Targeting Heat-Shock Protein 90 (HSP90) as a Complementary Strategy to Immune Checkpoint Blockade for Cancer Therapy

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.

Heat Shock Proteins, a Double-Edged Sword: Significance in Cancer Progression, Chemotherapy Resistance and Novel Therapeutic Perspectives

Heat shock proteins (Hsps) are involved in one of the adaptive mechanisms protecting cells against environmental and metabolic stress. Moreover, the large role of these proteins in the carcinogenesis process, as well as in chemoresistance, was noticed. This review aims to draw attention to the possibilities of using Hsps in developing new cancer therapy methods, as well as to indicate directions for future research on this topic. In order to discuss this matter, a thorough review of the latest scientific literature was carried out, taking into account the importance of selected proteins from the Hsp family, including Hsp27, Hsp40, Hsp60, Hsp70, Hsp90 and Hsp110. One of the more characteristic features of all Hsps is that they play a multifaceted role in cancer progression, which makes them an obvious target for modern anticancer therapy. Some researchers emphasize the importance of directly inhibiting the action of these proteins. In turn, others point to their possible use in the design of cancer vaccines, which would work by inducing an immune response in various types of cancer. Due to these possibilities, it is believed that the use of Hsps may contribute to the progress of oncoimmunology, and thus help in the development of modern anticancer therapies, which would be characterized by higher effectiveness and lower toxicity to the patients.

Predictive value of CDC37 gene expression for targeted therapy in metastatic colorectal cancer

BACKGROUND

CDC37 is a key determinant of client kinase recruitment to the HSP90 chaperoning system. We hypothesized that kinase-specific dependency on CDC37 alters the efficacy of targeted therapies for metastatic colorectal cancer (mCRC).

MATERIAL AND METHODS

Two independent mCRC cohorts were analyzed to compare the survival outcomes between CDC37-high and CDC37-low patients (stratified by the median cutoff values): the CALGB/SWOG 80405 trial (226 and 207 patients receiving first-line bevacizumab- and cetuximab-containing chemotherapies, respectively) and Japanese retrospective (50 refractory patients receiving regorafenib) cohorts. A dataset of specimens submitted to a commercial CLIA-certified laboratory was utilized to characterize molecular profiles of CDC37-high (top quartile, N = 5055) and CDC37-low (bottom quartile, N = 5055) CRCs.

RESULTS

In the bevacizumab-treated group, CDC37-high patients showed significantly better progression-free survival (PFS) (median 13.3 vs 9.6 months, hazard ratio [HR] 0.59, 95% confidence interval [CI] 0.44-0.79, p < 0.01) than CDC37-low patients. In the cetuximab-treated group, CDC37-high and CDC37-low patients had similar outcomes. In the regorafenib-treated group, CDC37-high patients showed significantly better overall survival (median 11.3 vs 6.0 months, HR 0.24, 95% CI 0.11-0.54, p < 0.01) and PFS (median 3.5 vs 1.9 months, HR 0.51, 95% CI 0.28-0.94, p = 0.03). Comprehensive molecular profiling revealed that CDC37-high CRCs were associated with higher VEGFA, FLT1, and KDR expressions and activated hypoxia signature.

CONCLUSIONS

CDC37-high mCRC patients derived more benefit from anti-VEGF therapies, including bevacizumab and regorafenib, but not from cetuximab. Molecular profiles suggested that such tumors were dependent on angiogenesis-relating pathways.

The tumour-promoting role of protein homeostasis: Implications for cancer immunotherapy

Protein homeostasis, an important aspect of cellular fitness that encompasses the balance of production, folding and degradation of proteins, has been linked to several diseases of the human body. Multiple interconnected pathways coordinate to maintain protein homeostasis within the cell. Recently, the role of the protein homeostasis network in tumorigenesis and tumour progression has gradually come to light. Here, we summarize the involvement of the most prominent components of the protein quality control mechanisms (HSR, UPS, autophagy, UPR and ERAD) in tumour development and cancer immunity. In addition, evidence for protein quality control mechanisms and targeted drugs is outlined, and attempts to combine these drugs with cancer immunotherapy are discussed. Altogether, combination therapy represents a promising direction for future investigations, and this exciting insight will be further illuminated by the development of drugs that can reach a balance between the benefits and hazards associated with protein homeostasis interference.

Heat shock proteins in cancer - Known but always being rediscovered: Their perspectives in cancer immunotherapy

Heat shock proteins (HSPs) represent cellular chaperones that are classified into several families, including HSP27, HSP40, HSP60, HSP70, and HSP90. The role of HSPs in the cell includes the facilitation of protein folding and maintaining protein structure. Both processes play crucial roles during stress conditions in the cell such as heat shock, degradation, and hypoxia. Moreover, HSPs are important modulators of cellular proliferation and differentiation, and are strongly associated with the molecular orchestration of carcinogenesis. The expression and/or activity of HSPs in cancer cells is generally abnormally high and is associated with increased metastatic potential and activity of cancer stem cells, more pronounced angiogenesis, downregulated apoptosis, and the resistance to anticancer therapy in many patients. Based on the mentioned reasons, HSPs have strong potential as valid diagnostic, prognostic, and therapeutic biomarkers in clinical oncology. In addition, numerous papers describe the role of HSPs as chaperones in the regulation of immune responses inside and outside the cell. Importantly, highly expressed/activated HSPs may be inhibited via immunotherapeutic targets in various types of cancers. The aim of this work is to provide a comprehensive overview of the relationship between HSPs and the tumor cell with the intention of highlighting the potential use of HSPs in personalized cancer management.

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.

Cisplatin-induced HSF1-HSP90 axis enhances the expression of functional PD-L1 in oral squamous cell carcinoma

Immune checkpoint inhibitor-based cancer immunotherapy has provided an additional therapeutic option for oral squamous cell carcinoma (OSCC) with recurrence or distant metastases. However, further improvement of OSCC treatment is required to develop the optimal combination or order for chemoradiotherapy and immunotherapy. Along with the accumulation of clinical knowledge and evidence, it is also essential to clarify the biological impact of chemo-radiotherapeutic agents on the cancer immune microenvironment. In this study, we investigated the effects of cisplatin (CDDP), a key therapeutic agent for OSCC, on programmed death-ligand 1 (PD-L1) expression in OSCC lines. Although CDDP treatment increased the surface levels of PD-L1 on OSCC cell lines, the gene and total protein expression levels of PD-L1 were not altered. We also demonstrated that the phosphorylation of heat shock factor 1 and heat shock protein 90 was involved in this process. In addition, CDDP-induced PD-L1 attenuated the target-specific cytotoxic T lymphocyte reaction to OSCC. These results provide an immunobiological basis for the response of OSCC to CDDP and will contribute to our biological understanding of the action of novel combination therapy including immunotherapy together with platinum-based chemotherapy for OSCC.

