(A) Expression of both isoforms of OB-R in two patients newly diagnosed with APL and one patient with recurrent APL compared with expression in normal bone marrow (NBM), FACS-sorted normal myeloid progenitors, peripheral blood (PB), and MO7E cells (as positive control). In one APL sample (lane 3) OB-R expression was detected in peripheral blood containing 37% promyelocytes. (B) OB-R expression of FACS-sorted CD34⁺33⁻ and CD34⁻33⁺ APL cells in complete remission (CR). OB-R was identified only in the CD34⁺compartment of NBM. In contrast, in a sample from a patient with newly diagnosed APL containing 90% promyelocytes and no CD34⁺cells, the level of OB-R expression corresponded to that seen in NBM, which was used as a control.