Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0006142 (breast cancer)
 160,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

BAG family proteins are regulatory co-chaperones for heat shock protein (Hsp) 70. Hsp70 facilitates the removal of injured proteins by ubiquitin-mediated proteasomal degradation. This process can be driven by geldanamycin, an irreversible blocker of Hsp90. We hypothesize that CAIR-1/BAG-3 inhibits Hsp-mediated proteasomal degradation. Human breast cancer cells were engineered to overexpress either full-length CAIR-1 (FL), which binds Hsp70, or a BAG domain-deletion mutant (dBAG) that cannot bind Hsp70. FL overexpression prevented geldanamycin-mediated loss of total and phospho-Akt and other Hsp client proteins. dBAG provided no protection, indicating a requirement for Hsp70 binding. Ubiquitinated Akt accumulated in FL-expressing cells, mimicking the effect of lactacystin proteasomal inhibition, indicating that CAIR-1 inhibits proteasomal degradation distal to protein ubiquitination in a BAG domain-dependent manner. Protein protection in FL cells was generalizable to downstream Akt targets, GSK3beta, P70S6 kinase, CREB, and other Hsp client proteins, including Raf-1, cyclin-dependent kinase 4, and epidermal growth factor receptor. These findings suggest that Hsp70 is a chaperone driving a multiprotein degradation complex and that the inhibitory co-chaperone CAIR-1 functions distal to client ubiquitination. Furthermore, poly-ubiquitination is not sufficient for efficient proteasomal targeting of Hsp client proteins.
 ...
PMID:CAIR-1/BAG-3 abrogates heat shock protein-70 chaperone complex-mediated protein degradation: accumulation of poly-ubiquitinated Hsp90 client proteins. 1275 Mar 78

Id proteins bind basic helix-loop-helix transcription factors and function as dominant negative inhibitors of gene expression. Id1 and Id3 are required for the recruitment of bone marrow-derived endothelial cell precursors and tumors transplanted into Id-deficient mice demonstrate impaired angiogenesis. Mouse mammary tumor virus-neu mice were bred with Id1-/-Id3+/- mice to ascertain the role of Id1 and Id3 in mammary tumorigenesis in a more physiologically relevant model. In mammary tumors from these mice, Id1 and Id3 expression was restricted to the vascular endothelium. Id1 and Id3 deficiency did not prevent or delay tumor formation but did alter tumor phenotype. The tumors that developed in the Id-deficient mice were larger and cystic with a viable rim of tumor cells surrounding a nonviable core of cellular debris. The Hsp90 chaperone protein is required for cellular survival under condition of environmental stress and for the stability of the neu oncogene. 17-Allylamino-17-demethoxygeldanamycin, an Hsp90 inhibitor, was used to treat these mice. Whereas 17-allylamino-17-demethoxygeldanamycin only modestly delayed the growth of established mammary tumors in WT mice for Id, tumor suppression was dramatically more effective in an Id1- or Id3-deficient background. These data suggest that tumorigenesis can occur in a background of defective angiogenesis but that tumors developing in such an environment may be especially sensitive to inhibitors of neu and stress-activated survival pathways. Thus angiogenesis inhibitors in combination with inhibitors of Hsp90 function should be evaluated for the treatment of advanced breast cancer.
 ...
PMID:Angiogenesis impairment in Id-deficient mice cooperates with an Hsp90 inhibitor to completely suppress HER2/neu-dependent breast tumors. 1452 2

