In vitro activity: In HEK-293 cells, GSK-J1 inhibits the activities of transiently transfected JMJD3 and UTX. GSK-J1 also inhibits TNF-α production by human primary macrophages by increasing total nuclear H3K27me3 levels. In MC3T3-E1 cells, GSK-J1 suppresses Runx2 and Osterix expressions and ALP activity, and increases the global levels of H3K27me3.

Kinase Assay: purified JmjD3 (1 μM) and UTX (3 μM) is incubated with 10 μM peptide [BiotinKAPRKQLATKAARK(me3 )SAPATGG] in 50 mM HEPES pH 7.5, 150 mM KCl, 50 μM (NH4)2SO4·FeSO4·H2O, 1 mM 2-oxoglutarate, and 2 mM ascorbate (JmjD3, 3 minutes at 25°C; UTX, 20 minutes at 25°C) with various concentration of the inhibitor (0, 0.005, 0.01, 0.02, 0.05, 0.1 μM). 10 mM EDTA is added to stop the reaction. The reaction is desalted by zip tip and spotted on a MALDI plate with α-cyano-4-hydroxycinnamic acid MALDI matrix. Samples are analysed on a MALDI-TOF R system.

Cell Assay: Interestingly, the relative selectivity of JIB-04 toward KDM5B over KDM5C in vitro translates to a ~10-50-fold greater growth-inhibitory activity against breast cancer cell lines.