Inhibition of growth of two human pancreatic adenocarcinomas in vivo by somatostatin analog SMS 201-995.

Somatostatin inhibits hormone secretion from gastrointestinal endocrine tumors. The purpose of this study was to determine whether SMS 201-995, a long-acting analog, would inhibit the growth of pancreatic adenocarcinomas. Two human pancreatic cancers grown in nude mice were studied: SKI, which has cholecystokinin receptors, and CAV, which does not. Tumors were implanted in groups of six mice each. Treatment groups received SMS 201-995 (100 micrograms/kg three times daily) by intraperitoneal injections and control animals received saline solution. Tumor area was measured twice weekly. After 7 weeks, the tumors and mouse pancreases were excised, weighed, and analyzed for protein and RNA and DNA content. In a second set of experiments, treatment was begun 21 days after transplantation. Mean body weights between groups were not different in any experiment. With treatment beginning on the day of transplantation, the tumor areas of SKI and CAV cancers were reduced by the third and fifth weeks of treatment, respectively. Tumor doubling times were prolonged with treatment in both SKI tumors (5 days) and CAV tumors (6 days). In the SKI treatment groups, tumor weight (52 percent), RNA content (72 percent), and DNA content (60 percent) were decreased at sacrifice compared with those of the control groups. In the CAV treatment group, the mean tumor weight (55 percent) and protein (48 percent), RNA (67 percent) and DNA contents (60 percent) were decreased compared with the CAV control group. Tumor growth of SKI and CAV cancers was also inhibited when treatment was delayed 21 days after transplantation. We conclude that these effects are not mediated by inhibition of cholecystokinin, as seen by similar inhibitory effects on both tumors. Treatment with SMS 201-995 may be an effective hormonal therapy in patients with pancreatic cancers.