Hsp90: an emerging target for breast cancer therapy

Synthesis and characterization of 64Cu-labeled Geldanamycin derivative for imaging HSP90 expression in breast cancer

Heat shock protein 90 (HSP90) plays a crucial role in cancer cell growth and metastasis by stabilizing overexpressed signaling proteins. Inhibiting HSP90 has emerged as a promising anti-cancer strategy. In this study, we aimed to develop and characterize a HSP90-targeted molecular imaging probe, [64Cu]Cu-DOTA-BDA-GM, based on a specific HSP90 inhibitor, geldanamycin (GM), for PET imaging of cancers. GM is modified at the C-17 position with 1,4-butane-diamine (BDA) and linked to 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) for 64Cu radiolabeling. We evaluated the probe's specific binding to HSP90-expressing cells using Chinese hamster ovary (CHO) cells and breast cancer cells including MDA-MB-231, MDA-MB-435S, MCF7, and KR-BR-3 cell lines. A competition study with non-radioactive GM-BDA yielded an IC50 value of 1.35 ± 0.14 nM, underscoring the probe's affinity for HSP90. In xenograft models of MDA-MB-231 breast cancer, [64Cu]Cu-DOTA-BDA-GM showcased targeted tumor localization, with significant radioactivity observed up to 18 h post-injection. Blocking studies using unlabeled GM-BDA and treatment with the anticancer drug Vorinostat (SAHA), which can affect the expression and activity of numerous proteins, such as HSPs, confirmed the specificity and sensitivity of the probe in cancer targeting. Additionally, PET/CT imaging in a lung metastasis mouse model revealed increased lung uptake of [64Cu]Cu-DOTA-BDA-GM in metastatic sites, significantly higher than in non-metastatic lungs, illustrating the probe's ability to detect metastatic breast cancer. In conclusion, [64Cu]Cu-DOTA-BDA-GM represents a sensitive and specific approach for identifying HSP90 expression in breast cancer and metastases, offering promising implications for clinical diagnosis and monitoring.

Synthesis of new antiproliferative 1,3,4-substituted-pyrrolo[3,2-c]quinoline derivatives, biological and in silico insights

A series of biologically unexplored substituted 1,3,4-subtituted-pyrrolo[3,2-c]quinoline derivatives (PQs) was evaluated against a panel of about 60 tumor cells (NCI). Based on the preliminary antiproliferative data, the optimizations efforts permitted us to design and synthesize a new series of derivatives allowing us to individuate a promising hit (4g). The insertion of a 4-benzo[d] [1,3]dioxol-5-yl moiety on increased and extended the activity towards five panel tumor cell lines such as leukemia, CNS, melanoma, renal and breast cancer, reaching IG₅₀ in the low μM range. Replacement of this latter with a 4-(OH-di-Cl-Ph) group (4i) or introduction a Cl-propyl chain in position 1 (5), selectively addressed the activity against the entire leukemia sub-panel (CCRF-CEM, K-562, MOLT-4, RPMI-8226, SR). Preliminary biological assays on MCF-7 such as cell cycle, clonogenic assay, ROS content test alongside a comparison of viability between MCF-7 and non-tumorigenic MCF-10 were investigated. Among the main anticancer targets involved in breast cancer, HSP90 and ER receptors were selected for in silico studies. Docking analysis revealed a valuable affinity for HSP90 providing structural insights on the binding mode, and useful features for optimization.

Uncovering the molecular mechanism of Gynostemma pentaphyllum (Thunb.) Makino against breast cancer using network pharmacology and molecular docking

Because of their strong anti-cancer efficacy with fewer side effects, traditional Chinese medicines (TCM) have attracted considerable attention for their potential application in treating breast cancer (BC). However, knowledge about the underlying systematic mechanisms is scarce. Gynostemma pentaphyllum (Thunb.) Makino (GP), a creeping herb, has been regularly used as a TCM to prevent and treat tumors including BC. Again, mechanisms underlying its anti-BC properties have remained elusive. We used network pharmacology and molecular docking to explore the mechanistic details of GP against BC. The TCM systems pharmacology database and analysis platform and PharmMapper Server database were used to retrieve the chemical constituents and potential targets in GP. In addition, targets related to BC were identified using DrugBank and Therapeutic Target Database. Protein-protein interaction network, Gene Ontology, and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses of crucial targets were performed using the Search Tool for the Retrieval of Interacting Genes/Proteins and database for annotation, visualization, and integrated discovery databases, whereas the network visualization analysis was performed using Cytoscape 3.8.2. In addition, the molecular docking technique was used to validate network pharmacology-based predictions. A comparison of the predicted targets of GP with those of BC-related drugs revealed 26 potential key targets related to the treatment of BC, among which ALB, EGFR, ESR1, AR, PGR, and HSP90AA1 were considered the major potential targets. Finally, network pharmacology-based prediction results were preliminarily verified by molecular docking experiments. In addition, chemical constituents and potential target proteins were scored, followed by a comparison with the ligands of the protein. We provide a network of pharmacology-based molecular mechanistic insights on the therapeutic action of GP against BC. We believe that our data will serve as a basis to conduct future studies and promote the clinical applications of GP.

Safety and efficacy of HSP90 inhibitor ganetespib for neoadjuvant treatment of stage II/III breast cancer

HSP90 inhibitors destabilize oncoproteins associated with cell cycle, angiogenesis, RAS-MAPK activity, histone modification, kinases and growth factors. We evaluated the HSP90-inhibitor ganetespib in combination with standard chemotherapy in patients with high-risk early-stage breast cancer. I-SPY2 is a multicenter, phase II adaptively randomized neoadjuvant (NAC) clinical trial enrolling patients with stage II-III breast cancer with tumors 2.5 cm or larger on the basis of hormone receptors (HR), HER2 and Mammaprint status. Multiple novel investigational agents plus standard chemotherapy are evaluated in parallel for the primary endpoint of pathologic complete response (pCR). Patients with HER2-negative breast cancer were eligible for randomization to ganetespib from October 2014 to October 2015. Of 233 women included in the final analysis, 140 were randomized to the standard NAC control; 93 were randomized to receive 150 mg/m2 ganetespib every 3 weeks with weekly paclitaxel over 12 weeks, followed by AC. Arms were balanced for hormone receptor status (51-52% HR-positive). Ganetespib did not graduate in any of the biomarker signatures studied before reaching maximum enrollment. Final estimated pCR rates were 26% vs. 18% HER2-negative, 38% vs. 22% HR-negative/HER2-negative, and 15% vs. 14% HR-positive/HER2-negative for ganetespib vs control, respectively. The predicted probability of success in phase 3 testing was 47% HER2-negative, 72% HR-negative/HER2-negative, and 19% HR-positive/HER2-negative. Ganetespib added to standard therapy is unlikely to yield substantially higher pCR rates in HER2-negative breast cancer compared to standard NAC, and neither HSP90 pathway nor replicative stress expression markers predicted response. HSP90 inhibitors remain of limited clinical interest in breast cancer, potentially in other clinical settings such as HER2-positive disease or in combination with anti-PD1 neoadjuvant chemotherapy in triple negative breast cancer.Trial registration: www.clinicaltrials.gov/ct2/show/NCT01042379.

Development of machine learning models for the screening of potential HSP90 inhibitors

Heat shock protein 90 (Hsp90) is a molecular chaperone playing a significant role in the folding of client proteins. This cellular protein is linked to the progression of several cancer types, including breast cancer, lung cancer, and gastrointestinal stromal tumors. Several oncogenic kinases are Hsp90 clients and their activity depends on this molecular chaperone. This makes HSP90 a prominent therapeutic target for cancer treatment. Studies have confirmed the inhibition of HSP90 as a striking therapeutic treatment for cancer management. In this study, we have utilized machine learning and different in silico approaches to screen the KCB database to identify the potential HSP90 inhibitors. Further evaluation of these inhibitors on various cancer cell lines showed favorable inhibitory activity. These inhibitors could serve as a basis for future development of effective HSP90 inhibitors.

Recent advances in therapeutic strategies for triple-negative breast cancer

Triple-negative breast cancer (TNBC) is the most malignant subtype of breast cancer (BC) with a poor prognosis. Current treatment options are limited to surgery, adjuvant chemotherapy and radiotherapy; however, a proportion of patients have missed the surgical window at the time of diagnosis. TNBC is a highly heterogeneous cancer with specific mutations and aberrant activation of signaling pathways. Hence, targeted therapies, such as those targeting DNA repair pathways, androgen receptor signaling pathways, and kinases, represent promising treatment options against TNBC. In addition, immunotherapy has also been demonstrated to improve overall survival and response in TNBC. In this review, we summarize recent key advances in therapeutic strategies based on molecular subtypes in TNBC.

