Heat shock proteins as targets in oncology

Dual targeting of HSP90 and BCL-2 in breast cancer cells using inhibitors BIIB021 and ABT-263

PURPOSE

The incidence of breast cancer has been increasing in recent years, and monotherapy approaches are not sufficient alone in the treatment of breast cancer. In the combined therapy approach, combining two or three different agents in lower doses can mitigate the side effects on living cells and tissues caused by high doses of chemical agents used alone. ABT-263 (navitoclax), a clinically tested Bcl-2 family protein inhibitor, has shown limited success in clinical trials due to the development of resistance to monotherapy in breast cancer cells. This resistance shows that monotherapy approaches are inadequate and more effective treatment strategies are needed. It is the ability of HSP90 inhibitors to destabilize many oncoproteins that are critical for the survival of cancer cells. This study aimed to examine the anticancer activity of the combination of ABT-263 with BIIB021, a new generation HSP90 inhibitor, on two widely used breast cancer cell lines: MCF-7 (ER-positive) and MDA-MB-231 (triple-negative breast cancer, TNBC). These cell lines were selected to represent distinct breast cancer subtypes with different molecular characteristics and clinical behaviors.

METHODS

Single and combined cytotoxic effects of this agents on MCF-7 and MDA-MB-231 breast cancer cell lines were determined using the MTT cell viability test. The combined use of these two agents showed a synergistic effect, and this effect was assigned using the Chou and Talalay method. mRNA and protein levels of apoptosis-related genes Bax, Bcl-2, Casp9, and Heat Shock Proteins HSP27, HSP70, and HSP90 were analyzed using Quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) and Western Blotting, respectively.

RESULTS

The cytotoxicity analysis, combined with the application of the Chou-Talalay method, demonstrated that the BIIB021 and ABT-263 combination exhibited significantly greater anticancer activity compared to the individual effects of either BIIB021 or ABT-263 in breast cancer cell lines. The analysis of mRNA and protein levels indicated that the BIIB021+ABT-263 combination may have triggered the intrinsic apoptotic pathway in breast cancer cells.

CONCLUSION

This study showed that co-administration of ABT-263 and BIIB021 agents exhibited synergistic cytotoxic effects and increased the expression of apoptosis-related genes in breast cancer cell lines.

Ligand-based pharmacophore modelling, structure optimisation, and biological evaluation for the identification of 2-heteroarylthio-N-arylacetamides as novel HSP90 C-terminal inhibitors

Targeting Heat shock protein 90 (HSP90) C-terminus is an important strategy to develop HSP90 inhibitors without inducing heat shock response. The development of C-terminal inhibitors, however, is hampered by a lack of understanding regarding the interaction between the HSP90 C-terminus and the present inhibitors. We collected seven classical and structurally diverse HSP90 C-terminal inhibitors and constructed a ligand-based pharmacophore model. The subsequent virtual screening and structural optimisation led to the identification of 2-heteroarylthio-N-arylacetamides as novel HSP90 C-terminal inhibitors. 9 and 27 exhibited strong antitumour activity in vitro by inhibiting proliferation and inducing apoptosis in multiple cancer cell lines. These compounds disrupted the interaction between HSP90 C-terminus and peptidylprolyl isomerase D, exerting a stronger inhibitory effect than novobiocin. 27 significantly induced the degradation of HSP90 clients without triggering heat shock response. In an in vivo study using 4T1 mice breast cancer models, 9 showed a potent antitumour effect without obvious toxicity.

Heat shock proteins as a new, promising target of multiple myeloma therapy

Introduction: The results of therapy of the multiple myeloma (MM) patients remain unsatisfactory despite the constantly observed progress in treatment.Areas covered: It has been shown that mechanisms regulated by heat shock proteins (HSPs) play an important role in pathogenesis of MM and resistance developing to treatment, which constitute a protective shield against external damaging factors in healthy and cancerous cells.Expert opinion: Inhibiting these mechanisms seems to be the natural way of therapy in MM patients. In vitro studies have shown promising effects in the form of an increase in the apoptosis index of MM cells exposed to HSP inhibitors. The observations are very promising in the early stages of clinical trials with HSP inhibitors, such as tanespimycin, in the relapsed/refractory MM patients. Effects were more pronounced when combined with bortezomib. It seems that enriching the range of anti-myeloma drugs with HSP inhibitors may be the next step in the future of extending life of patients with multiple myeloma.

