STCA does not affect the ability of HSP90 to bind ATP. MCF7 cells (5 × 105 per dish) in 6-cm dishes were exposed to vehicle (0.1% acetonitrile) or STCA for 24 h. Control treatments were also performed with vehicle (0.1% DMSO), 1 μ M GA and 0.8 μ M celastrol (CL). Cells were lysed and subjected to ATP pulldown using ATP-agarose beads. For the ATP pulldown and input samples, the levels HSP90 and GAPDH were determined by western blot analyses. The data represent results from three independent experiments.