This study deals with the growth effect of
gastrin on two xenotransplantable human gastric
carcinomas (SC-6-JCK, poorly differentiated
adenocarcinoma; and St-15,
mucinous adenocarcinoma) and on one colonic
carcinoma (Co-3, well-differentiated adenocarcinoma). In SC-6-JCK, the treatment with s.c. injection of
pentagastrin at a dose of 10 micrograms/mouse once daily for 25 days promoted the growth of the
tumor transplanted in nude mice, but
gastrin had no effect at all on St-15 and Co-3. In SC-6-JCK, the weight, size, and labeling index of [3H]
thymidine of the
tumor were significantly increased in comparison with those of the control (p less than 0.05). In SC-6-JCK, cyclic
adenosine 3':5'-monophosphate (cAMP) in the
tumor was increased by a single i.p. injection of
pentagastrin at a dose of 20 micrograms/mouse in nude mice, but such an increase was not observed in St-15 and Co-3. Cyclic
guanosine 3':5'-monophosphate in SC-6-JCK was slightly increased by
gastrin treatment but was not affected in the other
tumors. In SC-6-JCK, at 30 min after
gastrin treatment when cAMP showed a maximum increase, the activity ratio of
cAMP-dependent protein kinase in the
tumor was also elevated. In vitro also,
gastrin stimulated cAMP production and
cAMP-dependent protein kinase activation. The data suggest that some human gastric
carcinomas may have receptor for
gastrin.