Measurement of the novel antitumor agent 17-(allylamino)-17-demethoxygeldanamycin in human plasma by high-performance liquid chromatography

Agnew, Elizabeth B.; Wilson, Richard H.; Grem, Jean L.; Neckers, Leonard Μ.; Bi, Daoqin; Takimoto, Chris H.

doi:10.1016/s0378-4347(01)00113-x

Cited by 25 publications

(11 citation statements)

References 6 publications

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“…The molecular mass cutoff of the filters was 3 kDa; the molecular mass of GA is 0.56 kDa, so the flow-through containing excess GA was discarded and the retentate was collected. Because GA itself may have an inhibitory effect on this assay, we confirmed that this approach efficiently removed GA from conditioned medium by subjecting media preparations containing known concentrations of GA to filtration and measuring the drug remaining in the retentate by high-performance liquid chromatography, as previously described (52). It was determined that the amount of GA remaining after two successive filtration spins was negligible when the starting concentration did not exceed 0.5 M. The final filter retentate was concentrated 3-fold for use in the angiogenesis assay.…”

Section: Cellsupporting

confidence: 54%

Hsp90 Regulates a von Hippel Lindau-independent Hypoxia-inducible Factor-1α-degradative Pathway

Isaacs

Jung

Mimnaugh

et al. 2002

Journal of Biological Chemistry

634

461

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HIF-1␣ is a normally labile proangiogenic transcription factor that is stabilized and activated in hypoxia. Although the von Hippel Lindau (VHL) gene product, the ubiquitin ligase responsible for regulating HIF-1␣ protein levels, efficiently targets HIF-1␣ for rapid proteasome-dependent degradation under normoxia, HIF-1␣ is resistant to the destabilizing effects of VHL under hypoxia. HIF-1␣ also associates with the molecular chaperone Hsp90. To examine the role of Hsp90 in HIF-1␣ function, we used renal carcinoma cell (RCC) lines that lack functional VHL and express stable HIF-1␣ protein under normoxia. Geldanamycin (GA), an Hsp90 antagonist, promoted efficient ubiquitination and proteasome-mediated degradation of HIF-1␣ in RCC in both normoxia and hypoxia. Furthermore, HIF-1␣ point mutations that block VHL association did not protect HIF-1␣ from GA-induced destabilization. Hsp90 antagonists also inhibited HIF-1␣ transcriptional activity and dramatically reduced both hypoxiainduced accumulation of VEGF mRNA and hypoxiadependent angiogenic activity. These findings demonstrate that disruption of Hsp90 function 1) promotes HIF-1␣ degradation via a novel, oxygen-independent E3 ubiquitin ligase and 2) diminishes HIF-1␣ transcriptional activity. Existence of an Hsp90-dependent pathway for elimination of HIF-1␣ predicts that Hsp90 antagonists may be hypoxic cell sensitizers and possess antiangiogenic activity in vivo, thus extending the utility of these drugs as therapeutic anticancer agents.Hypoxia-inducible factor-1␣ (HIF-1␣) 1 is a component of a transcriptional complex that is extremely labile under normoxia but is stabilized and activated under hypoxia (1). Because HIF-1␣ regulates a variety of processes such as angiogenesis and glucose metabolism, it is acknowledged to be a critically important tumor cell survival factor that is required for tumorigenesis in many cancer models and is expressed in a majority of metastases and late stage tumors. The rapid degradation of HIF-1␣ in normoxic cells is mediated by the tumor suppressor VHL, which, together with a multimeric protein complex, serves as its E3 ubiquitin protein ligase (2-5). Under hypoxic conditions, the stabilization and activation of HIF-1␣ is due to an inability of VHL to associate with and ubiquitinate HIF-1␣. It was recently shown that hypoxic conditions impair the ability of a class of enzymes termed prolyl hydroxylases to modify two separate consensus proline motifs present on HIF-1␣ (6 -10). These modifications are required for VHL to associate with and ubiquitinate HIF-1␣, thereby targeting the protein for proteasome-dependent degradation.HIF-1␣ is constitutively stabilized in normoxic tumors and in cell lines that are VHL null or that express a nonfunctional mutant form of VHL. This occurs in over 50% of sporadic RCCs and clear cell RCCs (11), the most common malignant neoplasm of the kidney, and one of the few human tumors known to depend upon VHL inactivation. The importance of VHL function is further demonstrated in VHL disease, a human cancer ...

