A. Knockdown of p38 MAPK prevents induction of p75NTR by carprofen. PC-3 and DU-145 cells were transfected with non-targeting siRNA or siRNA for p38α for 72 hours. Following transfection, cells were treated with 100 μM carprofen (CAR), or DMSO vehicle control (CON) and the cell lysates used for immunoblot analysis. A875 cell lysates were used as a positive control for p75NTR expression. β-actin (β-act) was used as the loading control. B. Activation of the p38 MAPK pathway by carprofen. PC-3 and DU-145 cells were treated with 100 μM carprofen for 0 minutes, 1 minute, 5 minutes, 1 hour, 4 hours, or 8 hours. Cell lysates were prepared for immunoblot analysis using antibodies to phosphorylated p38 MAPK (P-p38). Blots for P-p38 MAPK were stripped and reprobed for total p38 MAPK.