Fluorogenic compound activation in rVACV-colonized tumors. A) Two hours post intraperitoneal injection of FDG and FDGlcU tumor specific fluorescein dependent fluorescence was observed in the presence of LacZ- and GusA-expressing vaccinia virus GLV-1h68 respectively. In rVACV-LacZ-negative and rVACV-GusA-negative colonized tumors, only GFP fluorescence was observed (no difference in fluorescence between pre- and 120 min post fluorogenic compound injection). B) Fluorescence immunohistochemical analysis of GLV-1h68, rVACV-GusA-negative and rVACV-LacZ-negative colonized tumors. Blue - Hoechst 33342 stained DNA, green - virus encoded GFP, yellow - beta-galactosidase, red - beta-glucuronidase. C) Tumor specific fluorescence over time post FDGlcU-injection (n = 4; average plus standard deviation is shown).