Diagnosis of fibroadenoma using radiolabeled bladder cancer specific peptide

Most tumors are believed to overexpress several receptors, and small peptides targeting these receptors were developed for diagnosis and tumor therapy during past decade. Here we report that fibroadenoma can be visualized by bladder cancer specific peptide. A 9-mer bladder cancer specific peptide, which was discovered from the phage display method, was synthesized by peptide synthesizer, and additional tyrosine was conjugated at the N-terminal for radioiodination (Y-BP). Y-BP was radiolabeled with $^{131/124}I$ using Iodogen tube. The rat treated with N-butyl-N-(4-hydroxybutyl)nitrosamine for 8 weeks was allowed to grow until large size tumor was developed under axilla. The tumor model was microPET imaged sequentially using [$^{18}F$]FDG and radioiodinated $^{124}I-Y-BP$. The tumor was excised and examined by immunostaining studies. Radioiodinated $^{124}I-Y-BP$ was purified using fast protein liquid chromatography (FPLC) in > 90% radiochemical purity. The whole tumor was well visualized by [$^{18}F$]FDG with several intense focal uptake within tumor. The tumor was also clearly seen with $^{124}I-Y-BP$ at 4 h post-injection, and to our surprise the tumor uptake of $^{124}I-Y-BP$ lasted up to three days. The tumor was diagnosed histologically as a fibroadenoma derived from mammary gland. In conclusion, the bladder cancer specific peptide showed the good potential as a new radiotracer for the detection of breast fibroadenoma.