Promoter activity of the pSEAP-S1Promoter construct. The pSEAP-S1Promoter vector, the positive control (pSEAP-CONTROL), and the negative control (pSEAP-BASIC) plasmids were each individually transfected into CHO (a) or HaCaT (b) cells. Culture supernatants were collected at 24, 48, and 72 h post-transfection and analyzed for alkaline phosphatase (AP) activity. Values for all samples were normalized to the 24 h pSEAP-BASIC sample which was set at 1.0. Values shown at each time point are the average of 2–3 independent experiments. Values for the 24, 48, and 72 h pSEAP-CONTROL and pSEAP-S1Promoter samples in CHO cells (a) were all statistically significant compared to the pSEAP-BASIC samples (P < 0.05). In HaCaT cells (b), only the 48 and 72 h samples achieved statistical significance