Estradiol and Estrogen-like Alternative Therapies in Use: The Importance of the Selective and Non-Classical Actions

Estrogen is one of the most important female sex hormones, and is indispensable for reproduction. However, its role is much wider. Among others, due to its neuroprotective effects, estrogen protects the brain against dementia and complications of traumatic injury. Previously, it was used mainly as a therapeutic option for influencing the menstrual cycle and treating menopausal symptoms. Unfortunately, hormone replacement therapy might be associated with detrimental side effects, such as increased risk of stroke and breast cancer, raising concerns about its safety. Thus, tissue-selective and non-classical estrogen analogues have become the focus of interest. Here, we review the current knowledge about estrogen effects in a broader sense, and the possibility of using selective estrogen-receptor modulators (SERMs), selective estrogen-receptor downregulators (SERDs), phytoestrogens, and activators of non-genomic estrogen-like signaling (ANGELS) molecules as treatment.

Steroid sulfatase deficiency causes cellular senescence and abnormal differentiation by inducing Yippee-like 3 expression in human keratinocytes

Human steroid sulfatase (STS) is an enzyme that catalyzes the hydrolysis of dehydroepiandrosterone sulfate (DHEAS), estrone sulfate (E1S), and cholesterol sulfate. Abnormal expression of STS causes several diseases including colorectal, breast, and prostate cancer and refractory skin disease. In particular, accumulation of intracellular cholesterol sulfate by STS deficiency leads to a skin disorder with abnormal keratinization called X-linked ichthyosis (XLI). To determine the detailed mechanisms of XLI, we performed RNA sequencing (RNA-seq) analysis using human keratinocyte HaCaT cells treated with cholesterol and cholesterol sulfate. Of the genes with expression changes greater than 1.5-fold, Yippee-like 3 (YPEL3), a factor expected to affect cell differentiation, was found. Induction of YPEL3 causes permanent growth arrest, cellular senescence, and inhibition of metastasis in normal and tumor cells. In this study, we demonstrate that YPEL3 expression was induced by STS deficiency and, using the CRISPR/Cas9 system, a partial knock-out (STS^+/−) cell line was constructed to establish a disease model for XLI studies. Furthermore, we show that increased expression of YPEL3 in STS-deficient cell lines promoted cellular senescence and expression of keratinization-related proteins such as involucrin and loricrin. Our results suggest that upregulation of YPEL3 expression by STS deficiency may play a crucial role in inducing cellular senescence and abnormal differentiation in human keratinocytes.

Effects of Combinatorial Ubiquitinated Protein-Based Nanovaccine and STING Agonist in Mice With Drug-Resistant and Metastatic Breast Cancer

We previously reported that enriched ubiquitinated proteins (UPs) from tumor cells have the potential to be used as immunotherapy vaccine against cancer. Here we enriched UPs from epirubicin (EPB)-induced multi-drug-resistant cancer stem-like breast cancer cell line (4T1/EPB) and tested the efficacy of α-Al₂O₃-UPs-4T1/EPB (short for UPs-4T1/EPB) as therapeutic vaccine alone and in combination with the stimulator of interferon genes (STING) agonist in mice with drug-resistant and metastatic breast cancer. Vaccination with UPs-4T1/EPB exerted profound anti-tumor effects through augmented specific CD8⁺ T cell responses and amplified T cell receptor diversity of tumor-infiltrating lymphocytes (TILs). Importantly, the combination with STING agonist further facilitated the migration of mature CD8α⁺ dendritic cells to the lymph nodes and the infiltration of TILs within tumors, resulting in primary tumor regression and pulmonary metastasis eradication in mice. Moreover, the cured mice were completely resistant against a subsequent rechallenge with the same tumor. Our study indicates that this novel combinatorial immunotherapy with UPs-4T1/EPB vaccine and STING agonist is effective in mice with drug-resistant and metastatic breast cancer.

Hsp90 inhibitor-loaded IR780 micelles for mitochondria-targeted mild-temperature photothermal therapy in xenograft models of human breast cancer

Mitochondria-targeted mild-temperature photothermal therapy (MT-PTT) is a promising strategy that can maximize anticancer effects and reduce adverse reactions. Here, a novel photosensitizer with mitochondrial targeting based on IR780 iodide and heat shock protein 90 inhibitor (BIIB021), which can passively accumulate in MCF-7 cells and achieve effective MT-PTT effect is synthesized. The prepared PEG-IR780-BIIB021 nano-micelles possess considerable biocompatibility and biological stability, with an encapsulation efficiency of about 84% for BIIB021. They can selectively enrich in mitochondria, and release BIIB021 after NIR irradiation to reduce cell tolerance to heat, thereby reducing the mitochondrial membrane potential and rapidly affecting key intrinsic apoptotic factors (Cyt-C, Caspase-9, Bcl-2 and Bax) to achieve the effect of MT-PTT. It is believed that mitochondria-targeted MT-PTT generated by the PEG-IR780-BIIB021 nano-micelles is a promising therapeutic strategy in clinical practice.

Inhibition of CSF1R and AKT by (±)-kusunokinin hinders breast cancer cell proliferation

Kusunokinin, a lignan compound, inhibits cancer cell proliferation and induces apoptosis; however, the role of kusunokinin is not fully understood. Here, we aimed to identify a target protein of (-)-kusunokinin and determine the protein levels of its downstream molecules. We found that (-)-kusunokinin bound 5 possible target proteins, including CSF1R, MMP-12, HSP90-α, CyclinB1 and MEK1 with ΔG_bind less than -10.40 kcal/mol. MD simulation indicated (-)-kusunokinin and pexidartinib (P31, a specific CSF1R binding compound) shared some extents of functional similarity in which (-)-kusunokinin bound CSF1R at the juxtamembrane (JM) region with aromatic amino acids similar to pexidartinib using π-π interaction, as well as hydrogen bond. Both P31 and (-)-kusunokinin moved into the same CSF1R region and W7 was a mutual key residue. However, the P31 binding site differed from the (-)-kusunokinin binding site. For in vitro study, the synthetic (±)-kusunokinin exhibited stronger cytotoxicity than picropodophyllotoxin, silibinin and etoposide on MCF-7 cells and represented less toxicity than picropodophyllotoxin and doxorubicin on L-929 and MCF-12A cells. Knocking down CSF1R using a specific siRNA combination with (±)-kusunokinin demonstrated levels of cell proliferation proteins slightly higher than siRNA-CSF1R treatment. However, siRNA-CSF1R combination with P31 represented the number of cell viability and cell proliferation proteins, like in the control groups (Lipofectamine and siRNA-Luciferase). Moreover, (±)-kusunokinin suppressed CSF1R and its downstream proteins, including AKT, CyclinD1 and CDK1. Meanwhile, both P31 and siRNA-CSF1R dramatically suppressed CSF1R, MEK1, AKT, ERK, CyclinB1, CyclinD1 and CDK1. Our overall results indicate that the mechanism of (±)-kusunokinin differed fairly from P31. We have concluded that (±)-kusunokinin inhibited breast cancer cell proliferation partially through the binding and suppression of CSF1R, which consequently affected AKT and its downstream molecules.

miR-485-5p/HSP90 axis blocks Akt1 phosphorylation to suppress osteosarcoma cell proliferation and migration via PI3K/AKT pathway

Osteosarcoma (OS) is closely related to the dysregulation of various intracellular signaling pathways, especially the PI3K/Akt signaling pathway. Reportedly, HSP90 was responsible for phospho-Akt stabilization, and both AKT1 and HSP90 were upregulated within osteosarcoma. Herein, we demonstrated that AKT1 and HSP90 mRNA and protein expression were upregulated within osteosarcoma tissues and cells; AKT1 knockdown significantly inhibited OS cell viability. HSP90 knockdown suppressed the phosphorylation of AKT1, decreased ki-67 and Vimentin protein levels, enhanced p21 and E-cadherin protein levels, and inhibited OS cell proliferation and migration; AKT1 overexpression exerted opposing effects and significantly attenuated the effects of HSP90 knockdown. miR-485-5p targeted AKT1 and HSP90 3'-UTR to inhibit AKT1 and HSP90 expression. miR-485-5p overexpression dramatically reduced AKT1, HSP90, and ki-67 proteins, increased E-cadherin protein levels, and inhibited OS cell proliferation and migration. In conclusion, HSP90 knockdown blocked the phosphorylation of AKT1 suppressing the proliferation and migration capacity of OS cells via the PI3K/AKT pathway; miR-485-5p binds to HSP90 and AKT1 in their 3'-UTR to inhibit HSP90 and AKT1 expression, therefore exerting a tumor suppressor function within osteosarcoma.