Novel peptide-based vaccine targeting heat shock protein 90 induces effective antitumor immunity in a HER2+ breast cancer murine model

Background

Heat shock protein 90 (HSP90) is a protein chaperone for most of the important signal transduction pathways in human epidermal growth factor receptor 2-positive (HER2+) breast cancer, including human epidermal growth factor receptor 2, estrogen receptor, progesterone receptor and Akt. The aim of our study is to identify peptide-based vaccines and to develop an effective immunotherapeutics for the treatment of HER2+ breast cancer.

Methods

HSP90-derived major histocompatibility complex (MHC) class II epitopes were selected using in silico algorithms and validated by enzyme-linked immunospot (ELISPOT). In vivo antitumor efficacy was evaluated in MMTVneu-transgenic mice. HSP90 peptide-specific systemic T-cell responses were assessed using interferon gamma ELISPOT assay, and immune microenvironment in tumors was evaluated using multiplex immunohistochemistry and TCRβ sequencing.

Results

First, candidate HSP90-derived MHC class II epitopes with high binding affinities across multiple human HLA class II genotypes were identified using in silico algorithms. Among the top 10 peptides, p485 and p527 were selected as promising Th1 immunity-inducing epitopes with low potential for Th2 immunity induction. The selected MHC class II HSP90 peptides induced strong antigen-specific T cell responses, which was induced by cross-priming of CD8⁺ T cells in vivo. The HSP90 peptide vaccines were effective in the established tumor model, and their efficacy was further enhanced when combined with stimulator of interferon genes (STING) agonist and/or anticytotoxic T lymphocyte-associated antigen-4 antibody in MMTVneu-transgenic mice. Increased tumor rejection was associated with increased systemic HSP90-specific T-cell responses, increased T-cell recruitment in tumor microenvironment, intermolecular epitope spreading, and increased rearrangement of TCRβ by STING agonist.

Conclusions

In conclusion, we have provided the first preclinical evidence of the action mechanism of HSP90 peptide vaccines with a distinct potential for improving breast cancer treatment.

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

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

Immunostimulatory Properties of Chemotherapy in Breast Cancer: From Immunogenic Modulation Mechanisms to Clinical Practice

Breast cancer (BC) is the most common malignancy among females. Chemotherapy drugs remain the cornerstone of treatment of BC and undergo significant shifts over the past 100 years. The advent of immunotherapy presents promising opportunities and constitutes a significant complementary to existing therapeutic strategies for BC. Chemotherapy as a cytotoxic treatment that targets proliferation malignant cells has recently been shown as an effective immune-stimulus in multiple ways. Chemotherapeutic drugs can cause the release of damage-associated molecular patterns (DAMPs) from dying tumor cells, which result in long-lasting antitumor immunity by the key process of immunogenic cell death (ICD). Furthermore, Off-target effects of chemotherapy on immune cell subsets mainly involve activation of immune effector cells including natural killer (NK) cells, dendritic cells (DCs), and cytotoxic T cells, and depletion of immunosuppressive cells including Treg cells, M2 macrophages and myeloid-derived suppressor cells (MDSCs). Current mini-review summarized recent large clinical trials regarding the combination of chemotherapy and immunotherapy in BC and addressed the molecular mechanisms of immunostimulatory properties of chemotherapy in BC. The purpose of our work was to explore the immune-stimulating effects of chemotherapy at the molecular level based on the evidence from clinical trials, which might be a rationale for combinations of chemotherapy and immunotherapy in BC.

Boosting Natural Killer Cell Therapies in Glioblastoma Multiforme Using Supramolecular Cationic Inhibitors of Heat Shock Protein 90

Allogeneic natural killer (aNK) cell adoptive therapy has the potential to dramatically impact clinical outcomes of glioblastoma multiforme (GBM). However, in order to exert therapeutic activity, NK cells require tumor expression of ligands for activating receptors, such as MHC Class I peptide A/B (MICA/B) and ULBPs. Here, we describe the use of a blood-brain barrier (BBB) permissive supramolecular cationic drug vehicle comprising an inhibitor of the chaperone heat shock protein 90 (Hsp90), which sustains a cytotoxic effect on GBM cells, boosts the expression of MICA/B and ULBPs on the residual population, and augments the activity of clinical-grade aNK cells (GTA002). First, we identify Hsp90 mRNA transcription and gain of function as significantly upregulated in GBM compared to other central nervous system tumors. Through a rational chemical design, we optimize a radicicol supramolecular prodrug containing cationic excipients, SCI-101, which displays >2-fold increase in relative BBB penetration compared to less cationic formulations in organoids, in vitro. Using 2D and 3D biological models, we confirm SCI-101 sustains GBM cytotoxicity 72 h after drug removal and induces cell surface MICA/B protein and ULBP mRNA up to 200% in residual tumor cells compared to the naked drug alone without augmenting the shedding of MICA/B, in vitro. Finally, we generate and test the sequential administration of SCI-101 with a clinical aNK cell therapy, GTA002, differentiated and expanded from healthy umbilical cord blood CD34⁺ hematopoietic stem cells. Using a longitudinal in vitro model, we demonstrate >350% relative cell killing is achieved in SCI-101-treated cell lines compared to vehicle controls. In summary, these data provide a first-of-its-kind BBB-penetrating, long-acting inhibitor of Hsp90 with monotherapy efficacy, which improves response to aNK cells and thus may rapidly alter the treatment paradigm for patients with GBM.

The HSP Immune Network in Cancer

Heat shock proteins are molecular chaperones which support tumor development by regulating various cellular processes including unfolded protein response, mitochondrial bioenergetics, apoptosis, autophagy, necroptosis, lipid metabolism, angiogenesis, cancer cell stemness, epithelial-mesenchymal transition and tumor immunity. Apart from their intracellular activities, HSPs have also distinct extracellular functions. However, the role that HSP chaperones play in the regulation of immune responses inside and outside the cell is not yet clear. Herein, we explore the intracellular and extracellular immunologic functions of HSPs in cancer. A broader understanding of how HSPs modulate immune responses may provide critical insights for the development of effective immunotherapies.

