Synthesis and Antitumor Activity of Conjugates Based on the Phe-D-Trp-Lys-Thr Peptide Fragment of Somatostatin

Abstract

New somatostatin analogs containing the fragments of adamantane, coumarin, tetrahydrocarbazole, and palmitic acid of the general formula R-Phe-D-Trp-Lys(Boc)-Thr-OMe have been synthesized. The structure of the conjugates combines a peptide fragment, which has affinity for somatostatin receptors (sstr), and a nonpeptide fragment, which potentially possesses antitumor activity. Presumably, the compounds synthesized are the agonists of sstr. The amide bond between the peptide and nonpeptide fragments has been formed using the carbodiimide method and the method of activated esters. The structures of the conjugates have been confirmed by mass spectrometry (ESI⁺) and ¹H NMR spectroscopy. The antitumor activity of the conjugates has been examined by the MTT test on human lung adenocarcinoma (A549), human prostate adenocarcinoma (PC3), human colon cancer (HCT-116), human breast cancer (MCF7), and acute human T‑cell leukemia (Jurkat) cell lines. Compounds selectively inhibiting the growth of A549 cells have been identified.