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Section: Cellsupporting

confidence: 54%

Hsp90 Regulates a von Hippel Lindau-independent Hypoxia-inducible Factor-1α-degradative Pathway

Isaacs

Jung

Mimnaugh

et al. 2002

Journal of Biological Chemistry

634

461

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“…Preliminary data obtained from these trials demonstrate predicted biological activity achieved at drug concentrations below the maximally tolerated dose [53]. Additionally, the findings demonstrate that dose-limiting hepatotoxicity occurs after several days of daily drug administration, while once-weekly administration of a much higher drug dose is significantly better tolerated.…”

Section: Use Of Hsp90 Inhibitors As Single Agents: Cytostatic or Cytomentioning

confidence: 81%

Heat-shock protein 90 inhibitors as novel cancer chemotherapeutic agents

Neckers

2002

Expert Opinion on Emerging Drugs

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Heat-shock protein 90 (Hsp90) is a molecular chaperone whose association is required for the stability and function of multiple mutated, chimeric and overexpressed signalling proteins that promote cancer cell growth and/or survival. Hsp90 client proteins include mutated p53, Bcr-Abl, Raf-1, Akt, HER2/Neu (ErbB2) and hypoxia inducible factor-1alpha (HIF-1alpha). Through specific interaction with a single molecular target, Hsp90 inhibitors cause the destabilisation and eventual degradation of Hsp90 client proteins, and they have shown promising antitumour activity in preclinical model systems. One Hsp90 inhibitor, 17-allylamino-geldanamycin (17-AAG), is currently in Phase I clinical trials. Hsp90 inhibitors are unique in that, although they are directed towards a specific molecular target, they simultaneously inhibit multiple signalling pathways on which cancer cells depend for growth and survival. Further, because of the unique effect that Hsp90 inhibition has on cancer cells, combination of an Hsp90 inhibitor with standard chemotherapeutic agents may dramatically increase the in vivo efficacy of the standard agent.

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“…However, continued characterization of the ansamycin-binding site on HSP90 may make it possible to develop more substrate-or tissue-specific HSP90 inhibitors. In fact, the geldanamycin analog, 17-allylamino-17-desmethoxygeldanamycin, is currently in a Phase I clinical trial at the NCI (48). Structurally different HSP90 binding drugs, such as radicicol, were also introduced as another class of HSP90 inhibitor.…”

Section: Discussionmentioning

confidence: 99%

The Heat Shock Protein 90-Binding Geldanamycin Inhibits Cancer Cell Proliferation, Down-Regulates Oncoproteins, and Inhibits Epidermal Growth Factor-Induced Invasion in Thyroid Cancer Cell Lines

Park¹,

Yeh²,

Wong³

et al. 2003

The Journal of Clinical Endocrinology & Metabolism

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Heat shock protein 90 (HSP90) serves as a chaperone protein and plays a critical role in tumor cell growth and/or survival. Geldanamycin, a specific inhibitor of HSP90, is cytotoxic to several human cancer cell lines, but its effect in thyroid cancer is unknown. We, therefore, investigated the effect of geldanamycin on cell proliferation, oncoprotein expression, and invasion in human thyroid cancer cell lines. We used six thyroid cancer cell lines: TPC-1 (papillary), FTC-133, FTC-236, FTC-238 (follicular), XTC-1 (Hürthle cell), and ARO (anaplastic). We used the dimethyl-thiazol-diphenyltetrazolium bromide assay, a clonogenic assay, an apoptotic assay, and a Matrigel invasion assay. We evaluated oncoprotein expression using Western blots and flow cytometry. After 6 d of treatment with 50 nM geldanamycin, the percent inhibition of growth was 29.4% in TPC-1, 97.5% in FTC-133, 96.7% in FTC-236, 10.8% in FTC-238, 70.9% in XTC-1, and 45.5% in ARO cell lines. In the FTC-133 cell line, geldanamycin treatment decreased clonogenicity by 21% at a concentration of 50 nM; geldanamycin induced apoptosis and down-regulated c-Raf-1, mutant p53, and epidermal growth factor (EGF) receptor expression; geldanamycin inhibited EGF-stimulated invasion. In conclusion, geldanamycin inhibited cancer cell proliferation, down-regulated oncoproteins, and inhibited EGF-induced invasion in thyroid cancer cell lines.

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Measurement of the novel antitumor agent 17-(allylamino)-17-demethoxygeldanamycin in human plasma by high-performance liquid chromatography

Cited by 25 publications

References 6 publications

Hsp90 Regulates a von Hippel Lindau-independent Hypoxia-inducible Factor-1α-degradative Pathway

Hsp90 Regulates a von Hippel Lindau-independent Hypoxia-inducible Factor-1α-degradative Pathway

Heat-shock protein 90 inhibitors as novel cancer chemotherapeutic agents

The Heat Shock Protein 90-Binding Geldanamycin Inhibits Cancer Cell Proliferation, Down-Regulates Oncoproteins, and Inhibits Epidermal Growth Factor-Induced Invasion in Thyroid Cancer Cell Lines

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