Identification of Cellular Protein Targets of a Half-Sandwich Iridium(III) Complex Reveals Its Dual Mechanism of Action via Both Electrophilic and Oxidative Stresses.

Identification of intracellular targets of anticancer drug candidates provides key information on their mechanism of action. Exploiting the ability of the anticancer (C∧N)-chelated half-sandwich iridium(III) complexes to covalently bind proteins, click chemistry with a bioorthogonal azido probe was used to localize a phenyloxazoline-chelated iridium complex within cells and profile its interactome at the proteome-wide scale. Proteins involved in protein folding and actin cytoskeleton regulation were identified as high-affinity targets. Upon iridium complex treatment, the folding activity of Heat Shock Protein HSP90 was inhibited in vitro and major cytoskeleton disorganization was observed. A wide array of imaging and biochemical methods validated selected targets and provided a multiscale overview of the effects of this complex on live human cells. We demonstrate that it behaves as a dual agent, inducing both electrophilic and oxidative stresses in cells that account for its cytotoxicity. The proposed methodological workflow can open innovative avenues in metallodrug discovery.

The HSP90 inhibitor HVH-2930 exhibits potent efficacy against trastuzumab-resistant HER2-positive breast cancer.

Rationale: Resistance to targeted therapies like trastuzumab remains a critical challenge for HER2-positive breast cancer patients. Despite the progress of several N-terminal HSP90 inhibitors in clinical trials, none have achieved approval for clinical use, primarily due to issues such as induction of the heat shock response (HSR), off-target effects, and unfavorable toxicity profiles. We sought to examine the effects of HVH-2930, a novel C-terminal HSP90 inhibitor, in overcoming trastuzumab resistance. Methods: The effect of HVH-2930 on trastuzumab-sensitive and -resistant cell lines in vitro was evaluated in terms of cell viability, expression of HSP90 client proteins, and impact on cancer stem cells. An in vivo model with trastuzumab-resistant JIMT-1 cells was used to examine the efficacy and toxicity of HVH-2930. Results: HVH-2930 was rationally designed to fit into the ATP-binding pocket interface cavity of the hHSP90 homodimer in the C-terminal domain of HSP90, stabilizing its open conformation and hindering ATP binding. HVH-2930 induces apoptosis without inducing the HSR but by specifically suppressing the HER2 signaling pathway. This occurs with the downregulation of HER2/p95HER2 and disruption of HER2 family member heterodimerization. Attenuation of cancer stem cell (CSC)-like properties was associated with the downregulation of stemness factors such as ALDH1, CD44, Nanog and Oct4. Furthermore, HVH-2930 administration inhibited angiogenesis and tumor growth in trastuzumab-resistant xenograft mice. A synergistic effect was observed when combining HVH-2930 and paclitaxel in JIMT-1 xenografts. Conclusion: Our findings highlight the potent efficacy of HVH-2930 in overcoming trastuzumab resistance in HER2-positive breast cancer. Further investigation is warranted to fully establish its therapeutic potential.

Targeted delivery of HSP90 inhibitors for efficient therapy of CD44-positive acute myeloid leukemia and solid tumor-colon cancer.

Heat shock protein 90 (HSP90) is overexpressed in numerous cancers, promotes the maturation of numerous oncoproteins and facilitates cancer cell growth. Certain HSP90 inhibitors have entered clinical trials. Although less than satisfactory clinical effects or insurmountable toxicity have compelled these trials to be terminated or postponed, these results of preclinical and clinical studies demonstrated that the prospects of targeting therapeutic strategies involving HSP90 inhibitors deserve enough attention. Nanoparticulate-based drug delivery systems have been generally supposed as one of the most promising formulations especially for targeting strategies. However, so far, no active targeting nano-formulations have succeeded in clinical translation, mainly due to complicated preparation, complex formulations leading to difficult industrialization, incomplete biocompatibility or nontoxicity. In this study, HSP90 and CD44-targeted A6 peptide functionalized biomimetic nanoparticles (A6-NP) was designed and various degrees of A6-modification on nanoparticles were fabricated to evaluate targeting ability and anticancer efficiency. With no excipients, the hydrophobic HSP90 inhibitor G2111 and A6-conjugated human serum albumin could self-assemble into nanoparticles with a uniform particle size of approximately 200 nm, easy fabrication, well biocompatibility and avoidance of hepatotoxicity. Besides, G2111 encapsulated in A6-NP was only released less than 5% in 12 h, which may avoid off-target cell toxicity before entering into cancer cells. A6 peptide modification could significantly enhance uptake within a short time. Moreover, A6-NP continues to exert the broad anticancer spectrum of Hsp90 inhibitors and displays remarkable targeting ability and anticancer efficacy both in hematological malignancies and solid tumors (with colon tumors as the model cancer) both in vitro and in vivo. Overall, A6-NP, as a simple, biomimetic and active dual-targeting (CD44 and HSP90) nanomedicine, displays high potential for clinical translation.

