Publication Date:
2011-11-18
Description:
Abstract 2589 Introduction: Acute lymphoblastic leukemia (ALL) is one of the most common malignancies in children. Pediatric cure rates for ALL have dramatically increased in recent years as intensified therapeutic regimens have been developed. However, intensified therapy is associated with a significant and increased risk of short- and long-term toxicities. In addition, patients who relapse, do not reach remission, or have certain cytogenetic abnormalities have a poor prognosis and limited treatment options. Therefore, novel and less toxic therapies are needed. Tyrosine kinases are frequently abnormally regulated in cancer cells. Mer receptor tyrosine kinase is ectopically expressed in ALL cell lines and patient samples. Inhibition of Mer expression reduces pro-survival signaling, dramatically increases the sensitivity of leukemia cells to cytotoxic agents, and significantly delays development of leukemia in a mouse model. Thus, Mer tyrosine kinase inhibitors (TKIs) are excellent candidates for targeted therapies. We report here the first small molecule selective for Mer TK (UNC569) and characterization of its biochemical and anti-tumor activities in cell culture models of ALL. Methods: UNC569 is a substituted pyrazolopyrimidine that has been developed by a structure-based design and iterative medicinal chemistry from the known Mer/C52 cocrystal structure. Inhibition of Mer kinase activity by UNC569 was determined by a microfluidic capillary electrophoresis (MCE) assay in which phosphorylated and unphosphorylated substrate peptides were separated and analyzed through a LabChip EZ Reader. Western blot analysis of phosphorylated and total Mer protein was used to determine Mer inhibition by UNC569 in 697 (B-ALL) and Jurkat (T-ALL) cell lines. UNC569-mediated anti-leukemia activity was determined by detection of metabolically active cells using MTT reagent after 48 hours of exposure and by determining colony-formation in methylcellulose medium in the presence of UNC569. To investigate interactions with standard ALL therapies, apoptotic and dead cells were identified by flow cytometric analysis of cells stained with YO-PRO-1 and propidium iodide dyes after treatment with a chemotherapeutic agent alone or in combination with UNC569. Results: UNC569 is a novel small molecule Mer TKI with potent activity against Mer kinase (IC50 = 2.9 nM). In cell-based assays, UNC569 inhibited accumulation of phospho-Mer in both 697 and Jurkat ALL cells (IC50
Print ISSN:
0006-4971
Electronic ISSN:
1528-0020
Topics:
Biology
,
Medicine
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