99mTc-labelled human serum transferrin for tumour imaging: an in vitro and in vivo study of the complex

This pilot study reports the uptake of 99mTc-transferrin by MCF7 cells and the biodistribution of the complex in mice bearing MCF7 tumours. Human serum holo-transferrin was labelled with 99mTc using pre-reduction with 2-mercaptoethanol. The uptake of the complex by MCF7 breast tumour cells, which was found to be competitively inhibited by the presence of unlabelled transferrin, reached a plateau within 30 min. Two groups of xenografted mice with small and large tumours, respectively, were injected with the complex, and the uptake was followed for up to 24 h post-administration using a dedicated gamma camera. The mean tumour uptake values, determined after dissection, in the two groups of mice were 6% (small tumours) and 1.7% (large tumours) of the injected dose per gram of tissue, with mean tumour/blood ratios of 2.7 and 1.7, respectively.