Fig (4) Inhibition of 17-AAG-induced beta-lactamase reporter activity in the HSE-bla HeLa cells. Cells were pretreated with the indicated concentrations of quercetin and then stimulated with 65 nM 17-AAG for 5 hours before the beta-lactamase assay was performed as described in Methods. Response Ratios were plotted for the indicated concentrations of quercetin (n=4 for each data point). The calculated IC⁵⁰ for quercetin was 5.8 µM.