HSP90, which is the biomarker of cell stress and endogenous protective protein, functions as a molecular chaperone. Many client proteins of HSP90, including EGFR, Met, Raf-1, IKK and p53, play important roles in the occurrence and development of tumor. Binding of HSP90 inhibitors triggers the deactivation of HSP90, resulting in client protein degradation, and hence inhibits the tumor growth by blocking multiple targets involved in signaling of tumor proliferation. This review summarizes recent development of small molecule inhibitors bound to N-terminal of HSP90.
Antineoplastic Agents ; chemistry ; HSP90 Heat-Shock Proteins ; antagonists & inhibitors ; Humans ; Neoplasms ; Signal Transduction

Heat shock proteins (HSPs) form the most ancient defense system in all living organisms. These proteins act as molecular chaperones by helping the refolding of misfolded proteins and assisting their elimination if they become irreversibly damaged. HSPs interact with a number of cellular systems and form efficient cytoprotective mechanisms. HSPs allow cells to adapt to gradual changes in their environment and to survive in otherwise lethal conditions. The events of cell stress and cell death are linked, and HSPs induced in response to stress appear to function at key regulatory points in the control of apoptosis. HSPs include antiapoptotic and proapoptotic proteins that interact with a variety of cellular proteins. Their expression levels can determine the fate of the cell in response to death stimulus. On the other hand, HSPs are overexpressed in tumor cells, and the inhibition of HSP90 has recently been regarded as a very promising tool to combat various cancers. HSPs can be secreted to circulatory system from a variety of cell types in response to stress. The secreted exogenous proteins act as cytokines and have potential modulatory functions in immune system. Cell surface-bound HSP70 can render tumor cell more sensitive to natural killer cell-mediated cytolytic attack. Therefore, modulator of chaperone activities is becoming a new target of drug development, such as in apoptosis and tumor immunity fields.
Animals ; Apoptosis ; drug effects ; Cytoprotection ; drug effects ; Drug Delivery Systems ; economics ; methods ; trends ; Drug Screening Assays, Antitumor ; HSP70 Heat-Shock Proteins ; antagonists & inhibitors ; metabolism ; HSP90 Heat-Shock Proteins ; antagonists & inhibitors ; metabolism ; Heat-Shock Proteins ; antagonists & inhibitors ; metabolism ; Humans ; Molecular Chaperones ; Pharmaceutical Preparations ; administration & dosage ; chemical synthesis

MDR1 promoter has been shown to contain heat shock elements (HSE), and it has been reported that FM3A/M and P388/M MDR cells show a constitutively activated heat shock factor (HSF), suggesting that HSF might be an important target for reversing the multidrug resistance. Therefore, it was examined whether quercetin, which has been shown to interfere with the formation of the complex between HSE and HSF, and to downregulate the level of HSF1, can sensitize MDR cells against anticancer drugs by inhibition of HSF DNA-binding activity. In this study, quercetin appeared to inhibit the constitutive HSF DNA-binding activity and the sodium arsenite-induced HSF DNA-binding activity in the MDR cells. The basal and sodium arsenite-induced MDRCAT activities were remarkably suppressed by the treatment of quercetin. These results were well consistent with the finding that the treatment of quercetin decreased the expression level of P-gp, MDR1 gene product, in dose-dependent manner, and markedly increased the sensitivity of MDR cells to vincristine or vinblastine. These results suggest that quercetin can decrease the expression of P-gp via inhibition of HSF DNA-binding activity, and might be useful as a chemosensitizer in MDR cells.
Animal ; Antineoplastic Agents/pharmacology ; Arsenites/pharmacology ; Carcinoma/drug therapy ; Drug Resistance, Multiple/physiology* ; Drug Resistance, Neoplasm/physiology ; Heat-Shock Proteins/metabolism ; Heat-Shock Proteins/drug effects* ; Heat-Shock Proteins/antagonists & inhibitors ; Leukemia, Experimental/drug therapy ; Mice ; P-Glycoprotein/genetics ; P-Glycoprotein/drug effects ; Quercetin/pharmacology* ; Sodium Compounds/pharmacology ; Tumor Cells, Cultured ; Vinblastine/pharmacology ; Vincristine/pharmacology

