In vitro activity: GNF-2 causes a dose-dependent growth inhibition of the Bcr-abl–positive cell lines with IC50 values of 273 nM (K562) and 268 nM (SUP-B15). GNF-2 inhibits the growth of Ba/F3.p210E255V and Ba/F3.p185Y253H cells with IC50 values of 268 nM and 194 nM respectively. GNF-2 (1 μM) induces apoptosis of Ba/F3.p210 cells as well as Ba/F3.p210E255V cells. GNF-2 inhibits the cellular tyrosine phosphorylation of Bcr-abl in a dose-dependent manner with IC50 of 267 nM. GNF-2 (1 μM) induces a significant decrease in the levels of phospho-Stat5 in Ba/F3.p210 cells. GNF-2 binds to the myristic binding pocket of Bcr-abl. GNF-2 inhibits the kinase activity of non-myristoylated c-Abl more potently than that of myristoylated c-Abl by binding to the myristate-binding pocket in the C-lobe of the kinase domain. GNF-2 (10 μM) requires BCR and/or the c-Abl SH3 and/or SH2 domains to inhibit BCR-Abl-dependent cell proliferation. GNF-2, but not a methylated GNF-2 analog, binds c-Abl in cellular extracts derived from 3T3 fibroblasts. GNF-2 (10 μM), in a dose-dependent manner, clearly inhibits tyrosine phosphorylation of CrkII. GNF-2 inhibits the phosphorylation of CrkII in c-AblG2A-expressing cells with IC50 of 0.051 μM. GNF-2 binds in an extended conformation in the myristate pocket with the CF3-group buried at the same depth as the final two carbons of the myristate ligand. GNF-2 (10 μM) combined with imatinib (1 μM) reduces the number of resistant clones to 1 μM imatinib by at least 90%. GNF-2 inhibits the auto-phosphorylation and proliferation of BafF3 cells expressing p210Bcr–Abl and p210Bcr–Abl mutants. GNF-2 (8 nM) in combination with GNF-5 (20 nM) results in additive effects with respect to inhibition of the Abl64–515 kinase activity.

Kinase Assay: Recombinant proteins (100 nM for each construct) or immunoprecipitated proteins are diluted in kinase buffer (20 mM HEPES (pH 7.4), 50 mM KCl, 0.1% CHAPS, 30 mM MgCl2, 2 mM MnCl2, 1 mM DTT, and 1% glycerol). Aliquots of the diluted proteins are preincubated with either DMSO or compounds for 30 min at room temperature and then added to K-LISA PTK EAY reaction plates. The kinase reaction is initiated by adding 0.1 mM ATP and is allowed to proceed for 30 min at room temperature. The phosphorylation of GST-Abltide is monitored by SDS-PAGE and phosphorimaging analysis or autoradiography.

Cell Assay: Cells (0.3-0.6 × 106 per mL, Ba/F3.p210, Ba/F3.p210E255V and Ba/F3.p185Y253H cells) are plated in duplicate or triplicate in 96-well plates containing increasing GNF-2 concentrations (5 nM–10 μM). After incubation at 37 ℃ in 5% CO2 for 48 hours, the effect of GNF-2 on cell viability is determined by the MTT colorimetric dye reduction method. Inhibition of cell proliferation is calculated as a percentage of growth of DMSO-treated cells, and IC50 values are determined with Microsoft Excel XLfit3.