RESPONSIVENESS OF BONE-MARROW ERYTHROID PROGENITORS (CFU-E AND BFU-E) TO RECOMBINANT-HUMAN-ERYTHROPOIETIN (RH-EP) INVITRO IN MULTIPLE-MYELOMA

The responsiveness of bone marrow erythroid progenitors (CFU-E and BFU-E) to recombinant human erythropoietin (rh-Hp) was investigated in vitro in 21 patients with multiple myeloma to assess the clinical usefulness of rh-Ep in this disease. CFU-E and BFU-E assays were performed by methylcellulose culture methods. The myeloma patients were divided into two groups according to the percentage of plasma cells in the bone marrow (over 50% and under 50%). Among the patients with few plasma cells, some revealed normal CFU-E and BFU-E growth at 2 units of rh-Ep, and no further increase was observed even with an increasing dose of rh-Ep. Among the other patients, more than half demonstrated a good response to rh-Ep. Among the patients with a high percentage of plasma cells, some revealed no response to rh-Ep, but there were patients with a high percentage of plasma cells in the bone marrow who had a good response to rh-Ep. High doses of rh-Ep may be clinically effective in some patients with multiple myeloma independently of the level of plasma cells in the bone marrow.