CD26 (dipeptidylpeptidase IV) has been identified as a biomarker for the quantification and isolation of CML LSCs in the bone marrow (BM) of CML patients, as CD26+-sorted LSCs have been demonstrated to be entirely BCR-ABL1-positive at the genomic level. The gene discussed is ABL1; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.