Selective in vitro targeting of GRP and NMB receptors in human tumours with the new bombesin tracer 177Lu-AMBA
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- Waser, B., Eltschinger, V., Linder, K. et al. Eur J Nucl Med Mol Imaging (2007) 34: 95. doi:10.1007/s00259-006-0229-9
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To investigate the in vitro binding properties of a novel radiolabelled bombesin analogue, 177Lu-AMBA, in human neoplastic and non-neoplastic tissues selected for their expression of the bombesin receptor subtypes GRP-R, NMB-R and BRS-3.
In vitro receptor autoradiography was performed in cancers expressing the various bombesin receptor subtypes. The novel radioligand 177Lu-AMBA was used and compared with established bombesin radioligands such as 125I-Tyr4-bombesin and 125I-[D-Tyr6,β-Ala11,Phe13,Nle14]-bombesin(6–14). In vitro incidence of detection of each of the three bombesin receptor subtypes was evaluated in each tumour.
177Lu-AMBA identified all GRP-R-expressing tumours, such as prostatic, mammary and renal cell carcinomas as well as gastrointestinal stromal tumours. 177Lu-AMBA also identified all NMB-expressing tumours, but did not detect BRS-3-expressing tumours or BRS-3-expressing pancreatic islets. GRP-R-expressing peritumoural vessels were heavily labelled with 177Lu-AMBA. In contrast to the strongly GRP-R-positive mouse pancreas, the human pancreas was not labelled with 177Lu-AMBA unless chronic pancreatitis was diagnosed. In general, the sensitivity was slightly better with 177Lu-AMBA than with the conventional bombesin radioligands.
The present in vitro study suggests that 177Lu-AMBA may be a very useful in vivo targeting agent for GRP-R-expressing tumours, NMB-R-expressing tumours and GRP-R-expressing neoangiogenic vessels.