The heat-shock protein 90 inhibitor, geldanamycin, induces apoptotic cell death in Epstein-Barr virus-positive NK/T-cell lymphoma by Akt down-regulation

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

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

K64 acetylation of heat shock protein 90 suppresses nucleopolyhedrovirus replication in Bombyx mori

HSP90 is a highly conserved chaperone that facilitates the proliferation of many viruses, including silkworm (bombyx mori) nucleopolyhedrovirus (BmNPV), but the underlying regulatory mechanism was unclear. We found that suppression of HSP90 by 17-AAG, a HSP90-specific inhibitor, significantly reduced the expression of BmNPV capsid protein gp64 and viral genome replication, whereas overexpression of B. mori HSP90(BmHSP90) promoted BmNPV replication. Furthermore, in a recent study of the lysine acetylome of B. mori infected with BmNPV, we focused on the reduced viral proliferation due to changes of BmHSP90 lysine acetylation. Site-directed introduction of acetylated (K/Q) or deacetylated (K/R) mimic mutations into BmHSP90 revealed that lysine 64 (K64) acetylation activated the JAK/STAT pathway and reduced BmHSP90 ATPase activity, leading to diminished chaperone activity and ultimately inhibiting BmNPV proliferation. In this study, a single lysine 64 acetylation change of BmHSP90 was elucidated as a model of posttranslational modifications occurring in the wake of host-virus interactions, providing novel insights into potential antiviral strategies.

Mode of Action of Heat Shock Protein (HSP) Inhibitors against Viruses through Host HSP and Virus Interactions

Misfolded proteins after stress-induced denaturation can regain their functions through correct re-folding with the aid of molecular chaperones. As a molecular chaperone, heat shock proteins (HSPs) can help client proteins fold correctly. During viral infection, HSPs are involved with replication, movement, assembly, disassembly, subcellular localization, and transport of the virus via the formation of macromolecular protein complexes, such as the viral replicase complex. Recent studies have indicated that HSP inhibitors can inhibit viral replication by interfering with the interaction of the virus with the HSP. In this review, we describe the function and classification of HSPs, the transcriptional mechanism of HSPs promoted by heat shock factors (HSFs), discuss the interaction between HSPs and viruses, and the mode of action of HSP inhibitors at two aspects of inhibiting the expression of HSPs and targeting the HSPs, and elaborate their potential use as antiviral agents.

Schisandrin B Attenuates Colitis-Associated Colorectal Cancer through SIRT1 Linked SMURF2 Signaling

Colon cancer, a common type of malignant tumor, seriously endangers human health. However, due to the relatively slow progress in diagnosis and treatment, the clinical therapeutic technology of colon cancer has not been substantially improved in the past three decades. The present study was designed to investigate the effects and involved mechanisms of schisandrin B in cell growth and metastasis of colon cancer. C57BL/6 mice received AOM and dextran sulfate sodium. Mice in treatment groups were gavaged with 3.75-30 mg/kg/day of schisandrin B. Transwell chamber migration, enzyme-linked immunosorbent assay (ELISA), Western blot analysis, immunoprecipitation (IP) and immunofluorescence were conducted, and HCT116 cell line was employed in this study. Data showed that schisandrin B inhibited tumor number and tumor size in the AOD+DSS-induced colon cancer mouse model. Schisandrin B also inhibited cell proliferation and metastasis of colon cancer cells. We observed that schisandrin B induced SMURF2 protein expression and affected SIRT1 in vitro and in vivo. SMURF2 interacted with SIRT1 protein, and there was a negative correlation between SIRT1 and SMURF2 expressions in human colorectal cancer. The regulation of SMURF2 was involved in the anticancer effects of schisandrin B in both in vitro and in vivo models. In conclusion, the present study revealed that schisandrin B suppressed SIRT1 protein expression, and SIRT1 is negatively correlated with the induction of SMURF2, which inhibited cell growth and metastasis of colon cancer. Schisandrin B could be a leading compound, which will contribute to finding novel potential agents and therapeutic targets for colon cancer.

Inhibition of heat shock protein 90 suppresses Bombyx mori nucleopolyhedrovirus replication in B. mori

Heat shock protein 90 (Hsp90) plays a very important role in facilitating the replication of many viruses. Until now, little has been known about the role of Hsp90 in Bombyx mori virus infection. In this study, we explored the role of BmHsp90 in B. mori nucleopolyhedrovirus (BmNPV) replication. We found that BmHsp90 inhibition by geldanamycin (GA) significantly reduced the BmNPV titre, the protein expression level of BmNPV nucleocapsid protein 39 (VP39) and the transcript level of BmNPV genes. Silencing the hsp90 gene in BmN cells by small interfering RNA suppressed BmNPV replication whereas overexpression of hsp90 promoted the replication of BmNPV. After inhibition of Hsp90, the expression of three key genes [signal transducing activator of transcription (stat), suppressor of cytokine signalling protein 2 (socs2), socs6] involved in the Janus kinase/STAT pathway significantly changed, with up-regulation of stat and down-regulation of socs2 and socs6. In addition, the expression of two antiapoptosis genes, BmNPV inhibitor of apoptosis protein1 (BmNPV-iap1) and Bmiap2, was greatly decreased in GA-treated cells, whereas their expression was significantly increased in hsp90-overexpressed silkworm larvae. Our results indicated that inhibition of Hsp90 can suppress BmNPV proliferation in B. mori. Our findings may provide new clues to elucidate the molecular mechanisms of silkworm-virus interactions.

