Fluorescence properties and cellular distribution of the investigational anticancer drug triapine (3-aminopyridine-2-carboxaldehyde thiosemicarbazone) and its zinc(II) complex.

Triapine (3-aminopyridine-2-carboxaldehyde thiosemicarbazone), which entered several phase I and II clinical trials as an antitumor chemotherapeutic agent, was found to possess intrinsic fluorescence properties (lambda(ex) = 360 nm), which enabled us to monitor the uptake and intracellular distribution in living human cancer cells by fluorescence microscopy.