Figure 4.

(A) PERK activation by Grp78 under stress condition lead to the phosphorylation of eIF2α, which activates the translation of the transcription factor ATF4, which in turn regulates gene expression in response to environmental stresses; p38 MAPK activation induces growth arrest and tumor cell dormancy through the activation of PERK and also through the suppression of ERK signaling. (B) Western blot analyses of Grp78, Grp94, GADD34, ATF4, and phospho-p38 MAPK expression in TMZ-S versus TMZ-LTT Hs683 cells and in TMZ-S Hs683 cells treated with 100 µM TMZ for 72 hours (see the legend to Figure 3). Tubulin was used as a quality and loading control.