Is there a role for agonist gastrin-releasing peptide receptor radioligands in tumour imaging?

Gastrin-releasing peptide (GRP) has been shown to be a tumour growth stimul ating agent for a number of normal and human cancer cell lines. The tumour growth effect is a direct result of GRP binding to membrane G-protein coupl ed GRP receptors (GRP-R) on the cell surface. Available data on the role of GRP and CRP-R in human lung, prostate, breast, colorectal and gastric carc inoma are reviewed and it is suggested that radiolabelled agonists are pref erable to antagonists for imaging and therapy as they appear to be internal ised, yielding a higher target/background ratio. The use of rhenium or indi um radiolabels for therapy may provide a new approach to GRP/bombesin expre ssing tumours. ((C) 2001 Lippincott Williams & Wilkins).