Identification and Structure-Activity Studies of 1,3-Dibenzyl-2-aryl imidazolidines as Novel Hsp90 Inhibitors

Hsp90 (Heat shock protein 90) is involved in various processes in cancer occurrence and development, and therefore represents a promising drug target for cancer therapy. In this work, a virtual screening strategy was employed, leading to the identification of a series of compounds bearing a scaffold of 1,3-dibenzyl-2-aryl imidazolidine as novel Hsp90 inhibitors. Compound 4a showed the highest binding affinity to Hsp90α (IC50 = 12 nM) in fluorescence polarization (FP) competition assay and the strongest anti-proliferative activity against human breast adenocarcinoma cell line (MCF-7) and human lung epithelial cell line (A549) with IC50 values of 21.58 μM and 31.22 μM, respectively. Western blotting assays revealed that these novel Hsp90 inhibitors significantly down-regulated the expression level of Her2, a client protein of Hsp90, resulting in the cytotoxicity of these novel Hsp90 inhibitors. The molecular docking study showed that these novel Hsp90 inhibitors bound to the adenosine triphosphate (ATP) binding site at the N-terminus of Hsp90. Furthermore, structure-activity relationship studies indicated that the N-benzyl group is important for the anti-cancer activity of 1,3-dibenzyl-2-aryl imidazolidines.

Gold nanoparticles loaded with cullin-5 DNA increase sensitivity to 17-AAG in cullin-5 deficient breast cancer cells

HSP90 inhibitors have the potential to treat many types of cancer due to the dependence of tumor cells on HSP90 for cell growth and proliferation. The Cullin-5 (Cul5) E3 ubiquitin ligase is required for HSP90 inhibitors to induce client protein degradation and subsequent cell death. Cul5 is expressed at low levels in breast cancer cells compared to patient matched controls. This observed low Cul5 expression may play a role in the reported decreased efficacy of 17-AAG and related HSP90 inhibitors as a monotherapy. We have developed a method for delivery of 17-AAG plus Cul5 DNA to cells via gold nanoparticles (AuNPs). Delivery of AuNPs containing Cul5 DNA increases the sensitivity of Cul5 deficient AU565 cells to 17-AAG. Characterization of AuNPs by UV-vis spectrum, TEM, gel electrophoresis assay and ¹H NMR indicate attachment of both 17-AAG and DNA payload as well as AuNP stability. Studies in Cul5 deficient AU565 cells reveal that delivery of Cul5 and 17-AAG together increase cytotoxicity. Our results provide evidence that delivery of DNA with drug may serve as a method to sensitize drug resistant tumor cells.

Spotlight on 17-AAG as an Hsp90 inhibitor for molecular targeted cancer treatment

Hsp90 is a ubiquitous chaperone with important roles in the organization and maturation of client proteins that are involved in the progression and survival of cancer cells. Multiple oncogenic pathways can be affected by inhibition of Hsp90 function through degradation of its client proteins. That makes Hsp90 a therapeutic target for cancer treatment. 17-allylamino-17-demethoxy-geldanamycin (17-AAG) is a potent Hsp90 inhibitor that binds to Hsp90 and inhibits its chaperoning function, which results in the degradation of Hsp90's client proteins. There have been several preclinical studies of 17-AAG as a single agent or in combination with other anticancer agents for a wide range of human cancers. Data from various phases of clinical trials show that 17-AAG can be given safely at biologically active dosages with mild toxicity. Even though 17-AAG has suitable pharmacological potency, its low water solubility and high hepatotoxicity could significantly restrict its clinical use. Nanomaterials-based drug delivery carriers may overcome these drawbacks. In this paper, we review preclinical and clinical research on 17-AAG as a single agent and in combination with other anticancer agents. In addition, we highlight the potential of using nanocarriers and nanocombination therapy to improve therapeutic effects of 17-AAG.

Ultracentrifugation versus kit exosome isolation: nanoLC-MS and other tools reveal similar performance biomarkers, but also contaminations

Aim

For isolation of exosomes, differential ultracentrifugation and an isolation kit from a major vendor were compared.

Materials & methods

'Case study' exosomes isolated from patient-derived cells from glioblastoma multiforme and a breast cancer cell line were analyzed.

Results

Transmission electron microscopy, dynamic light scattering, western blotting, and so forth, revealed comparable performance. Potential protein biomarkers for both diseases were also identified in the isolates using nanoLC-MS. Western blotting and nanoLC-MS also revealed negative exosome markers regarding both isolation approaches.

Conclusion

The two isolation methods had an overall similar performance, but we hesitate to use the term 'exosome isolation' as impurities may be present with both isolation methods. NanoLC-MS can detect disease biomarkers in exosomes and is useful for critical assessment of exosome enrichment procedures.

Network pharmacology-based and clinically relevant prediction of the active ingredients and potential targets of Chinese herbs in metastatic breast cancer patients

Chinese Herbal Medicine (CHM) plays a significant role in breast cancer treatment. We conduct the study to ascertain the relative molecular targets of effective Chinese herbs in treating stage IV breast cancer.Survival benefit of CHM was verified by Kaplan-Meier method and Cox regression analysis. A bivariate correlation analysis was used to find and establish the effect of herbs in complex CHM formulas. A network pharmacological approach was adopted to explore the potential mechanisms of CHM.Patients in the CHM group had a median survival time of 55 months, which was longer than the 23 months of patients in the non-CHM group. Cox regression analysis indicated that CHM was an independent protective factor. Correlation analysis showed that 10 herbs were strongly correlated with favorable survival outcomes (P<0.01). Bioinformatics analyses suggested that the 10 herbs might achieve anti-breast cancer activity primarily through inhibiting HSP90, ERα and TOP-II related pathways.

ATM Is Required for the Prolactin-Induced HSP90-Mediated Increase in Cellular Viability and Clonogenic Growth After DNA Damage

Prolactin (PRL) acts as a survival factor for breast cancer cells, but the PRL signaling pathway and the mechanism are unknown. Previously, we identified the master chaperone, heat shock protein 90 (HSP90) α, as a prolactin-Janus kinase 2 (JAK2)-signal transducer and activator of transcription 5 (STAT5) target gene involved in survival, and here we investigated the role of HSP90 in the mechanism of PRL-induced viability in response to DNA damage. The ataxia-telangiectasia mutated kinase (ATM) protein plays a critical role in the cellular response to double-strand DNA damage. We observed that PRL increased viability of breast cancer cells treated with doxorubicin or etoposide. The increase in cellular resistance is specific to the PRL receptor, because the PRL receptor antagonist, Δ1-9-G129R-hPRL, prevented the increase in viability. Two different HSP90 inhibitors, 17-allylamino-17-demethoxygeldanamycin and BIIB021, reduced the PRL-mediated increase in cell viability of doxorubicin-treated cells and led to a decrease in JAK2, ATM, and phosphorylated ATM protein levels. Inhibitors of JAK2 (G6) and ATM (KU55933) abolished the PRL-mediated increase in cell viability of DNA-damaged cells, supporting the involvement of each, as well as the crosstalk of ATM with the PRL pathway in the context of DNA damage. Drug synergism was detected between the ATM inhibitor (KU55933) and doxorubicin and between the HSP90 inhibitor (BIIB021) and doxorubicin. Short interfering RNA directed against ATM prevented the PRL-mediated increase in cell survival in two-dimensional cell culture, three-dimensional collagen gel cultures, and clonogenic cell survival, after doxorubicin treatment. Our results indicate that ATM contributes to the PRL-JAK2-STAT5-HSP90 pathway in mediating cellular resistance to DNA-damaging agents.

Gastric cancer-derived heat shock protein-gp96 peptide complex enhances dendritic cell activation

AIM

To investigate the role of heat shock protein (HSP)-glycoprotein (gp)96 in dendritic cells (DCs) and lymphocytes induction in gastric cancer (GC).

