G-Quadruplex Formed by the Promoter Region of the hTERT Gene: Structure-Driven Effects on DNA Mismatch Repair Functions.

G-quadruplexes (G4s) are a unique class of noncanonical DNAs that play a key role in cellular processes and neoplastic transformation. Herein, we focused on the promoter region of human TERT oncogene, whose product is responsible for the immortality of cancer cells. It has been shown by chemical probing and spectroscopic methods that synthetic 96-nt DNAs modeling the wild-type G-rich strand of the hTERT promoter and its variants with G>A point substitutions corresponding to somatic driver mutations fold into three stacked parallel G4s with sites of local G4 destabilization caused by G>A substitutions in the G4 motif. These models were used to elucidate how the hTERT multiG4 affects the binding affinity and functional responses of two key proteins, MutS and MutL, involved in the initial stage of DNA mismatch repair (MMR) in Escherichiacoli and Neisseriagonorrhoeae with different MMR mechanisms. We have shown for the first time that (i) point substitutions do not affect the effective binding of these proteins to the hTERT G4 structure, and (ii) the endonuclease activity of MutL from N. gonorrhoeae is significantly suppressed by the stable G4 scaffold. It is likely that some of the genomic instability associated with G4 may be related to the blockage of human intrinsic methyl-independent MMR attempting to operate near G4 structures.

Synthetic Design and Biological Evaluation of New p53-MDM2 Interaction Inhibitors Based on Imidazoline Core.

The use of p53-MDM2 inhibitors is a prospective strategy in anti-cancer therapy for tumors expressing wild type p53 protein. In this study, we have applied a simple approach of two-step synthesis of imidazoline-based alkoxyaryl compounds, which are able to efficiently inhibit p53-MDM2 protein-protein interactions, promote accumulation of p53 and p53-inducible proteins in various cancer cell lines. Compounds 2l and 2k cause significant upregulation of p53 and p53-inducible proteins in five human cancer cell lines, one of which possesses overexpression of MDM2.

2,4,5-Tris(alkoxyaryl)imidazoline derivatives as potent scaffold for novel p53-MDM2 interaction inhibitors: Design, synthesis, and biological evaluation.

Imidazoline-based small molecule inhibitors of p53-MDM2 interaction intended for the treatment of p53 wild-type tumors are the promising structures for design of anticancer drugs. Based on fragment approach we have investigated a key role of substituents in cis-imidazoline core for biological activity of nutlin family compounds. Although the necessity of the substituents in the phenyl rings of cis-imidazoline has been shown, there are no studies in which the replacements of a halogen by other substituents have been investigated. A series of simple cis-imidazoline derivatives containing halogen, hydroxy and alkoxy-substituents were synthesized. The biological activity of the compounds was studied using assays of cytotoxicity (MTT) and p53 level. It was found that the hydroxyl-derivatives were not cytotoxic whereas the alkoxy analogues were the same or more active as halogen-substituted compounds in cell viability test. The synthesized alkoxy derivatives induced an increase of p53 level and did not promote necrotic cell death in the concentration up to 40 µM.