Mitochondrial Hsp90s suppress calcium-mediated stress signals propagating from mitochondria to the ER in cancer cells

Endothelial Unfolded Protein Response-Mediated Cytoskeletal Effects

The endothelial semipermeable monolayers ensure tissue homeostasis, are subjected to a plethora of stimuli, and their function depends on cytoskeletal integrity and remodeling. The permeability of those membranes can fluctuate to maintain organ homeostasis. In cases of severe injury, inflammation or disease, barrier hyperpermeability can cause irreparable damage of endothelium-dependent issues, and eventually death. Elucidation of the signaling regulating cytoskeletal structure and barrier integrity promotes the development of targeted pharmacotherapies towards disorders related to the impaired endothelium (e.g., acute respiratory distress syndrome, sepsis). Recent reports investigate the role of unfolded protein response in barrier function. Herein we review the cytoskeletal components, the unfolded protein response function; and their interrelations on health and disorder. Moreover, we emphasize on unfolded protein response modulators, since they ameliorate illness related to endothelial leak.

Litopenaeus vannamei heat shock protein 90 (LvHSP90) interacts with white spot syndrome virus protein, WSSV322, to modulate hemocyte apoptosis during viral infection

As cellular chaperones, heat shock protein can facilitate viral infection in different steps of infection process. Previously, we have shown that the suppression of Litopenaeus vannamei (Lv)HSP90 not only results in a decline of white spot syndrome virus (WSSV) infection but also induces apoptosis in shrimp hemocyte cells. However, the mechanism underlying how LvHSP90 involved in WSSV infection remains largely unknown. In this study, a yeast two-hybrid assay and co-immunoprecipitation revealed that LvHSP90 interacts with the viral protein WSSV322 which function as an anti-apoptosis protein. Recombinant protein (r) LvHSP90 and rWSSV322 inhibited cycloheximide-induced hemocyte cell apoptosis in vitro. Co-silencing of LvHSP90 and WSSV322 in WSSV-infected shrimp led to a decrease in expression level of viral replication marker genes (VP28, ie-1) and WSSV copy number, while caspase 3/7 activity was noticeably induced. The number of apoptotic cells, confirmed by Hoechst 33342 staining assay and annexin V/PI staining, was significantly higher in LvHSP90 and WSSV322 co-silenced-shrimp than the control groups. Moreover, the co-silencing of LvHSP90 and WSSV322 triggered apoptosis by the mitochondrial pathway, resulting in the upregulation of pro-apoptotic protein expression (bax) and the downregulation of anti-apoptotic protein expression (bcl, Akt). This process also involved the release of cytochrome c (CytC) from the mitochondria and a decrease in mitochondrial membrane potential (MMP). These findings suggest that LvHSP90 interacts with WSSV322 to facilitate viral replication by inhibiting host apoptosis during WSSV infection.

Targeting the Mitochondrial Chaperone TRAP1 Alleviates Vascular Pathologies in Ischemic Retinopathy

Activation of hypoxia-inducible factor 1α (HIF1α) contributes to blood-retinal barrier (BRB) breakdown and pathological neovascularization responsible for vision loss in ischemic retinal diseases. During disease progression, mitochondrial biology is altered to adapt to the ischemic environment created by initial vascular dysfunction, but the mitochondrial adaptive mechanisms, which ultimately contribute to the pathogenesis of ischemic retinopathy, remain incompletely understood. In the present study, it is identified that expression of mitochondrial chaperone tumor necrosis factor receptor-associated protein 1 (TRAP1) is essential for BRB breakdown and pathologic retinal neovascularization in mouse models mimicking ischemic retinopathies. Genetic Trap1 ablation or treatment with small molecule TRAP1 inhibitors, such as mitoquinone (MitoQ) and SB-U015, alleviate retinal pathologies via proteolytic HIF1α degradation, which is mediated by opening of the mitochondrial permeability transition pore and activation of calcium-dependent protease calpain-1. These findings suggest that TRAP1 can be a promising target for the development of new treatments against ischemic retinopathy, such as retinopathy of prematurity and proliferative diabetic retinopathy.

The development of cancers research based on mitochondrial heat shock protein 90

Mitochondrial heat shock protein 90 (mtHsp90), including Tumor necrosis factor receptor-associated protein 1 (TRAP1) and Hsp90 translocated from cytoplasm, modulating cellular metabolism and signaling pathways by altering the conformation, activity, and stability of numerous client proteins, and is highly expressed in tumors. mtHsp90 inhibition results in the destabilization and eventual degradation of its client proteins, leading to interference with various tumor-related pathways and efficient control of cancer cell development. Among these compounds, gamitrinib, a specific mtHsp90 inhibitor, has demonstrated its safety and efficacy in several preclinical investigations and is currently undergoing evaluation in clinical trials. This review aims to provide a comprehensive overview of the present knowledge pertaining to mtHsp90, encompassing its structure and function. Moreover, our main emphasis is on the development of mtHsp90 inhibitors for various cancer therapies, to present a thorough overview of the recent pre-clinical and clinical advancements in this field.

