No abstract

DNA methylation is a mammalian epigenetic mark that is involved in defining where and when genes are expressed, both in normal cells and in the context of diseases. Like other epigenetic marks, it is reversible and can be modulated by chemical agents. Because it plays an important role in cancer by silencing certain genes, such as tumor suppressor genes, and by reactivating other regions, such as repeated elements, it is a promising therapeutic target. Two compounds are already approved to treat hematological cancers. Many efforts have been carried out to discover new molecules that are able to efficiently inhibit DNA methylation in cancer cells. We will briefly overview the foremost of these efforts by focusing on what we have learned to this point on non-nucleoside inhibitors and on what we consider to be the features of an ideal inhibitor.

DNA methyltransferases (DNMT) are promising drug targets in cancer provided that new, more specific, and chemically stable inhibitors are discovered. Among the non-nucleoside DNMT inhibitors, N-phthaloyl-l-tryptophan 1 (RG108) was first identified as inhibitor of DNMT1. Here, 1 analogues were synthesized to understand its interaction with DNMT. The indole, carboxylate, and phthalimide moieties were modified. Homologated and conformationally constrained analogues were prepared. The latter were synthesized from prolinohomotryptophan derivatives through a methodology based amino-zinc-ene-enolate cyclization. All compounds were tested for their ability to inhibit DNMT1 in vitro. Among them, constrained compounds 16-18 and NPys derivatives 10-11 were found to be at least 10-fold more potent than the reference compound. The cytotoxicity on the tumor DU145 cell line of the most potent inhibitors was correlated to their inhibitory potency. Finally, docking studies were conducted in order to understand their binding mode. This study provides insights for the design of the next-generation of DNMT inhibitors.