Uptake of radiolabelled modified fragment of human alfa-fetoptrotein by experimental mammary adenocarcinoma: in vitro and in vivo studies.
BACKGROUND
The aim of the study was to examine in vitro and in vivo binding of radiolabelled analogues of P149 peptide by experimental mammary adenocarcinoma with the intention of potential application for diagnosis and internal radiotherapy of tumours.


METHODS
The 36-amino acid peptide (P149-QY) of 90% homology to 447-480 peptide fragment of hAFP was synthesised and radiolabelled with iodine-125. The biodistribution of P149-Q[125I]-Y was studied in experimental mammary tumours. For in vitro experiments, extract from mouse mammary tumours were prepared and incubated with radioiodinated P149-QY peptide in the presence of a cross-linking reagent.


RESULTS
The gel electrophoresis analysis (SDS-PAGE) showed that radioiodinated P149-QY peptide formed a complex with adenocarcinoma proteins of about 30 kDa. The biodistribution of P149-Q[125I]-Y studied in experimental mammary tumours revealed a higher pharmacokinetic rate in comparison with the whole radioiodinated AFP molecule. A moderate uptake of P149-Q[125I]-Y in the tumour tissue was observed (3.2% ID/g at 30-min p.i.v). However, a faster radioactivity clearance from blood and normal tissues resulted in an increase in the tumour/muscle (T/M) ratio, i.e. from 2.3 to 3.4 after 30 mins and 24 h p.i.v, respectively.


CONCLUSIONS
The present study shows that radioiodinated P149-QY peptide reveals some positive features as the AFP receptor radioligand, however, some additional structural modifications of the initial peptide molecule are necessary for full retention of the ligand-receptor interaction of its radiolabelled forms.
Department of Radiopharmaceuticals, National Institute of Public Health, Warsaw, Poland.
Piotr
P
Garnuszek
Rafał
R
Wiercioch
Helena
H
Sztajer
Urszula
U
Karczmarczyk
Marek
M
Mirowski
D000230:Adenocarcinoma / Q000473:pathology*; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics*; D008325:Mammary Neoplasms, Experimental / Q000473:pathology*; D051379:Mice; D010455:Peptides / Q000737:chemistry; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D013997:Time Factors; D014018:Tissue Distribution; D000509:alpha-Fetoproteins / Q000493:pharmacokinetics*
D003432:Cross-Linking Reagents; D007457:Iodine Radioisotopes; D010455:Peptides; D019275:Radiopharmaceuticals; D000509:alpha-Fetoproteins