A reversible, cell-permeable inhibitor of JARID1 family demethylases (IC50s = 6, 3, 4.9, and 28 μM for JARID1A, JARID1B, JARID1C, and JARID1D, respectively); increases trimethylation of H3K4 in HeLa cells and blocks the proliferation of tumor cells expressing high levels of JARID1B