Fig. 1. Effect of TPA and Pra-B on the viability of HeLa and SiHa cells. (A) The structure of praeruptorin B (Pra-B). (B) HeLa and SiHa cells were treated with Pra-B (0, 5, 10, 20, 40 and 60 μM) for 24 h, and cell viability was assessed using the MTT assay. (C) HeLa and SiHa cells were pretreated with TPA (50 ng/ml) for 2 h and then incubated with Pra-B (5, 10 and 20 μM) for 24 h. These results are representative of three independent experiments. The values shown are the mean ± SE. ** P<0.01 compared with untreated cells.