Methods and compositions for identifying leukemic stem cells

A method of treating a subject having or diagnosed with acute lymphocytic leukemia (ALL) or lymphoid blast crisis chronic myeloid leukemia (LBC CML), comprising:

• (a) obtaining a biological cell sample from the subject;
• (b) isolating mononuclear cells from the sample of (a);
• (c) allowing the cells of (b) to take up a fluorescence substrate for the enzyme aldehyde dehydrogenase (ALDH) and labeling the cells with an anti-CD34 monoclonal antibody and an anti-CD38 monoclonal antibody;
• (d) isolating CD34+CD38− mononuclear cells from the cells of (c) using flow cytometry;
• (e) measuring the ALDH activity of the cells of (d);
• (f) comparing the levels of ALDH activity in the cells of (e) with the levels of ALDH activity in the cells of a reference sample;
• (g) identifying the cells of (f) that have an intermediate level of ALDH activity (CD34+CD38− ALDHint) in the sample from the subject when compared to the level of ALDH activity of the CD34+CD38− cells in the reference sample as being LSCs;
• (h) administering to the subject a treatment for ALL or LBC CML;
• (i) repeating steps (a) through (f);
• and
• (j) determining that the subject has completed treatment for ALL or LBC CML when the presence of LSCs is not detected.