Imatinib treatment of mutant 32D PDGFRA cell-injected mice prolongs survival and decreases lymphadenopathy. Mice were injected with 1.2 × 10⁶ cells of indicated cell lines (32D PDGFRA wt [−imatinib/+imatinib n = 5/5], H650Q [n = 5/5], R748G [n = 5/5], and FIP1L1-PDGFRA [n = 4/5]) and treated with 62.5 mg of imatinib per kilogram body weight twice daily by oral gavage from day 5 after cell injection. One mouse was excluded because of late death on day 50 supposedly because of infection without comparable lymphadenopathy (PDGFRA wt). (A) Injected cells are susceptible to imatinib treatment, prolonging survival of mice. Kaplan-Meier plots show survival of injected mice (survival curves for PDGFRA wt overlap). Statistical significance was tested with the log-rank test. (B-C) Treatment with imatinib consistently decreases lymphadenopathy and spleen weight of 32D PDGFRA H650Q and R748G-injected mice as shown by lymph node and spleen weight. Moribund or dead mice were analyzed for spleen and lymph node weight; animals surviving for 57 days were killed and included. Statistical significance was tested with the Mann-Whitney U test. Autopsy of the 4 surviving imatinib-treated FIP1L1-PDFGRA mice showed splenomegaly in 3 of the mice, while 1 of the mice showed a normal spleen weight. Therefore, although splenomegaly did develop in some of these mice, the difference was not statistically significant.