Heat shock proteins in infection

Heat shock proteins (HSPs) are constitutively expressed under physiological conditions in most organisms but their expression can significantly enhance in response to four types of stimuli including physical (e.g., radiation or heat shock), chemical and microbial (e.g., pathogenic bacteria, viruses, parasites and fungi) stimuli, and also dietary. These proteins were identified for their role in protecting cells from high temperature and other forms of stress. HSPs control physiological activities or virulence through interaction with various regulators of cellular signaling pathways. Several roles were determined for HSPs in the immune system including intracellular roles (e.g., antigen presentation and expression of innate receptors) as well as extracellular roles (e.g., tumor immunosurveillance and autoimmunity). It was observed that exogenously administered HSPs induced various immune responses in immunotherapy of cancer, infectious diseases, and autoimmunity. Moreover, virus interaction with HSPs as molecular chaperones showed important roles in regulating viral infections including cell entry and nuclear import, viral replication and gene expression, folding/assembly of viral protein, apoptosis regulation, and host immunity. Viruses could regulate host HSPs at different levels such as transcription, translation, post-translational modification and cellular localization. In this review, we attempt to overview the roles of HSPs in a variety of infectious diseases.

The HSP90/Akt pathway may mediate artemether-induced apoptosis of Cal27 cells

Tongue squamous cell carcinoma is the most common malignant tumor in oral and maxillofacial regions. Recent research has found that artemether can inhibit growth and induce apoptosis of cancer cells, although the mechanism is not clear. The present study aimed to explore the correlation between the HSP90/Akt pathway and artemether‐induced apoptosis of Cal27 cells. A cell counting kit‐8 and flow cytometry were used to detect the proliferation and apoptosis of Cal27 cells, respectively, mRNA expression was examined by quantitative RT‐PCR, and protein expression was detected by western blotting. Our data revealed that artemether can inhibit growth and induce apoptosis of Cal27 cells. As the artemether concentration was increased, we observed downregulation of the expression of HSP90, p‐Akt and p‐mTOR in Cal27 cells, whereas the expression of Akt was not significantly changed. We also observed a time‐dependent decrease in the expression of HSP90, p‐Akt and p‐mTOR during exposure to 0.1 mg·mL⁻¹ artemether. In conclusion, the HSP90/Akt pathway may be involved in artemether‐induced apoptosis of Cal27 cells.

[PRDM1 expression and its relationship with PI3K/AKT pathway activation in extranodal NK/T cell lymphoma-nasal type]

目的

探讨抑癌基因PRDM1在结外NK/T细胞淋巴瘤-鼻型（EN-NK/T-NT）中的表达及其与PI3K/AKT通路活化的关系。

方法

以10例EN-NK/T-NT患者病理组织标本和PRDM1阳性细胞系YT细胞、PRDM1缺失细胞系NKL、NK92细胞为研究对象，采用免疫细胞化学和Western blot法检测PRDM1、p-AKT的表达，采用NanoString基因表达谱技术检测PI3K/AKT通路在正常鼻黏膜、PRDM1阴性和阳性EN-NK/T-NT组织中的激活情况，采用MTS法检测YT、NKL和NK92细胞增殖活性，采用流式细胞术检测细胞周期和细胞凋亡。

结果

①NanoString基因表达谱分析结果显示PRDM1阳性组PI3K/AKT信号通路IL-7、BRCA1、ITGA8、IL2RB、FASLG、CDK2、COL27A1、CSF3R、KITLG、IL-6的表达明显高于对照组，差异均有统计学意义（P值均<0.05）。②免疫细胞化学和Western blot法检测结果显示p-AKT在YT细胞系中高表达，而在NK92和NKL细胞中低表达或不表达。③Western blot法检测结果显示，PI3K/AKT通路抑制剂LY294002作用24 h后YT细胞PRDM1和PTEN的表达水平升高，且呈剂量依赖性。④LY294002（20 µmol/L）作用48 h后，与对照组比较，YT细胞增殖率较对照组明显降低（100.00%对58.18%，t=−12.770，P=0.006），G₁期细胞比例明显增高（30.05%对76.93%，t=11.570，P<0.001），差异均有统计学意义；但NKL细胞与对照组比较细胞增殖和细胞周期的差异均无统计学意义（P值均>0.05）。

结论

EN-NK/T-NT中PI3K/AKT通路活化与PRDM1阳性表达相关，抑制PI3K/AKT通路有望成为PRDM1阳性EN-NK/T-NT的治疗手段。

Hsp90ab1 stabilizes LRP5 to promote epithelial-mesenchymal transition via activating of AKT and Wnt/β-catenin signaling pathways in gastric cancer progression

Hsp90ab1 is upregulated in numerous solid tumors, which is thought to induce the angiogenesis and promote cancer metastasis. However, it's actions in gastric cancer (GC) has not been exhibited. In this study, Hsp90ab1 was demonstrated to be overexpressed and correlated with the poor prognosis, proliferation and invasion of GC. Ectopic expression of Hsp90ab1 promoted the proliferation and metastasis of GC cells both in vitro in cell line models of GC and in vivo using two different xenograft mouse models, while opposite effects were observed in Hsp90ab1 silenced cells. Moreover, the underlining molecular mechanism was explored by the co-immunoprecipitation, immunofluorescence, GST pull-down and in vitro ubiquitination assay. Namely, Hsp90ab1 exerted these functions via the interaction of LRP5 and inhibited ubiquitin-mediated degradation of LRP5, an indispensable coreceptor of the Wnt/β-catenin signaling pathway. In addition, the crosstalk between Hsp90ab1 and LRP5 contributed to the upregulation of multiple mesenchymal markers, which are also targets of Wnt/β-catenin. Collectively, this study uncovers the details of the Hsp90ab1-LRP5 axis, providing novel insights into the role and mechanism of invasion and metastasis in GC.