Cysteine Proteases from V. cundinamarcensis (C. candamarcensis) Inhibit Melanoma Metastasis and Modulate Expression of Proteins Related to Proliferation, Migration and Differentiation

Previous studies showed that P1G10, a proteolytic fraction from Vasconcellea cundinamarcensis latex, reduced the tumor mass in animals bearing melanoma, increased in vitro DNA fragmentation and decreased cell adhesion. Here, we present some molecular and cellular events related to the antimetastatic effect induced by the CMS-2 fraction derived from P1G10 in metastatic melanoma B16-F10 and melanocyte Melan-a. Using difference gel electrophoresis and mass spectrometry, we identified four proteins overexpressed in tumor cells, all of them related to proliferation, survival, migration and cell invasion, that had their expression normalized upon treatment with CMS-2: nucleophosmin 1, heat shock protein 65, calcyclin binding protein and eukaryotic translation initiation factor 4H. In addition, some antioxidant and glycolytic enzymes show increased expression after exposure to CMS-2, along with an induction of melanogenesis (differentiation marker). The down regulation of cofilin 1, a protein involved in cell motility, may explain the inhibition of cell migration and dendritic-like outgrowth in B16-F10 and Melan-a, observed after CMS-2 treatment. Taken together, it is argued that CMS-2 modulates the expression of proteins related to metastatic development, driving the cell to a more differentiated-like state. These effects support the CMS-2 antimetastatic activity and place this fraction in the category of anticancer agent.

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

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

Suppression of heat shock protein 70 by siRNA enhances the antitumor effects of cisplatin in cultured human osteosarcoma cells

Although advances in chemotherapy have improved the prognosis for osteosarcoma, some patients do not respond sufficiently to treatment. Heat shock protein 70 (Hsp70) is expressed at high levels in cancer cells and attenuates the therapeutic efficacy of anticancer agents, resulting in a poorer prognosis. This study investigated whether small interfering RNA (siRNA)-mediated inhibition of Hsp70 expression in an osteosarcoma cell line would enhance sensitivity to cisplatin. The expression of Hsp70 with cisplatin treatment was observed by using Western blotting and real-time reverse transcription polymerase chain reaction (RT-PCR). Changes in the IC50 of cisplatin when Hsp70 was inhibited by siRNA were evaluated. Cisplatin's effectiveness in inducing apoptosis was assessed by assay of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL), caspase-3 activity, and mitochondrial membrane potential. Up-regulation of Hsp70 expression was dependent on the concentration of cisplatin. Inhibition of Hsp70 expression significantly reduced the IC50 of cisplatin. When cisplatin was added to osteosarcoma cells with Hsp70 expression inhibited, a significant increase in apoptosis was demonstrated in TUNEL, caspase-3, and mitochondrial membrane potential assays. Inhibition of Hsp70 expression induced apoptosis in cultured osteosarcoma cells, indicating that Hsp70 inhibition enhanced sensitivity to cisplatin. Inhibition of Hsp70 expression may provide a new adjuvant therapy for osteosarcoma.

Glioma progression through the prism of heat shock protein mediated extracellular matrix remodeling and epithelial to mesenchymal transition

Glial tumor is one of the intrinsic brain tumors with high migratory and infiltrative potential. This essentially contributes to the overall poor prognosis by circumvention of conventional treatment regimen in glioma. The underlying mechanism in gliomagenesis is bestowed by two processes- Extracellular matrix (ECM) Remodeling and Epithelial to mesenchymal transition (EMT). Heat Shock Family of proteins (HSPs), commonly known as "molecular chaperons" are documented to be upregulated in glioma. A positive correlation also exists between elevated expression of HSPs and invasive capacity of glial tumor. HSPs overexpression leads to mutational changes in glioma, which ultimately drive cells towards EMT, ECM modification, malignancy and invasion. Differential expression of HSPs - a factor providing cytoprotection to glioma cells, also contributes towards its radioresistance /chemoresistance. Various evidences also display upregulation of EMT and ECM markers by various heat shock inducing proteins e.g. HSF-1. The aim of this review is to study in detail the role of HSPs in EMT and ECM leading to radioresistance/chemoresistance of glioma cells. The existing treatment regimen for glioma could be enhanced by targeting HSPs through immunotherapy, miRNA and exosome mediated strategies. This could be envisaged by better understanding of molecular mechanisms underlying glial tumorigenesis in relation to EMT and ECM remodeling under HSPs influence. Our review might showcase fresh potential for the development of next generation therapeutics for effective glioma management.

