Recently,
low-molecular-weight B-cell growth factor (
LMW-BCGF) has been reported to stimulate growth of leukemic cells from B-cell precursor-
acute lymphoblastic leukemia (BCP-ALL). We further investigated the effects of
LMW-BCGF on proliferation of leukemic clonogenic (progenitor) and nonclonogenic (progeny) cells from children with BCP-ALL (28 patients) and B-cell ALL (two patients). Patients were either at diagnosis (n = 18) or in relapse (n = 12). Response of leukemic progenitor cells was determined by culturing cells (10(5) cells/mL) in
methylcellulose with 0.1 U/mL
LMW-BCGF. Colonies (greater than 20 cells) were counted at day 7. The response of the leukemic progeny population was determined by
DNA synthesis studies using tritiated-
thymidine and by
DNA quantitation with propidiumiodide for determination of cell-cycle status.
LMW-BCGF supported growth of leukemic progenitor cells from 20 of 28 (71%) BCP-ALL and two of two B-cell ALL patients. Colony numbers ranged from 7 to 2,400 (mean 145, median 45). A dose-response effect in colony growth was noted, with an apparent plateau at approximately 2.0 U/mL
LMW-BCGF. Colony cells were primarily of leukemic phenotype (CD19+/CD10+/-).
LMW-BCGF also induced significant increases in leukemic progeny cell proliferation as measured by both
thymidine incorporation (stimulation indexes of 1.6 to 34) and by cell-cycle assay (percentage S+ G2/M stimulation indexes of 1.6 to 6).
LMW-BCGF was more effective in stimulating leukemic proliferation than three recombinant
interleukins (rIL-2, rIL-3, rIL-4), although rIL-3 was able to support colony growth in 4 of 11 patients. These results indicate that
LMW-BCGF and, to a lesser degree rIL-3, are able to stimulate proliferation of BCP-ALL progenitor and progeny cells, whereas rIL-2 and rIL-4 do not support progenitor cell proliferation and have only marginal effects on leukemic progeny cell proliferation.