HSP90: a promising broad-spectrum antiviral drug target

The emergence of antiviral drug-resistant mutants is the most important issue in current antiviral therapy. As obligate parasites, viruses require host factors for efficient replication. An ideal therapeutic target to prevent drug-resistance development is represented by host factors that are crucial for the viral life cycle. Recent studies have indicated that heat shock protein 90 (HSP90) is a crucial host factor that is required by many viruses for multiple phases of their life cycle including viral entry, nuclear import, transcription, and replication. In this review, we summarize the most recent advances regarding HSP90 function, mechanisms of action, and molecular pathways that are associated with viral infection, and provide a comprehensive understanding of the role of HSP90 in the immune response and exosome-mediated viral transmission. In addition, several HSP90 inhibitors have entered clinical trials for specific cancers that are associated with viral infection, which further implies a crucial role for HSP90 in the malignant transformation of virus-infected cells; as such, HSP90 inhibitors exhibit excellent therapeutic potential. Finally, we describe the challenge of developing HSP90 inhibitors as anti-viral drugs.

Heat shock protein 90/Akt pathway participates in the cardioprotective effect of exogenous hydrogen sulfide against high glucose-induced injury to H9c2 cells

It has been reported that exogenous hydrogen sulfide (H2S) protects against high glucose (HG)-induced cardiac injury and has a modulatory effect on heat shock protein (HSP) and Akt, which play a cardioprotective role. In this study, we examined whether the HSP90/Akt pathway contributes to the protective effects of exogenous H2S against HG-induced injury to H9c2 cardiac cells. Our results revealed that the exposure of H9c2 cardiac cells to 35 mM glucose (HG) for 1 to 24 h decreased the expression of HSP90 and markedly reduced the expression level of phosphorylated (p)-Akt in a time-dependent manner. Co-exposure of the cells to HG and geldanamycin (GA; an inhibitor of HSP90) aggravated the inhibition of the p-Akt expression level by HG. Of note, treatment of the cells with 400 µM NaHS (a donor of H2S) for 30 min prior to exposure to HG significantly attenuated the HG-induced decrease in the expression levels of both HSP90 and p-Akt, along with inhibition of HG-induced cell injury, as indicated by the increase in cell viability and superoxide dismutase (SOD) activity, and by a decrease in the number of apoptotic cells, reactive oxygen species (ROS) generation, as well as by the decreased dissipation of mitochondrial membrance potential (MMP). Importantly, treatment of the cells with GA or LY294002 (an inhibitor of Akt) prior to exposure to NaHS and HG considerably blocked the cardioprotective effects of NaHS against the HG-induced injury mentioned above. On the whole, the findings of this study demonstrate that the inhibition of the HSP90/Akt pathway may be an important mechanism responsible for HG-induced cardiomyocyte injury. We also provide novel evidence that exogenous H2S protects H9c2 cells against HG-induced injury by activating the HSP90/Akt pathway.

Ganetespib, an HSP90 inhibitor, kills Epstein-Barr virus (EBV)-infected B and T cells and reduces the percentage of EBV-infected cells in the blood

HSP90 inhibitors have been shown to kill Epstein-Barr virus (EBV)-infected cells by reducing the level of EBV EBNA-1 and/or LMP1. We treated virus-infected cells with ganetespib, an HSP90 inhibitor currently being evaluated in multiple clinical trials for cancer and found that the drug killed EBV-positive B and T cells and reduced the level of both EBV EBNA-1 and LMP1. Treatment of cells with ganetespib also reduced the level of pAkt. Ganetespib delayed the onset of EBV-positive lymphomas and prolonged survival in SCID mice inoculated with one EBV-transformed B-cell line, but not another B-cell line. The former cell line showed lower levels of EBNA-1 after treatment with ganetespib in vitro. Treatment of a patient with T-cell chronic active EBV with ganetespib reduced the percentage of EBV-positive cells in the peripheral blood. These data indicate that HSP90 inhibitors may have a role in the therapy of certain EBV-associated diseases.