Integrated bioinformatics and network pharmacology to explore the therapeutic target and molecular mechanisms of Taxus chinensis against non-small cell lung cancer

Taxus chinensis (TC) has tremendous therapeutic potential in alleviating non-small cell lung cancer (NSCLC), but the mechanism of action of TC remains unclear. Integrated bioinformatics and network pharmacology were employed in this study to explore the potential targets and molecular mechanism of TC against NSCLC. Data obtained from public databases were combined with appropriate bioinformatics tools to identify the common targets for TC and NSCLC. Common targets were uploaded to the Metascape database for gene ontology terms and Kyoto Encyclopedia of Genes and Genomes pathway analyses. A protein-protein interaction network was established, and topological analysis was performed to obtain hub genes. The expression of the hub genes in NSCLC tissues and their consequent effects on the prognosis of patients with NSCLC were confirmed using the Human Protein Atlas database and appropriate bioinformatics tools. Molecular docking was used to verify the binding affinity between the active ingredients and hub targets. We found 401 common targets that were significantly enriched in the cancer, MAPK signaling, and PI3K/Akt signaling pathways. Proto-oncogene tyrosine-protein kinase Src (SRC), mitogen-activated protein kinase 1, phosphoinositide-3-kinase, regulatory subunit 1 (PIK3R1), AKT serine/threonine kinase 1 (AKT1), phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), and lymphocyte-specific protein tyrosine kinase were identified as the hub genes. Immunohistochemical results confirmed that the expression of SRC, mitogen-activated protein kinase 1, PIK3R1, AKT1, and phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha was upregulated in the NSCLC tissues, while survival analysis revealed the expression of SRC, AKT1, PIK3R1, and lymphocyte-specific protein tyrosine kinase was closely related to the prognosis of patients with NSCLC. Molecular docking results confirmed all bioactive ingredients present in TC strongly bound to hub targets. We concluded that TC exhibits an anti-NSCLC role through multi-target combination and multi-pathway cooperation.

Hsp90 is a potential risk factor for ovarian cancer prognosis: an evidence of a Chinese clinical center

BACKGROUND

The potential treatment effects of heat shock protein 90 (Hsp90) inhibitors in ovarian cancer (OC) are controversial. This research aims to investigate the relationship between the level of Hsp90 in peripheral blood and the prognosis of OC patients, as well as the clinicopathological indicators.

MATERIALS AND METHODS

We retrospectively collected the clinicopathological indicators of OC patients who were admitted to the Department of Obstetrics and Gynecology of the First Affiliated Hospital of Anhui Medical University from 2017 to 2022. Hsp90 level in patient blood was detected by enzyme-linked immunosorbent assay, and the correlation between Hsp90 level and OC prognosis was systematically investigated. Kaplan-Meier method was used to draw the survival curve, and the average survival time and survival rate were calculated. The log-rank test and Cox model were used for univariate survival analysis, and the Cox proportional hazards model was applied for multivariate survival analysis. Based on the TCGA dataset of OC obtained by cBioPortal, Pearson's correlation coefficients between Hsp90 level values and other mRNA expression values were calculated to further conduct bioinformatics analysis. GSEA and GSVA analysis were also conducted for gene functional enrichment. The expression of Hsp90 in OC tissues were evaluated and compared by Immunohistochemical staining.

RESULTS

According to the established screening criteria, 106 patients were selected. The enzyme-linked immunosorbent assay results showed that 50.94% OC patients with abnormal Hsp90 level. According to the outcome of Kaplan-Meier curves, the results revealed that the abnormal level of Hsp90 was suggested to poor prognosis (P = 0.001) of OC patients. Furthermore, the result of multivariate Cox proportional hazards regression model analysis also predicted that abnormal Hsp90 level (HR = 2.838, 95%CI = 1.139-7.069, P = 0.025) was linked to poor prognosis, which could be an independent prognostic factor for the prognosis of OC patients. Moreover, top 100 genes screened by Pearson's value associated with Hsp90, indicating that Hsp90 participated in the regulation of ATF5 target genes, PRAGC1A target genes and BANP target genes and also enriched in the metabolic processes of cell response to DNA damage stimulus, response to heat and protein folding.

CONCLUSION

Hsp90 level is positively associated with OC mortality and is a potential prognostic indicator of OC.

The Influence of Mitochondrial Energy and 1C Metabolism on the Efficacy of Anticancer Drugs: Exploring Potential Mechanisms of Resistance

Mitochondria are the main energy factory in living cells. To rapidly proliferate and metastasize, neoplastic cells increase their energy requirements. Thus, mitochondria become one of the most important organelles for them. Indeed, much research shows the interplay between cancer chemoresistance and altered mitochondrial function. In this review, we focus on the differences in energy metabolism between cancer and normal cells to better understand their resistance and how to develop drugs targeting energy metabolism and nucleotide synthesis. One of the differences between cancer and normal cells is the higher nicotinamide adenine dinucleotide (NAD+) level, a cofactor for the tricarboxylic acid cycle (TCA), which enhances their proliferation and helps cancer cells survive under hypoxic conditions. An important change is a metabolic switch called the Warburg effect. This effect is based on the change of energy harvesting from oxygen-dependent transformation to oxidative phosphorylation (OXPHOS), adapting them to the tumor environment. Another mechanism is the high expression of one-carbon (1C) metabolism enzymes. Again, this allows cancer cells to increase proliferation by producing precursors for the synthesis of nucleotides and amino acids. We reviewed drugs in clinical practice and development targeting NAD+, OXPHOS, and 1C metabolism. Combining novel drugs with conventional antineoplastic agents may prove to be a promising new way of anticancer treatment.

