Anti-MUC1 aptamers: radiolabelling with (99m)Tc and biodistribution in MCF-7 tumour-bearing mice.
BACKGROUND
Aptamers previously selected against the protein core (AptA) or the tumour glycosylated (AptB) MUC1 glycoprotein have been conjugated to MAG2 and labelled with (99m)Tc, for the potential use as radiopharmaceuticals for diagnostic imaging of breast cancer.


METHODS
The conjugation was achieved in high yield using standard peptide coupling reactions between an amino modification on the aptamer and the activated carboxylic group on the ligands. The retention of the affinity of the MAG2 modified AptA for the MUC1 protein core was confirmed using a fluorescent intercalator displacement binding assay. The labelled aptamers were separated from free (99m)Tc using ultrafiltration and monitored by high-performance liquid chromatography at all stages, to ensure that only radiolabelled aptamers were produced. The biodistribution properties of the two aptamer-radionuclide conjugates were analysed in MCF-7 tumour bearing mice and compared.


RESULTS
Efficient and convenient labelling of the two aptamers with (99m)Tc was achieved as the last step of the synthesis (post-conjugation labelling). Both the aptamer-chelator conjugates had strong (99m)Tc binding properties and the resulting complexes were stable in vivo, both in terms of nuclease degradation and leaking of the metal. The radiolabelled aptamers showed a high renal clearance and a high uptake in the intestine.


CONCLUSIONS
AptA and AptB have been successfully conjugated in high yield to the ligand MAG2 and labelled with (99m)Tc. The radiolabelled aptamers showed different tumour uptake and clearance, but will require further development prior to diagnostic use.
Pieve
Chiara Da
CD
Department of Chemistry and Analytical Sciences, The Open University, Walton Hall, MK7 6AA Milton Keynes, UK.
Perkins
Alan C
AC
Missailidis
Sotiris
S
D000818:Animals; D052157:Aptamers, Nucleotide / Q000378:metabolism*; D001943:Breast Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor; D005260:Female; D005456:Fluorescent Dyes / Q000378:metabolism; D006801:Humans; D007364:Intercalating Agents / Q000378:metabolism; D007553:Isotope Labeling; D051379:Mice; D018396:Mucin-1 / Q000378:metabolism*; D015609:Organotechnetium Compounds / Q000737:chemistry*; D014018:Tissue Distribution
D052157:Aptamers, Nucleotide; D005456:Fluorescent Dyes; D007364:Intercalating Agents; D018396:Mucin-1; D015609:Organotechnetium Compounds