest and apoptosis by disrupting MAPK signaling in human glioblastoma cells. This study concludes that CHBC represent a class of compounds for treating glioblastoma.

Recent Applications of Retro-Inverso Peptides

Natural and de novo designed peptides are gaining an ever-growing interest as drugs against several diseases. Their use is however limited by the intrinsic low bioavailability and poor stability. To overcome these issues retro-inverso analogues have been investigated for decades as more stable surrogates of peptides composed of natural amino acids. Retro-inverso peptides possess reversed sequences and chirality compared to the parent molecules maintaining at the same time an identical array of side chains and in some cases similar structure. The inverted chirality renders them less prone to degradation by endogenous proteases conferring enhanced half-lives and an increased potential as new drugs. However, given their general incapability to adopt the 3D structure of the parent peptides their application should be careful evaluated and investigated case by case. Here, we review the application of retro-inverso peptides in anticancer therapies, in immunology, in neurodegenerative diseases, and as antimicrobials, analyzing pros and cons of this interesting subclass of molecules.

Inhibition of HSP90 as a Strategy to Radiosensitize Glioblastoma: Targeting the DNA Damage Response and Beyond

Radiotherapy is an essential component of multi-modality treatment of glioblastoma (GBM). However, treatment failure and recurrence are frequent and give rise to the dismal prognosis of this aggressive type of primary brain tumor. A high level of inherent treatment resistance is considered to be the major underlying reason, stemming from constantly activated DNA damage response (DDR) mechanisms as a consequence of oncogene overexpression, persistent replicative stress, and other so far unknown reasons. The molecular chaperone heat shock protein 90 (HSP90) plays an important role in the establishment and maintenance of treatment resistance, since it crucially assists the folding and stabilization of various DDR regulators. Accordingly, inhibition of HSP90 represents a multi-target strategy to interfere with DDR function and to sensitize cancer cells to radiotherapy. Using NW457, a pochoxime-based HSP90 inhibitor with favorable brain pharmacokinetic profile, we show here that HSP90 inhibition at low concentrations with per se limited cytotoxicity leads to downregulation of various DNA damage response factors on the protein level, distinct transcriptomic alterations, impaired DNA damage repair, and reduced clonogenic survival in response to ionizing irradiation in glioblastoma cells in vitro. In vivo, HSP90 inhibition by NW457 improved the therapeutic outcome of fractionated CBCT-based irradiation in an orthotopic, syngeneic GBM mouse model, both in terms of tumor progression and survival. Nevertheless, in view of the promising in vitro results the in vivo efficacy was not as strong as expected, although apart from the radiosensitizing effects HSP90 inhibition also reduced irradiation-induced GBM cell migration and tumor invasiveness. Hence, our findings identify the combination of HSP90 inhibition and radiotherapy in principle as a promising strategy for GBM treatment whose performance needs to be further optimized by improved inhibitor substances, better formulations and/or administration routes, and fine-tuned treatment sequences.

Small Heat Shock Proteins in Cancers: Functions and Therapeutic Potential for Cancer Therapy

Small heat shock proteins (sHSPs) are ubiquitous ATP-independent chaperones that play essential roles in response to cellular stresses and protein homeostasis. Investigations of sHSPs reveal that sHSPs are ubiquitously expressed in numerous types of tumors, and their expression is closely associated with cancer progression. sHSPs have been suggested to control a diverse range of cancer functions, including tumorigenesis, cell growth, apoptosis, metastasis, and chemoresistance, as well as regulation of cancer stem cell properties. Recent advances in the field indicate that some sHSPs have been validated as a powerful target in cancer therapy. In this review, we present and highlight current understanding, recent progress, and future challenges of sHSPs in cancer development and therapy.