Modification of the hTERT promoter by heat shock elements enhances the efficiency and specificity of cancer targeted gene therapy

PURPOSE

One of the current challenges facing cancer gene therapy is the tumour-specific targeting of therapeutic genes. Effective targeting in gene therapy requires accurate spatial and temporal control of gene expression. To develop a sufficient and accurate tumour-targeting method for cancer gene therapy, we have investigated the use of hyperthermia to control the expression of a transgene under the control of the human telomerase reverse transcriptase (hTERT) promoter and eight heat shock elements (8HSEs).

MATERIALS AND METHODS

Luciferase reporters were constructed by inserting eight HSEs and the hTERT promoter (8HSEs-hTERTp) upstream of the pGL4.20 vector luciferase gene. The luciferase activity of the hTERT promoter and 8HSEs-hTERT promoter were then compared in the presence and absence of heat. The differences in luciferase activity were analysed using dual luciferase assays in SW480 (high hTERT expression), MKN28 and MRC-5 cells (low hTERT expression). The luciferase activity of the Hsp70B promoter was also compared to the 8HSEs-hTERT promoter in the above listed cell lines. Lentiviral vector and heat-induced expression of EGFP expression under the control of the 8HSEs-hTERT promoter in cultured cells and mouse tumour xenografts was measured by reverse transcription polymerase (RT-PCR), Western blot and immunofluorescence assays.

RESULTS

hTERT promoter activity was higher in SW480 cells than in MKN28 or MRC-5 cells. At 43 °C, the luciferase activity of the 8HSEs-hTERT promoter was significantly increased in SW480 cells, but not in MKN28 or MRC-5 cells. Importantly, the differences in luciferase activity were much more obvious in both high (SW480) and low (MKN28 and MRC-5) hTERT expressing cells when the activity of the 8HSEs-hTERT promoter was compared to the Hsp70B promoter. Moreover, under the control of 8HSEs-hTERT promoter in vitro and in vivo, EGFP expression was obviously increased by heat treatment in SW480 cells but not in MKN28 or MRC-5 cells, nor was expression increased under normal temperature conditions.

CONCLUSIONS

The hTERT promoter is a potentially powerful tumour-specific promoter and gene therapy tool for cancer treatment. Incorporating heat-inducible therapeutic elements (8HSEs) into the hTERT promoter may enhance the efficiency and specificity of cancer targeting gene therapy under hyperthermic clinical conditions.

Heat shock protein 90 inhibitors induce functional inhibition of human natural killer cells in a dose-dependent manner

Heat shock protein 90 (Hsp90) is a ubiquitously expressed ATP-dependent molecular chaperone across all species that helps to the correct the folding of many proteins related to important signaling pathways. Tumor cells expressing Hsp90 have more ATP-binding affinity than normal cells. Many correlative inhibitors have been developed to promising anti-tumor strategies and have been evaluated in clinical trials. However, the effect of Hsp90 inhibitors on immunocytes cannot be ignored. Natural killer (NK) cells are key components of the innate immune system that play a pivotal role in tumor surveillance. The present study has investigated the potential effect of four Hsp90 inhibitors (NVP-AUY922, BIIB021, 17-DMAG, and SNX-2112) on human primary NK cells. The viability, cytotoxicity, apoptosis, phenotype, and cytokine secretion of NK cells after inhibitor treatment were assessed. The results of this study demonstrated that the inhibitors had negative effects on NK cell activity in a dose-dependent manner. The four inhibitors significantly reduced the cytotoxicity of the NK cells by decreasing viability, inducing apoptosis and down-regulating the expression of cytokines and functional receptors. These findings suggest that more attention should be given to the effect of Hsp90 inhibitors on NK cell function during clinical trials and also represent a potential immunosuppressant strategy.

Druggable targets in pediatric neurocutaneous melanocytosis: Molecular and drug sensitivity studies in xenograft and ex vivo tumor cell culture to identify agents for therapy

BACKGROUND

Neurocutaneous melanocytosis (NCM) is a rare congenital disorder that presents with pigmented cell lesions of the brain or leptomeninges in children with large or multiple congenital melanocytic nevi. Although the exact pathological processes involved are currently unclear, NCM appears to arise from an abnormal development of melanoblasts or melanocyte precursors. Currently, it has an extremely poor prognosis due to rapid disease progression and lack of effective treatment modalities.