Structure, Function, and Inhibitors of the Mitochondrial Chaperone TRAP1

Tumor necrosis factor receptor-associated protein 1 (TRAP1) is a mitochondrial molecular chaperone modulating cellular metabolism and signaling pathways by altering the conformation, activity, and stability of numerous substrate proteins called clients. It exerts its chaperone function as an adaptive response to counter cellular stresses instead of maintaining housekeeping protein homeostasis. However, the stress-adaptive machinery becomes dysregulated to support the progression and maintenance of human diseases, such as cancers; therefore, TRAP1 has been proposed as a promising target protein for anticancer drug development. In this review, by collating recent reports on high-resolution TRAP1 structures and structure-activity relationships of inhibitors, we aimed to provide better insights into the chaperoning mechanism of the emerging drug target and to suggest an efficient strategy for the development of potent TRAP1 inhibitors.

FAM172A supervises ER (endoplasmic reticulum) stress-triggered autophagy in the epidural fibrosis process

Backgrounds

Lumbar laminectomy is usually utilized for lumbar disc herniation (LDH), but also causes epidural fibrosis (EF) process associated with abnormal proliferation of fibroblasts. FAM172A is associated with ER stress and cell proliferation, but its mechanism was unclear, especially in the process of EF.

Methods

Therefore, the regulation of FAM172A on the calcium flux and autophagy in fibroblasts were investigated by inducing ER stress with tunicamycin and upexpression or downexpression of FAM172A. The calcium flux was determined using Fluo-3, and autophagy was examined with immunofluorescence or western blot for LC3, Beclin-1, ATG-5, and p62. Moreover, the apoptotic protein of Bax and Bcl-2 was detected, too. Furthermore, the laminectomy model was constructed and then dealt with overexpression of FAM172A.

Results

Tunicamycin-induced endoplasmic reticulum (ER) stress and autophagy process in fibroblasts were associated with the calcium flux regulated by FAM172A, especially in EF cells. Besides, tunicamycin induced autophagy and suppressed cell apoptosis of fibroblasts. Furthermore, FAM72A repressed the proliferation of fibroblasts and the process of EF in the laminectomy model through the mediation of the autophagy process.

Conclusions

Tunicamycin-induced endoplasmic reticulum (ER) stress in fibroblasts was associated with calcium flux mediated by FAM172A. FAM72A participated in the autophagy regulation of fibroblasts and maybe the key interaction regulator of apoptosis and autophagy in fibroblasts, especially for epidural scar cells.

Geraniol and Citral as potential therapeutic agents targeting the HSP90 activity: An in silico and experimental approach

Lemongrass essential oil has antifungal and anti-cancerous properties. Heat-shock protein (HSP90), an ATP-dependent molecular chaperone found in eukaryotes, is involved in protein folding, stability, and disease, making it a promising research topic. Both in silico and in vitro approaches were used to provide a clear insight into the HSP90-ATPase 3D structures, activity, and their interaction with the essential oil constituents among various species such as fungi (S. cerevisiae), parasites (P. falciparum), and humans. For in silico studies, sequence alignment, docking (AutoDock), and absorption, distribution, metabolism, and excretion (ADME) properties were evaluated to obtain hit compounds specifically against each HSP90-ATPase. The hit compounds obtained were evaluated for their efficacy in the in vitro studies of S. cerevisiae. In vitro studies were carried out targeting HSP90-ATPases via lemongrass essential oil components individually and in combination as a function of concentration and various salt concentrations. Results suggest that sequence alignment exists of over 75% among these three species. The best docking score was possessed by Geraniol and its constituent (geldanamycin ≥ -4.93 kcal/mol) (a known antifungal and antitumor against HSP90) in all the above species. Lemongrass oil and the combination of Geraniol and Citral at concentrations of 80 μg/mL showed the maximum inhibition of ATPase and HSP90-ATPase activity compared to their individual treatment. Therefore, both in silico and in vitro studies provide clear evidence of specific inhibitory action of lemongrass oil, Geraniol, and Citral against the ATPase and HSP90-ATPase activities and might show potential as antifungal and antitumor drugs.

Commentary on: Xbp1s-Ddit3, DNA damage and pulmonary hypertension

In this commentary, we discuss new observations stating that spliced X-box-binding protein 1 (Xbp1s)-DNA damage-inducible transcript 3 (Ddit3) promotes monocrotaline (MCT)-induced pulmonary hypertension (Jiang et al., Clinical Science (2021) 135(21), https://doi.org/10.1042/CS20210612). Xbp1s-Ddit3 is involved in the regulation of endoplasmic reticulum stress but is also associated with DNA damage repair machinery. Pathologic DNA damage repair mechanisms have emerged as critical determinants of pulmonary hypertension development. We discuss the potential relationship among Xbp1s-Ddit3, DNA damage, and pulmonary hypertension. Although Xbp1s-Ddit3 contributes to the regulation of cell proliferation and apoptosis and the development of vascular lesions, whether Xbp1s is a friend or foe remains controversial.