Progression of Myeloproliferative Neoplasms (MPN): Diagnostic and Therapeutic Perspectives

Classical BCR-ABL-negative myeloproliferative neoplasms (MPN) are a heterogeneous group of hematologic malignancies, including essential thrombocythemia (ET), polycythemia vera (PV), and primary myelofibrosis (PMF), as well as post-PV-MF and post-ET-MF. Progression to more symptomatic disease, such as overt MF or acute leukemia, represents one of the major causes of morbidity and mortality. There are clinically evident but also subclinical types of MPN progression. Clinically evident progression includes evolution from ET to PV, ET to post-ET-MF, PV to post-PV-MF, or pre-PMF to overt PMF, and transformation of any of these subtypes to myelodysplastic neoplasms or acute leukemia. Thrombosis, major hemorrhage, severe infections, or increasing symptom burden (e.g., pruritus, night sweats) may herald progression. Subclinical types of progression may include increases in the extent of bone marrow fibrosis, increases of driver gene mutational allele burden, and clonal evolution. The underlying causes of MPN progression are diverse and can be attributed to genetic alterations and chronic inflammation. Particularly, bystander mutations in genes encoding epigenetic regulators or splicing factors were associated with progression. Finally, comorbidities such as systemic inflammation, cardiovascular diseases, and organ fibrosis may augment the risk of progression. The aim of this review was to discuss types and mechanisms of MPN progression and how their knowledge might improve risk stratification and therapeutic intervention. In view of these aspects, we discuss the potential benefits of early diagnosis using molecular and functional imaging and exploitable therapeutic strategies that may prevent progression, but also highlight current challenges and methodological pitfalls.

Enhancing the Therapeutic Efficacy of KRASG12C Inhibitors in Lung Adenocarcinoma Cell Models by Cotargeting the MAPK Pathway or HSP90

Background

KRAS^G12C inhibitors have shown promising efficacy in early clinical trials, but drug resistance compromises their long-term benefits. Therefore, it is critical to understand the mechanisms of drug resistance and to design appropriate combinatory treatments to improve efficacy.

Methods

To understand the comprehensive mechanisms of drug resistance, we treated lung cancer cells with KRAS^G12C inhibitors for different periods and performed transcriptional profiling and signaling analysis to identify critical factors and pathways that drive drug tolerance and resistance. We also evaluated several drug combinations in vitro and in vivo to identify potentially effective therapeutics.

Results

We found that the feedback activation of multiple receptor tyrosine kinases (RTKs) may have cooperatively induced intrinsic and adaptive resistance to KRAS^G12C inhibitors. Notably, continuous KRAS inhibition induced a multidrug-resistant phenotype, implying that upfront combinatory treatment might be required to treat this group of patients. We also demonstrated that concurrently targeting multiple nodes in the RTK/RAS/RAF/MEK/ERK axis improved the efficacy of KRAS^G12C inhibitors, mainly by suppressing the reactivation of the mitogen-activated protein kinase (MAPK) pathway. Moreover, the combined use of HSP90 and KRAS^G12C inhibitors effectively induced tumor regression in lung adenocarcinoma models in vitro and in vivo.

Conclusion

Together, our findings revealed mechanisms underlying KRAS^G12C inhibitors resistance and provided novel candidate combinatory strategies to improve their anticancer activity.

Mirage or long-awaited oasis: reinvigorating T-cell responses in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is plagued by a dismal 5-year survival rate, early onset of metastasis and limited efficacy of systemic therapies. This scenario highlights the need to fervently pursue novel therapeutic strategies to treat this disease. Recent research has uncovered complicated dynamics within the tumor microenvironment (TME) of PDAC. An abundant stroma provides a framework for interactions between cancer-associated fibroblasts, suppressive myeloid cells and regulatory lymphocytes, which together create an inhospitable environment for adaptive immune responses. This accounts for the poor infiltration and exhausted phenotypes of effector T cells within pancreatic tumors. Innovative studies in genetically engineered mouse models have established that with appropriate pharmacological modulation of suppressive elements in the TME, T cells can be prompted to regress pancreatic tumors. In light of this knowledge, innovative combinatorial strategies involving immunotherapy and targeted therapies working in concert are rapidly emerging. This review will highlight recent advances in the field related to immune suppression in PDAC, emerging preclinical data and rationale for ongoing immunotherapy clinical trials. In particular, we draw attention to foundational findings involving T-cell activity in PDAC and encourage development of novel therapeutics to improve T-cell responses in this challenging disease.

Single-cell RNA sequencing identify SDCBP in ACE2-positive bronchial epithelial cells negatively correlates with COVID-19 severity

The coronavirus disease 2019 (COVID‐19), caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), has resulted in many deaths throughout the world. It is vital to identify the novel prognostic biomarkers and therapeutic targets to assist with the subsequent diagnosis and treatment plan to mitigate the expansion of COVID‐19. Since angiotensin‐converting enzyme 2 (ACE2)‐positive cells are hosts for COVID‐19, we focussed on this cell type to explore the underlying mechanisms of COVID‐19. In this study, we identified that ACE2‐positive cells from the bronchoalveolar lavage fluid (BALF) of patients with COVID‐19 belong to bronchial epithelial cells. Comparing with patients of COVID‐19 showing severe symptoms, the antigen processing and presentation pathway was increased and 12 typical genes, HLA‐DRB5, HLA‐DRB1, CD74, HLA‐DRA, HLA‐DPA1, HLA‐DQA1, HSP90AA1, HSP90AB1, HLA‐DPB1, HLA‐DQB1, HLA‐DQA2, and HLA‐DMA, particularly HLA‐DPB1, were obviously up‐regulated in ACE2‐positive bronchial epithelial cells of patients with mild disease. We further discovered SDCBP was positively correlated with above 12 genes particularly with HLA‐DPB1 in ACE2‐positive bronchial epithelial cells of COVID‐19 patients. Moreover, SDCBP may increase the immune infiltration of B cells, CD8+ T cells, CD4+ T cells, macrophages, neutrophils and dendritic cells in different lung carcinoma. Moreover, we found the expression of SDCBP was positively correlated with the expression of antigen processing and presentation genes in post‐mortem lung biopsies tissues, which is consistent with previous discoveries. These results suggest that SDCBP has good potential to be further developed as a novel diagnostic and therapeutic target in the treatment of COVID‐19.

Immunotherapies targeting stimulatory pathways and beyond

Co-stimulatory and co-inhibitory molecules play a critical role in T cell function. Tumor cells escape immune surveillance by promoting immunosuppression. Immunotherapy targeting inhibitory molecules like anti-CTLA-4 and anti-PD-1/PD-L1 were developed to overcome these immunosuppressive effects. These agents have demonstrated remarkable, durable responses in a small subset of patients. The other mechanisms for enhancing anti-tumor activities are to target the stimulatory pathways that are expressed on T cells or other immune cells. In this review, we summarize current phase I/II clinical trials evaluating novel immunotherapies targeting stimulatory pathways and outline their advantages, limitations, and future directions.