Two LAL family regulatory genes, gdmRI and gdmRII, were identified in the geldanamycin biosynthetic gene cluster of Streptomyces hygroscopicus 17997. Disruption of the two regulatory genes resulted in absolute elimination of geldanamycin biosynthesis. The complementation experiments using a single wild-type gene could restore geldanamycin production. These results indicated that both gdmRI and gdmRII were positive regulatory genes of the geldanamycin biosynthesis.
Anti-Bacterial Agents ; biosynthesis ; Benzoquinones ; metabolism ; Gene Expression Regulation, Bacterial ; HSP90 Heat-Shock Proteins ; antagonists & inhibitors ; Lactams, Macrocyclic ; metabolism ; Protein-Tyrosine Kinases ; antagonists & inhibitors ; Repressor Proteins ; genetics ; Streptomyces ; genetics ; metabolism ; Trans-Activators ; genetics

OBJECTIVE: To observe whether HSP70 could protect against H2O2-induced apoptosis in C2C12 myogenic cells by inhibiting Smac release from the mitochondria. METHODS: HSP70 gene and full length Smac gene was transiently transfected in C2C12 myogenic cells by lipofectamine and the protein levels of HSP70 and Smac were analysed by Western blotting. Hoechst 33 258 staining was used to examine cell morphological changes and to calculate percentage of apoptotic nuclei. DNA ladder pattern on agarose gel electrophoresis was used to observe the DNA fragmentation. Activities of caspase-3 and caspase-9 were assayed with Western blotting. The release of Smac from the mitochondria to the cytoplasm was observed by immunofluorescence. RESULTS: H2O2 ( 0.5 mmol/L ) activated caspase-3, caspase-9 8 h after the treatment and specific morphological changes of apoptosis 12 h after the treatment, and overexpression of Smac significantly promoted H2O2-induced activation of caspase-3, caspase-9 and apoptosis in C2C12 myogenic cells. HSP70 overexpression significantly inhibited H2O2-induced and Smac-promoted apoptosis, as shown by no specific DNA ladder pattern in agarose gel electrophoresis, decrease of percentage of apoptotic nuclei, and marked inactivation of caspase-3 and caspase-9. HSP70 could inhibit the release of Smac from the mitochondria to the cytoplasm 2 h after the treatment by H2O2. CONCLUSION HSP70 inhibits Smac release from the mitochondria and protects against H2O2-induced apoptosis in C2C12 myogenic cells.
Apoptosis ; drug effects ; Apoptosis Regulatory Proteins ; Cells, Cultured ; HSP70 Heat-Shock Proteins ; pharmacology ; Humans ; Hydrogen Peroxide ; Intracellular Signaling Peptides and Proteins ; metabolism ; Mitochondria, Heart ; drug effects ; metabolism ; Mitochondrial Proteins ; antagonists & inhibitors ; metabolism ; Myoblasts ; metabolism ; Myocytes, Cardiac ; drug effects ; metabolism

OBJECTIVETo explore the signal transduction pathway in the differentiation and apoptosis of leukemia cells induced by heat shock protein 90 (HSP90) inhibitor 17-Allyl amide-17-demethoxygeldanamycin (17AAG).

METHODSKasumi-1 cells were treated with increasing concentrations or exposure time of 17AAG. The total kit protein (CD117), phosphorylated kit protein and its downstream signaling molecules were measured by Western blot analysis. Mutated kit protein from control and 17AAG-treated Kasumi-1 cells was immunoprecipitated and immunoblotted for associated chaperones.

RESULTSTotal kit protein and kit activity were decreased in 17AAG treated cells, but c-kit mRNA level was not. Total AKT protein and phospho-AKT, as well as phospho-STAT3 were rapidly down-regulated in Kasumi-1 cell after treatment with 17AAG. There was no change in total STAT3 protein. Immunoprecipitation showed that 1 microM 17AAG treatment for 1 hour caused kit associated HSP90 decrease and HSP70 increase.