A Brain-Penetrating Hsp90 Inhibitor NXD30001 Inhibits Glioblastoma as a Monotherapy or in Combination With Radiation

Glioblastoma multiforme (GBM) is a highly heterogeneous disease, which is initiated and sustained by various molecular alterations in an array of signal transduction pathways. Heat-shock protein 90 (Hsp90) is a molecular chaperone and is critically implicated in folding and activation of a diverse group of client proteins, many of which are key regulators for glioblastoma biology. We here assessed the anti-neoplastic efficacy of a novel brain-penetrating Hsp90 inhibitor NXD30001 as a monotherapy and combined with radiation in vitro and in vivo. Our results demonstrated that NXD30001 potently inhibited neurosphere formation, growth, and survival of CD133+ GBM cells with the half maximal inhibitory concentration at low nanomolar range, but CD133- GBM cells were less sensitive to NXD30001. NXD30001 also increased radio-sensitivity in glioblastoma stem cells (GSCs) at suboptimal concentrations. Moreover, NXD30001 dose-dependently decreased phosphorylation levels of multiple Hsp90 client proteins which play key roles in GBM, such as EGFR, Akt, c-Myc, and Notch1. In addition, NXD30001 could impair DNA damage response and endoplasmic reticulum stress response after radiotherapy by alteration of the related proteins expression. In a murine orthotopic model of human glioblastoma, NXD30001 marvelously induced tumor regression and extended median survival of tumor-bearing mice by approximately 20% when compared with the vehicle group (37 d vs 31 d, P<0.05). Radiotherapy solely increased median survival of tumor-bearing mice from 31 d to 38 d (P<0.05), while NXD30001 combined with radiation further extended survival to 43 d (P<0.05). We concluded that GSCs are more sensitive to NXD30001 than non-stem GBM cells, and NXD30001 in combination with radiation exerts better inhibitive effect in GBM progression than monotherapy.

[Biology behavior of head and neck squamous cell cancer cells changes after knocking down heat shock protein 27]

OBJECTIVE

This study aimed to observe the metastatic behavior of head and neck squamous cell carcinoma cells after knocking down heat shock protein (Hsp) 27.

METHODS

The experiment was divided into three groups: the lentivirus vector plasmid of pLenti-shRNA-Hsp27 was transfected into UM-SCC-22B cells as experimental group (shHsp27 group), routine culture of UM-SCC-22B cells as blank control (ctrl group), UM-SCC-22B cells transfection of pLenti-shRNA-ctrl lentivirus vector as negative control (shctrl group). Through real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot assay to detect the mRNA expression of Hsp27 in three groups. MTS assay was performed to detect cell-proliferation changes, wounding healing assay was performed to detect cell-migration changes, and Matrigel Transwell invasion assay was performed to detect cell-invasion changes.

RESULTS

The expression of Hsp27 in shHsp27 group decreased signifi-cantly; MTS assay showed that UM-SCC-22B before and after Hsp27 knockdown had similar proliferation rates after being cultured for 24 or 48 h. Compared with the ctrl group, the shHsp27 group decreased the metastatic behavior by 4.38-fold in migration and 2.03-fold in cell invasion.

CONCLUSIONS

Stably transfected lentivirus vector plasmid of pLenti-shRNA-Hsp27 can efficiently decrease Hsp27 expression and reduce the metastasis ability of UM-SCC-22B.

Molecular chaperones in the brain endothelial barrier: neurotoxicity or neuroprotection?

Brain microvascular endothelial cells (BMECs) interact with astrocytes and pericytes to form the blood-brain barrier (BBB). Their compromised function alters the BBB integrity, which is associated with early events in the pathogenesis of cancer, neurodegenerative diseases, and epilepsy. Interestingly, these conditions also induce the expression of heat shock proteins (HSPs). Here we review the contribution of major HSP families to BMEC and BBB function. Although investigators mainly report protective effects of HSPs in brain, contrasted results were obtained in BMEC, which depend both on the HSP and on its location, intra- or extracellular. The therapeutic potential of HSPs must be scrupulously analyzed before targeting them in patients to reduce the progression of brain lesions and improve neurologic outcomes in the long term.-Thuringer, D., Garrido, C. Molecular chaperones in the brain endothelial barrier: neurotoxicity or neuroprotection?