Mitoquinone Inactivates Mitochondrial Chaperone TRAP1 by Blocking the Client Binding Site

Heat shock protein 90 (Hsp90) family proteins are molecular chaperones that modulate the functions of various substrate proteins (clients) implicated in pro-tumorigenic pathways. In this study, the mitochondria-targeted antioxidant mitoquinone (MitoQ) was identified as a potent inhibitor of mitochondrial Hsp90, known as a tumor necrosis factor receptor-associated protein 1 (TRAP1). Structural analyses revealed an asymmetric bipartite interaction between MitoQ and the previously unrecognized drug binding sites located in the middle domain of TRAP1, believed to be a client binding region. MitoQ effectively competed with TRAP1 clients, and MitoQ treatment facilitated the identification of 103 TRAP1-interacting mitochondrial proteins in cancer cells. MitoQ and its redox-crippled SB-U014/SB-U015 exhibited more potent anticancer activity in vitro and in vivo than previously reported mitochondria-targeted TRAP1 inhibitors. The findings indicate that targeting the client binding site of Hsp90 family proteins offers a novel strategy for the development of potent anticancer drugs.

Computational Approaches for the Design of Novel Anticancer Compounds Based on Pyrazolo[3,4-d]pyrimidine Derivatives as TRAP1 Inhibitor

In the present in-silico study, various computational techniques were applied to determine potent compounds against TRAP1 kinase. The pharmacophore hypothesis DHHRR_1 consists of important features required for activity. The 3D QSAR study showed a statistically significant model with R² = 0.96 and Q² = 0.57. Leave one out (LOO) cross-validation (R² CV = 0.58) was used to validate the QSAR model. The molecular docking study showed maximum XP docking scores (−11.265, −10.532, −10.422, −10.827, −10.753 kcal/mol) for potent pyrazole analogs (42, 46, 49, 56, 43), respectively, with significant interactions with amino acid residues (ASP 594, CYS 532, PHE 583, SER 536) against TRAP1 kinase receptors (PDB ID: 5Y3N). Furthermore, the docking results were validated using the 100 ns MD simulations performed for the selected five docked complexes. The selected inhibitors showed relatively higher binding affinities than the TRAP1 inhibitor molecules present in the literature. The ZINC database was used for a virtual screening study that screened ZINC05297837, ZINC05434822, and ZINC72286418, which showed similar binding interactions to those shown by potent ligands. Absorption, distribution, metabolism, and excretion (ADME) analysis showed noticeable results. The results of the study may be helpful for the further development of potent TRAP1 inhibitors

Design and Synthesis of TRAP1 Selective Inhibitors: H-Bonding with Asn171 Residue in TRAP1 Increases Paralog Selectivity

Tumor necrosis factor receptor-associated protein 1 (TRAP1) is overexpressed in the mitochondria of various cancer cells, reprograms cellular metabolism to enable cancer cells to adapt to harsh tumor environments. As inactivation of TRAP1 induces massive apoptosis in cancer cells in vitro and in vivo, the development of TRAP1-selective inhibitors has become an attractive approach. A series of purine-8-one and pyrrolo[2,3-d]pyrimidine derivatives was developed based on TRAP1 structure and identified to be highly selective in vitro for TRAP1 over the paralogous enzymes, Hsp90α and Grp94. The TRAP1-selective inhibition strategy via utilization of the Asn171 residue of the ATP-lid was investigated using X-ray crystallography and molecular dynamics simulation studies. Among various synthesized potent TRAP1 inhibitors, 5f possessed a 65-fold selectivity over Hsp90α and a 13-fold selectivity over Grp94. Additionally, 6f had a half-maximal inhibitory concentration (IC₅₀) of 63.5 nM for TRAP1, with a 78-fold and 30-fold selectivity over Hsp90α and Grp94, respectively.

Development of pyrazolo[3,4-d]pyrimidine-6-amine-based TRAP1 inhibitors that demonstrate in vivo anticancer activity in mouse xenograft models

TNF Receptor Associated Protein 1 (TRAP1) is a mitochondrial paralog of Hsp90 related to the promotion of tumorigenesis in various cancers via maintaining mitochondrial integrity, reducing the production of reactive oxygen species, and reprogramming cellular metabolism. Consequently, Hsp90 and TRAP1 have been targeted to develop cancer therapeutics. Herein, we report a series of pyrazolo[3,4-d]pyrimidine derivatives that are mitochondria-permeable TRAP1 inhibitors. Structure-based drug design guided the optimization of potency, leading to the identification of compounds 47 and 48 as potent TRAP1 and Hsp90 inhibitors with good metabolic and plasma stability as well as acceptable CYP and hERG inhibition. X-ray co-crystallization studies confirmed both 47 and 48 interact with the ATP binding pocket in the TRAP1 protein. Compounds 47 and 48 demonstrated excellent anticancer efficiency in various cancer cells, with limited toxicity over normal hepatocyte and prostate cells. Mouse PC3 xenograft studies showed 47 and 48 significantly reduced tumor growth.