Radicicol, a macrocyclic antibiotic produced by fungi, was originally isolated many years ago, and was described as tyrosine kinase inhibitor. We also rediscovered radicicol as an inhibitor of signal transduction of oncogene products, such as K-ras and v-Src, using yeast and mammalian cell-based assays. In a study of mechanisms of action, it was revealed that radicicol depletes the Hsp90 client signaling molecules in cells, and thus inhibit the signal transduction pathway. In addition, direct binding of radicicol to the N-terminal ATP/ADP binding site of Hsp90 was shown, and thus radicicol has been recognized as a structurally unique antibiotic that binds and inhibits the molecular chaperone Hsp90. Although radicicol itself has little or no activity in animals because of instability in animals, its oxime derivatives showed potent antitumor activities against human tumor xenograft models. Hsp90 client proteins were depleted and apoptosis was induced in the tumor specimen treated with radicicol oxime derivatives. Taken together, these results suggest that the antitumor activity of radicicol oxime derivatives is mediated by binding to Hsp90 and destabilization of Hsp90 client proteins in the tumor. Among Hsp90 clients, we focused on ErbB2 and Bcr-Abl as examples of important targets of Hsp90 inhibitors. Radicicol oxime showed potent antitumor activity against ER negative/ErbB2 overexpressing breast cancer and Bcr-Abl expressing CML. Putative mechanisms of action and future directions of radicicol oxime against these kinds of tumor are discussed.
 ...
PMID:Development of radicicol analogues. 1452 87

A program currently ongoing in our laboratory envisions natural macrolide radicicol-based inhibitors targeting the molecular chaperone Hsp90. Such inhibitors can be potential anticancer agents due to their ability to induce the breakdown of a variety of oncogenic proteins. In this account, we first concern ourselves with a vastly important total synthesis of such an inhibitor. We accomplished this via a new approach, which we term the "ynolide method", directed to the synthesis of resorcinylic macrolides, including cycloproparadicicol and aigialomycin D. The key features of the syntheses involve cobalt-complexation-promoted ring-closing metathesis (RCM) to generate ynolides, followed by Diels-Alder reaction with dimedone-derived bis-siloxy dienes to elaborate the benzo system. A number of interesting analogues were synthesized using this protocol. They were evaluated for their inhibitory activity against the growth of breast cancer cell line, MCF-7. The potency of their cytotoxicity was found to be consistent with their ability to degrade the oncogenic protein, Her2. From these assays, cycloproparadicicol was identified as a most promising candidate for further development.
 ...
PMID:New efficient synthesis of resorcinylic macrolides via ynolides: establishment of cycloproparadicicol as synthetically feasible preclinical anticancer agent based on Hsp90 as the target. 1521 36

ErbB2 is a transmembrane tyrosine kinase whose surface overexpression is linked to tumorigenesis and poor prognosis in breast cancer patients. Two models have emerged that account for the high surface distribution of ErbB2. In one model, the surface pool is dynamic and governed by a balance between endocytosis and recycling, whereas in the other it is retained, static, and excluded from endocytosis. These models have contrasting implications for how ErbB2 exerts its biological function and how cancer therapies might down-regulate surface ErbB2, such as the antibody trastuzumab (Herceptin) or the Hsp90 inhibitor geldanamycin. Little is known, however, about how these treatments affect ErbB2 endocytic trafficking. To investigate this issue, we examined breast carcinoma cells by immunofluorescence and quantitative immunoelectron microscopy and developed imaging and trafficking kinetics assays using cell surface fluorescence quenching. Surprisingly, trastuzumab does not influence ErbB2 distribution but instead recycles passively with internalized ErbB2. By contrast, geldanamycin down-regulates surface ErbB2 through improved degradative sorting in endosomes exclusively rather than through increased endocytosis. These results reveal substantial dynamism in the surface ErbB2 pool and clearly demonstrate the significance of endosomal sorting in the maintenance of ErbB2 surface distribution, a critical feature of its biological function.
 ...
PMID:Endocytosis and sorting of ErbB2 and the site of action of cancer therapeutics trastuzumab and geldanamycin. 1538 31