METHODS

In this study, we report on an experimental approach to examining NCM cells by establishing subcutaneous tumors in nude mice, which can be further expanded for conducting molecular and drug sensitivity experiments.

RESULTS

Analysis of the NRAS gene-coding sequences of an established NCM cell line (YP-MEL) and NCM patient cells revealed heterogeneity in NRAS Q61K that activated mutation and possibly consequential differential sensitivity to MEK inhibition. Gene expression studies were performed to compare the molecular profiles of NCM cells with normal skin fibroblasts. In vitro cytotoxicity screens of libraries of targeted small-molecule inhibitors revealed prospective agents for further evaluation.

CONCLUSIONS

Our studies provide an experimental platform for the generation of NCM cells for preclinical studies and the production of molecular and in vitro data with which to identify druggable targets for the treatment.

Co-overexpression of Hsp90-β and annexin A1 with a significantly positive correlation contributes to the diagnosis of lung cancer

AIM

Hsp90-β and annexin A1 have been demonstrated to be associated with tumorigenesis. However, the effect of Hsp90-β and annexin A1 in lung cancer remains poorly understood. In this research, the correlation of Hsp90-β and annexin A1 in lung cancer patients were analyzed.

METHODS

The expression levels of Hsp90-β and annexin A1 were examined by immunohistochemistry and ELISA.

RESULTS

Lung cancer tissues and serum exhibited higher co-expression of Hsp90-β and annexin A1 than control groups (p < 0.05). Hsp90-β and annexin A1 could discriminate lung cancer from the control groups (sensitivity of Hsp90-β was 80.2% in tissues and 96% in serum; specificity of Hsp90-β was 80% in tissues and 83.33% in serum; sensitivity of annexin A1 was 68.76% in tissues and 95.23% in serum; specificity of annexin A1 was 75% in tissues and 85.7% in serum) and multi-index combined detection had a better diagnostic value.

CONCLUSION

The expression levels of Hsp90-β and annexin A1 positively correlated and such co-overexpression of Hsp90-β and annexin A1 contributed to lung cancer diagnosis.

Clinical presentation, pathogenesis, diagnosis, and treatment of epidermolysis bullosa acquisita

Epidermolysis bullosa acquisita (EBA) is a chronic mucocutaneous autoimmune skin blistering disease. The pathogenic relevance of autoantibodies targeting type VII collagen (COL7) has been well-documented. Therefore, EBA is a prototypical autoimmune disease with a well-characterized pathogenic relevance of autoantibody binding to the target antigen. EBA is a rare disease with an incidence of 0.2 new cases per million and per year. The current treatment of EBA relies on general immunosuppressive therapy, which does not lead to remission in all cases. Therefore, there is a high, so far unmet medical need for the development of novel therapeutic options. During the last 10 years, several novel in vitro and in vivo models of EBA have been established. These models demonstrated a critical role of the genetic background, T cells, and cytokines for mediating the loss of tolerance towards COL7. Neutrophils, complement activation, Fc gamma receptor engagement, cytokines, several molecules involved in cell signaling, release of reactive oxygen species, and matrix metalloproteinases are crucial for autoantibody-induced tissue injury in EBA. Based on this growing understanding of the diseases' pathogenesis, several potential novel therapeutic targets have emerged. In this review, the clinical presentation, pathogenesis, diagnosis, and current treatment options for EBA are discussed in detail.

Hsp90-targeted miRNA-liposomal formulation for systemic antitumor effect

Chaperone protein Hsp90 maintains functional integrity and maturation of a large number of cellular proteins including transcription factors, kinases, etc. It is often over-expressed in cancer cells for simultaneous maintenance of many non-regulated and/or genetically mutated proteins. Small molecule-based regimens inhibiting over-expressing Hsp90 in cancer cells often plagued with improper targeting leading to non-specific toxicity. Recently using a glucocorticoid receptor (GR)-targeted cationic lipoplex, we observed cancer cell-specific GR-transactivation and transgene expression by utilizing an unprecedentedly compromised chaperone-activity of cancer cell-associated Hsp90. In normal cells, GR is expressed ubiquitously and is highly regulated and chaperoned by Hsp90. This does not allow cancer cell-alike GR-mediated transgene expression. As a novel anticancer strategy, we showed that compromising Hsp90 in cancer cells can be utilized to selectively deplete its own level by delivering a specially designed artificial miRNA-plasmid against Hsp90 (amiR-Hsp90). Practically, GR-mediated delivery of amiR-Hsp90 plasmid in tumor-bearing mice, depleted Hsp90, critically down-regulated levels of Akt, VEGFR2 and other Hsp90-client proteins but up-regulated wild-type p53 in tumor. These enforced apoptosis in angiogenic vessels and in tumor mass and significantly shrunk tumor-volume. The present study describes gene therapy strategy against Hsp90 using a new GR-targeted liposome-amiR-Hsp90 lipoplex formulation for treating cancer.