LIMIT is an immunogenic lncRNA in cancer immunity and immunotherapy

MHC-I presents tumor antigens to CD8⁺ T cells and triggers anti-tumor immunity. Humans may have 30,000-60,000 long noncoding RNAs (lncRNAs). However, it remains poorly understood whether lncRNAs may affect tumor immunity. Here, we identify a LncRNA, capable of Inducing MHC-I and Immunogenicity of Tumor (LIMIT) in humans and mice. We found IFNγ stimulated LIMIT, LIMIT cis-activated guanylate binding protein (GBP) gene cluster, and GBPs disrupted the association between HSP90 and heat shock factor-1 (HSF1) - thereby resulting in HSF1 activation and transcription of MHC-I machinery, but not PD-L1. RNA-guided CRISPR activation of LIMIT boosted GBPs and MHC-I, and potentiated tumor immunogenicity and checkpoint therapy. Silencing LIMIT, GBPs, and/or HSF1 diminished MHC-I, impaired antitumor immunity, and blunted immunotherapy efficacy. Clinically, LIMIT, GBPs- and HSF1-signaling transcripts and proteins correlated with MHC-I, tumor infiltrating T cells, and checkpoint blockade response in cancer patients. Altogether, we demonstrate LIMIT is a previously unknown cancer immunogenic lncRNA and the LIMIT-GBP-HSF1 axis may be targetable for cancer immunotherapy.

Heat Shock Proteins in Lymphoma Immunotherapy

Immunotherapy harnessing the host immune system for tumor destruction revolutionized oncology research and advanced treatment strategies for lymphoma patients. Lymphoma is a heterogeneous group of cancer, where the central roles in pathogenesis play immune evasion and dysregulation of multiple signaling pathways. Immunotherapy-based approaches such as engineered T cells (CAR T), immune checkpoint modulators and NK cell-based therapies are now in the frontline of lymphoma research. Even though emerging immunotherapies showed promising results in treating lymphoma patients, low efficacy and on-target/off-tumor toxicity are of a major concern. To address that issue it is suggested to look into the emerging role of heat shock proteins. Heat shock proteins (HSPs) showed to be highly expressed in lymphoma cells. HSPs are known for their abilities to modulate immune responses and inhibit apoptosis, which made their successful entry into cancer clinical trials. Here, we explore the role of HSPs in Hodgkin and Non-Hodgkin lymphoma and their involvement in CAR T therapy, checkpoint blockade and NK cell- based therapies. Understanding the role of HSPs in lymphoma pathogenesis and the ways how HSPs may enhance anti-tumor responses, may help in the development of more effective, specific and safe immunotherapy.

Heat Shock Protein-90 Inhibition Alters Activation of Pancreatic Stellate Cells and Enhances the Efficacy of PD-1 Blockade in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) has a prominent fibrotic stroma, which is a result of interactions between tumor, immune and pancreatic stellate cells (PSC), or cancer-associated fibroblasts (CAF). Targeting inflammatory pathways present within the stroma may improve access of effector immune cells to PDAC and response to immunotherapy. Heat shock protein-90 (Hsp90) is a chaperone protein and a versatile target in pancreatic cancer. Hsp90 regulates a diverse array of cellular processes of relevance to both the tumor and the immune system. However, to date the role of Hsp90 in PSC/CAF has not been explored in detail. We hypothesized that Hsp90 inhibition would limit inflammatory signals, thereby reprogramming the PDAC tumor microenvironment to enhance sensitivity to PD-1 blockade. Treatment of immortalized and primary patient PSC/CAF with the Hsp90 inhibitor XL888 decreased IL6, a key cytokine that orchestrates immune changes in PDAC at the transcript and protein level in vitro XL888 directly limited PSC/CAF growth and reduced Jak/STAT and MAPK signaling intermediates and alpha-SMA expression as determined via immunoblot. Combined therapy with XL888 and anti-PD-1 was efficacious in C57BL/6 mice bearing syngeneic subcutaneous (Panc02) or orthotopic (KPC-Luc) tumors. Tumors from mice treated with both XL888 and anti-PD-1 had a significantly increased CD8+ and CD4+ T-cell infiltrate and a unique transcriptional profile characterized by upregulation of genes associated with immune response and chemotaxis. These data demonstrate that Hsp90 inhibition directly affects PSC/CAF in vitro and enhances the efficacy of anti-PD-1 blockade in vivo.

Soluble PD-1: Predictive, Prognostic, and Therapeutic Value for Cancer Immunotherapy

Programmed death protein 1 (PD-1) interaction with PD-L1 deliver immunosuppressive environment for tumor growth, and its blockade with directed monoclonal antibodies (anti-PD-1/anti-PD-L1) has shown remarkable clinical outcome. Lately, their soluble counterparts, sPD-1 and sPD-L1, have been detected in plasma, and elevated levels have been associated with advanced disease, clinical stages, and worst prognosis for cancer patients. Elevated plasma levels of sPD-L1 have been correlated with worst prognosis in several studies and has displayed a persistent outlook. On the other hand, sPD-1 levels have been inconsistent in their predictive and prognostic ability. Pretherapeutic higher sPD-1 plasma levels have shown to predict advanced disease state and to a lesser extent worst prognosis. Any increase in sPD-1 plasma level post therapeutically have been correlated with improved survival for various cancers. In vitro and in vivo studies have shown sPD-1 ability to bind PD-L1 and PD-L2 and block PD-1/PD-L1 interaction. Local delivery of sPD-1 in cancer tumor microenvironment through local gene therapy have demonstrated an increase in tumor specific CD8+ T cell immunity and tumor growth reduction. It had also exhibited enhancement of T cell immunity induced by vaccination and other gene therapeutic agents. Furthermore, it may also lessen the inhibitory effect of circulating sPD-L1 and enhance the effects of mAb-based immunotherapy. In this review, we highlight various aspects of sPD-1 role in cancer prediction, prognosis, and anti-cancer immunity, as well as, its therapeutic value for local gene therapy or systemic immunotherapy in blocking the PD-1 and PD-L1 checkpoint interactions.

Increasing the efficiency of the retinoblastoma brachytherapy protocol with ultrasonic hyperthermia and gold nanoparticles: a rabbit model

PURPOSE

This study purposed to evaluate the efficacy of brachytherapy with the modality of ultrasonic hyperthermia in the presence of gold nanoparticles (GNPs) on an ocular retinoblastoma tumor in an animal model of the rabbit.

MATERIALS AND METHODS

A retinoblastoma tumor was induced by the injection of the human cell line of Y79 in rabbit eyes (n = 41). After two weeks, tumor size reached a diameter of about 5-7 mm. Seven groups were involved: control, GNPs injection, hyperthermia, hyperthermia with GNPs injection, brachytherapy with I-125, a combination of hyperthermia and brachytherapy, and a combination of brachytherapy, hyperthermia and, GNPs. The tumor area was measured using B-mode ultrasound images on the zero-day and at the end of the third week. The groups were evaluated for a histopathological study of tumor necrosis.

