Inhibition of the UCI-107 human ovarian carcinoma cell line by a targeted cytotoxic analog of somatostatin, AN-238

BACKGROUND. Cytotoxic analogs of somatostatin (SST), such as AN-238, which consists of 2-pyrrolinodoxorubicin (AN-201) linked to the SST carrier RC-12 1, can be targeted to tumors that express SST receptors. Because SST recept ors are present in ovarian carcinoma cells, the authors evaluated the effec t of AN-238 on the UCI-107 ovarian carcinoma cell line. METHODS. An analysis of microsatellite alleles in cocultured SST receptor p ositive and receptor negative cells was used for the demonstration of in vi tro targeting. The toxicity and antitumor effects of AN-238 in nude mice be aring UCI-107 human ovarian tumors were investigated with or without pharma cologic inhibition of serum carboxylesterases (CE). The expression of SST r eceptor subtypes was determined by reverse transcriptase-polymerase chain r eaction analysis, and the binding affinity of AN-238 to SST receptors was d etermined by radioligand assays. RESULTS. The proliferation of SST receptor positive UCI-107 cells in vitro was inhibited preferentially by AN-238. AN-238 showed high-affinity binding to UCI-107 tumor membranes at a 50% inhibition concentration of 3.39 nM +/ - 0.74 nM. In vivo, the volume and weights of UCI-107 tumors treated with A N-238 were decreased by more than 60% (P < 0.05) compared with controls. Cy totoxic radical AN-201 or the unconjugated mixture of AN-201 with carrier R C-121 had no significant effects on tumors and were toxic. In mice with inh ibited serum CE activity, AN-201 at 400 nmol/kg was lethal, whereas AN-238 at a total dose of 800 nmol/kg caused only 22% mortality and reduced tumor weight by 69% and volume by 70% (P < 0.05 vs. control). CONCLUSIONS. Targeted chemotherapy with the SST conjugate AN-238 inhibits S ST receptor positive experimental ovarian tumors. AN-238 may provide a new treatment modality for patients with advanced ovarian carcinoma. (C) 2001 A merican Cancer Society.