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 (Kd)] 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(beta-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 Kd, and CCK-stimulated growth was inhibited by the
CCK-B receptor antagonist (L-365,260) not the
CCK-A receptor antagonist (
L-364,718).(ABSTRACT TRUNCATED AT 250 WORDS)