Identification of chemically diverse Cdc25 phosphatase inhibitors by receptor-based virtual screening

The cell division cycle 25 (Cdc25) family of proteins are highly conserved dual specificity phosphatases that regulate cyclin-dependent kinases, the main gatekeepers of the eukaryotic cell division cycle. The three isoforms of Cdc25, including Cdc25A, Cdc25B and Cdc25C, appear to act on different cyclin-dependent kinase/cyclin complexes at different stages of the cell cycle. Overexpression of Cdc25A and/or Cdc25B, but not Cdc25C, has been detected in numerous cancers and is often correlated with a poor clinical prognosis; Thus, the inhibition of these phosphatases may represent a promising therapeutic approach in oncology [1-2]. So, a computer-aided drug design protocol involving virtual screening was performed on Cdc25B crystal structure (Figure 1) [3] in order to identify novel classes of inhibitors. In vitro experiments carried out on a selected list of 30 molecules led to the discovery of 4 compounds able to inhibit Cdc25A and B activity at low micromolar concentrations and to the significant inhibition of the MCF-7 breast cancer cell proliferation. All selected compounds also affected MCF-7 cell cycle progression. Furthermore, kinetics studies were realised on the phosphatase activity catalysed by Cdc25B in the presence of the above-mentioned compounds, in order to establish type and power of inhibition.