TABLE 1

In Vitro GRP Receptor Binding, Signaling, and Internalization Properties of Bombesin Analogs

Binding affinity (IC50 in nM)*SignalingReceptor internalization
CompoundHuman prostate cancersHEK-GRPR cellsPC3 cellsCalcium mobilization†Immunofluorescence/ELISA‡
Bombesin1.6 ± 0.21.2 ± 0.10.8 ± 0.2AgonistInternalization (EC50: 0.09 ± 0.02 nM)
Demobesin 12.6 ± 0.22.4 ± 0.52.1 ± 0.5AntagonistNo internalization Antagonizes bombesin-induced internalization
Demobesin 42.0 ± 0.52.1 ± 0.30.8 ± 0.1AgonistInternalization (EC50 = 0.20 ± 0.11 nM) Does not antagonize bombesin-induced internalization

  • ↵* Values are mean ± SEM (n ≥ 3).

  • ↵† Tested in PC3 cells and in GRPR-transfected HEK293 cells.

  • ↵‡ Tested in GRPR-transfected HEK293 cells.

  • EC50 = half-maximally effective concentration.