METHODS

Human GC cell lines KATOIII, MKN-28 and SGC-7901 were infected with adenovirus gp96 at a multiplicity of infection of 100. gp96-GC antigen peptide complexes were purified. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, lactate dehydrogenase (LDH) release assay and enzyme-linked immunosorbent assay were used to determine allo-reactive T cell stimulation, natural killer (NK) cell activity and expression of cytokines (such as interleukin (IL)-10, IL-12, interferon (IFN)-γ and tumor necrosis factor (TNF)-α), respectively. Effect of cytotoxic T lymphocyte (CTL) on DCs incubated with HSP-gp96 was also evaluated by LDH release. All assays were performed in triplicate and the average values were reported. Comparison between groups was conducted using Student’s t test.

RESULTS

T cells incubated with HSP-gp96 exhibited a marked increase in proliferation in a dose-dependent manner (P < 0.05). NK cell activity after gp96-GC peptide complex treatment was significantly higher than that after antigen peptide treatment (P < 0.05). The activity of CTLs incubated with DCs from three GC cells lines was obviously higher than that stimulated by GC antigen at ratios of 50: 1, 25: 1, 10: 1, and 5: 1 (P < 0.05). Furthermore, the secretion of TNF-α, IL-10, IL-12 (P70) and IFN-γ markedly increased after incubation with HSP-gp96 (P < 0.05).

CONCLUSION

HSP-gp96 promotes T cell response, enhances DC antigen presentation and induces cytokine secretion, as well. HSP-gp96 has potential as immunotherapy for elimination of residual GC cells.

Structure-based virtual screening and molecular docking for the identification of potential multi-targeted inhibitors against breast cancer

Breast cancer is characterized by an uncontrolled growth of cells in breast tissue. Genes that foster cell growth in breast cells are overexpressed, giving rise to breast tumors. The identification of effective inhibitors represents a rational chemopreventive strategy. The current in silico study provides a pharmacoinformatic approach for the identification of active compounds against a co-chaperone HSP90 and the human epidermal growth factor receptors EGFR and HER2/neu receptor. The elevated levels of expression of these target proteins have been documented in breast cancer. The utilization of drug-likeness filters helped to evaluate the pharmacological activity of potential lead compounds. Those fulfilling this criterion were subjected to energy minimization for 1000 steepest descent steps at a root means square gradient of 0.02 with an Amber ff12SB force field. Based on molecular docking results and binding interaction analysis, this study represents five chemical compounds (S-258282355, S-258012947, S-259417539, S-258002927, and S-259411474) that indicate high binding energies that range between -8.7 to -10.3 kcal/mol. With high cytochrome P inhibitory promiscuity activity, these multi-targeted potential hits portray not only good physiochemical interactions but also an excellent profile of absorption, distribution, metabolism, excretion, and toxicity, which hypothesizes that these compounds can be developed as anticancer drugs in the near future.

What is known about melatonin, chemotherapy and altered gene expression in breast cancer

Melatonin, synthesized in and released from the pineal gland, has been demonstrated by multiple in vivo and in vitro studies to have an oncostatic role in hormone-dependent tumors. Furthermore, several clinical trials point to melatonin as a promising adjuvant molecule to be considered for cancer treatment. In the past few years, evidence of a broader spectrum of action of melatonin as an antitumor agent has arisen; thus, melatonin appears to also have therapeutic effects in several types of hormone-independent cancer, including ovarian, leukemic, pancreatic, gastric and non-small cell lung carcinoma. In the present study, the latest findings regarding melatonin molecular actions when concomitantly administered with either radiotherapy or chemotherapy in cancer were reviewed, with a particular focus on hormone-dependent breast cancer. Finally, the present study discusses which direction should be followed in the next years to definitely clarify whether or not melatonin administration could protect against non-desirable effects (such as altered gene expression and post-translational protein modifications) caused by chemotherapy or radiotherapy treatments. As treatments move towards personalized medicine, comparative gene expression profiling with and without melatonin may be a powerful tool to better understand the antitumor effects of melatonin, the pineal gland hormone.

Elevated levels of ribosomal proteins eL36 and eL42 control expression of Hsp90 in rhabdomyosarcoma

Mammalian 90 kDa heat shock protein (Hsp90) is a ubiquitous molecular chaperone whose expression is selectively upregulated during stress, although the precise control mechanism of this increase is yet to be fully elucidated. We used polysome profiling to show that Hsp90α mRNA is selectively translated, while global translation is inhibited during heat stress. Furthermore, we have identified 2 ribosomal proteins, eL36 and eL42 that modulate Hsp90α expression under both normal and heat shock conditions. Importantly, we noted that expression of eL36 and eL42 is elevated in a panel of human rhabdomyosarcomas where it drives high expression of Hsp90 and modulates sensitivity of these cells to an Hsp90 inhibitor 17-AAG.

Hsp90-binding immunophilin FKBP51 forms complexes with hTERT enhancing telomerase activity

FK506-binding proteins are members of the immunophilin family of proteins. Those immunophilins associated to the 90-kDa-heat-shock protein, Hsp90, have been proposed as potential modulators of signalling cascade factors chaperoned by Hsp90. FKBP51 and FKBP52 are the best characterized Hsp90-bound immunophilins first described associated to steroid-receptors. The reverse transcriptase subunit of telomerase, hTERT, is also an Hsp90 client-protein and is highly expressed in cancer cells, where it is required to compensate the loss of telomeric DNA after each successive cell division. Because FKBP51 is also a highly expressed protein in cancer tissues, we analyzed its potential association with hTERT·Hsp90 complexes and its possible biological role. In this study it is demonstrated that both immunophilins, FKBP51 and FKBP52, co-immunoprecipitate with hTERT. The Hsp90 inhibitor radicicol disrupts the heterocomplex and favors the partial cytoplasmic relocalization of hTERT in similar manner as the overexpression of the TPR-domain peptide of the immunophilin. While confocal microscopy images show that FKBP51 is primarily localized in mitochondria and hTERT is totally nuclear, upon the onset of oxidative stress, FKBP51 (but not FKBP52) becomes mostly nuclear colocalizing with hTERT, and longer exposure times to peroxide favors hTERT export to mitochondria. Importantly, telomerase activity of hTERT is significantly enhanced by FKBP51. These observations support the emerging role assigned to FKBP51 as antiapoptotic factor in cancer development and progression, and describe for the first time the potential role of this immunophilin favoring the clonal expansion by enhancing telomerase activity.

Calpain Genetic Disruption and HSP90 Inhibition Combine To Attenuate Mammary Tumorigenesis

Calpain is an intracellular Ca(2+)-regulated protease system whose substrates include proteins involved in proliferation, survival, migration, invasion, and sensitivity to therapeutic drugs. Genetic disruption of calpain attenuated the tumorigenic potential of breast cancer cells and hypersensitized cells to 17AAG, an inhibitor of the molecular chaperone HSP90. Calpain-1 or -2 overexpression rendered cells resistant to 17AAG, whereas downregulation or inhibition of calpain-1/2 led to increased cell death in multiple breast cancer cell lines, including models of HER2(+) (SKBR3) and triple-negative basal-cell-like (MDA-MB-231) breast cancer. In an MDA-MB-231 orthotopic xenograft model, calpain knockdown or 17AAG treatment independently attenuated tumor growth and metastasis, while the combination was most effective. Calpain knockdown was associated with increased 17AAG-induced degradation of the HSP90 clients cyclin D1 and AKT and multidrug resistance protein 2, which correlated with increased expression of antimitogenic p27(KIP1) and proapoptotic BIM proteins. Like other therapeutics, 17AAG can be effluxed by specific ABC transporters. Calpain expression positively correlated with the expression of P glycoprotein in mouse embryonic fibroblasts. Importantly, we show that calpain affects ABC transporter function and efflux of clinically relevant doxorubicin. These observations provide a compelling rationale for exploring the combination of calpain inhibition with new or existing cancer therapeutics.