Heat shock protein 90 is critical for regulation of phenotype and functional activity of human T lymphocytes and NK cells

The 90-kDa heat shock protein (Hsp90) has become an important therapeutic target with ongoing evaluation in a number of malignancies. Although Hsp90 inhibitors have a high therapeutic index with limited effects on normal cells, they have been described to inhibit dendritic cell function. However, its effect on human immune effector cells may have significant clinical implications, but remains unexplored. In this study, we have evaluated the effects of Hsp90 inhibition on human T lymphocyte and NK cells, including their Ag expression, activation, proliferation, and functional activities. These studies demonstrate that Hsp90 inhibition irreversibly downregulates cell surface expression of critical Ags (CD3, CD4, CD8), the costimulatory molecule (CD28, CD40L), and αβ receptors on T lymphocytes, as well as activating receptors (CD2, CD11a, CD94, NKp30, NKp44, NKp46, KARp50.3) on NK cells. Hsp90 inhibition significantly reduced CD4 protein expression on T lymphocytes at both the cell surface and intracellular level, which was shown to be associated with aberrant regulation of Src-kinase p56(Lck). Downregulation of the Ags triggered by Hsp90 inhibition on CD3(+) T lymphocytes, both in CD4(+) and CD8(+) T cell subsets, was associated with a disruption in their cellular activation, proliferation, and/or IFN-γ production, when the inhibition occurred either in activated or inactivated cells. In addition, downregulation of key activating receptors on NK cells following Hsp90 inhibition resulted in decreased cytotoxicity against tumor cells. Therefore, these observations demonstrate the need to closely monitor immune function in patients being treated with a Hsp90 inhibitor and may provide a potential therapeutic application in autoimmune diseases.

Proteome analysis identified the PPARγ ligand 15d-PGJ2 as a novel drug inhibiting melanoma progression and interfering with tumor-stroma interaction

Peroxisome proliferator-activated receptors (PPARs) have been originally thought to be restricted to lipid metabolism or glucose homeostasis. Recently, evidence is growing that PPARγ ligands have inhibitory effects on tumor growth. To shed light on the potential therapeutic effects on melanoma we tested a panel of PPAR agonists on their ability to block tumor proliferation in vitro. Whereas ciglitazone, troglitazone and WY14643 showed moderate effects on proliferation, 15d-PGJ2 displayed profound anti-tumor activity on four different melanoma cell lines tested. Additionally, 15d-PGJ2 inhibited proliferation of tumor-associated fibroblasts and tube formation of endothelial cells. 15d-PGJ2 induced the tumor suppressor gene p21, a G₂/M arrest and inhibited tumor cell migration. Shot gun proteome analysis in addition to 2D-gel electrophoresis and immunoprecipitation of A375 melanoma cells suggested that 15d-PGJ2 might exert its effects via modification and/or downregulation of Hsp-90 (heat shock protein 90) and several chaperones. Applying the recently established CPL/MUW database with a panel of defined classification signatures, we demonstrated a regulation of proteins involved in metastasis, transport or protein synthesis including paxillin, angio-associated migratory cell protein or matrix metalloproteinase-2 as confirmed by zymography. Our data revealed for the first time a profound effect of the single compound 15d-PGJ2 on melanoma cells in addition to the tumor-associated microenvironment suggesting synergistic therapeutic efficiency.

