Effects of pentagastrin and of the somatostatin analog (SMS 201-995) on growth of CT26 in vivo adenocarcinoma of the colon.

This study was done to investigate the effects of pentagastrin and of somatostatin analog (SMS 201-995) on growth of CT26 adenocarcinoma of the colon implanted in mice. Eighty Balb C mice were inoculated subcutaneously with 100,000 cells. Four groups of 20 mice each were treated with 0.1 milliliters of saline solution every eight hours; 250 micrograms per kilogram of pentagastrin every eight hours; 100 micrograms per kilogram of SMS 201-995 every 12 hours; 250 micrograms per kilogram of pentagastrin every eight hours, plus 100 micrograms per kilogram of SMS 201-995 every 12 hours. Tumoral weight, volume and deoxyribonucleic acid (DNA) content and mean survival rates were determined for each group. Control mice had tumors weighing 1,619 +/- 179 milligrams, of 1.47 +/- 0.2 milliliters to the third power and with 12.9 +/- 1.1 milligram of DNA, at 30 days after inoculation. The mean survival rate was 42.5 days. Pentagastrin administration increased the three parameters of tumoral growth by 40 percent and reduced survival time to 29.6 days (p < 0.01), while SMS 201-995 inhibited growth by 40 percent and prolonged survival time to 48.5 days (p < 0.01). Simultaneous administration of both peptides had no effects. These data suggest that pentagastrin has a trophic effect and SMS 201-995 an inhibitory effect on CT26 adenocarcinoma in mice.