Macrophage inflammatory protein 1 alpha (MIP-1α) may be associated with poor outcome in patients with extranodal NK/T-cell lymphoma

The macrophage inflammatory protein 1α (MIP-1α) is anticipated to have a role in extranodal natural killer (NK)/T-cell lymphoma (ENKTL) because the expression of MIP-1α is related to Epstein-Barr virus (EBV) latency in EBV-related non-Hodgkin lymphoma cells. Thus, we measured the serum level of MIP-1α in 69 patients with ENKTL using frozen serum samples that were archived at diagnosis. As serum level of MIP-1α was not detectable in 19 patients (range: 0-24.37 pg/mL), patients were dichotomized into positive (n = 50) and negative (n = 19) MIP-1α groups according to the presence of detectable level of MIP-1α in serum. MIP-1α-positive group showed a significantly poor overall survival (OS) in comparison with the MIP-1α-negative group (p = 0.004). In the subgroup analysis, the positivity of MIP-1α was significantly associated with OS in patients with stage IIIE/IV and a detectable level of EBV DNA (p = 0.002 and 0.032, respectively). Multivariate analysis also showed that the positivity of MIP-1α was independently associated with worse OS together with bone marrow involvement (p = 0.002). An in vitro study with patient-derived ENKTL tumour cells showed the expression of CCR1 and CCR5 on the surface of tumour cells (28% and 14%, respectively) , and the addition of MIP-1α to the culture media of tumour cells increased cell growth supporting the negative impact of MIP-1α on the prognosis of ENKTL patients. In conclusion, serum levels of MIP-1α could predict survival outcomes in patients with ENKTL. Therefore, MIP-1α should be considered for prognostication and a potential therapeutic target. Copyright © 2016 John Wiley & Sons, Ltd.

The serum CXCL13 level is associated with the Glasgow Prognostic Score in extranodal NK/T-cell lymphoma patients

Background

The Glasgow Prognostic Score (GPS) measures inflammation and proves its prognostic value in patients with extranodal natural killer (NK)/T-cell lymphoma (ENKTL) which is commonly combined with inflammatory lesion. Given inflammatory chemokines play an important role in tumor progression, we hypothesized that chemokines might influence ENKTL aggressiveness through interaction with their receptors in the tumor tissue.

Methods

We measured the serum levels of C-X-C motif ligand 13 (CXCL13) in 69 patients with ENKTL who received non-anthracycline-based chemotherapy and/or concurrent chemoradiotherapy because CXCL13 is thought to have a pro-tumor effect through interaction with its receptor, the C-X-C chemokine receptor 5 (CXCR5). We analyzed the association of serum CXCL13 with the GPS, and their prognostic relevance. The levels of CXCL13 were measured using a multiplex chemokine assay on archived frozen serum samples.

Results

Patients were categorized into high and low CXCL13 groups if they had CXCL13 levels above or below the median value of 29.1 pg/mL, respectively. The high CXCL13 group and grouping by the GPS showed a significant association with poor progression-free survival. The elevated serum levels of CXCL13 were also significantly associated with a high score of the GPS. High CXCL13 levels and GPS were significantly associated with high tumor burden predicting poor prognosis including stages III/IV, extranasal presentation, bone marrow invasion, and presence of Epstein-Barr virus (EBV) DNA in blood. Furthermore, serum CXCL13 and GPS discriminated patients at risk of treatment failure among patients with low tumor burden (stage I/II) and non-detectable EBV DNA.

Conclusions

Serum levels of CXCL13 were associated with the prognostic value of GPS. Grouping by the serum CXCL13 might predict survival outcomes in patients with ENKTL, suggesting that it is a potential therapeutic target.

Differential proteomic analysis of endemic and sporadic Epstein-Barr virus-positive and negative Burkitt lymphoma

BACKGROUND

Burkitt lymphoma (BL) is the most common non-Hodgkin lymphoma in children worldwide and the most common paediatric malignancy in sub-Saharan Africa. The endemic (eBL) and sporadic (sBL) variants have distinct epidemiologic and virologic characteristics. Although gene expression studies have defined the transcriptional profiles of both, their proteomic signatures have not been studied.

METHODS

We compared the proteomic expression profiles using differential mass spectrometry-based isotope tag for relative and absolute quantitation (iTRAQ) analysis of a cell line representing Epstein-Barr virus (EBV)+ eBL, EBV+ and EBV- sBL, and EBV+/- normal B cells from healthy donors.

RESULTS

In total, there were 144 differentially expressed proteins with a statistically significant false discovery rate (FDR) of ⩽0.2. Results revealed over-expression of specific proteins with well-established links to lymphomagenesis such as TUBB2C (FDR 0.05), UCHL1 (FDR 0.05) and HSP90AB1 (FDR 0.1). Distinct characteristics based upon the epidemiologic and virologic subtypes of BL were also identified. In sBL, PCNA (FDR 0.05) and SLC3A2 (FDR 0.1) were significantly over-expressed. In eBL, C1QBP (FDR 0.1) and ENO1 (FDR 0.25) were significantly over-expressed. Comparison of EBV+ to EBV- BL cell lines and B cells revealed significant over-expression of DDX3X (FDR 0.1). Proteins were validated using Western blot analysis.

CONCLUSION

Our results suggest unique signal transduction pathways associated with EBV infection and epidemiological subtype of BL that may contribute to lymphomagenesis. These proteomic findings provide potential diagnostic, prognostic and therapeutic links to BL.