MET in glioma: signaling pathways and targeted therapies

Gliomas represent the most common type of malignant brain tumor, among which, glioblastoma remains a clinical challenge with limited treatment options and dismal prognosis. It has been shown that the dysregulated receptor tyrosine kinase (RTK, including EGFR, MET, PDGFRα, ect.) signaling pathways have pivotal roles in the progression of gliomas, especially glioblastoma. Increasing evidence suggests that expression levels of the RTK MET and its specific stimulatory factors are significantly increased in glioblastomas compared to those in normal brain tissues, whereas some negative regulators are found to be downregulated. Mutations in MET, as well as the dysregulation of other regulators of cross-talk with MET signaling pathways, have also been identified. MET and its ligand hepatocyte growth factor (HGF) play a critical role in the proliferation, survival, migration, invasion, angiogenesis, stem cell characteristics, and therapeutic resistance and recurrence of glioblastomas. Therefore, combined targeted therapy for this pathway and associated molecules could be a novel and attractive strategy for the treatment of human glioblastoma. In this review, we highlight progress made in the understanding of MET signaling in glioma and advances in therapies targeting HGF/MET molecules for glioma patients in recent years, in addition to studies on the expression and mutation status of MET.

Novel Immunotherapeutics for Treatment of Glioblastoma: The Last Decade of Research

Despite surgical resection and adjuvant chemoradiation, survival for glioblastoma remains poor. Because of the dismal prognosis, attention has shifted to alternative adjuvant treatment modalities. Although traditionally limited to systemic malignancies (melanoma, lung and colon cancer), the field of immunotherapy has recently identified glioblastoma as a potential target for new treatments. Anti-tumor vaccines (dendritic cell/heat shock), checkpoint inhibitors, chimeric T-cell receptors, and virotherapy all have been preliminarily trialed in glioblastoma patients with reasonable success and safety. Although there are certainly limitations due to autoimmune reactions and immune escape, immunotherapeutics hold much promise in the future treatment paradigms for malignant glioma.

Novel Immunotherapeutics for the Treatment of Glioblastoma: The Last Decade of Research

Despite surgical resection and adjuvant chemoradiation, survival for glioblastoma remains poor. Because of the dismal prognosis, attention has shifted to alternative adjuvant treatment modalities. Although traditionally limited to systemic malignancies (melanoma, lung and colon cancer), the field of immunotherapy has recently identified glioblastoma as a potential target for new treatments. Anti-tumor vaccines (dendritic cell/heat shock), checkpoint inhibitors, chimeric T-cell receptors, and virotherapy all have been preliminarily trialed in glioblastoma patients with reasonable success and safety. Although there are limitations due to autoimmune reactions and immune escape, immunotherapeutics hold much promise in the future treatment paradigms for malignant glioma.

Glioma progression through the prism of heat shock protein mediated extracellular matrix remodeling and epithelial to mesenchymal transition

Glial tumor is one of the intrinsic brain tumors with high migratory and infiltrative potential. This essentially contributes to the overall poor prognosis by circumvention of conventional treatment regimen in glioma. The underlying mechanism in gliomagenesis is bestowed by two processes- Extracellular matrix (ECM) Remodeling and Epithelial to mesenchymal transition (EMT). Heat Shock Family of proteins (HSPs), commonly known as "molecular chaperons" are documented to be upregulated in glioma. A positive correlation also exists between elevated expression of HSPs and invasive capacity of glial tumor. HSPs overexpression leads to mutational changes in glioma, which ultimately drive cells towards EMT, ECM modification, malignancy and invasion. Differential expression of HSPs - a factor providing cytoprotection to glioma cells, also contributes towards its radioresistance /chemoresistance. Various evidences also display upregulation of EMT and ECM markers by various heat shock inducing proteins e.g. HSF-1. The aim of this review is to study in detail the role of HSPs in EMT and ECM leading to radioresistance/chemoresistance of glioma cells. The existing treatment regimen for glioma could be enhanced by targeting HSPs through immunotherapy, miRNA and exosome mediated strategies. This could be envisaged by better understanding of molecular mechanisms underlying glial tumorigenesis in relation to EMT and ECM remodeling under HSPs influence. Our review might showcase fresh potential for the development of next generation therapeutics for effective glioma management.

