Assay Method Information

Assay Name:  Serum Binding Analysis
Description:  In order to more properly assess the binding efficacy of the compounds, radioligand binding assays were carried out in the presence of 100% human serum to more accurately reflect the in vivo environment. While observed IC50 values are typically lower than those reported for buffer binding assays, the relevance of the assay for ranking of compound efficacy is enhanced. Target compounds were tested to determine their ability to bind with CXCR7 sites on MCF-7 and/or MDA-MB-435S CXCR7 transfected cells. Efficiency-maxim/zed radioligand binding using filtration protocols as described in Dairaghi D J, et al., HHV8-encoded vMIP-I selectively engages chemokine receptor CCR5. Agonist and antagonist profiles of viral chemokines., J. Biol. Chem. 1999 Jul. 30; 274(31): 21569-74 and Gosling J, et al., Cutting edge: identification of a novel chemokine receptor that binds dendritic cell- and T cell-active chemokines including ELC, SLC, and TECK, J. Immunol. 2000 Mar. 15; 164(6):2851-6 was used.In these assays, MCF-7 and/or MDA-MB-435S cells were interrogated with the target compounds and the ability of these compounds to displace 125 I radiolabeled SDF-1 was assessed using the protocol described in Dairaghi and Gosling. The target compounds were added to the plate to the indicated concentration followed by addition of cells and radiolabeled chemokine (125I SDF-1), both in the following medium (human AB serum with 10 mM HEPES added to stabilize at pH 7.4). All assays were then incubated for 3 hrs at 4° C. with gentle agitation. Following incubation in all binding assays, reactions were aspirated onto PEI-treated GF/B glass filters (Packard) using a cell harvester (Packard) and washed twice (25 mM HEPES, 500 mM NaCl, 1 mM CaCl2, 5 mM MgCl2, adjusted to pH 7.1). Scintillant (MicroScint 10, Packard) was added to the wells, and the filters were counted in a Packard Topcount scintillation counter. Data were analyzed and plotted using GraphPad Prism (GraphPad Software).
Affinity data for this assay
 

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