New arylthioindoles: potent inhibitors of tubulin polymerization. 2. Structure-activity relationships and molecular modeling studies.

Arylthioindoles (ATIs) that possess a 3-methoxyphenylthio or a 3,5-dimethoxyphenylthio moiety at position 2 of the indole ring were effective tubulin assembly inhibitors, but weak inhibitors of MCF-7 cell growth. ATIs bearing a 3-(3,4,5-trimethoxyphenyl)thio moiety were potent tubulin polymerization inhibitors, with IC(50)s in the 2.0 (35) to 4.5 (37) microM range. They also inhibited MCF-7 cell growth at nanomolar concentrations. The 3,4,5-trimethoxy substituted ATIs showed potencies comparable to those of the reference compounds colchicine and combretastatin A-4 in both tubulin assembly and cell growth inhibition assays. Dynamics simulation studies correlate well with the observed experimental data. Furthermore, from careful analysis of the biological and in silico data, we can now hypothesize a basic pharmacophore for this class of compounds.