Enzyme-Instructed Assemblies Enable Mitochondria Localization of Histone H2B in Cancer Cells

Presently, little is known of how the inter-organelle crosstalk impacts cancer cells owing to the lack of approaches that can manipulate inter-organelle communication in cancer cells. We found that a negatively charged, enzyme cleavable peptide (MitoFlag) enables the trafficking of histone protein H2B, a nuclear protein, to the mitochondria in cancer cells. MitoFlag interacts with the nuclear location sequence of H2B to block it from entering the nucleus. A protease on the mitochondria cleaves the Flag from the MitoFlag/H2B complex to form assemblies that retain H2B on the mitochondria and facilitate H2B entering the mitochondria. Adding NLS, replacing aspartic acid by glutamic acid residues, or changing the l- to d-aspartic acid residue on MitoFlag abolishes the trafficking of H2B into mitochondria of HeLa cells. As the first example of the enzyme-instructed self-assembly of a synthetic peptide for trafficking endogenous proteins, this work provides insights for understanding and manipulating inter-organelle communication in cells.

The Role of Vitamin D and Sunlight Incidence in Cancer

BACKGROUND

Vitamin D (VD) deficiency affects individuals of different ages in many countries. VD deficiency may be related to several diseases, including cancer.

OBJECTIVE

This study aimed to review the relationship between VD deficiency and cancer.

METHODS

We describe the proteins involved in cancer pathogenesis and how those proteins can be influenced by VD deficiency. We also investigated a relationship between cancer death rate and solar radiation.

RESULTS

We found an increased bladder cancer, breast cancer, colon-rectum cancer, lung cancer, oesophagus cancer, oral cancer, ovary cancer, pancreas cancer, skin cancer and stomach cancer death rate in countries with low sunlight. It was also observed that amyloid precursor protein, ryanodine receptor, mammalian target of rapamycin complex 1, and receptor for advanced glycation end products are associated with a worse prognosis in cancer. While the Klotho protein and VD receptor are associated with a better prognosis in the disease. Nfr2 is associated with both worse and better prognosis in cancer.

CONCLUSION

The literature suggests that VD deficiency might be involved in cancer progression. According to sunlight data, we can conclude that countries with low average sunlight have high cancers death rate. New studies involving transcriptional and genomic data in combination with VD measurement in long-term experiments are required to establish new relationships between VD and cancer.

Unleashing the full potential of Hsp90 inhibitors as cancer therapeutics through simultaneous inactivation of Hsp90, Grp94, and TRAP1

The Hsp90 family proteins Hsp90, Grp94, and TRAP1 are present in the cell cytoplasm, endoplasmic reticulum, and mitochondria, respectively; all play important roles in tumorigenesis by regulating protein homeostasis in response to stress. Thus, simultaneous inhibition of all Hsp90 paralogs is a reasonable strategy for cancer therapy. However, since the existing pan-Hsp90 inhibitor does not accumulate in mitochondria, the potential anticancer activity of pan-Hsp90 inhibition has not yet been fully examined in vivo. Analysis of The Cancer Genome Atlas database revealed that all Hsp90 paralogs were upregulated in prostate cancer. Inactivation of all Hsp90 paralogs induced mitochondrial dysfunction, increased cytosolic calcium, and activated calcineurin. Active calcineurin blocked prosurvival heat shock responses upon Hsp90 inhibition by preventing nuclear translocation of HSF1. The purine scaffold derivative DN401 inhibited all Hsp90 paralogs simultaneously and showed stronger anticancer activity than other Hsp90 inhibitors. Pan-Hsp90 inhibition increased cytotoxicity and suppressed mechanisms that protect cancer cells, suggesting that it is a feasible strategy for the development of potent anticancer drugs. The mitochondria-permeable drug DN401 is a newly identified in vivo pan-Hsp90 inhibitor with potent anticancer activity.

Complement C5b-9 and Cancer: Mechanisms of Cell Damage, Cancer Counteractions, and Approaches for Intervention

