PDI expression is induced in AML patients with activated UPR. (A) XBP1 mRNA spliced variant-specific PCR for negative (lanes 1-4) and positive (lanes 5-8) AML patient samples. U937 cells harvested 24 hours after ER stress induction after treatment with 3 μg/mL tunicamycin served as positive control. (B) Real-time PCR results for mRNAs of PDI, GRP78, calreticulin (CRT), CEBPA, and ABL from AML patient samples stratified according to being positive (n = 31; 25%) or negative (n = 91; 75%) for the XBP1 spliced variant as a marker for activated UPR. (C-E) Correlation between differential gene expression of PDI and GRP78 (C), of PDI and calreticulin (CRT; D), and of PDI and CEBPA mRNAs (E) in 122 AML patients.