A chimera composed of the natural products radicicol and geldanamycin has been prepared through an amide linkage connecting the resorcinol moiety of radicicol to the quinone ring of geldanamycin. The inhibitory activity of these compounds was determined by their ability to inhibit Hsp90's inherent ATPase activity along with degradation of the Hsp90 client protein, HER-2 in MCF-7 breast cancer cells. [reaction: see text]
 ...
PMID:Design, synthesis, and evaluation of a radicicol and geldanamycin chimera, radamide. 1554 50

Heat shock protein 90 is a molecular chaperone whose association is required for stability and function of multiple mutated, chimeric, and over-expressed signaling proteins that promote cancer cell growth and/or survival. Hsp90 client proteins important in breast cancer include the estrogen receptor, the serine-threonine kinases Raf-1 and Akt, the receptor tyrosine kinase ErbB2/Neu, and the hypoxia inducible transcription factor HIF-1alpha. Hsp90 small molecule inhibitors, by interacting specifically with a single molecular target, thus promote the destabilization and eventual degradation of multiple cancer cell survival and growth promoting proteins, and these inhibitors have shown promising anti-tumor activity in preclinical breast cancer model systems. One Hsp90 inhibitor, 17-AAG, is currently in Phase I clinical trial. Because of their unique ability to inhibit multiple survival pathways utilized by cancer cells, combination of Hsp90 inhibitors with standard chemotherapeutic agents may dramatically increase in vivo efficacy.
 ...
PMID:Heat shock protein 90 is a rational molecular target in breast cancer. 1568 45

[reaction: see text]. The antitumor antibiotics radicicol and geldanamycin are potent inhibitors of the Hsp90 protein folding machinery. Radester is a hybrid composed of radicicol's resorcinol ring and geldanamycin's quinone through an isopropyl ester. Radester was prepared, and the cytotoxicity of it and the corresponding hydroquinone were determined in MCF-7 breast cancer cells to be 13.9 and 7.1 microM, respectively. Protein degradation assays were performed on Hsp90-dependent client proteins, Her-2 and Raf, to correlate Hsp90 inhibition to cytotoxicity.
 ...
PMID:Radester, a novel inhibitor of the Hsp90 protein folding machinery. 1590 Nov 58

We have examined the role of NAD(P)H:quinone oxidoreductase 1 (NQO1) in the bioreductive metabolism of 17-allylamino-demethoxygeldanamycin (17-AAG). High-performance liquid chromatography (HPLC) analysis of the metabolism of 17-AAG by recombinant human NQO1 revealed the formation of a more polar metabolite 17-AAGH2. The formation of 17-AAGH2 was NQO1 dependent, and its formation could be inhibited by the addition of 5-methoxy-1,2-dimethyl-3-[(4-nitrophenoxy)methyl]indole-4,7-dione (ES936), a mechanism-based (suicide) inhibitor of NQO1. The reduction of 17-AAG to the corresponding hydroquinone 17-AAGH2 was confirmed by tandem liquid chromatography-mass spectrometry. 17-AAGH2 was relatively stable and only slowly underwent autooxidation back to 17-AAG over a period of hours. To examine the role of NQO1 in 17-AAG metabolism in cells, we used an isogenic pair of human breast cancer cell lines differing only in NQO1 levels. MDA468 cells lack NQO1 due to a genetic polymorphism, and MDA468/NQ16 cells are a stably transfected clone that express high levels of NQO1 protein. HPLC analysis of 17-AAG metabolism using cell sonicates and intact cells showed that 17-AAGH2 was formed by MDA468/NQ16 cells, and formation of 17-AAGH2 could be inhibited by ES936. No 17-AAGH2 was detected in sonicates or intact MDA468 cells. Following a 4-hour treatment with 17-AAG, the MDA468/NQ16 cells were 12-fold more sensitive to growth inhibition compared with MDA468 cells. More importantly, the increased sensitivity of MDA468/NQ16 cells to 17-AAG could be abolished if the cells were pretreated with ES936. Cellular markers of heat shock protein (Hsp) 90 inhibition, Hsp70 induction, and Raf-1 degradation were measured by immunoblot analysis. Marked Hsp70 induction and Raf-1 degradation was observed in MDA468/NQ16 cells but not in MDA468 cells. Similarly, downstream Raf-1 signaling molecules mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase and ERK also showed decreased levels of phosphorylation in MDA468/NQ16 cells but not in MDA468 cells. The ability of 17-AAG and 17-AAGH2 to inhibit purified yeast and human Hsp90 ATPase activity was examined. Maximal 17-AAG-induced ATPase inhibition was observed in the presence of NQO1 and could be abrogated by ES936, showing that 17-AAGH2 was a more potent Hsp90 inhibitor compared with 17-AAG. Molecular modeling studies also showed that due to increased hydrogen bonding between the hydroquinone and the Hsp90 protein, 17-AAGH2 was bound more tightly to the ATP-binding site in both yeast and human Hsp90 models. In conclusion, these studies have shown that reduction of 17-AAG by NQO1 generates 17-AAGH2, a relatively stable hydroquinone that exhibits superior Hsp90 inhibition.
 ...
PMID:Formation of 17-allylamino-demethoxygeldanamycin (17-AAG) hydroquinone by NAD(P)H:quinone oxidoreductase 1: role of 17-AAG hydroquinone in heat shock protein 90 inhibition. 1626 26

