Effects of gastrin on tumor growth and cyclic nucleotide metabolism in xenotransplantable human gastric and colonic carcinomas in nude mice.

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.