No abstract

The antiproliferative effect of somatostatin-14 and its analog octreotide on in vitro pancreatic and breast tumor cells has led to the suggestion that octreotide may have further oncological indications in addition to gastroenteropancreatic tumors. To extend these in vitro observations, we evaluated the effect of octreotide in rodent models of pancreatic and breast tumors. Octreotide of 5 or 50 μg b.i.d. in nude mice bearing solid MiaPaCa pancreatic tumors (subline 21) or ZR-75-1 breast tumors induced significant inhibition of tumor growth from week 2 until the end of treatment at week 5. After 5 weeks the mean volume of ZR-75-1 tumors in animals treated with the 50-μg regimen was 48% that of control. Autoradiographic studies showed a high percentage (71 %) of ZR-75-1 tumors to be somatostatin receptor-positive. In addition, the growth of ZR-75-1 cells in vitro was significantly inhibited by octreotide. The drug was also tested in a second breast cancer model, DMBA-induced mammary tumors in rats, and continuous administration of 10 μg/kg/h over 6 weeks led to an approximately 50% reduction in the number of tumors arising in the rat mammary gland. These data suggest that pancreatic and breast cancer may be among the malignant diseases clinically susceptible to octreotide.