Phase 1B/2 study of the HSP90 inhibitor AUY922 plus trastuzumab in metastatic HER2-positive breast cancer patients who have progressed on trastuzumab-based regimen

This open-label, multicenter, phase 1B/2 trial assessed AUY922 plus trastuzumab in patients with locally advanced or metastatic HER2-positive breast cancer previously treated with chemotherapy and anti-HER2 therapy. This study was composed of a dose-escalation part with AUY922 administered weekly at escalating doses with trastuzumab 2 mg/kg/week (phase 1B), followed by a phase 2 part using the same regimen at recommended phase 2 dose (RP2D). The primary objectives were to determine the maximum tolerated dose (MTD) and/or RP2D (phase 1B), and to evaluate preliminary antitumor activity (phase 2) of AUY922 plus trastuzumab at MTD/RP2D. Forty-five patients were treated with AUY922 plus trastuzumab (4 in phase 1B with AUY922 at 55 mg/m2 and 41 in phase 1B/2 with AUY922 at 70 mg/m2 [7 in phase 1B and 34 in phase 2]). One patient in phase 1B (70 mg/m2) experienced a dose-limiting toxicity (grade 3 diarrhea); the RP2D was weekly AUY922 70 mg/m2 plus trastuzumab. Of the 41 patients in the 70 mg/m2 cohort, the overall response rate (complete or partial responses) was 22.0% and 48.8% patients had stable disease. Study treatment-related adverse events occurred in 97.8% of patients; of these, 31.1% were grade 3 or 4. Forty-one patients (91.1%) reported ocular events (82.3% had grade 1 or 2 events). Two patients (4.4%) had ocular events leading to the permanent discontinuation of study treatment. AUY922 at 70 mg/m2 plus trastuzumab standard therapy is well tolerated and active in patients with HER2-positive metastatic breast cancer who progressed on trastuzumab-based therapy.

HSP90 expression and its association with wighteone metabolite response in HER2-positive breast cancer cells

It is well known that heat shock protein 90 (HSP90) overexpression is correlated with poor prognosis and chemo-resistance in human malignant cancers. At the same time, wighteone, or 6-prenyl-5,7,4'-trihydroxyisoflavone, a major isoflavone component of the ornamental tall tree Erythrina suberosa, has been demonstrated to exhibit a potent anti-proliferative effect on human leukemia HL-60 cancer cell lines. In this study, the effects of wighteone on the proliferation of HER2-positive breast cancer cells were investigated, and the action mechanism was explored. MCF-7 HER2-positive breast cancer cells were treated with various concentrations of wighteone. The growth inhibitory rate of the cells was calculated by MTT assay, apoptosis was detected by flow cytometry, and the expression level of HSP90 was assessed by western blot analysis. The addition of wighteone at concentrations ranging from 1-10 g/ml in the medium for 48 h had a marked inhibition on the proliferation of HER2-positive cancer cell lines. The growth inhibitory rates with 0.5, 2 or 8 mM wighteone were significantly higher compared with the control group. Apoptosis in the wighteone-treated cells was also significantly higher compared with the control group. The expression level of HSP90 in the wighteone group was significantly lower than that in the control group. Our findings demonstrated that wighteone effectively inhibited the proliferation of HER2-positive cancer cell lines, and this is considered to be the result of downregulating HSP90 receptor and downstream signaling.

Hormone receptor positive, HER2 negative metastatic breast cancer: Future treatment landscape

Endocrine therapy is an established and effective treatment strategy for hormone receptor positive metastatic breast cancer. The clinical utility of endocrine therapy is lost over time due to evolving changes in tumor biology and the development of endocrine resistance. Many agents targeting the intracellular signaling pathways associated with endocrine resistance are in development. Encouraging early results have been seen for agents which directly target the estrogen receptor (ER), inhibitors of co-signaling pathways, inhibitors of ER chaperones, ER antagonists able to inhibit mutated or otherwise activated ERs, and modulators of histone acetylation restoring synthesis of ER signaling components. Following our systematic review of treatments with established benefits in this supplement, we review some of the more promising new strategies for overcoming endocrine resistance, looking at the impact on disease control and quality of life for women with hormone receptor positive, HER2 negative breast cancer. We also examine the biomarkers that may guide selection of the best therapy for the individual.

Modulation of expression of heat shock proteins and apoptosis by Flueggea leucopyrus (Willd) decoction in three breast cancer phenotypes

Background

During the past few years, there has been an increasing interest among the Traditional and Folk medical practitioners of Sri Lanka in the use of a decoction prepared from Flueggea leucopyrus (Willd.) for treating various cancers including breast cancer. In the present study, the cytotoxicity of this decoction and its effects on Heat Shock Protein (HSP) expression and apoptosis were compared in three breast cancer phenotypes, to scientifically evaluate if a decoction prepared from F. leucopyrus (Willd.) is useful for the treatment of breast cancer.

Methods

Cytotoxic potential of the F. leucopyrus decoction was determined by evaluating its effects in MCF-7, MDA-MB-231 and SKBR-3 breast cancer cell lines, and MCF-10A (non-cancerous) breast cell line, by use of the Sulphorhodamine (SRB) assay. The effect of the decoction on HSP gene expression in the above cells was evaluated by (a) Real time reverse transcription PCR (RT-PCR) and (b) Immunofluorescence analysis of HSP protein expression. Effects of the decoction on apoptosis were evaluated by (a) fluorescent microscopic examination of apoptosis related morphological changes and (b) DNA fragmentation (c) Caspase 3/7 assay.

Results

F. leucopyrus decoction can mediate significant cytotoxic effects in all three breast cancer cells phenotypes (IC₅₀ values: 27.89, 99.43, 121.43 μg/mL at 24 h post incubation periods, for MCF-7, MDA-MB-231, SKBR-3 respectively) with little effect in the non-cancerous breast cell line MCF-10A (IC₅₀: 570.4 μg/mL). Significant (*P <0.05) inhibitions of HSP 90 and HSP 70 expression were mediated by the decoction in MCF-7 and MDA-MB-231, with little effect in the SKBR-3 cells. Clear apoptotic morphological changes on Acridine orange/Ethidium bromide staining and DNA fragmentation were observed in all three breast cancer cell lines. Caspase 3/7 were significantly (*P <0.05) activated only in MDA-MB-231 and SKBR-3 cells indicating caspase dependent apoptosis in these cells and caspase independent apoptosis in MCF-7 cells.

Conclusions

Modulation of HSP 90 and HSP 70 expressions is a possible mechanism by which the decoction of F. leucopyrus mediates cytotoxic effects MCF-7 and MDA-MB-231 cells. This effect appears to correlate with enhanced apoptosis in these cells. In SKBR-3 cells, mechanisms other than HSP inhibition may be utilized to a greater extent by the decoction to mediate the observed cytotoxic effects. Overall findings suggest that the decoction has the potential to be exploited further for effective treatment of breast cancer.

Potential Prognostic Value of Histone Deacetylase 6 and Acetylated Heat-Shock Protein 90 in Early-Stage Breast Cancer

Purpose

Histone deacetylase 6 (HDAC6) is an enzyme that deacetylates heat-shock protein 90 (HSP90). Many studies have investigated the role of HDAC6 and HSP90 in tumorigenesis and in the prognosis of cancer patients. This study aimed to evaluate the prognostic value of HDAC6 and acetylated HSP90 (acetyl-HSP90) in a cohort of breast cancer patients.

Methods

Immunohistochemical analysis of 314 surgical specimens obtained from patients with invasive breast cancer was carried out to assess standard pathologic factors and the expression of HDAC6 and acetyl-HSP90. Statistical analyses were performed to determine the association between HDAC6, acetyl-HSP90, and conventional clinicopathological factors, and the prognostic values of these factors were evaluated.

Results

HDAC6 expression did not show any correlation with other clinicopathological factors, but acetyl-HSP90 was significantly correlated with histologic grade (p=0.001) and the Ki-67 index (p=0.015). HDAC6 and acetyl-HSP90 expression were significantly associated with each other (p=0.047). Although HDAC6 was not prognostic for disease-free survival (DFS), some patients with high expression of HDAC6 experienced recurrence 5 years after diagnosis, while there was no recurrent disease after 5 years in those with low expression. Acetyl-HSP90 was significantly associated with the DFS of all patients (p=0.016) and with high HDAC6 expression (p=0.017), but not with low expression.

Conclusion

Expression of HDAC6 and acetyl-HSP90 are correlated. HDAC6 is proposed to be a possible predictive marker of late recurrence, and acetyl-HSP90 has prognostic value in predicting the DFS of breast cancer patients.

A dynamic view of ATP-coupled functioning cycle of Hsp90 N-terminal domain

Heat-shock protein 90 (Hsp90) is one of the most important chaperones involved in multiple cellular processes. The chaperoning function of Hsp90 is intimately coupled to the ATPase activity presented by its N-terminal domain. However, the molecular mechanism for the ATP-dependent working cycle of Hsp90 is still not fully understood. In this study, we use NMR techniques to investigate the structural characteristics and dynamic behaviors of Hsp90 N-terminal domain in its free and AMPPCP (ATP analogue) or ADP-bound states. We demonstrated that although AMPPCP and ADP bind to almost the same region of Hsp90, significantly different effects on the dynamics behaviors of the key structural elements were observed. AMPPCP binding favors the formation of the active homodimer of Hsp90 by enhancing the slow-motion featured conformational exchanges of those residues (A117–A141) within the lid segment (A111–G135) and around region, while ADP binding keeps Hsp90 staying at the inactive state by increasing the conformational rigidity of the lid segment and around region. Based on our findings, a dynamic working model for the ATP-dependent functioning cycle of Hsp90 was proposed.

