STCA activates transcription through HSEs. HeLa-luc cells (1.3 × 105 per well) stably transfected with the luciferase gene under the control of the HSP70.1 promoter containing the HSE, were exposed to STCA for 24 h in 12-well plates. (A) Luciferase activity was determined in cell lysates. The relative luminescence units (RLU) were quantified and normalised with respect to the vehicle control treatment and are expressed as the relative luciferase activity (treated/control ratio). Cells were also treated with celastrol (1.6 μ M) as a positive control. *P<0.05 relative to the vehicle treatment. (B) The levels of endogenous HSP70 were determined in a parallel experiment by western blot analysis. GAPDH served as the loading control. The data are representative from three independent experiments.