Daunorubicin is an anticancer drug, and cholesterol is involved in cancer progression, but
their relationship has not been defined. In this study, we developed a novel experimental model that
utilizes daunorubicin, cholesterol, and daunorubicin plus cholesterol in the same cells (H35) to search
for the role of nuclear lipid microdomains, rich in cholesterol and sphingomyelin, in drug resistance.
We find that the daunorubicin induces perturbation of nuclear lipid microdomains, localized in the
inner nuclear membrane, where active chromatin is anchored. As changes of sphingomyelin species in
nuclear lipid microdomains depend on neutral sphingomyelinase activity, we extended our studies
to investigate whether the enzyme is modulated by daunorubicin. Indeed the drug stimulated the
sphingomyelinase activity that induced reduction of saturated long chain fatty acid sphingomyelin
species in nuclear lipid microdomains. Incubation of untreated-drug cells with high levels of
cholesterol resulted in the inhibition of sphingomyelinase activity with increased saturated fatty acid
sphingomyelin species. In daunodubicin-treated cells, incubation with cholesterol reversed the action
of the drug by acting via neutral sphingomyelinase. In conclusion, we suggest that cholesterol and
sphingomyelin-forming nuclear lipid microdomains are involved in the drug resistance.
