Glycosylated insulin-like growth factor II promoted expansion of granulocyte-macrophage colony-forming cells in serum-deprived liquid cultures of human peripheral blood cells.

This report presents the results of studies investigating the effect of a glycosylated form of insulin-like growth factor II with an apparent molecular weight of 15,000 (appM(r) = 15K IGF-II) and one with a molecular weight of 7500 (M(r) = 7.5K IGF-II) on the expansion of granulocyte-macrophage colony-forming cells (GM-CFC) in human peripheral blood cells. Blood cells were enriched for GM-CFC and other CFCs, and liquid cultures of these cells were established in serum-deprived medium supplemented with either interleukin-3 (IL-3) alone (no insulin or IGF added to the medium) or with IL-3 plus M(r) = 7.5K recombinant (r) IGF-II or appM(r) = 15K IGF-II. After incubation for 3 days or 1 week, the blood cells were subcultured in plasma clots, and the number of colonies detected at 7 days (D7) and at 14 days (D14) was used to calculate the number of D7 GM-CFC and D14 GM-CFC. The number of GM-CFC in liquid cultures of blood cells incubated for 3 days with IL-3 alone was similar to the number added at day 0. By 1 week, the number of D14 GM-CFC and D7 GM-CFC had increased to 3.5 +/- 0.9-fold (p = .03) and two- to 50-fold (p = .04) of the number at day 3, respectively. There were 1.5- to six-fold more D7 GM-CFC in cultures of blood cells incubated for 1 week with IL-3 plus either 100 ng/mL M(r) = 7.5K IGF-II or 200 ng/mL appM(r) = 15K IGF-II than after incubation with IL-3 alone. appM(r) = 15K IGF-II also promoted a two-fold increase in the number of D14 GM-CFC. appM(r) = 15K IGF-II promoted a greater increase in D14 GM-CFC than incubation with IL-3 alone even for blood samples in which M(r) = 7.5K IGF-II did not promote such an increase. The results of these studies demonstrate that physiologic concentrations of appM(r) = 15K IGF-II and M(r) = 7.5K IGF-II increased the number of GM-CFC more than IL-3 alone and suggest that appM(r) = 15K IGF-II was more potent than M(r) = 7.5K IGF-II in augmenting IL-3-induced expansion of GM-CFC in serum-deprived liquid cultures of peripheral blood cells.