QUANTITATIVE CONFOCAL SPECTRAL IMAGING ANALYSIS OF MITOXANTRONE WITHIN LIVING K562 CELLS - INTRACELLULAR ACCUMULATION AND DISTRIBUTION OF MONOMERS, AGGREGATES, NAPHTHOQUINOXALINE METABOLITE, AND DRUG-TARGET COMPLEXES

Confocal spectral imaging (CSI) technique was used for quantitative an alysis of the uptake, subcellular localization, and characteristics of localized binding and retention of anticancer agent mitoxantrone (MIT OX) within human K562 erythroleukemia cells. The CSI technique enables identification of the state and interactions of the drug within the l iving cells. Utilizing this unique property of the method, intracellul ar distributions were examined for monomeric MITOX in polar environmen t, MITOX bound with hydrophobic cellular structures, naphthoquinoxalin e metabolite, and nucleic acid-related complexes of MITOX. The feature s revealed were compared for the cells treated with 2 mu M or 10 mu M of MITOX for 1 h and correlated to the known data on antitumor action of the drug. MITOX was found to exhibit high tendency to self-aggregat ion within intracellular media. The aggregates are concluded to be a d eterminant of long-term intracellular retention of the drug and a sour ce of persistent intracellular binding of MITOX. Considerable penetrat ion of MITOX in the hydrophobic cytoskeleton structures as well as gro wing accumulation of MITOX bound to nucleic acids within the nucleus w ere found to occur in the cells treated with a high concentration of t he drug. These effects may be among the factors stimulating and/or acc ompanying high-dose mitoxantrone-induced programmed cell death or apop tosis.