Measuring the pharmacodynamic effects of a novel Hsp90 inhibitor on HER2/ neu expression in mice using (89)Zr-DFO-trastuzumab Journal Article
| Authors: | Holland, J. P.; Caldas-Lopes, E.; Divilov, V.; Longo, V. A.; Taldone, T.; Zatorska, D.; Chiosis, G.; Lewis, J. S. |
| Article Title: | Measuring the pharmacodynamic effects of a novel Hsp90 inhibitor on HER2/ neu expression in mice using (89)Zr-DFO-trastuzumab |
| Abstract: | Background:The positron-emitting radionuclide 89Zr (t 1/2 = 3.17 days) was used to prepare 89Zr-radiolabeled trastuzumab for use as a radiotracer for characterizing HER2/neu-positive breast tumors. In addition, pharmacodynamic studies on HER2/ neu expression levels in response to therapeutic doses of PU-H71 (a specific inhibitor of heat-shock protein 90 [Hsp90]) were conducted. Methodology/Principal Findings: Trastuzumab was functionalized with desferrioxamine B (DFO) and radiolabeled with [ 89Zr]Zr-oxalate at room temperature using modified literature methods. ImmunoPET and biodistribution experiments in female, athymic nu/nu mice bearing sub-cutaneous BT-474 (HER2/neu positive) and/or MDA-MB-468 (HER2/neu negative) tumor xenografts were conducted. The change in 89Zr-DFO- trastuzumab tissue uptake in response to high- and low-specific-activity formulations and co-administration of PU-H71 was evaluated by biodistribution studies, Western blot analysis and immunoPET. 89Zr-DFO-trastuzumab radiolabeling proceeded in high radiochemical yield and specific-activity 104.3±2.1 MBq/mg (2.82±0.05 mCi/mg of mAb). In vitro assays demonstrated >99% radiochemical purity with an immunoreactive fraction of 0.87±0.07. In vivo biodistribution experiments revealed high specific BT-474 uptake after 24, 48 and 72 h (64.68±13.06%ID/g; 71.71±10.35%ID/g and 85.18±11.10%ID/g, respectively) with retention of activity for over 120 h. Pre-treatment with PU-H71 was followed by biodistribution studies and immunoPET of 89Zr-DFO-trastuzumab. Expression levels of HER2/neu were modulated during the first 24 and 48 h post-administration (29.75±4.43%ID/g and 41.42±3.64%ID/g, respectively). By 72 h radiotracer uptake (73.64±12.17%ID/g) and Western blot analysis demonstrated that HER2/neu expression recovered to baseline levels. Conclusions/Significance: The results indicate that 89Zr-DFO- trastuzumab provides quantitative and highly-specific delineation of HER2/neu positive tumors, and has potential to be used to measure the efficacy of long-term treatment with Hsp90 inhibitors, like PU-H71, which display extended pharmacodynamic profiles. Copyright: © 2010 Holland et al. |
| Keywords: | controlled study; unclassified drug; human cell; nonhuman; positron emission tomography; mouse; mus; pharmacodynamics; epidermal growth factor receptor 2; animal experiment; animal model; in vivo study; in vitro study; tumor xenograft; drug specificity; gene expression regulation; drug distribution; drug uptake; isotope labeling; nude mouse; breast tumor; western blotting; heat shock protein 90 inhibitor; pu h71; tracer; trastuzumab; zirconium; zirconium 89; deferoxamine; oxalate zr 89; cell strain; cell strain bt 474; cell strain mda mb 468 |
| Journal Title: | PLoS ONE |
| Volume: | 5 |
| Issue: | 1 |
| ISSN: | 1932-6203 |
| Publisher: | Public Library of Science |
| Date Published: | 2010-01-25 |
| Start Page: | e8859 |
| Language: | English |
| DOI: | 10.1371/journal.pone.0008859 |
| PROVIDER: | scopus |
| PMCID: | PMC2810330 |
| PUBMED: | 20111600 |
| DOI/URL: | |
| Notes: | --- - "Cited By (since 1996): 1" - "Export Date: 20 April 2011" - "Art. No.: e8859" - "Source: Scopus" |
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