Figure 4.

Bacteria-delivered enzyme prodrug cytotoxicity assay. Calculated IC₅₀ of HCT-116 cells post-incubation with E. coli 6KO cells (over-expressing either NfsA_Ec, NfsB_Ec, MsuE, or an empty pUCX control) across a 2-fold dilution series of (A) CB1954 (25 µM to 400 µM); or (B) nitro-CBI-DEI (0.06 µM to 15 µM). Percentage cell survival at each prodrug concentration was calculated relative to an unchallenged control by CellTiter 96^® AQ_ueous One Solution Cell Proliferation Assay (Promega, Madison, WI, USA). Data are the mean of three independent experiments, each performed in duplicate; and error bars are ±1 standard deviation. ** indicates p < 0.005 and *** p < 0.001 by one-way ANOVA with Dunnett comparison of test to control.