Abstract
MGMT protein, which has been associated with resistance to antitumor alkylation drugs for many patients, is a very useful prognostic marker to provide a guide for therapeutic decisions. Considering the large number of cellular samples that have to be handled at the hospital every day, it is thus important to develop a rapid and simple analytical method to distinguish MGMT activity in different types of cells. In this study, we describe the first MGMT fluorescence activation probe for the rapid no-wash imaging of MGMT in living cells. The probe consists of a specific MGMT suicide pseudosubstrate, O6-benzylguanine and a fluorescent molecular rotor CCVJ. In the presence of MGMT, the enzyme transfers CCVJ to the protein active site where the crowded surrounding restricts the bond rotation of the fluorescent molecular rotor to trigger fluorescence activation of about 170-fold. With this probe, bright fluorescence was observed for MGMT-positive, Hela S3, MCF-7 and HEK293 cells, while MGMT-deficient CHO cells displayed no fluorescence. This fluorescence activation probe design can also be extended for the detection of other transferases and binding proteins for which there are still no effective methods to image them in living cells.