Discovery of potent heat shock protein 90 (Hsp90) inhibitors: structure-based virtual screening, molecular dynamics simulation, and biological evaluation.

Heat shock protein 90 (Hsp90) is considered an attractive therapeutic target for cancer treatment due to its high expression in many cancers. In this study, four potent Hsp90 inhibitors (HPs 1-4) were identified using structure-based virtual screening. Among them, HP-4 exhibited the most potent inhibitory effects (IC50 = 17.64 ± 1.45 nM) against the Hsp90 protein, which was about 7.7 times stronger than that of MPC-3100 (a positive inhibitor targeting Hsp90). In vitro cytotoxicity assay suggested that HP-4 could effectively inhibit the proliferation of a series of tumour cells, including HCT-116, HeLa, A549, A2780, DU145, HepG2 and A498. Furthermore, in vivo assay displayed that HP-4 had significant anti-tumour effects on HCT-116 cell-derived xenograft models. These data demonstrate that HP-4 could be a potential lead compound for the further investigation of anti-tumour drugs.

HSP90-regulated CHIP/TRIM21/p21 Axis Involves in the Senescence of Osteosarcoma Cells.

BACKGROUND: OS is the most frequent malignant bone tumor with a poor prognosis. TRIM21 has been reported to play a critical role in OS by regulating the expression of the TXNIP/p21 axis and inhibiting the senescence of OS cells. AIM: Investigation of the molecular mechanism of tripartite motif 21 (TRIM21) in osteosarcoma (OS) would shed light on the understanding of the pathogenesis of OS. OBJECTIVE: This study aimed to explore the mechanism regulating the protein stability of TRIM21 in the process of OS senescence. METHODS: Human U2 OS cells were used to establish stable cells overexpressing TRIM21 (induced by Dox) or knocking down TRIM21. The co-immunoprecipitation (co-IP) assay was used to examine the interaction between TRIM21 and HSP90. Immunofluorescence (IF) assay was used to observe colocalization in OS cells. Western blot analysis was applied to detect the protein expression, and quantitative real-time PCR (qRT-PCR) assay was used to test the mRNA expression of corresponding genes. SA-ß-gal staining was used to evaluate OS senescence. RESULTS: In this study, we verified the interaction between HSP90 and TRIM21 using a co-IP assay. Knockdown or inhibition of HSP90 with its inhibitor 17-AAG accelerated the degradation of TRIM21 by the proteasome in OS cells. CHIP E3 ligase mediated this degradation of TRIM21, with the knockdown of CHIP rescuing the downregulation of TRIM21 induced by 17-AAG. TRIM21 inhibited OS senescence and downregulated the expression of senescence marker p21, while CHIP exhibited an opposite regulatory role on p21 expression. CONCLUSION: Taken together, our results demonstrated that HSP90 is responsible for the stabilization of TRIM21 in OS and that the CHIP/TRIM21/p21 axis controlled by HSP90 affects the senescence of OS cells.

Synthesis, DFT calculations, and anti-proliferative evaluation of pyrimidine and selenadiazolopyrimidine derivatives as dual Topoisomerase II and HSP90 inhibitors.

