ChemBioChem 2012-01-23

Synthesis and evaluation of a fluorescent non-peptidic cholecystokinin-B/gastrin receptor specific antagonist for cancer cell imaging.

Saroj Kumari, Joyita Chowdhury, Anil K Mishra, Sudhir Chandna, Daman Saluja, Madhu Chopra

Index: ChemBioChem. 13 , 282-292, (2012)

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Abstract

Fluorescent labeling has enabled a better understanding of the relationships between receptor location, function, and life cycle. Each of these perspectives contributes new insights into drug action, particularly for G protein-coupled receptors (GPCRs). The aim of this study was to develop a fluorescein derivative, FLUO-QUIN-a novel antagonist of the cholecystokinin-B/gastrin receptor. A radioligand-binding experiment revealed an IC(50) of 4.79 nm, and the antagonist inhibited gastric acid secretion in an isolated lumen-perfused mouse stomach assay (up to 51 % at 100 nm). The fluorescence properties altered upon binding to the receptor, and the fluorophore was quenched to a greater extent when free than in the bound form. FLUO-QUIN specifically bound to human pancreatic carcinoma cells, MiaPaca-2, which are known to express the receptor, as evidenced by rapid clustering followed by time-dependent receptor internalization. This proves the stability of FLUO-QUIN and its ability to penetrate vesicular membranes and reach various cell targets. Hence it might be used as an agent for the detection of CCK-B-receptor-positive tumors by fluorescence imaging.Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.