Induction of R18 effectively inhibits ZNF198-FGFR1–induced transformation in Ba/F3 cells in vitro and attenuates disease development in vivo. (A) R18 dimer inhibits 4ZF-conferred IL-3–independent proliferation of TonBaF cells. Cells were cultured with increasing dosages of Dox in the absence of IL-3 and counted daily. TonBaF cells inducibly expressing R18 dimer or mutant cultured in the presence of IL-3 were included as controls. (B) Inhibitory effects of R18 dimer on the IL-3 independence of 4ZF-transformed TonBaF cells. The relative cell viability was normalized to the viability of cells in the absence of Dox. (C) Inducible expression of R18 dimer attenuates tumor development in mice mediated by 4ZF-transformed TonBaF cells. (Left) Differential sizes of the spleens from each group of animals. Median values are represented by horizontal bars. Indicated P values are determined by an unpaired test. NS indicates not significant. (Right) Representative spleen examples from each group of animals.