MEK2 inhibitors and Geldanamycins interact to encourage p38 MAPK activation that is partly ROS dependent and suppressed by AKT and ERK1/2 signaling: CD95 activation after drug exposure is p38 MAPK dependent As mentioned in Figure 5A, the p38 MAPK pathway was quickly activated within 3h after mixed exposure to 17AAG and MEK1/2 inhibitor prior to total inactivation of ERK1/2 and AKT that Hedgehog pathway inhibitor occurred 6 12h after exposure, suggesting that even though activated MEK1 and activated AKT could reduce drug induced p38 MAPK activation, the activation of p38 MAPK was probably be independent of drug induced ERK1/2 and AKT inactivation. Combined expression of dominant negative AKT and dominant negative MEK1 paid down the phosphorylation of AKT and ERK1/2, but did not seriously raise the phosphorylation of p38 MAPK. Mixed expression of dominant negative MEK1 and dominant negative AKT paid down the expression of c FLIP s and BCL XL, but didn’t notably improve basal levels of cell morbidity. Appearance of dominant negative MEK1 recapitulated the results of PD184352 when it comes to enhancing 17AAG stimulated p38 MAPK phosphorylation and Digestion enhancing 17AAG stimulated eliminating. These studies argue the drug 17AAG must provide an additional indication individual from only suppressing ERK1/2 and AKT function, which can be necessary to tumefaction cell-killing and to trigger p38 MAPK activation. Preceding studies from this laboratory have shown that reactive oxygen species are a significant component of 17AAG fatal signaling, such as the activation of p38 MAPK. Exposure of hepatoma cells for the ROS quenching agent N acetyl cysteine, that suppresses ROS induction in hepatoma cells, did not significantly change the inactivation of ERK1/2 or AKT by 17AAG and MEK1/2 chemical therapy but did reduce the activation of p38 MAPK by these drugs. Exposure of hepatoma cells to the ROS quenching agent N acetyl cysteine dramatically IPA-3 paid off the lethality of MEK1/2 inhibitor therapy and 17AAG. Collectively, the info in Figure 5 argues that lack of ERK1/2 and AKT function and gain of p38 MAPK function play important roles in the actions of 17AAG and MEK1/2 chemical therapy in hepatoma cells. Based on our data in Figure 5A, which demonstrated that p38 MAPK was fast activated after exposure to 17AAG and MEK1/2 inhibitor, we further examined whether this signaling pathway played any direct role in the extrinsic pathway following drug treatment and the regulation of CD95. Exposure of cells to PD184352 and 17AAG increased the association of professional caspase 8 with CD95 in hepatoma cells, an impact which was inhibited by expression of dominant negative p38 MAPK or by expression of dominant negative MKK6 and dominant negative MKK3. Appearance of dominant negative p38 was competent to prevent stress induced signaling in this pathway. Expression of activated MEK1 and activated AKT also suppressed 17AAG and MEK1/2 chemical induced association of professional caspase 8 with CD95.