Loss of Cdc42 disrupts maintenance of the fully transformed MA9 leukemia. MA9 leukemia cells were harvested from diseased animals in the vehicle control group (Cdc42 alleles still intact) and plated in methylcellulose in the presence or absence of 4-OHT. (A) On Cdc42 deletion, MA9 cells had a reduced number of CFU-C compared with controls and (B) fewer cells per colony. (C) Cdc42 deletion from MA9 cells in secondary transplants prolonged the latency of disease (P < .002).