Fig. 6.

Honokiol suppresses stress-induced PLD activity in T24 bladder and Calu1 lung cancer cells. A, T24 and Calu1 cells (obtained from the American Type Culture Collection) were plated in DMEM containing 10% serum for 48 h and then shifted to either 10% serum or 0.5% serum overnight as indicated. Honokiol (20 μmol/L) or control ethanol was then added for 4 h as indicated. [³H]myristate was added with the honokiol. After 4 h, BtOH (0.7%) was added for 20 min, at which time the cells were harvested and the level of phosphatidyl-BtOH was determined as in Fig. 1. The experiments shown are representative of at least two independent experiments. B, T24 and Calu-1 cells were plated in DMEM with 10% serum for 48 h then changed to DMEM containing either 10% or 0.5% serum overnight as indicated. Honokiol (20 μmol/L) or control ethanol was then added either at the time of changing medium (24 h) or 4 h before harvesting as in Fig. 3, at which time the cells were examined for cell viability or PARP cleavage. The Western blot is representative of at least two independent experiments. The error bars for cell viability represent the SD for triplicate samples from a representative experiment repeated twice.