RESULTS

There was a significant difference between the relative area changes of tumor in the combination group with the other study groups (p < .05). The results of histopathologic studies confirmed the necrosis of living retinoblastoma cells.

CONCLUSION

Combination therapy of brachytherapy and hyperthermia with GNPs reduces the relative size of the tumor. This method increases the necrosis percentage of retinoblastoma and significantly reduces the retinoblastoma mass in the rabbit eyes.

Heat Shock Protein 90 Family Isoforms as Prognostic Biomarkers and Their Correlations with Immune Infiltration in Breast Cancer

Background

The heat shock protein 90 (HSP90s) family is composed of molecular chaperones composed of four isoforms in humans, which has been widely reported as unregulated in various kinds of cancers. Nevertheless, the role of each HSP90s isoform in prognosis and immune infiltration in distinct subtypes of breast cancer (BRAC) remains unclear.

Methods

Public online databases including the Oncomine, UALCAN, Kaplan-Meier Plotter, Tumor IMmune Estimation Resource (TIMER), Gene Expression Profiling Interactive Analysis (GEPIA), GeneMANIA, and Database for Annotation, Visualization, and Integrated Discovery (DAVID) were integrated to perform bioinformatic analyses and to explore the possible associations among HSP90s gene expression, prognosis, and immune infiltration in BRAC.

Results

The mRNA expression of all HSP90s members was elevated in distinct clinical stages and subtypes of BRAC, compared with the normal breast tissue (P < 0.05). Overexpressed HSP90AA1 was associated with poor prognosis, particularly, both short overall survival (OS) and release-free survival (RFS) in Basal-like BRAC patients; overexpressed HSP90AB1 and HSP90B1 were both associated with poor RFS in Luminal A BRAC patients, while overexpressed TRAP1 was associated with favorable RFS in Luminal A BRAC patients. Moreover, HSP90s gene expression in BRAC showed correlations with the infiltration of CD8+ T cells, neutrophils, macrophages, and dendritic cells (DCs), as well as the activation of tumor-associated macrophages (TAMs), DCs, and CD4+ helper T (Th) cells. The underlying mechanisms of HSP90s modulating tumor-infiltrating immune cells (TIICs) might be related with their functions in antigen processing and presentation, major histocompatibility complex (MHC) binding, and assisting client proteins.

Conclusion

This study demonstrated that HSP90s family genes were overexpressed and might be serve as prognostic biomarkers in subtypes of BRAC. It might be a novel breakthrough point of BRAC treatment to regulate immune infiltration in BRAC microenvironment for more effective anticancer immunity through pharmacological intervention of HSP90s.

Role of microenvironmental acidity and tumor exosomes in cancer immunomodulation

Tumor microenvironment (TME) is a complex milieu in which tumor grows, develops and progresses through a complex bi-directional cross-talk with immune-, stromal cells, and the extracellular matrix (ECM). In this context, tumor-derived exosomes (TE) drive the fate of tumor cells through a stimulatory or inhibitory role on immune system. In fact, TE can induce the apoptosis of cells of the immune surveillance, and enhance the proliferation and survival of stromal cells that sustain tumor development. However, depending on the molecular cargo, TE are also able to stimulate anti-tumor immune response. TME is mainly characterized by the acidic pH that contributes to tumor development, through multiple mechanisms. Among these, the impairment of tumor immune surveillance does occur within acidic TME, and is directly mediated by acidic pH or by molecular cargo carried by TE. Little is known about the role of TE in immunomodulation in acidic conditions. The present review summarizes the studies describing the role of microenvironmental acidity and TE in immune system modulation.

Dynamically Shaping Chaperones. Allosteric Modulators of HSP90 Family as Regulatory Tools of Cell Metabolism in Neoplastic Progression

Molecular chaperones have recently emerged as fundamental regulators of salient biological routines, including metabolic adaptations to environmental changes. Yet, many of the molecular mechanisms at the basis of their functions are still unknown or at least uncertain. This is in part due to the lack of chemical tools that can interact with the chaperones to induce measurable functional perturbations. In this context, the use of small molecules as modulators of protein functions has proven relevant for the investigation of a number of biomolecular systems. Herein, we focus on the functions, interactions and signaling pathways of the HSP90 family of molecular chaperones as possible targets for the discovery of new molecular entities aimed at tuning their activity and interactions. HSP90 and its mitochondrial paralog, TRAP1, regulate the activity of crucial metabolic circuitries, making cells capable of efficiently using available energy sources, with relevant implications both in healthy conditions and in a variety of disease states and especially cancer. The design of small-molecules targeting the chaperone cycle of HSP90 and able to inhibit or stimulate the activity of the protein can provide opportunities to finely dissect their biochemical activities and to obtain lead compounds to develop novel, mechanism-based drugs.

HSP90A inhibition promotes anti-tumor immunity by reversing multi-modal resistance and stem-like property of immune-refractory tumors

Cancer immunotherapy has emerged as a promising cancer treatment. However, the presence of immune-refractory tumor cells limits its clinical success by blocking amplification of anti-tumor immunity. Previously, we found that immune selection by immunotherapy drives the evolution of tumors toward multi-modal resistant and stem-like phenotypes via transcription induction of AKT co-activator TCL1A by NANOG. Here, we report a crucial role of HSP90A at the crossroads between NANOG-TCL1A axis and multi-aggressive properties of immune-edited tumor cells by identifying HSP90AA1 as a NANOG transcriptional target. Furthermore, we demonstrate that HSP90A potentiates AKT activation through TCL1A-stabilization, thereby contributing to the multi-aggressive properties in NANOG^high tumor cells. Importantly, HSP90 inhibition sensitized immune-refractory tumor to adoptive T cell transfer as well as PD-1 blockade, and re-invigorated the immune cycle of tumor-reactive T cells. Our findings implicate that the HSP90A-TCL1A-AKT pathway ignited by NANOG is a central molecular axis and a potential target for immune-refractory tumor.

Nanog can confer resistance to cancer immunotherapy by promoting AKT activity. Here, the authors demonstrate that HSP90A is a Nanog target that stabilizes the AKT coactivator TCL1, thereby activating AKT, and that HSP90A inhibition can enhance the anti-tumor efficacy of adoptive T cell transfer and checkpoint blockade.

Heat Shock Proteins in Cancer Immunotherapy

Heat shock proteins (HSPs) are highly conserved molecular chaperones with divergent roles in various cellular processes. The HSPs are classified according to their molecular size as HSP27, HSP40, HSP60, HSP70, and HSP90. The HSPs prevent nonspecific cellular aggregation of proteins by maintaining their native folding energetics. The disruption of this vital cellular process, driven by the aberrant expression of HSPs, is implicated in the progression of several different carcinomas. Many HSPs are also actively involved in promoting the proliferation and differentiation of tumor cells, contributing to their metastatic phenotype. Upregulation of these HSPs is associated with the poor outcome of anticancer therapy in clinical settings. On the other hand, these highly expressed HSPs may be exploited as viable immunotherapeutic targets for different types of cancers. This review discusses recent advances and perspectives on the research of HSP-based cancer immunotherapy.