Targeting the Hsp90-associated viral oncoproteome in gammaherpesvirus-associated malignancies

PU-H71 is a purine-scaffold Hsp90 inhibitor that, in contrast to other Hsp90 inhibitors, displays unique selectivity for binding the fraction of Hsp90 that is preferentially associated with oncogenic client proteins and enriched in tumor cells (teHsp90). This property allows PU-H71 to potently suppress teHsp90 without inducing toxicity in normal cells. We found that lymphoma cells infected by Epstein-Barr virus or Kaposi sarcoma-associated herpes virus (KSHV) are exquisitely sensitive to this compound. Using PU-H71 affinity capture and proteomics, an unbiased approach to reveal oncogenic networks, we identified the teHsp90 interactome in KSHV(+) primary effusion lymphoma cells. Viral and cellular proteins were identified, including many involved in nuclear factor (NF)-κB signaling, apoptosis, and autophagy. KSHV vFLIP is a viral oncoprotein homologous to cFLIPs, with NF-κB-activating and antiapoptotic activities. We show that teHsp90 binds vFLIP but not cFLIPs. Treatment with PU-H71 induced degradation of vFLIP and IKKγ, NF-κB downregulation, apoptosis and autophagy in vitro, and more importantly, tumor responses in mice. Analysis of the interactome revealed apoptosis as a central pathway; therefore, we tested a BCL2 family inhibitor in primary effusion lymphoma cells. We found strong activity and synergy with PU-H71. Our findings demonstrate PU-H71 affinity capture identifies actionable networks that may help design rational combinations of effective therapies.

Heat shock protein-90-beta facilitates enterovirus 71 viral particles assembly

Molecular chaperones are reported to be crucial for virus propagation, but are not yet addressed in Human Enterovirus 71 (EV71). Here we describe the specific association of heat shock protein-90-beta (Hsp90β), but not alpha form (Hsp90α), with EV71 viral particles by the co-purification with virions using sucrose density gradient ultracentrifugation, and by the colocalization with viral particles, as assessed by immunogold electron microscopy. The reduction of the Hsp90β protein using RNA interference decreased the correct assembly of viral particles, without affecting EV71 replication levels. Tracking ectopically expressed Hsp90β protein associated with EV71 virions revealed that Hsp90β protein was transmitted to new host cells through its direct association with infectious viral particles. Our findings suggest a new antiviral strategy in which extracellular Hsp90β protein is targeted to decrease the infectivity of EV71 and other enteroviruses, without affecting the broader functions of this constitutively expressed molecular chaperone.

Heat shock protein 90 inhibitors repress latent membrane protein 1 (LMP1) expression and proliferation of Epstein-Barr virus-positive natural killer cell lymphoma

Epstein-Barr virus (EBV) LMP1 is a major oncoprotein expressed in latent infection. It functions as a TNFR family member and constitutively activates cellular signals, such as NFκB, MAPK, JAK/STAT and AKT. We here screened small molecule inhibitors and isolated HSP90 inhibitors, Radicicol and 17-AAG, as candidates that suppress LMP1 expression and cell proliferation not only in EBV-positive SNK6 Natural Killer (NK) cell lymphoma cells, but also in B and T cells. Tumor formation in immuno-defficient NOD/Shi-scid/IL-2Rγ^null (NOG) mice was also retarded. These results suggest that HSP90 inhibitors can be alternative treatments for patients with EBV-positive malignancies.

Nuclear transport of Epstein-Barr virus DNA polymerase is dependent on the BMRF1 polymerase processivity factor and molecular chaperone Hsp90

Epstein-Barr virus (EBV) replication proteins are transported into the nucleus to synthesize viral genomes. We here report molecular mechanisms for nuclear transport of EBV DNA polymerase. The EBV DNA polymerase catalytic subunit BALF5 was found to accumulate in the cytoplasm when expressed alone, while the EBV DNA polymerase processivity factor BMRF1 moved into the nucleus by itself. Coexpression of both proteins, however, resulted in efficient nuclear transport of BALF5. Deletion of the nuclear localization signal of BMRF1 diminished the proteins' nuclear transport, although both proteins can still interact. These results suggest that BALF5 interacts with BMRF1 to effect transport into the nucleus. Interestingly, we found that Hsp90 inhibitors or knockdown of Hsp90β with short hairpin RNA prevented the BALF5 nuclear transport, even in the presence of BMRF1, both in transfection assays and in the context of lytic replication. Immunoprecipitation analyses suggested that the molecular chaperone Hsp90 interacts with BALF5. Treatment with Hsp90 inhibitors blocked viral DNA replication almost completely during lytic infection, and knockdown of Hsp90β reduced viral genome synthesis. Collectively, we speculate that Hsp90 interacts with BALF5 in the cytoplasm to assist complex formation with BMRF1, leading to nuclear transport. Hsp90 inhibitors may be useful for therapy for EBV-associated diseases in the future.

The role of the Hsp90/Akt pathway in myocardial calpain-induced caspase-3 activation and apoptosis during sepsis

Background

Recent studies have demonstrated that myocardial calpain triggers caspase-3 activation and myocardial apoptosis in models of sepsis, whereas the inhibition of calpain activity down-regulates myocardial caspase-3 activation and apoptosis. However, the mechanism underlying this pathological process is unclear. Therefore, in this study, our aim was to explore whether the Hsp90/Akt signaling pathway plays a role in the induction of myocardial calpain activity, caspase-3 activation and apoptosis in the septic mice.

Methods

Adult male C57 mice were injected with lipopolysaccharide (LPS, 4 mg/kg, i.p.) to induce sepsis. Next, myocardial caspase-3 activity and the levels of Hsp90/p-Akt (phospho-Akt) proteins were detected, and apoptotic cells were assessed by performing the TUNEL assay.