Novel series of aminopyrimidines bearing a biologically active cyclohexenone 3a-f and oxo-selaneylidene moiety 4, besides selenadiazolopyrimidines (5a-e and 7), were synthesised using 5,6-diaminouracils as starting materials. Compound 3a exhibited strong anti-proliferative activity against three cell lines: HepG-2 (IC50 14.31 ± 0.83 µM), A-549 (IC50 30.74 ± 0.76 µM), and MCF-7 (IC50 27.14 ± 1.91 µM). Also, it was four times more selectively cytotoxic against WI-38 cell lines than doxorubicin. Furthermore, Topoisomerase II (IC50 4.48 ± 0.65 µM) and HSP90 (IC50 1.78 ± 0.11 µM) were both strongly inhibited in vitro by 3a. The cell cycle was halted at the G1-S phase, and total apoptotic cells were 65 times more than control Hep-G2 cells. Besides, it increased caspase-3 gene expression, triggering mitochondrial cell death. Molecular docking study indicated that it could bind to Topoisomerase II and HSP90 binding sites in an inhibitory mode. Its geometric properties were investigated using the density functional theory (DFT). Furthermore, compound 3a demonstrated in silico good oral bioavailability.

Targeted Inhibition of Hsp90 in Combination with Metformin Modulates Programmed Cell Death Pathways in A549 Lung Cancer Cells.

The pathophysiology of lung cancer is dependent on the dysregulation in the apoptotic and autophagic pathways. The intricate link between apoptosis and autophagy through shared signaling pathways complicates our understanding of how lung cancer pathophysiology is regulated. As drug resistance is the primary reason behind treatment failure, it is crucial to understand how cancer cells may respond to different therapies and integrate crosstalk between apoptosis and autophagy in response to them, leading to cell death or survival. Thus, in this study, we have tried to evaluate the crosstalk between autophagy and apoptosis in A549 lung cancer cell line that could be modulated by employing a combination therapy of metformin (6 mM), an anti-diabetic drug, with gedunin (12 µM), an Hsp90 inhibitor, to provide insights into the development of new cancer therapeutics. Our results demonstrated that metformin and gedunin were cytotoxic to A549 lung cancer cells. Combination of metformin and gedunin generated ROS and promoted MMP loss and DNA damage. The combination further increased the expression of AMPKα1 and promoted the nuclear localization of AMPKα1/α2. The expression of Hsp90 was downregulated, further decreasing the expression of its clients, EGFR, PIK3CA, AKT1, and AKT3. Inhibition of the EGFR/PI3K/AKT pathway upregulated TP53 and inhibited autophagy. The combination was promoting nuclear localization of p53; however, some cytoplasmic signals were also detected. Further increase in the expression of caspase 9 and caspase 3 was observed. Thus, we concluded that the combination of metformin and gedunin upregulates apoptosis by inhibiting the EGFR/PI3K/AKT pathway and autophagy in A549 lung cancer cells.

Heat shock protein 90 (HSP90) inhibitors in gastrointestinal cancer: where do we currently stand?-A systematic review.

PURPOSE: Dysregulated expression of heat shock proteins (HSP) plays a fundamental role in tumor development and progression. Consequently, HSP90 may be an effective tumor target in oncology, including the treatment of gastrointestinal cancers. METHODS: We carried out a systematic review of data extracted from clinicaltrials.gov and pubmed.gov, which included all studies available until January 1st, 2022. The published data was evaluated using primary and secondary endpoints, particularly with focus on overall survival, progression-free survival, and rate of stable disease. RESULTS: Twenty trials used HSP90 inhibitors in GI cancers, ranging from phase I to III clinical trials. Most studies assessed HSP90 inhibitors as a second line treatment. Seventeen of the 20 studies were performed prior to 2015 and only few studies have results pending. Several studies were terminated prematurely, due to insufficient efficacy or toxicity. Thus far, the data suggests that HSP90 inhibitor NVP-AUY922 might improve outcome for colorectal cancer and gastrointestinal stromal tumors. CONCLUSION: It currently remains unclear which subgroup of patients might benefit from HSP90 inhibitors and at what time point these inhibitors may be beneficial. There are only few new or ongoing studies initiated during the last decade.

