Immortalization ex vivo and increased oncogenic potential through CFC assays of MLL edited acute leukemia cells. CFC assays were performed to assess the replating efficiency of leukemic cells ex vivo in semisolid medium. Scale bars define 100 µm. (A) Images show representative morphologies of compact colonies displaying increased density after each replating. (B) Bar graph represents the mean number of colonies generated per 10⁴ seeded cells. (C) Plot indicates cell numbers after each replating. Pooled data from 3 independent experiments. (D) Representative morphologies and phenotypes (E) are shown for colony-forming cells. Scale bar defines 10 µm. (F) Representative qPCR analyses of MLL target genes show increasing levels after each replating in CFC assays. Results from 1 of 3 independent experiments performed in triplicate. (G) Kaplan-Meier plot is shown for each cohort of animals (direct inject = 4 and secondary inject = 4). *P < .05 was considered statistically significant. Error bars indicate SEM. CFU, colony-forming unit; R, round.