Combination of Anti-Cancer Drugs with Molecular Chaperone Inhibitors

Most molecular chaperones belonging to heat shock protein (HSP) families are known to protect cancer cells from pathologic, environmental and pharmacological stress factors and thereby can hamper anti-cancer therapies. In this review, we present data on inhibitors of the heat shock response (particularly mediated by the chaperones HSP90, HSP70, and HSP27) either as a single treatment or in combination with currently available anti-cancer therapeutic approaches. An overview of the current literature reveals that the co-administration of chaperone inhibitors and targeting drugs results in proteotoxic stress and violates the tumor cell physiology. An optimal drug combination should simultaneously target cytoprotective mechanisms and trigger the imbalance of the tumor cell physiology.

Structure, Function, and Regulation of the Hsp90 Machinery

Heat shock protein 90 (Hsp90) is a molecular chaperone involved in the maturation of a plethora of substrates ("clients"), including protein kinases, transcription factors, and E3 ubiquitin ligases, positioning Hsp90 as a central regulator of cellular proteostasis. Hsp90 undergoes large conformational changes during its ATPase cycle. The processing of clients by cytosolic Hsp90 is assisted by a cohort of cochaperones that affect client recruitment, Hsp90 ATPase function or conformational rearrangements in Hsp90. Because of the importance of Hsp90 in regulating central cellular pathways, strategies for the pharmacological inhibition of the Hsp90 machinery in diseases such as cancer and neurodegeneration are being developed. In this review, we summarize recent structural and mechanistic progress in defining the function of organelle-specific and cytosolic Hsp90, including the impact of individual cochaperones on the maturation of specific clients and complexes with clients as well as ways of exploiting Hsp90 as a drug target.

Regulatory T cells in cancer immunosuppression - implications for anticancer therapy

Regulatory T (T_reg) cells, an immunosuppressive subset of CD4⁺ T cells characterized by the expression of the master transcription factor forkhead box protein P3 (FOXP3), are a component of the immune system with essential roles in maintaining self-tolerance. In addition, T_reg cells can suppress anticancer immunity, thereby hindering protective immunosurveillance of neoplasia and hampering effective antitumour immune responses in tumour-bearing hosts, thus promoting tumour development and progression. Identification of the factors that are specifically expressed in T_reg cells and/or that influence T_reg cell homeostasis and function is important to understanding cancer pathogenesis and to identifying therapeutic targets. Immune-checkpoint inhibitors (ICIs) have provided a paradigm shift in the treatment of cancer. Most immune-checkpoint molecules are expressed in T_reg cells, but the effects of ICIs on T_reg cells, and thus the contributions of these cells to treatment responses, remain unclear. Notably, evidence indicates that ICIs targeting programmed cell death 1 (PD-1) might enhance the immunosuppressive function of T_reg cells, whereas cytotoxic T lymphocyte antigen 4 (CTLA-4) inhibitors might deplete these cells. Thus, although manipulation of T_reg cells is a promising anticancer therapeutic strategy, approaches to controlling these cells require further research. Herein, we discuss novel insights into the roles of T_reg cells in cancer, which can hopefully be used to develop T_reg cell-targeted therapies and facilitate immune precision medicine.

Rebalancing Protein Homeostasis Enhances Tumor Antigen Presentation

PURPOSE

Despite the accumulation of extensive genomic alterations, many cancers fail to be recognized as "foreign" and escape destruction by the host immune system. Immunotherapies designed to address this problem by directly stimulating immune effector cells have led to some remarkable clinical outcomes, but unfortunately, most cancers fail to respond, prompting the need to identify additional immunomodulatory treatment options.Experimental Design: We elucidated the effect of a novel treatment paradigm using sustained, low-dose HSP90 inhibition in vitro and in syngeneic mouse models using genetic and pharmacologic tools. Profiling of treatment-associated tumor cell antigens was performed using immunoprecipitation followed by peptide mass spectrometry.

RESULTS

We show that sustained, low-level inhibition of HSP90 both amplifies and diversifies the antigenic repertoire presented by tumor cells on MHC-I molecules through an IFNγ-independent mechanism. In stark contrast, we find that acute, high-dose exposure to HSP90 inhibitors, the only approach studied in the clinic to date, is broadly immunosuppressive in cell culture and in patients with cancer. In mice, chronic non-heat shock-inducing HSP90 inhibition slowed progression of colon cancer implants, but only in syngeneic animals with intact immune function. Addition of a single dose of nonspecific immune adjuvant to the regimen dramatically increased efficacy, curing a subset of mice receiving combination therapy.

CONCLUSIONS

These highly translatable observations support reconsideration of the most effective strategy for targeting HSP90 to treat cancers and suggest a practical approach to repurposing current orally bioavailable HSP90 inhibitors as a new immunotherapeutic strategy.See related commentary by Srivastava and Callahan, p. 6277.

Combination therapies with HSP90 inhibitors against colorectal cancer

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

Prediction of Gold Nanoparticle and Microwave-Induced Hyperthermia Effects on Tumor Control via a Simulation Approach

Hyperthermia acts as a powerful adjuvant to radiation therapy and chemotherapy. Recent advances show that gold nanoparticles (Au-NPs) can mediate highly localized thermal effects upon interaction with laser radiation. The purpose of the present study was to investigate via in silico simulations the mechanisms of Au-NPs and microwave-induced hyperthermia, in correlation to predictions of tumor control (biological endpoints: tumor shrinkage and cell death) after hyperthermia treatment. We also study in detail the dependence of the size, shape and structure of the gold nanoparticles on their absorption efficiency, and provide general guidelines on how one could modify the absorption spectrum of the nanoparticles in order to meet the needs of specific applications. We calculated the hyperthermia effect using two types of Au-NPs and two types of spherical tumors (prostate and melanoma) with a radius of 3 mm. The plasmon peak for the 30 nm Si-core Au-coated NPs and the 20 nm Au-NPs was found at 590 nm and 540 nm, respectively. Considering the plasmon peaks and the distribution of NPs in the tumor tissue, the induced thermal profile was estimated for different intervals of time. Predictions of hyperthermic cell death were performed by adopting a three-state mathematical model, where “three-state” includes (i) alive, (ii) vulnerable, and (iii) dead states of the cell, and it was coupled with a tumor growth model. Our proposed methodology and preliminary results could be considered as a proof-of-principle for the significance of simulating accurately the hyperthermia-based tumor control involving the immune system. We also propose a method for the optimization of treatment by overcoming thermoresistance by biological means and specifically through the targeting of the heat shock protein 90 (HSP90), which plays a critical role in the thermotolerance of cells and tissues.