Role of Ganetespib, an HSP90 Inhibitor, in Cancer Therapy: From Molecular Mechanisms to Clinical Practice.

Heat-shock proteins are upregulated in cancer and protect several client proteins from degradation. Therefore, they contribute to tumorigenesis and cancer metastasis by reducing apoptosis and enhancing cell survival and proliferation. These client proteins include the estrogen receptor (ER), epidermal growth factor receptor (EGFR), insulin-like growth factor-1 receptor (IGF-1R), human epidermal growth factor receptor 2 (HER-2), and cytokine receptors. The diminution of the degradation of these client proteins activates different signaling pathways, such as the PI3K/Akt/NF-κB, Raf/MEK/ERK, and JAK/STAT3 pathways. These pathways contribute to hallmarks of cancer, such as self-sufficiency in growth signaling, an insensitivity to anti-growth signals, the evasion of apoptosis, persistent angiogenesis, tissue invasion and metastasis, and an unbounded capacity for replication. However, the inhibition of HSP90 activity by ganetespib is believed to be a promising strategy in the treatment of cancer because of its low adverse effects compared to other HSP90 inhibitors. Ganetespib is a potential cancer therapy that has shown promise in preclinical tests against various cancers, including lung cancer, prostate cancer, and leukemia. It has also shown strong activity toward breast cancer, non-small cell lung cancer, gastric cancer, and acute myeloid leukemia. Ganetespib has been found to cause apoptosis and growth arrest in these cancer cells, and it is being tested in phase II clinical trials as a first-line therapy for metastatic breast cancer. In this review, we will highlight the mechanism of action of ganetespib and its role in treating cancer based on recent studies.

Malachite Green Assay for the Discovery of Heat-Shock Protein 90 Inhibitors.

Heat shock protein 90 (Hsp90) is a promising anticancer target because of its chaperoning effect on multiple oncogenic proteins. The activity of Hsp90 is dependent on its ability to hydrolyze adenosine triphosphate (ATP) to adenosine diphosphate (ADP) and free phosphate. The ATPase activity of Hsp90 is linked to its chaperoning function; ATP binds to the N-terminal domain of the Hsp90, and disrupting its binding was found to be the most successful strategy in suppressing Hsp90 function. The ATPase activity can be measured by a colorimetric malachite green assay, which determines the amount of free phosphate formed by ATP hydrolysis. Here, a procedure for determining the ATPase activity of yeast Hsp90 by using the malachite green phosphate assay kit is described. Further, detailed instructions for the discovery of Hsp90 inhibitors by taking geldanamycin as an authentic inhibitor is provided. Finally, the application of this assay protocol through the high-throughput screening (HTS) of inhibitor molecules against yeast Hsp90 is discussed.

Heat shock protein 90 inhibitor RGRN-305 potently attenuates skin inflammation.

Introduction: Chronic inflammatory skin diseases may have a profound negative impact on the quality of life. Current treatment options may be inadequate, offering an unsatisfactory response or side effects. Therefore, ongoing efforts exist to identify novel effective and safe treatments. Heat shock protein (HSP) 90 is a chaperone that promotes the activity of a wide range of client proteins including key proinflammatory molecules involved in aberrant inflammation. Recently, a proof-of-concept clinical trial of 13 patients suggested that RGRN-305 (an HSP90 inhibitor) may be an oral treatment for psoriasis. However, HSP90 inhibition may be a novel therapeutic approach extending beyond psoriasis to include multiple immune-mediated inflammatory skin diseases. Methods: This study aimed to investigate (i) the anti-inflammatory effects and mechanisms of HSP90 inhibition and (ii) the feasibility of topical RGRN-305 administration (new route of administration) in models of inflammation elicited by 12-O-tetradecanoylphorbol-13-acetate (TPA) in primary human keratinocytes and mice (irritative dermatitis murine model). Results/Discussion: In primary human keratinocytes stimulated with TPA, a Nanostring® nCounter gene expression assay demonstrated that HSP90 inhibition with RGRN-305 suppressed many proinflammatory genes. Furthermore, when measured by quantitative real-time polymerase chain reaction (RT-qPCR), RGRN-305 significantly reduced the gene expression of TNF, IL1B, IL6 and CXCL8. We next demonstrated that topical RGRN-305 application significantly ameliorated TPA-induced skin inflammation in mice. The increase in ear thickness (a marker of inflammation) was significantly reduced (up to 89% inhibition). In accordance, RT-qPCR of the ear tissue demonstrated that RGRN-305 robustly reduced the gene expression of proinflammatory markers (Tnf, Il1b, Il6, Il17A and Defb4). Moreover, RNA sequencing revealed that RGRN-305 mitigated TPA-induced alterations in gene expression and suppressed genes implicated in inflammation. Lastly, we discovered that the anti-inflammatory effects were mediated, at least partly, by suppressing the activity of NF-κB, ERK1/2, p38 MAPK and c-Jun signaling pathways, which are consistent with previous findings in other experimental models beyond skin inflammation. In summary, HSP90 inhibition robustly suppressed TPA-induced inflammation by targeting key proinflammatory cytokines and signaling pathways. Our findings suggest that HSP90 inhibition may be a novel mechanism of action for treating immune-mediated skin disease beyond psoriasis, and it may be a topical treatment option.

