Based on these findings, Bocchia et al. hypothesized that noninvasive cytofluorimetric measurement of CD26 in PB might be used to explore the persistence of circulating LSCs in CML patients [43]—which may prove useful to study the impact of residual LSCs on the possibility to successfully achieve TFR. This evidence concerns the gene DPP4 and chronic myelogenous leukemia, BCR-ABL1 positive.