Figure 4

Parthenolide induces intrinsic apoptosis through up-regulating PMAIP1 expression and down-regulating MCL1 level in a dose-dependent (A) and a time-dependent (B) manner, and knockdown of TNFRSF10B by siRNA decreases parthenolide–induced apoptosis (C, D and E). The indicated cells were treated with indicated concentrations of PTL for 24 hrs (A) or treated with 20 μmol/L PTL for various lengths of time and harvested for Western blot analysis (B). A549 (C, D) and H1299 (C, E) cells were seeded in 6-well plates and on the second day transfected with control or PMAIP1 siRNA. A549 cells were treated with 20 μmol/L PTL while H1299 cells with 10 μmol/L for 24 hours after 48hs of transfection and harvested for Western blot analysis (C) or for detection of apoptotic cells using Annexin V/PI staining (D, E). Points:mean of three replicate determinations; bars: S.D. P value < 0.05.