Synthetic Small Molecule Modulators of Hsp70 and Hsp40 Chaperones as Promising Anticancer Agents.

A class of chaperones dubbed heat shock protein 70 (Hsp70) possesses high relevance in cancer diseases due to its cooperative activity with the well-established anticancer target Hsp90. However, Hsp70 is closely connected with a smaller heat shock protein, Hsp40, forming a formidable Hsp70-Hsp40 axis in various cancers, which serves as a suitable target for anticancer drug design. This review summarizes the current state and the recent developments in the field of (semi-)synthetic small molecule inhibitors directed against Hsp70 and Hsp40. The medicinal chemistry and anticancer potential of pertinent inhibitors are discussed. Since Hsp90 inhibitors have entered clinical trials but have exhibited severe adverse effects and drug resistance formation, potent Hsp70 and Hsp40 inhibitors may play a significant role in overcoming the drawbacks of Hsp90 inhibitors and other approved anticancer drugs.

Identification of Novel Natural Dual HDAC and Hsp90 Inhibitors for Metastatic TNBC Using e-Pharmacophore Modeling, Molecular Docking, and Molecular Dynamics Studies.

Breast cancer (BC) is one of the main types of cancer that endangers women's lives. The characteristics of triple-negative breast cancer (TNBC) include a high rate of recurrence and the capacity for metastasis; therefore, new therapies are urgently needed to combat TNBC. Dual targeting HDAC6 and Hsp90 has shown good synergistic effects in treating metastatic TNBC. The goal of this study was to find potential HDAC6 and Hsp90 dual inhibitors. Therefore, several in silico approaches have been used. An e-pharmacophore model generation based on the HDAC6-ligand complex and subsequently a pharmacophore-based virtual screening on 270,450 natural compounds from the ZINC were performed, which resulted in 12,663 compounds that corresponded to the obtained pharmacophoric hypothesis. These compounds were docked into HDAC6 and Hsp90. This resulted in the identification of three compounds with good docking scores and favorable free binding energy against the two targets. The top three compounds, namely ZINC000096116556, ZINC000020761262, and ZINC000217668954, were further subjected to ADME prediction and molecular dynamic simulations, which showed promising results in terms of pharmacokinetic properties and stability. As a result, these three compounds can be considered potential HDAC6 and Hsp90 dual inhibitors and are recommended for experimental evaluation.

Diptoindonesin G, a new Hsp90 drug.

Hsp90 is a molecular chaperone that participates in protein folding, activation, and stabilization of substrate proteins. Since many diseases, including cancer, neurodegenerative diseases, and metabolic diseases, are caused by protein misfolding, drugs that inhibit Hsp90 are being pursued as potential targets for treatments. In the recent JBC Editor's Pick by Donahue et al., the authors show that diptoindonesin G is a new Hsp90 inhibitor that promotes degradation of the estrogen receptor, an Hsp90 client, without inducing the heat shock response.

HSP90 inhibitors and cancer: Prospects for use in targeted therapies (Review).

