Responsiveness of the hamster pancreatic cancer to treatment with microcapsules of D-Trp-6-LH-RH and somatostatin analog RC-160. Histological evidence of improvement.

The effect of treatment with D-Trp-6-LH-RH, an agonist of luteinizing hormone-releasing hormone (LHRH), and somatostatin analog RC-160 was studied in male Syrian hamsters with N-nitrosobis(2-oxopropyl)amine (BOP)-induced pancreatic carcinoma. The peptides were administered periodically in long-acting microcapsule formulations designed to release controlled doses and maintain continuous blood levels of these analogs. The treatment lasted 60 d. Eighteen wk after administration of BOP, 80% of the animals developed ductal pancreatic adenocarcinomas, typically in multinodular form. Treatment with D-Trp-6-LH-RH resulted in a significant decrease in the tumorous pancreatic weight, and, in 35% of the specimens, changes indicative of histological regression were seen. Similarly, regressive alterations in the tumorous epithelium could be observed in 28% of the tumors in the RC-160 treated group. This regression was not accompanied by accumulation of lymphoid cells and only the epithelial components of the tumors were involved. These data indicate that the analogs D-Trp-6-LH-RH and RC-160 exert antitumoral effects on the experimentally-induced pancreatic cancer. It is unlikely that immunological mechanisms are involved in this response. These inhibitory effects on tumor growth could be mediated by creating a state of sex hormone deprivation of D-Trp-6-LH-RH and by inhibition of the release and/or action of gastrointestinal hormones and growth factors by the somatostatin analog RC-160.