Standard of care and promising new agents for triple negative metastatic breast cancer

Triple negative breast cancer (TNBC) is a cluster of heterogeneous diseases, all of them sharing the lack of expression of estrogen and progesterone receptors and HER2 protein. They are characterized by different biological, molecular and clinical features, including a poor prognosis despite the increased sensitivity to the current cytotoxic therapies. Several studies have identified important molecular features which enable further subdivision of this type of tumor. We are drawing from genomics, transcription and translation analysis at different levels, to improve our knowledge of the molecular alterations along the pathways which are activated during carcinogenesis and tumor progression. How this information should be used for the rational selection of therapy is an ongoing challenge and the subject of numerous research studies in progress. Currently, the vascular endothelial growth factor (VEGF), poly (ADP-ribose) polymerase (PARP), HSP90 and Aurora inhibitors are most used as targeting agents in metastatic setting clinical trials. In this paper we will review the current knowledge about the genetic subtypes of TNBC and their different responses to conventional therapeutic strategies, as well as to some new promising molecular target agents, aimed to achieve more tailored therapies.

Astragalus saponins modulates colon cancer development by regulating calpain-mediated glucose-regulated protein expression

Background

Glucose-regulated proteins (GRP) are induced in the cancer microenvironment to promote tumor survival, metastasis and drug resistance. AST was obtained from the medicinal plant Astragalus membranaceus, which possesses anti-tumor and pro-apoptotic properties in colon cancer cells and tumor xenograft. The present study aimed to investigate the involvement of GRP in endoplasmic reticulum (ER) stress-mediated apoptosis during colon cancer development, with focus on the correlation between AST-evoked regulation of GRP and calpain activation.

Methods

The effects of AST on GRP and apoptotic activity were assessed in HCT 116 human colon adenocarcinoma cells. Calpain activity was examined by using a fluorescence assay kit. Immunofluorescence staining and immunoprecipitation were employed to determine the localization and association between calpains and GRP. GRP78 gene silencing was performed to confirm the importance of GRP in anticancer drug activities. The modulation of GRP and calpains was also studied in nude mice xenograft.

Results

ER stress-mediated apoptosis was induced by AST, as shown by elevation in both spliced XBP-1 and CHOP levels, with parallel up-regulation of GRP. The expression of XBP-1 and CHOP continued to increase after the peak level of GRP was attained at 24 h. Nevertheless, the initial increase in calpain activity as well as calpain I and II protein level was gradually declined at later stage of drug treatment. Besides, the induction of GRP was partly reversed by calpain inhibitors, with concurrent promotion of AST-mediated apoptosis. The knockdown of GRP78 by gene silencing resulted in higher sensitivity of colon cancer cells to AST-induced apoptosis and reduction of colony formation. The association between calpains and GRP78 had been confirmed by immunofluorescence staining and immunoprecipitation. Modulation of GRP and calpains by AST was similarly demonstrated in nude mice xenograft, leading to significant inhibition of tumor growth.

Conclusions

Our findings exemplify that calpains, in particular calpain II, play a permissive role in the modulation of GRP78 and consequent regulation of ER stress-induced apoptosis. Combination of calpain inhibitors and AST could exhibit a more pronounced pro-apoptotic effect. These results help to envisage a new therapeutic approach in colon cancer by targeting calpain and GRP.

Electronic supplementary material

The online version of this article (doi:10.1186/1472-6882-14-401) contains supplementary material, which is available to authorized users.

A physiologically based pharmacokinetic model of alvespimycin in mice and extrapolation to rats and humans

BACKGROUND AND PURPOSE

Alvespimycin, a new generation of heat shock protein 90 (Hsp90) inhibitor in clinical trial, is a promising therapeutic agent for cancer. Pharmacokinetic models of alvespimycin would help in the understanding of drug disposition, predicting drug exposure and interpreting dose-response relationship. In the present study we aimed to develop a physiologically based pharmacokinetic (PBPK) model of alvespimycin in mice and evaluate the utility of the model for predicting alvespimycin disposition in other species.

EXPERIMENTAL APPROACH

A literature search was performed to collect pharmacokinetic data for alvespimycin. A PBPK model was initially constructed to demonstrate the disposition of alvespimycin in mice, and then extrapolated to rats and humans by taking into account the interspecies differences in physiological- and chemical-specific parameters.

KEY RESULTS

A PBPK model, employing a permeability-limited model structure and saturable tissue binding, was built in mice. It successfully characterized the time course of the disposition of alvespimycin in mice. After extrapolation to rats, the model simulated the alvespimycin concentration-time profiles in rat tissues with acceptable accuracies. Likewise, a reasonable match was found between the observed and simulated human plasma pharmacokinetics of alvespimycin.

CONCLUSIONS AND IMPLICATIONS

The PBPK model described here is beneficial to the understanding and prediction of the effects of alvespimycin in different species. It also provides a good basis for further development, which necessitates additional studies, especially those needed to clarify the in-depth mechanism of alvespimycin elimination. A refined PBPK model would benefit the understanding of dose-response relationships and optimization of dosing regimens.

In silico design of small peptide-based Hsp90 inhibitor: a novel anticancer agent

BACKGROUND

Breast cancer is a common disease found among women and has been a serious issue for last two decades. Although various kinds of heat shock proteins (Hsp's) have strong implications in cancer, heat shock protein 90 alpha (Hsp90α) has attracted highest attention for the cause and therapy of breast cancer. It regulates approximately 200 numbers of proteins known as client proteins including large number of oncoproteins found to be upregulated in many cancer cells. Therefore, inhibition of Hsp90α is a common therapeutic approach pursued in many cancers. However, Hsp90α inhibitors both natural and chemical, reported so far are plagued with problems related to toxicity, bioavailability and solubility including geldanamycin, the most common Hsp90α inhibitor. Therefore, search for a suitable Hsp90α inhibitor is an urgent need.

HYPOTHESIS

Here we hypothesize that Hsp organizing protein (HOP) helps in the interaction of Hsp90α with Hsp70, which is the key to appropriate chaperonin function of Hsp90α and therefore, inhibiting such interaction might lead to the disruption of Hsp90α-client protein complex, which in turn destabilize and degrade client proteins. We further hypothesize that considering the residues involved in the reaction we can design novel peptide based Hsp90α inhibitor.

EXPERIMENTAL DESIGN

In our present in silico investigation, we hypothesized that the chaperone function of Hsp90α requires the complex formation with HOP and co-chaperones Hsp70, Hsp40. We performed the docking interaction between Hsp90α and HOP. Based on the key residues involved in the interaction between Hsp90α and HOP, we designed ten peptides having twelve amino acids each. We docked the designed peptides with Hsp90α using docking software Hex 6.1 and the peptide with the highest binding energy value was identified. Using the online FOLDAMYLOID program, we assessed their amyloidogenic propensity. Amylodegenic properties were also considered and based on that five different peptides were again redesigned. Several modifications incorporated onto the peptide led to the design of five different peptides.

RESULTS

The peptide with the lowest amyloidogenic properties and highest binding energy for Hsp90α was the criteria laid for selection as an Hsp90α-inhibitor. Its potential to bind Hsp90α and disrupt Hsp90α-HOP complex was subsequently investigated using both wild as well as mutant p53 as a client protein.

CONCLUSION

The predicted binding energy values showed that our designed novel peptide demonstrated strong binding affinity for Hsp90α. Subsequently, the binding affinity of Hsp90α for mutant p53 was shown to be reduced substantially indicating a strong inhibitory potential of the designed peptide PEP73 (INSAYKLKYARG) for Hsp90α.

