Synthesis, biological evaluation and molecular modeling of new analogs of the anti-cancer agent 2-methoxyestradiol: potent inhibitors of angiogenesis

Abstract

The synthesis, cytotoxicity, inhibition of tubulin polymerization and anti-angiogenic effects of 10 analogs of 2-methoxyestradiol are reported. These efforts revealed that the analog with a 4-pyridine ring in the 17-position, in combination with 2-ethyl- and 3-sulfamate substituents on the steroid A-ring, is the most interesting anti-cancer agent. This compound showed potent inhibitory effects against angiogenesis (IC₅₀ = 0.1 ± 0.02 μM) and selective cytotoxic effects towards the CEM, H460 and HT-29 cancer cell lines, with no cytotoxicity observed against the healthy VERO cell line. The most interesting analog also displayed inhibition of tubulin polymerization (IC₅₀ = 4.3 μM) almost as potent as 2-methoxyestradiol (IC₅₀ = 3.5 μM). Molecular modeling experiments showed that this analog interacts within the colchicine-binding site of β-tubulin via multiple bonding with several amino acids. These observations provide support that the cytotoxic and anti-angiogenic effects observed for this novel analog are, at least in part, mediated by binding to tubulin.