The interactions of cancer cells with components of the complement system are highly complex, leading to an outcome that is either favorable or detrimental to cancer cells. Currently, we perceive only the "tip of the iceberg" of these interactions. In this review, we focus on the complement terminal C5b-9 complex, known also as the complement membrane attack complex (MAC) and discuss the complexity of its interaction with cancer cells, starting with a discussion of its proposed mode of action in mediating cell death, and continuing with a portrayal of the strategies of evasion exhibited by cancer cells, and closing with a proposal of treatment approaches targeted at evasion strategies. Upon intense complement activation and membrane insertion of sufficient C5b-9 complexes, the afflicted cells undergo regulated necrotic cell death with characteristic damage to intracellular organelles, including mitochondria, and perforation of the plasma membrane. Several pro-lytic factors have been proposed, including elevated intracellular calcium ion concentrations and activated JNK, Bid, RIPK1, RIPK3, and MLKL; however, further research is required to fully characterize the effective cell death signals activated by the C5b-9 complexes. Cancer cells over-express a multitude of protective measures which either block complement activation, thus reducing the number of membrane-inserted C5b-9 complexes, or facilitate the elimination of C5b-9 from the cell surface. Concomitantly, cancer cells activate several protective pathways that counteract the death signals. Blockage of complement activation is mediated by the complement membrane regulatory proteins CD46, CD55, and CD59 and by soluble complement regulators, by proteases that cleave complement proteins and by protein kinases, like CK2, which phosphorylate complement proteins. C5b-9 elimination and inhibition of cell death signals are mediated by caveolin and dynamin, by Hsp70 and Hsp90, by the mitochondrial stress protein mortalin, and by the protein kinases PKC and ERK. It is conceivable that various cancers and cancers at different stages of development will utilize distinct patterns of these and other MAC resistance strategies. In order to enhance the impact of antibody-based therapy on cancer, novel precise reagents that block the most effective protective strategies will have to be designed and applied as adjuvants to the therapeutic antibodies.

Interplay between TRAP1 and Sirtuin-3 Modulates Mitochondrial Respiration and Oxidative Stress to Maintain Stemness of Glioma Stem Cells

Glioblastoma (GBM) cancer stem cells (CSC) are primarily responsible for metastatic dissemination, resistance to therapy, and relapse of GBM, the most common and aggressive brain tumor. Development and maintenance of CSCs require orchestrated metabolic rewiring and metabolic adaptation to a changing microenvironment. Here, we show that cooperative interplay between the mitochondrial chaperone TRAP1 and the major mitochondria deacetylase sirtuin-3 (SIRT3) in glioma stem cells (GSC) increases mitochondrial respiratory capacity and reduces production of reactive oxygen species. This metabolic regulation endowed GSCs with metabolic plasticity, facilitated adaptation to stress (particularly reduced nutrient supply), and maintained "stemness." Inactivation of TRAP1 or SIRT3 compromised their interdependent regulatory mechanisms, leading to metabolic alterations, loss of stemness, and suppression of tumor formation by GSC in vivo. Thus, targeting the metabolic mechanisms regulating interplay between TRAP1 and SIRT3 may provide a novel therapeutic option for intractable patients with GBM. SIGNIFICANCE: Discovery and functional analysis of a TRAP1-SIRT3 complex in glioma stem cells identify potential target proteins for glioblastoma treatment.

Wi-Fi is an important threat to human health

Repeated Wi-Fi studies show that Wi-Fi causes oxidative stress, sperm/testicular damage, neuropsychiatric effects including EEG changes, apoptosis, cellular DNA damage, endocrine changes, and calcium overload. Each of these effects are also caused by exposures to other microwave frequency EMFs, with each such effect being documented in from 10 to 16 reviews. Therefore, each of these seven EMF effects are established effects of Wi-Fi and of other microwave frequency EMFs. Each of these seven is also produced by downstream effects of the main action of such EMFs, voltage-gated calcium channel (VGCC) activation. While VGCC activation via EMF interaction with the VGCC voltage sensor seems to be the predominant mechanism of action of EMFs, other mechanisms appear to have minor roles. Minor roles include activation of other voltage-gated ion channels, calcium cyclotron resonance and the geomagnetic magnetoreception mechanism. Five properties of non-thermal EMF effects are discussed. These are that pulsed EMFs are, in most cases, more active than are non-pulsed EMFs; artificial EMFs are polarized and such polarized EMFs are much more active than non-polarized EMFs; dose-response curves are non-linear and non-monotone; EMF effects are often cumulative; and EMFs may impact young people more than adults. These general findings and data presented earlier on Wi-Fi effects were used to assess the Foster and Moulder (F&M) review of Wi-Fi. The F&M study claimed that there were seven important studies of Wi-Fi that each showed no effect. However, none of these were Wi-Fi studies, with each differing from genuine Wi-Fi in three distinct ways. F&M could, at most conclude that there was no statistically significant evidence of an effect. The tiny numbers studied in each of these seven F&M-linked studies show that each of them lack power to make any substantive conclusions. In conclusion, there are seven repeatedly found Wi-Fi effects which have also been shown to be caused by other similar EMF exposures. Each of the seven should be considered, therefore, as established effects of Wi-Fi.

Calcium signaling and the therapeutic targeting of cancer cells

The calcium signal is implicated in a variety of processes important in tumor progression (e.g. proliferation and invasiveness). The calcium signal has also been shown to be important in other processes important in cancer progression including the development of resistance to current cancer therapies. In this review, we discuss how Ca²⁺ channels, pumps and exchangers may be drug targets in some cancer types. We consider what factors should be taken into account when considering an optimal Ca²⁺ channel, pump or exchanger as a candidate for further assessment as a novel drug target in cancer. We also present and summarize how some therapies for the treatment of cancer intersect with Ca²⁺ signaling and how pharmacological manipulation of the machinery of Ca²⁺ signaling could promote the effectiveness of some therapies. We also review new therapeutic opportunities for Ca²⁺ signal modulators in the context of the tumor microenvironment.

