Comparison of animal models for the evaluation of radiolabeled androgens

Biodistribution of two 18F-labeled androgens and an 124I/125I-labeled androgen were studied in five androgen receptor (prostate) animal models with or lacking sex hormone binding globulin (SHBG). As models for androgen-receptor positive ovarian cancer, xenografts of three human ovarian cancer cell lines were tested in SCID mice. SHBG in the prostate model systems significantly affects the metabolism, clearance, and distribution of the radiolabeled androgens in several tissues, but ovarian cancer animal models were disappointing.

Effect of administration route on FES uptake into MCF-7 tumors

We have observed that intraperitoneal administration of [(18)F]fluoroestradiol (FES), a radiolabeled estrogen receptor ligand, results in higher abdominal organ uptake and slower blood clearance than intravenous administration in female mice. In SCID mice bearing MCF-7 human tumors SC, IP administration resulted in tumor uptake that was only about one third that obtained with IV administration. Thus, the route of administration of a radiopharmaceutical for imaging or radiotherapy of a tumor in the abdomen, an ovarian tumor, for example, could have a profound effect on the efficiency and selectivity of delivery of the agent to the tumor.

Reactivity of p-[18F]fluorophenacyl bromide for radiolabeling of proteins and peptides

Radiolabeling of the somatostatin analog octreotide was attempted with p-[18F]fluorophenacyl bromide ([18F]FPB). Following these unsuccessful trials, the reactivity of FPB was studied using benzyl mercaptan, phenyl acetic acid, benzyl alcohol, and benzyl amine as model compounds for amino acid functional groups. Structure and purity of products, relative reactivity of FPB in competition reactions, and radiolabeling experiments are described. In addition, improvement in labeling efficiency of HSA using [18F]FPB was achieved by pretreatment with 2-iminothiolane.