The heat shock protein 90 inhibitor 17-AAG suppresses growth and induces apoptosis in human cholangiocarcinoma cells

The aim of this study was to investigate the effects of 17-Allylamino-17-demethoxygeldanamycin (17-AAG), a heat shock protein 90 (HSP90) inhibitor, on the proliferation, cell cycle, and apoptosis of human cholangiocarcinoma (CCA) cells. Cell proliferation and cell cycle distribution were measured by the MTT assay and flow cytometry analysis, respectively. Induction of apoptosis was determined by flow cytometry and Hoechst staining. The expressions of cleaved poly ADP-ribose polymerase (PARP), Bcl-2, Survivin, and Cyclin B1 were detected by Western blot analysis. The activity of caspase-3 was also examined. We found that 17-AAG inhibited cell growth and induced G2/M cell cycle arrest and apoptosis in CCA cells together with the down-regulation of Bcl-2, Survivin and Cyclin B1, and the up-regulation of cleaved PARP. Moreover, increased caspase-3 activity was also observed in CCA cells treated with 17-AAG. In conclusion, our data suggest that the inhibition of HSP90 function by 17-AAG may provide a promising therapeutic strategy for the treatment of human CCA.

Upregulation of Hsp90-beta and annexin A1 correlates with poor survival and lymphatic metastasis in lung cancer patients

Background

Hsp90-beta and annexin A1 were investigated as prognostic factors because of their apparent association with tumorigenesis. However, the effect of Hsp90-beta and annexin A1 in lung cancer remains poorly understood. The expressions of Hsp90-beta and annexin A1 in lung cancer and normal lung specimens were examined, and the relationships with respect to the clinico-pathological features and patient survival in lung cancer were analyzed.

Methods

The expression levels of Hsp90-beta and annexin A1 were examined using immunohistochemistry, in-situ hybridization, and Western blot.

Results

Lung cancer tissues exhibited higher expression levels of Hsp90-beta and annexin A1 than the normal tissues (p < 0.05), and the expression levels of the markers were significantly associated with the pathological grade and lymphatic invasion of lung cancer (p < 0.05). Moreover, the upregulation of Hsp90-beta and annexin A1 correlated with decreased survival (p < 0.05).

Conclusion

The upregulation of Hsp90-beta and annexin A1 were associated with poor post-surgical survival time and lymphatic metastasis of lung cancer patients. Moreover, the high expression of the markers was an independent predictor of poor outcomes.

Translocation of HSP27 into liver cancer cell nucleus may be associated with phosphorylation and O-GlcNAc glycosylation

It has been reported that the dynamic interplay between O-GlcNAcylation and O-phosphorylation is responsible for altering the activity or localization of heat-shock proteins. The aim of this study was to determine whether dynamic interplay between O-GlcNAcylation and O-phosphorylation of HSP27 in hepatocellular cancer (HCC) cells affect its entry into the nucleus. We demonstrate that the entry of HSP27 into the nucleus correlated with its phosphorylation through transfecting HCC cells with plasmids coding for wild-type HSP27 (HSP27-WT), its non-phosphorylatable (HSP27-3A) and pseudophosphorylated (HSP27-3D) mutants, however, not all of the endogenous or exogenous nuclear HSP27 was modified by phosphorylation. We observed that HSP27 was modified with O-GlcNAc glycosylation in HCC cells and report that at conserved Ser residues of HSP27, alternative phosphorylation and O-GlcNAc modification can be predicted by the YinOYang 1.2 method. Furthermore, after P79350 or combined SB203580 and PUGNAc treatment, increased nuclear import of HSP27-WT and HSP27-3D implied that the entry of HSP27 into the nucleus was not only correlated with phosphorylation, but also with O-GlcNAc glycosylation. Collectively, O-GlcNAcylation of HSP27 in HCC cells may be a novel regulatory mode of HSP27 function, particularly for its entry into the nucleus. Crosstalk or interplay between glycosylation and phosphorylation of HSP27 could regulate its subcellular localization and biological functions in liver cancer.

Targeted therapies in breast cancer: are heart and vessels also being targeted?

The concept of 'targeted' therapies implies that such drugs only act on cells that specifically express the particular target, therefore giving rise to a low incidence of side effects. However, targeted therapies currently approved for the treatment of breast cancer have demonstrated a relatively high incidence of cardiovascular events. The anti-HER2 agents trastuzumab and lapatinib may cause left ventricular dysfunction or even congestive heart failure. Bevacizumab, an antiangiogenic drug, has been shown to increase the risk of hypertension, cardiovascular dysfunction and thromboembolic events. In addition, several anti-human epidermal growth factor receptor 2 (HER2) and antiangiogenic agents plus their combinations are currently being developed and evaluated for the treatment of breast cancer. In this review, we aim to assess the incidence of cardiac adverse events associated with targeted therapies designed to block HER2 and angiogenic pathways.

