Hsp90 Inhibitors Inhibit the Entry of Herpes Simplex Virus 1 Into Neuron Cells by Regulating Cofilin-Mediated F-Actin Reorganization

Herpes simplex virus 1 (HSV-1) is a common neurotropic virus, the herpes simplex encephalitis (HSE) caused by which is considered to be the most common sporadic but fatal encephalitis. Traditional antiviral drugs against HSV-1 are limited to nucleoside analogs targeting viral factors. Inhibition of heat shock protein 90 (Hsp90) has potent anti-HSV-1 activities via numerous mechanisms, but the effects of Hsp90 inhibitors on HSV-1 infection in neuronal cells, especially in the phase of virus entry, are still unknown. In this study, we aimed to investigate the effects of the Hsp90 inhibitors on HSV-1 infection of neuronal cells. Interestingly, we found that Hsp90 inhibitors promoted viral adsorption but inhibited subsequent penetration in neuronal cell lines and primary neurons, which jointly confers the antiviral activity of the Hsp90 inhibitors. Mechanically, Hsp90 inhibitors mainly impaired the interaction between Hsp90 and cofilin, resulting in reduced cofilin membrane distribution, which led to F-actin polymerization to promote viral attachment. However, excessive polymerization of F-actin inhibited subsequent viral penetration. Consequently, unidirectional F-actin polymerization limits the entry of HSV-1 virions into neuron cells. Our research extended the molecular mechanism of Hsp90 in HSV-1 infection in neuron cells and provided a theoretical basis for developing antiviral drugs targeting Hsp90.

Development of Computational Approaches with a Fragment-Based Drug Design Strategy: In Silico Hsp90 Inhibitors Discovery

A semi-exhaustive approach and a heuristic search algorithm use a fragment-based drug design (FBDD) strategy for designing new inhibitors in an in silico process. A deconstruction reconstruction process uses a set of known Hsp90 ligands for generating new ones. The deconstruction process consists of cutting off a known ligand in fragments. The reconstruction process consists of coupling fragments to develop a new set of ligands. For evaluating the approaches, we compare the binding energy of the new ligands with the known ligands.

HSP90 Inhibition Synergizes with Cisplatin to Eliminate Basal-like Pancreatic Ductal Adenocarcinoma Cells

To improve the treatment of pancreatic ductal adenocarcinoma (PDAC), a promising strategy consists of personalized chemotherapy based on gene expression profiles. Investigating a panel of PDAC-derived human cell lines, we found that their sensitivities towards cisplatin fall in two distinct classes. The platinum-sensitive class is characterized by the expression of GATA6, miRNA-200a, and miRNA-200b, which might be developable as predictive biomarkers. In the case of resistant PDAC cells, we identified a synergism of cisplatin with HSP90 inhibitors. Mechanistic explanations of this synergy include the degradation of Fanconi anemia pathway factors upon HSP90 inhibition. Treatment with the drug combination resulted in increased DNA damage and chromosome fragmentation, as we have reported previously for ovarian cancer cells. On top of this, HSP90 inhibition also enhanced the accumulation of DNA-bound platinum. We next investigated an orthotopic syngeneic animal model consisting of tumors arising from KPC cells (LSL-KrasG12D/+; LSL-Trp53R172H/+; Pdx-1-Cre, C57/BL6 genetic background). Here again, when treating established tumors, the combination of cisplatin with the HSP90 inhibitor onalespib was highly effective and almost completely prevented further tumor growth. We propose that the combination of platinum drugs and HSP90 inhibitors might be worth testing in the clinics for the treatment of cisplatin-resistant PDACs.

Anti-Cancer Properties of Ginkgolic Acids in Human Nasopharyngeal Carcinoma CNE-2Z Cells via Inhibition of Heat Shock Protein 90

Ginkgo biloba L. has been used in traditional Chinese medicine (TCM) for thousands of years. However, the anti-cancer properties of ginkgolic acids (GAS) isolated from G. biloba have not been investigated in human nasopharyngeal carcinoma cells. In this study, GAS exhibited an inhibitory effect on the ATPase activity of heat shock protein 90 (Hsp90) and anti-proliferative activities against four human cancer cell lines, with IC50 values ranging from 14.91 to 23.81 μg·mL−1. In vivo experiments confirmed that GAS inhibited tumor growth in CNE-2Z cell-xenografted nude mice with low hepatotoxicity. We further demonstrated that GAS suppressed migration and invasion and induced the apoptosis of CNE-2Z cells by inducing the degradation of Hsp90 client proteins (MMP-2, MMP-9, Her-2, c-Raf, Akt, and Bcl-2). Together, GAS are new Hsp90 inhibitors by binding to Hsp90 (hydrogen bond and hydrophobic interaction). Thus, GAS from G. biloba might represent promising Hsp90 inhibitors for the development of anti-nasopharyngeal carcinoma agents.

