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Z3, a novel Jak2 tyrosine kinase small-molecule inhibitor that suppresses Jak2-mediated pathologic cell growth.

ABSTRACT: Jak2 tyrosine kinase is essential for animal development and hyperkinetic Jak2 function has been linked to a host of human diseases. Control of this pathway using Jak2-specific inhibitors would therefore potentially serve as a useful research tool and/or therapeutic agent. Here, we used a high-throughput program called DOCK to predict the ability of 20,000 small molecules to interact with a structural pocket adjacent to the ATP-binding site of murine Jak2. One small molecule, 2-methyl-1-phenyl-4-pyridin-2-yl-2-(2-pyridin-2-ylethyl)butan-1-one (herein designated as Z3), bound to Jak2 with a favorable energy score. Z3 inhibited Jak2-V617F and Jak2-WT autophosphorylation in a dose-dependent manner but was not cytotoxic to cells at concentrations that inhibited kinase activity. Z3 selectively inhibited Jak2 kinase function with no effect on Tyk2 or c-Src kinase function. Z3 significantly inhibited proliferation of the Jak2-V617F-expressing, human erythroleukemia cell line, HEL 92.1.7. The Z3-mediated reduction in cell proliferation correlated with reduced Jak2 and STAT3 tyrosine phosphorylation levels as well as marked cell cycle arrest. Finally, Z3 inhibited the growth of hematopoietic progenitor cells isolated from the bone marrow of an essential thrombocythemia patient harboring the Jak2-V617F mutation and a polycythemia vera patient carrying a Jak2-F537I mutation. Collectively, the data suggest that Z3 is a novel specific inhibitor of Jak2 tyrosine kinase.

SUBMITTER: Sayyah J

PROVIDER: S-EPMC2579271 | biostudies-literature | 2008 Aug

REPOSITORIES: biostudies-literature

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Z3, a novel Jak2 tyrosine kinase small-molecule inhibitor that suppresses Jak2-mediated pathologic cell growth.

Sayyah Jacqueline J Magis Andrew A Ostrov David A DA Allan Robert W RW Braylan Raul C RC Sayeski Peter P PP

Molecular cancer therapeutics 20080801 8

Jak2 tyrosine kinase is essential for animal development and hyperkinetic Jak2 function has been linked to a host of human diseases. Control of this pathway using Jak2-specific inhibitors would therefore potentially serve as a useful research tool and/or therapeutic agent. Here, we used a high-throughput program called DOCK to predict the ability of 20,000 small molecules to interact with a structural pocket adjacent to the ATP-binding site of murine Jak2. One small molecule, 2-methyl-1-phenyl-4 ...[more]

PMID: 18723478

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Project description:One of the most clinically relevant molecular aberrations in breast cancer is overexpression of human epidermal growth factor receptor type 2 (HER2). We aimed to develop a radiolabeled tyrosine kinase inhibitor for HER2-targeted breast cancer imaging. In this study, a radioiodinated analog (125/131I-IBA-CP) of the HER2-selective inhibitor CP724,714 was prepared and evaluated in HER2-positive or -negative subcutaneous human breast cancer xenografts. Methods: The CP724,714 analog IBA-CP was synthesized and assayed for its inhibitory activities against HER2 and 6 other tyrosine kinases. 125/131I-IBA-CP was prepared using a copper-mediated radioiodination method with enhanced labeling yield and molar activity. In vitro biologic activity, including specific and nonspecific binding of 131I-IBA-CP to its HER2 kinase target, was assessed in different cell lines. In vivo small-animal 125I-IBA-CP SPECT imaging and biodistribution studies were conducted on mice bearing HER2-positive, HER2-negative, or epidermal growth factor receptor (EGFR)-positive tumors. Nonradioactive IBA-CP and the EGFR inhibitor erlotinib were used as blocking agents to investigate the binding specificity and selectivity of 125/131I-IBA-CP toward HER2 in vitro and in vivo. Additionally, 125/131I-ICP was prepared by direct radioiodination of CP724,714 for comparison with 125/131I-IBA-CP. Results: IBA-CP displayed superior in vitro inhibitory activity (half-maximal inhibitory concentration, 16 nM) and selectivity for HER2 over 6 other cancer-related tyrosine kinases. 125/131I-IBA-CP was prepared in a typical radiochemical yield of about 65% (decay-corrected), radiochemical purity of more than 98%, and molar activity of 42 GBq/μmol at the end of synthesis. SPECT imaging revealed significantly higher uptake of 125I-IBA-CP than of 125I-ICP in the HER2-positive MDA-MB-453 tumors. Uptake in the HER2-negative MCF-7 tumors was much lower. Binding of 125I-IBA-CP in the MDA-MB-453 tumors was blocked by coinjection with an excess amount of IBA-CP, but not by erlotinib. Conclusion: The radiolabeled HER2-selective inhibitor 125/131I-IBA-CP is a promising probe for in vivo detection of HER2-positive tumors.

Dataset Information

Z3, a novel Jak2 tyrosine kinase small-molecule inhibitor that suppresses Jak2-mediated pathologic cell growth.

Publications

Z3, a novel Jak2 tyrosine kinase small-molecule inhibitor that suppresses Jak2-mediated pathologic cell growth.

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