Recombinant human interleukin-3 and recombinant human granulocyte-macrophage colony-stimulating factor administered in vivo after high-dose cyclophosphamide cancer chemotherapy: effect on hematopoiesis and microenvironment in human bone marrow.

The effects on bone marrow (BM) cell proliferation and differentiation of recombinant human interleukin-3 (rhIL-3) and recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) administered after high-dose (7 g/m2/d) cyclophosphamide (HD-CTX) chemotherapy were studied in nine patients with malignancies without BM involvement and in three control patients. rhIL-3 at a dose of 1 to 5 micrograms/kg/day was administered for 14 to 18 days by continuous intravenous (i.v.) infusion and rhGM-CSF was administered at a dose of 5.5 micrograms/kg/day for 14 days. Changes induced by cytokine treatment were assessed by morphoimmunohistochemical analysis of BM biopsies. Comparison was made in the cytokine-treated groups and with control patients who received HD-CTX alone. BM cellularity and the myeloid/erythroid (ME) ratio were lower in rhIL-3-treated than in rhGM-CSF-treated patients, but in both groups it was significantly higher than in the controls. The proportion of BM cells stained by PC10, a monoclonal antibody (MoAb) recognizing a proliferation-associated nuclear protein (PCNA), increased from 6.78% to 21.18% (P less than .02) after rhIL-3, and from 5% to 35.33% (P less than .001) after rhGM-CSF; no increase was observed in the control group. The frequency of CD34+ BM cells was unchanged after rhIL-3 (P = NS) and decreased after rhGM-CSF (P less than .001). In both groups, most of the PC10+ cells were represented by promyelocytes and myelocytes with no increase in blast cell numbers. rhIL-3-treated BM showed an increased number of megakaryocytes and increased proliferative activity of erythroid cells as compared with rhGM-CSF cases. BM stroma changes observed in both treated groups included endothelial cell proliferation, increased BM macrophage concentration, and increase in BM fibroblasts as detected with an anti-nerve growth factor receptor antibody. In most rhIL-3-treated cases, BM fibrosis developed after treatment. The same effect was not observed in rhGM-CSF patients.