Figure 4 TRIB3 is induced through the PERK/ATF4/CHOP pathway of the unfolded protein response. (a) mRNA abundance of the specific genes targeted by the specific siRNAs (mean + standard deviation (SD; n = 3). (b) Fold induction of TRIB3 expression (mean + SD) after anoxia (< 0.01% O2) in MCF7 cells with knockdown of scrambled control (SCR), HIF1, PERK, ATF6, IRE1, ATF4 or CHOP gene by siRNAs. *Significantly different from control (SCR) under anoxia, P < 0.01, each measurement was performed in triplicate.