GRPR and gastrointestinal stromal tumor: During this study, it was found that, in relation to the gastrin-releasing peptide receptor (GRPR), there were high specific bindings found, both for an agonist (AMBA) with high internalization and for an antagonist (NeoBOMB1) with enhanced membrane-binding activity, across all GIST cell lines, regardless of the level of TKI resistance.