CONCLUSION17AAG-induced apoptosis of Kasumi-1 cells is associated with a decline in Asn822Lys mutated kit protein level and phosphorylated kit, and with a downregulation in its downstream activated signaling molecules involved in proliferation. AKT is a client protein of HSP90. The changes of kit associated HSP90 and HSP70 satisfy the circulation mode of molecular chaperone complex.

Apoptosis ; drug effects ; Benzoquinones ; pharmacology ; Cell Differentiation ; drug effects ; HSP90 Heat-Shock Proteins ; antagonists & inhibitors ; Heat-Shock Proteins ; metabolism ; Humans ; Lactams, Macrocyclic ; pharmacology ; Leukemia ; metabolism ; pathology ; Proto-Oncogene Proteins c-akt ; metabolism ; Proto-Oncogene Proteins c-kit ; metabolism ; STAT3 Transcription Factor ; metabolism ; Signal Transduction ; drug effects ; Tumor Cells, Cultured

Heat shock protein 27 (HSP27) is a member of the small heat shock proteins (sHSP) and has multiple functions, it also plays an important role in the life cycle of some viruses. To investigate the regulatory effect of HSP27 during influenza virus infection, we cloned and expressed human HSP27 in both prokaryotic and eukaryotic cells, and demonstrated that HSP27 interacted with influenza A virus NS1 protein both in vivo and in vitro. Luciferase assay showed that HSP27 inhibited the expression of interferon-beta (IFN-beta) in infected cells, and independent of its phosphorylation. Moreover, HSP27 enhanced the inhibitory effect of NS1 on the expression of IFN-beta. Further analysis indicated that HSP27 exerted the inhibitory effect probably through influencing MDA5 of the RIG-I like helicase (RLH) pathway. The results suggested that HSP27 play a role in the innate immunity of infected cells, contributed to our understanding of the regulatory effect of host factors during influenza virus infection.
Cell Line ; Gene Expression Regulation, Viral ; HEK293 Cells ; HSP27 Heat-Shock Proteins ; genetics ; pharmacology ; Humans ; Influenza, Human ; genetics ; immunology ; Interferon-beta ; antagonists & inhibitors ; metabolism ; Viral Nonstructural Proteins ; genetics ; pharmacology

OBJECTIVETo explore the effect of 17-allylamide-17-demethoxygeldanamycin (17AAG), a heat shock protein 90 (HSP90) inhibitor, on the growth, differentiation and apoptosis of leukemic Kasumi-1 cells.

METHODSKasumi-1 cells were treated with 17AAG at different concentrations in suspension culture. Cell proliferation was analysed by MTT assay, expression of myeloid-specific differentiation antigen and cell cycle by flow cytometry, cell apoptosis by annexin V staining, agarose gel electrophoresis and flow cytometry. KIT protein was analysed by Western blot and c-kit mRNA by RT-PCR.

RESULTS17AAG treatment caused a dose-dependent inhibition of the cell proliferation with the IC(50) of 0.62 micromol/L. A dose-dependent increase in early apoptosis occurred at 24 hours treatment and in late apoptosis at 48 hours treatment. 17AAG induced a time- and dose-dependent increase in expression of myeloid cell surface protein CD11b and CD15, a progressive decline in S-phase cell fraction and an increase in G(0)/G(1) cells. When Kasumi-1 cells were incubated with 1 micromol/L of 17AAG, KIT protein began to decrease at 2 hours and KIT protein could hardly be detected at 20 hours, but c-kit mRNA was not decreased.

CONCLUSION17AAG treatment of Kasumi-1 cells could lower KIT protein expression, inhibit cell proliferation, induce cell partial differentiation, apoptosis and accumulation in G(0)/G(1) phase.

Apoptosis ; drug effects ; Benzoquinones ; pharmacology ; Cell Cycle ; drug effects ; Cell Differentiation ; drug effects ; Cell Line, Tumor ; Cell Proliferation ; drug effects ; HSP90 Heat-Shock Proteins ; antagonists & inhibitors ; Humans ; Lactams, Macrocyclic ; pharmacology ; Proto-Oncogene Proteins c-kit ; genetics ; metabolism ; RNA, Messenger ; genetics

OBJECTIVETo investigate the antitumor efficacy and mechanism of HSP90 inhibitor FW-04-806 against Bcr/Abl(+) leukemia K562 and HL60 cells and their mechanisms of action.