Results

In the septic mice, there was an increase in myocardial calpain and caspase-3 activity in addition to an increase in the number of apoptotic cells; however, there was a time-dependent decrease in myocardial Hsp90/p-Akt protein levels. The administration of calpain inhibitors (calpain inhibitor-Ш or PD150606) prevented the LPS-induced degradation of myocardial Hsp90/p-Akt protein and its expression in cardiomyocytes in addition to inhibiting myocardial caspase-3 activation and apoptosis. The inhibition of Hsp90 by pretreatment with 17-AAG induced p-Akt degradation, and the inhibition of Akt activity by pretreatment with wortmannin resulted in caspase-3 activation in wildtype C57 murine heart tissues.

Conclusions

Myocardial calpain induces myocardial caspase-3 activation and apoptosis in septic mice via the activation of the Hsp90/Akt pathway.

Roles of the PI3K/Akt pathway in Epstein-Barr virus-induced cancers and therapeutic implications

Viruses have been shown to be responsible for 10%-15% of cancer cases. Epstein-Barr virus (EBV) is the first virus to be associated with human malignancies. EBV can cause many cancers, including Burkett's lymphoma, Hodgkin's lymphoma, post-transplant lymphoproliferative disorders, nasopharyngeal carcinoma and gastric cancer. Evidence shows that phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) plays a key role in EBV-induced malignancies. The main EBV oncoproteins latent membrane proteins (LMP) 1 and LMP2A can activate the PI3K/Akt pathway, which, in turn, affects cell survival, apoptosis, proliferation and genomic instability via its downstream target proteins to cause cancer. It has also been demonstrated that the activation of the PI3K/Akt pathway can result in drug resistance to chemotherapy. Thus, the inhibition of this pathway can increase the therapeutic efficacy of EBV-associated cancers. For example, PI3K inhibitor Ly294002 has been shown to increase the effect of 5-fluorouracil in an EBV-associated gastric cancer cell line. At present, dual inhibitors of PI3K and its downstream target mammalian target of rapamycin have been used in clinical trials and may be included in treatment regimens for EBV-associated cancers.

Heat shock protein 90 inhibition by 17-DMAG lessens disease in the MRL/lpr mouse model of systemic lupus erythematosus

Elevated expression of heat shock protein 90 (HSP90) has been found in kidneys and serum of systemic lupus erythematosus (SLE) patients and MRL/Mp-Fas(lpr)/Fas(lpr) (MRL/lpr) autoimmune mice. We investigated if inhibition of HSP90 would reduce disease in MRL/lpr mice. In vitro, pretreatment of mesangial cells with HSP90 inhibitor Geldanamycin prior to immune-stimulation showed reduced expression of IL-6, IL-12 and NO. In vivo, we found HSP90 expression was elevated in MRL/lpr kidneys when compared to C57BL/6 mice and MRL/lpr mice treated with HSP90 inhibitor 17-DMAG. MRL/lpr mice treated with 17-DMAG showed decreased proteinuria and reduced serum anti-dsDNA antibody production. Glomerulonephritis and glomerular IgG and C3 were not significantly affected by administration of 17-DMAG in MRL/lpr. 17-DMAG increased CD8(+) T cells, reduced double-negative T cells, decreased the CD4/CD8 ratio and reduced follicular B cells. These studies suggest that HSP90 may play a role in regulating T-cell differentiation and activation and that HSP90 inhibition may reduce inflammation in lupus.

Broad action of Hsp90 as a host chaperone required for viral replication

Viruses are intracellular pathogens responsible for a vast number of human diseases. Due to their small genome size, viruses rely primarily on the biosynthetic apparatus of the host for their replication. Recent work has shown that the molecular chaperone Hsp90 is nearly universally required for viral protein homeostasis. As observed for many endogenous cellular proteins, numerous different viral proteins have been shown to require Hsp90 for their folding, assembly, and maturation. Importantly, the unique characteristics of viral replication cause viruses to be hypersensitive to Hsp90 inhibition, thus providing a novel therapeutic avenue for the development of broad-spectrum antiviral drugs. The major developments in this emerging field are hereby discussed. This article is part of a Special Issue entitled: Heat Shock Protein 90 (HSP90).

Targeting PI3K/Akt/HSP90 signaling sensitizes gastric cancer cells to deoxycholate-induced apoptosis

BACKGROUND

The heat shock protein 90 (HSP90) plays a crucial role in the stability of several proteins that are essential for cell survival and for malignant transformation. The binding of HSP90 with pro-survival kinase Akt prevents proteosomal degradation of Akt and contributes to the functional stabilization of PI3K/Akt signaling and cell survival. Akt kinase and HSP90 are therefore highly over-expressed in a large panel of cancer cell lines and are present in multi-chaperoning complexes. In this paper, we investigated whether targeting both Akt and HSP90 would inhibit the survival pathway in AGS cells (human gastric mucosal cells), and how Akt/HSP90 inhibition modulates the deoxycholate (DC)-induced apoptosis.

METHODS

AGS cells in the presence of Akt inhibitors (LY294002 and wortmannin), or HSP90 inhibitor (geldanamycin, GA) for 30 min or 18 h, respectively, were treated with DC (50 µM). Activation of PI3K/Akt signaling was evaluated by measuring the Akt and PTEN phosphorylation. HSP90, caspase-3 and caspase-9 were detected in whole lysates by Western blot analysis. AGS cells, transiently transfected with Akt siRNA, were treated with DC, and apoptosis was measured by caspase-3 activation. Apoptotic-positive cells were counted according to changes of cell morphology by Hoechst staining and fluorescence microscopy.

