Tumor cells were cultured in aMEM 20% FBS, IL7, FLT3-L. Cells were harvested and immediately spun down, and resuspended in PBS. Cells were fixed with 1% formaldehyde. Formaldehyde was quenched with 0.2 M glycine for 10 min. Fixed cells were stored at -80 degrees until use. Libraries were prepared with NEBNext primer set. Fragment size was selected with AMPure beads (Beckman Coulter).