Glucuronidase specific fluorigenic compound activation in serum of tumor bearing mice. A) Tumor bearing mice were mock injected (n = 2) or injected with GLV-1h68 (n = 6) and rVACV-GusA-negative (n = 6) respectively. Seven days later 5 μl serum was co-incubated for 1 h at 37°C with 4-MUG and FDGlcU respectively and subsequently specific fluorescence was determined. B) Retrospective serum analysis. Serum samples (n = 99) from different tumor xenograft models (GI-101A, A549, DU-145, PANC-1, HT-29) were retrospectively tested. Samples were derived from mock (n = 33) injected mice or mice treated for different periods of time (7 to 53 days) with several GusA-positive (n = 53) or -negative (n = 13) rVACV. * indicates p < 0.03; *** indicates p < 0.001.