TPA-induced Mcl-1 stabilization is associated with increased resistance to various chemotherapeutic agents in BL41-3 cells.

<p><b>A:</b> BL41-3 cells were incubated in the absence or presence of TPA (5 nM) for 0.5 hours, followed by the addition of the indicated concentrations of etoposide. After 6 hours, PARP cleavage, Mcl-1 expression, and Thr 163 phosphorylation were assayed (ChemiDoc), where the values for PARP Cleavage (%) and the Decrease in Mcl-1 Expression (%) are indicated below the respective blots. <b>B:</b> BL41-3 cells were incubated in the absence or presence of TPA (5 nM) for 0.5 hours prior to the addition of the indicated concentrations of vinblastine. After 6 hours, PARP cleavage and Mcl-1 expression were assayed as in Panel A. <b>C:</b> BL41-3 cells were incubated in the absence or presence of TPA (5 nM) for 0.5 hours prior to the addition of the indicated concentrations of cisplatin. After 24 hours, PARP cleavage and Mcl-1 expression were assayed as in Panel A. The blot shown is representative of 3 independent experiments. The SE of the values shown in successive lanes for PARP Cleavage was 2, 2, 5, 11, 17, 0.2, 4, 2, 3, 4, 6, and 13, respectively. The Decrease in Mcl-1 Expression was calculated relative to untreated control cells; the SE of the other values shown was 10, 12, 18, 12, 7, 9, and 11.