Development of ethynyl-2'-deoxyuridine chemical probes for cell proliferation.

A common method of evaluating cellular proliferation is to label DNA with chemical probes. 5-Ethynyl-2'-deoxyuridine (EdU) is a widely utilized chemical probe for labeling DNA, and upon incorporation, EdU treatment of cells is followed by a reaction with a small molecule fluorescent azide to allow detection. The limitations when using EdU include cytotoxicity and a reliance on nucleoside active transport mechanisms for entry into cells. Here we have developed six novel EdU pro-labels that consist of EdU modified with variable lipophilic acyl ester moieties. This pro-label:chemical probe relationship parallels the prodrug:drug relationship that is employed widely in medicinal chemistry. EdU and EdU pro-labels were evaluated for their labeling efficacy and cytotoxicity. Several EdU pro-label analogues incorporate into DNA at a similar level to EdU, suggesting that nucleoside transporters can be bypassed by the pro-labels. These EdU pro-labels also had reduced toxicity compared to EdU.