LGR5 and neoplasm: We further studied the effect of Arf1 ablation in eradicating CSCs in Lgr5-CreERT2/Arf1f/f/Apcf/f (Lgr5/Arf1/Apc) mice and found that knocking down Arf1 dramatically reduced the stem cell tumor number (Lgr5/Apc: 95.8 ± 17.8; Lgr5/Arf1/Apc: 48.4 ± 18.1) (Fig. 1b, c) and significantly extended the lifespan of the Lgr5/Apc mice (Fig. 1d).