Non-invasive imaging of GFP-luciferase labeled orthotopic prostate cancer model in nude mice using bioluminescence system

Abstract

Objective To develop preclinical orthotopic model in nude mice for sensitive prostate cancer cell tracking during tumor progression using bioluminescent technique.Methods The human prostate cancer cell line PC3 cells were transduced with green fluorescent protein (GFP) -luciferase fusion gene by a lentivirus vector which can express high activity of luciferase and GFP.Stably transduced GFP-LucPC3 monoclonal cells were got with Blasticidin selection.Labeled or normal tumor cells ( 5 × 106 ) were implanted into the flanks of 6 animals to build up an intradermal xenograft prostate cancer model,which provided prostate cancer graft to build the orthotopic prostate tumor model,and to confirm the tumorigenesis ablitiy of GFP-Luc-PC3.Tumor tissue from the either PC3 or GFP-Luc-PC3 line tumors was harvested and cut into pieces of about 2 mm3.These were grafted into the anterior prostates of 24 male animals which were randomly divided into two groups.The tumor growth was monitored by both WIS 200 and ex vivo tumor weight analysis 2,4,6 and 8 weeks after tumor tissue grafting.The bioluminescent signal values as well as tumor weight was measured,and their relationship was analyzed accordingly.Results A GFP-LucPC3 cell line was established which had the same growth pattern as well as tumorigenesis ability as normal PC3 cells.There was a positive linear correlation between bioluminescent signal and cell number with the coefficient factor r =0.997.In orthotopic prostate cancer model,all 12 mice in GFP-Luc-PC3 group developed prostate tumor,from which the bioluminescent signal could be recorded.In normal PC3 group,there was no significant bioluminescent signal.The bioluminescent values (photons/second) in vivo were (69.13298±2.07900) E+05,(82.66208±1.231 00) E+05,(91.94257±2.321 00) E+05 and ( 130.643 40 ± 3.247 00) E + 05 respectively 2,4,6 and 8 weeks after tumor tissue implantation.The tumor weight ex vivo was ( 9.67 ± 1.07 ),( 12.47 ± 2.12),( 16.45 ± 2.57 ),and ( 21.43 ± 4.56 ) g accordingly.There was a positive linear correlation between in vivo bioluminescent values and ex vivo tumor weight with coefficient being 0.973,P ＜0.05.Conclusion Our findings demonstrate the ability of the luciferase labeled tumor cells combinated within vivo bioluminesence imaging system is an excellent experimental animal model in tracking the location,magnitude and persistence of luciferase expression cells in human prostate cancer mouse models,which may be usful in non-invasively monitoring on progression of prostate cancer in vivo,even after the metastasis of the tumor. Key words: Prostate carcinoma; Bioluminescence; Luciferase; Transgene