Therapeutic targeting of fibroblast growth factor receptor kinase activity delays the outgrowth of established pulmonary tumors. (A) Metastatic D2.A1 cells were grown under three-dimensional organotypic conditions for 4 days and not stimulated (NS) or pretreated with fibroblast growth factor receptor (FGFR) kinase inhibitor PD173074 (PD173) or BGJ398 (BGJ) for 6 hours prior to being not stimulated (ns) or stimulated with FGF2 for 30 minutes, at which point the cells were analyzed by immunoblotting for phosphorylated and total extracellular signal-regulated kinases 1 and 2 (pErk1/2 and tErk1/2, respectively). (B) D2.A1 tumor organoids were established for 4 days under three-dimensional culture conditions, at which point the tumor organoids were treated with BGJ398 (1 μM) or PF271 (1 μM). Data are the bioluminescence values normalized to the plated value and are the mean (±SE) of two independent experiments completed in triplicate, resulting in the indicated P values. Inset: Photomicrographs (100x magnification) of the D2.A1 three-dimensional tumor organoids 4 days after initiation of treatment with the indicated inhibitors. (C) D2.A1 cells were injected into the lateral tail vein of female BALB/c mice and allowed to establish pulmonary tumors for 7 days, at which point the mice were randomized and split into the three cohorts that received vehicle, BGJ398 or PF271 (50 mg/kg) daily via oral gavage (arrow indicates treatment initiation). Pulmonary tumor outgrowth was monitored by bioluminescence at the indicated time points (n = 5 mice per group). Bioluminescent images and ex vivo photomicrographs show the lungs from representative mice in each treatment group. Data are the mean (±SE) pulmonary bioluminescence values at the indicated time points relative to the injected value (% of D0), *P<0.05.