Purpose: Orthotopic models of bladder cancer mimic the normal microenvironment and provide an opportunity to study new therapies for superficial bladder cancer. The use of green fluorescent protein (GFP) transduced cells provides a sensitive way of monitoring this disease. We investigated whether examining voided urine for GFP expressing cells would indicate the presence of GFP producing tumors in an orthotopic bladder tumor model in nude mice.
Materials and methods: The human bladder cancer cell lines KU-7, UM-UC-3 and UM-UC-14 were used. GFP transductants were generated after transfection with pEGFP-N3, followed by G418 selection. After the cells were inoculated in an orthotopic model of superficial bladder cancer voided urine was collected on slides weekly for 3 weeks and observed for GFP expressing cells by fluorescence microscopy. Bladder tumor imaging for GFP was performed in surgically exposed bladders to determine the tumor incidence.
Results: KU-7 GFP cells produced tumors in all 16 mice on whole bladder GFP imaging. UM-UC-3 and UM-UC-14 GFP cells produced tumors in 8 of 12 (67%) and 18 of 25 (72%) mice, respectively. The rate of GFP positive cells in spontaneously voided urine varied by cell line and increased with time but it was generally less than the rate of detection by whole bladder GFP imaging. All mice with GFP expressing cells in the urine had GFP expressing bladder tumors.
Conclusions: Examining urine for GFP expressing cells is less sensitive than imaging surgically exposed bladders but it is 100% specific.