Cellular delivery of dinucleotides by conjugation with small molecules: targeting translation initiation for anticancer applications

Targeting cap-dependent translation initiation is one of the experimental approaches that could lead to the development of novel anti-cancer therapies. Synthetic dinucleoside 5',5'-triphosphates Cap Analogs are potent antagonists of eukaryotic translation initiation factor 4E (eIF4E) in vitro and could counteract elevated levels of eIF4E in Cancer cells; however, transformation of these compounds into therapeutic agents remains challenging - they do not easily penetrate into cells and are susceptible to enzymatic cleavage. Here, we tested the potential of several small molecule ligands - folic acid, biotin, glucose, and Cholesterol - to deliver both hydrolyzable and cleavage-resistant Cap Analogs into cells. A broad structure-activity relationship (SAR) study using model fluorescent probes and cap-ligand conjugates showed that Cholesterol greatly facilitates uptake of Cap Analogs without disturbing the interactions with eIF4E. The most potent Cholesterol conjugate identified showed apoptosis-mediated cytotoxicity towards Cancer cells.