Folate receptor targeted 17-allylamino-17-demethoxygeldanamycin (17-AAG) loaded polymeric nanoparticles for breast cancer

Low water solubility and hepatotoxicity limited the clinical use of 17-allylamino-17-demethoxy geldanamycin (17-AAG), an inhibitor of heat shock protein 90 (HSP90). Folate targeted polylactide-co-glycolide-polyethylene glycol-folic acid (PLGA-PEG-FA) nanoparticles containing 17-AAG were prepared and characterized. Cellular uptake and in vitro cytotoxicity of the prepared nanoparticles were determined in MCF-7 human breast cancer cells. The particle size of 17-AAG loaded folate targeted nanoparticles was 238.67±3.52 nm, drug loading was 8.25±2.49% and about 80% of drug was released from the nanoparticles over 10 days. Cellular uptake studies showed much higher intracellular uptake of folate targeted nanoparticle as compared to nontargeted nanoparticles. Cytotoxicity study showed 2 fold increase (P<0.05, n=3) in the cytotoxicity of folate targeted nanoparticle in comparison to free drug or nontargeted nanoparticles. Due to their targeting ability, nanometer size, high drug loading and controlled release behavior, 17-AAG loaded PLGA-PEG-FA nanoparticles might be developed as a targeted delivery system for breast and other cancer treatment.

The heat shock proteins as targets for radiosensitization and chemosensitization in cancer

The heat shock proteins (HSPs) represent a class of proteins which are induced under physiologic stress to promote cell survival in the face of endogenous or exogenous injury. HSPs function predominantly as molecular chaperones, maintaining their "client" proteins in the correct conformational state in order to withstand a biologic stressor. Elevated HSP expression is also found in a range of pathologic conditions, notably malignancy. Cancer cells exploit the pro-survival phenotype endowed by HSPs to bolster their proliferative potential. Consequently, developing means of abrogating HSP expression may provide a way to render cancer cells more susceptible to radiation or chemotherapy. Here, we review the members of the HSP class and their roles in malignancy. We focus on attempts to target these proteins, particularly the small HSPs, in developing potent radiation and chemotherapy sensitizers, as well as proposed mechanisms for this sensitization effect.

Identification of HSP90 as a new GABARAPL1 (GEC1)-interacting protein

GABARAPL1 belongs to the small family of GABARAP proteins (including GABARAP, GABARAPL1 and GABARAPL2/GATE-16), one of the two subfamilies of the yeast Atg8 orthologue. GABARAPL1 is involved in the intracellular transport of receptors, via an interaction with tubulin and GABA(A) or kappa opioid receptors, and also participates in autophagy and cell proliferation. In the present study, we identify the HSP90 protein as a novel interaction partner for GABARAPL1 using GST pull-down, mass spectrometry and coimmunoprecipitation experiments. GABARAPL1 and HSP90 partially colocalize in MCF-7 breast cancer cells overexpressed Dsred-GABARAPL1 and in rat brain. Moreover, treatment of MCF-7 cells overexpressed FLAG-GABARAPL1-6HIS with the HSP90 inhibitor 17-AAG promotes the GABARAPL1 degradation, a process that is blocked by proteasome inhibitors such as MG132, bortezomib and lactacystin. Accordingly, we demonstrate that HSP90 interacts and protects GABARAPL1 from its degradation by the proteasome.

Imatinib mesylate: past successes and future challenges in the treatment of gastrointestinal stromal tumors

Just over a decade ago, gastrointestinal tumours were a poorly understood mesenchymal neoplasm unsuccessfully treated with chemotherapy. Cytotoxic therapy for advanced disease yielded response rates of 10% and median survival of just 18 months. However, the discovery of KIT and platelet derived growth factor receptor alpha (PDGFRA) mutations as oncogenic drivers of most gastrointestinal tumours, paved the way for targeted therapy. Imatinib mesylate, a tyrosine kinase inhibitor, produces a clinical benefit rate (complete response, partial response, and stable disease) of more than 80% in metastatic setting and a median survival of 57 months. Imatinib is now also approved in adult patients following resection of KIT-positive GIST. Major insights into the mechanism of action of imatinib, unique pharmacokinetics, drug resistance, and management of low grade but chronic adverse effects continue to be made.

