Zing meeting on Medicinal Chemistry 2012-Lanzarote-invitated lecture

Allosteric modulators of Thymidylate synthase, an anticancer drug target Costi MP, Wade Rc, Ferrari Sa, Ponterini Gd, Cardinale Da, Guaitoli Ga, Tondi Da, Marverti Ge, Myllikallio H.f Mangani S.g Thymdylate synthase (TS) plays a key role in the biosynthetic supply of thymidylate, an essential precursor for DNA replication and repair. Indeed, in human cells, downregulation of this pathway halts cellular replication and leads to apoptosis of cancer cells so, hTS active-site inhibitors are largely used in cancer chemotherapy. On the other hand, resistance frequently sets in during treatment with these drugs. While the molecular bases of this phenomenon are complex, there are evidences that it is correlated with protein overexpression presumably connected with the loss of RNA-binding capacity when the protein is bound to its inhibitors. It is therefore desirable to identify inhibitors that act through new mechanisms, such that RNA regulation is not altered1. The design of peptides that mimic portions of the monomer-monomer interface of multimeric proteins has been shown to be a useful approach for the discovery of inhibitors that bind at such interfaces2. In this contribution, we wish to show how these peptides interact with hTS in vitro: the main thermodynamic and structural aspects of this interaction, as well as its consequences on the enzyme catalytic efficiency, have been determined through a multidisciplinary approach of computational design, synthesis, X-ray crystallography and other biophysical techniques. These findings suggest a new mechanism of action and provide useful information for testing against ovarian cancer cells. We have tested the most potent peptides against ovarian cancer cells sensitive and resistant to cis-platin. The peptides were able to inhibit cancer cell growth and, differently from the classical inhibitors, do not show protein over expression. References. 1. E. Chu, et al. Identification of an RNA binding site for human thymidylate synthase. Proc. Natl. Acad. Sci. U.S.A. 1993, 90, 517-521. 2. D. Cardinale, and M.P.Costi et al. Homodimeric enzymes as drug targets. Curr Med Chem. 2010,17, 826-46. The project is supported by FP6 european grant (LIGHTS, Small ligands to interfere with Thymidylate synthase dimer formation as new tools for development of anticancer agents against ovarian carcinoma. www.light-eu.org), LSH 038752.