Cooperation between Hsp90 and mortalin/GRP75 in resistance to cell death induced by complement C5b-9

Cancer cells are commonly more resistant to cell death activated by the membranolytic protein complex C5b-9. Several surface-expressed and intracellular proteins that protect cells from complement-dependent cytotoxicity (CDC) have been identified. In this study, we investigated the function of heat shock protein 90 (Hsp90), an essential and ubiquitously expressed chaperone, overexpressed in cancer cells, in C5b-9-induced cell death. As shown, inhibition of Hsp90 with geldanamycin or radicicol is enhancing sensitivity of K562 erythroleukemia cells to CDC. Similarly, Hsp90 inhibition confers in Ramos B cell lymphoma cells elevated sensitivity to treatment with rituximab and complement. C5b-9 deposition is elevated on geldanamycin-treated cells. Purified Hsp90 binds directly to C9 and inhibits zinc-induced C9 polymerization, indicating that Hsp90 may act directly on the C5b-9 complex. Mortalin, also known as stress protein 70 or GRP75, is a mitochondrial chaperone that confers resistance to CDC. The postulated cooperation between Hsp90 and mortalin in protection from CDC was tested. Geldanamycin failed to sensitize toward CDC cells with knocked down mortalin. Direct binding of Hsp90 to mortalin was shown by co-immunoprecipitation in cell extracts after triggering with complement as well as by using purified recombinant proteins. These results provide an insight into the protective mechanisms utilized by cancer cells to evade CDC. They suggest that Hsp90 protects cells from CDC by inhibiting, together with mortalin, C5b-9 assembly and/or stability at the plasma membrane.

INF2-mediated actin polymerization at the ER stimulates mitochondrial calcium uptake, inner membrane constriction, and division

Mitochondrial division requires division of both the inner and outer mitochondrial membranes (IMM and OMM, respectively). Interaction with endoplasmic reticulum (ER) promotes OMM division by recruitment of the dynamin Drp1, but effects on IMM division are not well characterized. We previously showed that actin polymerization through ER-bound inverted formin 2 (INF2) stimulates Drp1 recruitment in mammalian cells. Here, we show that INF2-mediated actin polymerization stimulates a second mitochondrial response independent of Drp1: a rise in mitochondrial matrix calcium through the mitochondrial calcium uniporter. ER stores supply the increased mitochondrial calcium, and the role of actin is to increase ER-mitochondria contact. Myosin IIA is also required for this mitochondrial calcium increase. Elevated mitochondrial calcium in turn activates IMM constriction in a Drp1-independent manner. IMM constriction requires electron transport chain activity. IMM division precedes OMM division. These results demonstrate that actin polymerization independently stimulates the dynamics of both membranes during mitochondrial division: IMM through increased matrix calcium, and OMM through Drp1 recruitment.

Heat shock protein-guided dual-mode CT/MR imaging of orthotopic hepatocellular carcinoma tumor

Au@PEI-Gd-AAG NP nanoprobes hold enormous promise for highly efficient tumor diagnosis and dual-mode CT/T₁ positive MR imaging.

Inhibition of Mitochondrial Matrix Chaperones and Antiapoptotic Bcl-2 Family Proteins Empower Antitumor Therapeutic Responses

Rational therapeutic approaches based on synthetic lethality may improve cancer management. On the basis of a high-throughput drug screen, we provide preclinical proof of concept that targeting the mitochondrial Hsp90 chaperone network (mtHsp90) and inhibition of Bcl-2, Bcl-xL, and Mcl-1 is sufficient to elicit synthetic lethality in tumors recalcitrant to therapy. Our analyses focused on BH3 mimetics that are broad acting (ABT263 and obatoclax) or selective (ABT199, WEHI-539, and A1210477), along with the established mitochondrial matrix chaperone inhibitor gamitrinib-TPP. Drug combinations were tested in various therapy-resistant tumors in vitro and in vivo in murine model systems of melanoma, triple-negative breast cancer, and patient-derived orthotopic xenografts (PDX) of human glioblastoma. We found that combining BH3 mimetics and gamitrinib-TPP blunted cellular proliferation in a synergistic manner by massive activation of intrinsic apoptosis. In like manner, suppressing either Bcl-2, Bcl-xL, or Mcl-1 recapitulated the effects of BH3 mimetics and enhanced the effects of gamitrinib-TPP. Mechanistic investigations revealed that gamitrinib-TPP activated a PERK-dependent integrated stress response, which activated the proapoptotic BH3 protein Noxa and its downstream targets Usp9X and Mcl-1. Notably, in the PDX glioblastoma and BRAFi-resistant melanoma models, this drug combination safely and significantly extended host survival. Our results show how combining mitochondrial chaperone and Bcl-2 family inhibitors can synergize to safely degrade the growth of tumors recalcitrant to other treatments. Cancer Res; 77(13); 3513-26. ©2017 AACR.