A study on the biological function of heat shock factor 1 proteins in breast cancer

The present study aimed to investigate the effect of HSF1 proteins on cell proliferation, apoptosis and invasion of breast cancer. The Michigan Cancer Foundation-7 (MCF-7) HSF1-knocked down stable cell line (experimental group) and control cell line (control group) were obtained using a lentivirus assay, and the effects of HSF1 knockdown on the proliferation, tumor formation, apoptosis and invasion ability were analyzed, respectively. The effects of HSF1 on downstream signals were analyzed using western blotting. Western blotting results showed that lentivirus successfully established a HSF1 knockdown stable cell line of MCF-7. Compared with the control group, the growth rate of MCF-7 cells in the experimental group was significantly decreased (P<0.05). Flow cytometry showed that the proportion of apoptosis in the control group was significantly lower than that of the experimental group (P<0.05). Notably, the invasion ability of cells in the control group was significantly higher than that in the experimental group (P<0.05). Compared with cells in the control group, the levels of heat shock protein (HSP)70, HSP90, anti-apoptotic protein B-cell lymphoma 2 (Bcl-2) and macrophage migration inhibitory factor (MIF) in the experimental group were significantly downregulated, whereas the level of Bax was significantly increased (P<0.05). In conclusion, HSF1 protein, as a transcription factor, regulates the expression levels of HSP70, HSP90, MIF, Bcl-2 and Bax, thus controlling the proliferation, apoptosis and invasion of cells. These findings suggest HSF1 protein as a potential target for the treatment of breast cancer.

Methods to validate Hsp90 inhibitor specificity, to identify off-target effects, and to rethink approaches for further clinical development

The molecular chaperone Hsp90 is one component of a highly complex and interactive cellular proteostasis network (PN) that participates in protein folding, directs misfolded and damaged proteins for destruction, and participates in regulating cellular transcriptional responses to environmental stress, thus promoting cell and organismal survival. Over the last 20 years, it has become clear that various disease states, including cancer, neurodegeneration, metabolic disorders, and infection by diverse microbes, impact the PN. Among PN components, Hsp90 was among the first to be pharmacologically targeted with small molecules. While the number of Hsp90 inhibitors described in the literature has dramatically increased since the first such small molecule was described in 1994, it has become increasingly apparent that not all of these agents have been sufficiently validated for specificity, mechanism of action, and lack of off-target effects. Given the less than expected activity of Hsp90 inhibitors in cancer-related human clinical trials, a re-evaluation of potentially confounding off-target effects, as well as confidence in target specificity and mechanism of action, is warranted. In this commentary, we provide feasible approaches to achieve these goals and we discuss additional considerations to improve the clinical efficacy of Hsp90 inhibitors in treating cancer and other diseases.

A study on the biological function of heat shock factor 1 proteins in breast cancer

The present study aimed to investigate the effect of HSF1 proteins on cell proliferation, apoptosis and invasion of breast cancer. The Michigan Cancer Foundation-7 (MCF-7) HSF1-knocked down stable cell line (experimental group) and control cell line (control group) were obtained using a lentivirus assay, and the effects of HSF1 knockdown on the proliferation, tumor formation, apoptosis and invasion ability were analyzed, respectively. The effects of HSF1 on downstream signals were analyzed using western blotting. Western blotting results showed that lentivirus successfully established a HSF1 knockdown stable cell line of MCF-7. Compared with the control group, the growth rate of MCF-7 cells in the experimental group was significantly decreased (P<0.05). Flow cytometry showed that the proportion of apoptosis in the control group was significantly lower than that of the experimental group (P<0.05). Notably, the invasion ability of cells in the control group was significantly higher than that in the experimental group (P<0.05). Compared with cells in the control group, the levels of heat shock protein (HSP)70, HSP90, anti-apoptotic protein B-cell lymphoma 2 (Bcl-2) and macrophage migration inhibitory factor (MIF) in the experimental group were significantly downregulated, whereas the level of Bax was significantly increased (P<0.05). In conclusion, HSF1 protein, as a transcription factor, regulates the expression levels of HSP70, HSP90, MIF, Bcl-2 and Bax, thus controlling the proliferation, apoptosis and invasion of cells. These findings suggest HSF1 protein as a potential target for the treatment of breast cancer.

Targeted cancer therapy through 17-DMAG as an Hsp90 inhibitor: Overview and current state of the art

Heat shock protein 90 (Hsp90) is an evolutionary preserved molecular chaperone which mediates many cellular processes such as cell transformation, proliferation, and survival in normal and stress conditions. Hsp90 plays an important role in folding, maturation, stabilization and activation of Hsp90 client proteins which all contribute to the development, and proliferation of cancer as well as other inflammatory diseases. Functional inhibition of Hsp90 can have a massive effect on various oncogenic and inflammatory pathways, and will result in the degradation of their client proteins. This turns it into an interesting target in the treatment of different malignancies. 17-dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG) as a semi-synthetic derivative of geldanamycin, has several advantages over 17-Allylamino-17-demethoxygeldanamycin (17-AAG) such as higher water solubility, good bioavailability, reduced metabolism, and greater anti-tumour capability. 17-DMAG binds to the Hsp90, and inhibits its function which eventually results in the degradation of Hsp90 client proteins. Here, we reviewed the pre-clinical data and clinical trial data on 17-DMAG as a single agent, in combination with other agents and loaded on nanomaterials in various cancers and inflammatory diseases.

HSP90 inhibition enhances cancer immunotherapy by upregulating interferon response genes

T-cell-based immunotherapies are promising treatments for cancer patients. Although durable responses can be achieved in some patients, many patients fail to respond to these therapies, underscoring the need for improvement with combination therapies. From a screen of 850 bioactive compounds, we identify HSP90 inhibitors as candidates for combination with immunotherapy. We show that inhibition of HSP90 with ganetespib enhances T-cell-mediated killing of patient-derived human melanoma cells by their autologous T cells in vitro and potentiates responses to anti-CTLA4 and anti-PD1 therapy in vivo. Mechanistic studies reveal that HSP90 inhibition results in upregulation of interferon response genes, which are essential for the enhanced killing of ganetespib treated melanoma cells by T cells. Taken together, these findings provide evidence that HSP90 inhibition can potentiate T-cell-mediated anti-tumor immune responses, and rationale to explore the combination of immunotherapy and HSP90 inhibitors.

Many patients fail to respond to T cell based immunotherapies. Here, the authors, through a high-throughput screening, identify HSP90 inhibitors as a class of preferred drugs for treatment combination with immunotherapy.

