Screening of 14C-polyamines in the AT3B-1 rat prostate tumor model: the search for a new PET prostate imaging agent

We have previously reported the polyamine uptake kinetics in various prostate and non-prostate cancer cell lines, concluding that the prostate cancer cell lines took up and accumulated polyamines at higher levels than non-prostate cell lines, with a view to their use as PET agents. The objective of the present study was to assess their in vivo accumulation in a rat prostate tumor model.

A comparative biodistribution study of the polyamines was conducted in AT3B-1 prostate tumors in male Copenhagen rats to determine which of the polyamines show preferential accumulation in the tumor. Tissue samples were collected one hour post administration of the polyamines (i.v.), and the radioactivity of the samples was measured by first combusting the tissue samples in a biological oxidizer and then assaying the trapped 14CO2 in a liquid scintillation counter.

Putrescine exhibited the highest tumor accumulation followed by ornithine (4.1% and 1.8% of injected dose/g of the tumor respectively). The tumor-to-blood ratio was highest with putrescine followed by spermidine (18.7 and 12.9 respectively) and the order of tumor-to-normal prostate accumulation ratio was putrescine>ornithine>spermine>spermidine.

The results indicated preferential accumulation of putrescine and ornithine in the prostate tumor.