Bile Acid Conjugated DNA Chimera that Conditionally Inhibits Carbonic Anhydrase-II in the Presence of MicroRNA-21.

In order to tackle the issue of systemic toxicity in chemotherapy, there is a need to develop novel mechanisms for the activation of protein inhibitors using biomarkers overexpressed in cancer cells. Many current strategies focus on using cancer associated enzymes as a triggering agent for prodrugs. Herein, we detail an alternative approach that harnesses a microRNA (miR-21) that is overexpressed in cancers as the trigger that activates an inhibitor of human carbonic anhydrase-II (hCA-II). Specifically, we have developed a DNA-small molecule chimera (DC) composed of an hCA-II binding lithocholic acid amide (LAA) headgroup that can transition from a rigid duplex state (that does not bind appreciably to hCA) to a single-stranded conformation via a miR-21 trigger. The activated single-stranded DC can project the LAA headgroup into the hCA-II active site and is a robust hCA-II inhibitor (K(i) of 3.12 μM). This work may spur research into developing new classes of cancer selective protein inhibitors.