Detection of BrdU in the regenerating bone marrow cells of a patient with AML

A patient with acute myeloid leukemia received bromodeoxyuridine (BrdU) prior to remission induction therapy. Prior to therapy only leukemic blast cells were found to be labeled. The marrow was aplastic by day 17 with the marrow cavity being devoid of BrdU labeled cells. In contrast rare BrdU containing cells were noted in the paratrabecular and endosteal regions. As the marrow recovered, many regenerating cells contained BrdU, implying that normal stem cells must have been in S-phase at the time of BrdU infusion, and repopulation of marrow may be accounted for by the activity of only a few clones in remission.