β-tan and Sal A decrease basal and TPA-induced NF-κB transcriptional activities. At 60–80% confluency, JB6P + cells were transiently co-transfected with control renilla luciferase reporter construct and AP-1 or NF-κB firefly luciferase reporter constructs and were pre-treated with the indicated concentrations of β-tan (A) or Sal A (B) for 1 h followed by TPA treatment up to 24 h. Results were standardized relative to renilla luciferase and expressed as percentage of control (Ct)-treated cells. Significance from Ct-treated condition is indicated as ** at p < 0.01 and *** at p < 0.001. Significance from TPA-control condition is indicated as †† at p < 0.01 and ††† at p < 0.001. Results are representative of two independent experiments and plotted as averages of triplicate wells (± SD).