Jp. Smith et al., IDENTIFICATION AND CHARACTERIZATION OF CCK-B GASTRIN RECEPTORS IN HUMAN PANCREATIC-CANCER CELL-LINES/, The American journal of physiology, 266(1), 1994, pp. 180000277-180000283
The gastrointestinal peptide cholecystokinin (CCK) is known to stimula
te growth of human pancreatic cancer in a receptor-mediated fashion. T
he purpose of this study was to characterize the receptor responsible
for the trophic effects of CCK in cancer cells. With the use of homoge
nates of PANC-1 human pancreatic cancer cells grown in vitro, the bind
ing characteristics and optimal conditions of radiolabeled selective C
CK-receptor antagonists ([H-3]L-365,260 and [H-3]L-364,718) were exami
ned. Specific and saturable binding was detected with [H-3]L-365,260,
and Scatchard analysis revealed that the data were consistent for a si
ngle site of binding with a binding affinity of 4.3 +/- 0.6 nM and a b
inding capacity (B-MAX) of 283 +/- 68 fmol/mg protein in log phase cel
ls. Binding was dependent on protein concentration, time, temperature,
and pH and was sensitive to Na+, K+, Mg2+, and ethylene and glycol-bi
s(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. In contrast to lo
g phase cells, B-MAX decreased by 80 and 92% in confluent and postconf
luent cultures, respectively. Subcellular fractionation studied reveal
ed that binding was in the membrane fraction. Competition experiments
indicated that L-365,260 and gastrin were more effective at displacing
the radiolabeled L-365,260 than CCK. No binding was detected with the
CCK-A antagonist [H-3]L-364,718. Assays performed with [H-3]L-365,260
on five additional human pancreatic cancer cell lines in vitro and tu
mor tissue from xenografts in nude mice also revealed specific and sat
urable binding. These results provide the first identification of a CC
K-B/gastrin receptor in human pancreatic cancer cells and tumors and e
xplain the effects of CCK on the growth of this malignancy.