EREG mRNA expression in U87 cells is independent of IRE1 RNAse activity and of XBP1. (a) Kinetic analysis of the expression of EREG transcripts by U87Ctrl, U87dn and U87Δ899 cells with or without tunicamycin (Tun). qPCR values were presented as fold-increase relative to the reference value obtained in U87Ctrl cells at the beginning of the experiment (t = 0). HPRT1 was used as the internal standard and values are represented as the mean of triplicate experiments ± SD. (b) siRNA knockdown experiments. mRNA expression of XBP1 and EREG in XBP1 siRNA-transfected (si XBP1), nontarget siRNA-transfected cells (si Ctrl) or in untransfected U87wt cells (− si). After transfection, U87wt cells were incubated for 6 h with or without 10 μg/ml tunicamycin. Presence of mRNA was monitored by qPCR. Results were expressed as fold-change relative to untransfected U87 cells without tunicamycin and were normalized using HPRT1 mRNA detection.