(A) Growth and viability in the absence of GM-CSF. TF1 parental cells, TF1-neo clones (n = 4), TF1-S clones (n = 9), and TF1-L clones (n = 8) were washed extensively and replated at 2.5 × 105 cells/mL in medium lacking GM-CSF. Daily determinations of viable cell number were performed as in Fig 3. The final plotted value is the average for all clones tested. The day 0 value was set at 100%, and represents a colorimetric determination performed 1 hour after plating. (B) Apoptosis determination using a TUNEL assay (see Materials and Methods) after 72 hours of culture in the presence (left panels) or absence (right panels) of GM-CSF. Top panels: TF1-neo; middle panels: TF1-S; bottom panels: TF1-L. Viable cells are represented in the left lower quadrant of each panel, early (live) apoptotic cells are in the right lower quadrant, and late-stage apoptotic (dead) cells are displayed in the right upper quadrant. The number in each quadrant represents the percent of events in that quadrant.