Chemical Tools to Investigate Mechanisms Associated with HSP90 and HSP70 in Disease

The chaperome is a large and diverse protein machinery composed of chaperone proteins and a variety of helpers, such as the co-chaperones, folding enzymes, and scaffolding and adapter proteins. Heat shock protein 90s and 70s (HSP90s and HSP70s), the most abundant chaperome members in human cells, are also the most complex. As we have learned to appreciate, their functions are context dependent and manifested through a variety of conformations that each recruit a subset of co-chaperone, scaffolding, and folding proteins and which are further diversified by the posttranslational modifications each carry, making their study through classic genetic and biochemical techniques quite a challenge. Chemical biology tools and techniques have been developed over the years to help decipher the complexities of the HSPs and this review provides an overview of such efforts with focus on HSP90 and HSP70.

Fabrication and toxicity characterization of a hybrid material based on oxidized and aminated MWCNT loaded with carboplatin

This study focused on the fabrication and toxicity characterization of a hybrid material-based on the multiple functionalizations of multiwalled carbon nanotubes (MWCNTs) with carboxyl or amino groups and the anti-tumor drug carboplatin (CP). The functionalization was evidenced by Fourier transformed infrared spectroscopy (FTIR) and high performance liquid chromatography (HPLC). The amount of platinum ions released in the simulated body fluid (SBF) was assessed by inductively coupled plasma mass spectrometry (ICP-MS). Cell viability, nanotubes cellular uptake, cell proliferation, superoxide anion production, SOD activity, intracellular glutathione and protein expression of several molecules involved in breast tumor cell survival and death were investigated after 24h exposure. Exposure to the aminated carbon nanotubes loaded with carboplatin resulted in a greater decrease of viability compared to oxidized carbon nanotubes loaded with the same drug, which was in an inversely proportional relationship with the production of superoxide anions in breast cancer cells. The inhibition of Hsp60, Hsp90, p53 and Mdm2 protein expression was induced as a consequence of the cytoprotection mechanism failure. Overexpression of Beclin1 and the reduction of Bcl2 expression were also observed, suggesting that functionalized MWCNT loaded with CP trigger cell death via autophagy in breast cancer cells.

Characterization of Calcium Signals Provoked by Lysophosphatidylinositol in Human Microvascular Endothelial Cells

The lipid molecule, lysophosphatidylinositol (LPI), is hypothesised to form part of a novel lipid signalling system that involves the G protein-coupled receptor GPR55 and distinct intracellular signalling cascades in endothelial cells. This work aimed to study the possible mechanisms involved in LPI-evoked cytosolic Ca2+ mobilization in human brain microvascular endothelial cells. Changes in intracellular Ca2+ concentrations were measured using cell population Ca2+ assay. LPI evoked biphasic elevation of intracellular calcium concentration, a rapid phase and a sustained phase. The rapid phase was attenuated by the inhibitor of PLC (U 73122), inhibitor of IP3 receptors, 2-APB and the depletor of endoplasmic reticulum Ca2+ store, thapsigargin. The sustained phase, on the other hand, was enhanced by U 73122 and abolished by the RhoA kinase inhibitor, Y-27632. In conclusion, the Ca2+ signal evoked by LPI is characterised by a rapid phase of Ca2+ release from the endoplasmic reticulum, and requires activation of the PLC-IP3 signalling pathway. The sustained phase mainly depends on RhoA kinase activation. LPI acts as novel lipid signalling molecule in endothelial cells, and elevation of cytosolic Ca2+ triggered by it may present an important intracellular message required in gene expression and controlling of vascular tone.

Development of a mitochondria-targeted Hsp90 inhibitor based on the crystal structures of human TRAP1

The mitochondrial pool of Hsp90 and its mitochondrial paralogue, TRAP1, suppresses cell death and reprograms energy metabolism in cancer cells; therefore, Hsp90 and TRAP1 have been suggested as target proteins for anticancer drug development. Here, we report that the actual target protein in cancer cell mitochondria is TRAP1, and current Hsp90 inhibitors cannot effectively inactivate TRAP1 because of their insufficient accumulation in the mitochondria. To develop mitochondrial TRAP1 inhibitors, we determined the crystal structures of human TRAP1 complexed with Hsp90 inhibitors. The isopropyl amine of the Hsp90 inhibitor PU-H71 was replaced with the mitochondria-targeting moiety triphenylphosphonium to produce SMTIN-P01. SMTIN-P01 showed a different mode of action from the nontargeted PU-H71, as well as much improved cytotoxicity to cancer cells. In addition, we determined the structure of a TRAP1-adenylyl-imidodiphosphate (AMP-PNP) complex. On the basis of comparative analysis of TRAP1 structures, we propose a molecular mechanism of ATP hydrolysis that is crucial for chaperone function.

The multifaceted mitochondrion: An attractive candidate for therapeutic strategies

Mitochondria are considered the powerhouse of the cell and disturbances in mitochondrial functions are involved in several disorders such as neurodegeneration and mitochondrial diseases. This review summarizes pharmacological strategies that aim at modifying the number of mitochondria, their dynamics or the mitochondrial quality-control mechanisms, in several pathological instances in which any of these mechanisms are impaired or abnormal. The interplay between different cellular pathways that involve mitochondria in order to respond to stress is highlighted. Such a high mitochondrial plasticity could be exploited for new treatments.