Heat shock protein 90 (HSP90) is a vital chaperone protein, regulating signaling pathways and correcting misfolded proteins in cancer cells by interacting with oncogenic client proteins and co­chaperones. The inhibition of HSP90 chaperone machinery has been demonstrated as a potential approach with which to inhibit tumor survival, proliferation, invasion and migration. Numerous HSP90 inhibitors have been reported and have exhibited value as cancer­targeted therapies by interrupting the ATPase activity of HSP90, thus suppressing the oncogenic pathways in cancer cells. These inhibitors have been classified into three categories: i) N­terminal domain (NTD) inhibitors; ii) C­terminal domain (CTD) inhibitors; and iii) isoform­selective inhibitors. However, none of these HSP90 inhibitors are used as clinical treatments. The major limiting factors can be summarized into drug resistance, dose­limiting toxicity and poor pharmacokinetic profiles. Novel HSP90­targeted compounds are constantly being discovered and tested for their antitumor efficacy in preclinical and clinical trials, highlighting the prospect of the use of HSP90 inhibitors as cancer­targeted therapies. Additionally, improved antitumor effects have been observed when HSP90 inhibitors are used in combination with chemotherapy, targeted agents, or immunotherapy. In the present review, the effects of HSP90 inhibitors on the management of the cancer process are discussed and previous and novel HSP90­based therapeutic strategies in cancer treatment are summarized. Furthermore, prospective HSP90­targeting candidates are proposed for their future evaluation as cancer treatments.

The Role of HSP90 Inhibitors in the Treatment of Cardiovascular Diseases.

Cardiovascular disease is the result of complicated pathophysiological processes in the tissues that make up the blood vessels and heart. Heat shock protein 90 (HSP90) can interact with 10% of the proteome and is the most widely studied molecular chaperone in recent years. HSP90 is extensively involved in the regulation of protein folding and intracellular protein stability, making HSP90 a hopeful target for the treatment of multiple cardiovascular diseases. Numerous client proteins of HSP90 have been identified in known cardiac disease pathways, including MAPK signaling, PI3K/AKT (PKB)/mTOR, and TNF-α signaling. Therefore, these pathways can be controlled by regulating HSP90. Among them, the activity of HSP90 can be regulated via numerous inhibitors. In this review, first, we will discuss the function of HSP90 and its role in pathological pathways. In addition, HSP90 plays a significant role in most cardiovascular diseases, including hypertension, pulmonary venous hypertension, atherosclerosis, and heart failure; next we will focus on this part. Finally, we will summarize the currently known HSP90 inhibitors and their potential in the treatment of heart disease.

Design, synthesis and biological evaluation of a new class of Hsp90 inhibitors vibsanin C derivatives.

Hsp90, an ATP-dependent chaperone that is essential for a wide range of protein assembly and folding processes, has long been recognized as a potential target for cancer. Hsp90 has more recently been identified as having a significant pathogenic role in viral infection, neurodegenerative disease, and inflammation, therefore, the development of the agents to inhibit the chaperone could potentially treat such intractable diseases. Here, on the basis of primary structure-activity relationships and docking analysis, a series of novel vibsanin C analogues with an emphasis on the C18 position was first designed, synthesized and biologically evaluated. The most effective Hsp90 inhibitory activity among these analogues was demonstrated by 29 and 31, with IC50 values of 0.39 and 0.27 µM respectively. Direct interaction between Hsp90 and its inhibitors were further confirmed. Mechanism studies indicated that 29 promoted HL-60 cell apoptosis by mitochondrial-mediated apoptosis pathway. In addition, 29 suppressed tumor growth in the H22 tumor-bearing mice model and revealed low acute toxicity in mice (LD50 > 500 mg/kg), suggesting its potential for further investigations.

Hsp90 Activity Is Necessary for the Maturation of Rabies Virus Polymerase.

