A Human GRPr-Transfected Ace-1 Canine Prostate Cancer Model in Mice

作者：Ding Haiming; Kothandaraman Shankaran; Gong Li; Williams Michelle M; Dirksen Wessel P; Rosol Thomas J; Tweedle Michael F^*

来源：Prostate, 2016, 76(9): 783-795.

DOI：10.1002/pros.23172

• NIRF imaging
• GRP
• bombesin
• canine prostate cancer

BACKGROUND. A versatile drug screening system was developed to simplify early targeted drug discovery in mice and then translate readily from mice to a dog prostate cancer model that more fully replicates the features of human prostate cancer.
METHODS. We stably transfected human cDNA of the GRPr bombesin (BBN) receptor subtype to canine Ace-1 prostate cancer cells (Ace-1(huGRPr)). Expression was examined by I-125-Tyr(4)-BBN competition, calcium stimulation assay, and fluorescent microscopy. A dual tumor nude mouse xenograft model was developed from Ace-1(CMV) (vector transfected Ace-1) and Ace-1(huGRPr) cells. The model was used to explore the in vivo behavior of two new IRDye800-labeled GRPr binding optical imaging agents: 800-G-Abz4-t-BBN, from a GRPr agonist peptide, and 800-G-Abz4-STAT, from a GRPr antagonist peptide, by imaging the tumor mice and dissected organs.
RESULTS. Both agents bound Ace-1(huGRPr) and PC-3, a known GRPr-expressing human prostate cancer cell line, with 4-13nM IC50 against I-125-Tyr(4)-BBN, but did not bind Ace-1(CMV) cells (vector transfected). Binding was blocked by bombesin. Ca2+ activation assays demonstrated that Ace-1(huGPRr) expressed biologically active GRPr. Both Ace-1 cell lines grew in the flanks of 100% of the nude mice and formed tumors of similar to 0.5 cm diameter in 1 week. In vivo imaging of the mice at 800nm emission showed GRPr+: GRPr- tumor signal brighter by a factor of two at 24 h post IV administration of 10 nmol of the imaging agents. Blood retention (4-8% ID at 1 h) was greater by a factor >10 and cumulative urine accumulation (28-30% at 4 h) was less by a factor 2 compared to a radioactive analog of the t-BBN containing agent, (177)LuAMBA, probably due to binding to blood albumin, which we confirmed in a mouse serum assay.
CONCLUSIONS. The dual tumor Ace-1(CMV)/Ace-1(huGRPr) model system provides a rapid test of specific to nonspecific binding of new GRPr avid agents in a model that will extend logically to the known Ace-1 orthotopic canine prostate cancer model.

• 出版日期2016-6-15