ErbB2, a member of the EGF receptor family of tyrosine kinases is overexpressed on many tumor cells of epithelial origin and is the molecular target of trastuzumab (Herceptin), the first humanized antibody used in the therapy of solid tumors. Trastuzumab, which is thought to act, at least in part, by downregulating ErbB2 expression is only effective in approximately 30-40% of ErbB2 positive breast tumors. Geldanamycin and its derivative 17-AAG are potential antitumor agents capable of downregulating client proteins of Hsp90, including ErbB2. To investigate the ability of 17-AAG to downregulate ErbB2 in trastuzumab resistant breast cancer cells and the possibility of 17-AAG and trastuzumab potentiating each other's effect, the recently established trastuzumab resistant breast cancer cell line, JIMT-1 was compared to the known trastuzumab sensitive SKBR-3 line. Baseline and stimulus-evoked dimerization and activation levels of ErbB2, and the effects of trastuzumab and 17-AAG alone and in combination on cell proliferation and apoptosis, as well as on ErbB2 expression and phosphorylation have been measured. Baseline activation and amenability to activation and downregulation by trastuzumab was much lower in the resistant line. However, 17-AAG enhanced ErbB2 homodimerization after 5-10 min of treatment in both cell lines, and decreased proliferation with an IC50 of 70 nM for SKBR-3 and 10nM for JIMT-1. Thus, 17-AAG may be a useful drug in trastuzumab resistant ErbB2 overexpressing tumors. The antiproliferative effect of 17-AAG was positively correlated with phosphorylation and downregulation of ErbB2 and was dominated by apoptosis, although, especially at higher doses, necrosis was also present. Interestingly, IC50 values for ErbB2 downregulation and phosphorylation, in the 30-40 nM range, were not significantly different for the two cell lines. This observation and the negative correlation between resting ErbB2 levels and the antiproliferative effect of 17-AAG may indicate that activation of ErbB2 to some extent could counteract the overall cytostatic effect, especially at higher levels of ErbB2 expression. The usual therapeutic dose of trastuzumab did not change the IC50 of 17-AAG on the proliferation of either cell line, but nevertheless decreased overall ErbB2 phosphorylation and at low doses of 17-AAG further decreased cell growth in the sensitive SKBR-3, thus trastuzumab may be a good combination partner to counteract undesired activating effects of 17-AAG.
 ...
PMID:Hsp90 inhibitor 17-AAG reduces ErbB2 levels and inhibits proliferation of the trastuzumab resistant breast tumor cell line JIMT-1. 1638 10


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>