The antitumor activity of the somatostatin structural derivative (TT-232) on different human tumor xenografts.

A somatostatin structural derivative (TT-232) has been developed in our laboratory with strong antiproliferative effect but no GH- release inhibitory activity. TT-232 inhibited tyrosine kinase activity of tumor cell lines and this inhibition correlated well with the inhibition of cell proliferation. The antineoplastic activity of TT-232 has been found to be associated with induction of programmed cell death (apoptosis) in tumor cell, resulting in highly selective elimination of neoplastic tissue. The aim of this study was the therapeutic efficacy of TT-232 on different human tumor models: PC-3 prostate carcinoma, MDA-MB-231 (ER - ) and MCF-7 (ER + ) breast carcinoma, HT-29 colon carcinoma, HT-18 melanoma, HL-60 promyelocytic leukemia. We studied the therapeutic efficacy of the novel somatostatin analog, applying it for 30 days with intermittent injection once daily and for 14 days with s.c. infusion using the Alzet osmotic minipump (model 2002). The antitumor activity of TT-232 was evaluated on the basis of survival time and tumor growth inhibition. The tumor growth inhibitory effect of TT-232 on human tumor xenografts proved to be significant, resulting in 30%-80% decrease in tumor volume and in 20%-60% tumor-free animals. This antitumor efficacy of the novel somatostatin analog was observable in almost all tumors investigated. These data suggest that the novel somatostatin analog (TT-232) is an effective and promising antitumor agent.