FIG. 9.

MPO RNA levels in 32D-derived cells. The levels of MPO RNA, a marker of differentiation, were measured in the indicated cell lines. The MPO RNA levels are expressed as percentage of values in the same cell lines growing in IL-3-supplemented medium. The cell lines designated 32D IGF-IR and 32D IGF-IR/DNStat3 have been described in the previous figures. 32D IGF-IR Id2 cells are two mixed populations of 32D IGF-IR cells stably overexpressing Id2 (see Materials and Methods for the retroviral vector used). (A) MPO RNA levels in 32D IGF-IR and 32D IGF-IR/DNStat3 cells at 72 h after shifting from IL-3 to IGF-I. (B) Survival of 32D IGF-IR and 32D IGF-IR Id2 cell lines at 72 h after shifting from IL-3 to IGF-I (expressed as the percent decrease or increase over the plated number). The inset shows expression of Id2 protein in the parental cell lines (lane 1) and in the two mixed populations transduced with the Id2 retroviral vector (lanes 2 and 3). (C) MPO RNA levels in 32D IGF-IR and 32D IGF-IR Id2 cells, growing for 24 h in either IL-3 or IGF-I. The Northern blots give two distinct populations of 32D IGF-IR Id2 cells, selected separately at different times. Amounts of RNA in each lane were monitored with rRNA.