Bortezomib induces global DNA hypomethylation in vitro and in vivo. (A) Global DNA methylation was found to be decreased in MV4-11 cells treated in vitro with 20 nM bortezomib for 24 hours. (B,C) Global DNA hypomethylation was promoted in tumors from MV4-11(B) or K562 (C) xenograft mice following treatment with a single dose (2 mg/kg) of bortezomib (intravenous bolus). DNA (500 ng) was hydrolyzed and subjected to LC-MS/MS assay. Error bars represent SD.