Effectively delivering a unique hsp90 inhibitor using star polymers

We report the synthesis of a novel heat shock protein 90 (hsp90) inhibitor conjugated to a star polymer. Using reversible addition-fragmentation chain-transfer (RAFT) polymerization, we prepared star polymers comprised of PEG attached to a predesigned functional core. The stars were cross-linked using disulfide linkers, and a tagged version of our hsp90 inhibitor was conjugated to the polymer core to generate nanoparticles (14 nM). Dynamic light scattering showed that the nanoparticles were stable in cell growth media for 5 days, and HPLC analysis of compound-release at 3 different pH values showed that release was pH dependent. Cell cytotoxicity studies and confocal microscopy verify that our hsp90 inhibitor was delivered to cells using this nanoparticle delivery system. Further, delivery of our hsp90 inhibitor using star polymer induces apoptosis by a caspase 3-dependent pathway. These studies show that we can deliver our hsp90 inhibitor effectively using star polymers, and induce apoptosis by the same pathway as the parent compound.

Risk assessment, disease prevention and personalised treatments in breast cancer: is clinically qualified integrative approach in the horizon?

Breast cancer is a multifactorial disease. A spectrum of internal and external factors contributes to the disease promotion such as a genetic predisposition, chronic inflammatory processes, exposure to toxic compounds, abundant stress factors, a shift-worker job, etc. The cumulative effects lead to high incidence of breast cancer in populations worldwide. Breast cancer in the USA is currently registered with the highest incidence rates amongst all cancer related patient cohorts. Currently applied diagnostic approaches are frequently unable to recognise early stages in tumour development that impairs individual outcomes. Early diagnosis has been demonstrated to be highly beneficial for significantly enhanced therapy efficacy and possibly full recovery. Actual paper shows that the elaboration of an integrative diagnostic approach combining several levels of examinations creates a robust platform for the reliable risk assessment, targeted preventive measures and more effective treatments tailored to the person in the overall task of breast cancer management. The levels of examinations are proposed, and innovative technological approaches are described in the paper. The absolute necessity to create individual patient profiles and extended medical records is justified for the utilising by routine medical services. Expert recommendations are provided to promote further developments in the field.

Heat shock protein 90 (hsp90) expression and breast cancer

Hsp90 is an abundant protein in mammalian cells. It forms several discrete complexes, each containing distinct groups of co-chaperones that assist protein folding and refolding during stress, protein transport and degradation. It interacts with a variety of proteins that play key roles in breast neoplasia including estrogen receptors, tumor suppressor p53 protein, angiogenesis transcription factor HIF-1alpha, antiapoptotic kinase Akt, Raf-1 MAP kinase and a variety of receptor tyrosine kinases of the erbB family. Elevated Hsp90 expression has been documented in breast ductal carcinomas contributing to the proliferative activity of breast cancer cells; whilst a significantly decreased Hsp90 expression has been shown in infiltrative lobular carcinomas and lobular neoplasia. Hsp90 overexpression has been proposed as a component of a mechanism through which breast cancer cells become resistant to various stress stimuli. Therefore, pharmacological inhibition of HSPs can provide therapeutic opportunities in the field of cancer treatment. 17-allylamino,17-demethoxygeldanamycin is the first Hsp90 inhibitor that has clinically been investigated in phase II trial, yielding promising results in patients with HER2-overexpressing metastatic breast cancer, whilst other Hsp90 inhibitors (retaspimycin HCL, NVP-AUY922, NVP-BEP800, CNF2024/BIIB021, SNX-5422, STA-9090, etc.) are currently under evaluation.

TARGETgene: a tool for identification of potential therapeutic targets in cancer

The vast array of in silico resources and data of high throughput profiling currently available in life sciences research offer the possibility of aiding cancer gene and drug discovery process. Here we propose to take advantage of these resources to develop a tool, TARGETgene, for efficiently identifying mutation drivers, possible therapeutic targets, and drug candidates in cancer. The simple graphical user interface enables rapid, intuitive mapping and analysis at the systems level. Users can find, select, and explore identified target genes and compounds of interest (e.g., novel cancer genes and their enriched biological processes), and validate predictions using user-defined benchmark genes (e.g., target genes detected in RNAi screens) and curated cancer genes via TARGETgene. The high-level capabilities of TARGETgene are also demonstrated through two applications in this paper. The predictions in these two applications were then satisfactorily validated by several ways, including known cancer genes, results of RNAi screens, gene function annotations, and target genes of drugs that have been used or in clinical trial in cancer treatments. TARGETgene is freely available from the Biomedical Simulations Resource web site (http://bmsr.usc.edu/Software/TARGET/TARGET.html).

Functions and physiological roles of two types of estrogen receptors, ERα and ERβ, identified by estrogen receptor knockout mouse

Estrogens, a class of steroid hormones, regulate the growth, development, and physiology of the human reproductive system. Estrogens also involve in the neuroendocrine, skeletal, adipogenesis, and cardiovascular systems. Estrogen signaling pathways are selectively stimulated or inhibited depending on a balance between the activities of estrogen receptor (ER) α or ERβ in target organs. ERs belong to the steroid hormone superfamily of nuclear receptors, which act as transcription factors after binding to estrogen. The gene expression regulation by ERs is to modulate biological activities, such as reproductive organ development, bone modeling, cardiovascular system functioning, metabolism, and behavior in both females and males. Understanding of the general physiological roles of ERs has been gained when estrogen levels were ablated by ovariectomy and then replenished by treatment with exogenous estrogen. This technique is not sufficient to fully determine the exact function of estrogen signaling in general processes in living tissues. However, a transgenic mouse model has been useful to study gene-specific functions. ERα and ERβ have different biological functions, and knockout and transgenic animal models have distinct phenotypes. Analysis of ERα and ERβ function using knockout mouse models has identified the roles of estrogen signaling in general physiologic processes. Although transgenic mouse models do not always produce consistent results, they are the useful for studying the functions of these genes under specific pathological conditions.

Short-hairpin RNA-mediated Heat shock protein 90 gene silencing inhibits human breast cancer cell growth in vitro and in vivo

Hsp90 interacts with proteins that mediate signaling pathways involved in the regulation of essential processes such as proliferation, cell cycle control, angiogenesis and apoptosis. Hsp90 inhibition is therefore an attractive strategy for blocking abnormal pathways that are crucial for cancer cell growth. In the present study, the role of Hsp90 in human breast cancer MCF-7 cells was examined by stably silencing Hsp90 gene expression with an Hsp90-silencing vector (Hsp90-shRNA). RT-PCR and Western blot analyses showed that Hsp90-shRNA specifically and markedly down-regulated Hsp90 mRNA and protein expression. NF-kB and Akt protein levels were down-regulated in Hsp90-shRNA transfected cells, indicating that Hsp90 knockout caused a reduction of survival factors and induced apoptosis. Treatment with Hsp90-shRNA significantly increased apoptotic cell death and caused cell cycle arrest in the G1/S phase in MCF-7 cells, as shown by flow cytometry. Silencing of Hsp90 also reduced cell viability, as determined by MTT assay. In vivo experiments showed that MCF-7 cells stably transfected with Hsp90-shRNA grew slowly in nude mice as compared with control groups. In summary, the Hsp90-shRNA specifically silenced the Hsp90 gene, and inhibited MCF-7 cell growth in vitro and in vivo. Possible molecular mechanisms underlying the effects of Hsp90-shRNA include the degradation of Hsp90 breast cancer-related client proteins, the inhibition of survival signals and the upregulation of apoptotic pathways. shRNA-mediated interference may have potential therapeutic utility in human breast cancer.

The novel oral Hsp90 inhibitor NVP-HSP990 exhibits potent and broad-spectrum antitumor activities in vitro and in vivo

A novel oral Hsp90 inhibitor, NVP-HSP990, has been developed and characterized in vitro and in vivo. In vitro, NVP-HSP990 exhibits single digit nanomolar IC(50) values on three of the Hsp90 isoforms (Hsp90α, Hsp90β, and GRP94) and 320 nanomolar IC(50) value on the fourth (TRAP-1), with selectivity against unrelated enzymes, receptors, and kinases. In c-Met amplified GTL-16 gastric tumor cells, NVP-HSP990 dissociated the Hsp90-p23 complex, depleted client protein c-Met, and induced Hsp70. NVP-HSP990 potently inhibited the growth of human cell lines and primary patient samples from a variety of tumor types. In vivo, NVP-HSP990 exhibits drug-like pharmaceutical and pharmacologic properties with high oral bioavailability. In the GTL-16 xenograft model, a single oral administration of 15 mg/kg of NVP-HSP990 induced sustained downregulation of c-Met and upregulation of Hsp70. In repeat dosing studies, NVP-HSP990 treatment resulted in tumor growth inhibition of GTL-16 and other human tumor xenograft models driven by well-defined oncogenic Hsp90 client proteins. On the basis of its pharmacologic profile and broad-spectrum antitumor activities, clinical trials have been initiated to evaluate NVP-HSP990 in advanced solid tumors.