BIIB021: A novel inhibitor to heat shock protein 90–addicted oncology

Heat shock protein 90 is induced in response to the cell stress. Its overexpression has been reported in many cancers with poor prognosis. It acts as a chaperone to the client proteins, especially the activated oncoproteins in malignancies to protect them from degradation. Heat shock protein 90 inhibition represented anti-cancer effects in many studies. Previous natural product–based compounds are limited by their association with target toxicities. BIIB021 is an orally available, fully synthetic novel small-molecule heat shock protein 90 inhibitor that has shown strong antitumor activities in a large number of preclinical models and is now under clinical investigation. This review will summarize its therapeutic effects and highlight the prospect of targeting heat shock protein 90 in the cancer therapy.

Heat Shock Protein 90 Modulates Lipid Homeostasis by Regulating the Stability and Function of Sterol Regulatory Element-binding Protein (SREBP) and SREBP Cleavage-activating Protein

Sterol regulatory element-binding proteins (SREBPs) are the key transcription factors that modulate lipid biosynthesis. SREBPs are synthesized as endoplasmic reticulum-bound precursors that require proteolytic activation in the Golgi apparatus. The stability and maturation of precursor SREBPs depend on their binding to SREBP cleavage-activating protein (SCAP), which escorts the SCAP-SREBP complex to the Golgi apparatus. In this study, we identified heat shock protein (HSP) 90 as a novel SREBP regulator that binds to and stabilizes SCAP-SREBP. In HepG2 cells, HSP90 inhibition led to proteasome-dependent degradation of SCAP-SREBP, which resulted in the down-regulation of SREBP target genes and the reduction in intracellular triglyceride and cholesterol levels. We also demonstrated in vivo that HSP90 inhibition decreased SCAP-SREBP protein, down-regulated SREBP target genes, and reduced lipids levels in mouse livers. We propose that HSP90 plays an indispensable role in SREBP regulation by stabilizing the SCAP-SREBP complex, facilitating the activation of SREBP to maintain lipids homeostasis.

TC-N19, a novel dual inhibitor of EGFR and cMET, efficiently overcomes EGFR-TKI resistance in non-small-cell lung cancer cells

Epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) show a clinical benefit when used to treat patients with EGFR-mutated non-small-cell lung cancer (NSCLC), but this treatment unfortunately fails in patients with TKI-resistant tumors. We here provide evidence that TC-N19 (N19), a novel dual inhibitor of EGFR and cMET, efficiently overcomes the EGFR-TKI resistance in EGFR-mutated NSCLC cells via simultaneous degradation of both proteins by ubiquitin proteasomes. Comparison with HSP90 inhibitor treatment and knockdown of EGFR and cMET by small hairpin RNAs reveal that the reduction of EGFR and cMET expression by N19 is responsible for overcoming the intrinsic TKI resistance mediated by paxillin (PXN) in high PXN-expressing cells, PXN-overexpressing PC9 cells (PC9-PXN), the EGFR-T790M-mediated TKI resistance in H1975 and CL97 cells, and the acquired resistance to gefitinib in gefitinib-resistant PC9 cells (PC9GR). Annexin V-PI staining assay showed that the induction of apoptosis in NSCLC cells by N19 depended on the reduction in levels of both proteins. Xenograft tumor formation in nude mice induced by a PC9-PXN-stable clone and by PC9GR cells was nearly completely suppressed by N19 treatment, with no changes in animal body weight. MTT assays of normal lung cells and reticulocytes showed no cytotoxicity responses to N19. In summary, N19 may act as a novel dual inhibitor of EGFR and cMET that induces apoptosis in TKI-resistant EGFR-mutated NSCLC cells and suppresses xenograft tumor formation. We suggest that N19 may be a potential new-generation TKI or HSP90 inhibitor used for treatment of NSCLC patients who show resistance to current TKI-targeting therapies.

Ethoxyquin provides neuroprotection against cisplatin-induced neurotoxicity

Ethoxyquin was recently identified as a neuroprotective compound against toxic neuropathies and efficacy was demonstrated against paclitaxel-induced neurotoxicity in vivo. In this study we examined the efficacy of ethoxyquin in preventing neurotoxicity of cisplatin in rodent models of chemotherapy-induced peripheral neuropathy and explored its mechanism of action. Ethoxyquin prevented neurotoxicity of cisplatin in vitro in a sensory neuronal cell line and primary rat dorsal root ganglion neurons. In vivo, chronic co-administration of ethoxyquin partially abrogated cisplatin-induced behavioral, electrophysiological and morphological abnormalities. Furthermore, ethoxyquin did not interfere with cisplatin's ability to induce tumor cell death in ovarian cancer cell line in vitro and in vivo. Finally, ethoxyquin reduced the levels of two client proteins (SF3B2 and ataxin-2) of a chaperone protein, heat shock protein 90 (Hsp90) when co-administered with cisplatin in vitro. These results implied that the neuroprotective effect of ethoxyquin is mediated through these two client proteins of Hsp90. In fact, reducing levels of SF3B2 in tissue-cultured neurons was effective against neurotoxicity of cisplatin. These findings suggest that ethoxyquin or other compounds that inhibit chaperone activity of Hsp90 and reduce levels of its client protein, SF3B2 may be developed as an adjuvant therapy to prevent neurotoxicity in cisplatin-based chemotherapy protocols.

Hsp90: A New Player in DNA Repair?

Heat shock protein 90 (Hsp90) is an evolutionary conserved molecular chaperone that, together with Hsp70 and co-chaperones makes up the Hsp90 chaperone machinery, stabilizing and activating more than 200 proteins, involved in protein homeostasis (i.e., proteostasis), transcriptional regulation, chromatin remodeling, and DNA repair. Cells respond to DNA damage by activating complex DNA damage response (DDR) pathways that include: (i) cell cycle arrest; (ii) transcriptional and post-translational activation of a subset of genes, including those associated with DNA repair; and (iii) triggering of programmed cell death. The efficacy of the DDR pathways is influenced by the nuclear levels of DNA repair proteins, which are regulated by balancing between protein synthesis and degradation as well as by nuclear import and export. The inability to respond properly to either DNA damage or to DNA repair leads to genetic instability, which in turn may enhance the rate of cancer development. Multiple components of the DNA double strand breaks repair machinery, including BRCA1, BRCA2, CHK1, DNA-PKcs, FANCA, and the MRE11/RAD50/NBN complex, have been described to be client proteins of Hsp90, which acts as a regulator of the diverse DDR pathways. Inhibition of Hsp90 actions leads to the altered localization and stabilization of DDR proteins after DNA damage and may represent a cell-specific and tumor-selective radiosensibilizer. Here, the role of Hsp90-dependent molecular mechanisms involved in cancer onset and in the maintenance of the genome integrity is discussed and highlighted.