Culen et al. in 2016 studied 31 patients with CML to see whether CD26+ LSCs could be identified and discriminated from the CD26- HSCs using fluorescence in situ hybridization (FISH) and reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. This evidence concerns the gene DPP4 and chronic myelogenous leukemia, BCR-ABL1 positive.