Mononegavirales is an order of viruses with a genome in the form of a non-segmented negative-strand RNA that encodes several proteins. The functional polymerase complex of these viruses is composed of two proteins: a large protein (L) and a phosphoprotein (P). The replication of viruses from this order depends on Hsp90 chaperone activity. Previous studies have demonstrated that Hsp90 inhibition results in the degradation of mononegaviruses L protein, with exception of the rabies virus, for which the degradation of P protein was observed. Here, we demonstrated that Hsp90 inhibition does not affect the expression of rabies L and P proteins, but it inhibits binding of the P protein and L protein into functional viral polymerase. Rabies and the vesicular stomatitis virus, but not the measles virus, L proteins can be expressed independently of the presence of a P protein and in the presence of an Hsp90 inhibitor. Our results suggest that the interaction of L proteins with P proteins and Hsp90 in the process of polymerase maturation may be a process specific to particular viruses.

HSP90 N-terminal inhibitors target oncoprotein MORC2 for autophagic degradation and suppress MORC2-driven breast cancer progression.

AIMS: MORC family CW-type zinc finger 2 (MORC2), a GHKL-type ATPase, is aberrantly upregulated in multiple types of human tumors with profound effects on cancer aggressiveness, therapeutic resistance, and clinical outcome, thus making it an attractive drug target for anticancer therapy. However, the antagonists of MORC2 have not yet been documented. METHODS AND RESULTS: We report that MORC2 is a relatively stable protein, and the N-terminal homodimerization but not ATP binding and hydrolysis is crucial for its stability through immunoblotting analysis and Quantitative real-time PCR. The N-terminal but not C-terminal inhibitors of heat shock protein 90 (HSP90) destabilize MORC2 in multiple cancer cell lines, and strikingly, this process is independent on HSP90. Mechanistical investigations revealed that HSP90 N-terminal inhibitors disrupt MORC2 homodimer formation without affecting its ATPase activities, and promote its lysosomal degradation through the chaperone-mediated autophagy pathway. Consequently, HSP90 inhibitor 17-AAG effectively blocks the growth and metastatic potential of MORC2-expressing breast cancer cells both in vitro and in vivo, and these noted effects are not due to HSP90 inhibition. CONCLUSION: We uncover a previously unknown role for HSP90 N-terminal inhibitors in promoting MORC2 degradation in a HSP90-indepentent manner and support the potential application of these inhibitors for treating MORC2-overexpressing tumors, even those with low or absent HSP90 expression. These results also provide new clue for further design of novel small-molecule inhibitors of MORC2 for anticancer therapeutic application.

A novel small molecule Hsp90 inhibitor, C-316-1, attenuates acute kidney injury by suppressing RIPK1-mediated inflammation and necroptosis.

Acute kidney injury (AKI) is marked by a fast deterioration of the kidney function that may be caused by a variety of factors. Recently, although our group found that PPBICA alleviated programmed cell death in AKI, poor water solubility limited its bioavailability. In this research, we screened a series of derivatives and found that C-316-1 had the best suppressive effect on preventing necroptosis and inflammation in cisplatin- and ischemia/reperfusion-induced AKI in vitro and in vivo with lower toxicity and better water solubility. Mass spectrometry results showed that C-316-1 bound to heat shock protein 90 (Hsp90), which was further confirmed by molecular docking and surface plasmon resonance. Additionally, the Hsp90 expression was upregulated in the blood and tissues of AKI patients. We discovered that C-316-1 decreased the RIPK1 protein level without affecting its mRNA expression. The proteasome inhibitor, MG132 restored the level of RIPK1 reduced by C-316-1, suggesting that C-316-1 limits necroptosis by promoting the degradation of RIPK1 rather than by reducing its production. Immunoprecipitation further showed that pretreatment with C-316-1 disrupted the Hsp90-Cdc37 protein-protein Interactions (PPIs). Thereby, C-316-1 inhibited the Hsp90-Cdc37 complex formation and led to a significant decrease in RIPK1, which in turn reduced necroptosis. Moreover, C-316-1 treatment did not protect against kidney injury in vivo and in vitro when Hsp90 was knocked down and R46, E47, and S50 in Cdc37 binding site of Hsp90 might form an important active pocket with C-316-1. These findings suggest that C-316-1 is a potential therapeutic agent against RIPK1-Mediated Necroptosis in AKI.