Potent Apoptotic Response Induced by Chloroacetamidine Anthrathiophenediones in Bladder Cancer Cells.

We previously found that two neighboring G-quadruplexes behave as a molecular switch controlling the expression of HRAS (Cogoi, S.; Schekotikhin, A. E.; Xodo, L. E. Nucl. Acids Res. 2014, DOI: 10.1093/nar/gku574). In this study we have designed anthrathiophenediones with two chloroacetamidine-containing side chains (CATDs) as G-quadruplex binders and have examined their anticancer activity in T24 bladder cancer cells bearing mutant HRAS and in T24 xenografts. The designed CATDs (3a-e), bearing alkyl side chains of different length, penetrate T24 cancer cells more than their analogues with guanidine-containing side chains. The lead compounds 3a and 3c inhibit HRAS expression, metabolic activity, and colony formation in T24 cancer cells. They also activate a strong apoptotic response, as indicated by PARP-1, caspases 3/7, and annexin V/propidium iodide assays. Apoptosis occurs under conditions where cyclin D1 is down-regulated and the cell cycle arrested in G2 phase. Finally, compound 3a inhibits the growth of T24 xenografts and increases the median survival time of nude mice.