Low co-expression of epidermal growth factor receptor and its chaperone heat shock protein 90 is associated with worse prognosis in primary glioblastoma, IDH-wild-type

Epidermal growth factor receptor (EGFR) is a major oncogenic driver in glioblastoma (GBM) without mutations in the isocitrate dehydrogenase gene (IDH-wildtype). Heat shock protein 90 (HSP90) is a regulator of the stability of oncogenic proteins including EGFR, thereby acting as a molecular chaperone. We investigated the expression of EGFR and its chaperone HSP90 in GBM, IDH-wildtype. Tissue availability permitted analysis of 237/449 consecutive GBM cases, among them 214 IDH-wildtype (90.3%). The expression of EGFR and HSP90 was analysed by immunohistochemistry on a tissue microarray containing various tumour regions. The expression intensity (EI), and an expression score (ES) combining the percentage of stained cells with EI were determined for both markers. Overall, there was a positive correlation between EGFR and HSP90 expression (EI; r=0.275, P<0.001; ES, r=0.333, P<0.001). The expression of EGFR and HSP90 was significantly higher in the tumour centre, compared to the infiltration front (EI, P=0.002; ES, P<0.001). Survival data were available in 96 IDH-wildtype cases, and high expression of EGFR (ES only) was in trend associated with better outcome, but failed to meet statyistical significance (P=0.061). A combination of EGFR and HSP90, however, discriminated between different prognostic groups, with EGFRlow/HSP90low tumours showing the worst prognosis in univariate analysis (P=0.001), and in multivariate analysis including the other relevant prognostic factors age, MGMT status and postoperative treatment [n=76; hazard ratio (HR)=0.571; 95% confidence interval (CI) 0.328-0.996; P=0.048]. EGFR expression stratified most pronounced among HSP90low tumours, where the EGFRhigh phenotype was associated with longer survival. Our results reveal a variable reliance on the signalling pathway by EGFR in GBM, IDH-wildtype. Low co-expression was associated with worse prognosis.

HSP90 inhibitors in the context of heat shock and the unfolded protein response: effects on a primary canine pulmonary adenocarcinoma cell line

BACKGROUND

Agents targeting HSP90 and GRP94 are seldom tested in stressed contexts such as heat shock (HS) or the unfolded protein response (UPR). Tumor stress often activates HSPs and the UPR as pro-survival mechanisms. This begs the question of stress effects on chemotherapeutic efficacy, particularly with drugs targeting chaperones such as HSP90 or GRP94. We tested the utility of several HSP90 inhibitors, including PU-H71 (targeting GRP94), on a primary canine lung cancer line under HS/UPR stress compared to control conditions.

METHODS

We cultured canine bronchoalveolar adenocarcinoma cells that showed high endogenous HSP90 and GRP94 expression; these levels substantially increased upon HS or UPR induction. We treated cells with HSP90 inhibitors 17-DMAG, 17-AAG or PU-H71 under standard conditions, HS or UPR. Cell viability/survival was assayed. Antibody arrays measured intracellular signalling and apoptosis profiles.

RESULTS

HS and UPR had varying effects on cells treated with different HSP90 inhibitors; in particular, HS and UPR promoted resistance to inhibitors in short-term assays, but combinations of UPR stress and PU-H571 showed potent cytotoxic activity in longer-term assays. Array data indicated altered signalling pathways, with apoptotic and pro-survival implications. UPR induction + dual targeting of HSP90 and GRP94 swayed the balance toward apoptosis.

CONCLUSION

Cellular stresses, endemic to tumors, or interventionally inducible, can deflect or enhance chemo-efficacy, particularly with chaperone-targeting drugs. Stress is likely not held accountable when testing new pharmacologics or assessing currently-used drugs. A better understanding of stress impacts on drug activities should be critical in improving therapeutic targeting and in discerning mechanisms of drug resistance.