In vitro activity: GANT61 is an inhibitor for GLI1 as well as GLI2-induced transcription. GANT61 inhibits the DNA binding ability of GLI1. GANT61 inhibits hedgehog signaling with IC50 of 5 μM, displays selectivity over other pathways, such as TNF signaling/NFκB activation, glucocorticoid receptor gene transactivation, and the Ras–Raf–Mek–Mapk cascade. GANT61 efficiently inhibited in vitro tumor cell proliferation in a GLI-dependent manner. GANT61 induces apoptosis in chronic lymphocytic leukemia cells (CLL), but not in normal B lymphocytes. GANT61 induces robust cytotoxicity and abolishs the clonogenicity in human colon carcinoma cell lines. GANT61 induces inhibition of DNA replication in early S-phase in human colon carcinoma cell lines, leading to DNA damage signaling involving an ATM–Chk2 axis and induction of cell death. GANT61 (30 μM) causes growth arrest and apoptosis in acute myeloid leukemia (AML) cells.

Kinase Assay: HEK293 cells are transfected with GLI1 expression plasmid, together with the reporter plasmids 12×GliBSLuc and R-Luc on 10-cm plates (day 0). Twenty-four hours later, cells are seeded in white 96-well plates with clear bottom at a density of 15,000 cells per well. Cells are allowed to attach, and compounds are added at a final concentration of 10 μM in DMSO (0.5% final DMSO concentration) (day 1.5). Cells are grown for another 24 h, subsequently lysed, and then analyzed by using the Dual Luciferase kit.

Cell Assay: BrdU Incorporation Assay. Subconfluent cells are grown in reduced FBS (2.5%) for 48 h in the presence of 5 μM test compound (or DMSO) on white 96-well plates with clear bottom. Subsequently, cells are labeled for 2 h with BrdU, fixed, and analyzed.