Somatostatin controls Kaposi's sarcoma tumor growth through inhibition of angiogenesis

Somatostatin and its analogs are active in the inhibition of SST receptor-p ositive endocrine neoplasms, but their activity and mechanism in non endocr ine tumors is not clear. Somatostatin potently inhibited growth of a Kaposi 's sarcoma xenograft in nude mice, yet in vitro the tumor cells did not exp ress any known somatostatin receptors and were not growth inhibited by soma tostatin. Histological examination revealed limited vascularization in the somatostatin-treated tumors as compared with the controls. Somatostatin was a potent inhibitor of angiogenesis in an in vivo assay. In vitro, somatost atin inhibited endothelial cell growth and invasion. Migration of monocytes , important mediators of the angiogenic cascade, was also inhibited by soma tostatin. Both cells types expressed somatostatin receptor mRNAs. These dat a demonstrate that somatostatin is a potent antitumor angiogenesis compound directly affecting both endothelial and monocytic cells. The debated funct ion of somatostatin in tumor treatment and the design of therapeutic protoc ols should be reexamined considering these data.