Upregulation of TGF-b-induced HSP27 by HSP90 inhibitors in osteoblasts

Background: Heat shock protein (HSP) 90 functions as a molecular chaperone and is constitutively expressed and induced in response to stress in many cell types. We have previously demonstrated that transforming growth factor-b (TGF-b), the most abundant cytokine in bone cells, induces the expression of HSP27 through Smad2, p44/p42 mitogen-activated protein kinase (MAPK), p38 MAPK, and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) in mouse osteoblastic MC3T3-E1 cells. This study investigated the effects of HSP90 on the TGF-b-induced HSP27 expression and the underlying mechanism in mouse osteoblastic MC3T3-E1 cells. Methods: Clonal osteoblastic MC3T3-E1 cells were treated with the HSP90 inhibitors and then stimulated with TGF-b. HSP27 expression and the phosphorylation of Smad2, p44/p42 MAPK, p38 MAPK, and SAPK/JNK were evaluated by western blot analysis. Result: HSP90 inhibitors 17-dimethylaminoethylamino-17-demethoxy-geldanamycin (17-DMAG) and onalespib significantly enhanced the TGF-b-induced HSP27 expression. HSP90 inhibitors, geldanamycin, onalespib, and 17-DMAG did not affect the TGF-b-stimulated phosphorylation of Smad2. Geldanamycin did not affect the TGF-b-stimulated phosphorylation of p44/p42 MAPK or p38 MAPK but significantly enhanced the TGF-b-stimulated phosphorylation of SAPK/JNK. Onalespib also increased the TGF-b-stimulated phosphorylation of SAPK/JNK. Furthermore, SP600125, a specific inhibitor for SAPK/JNK, significantly suppressed onalespib or geldanamycin’s enhancing effect of the TGF-b-induced HSP27 expression levels. As for the canonical BMP signaling pathway, BMP-4 failed to induce the expression of HSP27 in osteoblastic MC3T3-E1 cells. Conclusion: Our results strongly suggest that HSP90 inhibitors upregulated the TGF-b-induced HSP27 expression and that these effects of HSP90 inhibitors were mediated through SAPK/JNK pathway in osteoblasts.

QSAR Studies to Predict Activity of HSP90 Inhibitors

: Heat shock protein 90 (HSP90) is a multichaperone complex that mediates the maturation and stability of a variety of oncogenic signaling proteins. HSP90 has emerged as a promising target for the development of anticancer agents. Heterocyclic chemical moieties with HSP90 inhibitory activity were studied continuously during the last decades, and resulting data were applied by medicinal chemists to design and develop new drugs. Their structure-activity relationship (SAR) studies and QSAR models have been derived to assist the current drug development process. The QSAR models are obtained via multiple linear regression (MLR) and non-linear approaches. Interpretation of the reported model highlights the core template required to design novel, potent HSP90 inhibitors to be used as anticancer agents.

Role of HSP90 in Cancer

HSP90 is a vital chaperone protein conserved across all organisms. As a chaperone protein, it correctly folds client proteins. Structurally, this protein is a dimer with monomer subunits that consist of three main conserved domains known as the N-terminal domain, middle domain, and the C-terminal domain. Multiple isoforms of HSP90 exist, and these isoforms share high homology. These isoforms are present both within the cell and outside the cell. Isoforms HSP90α and HSP90β are present in the cytoplasm; TRAP1 is present in the mitochondria; and GRP94 is present in the endoplasmic reticulum and is likely secreted due to post-translational modifications (PTM). HSP90 is also secreted into an extracellular environment via an exosome pathway that differs from the classic secretion pathway. Various co-chaperones are necessary for HSP90 to function. Elevated levels of HSP90 have been observed in patients with cancer. Despite this observation, the possible role of HSP90 in cancer was overlooked because the chaperone was also present in extreme amounts in normal cells and was vital to normal cell function, as observed when the drastic adverse effects resulting from gene knockout inhibited the production of this protein. Differences between normal HSP90 and HSP90 of the tumor phenotype have been better understood and have aided in making the chaperone protein a target for cancer drugs. One difference is in the conformation: HSP90 of the tumor phenotype is more susceptible to inhibitors. Since overexpression of HSP90 is a factor in tumorigenesis, HSP90 inhibitors have been studied to combat the adverse effects of HSP90 overexpression. Monotherapies using HSP90 inhibitors have shown some success; however, combination therapies have shown better results and are thus being studied for a more effective cancer treatment.