Heat-shock protein 90 inhibition in autoimmunity to type VII collagen: evidence that nonmalignant plasma cells are not therapeutic targets

Blocking heat-shock protein 90 (Hsp90) induces death of malignant plasma cells by activation of the unfolded protein response, a signaling pathway activated by accumulation of misfolded proteins within the endoplasmic reticulum. We hypothesized that nontransformed plasma cells are also hypersensitive to Hsp90 inhibition because of their high amount of protein biosynthesis. To investigate this hypothesis, 2 different Hsp90 inhibitors, the geldanamycin derivative 17-DMAG and the nontoxic peptide derivative TCBL-145, were applied to mice with experimental epidermolysis bullosa acquisita, an autoimmune bullous disease characterized by autoantibodies against type VII collagen of the dermal-epidermal junction. Both inhibitors ameliorated clinical disease of type VII collagen-immunized mice, suppressed auto-antibody production, and reduced dermal neutrophilic infiltrate. Interestingly, total plasma cell numbers, type VII collagen-specific plasma cells, and germinal center B cells were unaffected by anti-Hsp90 treatment in vivo. However, T-cell proliferation was potently inhibited, as evidenced by the reduced response of isolated lymph node cells from immunized mice to in vitro restimulation with anti-CD3/CD28 antibody or autoantigen in the presence of Hsp90 inhibitors. Our results suggest that Hsp90 blockade has no impact on normal or autoreactive plasma cells in vivo and indentify T cells as targets of anti-Hsp90 treatment in autoimmunity to type VII collagen.

Novel therapeutic strategies in multiple myeloma: role of the heat shock protein inhibitors

Despite advances in understanding the molecular pathogenesis of multiple myeloma and promising new therapies, almost all patients eventually relapse with resistant disease. There is therefore a strong rationale for combining novel therapies that target intrinsic molecular pathways mediating multiple myeloma cell resistance. One such protein family is the heat shock proteins (HSP), especially the HSP90 family. Heat shock protein inhibitors have been identified as promising cancer treatments as, while they only inhibit a single biologic function, the chaperone-protein association, their effect is widespread as it results in the destruction of numerous client proteins. This article reviews the preclinical and clinical data, which support the testing of HSP90 inhibitors as cancer drugs and update the reader on the current status of the ongoing clinical trials of HSP90 inhibitors in multiple myeloma.

17-allyamino-17-demethoxygeldanamycin treatment results in a magnetic resonance spectroscopy-detectable elevation in choline-containing metabolites associated with increased expression of choline transporter SLC44A1 and phospholipase A2

Introduction

17-allyamino-17-demethoxygeldanamycin (17-AAG), a small molecule inhibitor of Hsp90, is currently in clinical trials in breast cancer. However, 17-AAG treatment often results in inhibition of tumor growth rather than shrinkage, making detection of response a challenge. Magnetic resonance spectroscopy (MRS) and spectroscopic imaging (MRSI) are noninvasive imaging methods than can be used to monitor metabolic biomarkers of drug-target modulation. This study set out to examine the MRS-detectable metabolic consequences of Hsp90 inhibition in a breast cancer model.

Methods

MCF-7 breast cancer cells were investigated, and MRS studies were performed both on live cells and on cell extracts. ³¹P and ¹H MRS were used to determine total cellular metabolite concentrations and ¹³C MRS was used to probe the metabolism of [1,2-¹³C]-choline. To explain the MRS metabolic findings, microarray and RT-PCR were used to analyze gene expression, and in vitro activity assays were performed to determine changes in enzymatic activity following 17-AAG treatment.

Results

Treatment of MCF-7 cells with 17-AAG for 48 hours caused a significant increase in intracellular levels of choline (to 266 ± 18% of control, P = 0.05) and phosphocholine (PC; to 181 ± 10% of control, P = 0.001) associated with an increase in expression of choline transporter SLC44A1 and an elevation in the de novo synthesis of PC. We also detected an increase in intracellular levels of glycerophosphocholine (GPC; to 176 ± 38% of control, P = 0.03) associated with an increase in PLA2 expression and activity.

Conclusions

This study determined that in the MCF-7 breast cancer model inhibition of Hsp90 by 17-AAG results in a significant MRS-detectable increase in choline, PC and GPC, which is likely due to an increase in choline transport into the cell and phospholipase activation. ¹H MRSI can be used in the clinical setting to detect levels of total choline-containing metabolite (t-Cho, composed of intracellular choline, PC and GPC). As Hsp90 inhibitors enter routine clinical use, t-Cho could thus provide an easily detectable, noninvasive metabolic biomarker of Hsp90 inhibition in breast cancer patients.