Cholecystokinin receptors and PANC-1 human pancreatic cancer cells

The gastrointestinal peptide cholecystokinin (CCK) has been shown to stimulate growth of human pancreatic adenocarcinoma in vitro and in vivo, although CCK receptors have not been identified in pancreatic cancer cells. The purpose of this study was to characterize the CCK receptors in pancreatic cancer cells and to correlate the receptor binding studies with the trophic action of CCK agonists and antagonists. With the use of homogenates of PANC-1 human pancreatic cancer cell line grown in culture, the binding of ¹²⁵I- labeled CCK octapeptide (¹²⁵I-CCK-8) was examined under various conditions to characterize the CCK receptor. Specific and saturable binding of ¹²⁵I- CCK-8 was detected in PANC-1 cells; data were consistent with a single binding site. Scatchard analysis yielded a binding affinity [dissociation constant (K(d))] of 2.8 nM and a binding capacity of 26 fmol/mg protein. Binding was dependent on protein concentration, time, temperature, the presence of protease inhibitors, and pH and was sensitive to Na⁺, K⁺, Mg²⁺, and ethylene glycolbis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid. Competition experiments indicated that L-365,260, a selective CCK-B (gastrin) receptor antagonist, was the most potent displacer of ¹²⁵I-CCK- 8, and no significant displacement of binding was found with the selective CCK-A receptor antagonist. Growth of PANC-1 cells in culture was stimulated by CCK at a concentration consistent with the K(d), and CCK-stimulated growth was inhibited by the CCK-B receptor antagonist (L-365,260) not the CCK-A receptor antagonist (L-364,718). These results provide the first evidence that CCK-stimulated growth of human pancreatic cancer is receptor mediated and that the CCK receptors responsible for growth of PANC-1 human pancreatic cancer cells appear to be of the CCK-B (gastrin) type.