Following the last dose, spleens were harvested and CD19+ leukemic cells were isolated using EasySep™ Human CD19 Positive Selection Kit II (STEMCELL, cat. # 17854). RNA was isolated from Trizol preserved cells according to manufacturer's protocol (Ambion, Life Technologies) followed by loading the ethanol-precipitated sample into an RNeasy column (RNeasy Mini Kit; QIAGEN)  and DNase digestion with an RNase-Free DNase Set (QIAGEN). RNA sequencing was performed using TruSeq Stranded mRNA Library Prep (Illumina) according to the manufacturers' protocol. 1 μg of RNA was purified, fragmented and transcribed into cDNA, then samples were indexed with TruSeq RNA CD Index Plate (cat. no 20019792) and amplified. Quantification of DNA libraries using DNA 1000 chip on an Agilent Technologies 2200 TapeStation System was performed, then DNA libraries were normalized to 4 nM and then pooled in equal volumes.