Interaction of natural products with cell survival and signaling pathways in the biochemical elucidation of drug targets in cancer

The use of natural products with therapeutic properties is as ancient as human civilization and for a long time mineral, plant and animal products were the main sources of drugs. Worldwide sales of medicinal plants, crude extracts and finished products amounted to US$15 billion in 1999 and it increased to $23 billion in 2002. More interestingly, the influence of natural products upon anticancer drug discovery and design cannot be underestimated. Approximately 60% of all drugs in clinical trials are either a natural product, compounds derived from natural products or contain pharmacophores derived from active natural products. Thus, even today, in the presence of massive numbers of agents from combinatorial libraries, compounds from natural sources are still in the forefront of cancer chemotherapeutics as sources of active drug types, as well as being involved in drug discovery in diseases such as microbial and parasitic infections and the control of cholesterol/lipids, among other functions.

Andrographolide targets androgen receptor pathway in castration-resistant prostate cancer

Androgen receptor (AR) signaling not only plays a pivotal role in the development of androgen-dependent prostate cancer but is also important in the growth and survival of castration-resistant prostate cancer (CRPC). The first line of treatment of androgen-dependent prostate cancer is the use of androgen deprivation therapy. However, most patients will eventually relapse due to development of CRPC. Thus, development of a strategy to target AR for treatment of CRPC is urgently needed. The authors have previously identified andrographolide as an inhibitor of interleukin-6, which can suppress tumor growth of prostate cancer cells by screening compounds from the Prestwick Natural compound library. In this study, they identified that andrographolide can inhibit AR expression and prostate cancer cell growth and induce apoptosis. Andrographolide is able to down-regulate AR expression at both mRNA and protein levels, prevents its nuclear translocation, and inhibits transactivation of its target genes. Andrographolide prevents the binding of Hsp90 to AR, resulting in proteasome-mediated AR degradation. Furthermore, andrographolide inhibits castration-resistant C4-2 cell growth by reducing AR expression and activity. Thus, andrographolide can be developed as a potential therapeutic agent for prostate cancer by inhibition of androgen receptor signaling.

Degradable Cross-Linked Nanoassemblies as Drug Carriers for Heat Shock Protein 90 Inhibitor 17-N-Allylamino-17-demethoxy-geldanamycin

Cross-linked nanoassemblies (CNAs) with a degradable core were prepared for sustained release of 17-N-allylamino-17-demethoxygeldanamycin (17-AAG), a potent inhibitor of heat shock protein 90 (HSP90). The particle size of CNAs ranged between 100 and 250 nm, which changed depending on the cross-linking yields and drug entrapment method. CNAs with a 1% cross-linking yield entrapped 17-AAG in aqueous solutions, yet degraded in 3 hrs. CNAs entrapped 5.2 weight% of 17-AAG as the cross-linking yield increased to 10%, retaining more than 80% of particles for 24 hrs. CNAs with drugs entrapped after the cross-linking reactions were 100 nm and remained stable in both pH 7.4 and 5.0, corresponding to the physiological, tumoral, and intracellular environments. Drug was completely released from CNAs in 48 hrs, which would potentially maximize drug delivery and release efficiency within tumor tissues. Drug release patterns were not negatively affected by changing the cross-linking yields of CNAs. CNAs entrapping 17-AAG suppressed the growth of human non-small cell lung cancer A549 cells as equally effective as free drugs. The results demonstrated that CNAs would be a promising formulation that can be used in aqueous solutions for controlled delivery and release of 17-AAG.

Effective targeting of triple-negative breast cancer cells by PF-4942847, a novel oral inhibitor of Hsp 90

PURPOSE

Triple-negative breast cancer (TNBC) patients have poor prognoses and survival outcomes such that the development of new targeted therapies is in strong demand. Mechanisms associated with high proliferation and aggressive tumor progression, such as PI3K/PTEN aberration, epidermal growth factor receptor (EGFR) overexpression, and cell-cycle upregulation, play important roles in TNBC. The molecular chaperone Hsp90 is required for the conformational maturation and stability of a variety of proteins in multiple pathways, such as EGFR, AKT, Raf, cdk4, etc. Therefore, an Hsp90 inhibitor may show therapeutic benefit in TNBC by targeting multiple pathways.

EXPERIMENTAL DESIGN

The novel oral Hsp90 inhibitor PF-4942847 was characterized in multiple in vitro and in vivo assays to determine its antitumor activity in TNBC cell lines. In addition, the correlation of AKT degradation and Hsp70 induction in host peripheral blood lymphocytes (PBL) and xenograft tumors was determined.

RESULTS

PF-4942847 induces degradation of multiple client proteins, cell-cycle block, apoptosis, and inhibits cell proliferation in TNBC lines, subsequently leading to tumor growth inhibition in mouse xenograft models. The correlation of AKT degradation and Hsp70 induction between PBLs and xenograft tumors reveals a differential modulation of Hsp90 activity between host and tumor tissues, and suggests that AKT degradation in PBLs may serve as a pharmacodynamic biomarker in future clinical development.

CONCLUSIONS

The novel oral Hsp90 inhibitor, PF-4942847, is a candidate for clinical development in TNBC by collaboratively targeting multiple signaling pathways. In addition, AKT degradation in PBLs may serve as a biomarker in clinical development.

Mixed pH-sensitive polymeric micelles for combination drug delivery

PURPOSE

To prepare mixed polymeric micelles that can carry two different drugs, doxorubicin (DOX) and 17-hydroxyethylamino-17-demethoxygeldanamycin (GDM-OH), for combination cancer chemotherapy.

METHODS

The pH-sensitive micelles were prepared from poly(ethylene glycol)-poly(aspartate hydrazide) block copolymers to which either DOX or GDM-OH is conjugated through acid-labile hydrazone bond (individual micelles). Mixed micelles were formed not only by simply mixing two different individual micelles in aqueous solutions (aqueous mixed micelles) but also by evaporating organic solvents from the organic/aqueous mixed solvents in which two block copolymers possessing different drugs were dissolved homogeneously (organic mixed micelles). Particle size measurements, pH-dependent drug release tests, cytotoxicity assays and western blot analysis were subsequently conducted.

RESULTS

Individual and aqueous/organic mixed micelles showed clinically relevant particle size (<100 nm) and pH-dependent drug release patterns. Mixed polymer micelles suppress cancer cell growth effectively in a drug concentration, mixing method and schedule-dependent way.

CONCLUSION

Combination chemotherapy using polymeric micelles seems to minimize a schedule-dependent change in combination drug efficacy in comparison to drug combination using DMSO formulations.

Decreased Hsp90 expression in infiltrative lobular carcinoma: an immunohistochemical study

BACKGROUND

Elevated Hsp90 expression has been documented in breast ductal carcinomas, whereas decreased Hsp90 expression has been reported in precursor lobular lesions. This study aims to assess Hsp90 expression in infiltrative lobular carcinomas of the breast.

METHODS

Tissue specimens were taken from 32 patients with infiltrative lobular carcinoma. Immunohistochemical assessment of Hsp90 was performed both in the lesion and the adjacent normal breast ducts and lobules; the latter serving as control. Concerning Hsp90 assessment: i) the percentage of positive cells and ii) the intensity were separately analyzed. Subsequently, the Allred score was adopted and calculated. The intensity was treated as an ordinal variable-score (0: negative, low: 1, moderate: 2, high: 3). Statistical analysis followed.

RESULTS

All infiltrative lobular carcinoma foci mainly presented with a positive cytoplasmic immunoreaction for Hsp90. Compared to the adjacent normal ducts and lobules, infiltrative lobular carcinoma exhibited a statistically significant decrease in Hsp90 expression, both in terms of Hsp90 positive cells (%) and Allred score (74.2 +/- 11.2 vs. 59.1 +/- 14.2 p = 0.0001; 7.00 +/- 0.95 vs. 6.22 +/- 1.01, p = 0.007, Wilcoxon matched-pairs signed-ranks test). Concerning the intensity of Hsp90 immunostaining only a marginal decrease was noted (2.16 +/- 0.68 vs. 1.84 +/- 0.63, p = 0.087, Wilcoxon matched-pairs signed-ranks test).

CONCLUSION

ILC lesions seem to exhibit decreased Hsp90 expression, a finding contrary to what might have been expected, given that high Hsp90 expression is a trait of invasive ductal carcinomas.