METHODSMTT assay was used to assess the proliferation-inhibiting effect of FW-04-806. Cell cycle was analyzed with propidium iodide by flow cytometry. Cell apoptosis was determined using the FITC mV apoptosis detection kit. Western blot was applied to reveal the protein expression of related proliferative and apoptotic signaling pathways. The changes of mitochondrial membrane potential were detected by flow cytometry. Protein-protein interactions was shown by co-immunoprecipitation. The level of mRNA was assessed by real-time RT-PCR.

RESULTSFW-04-806 obviously inhibited cell proliferation in the HL60, K562 and HL60/Bcr-Abl cell lines, with an IC50 of (30.89 ± 0.12) µmol/L, (9.76 ± 0.19) µmol/L and (8.03 ± 0.26) µmol/L, respectively (P<0.001). Compared with the vehicle group, the two increasing doses of FW-04-806 showed inhibition of tumor growth at a rate of (17.40 ± 0.34)% and (34.33 ± 5.00)%, respectively, in the K562 cell line groups (P=0.003), and (18.90 ± 1.45)% and (35.60 ± 3.55)% (P=0.001) in the HL60/Bcr-Abl cell line groups. FW-04-806 dissociated Hsp90/Cdc37 chaperon/co-chaperon complex, followed by degradation of the Hsp90 proteins through proteasome pathway without affecting mRNA expression. FW-04-806 induced apoptosis and led to G2/M arrest.

CONCLUSIONOur findings indicate that FW-04-806 displays potential antitumor effect by suppressing the proliferation and apoptosis in Bcr/Abl(+) leukemia cells in vivo.

Apoptosis ; drug effects ; Cell Cycle ; Cell Proliferation ; drug effects ; Fusion Proteins, bcr-abl ; HL-60 Cells ; HSP90 Heat-Shock Proteins ; antagonists & inhibitors ; Humans ; K562 Cells ; Leukemia ; drug therapy ; metabolism ; pathology ; Membrane Potential, Mitochondrial ; Oxazoles ; pharmacology ; RNA, Messenger ; metabolism ; Signal Transduction

Oxidized LDL (OxLDL), a causal factor in atherosclerosis, induces the expression of heat shock proteins (Hsp) in a variety of cells. In this study, we investigated the role of CD36, an OxLDL receptor, and peroxisome proliferator-activated receptor gamma (PPAR gamma) in OxLDL-induced Hsp70 expression. Overexpression of dominant-negative forms of CD36 or knockdown of CD36 by siRNA transfection increased OxLDL-induced Hsp70 protein expression in human monocytic U937 cells, suggesting that CD36 signaling inhibits Hsp70 expression. Similar results were obtained by the inhibition of PPAR gamma activity or knockdown of PPAR gamma expression. In contrast, overexpression of CD36, which is induced by treatment of MCF-7 cells with troglitazone, decreased Hsp70 protein expression induced by OxLDL. Interestingly, activation of PPAR gamma through a synthetic ligand, ciglitazone or troglitazone, decreased the expression levels of Hsp70 protein in OxLDL-treated U937 cells. However, major changes in Hsp70 mRNA levels were not observed. Cycloheximide studies demonstrate that troglitazone attenuates Hsp70 translation but not Hsp70 protein stability. PPAR gamma siRNA transfection reversed the inhibitory effects of troglitazone on Hsp70 translation. These results suggest that CD36 signaling may inhibit stress- induced gene expression by suppressing translation via activation of PPAR gamma in monocytes. These findings reveal a new molecular basis for the anti-inflammatory effects of PPAR gamma.
Antigens, CD36/*physiology ; Cell Line, Tumor ; Chromans/pharmacology ; Cycloheximide/pharmacology ; HSP70 Heat-Shock Proteins/*biosynthesis ; Humans ; Lipoproteins, LDL/pharmacology/*physiology ; Monocytes/drug effects/metabolism ; PPAR gamma/agonists/antagonists & inhibitors/*physiology ; Protein Synthesis Inhibitors/pharmacology ; Signal Transduction ; Thiazolidinediones/pharmacology