RESULTS

The intrinsic level of phospho-Akt (pAkt; active form), phospho-PTEN (pPTEN; inactive enzyme) and HSP90 were highly expressed in AGS cells indicating the active PI3K/Akt/HSP90 signaling. Although, deoxycholate at low concentration (50 µM) slightly inhibited the expression of pAkt and cleaved HSP90 to 55 KDa fragment, no significant effect on apoptosis induction, up to 4 h (as assessed by caspase-3 activation) was observed. The higher concentrations of DC (100 µM-300 µM) resulted in progressive inhibition of pAkt, activation of PTEN, and specific cleavage of HSP90 to approximately 45 KDa fragments with significant induction of apoptosis. Although DC (50 µM) had no profound effect on Akt/HSP90 and did not induce apoptosis, it became an inducer of apoptosis when cells were pretreated with LY294002, wortmannin, or geldanamycin. Consistent with these findings, significant activation of apoptosis in response to DC (50 µM) was observed in cells with depleted Akt protein.

CONCLUSIONS

These results demonstrate that down-regulation of PI3K/Akt pathway with specific cleavage of HSP90 to 45 KDa modulates the pro-apoptotic effects of DC in gastric cells. They further indicate the importance of stable Akt/HSP90 complex in regulation of survival/death responses.

Role of Hsp90 in CpG ODN mediated immunostimulation in avian macrophages

In mammals, CpG mediated immune activation is initiated through toll-like receptor (TLR) 9 and Hsp90 via activation of MAPK/ERK and PI3K/AKT pathways. However, in the absence of TLR9 ortholog in chicken genome, the role of Hsp90 and kinase (MAPK/ERK and PI3K/AKT) pathways in initiating CpG ODN(2007) induced immune activation in chicken is not clear. Using electrophoretic mobility shift assay (EMSA) and selective inhibitors of signal transduction pathways, we determined the role of these pathways in the production of Th1 cytokines/chemokines and nitric oxide (NO) in CpG ODN(2007) treated avian macrophage cells. Hsp90alpha but not Hsp90beta is bound to CpG ODN(2007). Inhibition of Hsp90 with geldanamycin resulted in the inactivation of MAPK/ERK and PI3K/AKT pathways leading to significantly reduced levels of IFN-gamma, IL-6 and NO mRNAs in CpG ODN(2007) stimulated cells. Moreover, inhibition of ERK1/2 and PI3/AKT kinase pathways with PD985009 and LY294002, respectively, suppresses the phosphorylation of ERK2 and AKT leading to the production of decreased amounts of IFN-gamma, IL-6 and NO mRNAs in CpG ODN(2007) stimulated cells. Our results demonstrate that binding of CpG ODN(2007) to Hsp90 induces activation of ERK2 and AKT phosphorylation leading to the production of high levels of IFN-gamma, IL-6, MIP-3alpha and nitric oxide (NO). In contrast to mammals, our results suggest that Hsp90alpha but not Hsp90beta binds with the CpG ODN(2007) and may play a major role in CpG ODN(2007) induced immunoactivation in avian macrophage cells. To our knowledge, this is the first report evaluating the involvement of Hsp90 and kinase (MAPK/ERK and PI3K/AKT) pathways in CpG mediated immunostimulation in avian macrophage cells.

Macrocyclic inhibitors of hsp90

Heat shock proteins (HSP) are a family of highly conserved proteins, whose expression increases in response to stresses that may threaten cell survival. Over the past decade, heat shock protein 90 (Hsp90) has emerged as a potential therapeutic target for cancer as it plays a vital role in normal cell maturation and acts as a molecular chaperone for proper folding, assembly, and stabilization of many oncogenic proteins. To date, a majority of Hsp90 inhibitors that have been discovered are macrocycles. The relatively rigid conformation provided by the macrocyclic scaffold allows for a selective interaction with a biological target such as Hsp90. This review highlights the discovery and development of nine macrocycles that inhibit the function of Hsp90, detailing their potency and the client proteins affected by Hsp90 inhibition.

Extranodal NK / T-cell lymphoma, nasal type: new staging system and treatment strategies

Extranodal NK/T-cell lymphoma (NTCL) is characterized by clinical heterogeneity based on clinical prognostic factors and survival outcome. NTCL subsets are classified as upper aerodigestive tract (UAT) NTCL or non-UAT NTCL; non-UAT has pathologic similarity to UAT-NTCL but is a clinically distinct subtype. Due to the clinical heterogeneity of NTCL, optimal treatment modalities and prognostic factors have been difficult to determine. Ann Arbor staging for lymphomas and the International Prognostic Index (IPI) have been used to predict prognosis for UAT-NTCL; however, local tumor invasiveness (bony invasion or perforation or invasion of the overlying skin) is the most significant factor for poor outcomes in localized UAT-NTCL. Thus, a new staging system is proposed: limited disease (stage I/II UAT-NTCL without local tumor invasiveness) and extensive disease (stage I/II with local invasiveness or stage III/IV disease of UAT NTCL, and non-UAT NTCL) based on treatment outcomes. NTCL is resistant to anthracycline-based chemotherapy, whereas non-anthracycline combination chemotherapy (such as ifosfamide, methotrexate, etoposide, and prednisolone) has an activity against NTCL as either a front-line or as a second-line treatment. The effectiveness of radiotherapy is evident in limited disease, but questionable in extensive disease.

