In vivo activity of DHFR antagonists and corticosteroids. (A) The ability of Kasumi-1 cells to form colonies in methylcellulose with methotrexate or methylprednisolone was assessed. Both compounds inhibited colony formation compared with a vehicle control. Error bars represent SD across duplicate measurements. (B) A luciferase positive SKNO-1 orthotopic model was established in NOG mice. Mice were treated with vehicle (n = 4), dexamethasone 15 mg/kg per day intraperitoneally (n = 4), or methotrexate 5 mg/kg per day intraperitoneally (n = 3) for 4 daily doses, and tumor burden was monitored by in vivo imaging. (C) In the luciferase-positive SKNO-1 orthotopic model as above, mice were treated with vehicle (n = 7), dexamethasone (DEX) 15 mg/kg per day intraperitoneally (n = 7), or methotrexate (MTX) 5 mg/kg per day intraperitoneally (n = 7) for 8 doses, and tumor burden was monitored by in vivo imaging. Data are represented as mean ± SEM (n = 7 in each treatment arm). *P < .001 by 1-way analysis of variance (ANOVA) with Tukey posttest.