Magnetic resonance spectroscopy and fluorescence microscopy to investigatemobile lipids in sensitive, resistant and reverting K562 cells and their membranes

The erythroleukaemic K562 cell line and its adriamycin resistant counterpar t were used to study resistance, its reversion and their consequences on th e levels and localisation of lipids detected in proton nuclear magnetic res onance (NMR) spectra. On whole cells, the mobile lipids giving rise to a NM R signal were significantly elect-eased in the resistant cells when compare d to the sensitive ones; these lipids recovered partially in the reverting cells. According to the spin-lattice relaxation times (T-1) the lipids dete cted appeared to be in a similar environment in sensitive and reverting cel ls. In membrane-enriched fractions mobile lipid levels were not significant ly different in the sensitive and reverting cell fines but decreased in res istant ones. Moreover, lipid droplets stained with a fluorescent Nile red l ipophilic probe showed the presence of highly fluorescent particles in the samples in which NMR detected high levels of mobile lipids. These results s uggest the participation of cytosolic lipid droplets in NMR signals in drug sensitive and reverting cells and open the question of the relative roles of these droplets and of the membrane lipids in the lipid metabolic pathway s associated with drug resistance in cancer cells.