Studying mechanisms of
drug antitumor action is complicated by the lack of noninvasive methods enabling direct monitoring of the state and interactions of the drugs within intact viable cells. Here we present a confocal spectral imaging (CSI) technique as a method of overcoming this problem. We applied this method to the examination of localization and interactions of
mitoxantrone (1, 4-dihydroxy-5, 8-bis-[([2-(2-hydroxyethyl)-amino]ethyl)amino]-9,10-
anthracenedione dihydrochloride), a potent
antitumor drug, in living K562 cells. A two-dimensional set of fluorescence spectra of
mitoxantrone (
MITOX) recorded with micron resolution within a
drug-treated cell was analyzed to reveal formation of
drug-target complexes and to create the maps of their intracellular distribution. The analysis was based on detailed in vitro modeling of
drug-target (
DNA,
RNA,
DNA topoisomerase II) interactions and environmental effects affecting
drug fluorescence.
MITOX exposed to aqueous intracellular environment,
MITOX bound to hydrophobic cellular structures, complexes of
MITOX with
nucleic acids, as well as the naphtoquinoxaline metabolite of
MITOX were simultaneously detected and mapped in K562 cells. These states and complexes are known to be immediately related to the antitumor action of the
drug. The results obtained present a basis for the subsequent quantitative analysis of concentration and time-dependent accumulation of free and bound
MITOX within different compartments of living
cancer cells.