Effect of antibiotic treatment on the anti-tumor activity and GI toxicity of PHY906, CPT-11 and PHY906/CPT-11(9/c) in murine Colon-38 tumor-bearing BDF1 mice. (A) Effect of PHY906 and/or CPT-11 on the growth of Colon 38 tumor cells in BDF1 mice with or without (w/o) antibiotic treatment. Each spot represents an individual tumor’s size relative to that at initial treatment. One way ANOVA was used to determine the significance of the differences between curves (B) Immunohistochemistry staining for cleaved caspase-3 in Colon-38 tumor sections under different treatment conditions as indicated on the graph. Photographs in the figure were taken at 200× magnification. (C) Quantitation of cleaved caspase-3 staining. Cleaved caspase-3 stained cell per each view of Colon-38 tumor sections following different treatment conditions as indicated on the graph. Each spot represents the mean number of heavily stained cells from 4 to 5 views of each tumor section. Student's t-test was used to determine whether differences between treatment groups were significant. Details of the experimental procedures are given in Methods.