Expression of M-Ras G22V in an IL-3–dependent line results in factor-independent growth in the absence of IL-3, but decreased growth in its presence. (A) Parental R6-X (open symbols) or an FACS-sorted population expressing M-Ras G22V (closed symbols) were cultured in triplicate at 104/mL in medium alone (circles •, ○) or in the presence of IL-3 (2% W3) (squares ▪, □). Cells were counted at the indicated intervals and counts are shown as the mean ± SEM. (B) Parental R6-X cells or clones expressing high (clone F.3; MFI 474) or low (clone M.4; MFI 1775) levels of M-Ras G22V, or the polyclonal “sorted” population expressing high levels of M-Ras G22V cells (sorted), were plated in agar for 7 days in 2% W3 at 3 × 102 per mL. The mean ± SEM of numbers of colonies or in the case of M.4 and St, colonies and clusters, in triplicate cultures is shown under the images of representative plates of each triplicate. To visualize colonies, plates were stained with acridine orange (1 μg/mL) and the images were captured using a Canberra Packard photodocumentation system (Alpha Innotech Corp, San Leandro, CA).