Targeted therapy in T-cell malignancies: dysregulation of the cellular signaling pathways

T-cell malignancies, mainly known as T-cell acute lymphoblastic leukemia (T-ALL) and T-cell non-Hodgkin's lymphoma (T-NHL), are aggressive tumors. Although the clinical outcome of the patients has improved dramatically with combination chemotherapy, significant challenges remain, including understanding of the factors that contribute to the malignant behavior of these tumor cells and developing subsequently optimal targeted therapy. Aberrant cell signal transduction is generally involved in tumor progression and drug resistance. This review describes the pathogenetic role of multiple cellular signaling pathways in T-cell malignancies and the potential therapeutic strategies based on the modulation of these key signaling networks.

Heat shock protein 90 inhibitor induces apoptosis and attenuates activation of hepatic stellate cells

Activated hepatic stellate cells (HSCs) are major participants in hepatic fibrosis; thus, the induction of HSC apoptosis has been proposed as an antifibrotic treatment strategy. Heat shock protein (Hsp) 90 is a molecular chaperone that stabilizes major signal transduction proteins, and its inhibitors have antitumor activity. In this study, the susceptibility of HSCs to an Hsp90 inhibitor was evaluated. LX-2 cells, an immortalized human HSC line, 17-(allylamino)-17-demethoxygeldanamycin (17AAG), an Hsp90 inhibitor, and monensin, an acidic sphingomyelinase inhibitor, were used in this study. Cellular apoptosis was quantified by 4',6-diamidino-2-phenylindole dihydrochloride staining, and signaling cascades were explored using immunoblotting and immunoprecipitation techniques. Nuclear factor (NF) kappaB activities were evaluated by immunofluorescent microscopy and enzyme-linked immunosorbent assay. Collagen alpha1 and alpha-smooth muscle actin expressions were determined by real-time reverse transcription-polymerase chain reaction and immunoblotting, respectively. It was found that 17AAG induced HSC apoptosis and that caspase 8 cleavage preceded the downstream activation of apoptotic signaling cascades. Furthermore, this caspase 8 activation was dependent on ceramide generation by acidic sphingomyelinase. In addition, 17AAG prevented NFkappaB nuclear translocation and activation, specifically by inducing complex formation between NFkappaB and the glucocorticoid receptor. In accordance, NFkappaB-dependent cellular FLICE-like inhibitory protein expression level was found to be reduced by 17AAG. Finally, 17AAG down-regulated collagen alpha1 and alpha-smooth muscle actin expression levels in HSCs before inducing apoptosis. These results demonstrate that the Hsp90 inhibitor induces HSC apoptosis via a sphingomyelinase- and NFkappaB-dependent mechanism. Because this inhibitor also reduces HSC activation before apoptosis, Hsp90 inhibitor treatment might be therapeutically useful as an antifibrotic strategy in a variety of liver diseases.

The co-chaperone BAG3 regulates Herpes Simplex Virus replication

Viruses as obligate intracellular parasites use host cell proteins to ensure efficient replication and spread. Cellular proteins are required for several stages of a virus life cycle. Here, we identify BAG3, a co-chaperone, as a regulator of herpes virus immediate early gene expression. We report that a herpes simplex virus lacking the gene encoding a potent transcriptional activator, ICP0, is compromised for replication in cells silenced for BAG3 in a multiplicity of infection-dependent manner. We also show a requirement for BAG3 to augment virus gene expression and demonstrate that the co-chaperone acts independently of promyelocytic leukemia to increase herpes simplex virus replication.

The heat shock protein 90 inhibitor IPI-504 induces apoptosis of AKT-dependent diffuse large B-cell lymphomas

Heat shock protein 90 (HSP90) is a molecular chaperone that stabilizes critical client proteins in multiple cancers. Gene expression profiling was utilized to characterize HSP90 isoform expression in primary human diffuse large B-cell lymphomas (DLBCLs). HSP90 alpha and beta isoforms were differentially expressed in subsets of tumours defined by their transcriptional profiles. Thereafter, we assessed the activity of the HSP90 inhibitor, IPI-504, in an extensive panel of DLBCL cell lines. IPI-504, which interacts with the conserved ATP-binding site in both HSP90 isoforms, inhibited proliferation and induced apoptosis in the majority of DLBCL cell lines at low micromolar concentrations. IPI-504-sensitive cell lines expressed high levels of the HSP90 client protein, pAKT, and exhibited dose-dependent decreases in pAKT levels following IPI-504 treatment and significantly reduced proliferation following AKT RNAi. Furthermore, the combination of low-dose (<1 micromol/l) IPI-504 and the AKT/Pi3K pathway inhibitor, LY24009, was synergistic in IPI-504-sensitive DLBCL cell lines. Low-dose IPI-504 was also synergistic with the chemotherapeutic agent, doxorubicin. The HSP90 inhibitor IPI-504 warrants further investigation in DLBCL alone and in combination with identified client protein inhibitors and active chemotherapeutic agents.