Antiproliferative effect of wogonoside in vitro and in vivo. (A) Cell growth was measured by trypan blue exclusion assay. The cell growth curve represents the effect of wogonoside at different concentrations for 5 days. (B) Primary AML cells were incubated with wogonoside (100 μM and 150 μM) for 96 hours. Viability was measured by trypan blue exclusion assay. Statistical analysis shows the percentage of viable cells relative to the controls for every patient (control cells = 100%). (C) Cells were cloned in soft agar and cultured for 21 days after wogonoside treatment of 4 days. Colonies >50 μm in diameter were counted. The images of the representative colonies shown were taken using an inverted microscope (Nikon Instruments Inc) equipped with a color camera (Nikon) at ×40 magnification (objective lenses ×4) at room temperature. Statistical analysis shows the percentage of cells that formed colonies relative to the controls (control cells = 100%). Data represent mean ± SEM from 3 independent experiments. Asterisks denote statistically significant (P < .05) differences compared with controls by one-way ANOVA. (D) Examination was performed on tumor volumes and tumor weights to evaluate the effect of wogonoside on the proliferation of U937 cells in a xenograft model. U937 cells in Matrigel (Becton Dickinson, Bedford, MA) were injected bilaterally subcutaneously into BALB/c nude mice, forming 2 tumors per mouse. When U937 cells formed palpable tumors (50-100 mm³), mice were randomized into 2 groups (n = 5 per group) and treatment was initiated. Mice were treated with solvent or wogonoside (80 mg/kg) by intraperitoneal injection every other day for 14 days total. Tumor volumes were measured on alternate days during the experimental period. Mice were euthanized after 14 days of treatment, and the tumors were excised and weighed. Results are representative of 3 independent experiments. Results represent the mean ± SEM of tumor weights. Statistical significance was determined by 2-tailed Student t tests. Asterisks denote significant (P < .05) differences relative to controls. (E) A Kaplan-Meier survival plot for AML-bearing NOD/SCID mice is shown. Mice were sublethally irradiated (2.4 Gy), and primary AML cells were injected into the tail vein 24 hours later (2-5 × 10⁶ cells per mouse, 6 mice per group). Starting the next day, mice were injected intraperitoneally with or without wogonoside (80 mg/kg) every other day for 14 days. The blank animal group, without primary cells treated with solvent, was used to evaluate survival ability. The results are representative of 2 separate experiments. Animals were observed for 60 days after cell injection. The survival curves differed significantly between the wogonoside-treated group and the control group (P < .001; log-rank test). C, control.