A study of correlation between NPM-translocation and apoptosis in cells induced by daunomycin

Human leukemia K562 and HeLa cells were treated with daunomycin (DA) for 1- 4 hr. With the indirect immunofluorescence technique, we observed that the nucleolar protein nucleophosmin/B23 (NPM) shifted its location from the nuc leolus to the nucleoplasm (NPM-translocation). The degree of NPM-translocat ion was determined by the relative immunofluorescent intensity in the nucle oli vs the nucleoplasm (defined as localization index, LI). We found that N PM-translocation, as determined by the decrease of LI, correlates with cyto toxicity. The degrees of NPM-translocation, chromatin condensation, and DNA fragmentation in HeLa cells were determined after treatment with 0.1, 0.5 and 1 mu g/mL DA for 1 hr. We found that NPM-translocation (LI < 2.5) was o bserved in cells during the treatment with 0.5 and 1 but not with 0.1 mu g/ mL DA. Also, cells treated with 1 mu Lg/mL remained in an NPM-translocated state for a longer time (5-6 hr) than those cells treated with 0.5 mu g/mL (1-2 hr). Cells treated with 0.5 and 1 mu g/mL DA showed increased levels o f chromatin condensation beginning at 5 hr after the drug treatment. The nu mber of cells with condensed chromatin increased with both time and drug co ncentration. No cells with condensed chromatin were observed in samples tre ated with 0.1 mu g/mL DA, which also showed no significant NPM-translocatio n. Similar results were observed for induction of DNA fragmentation. We fou nd that the drug concentration required for induction of DNA fragmentation and chromatin condensation coincided with the drug concentration required f or NPM-translocation. Taken together, these results indicate that NPM-trans location correlates with apoptosis induced by daunomycin. BIOCHEM PHARMACOL 57;11:1265-1273, 1999. (C) 1999 Elsevier Science Inc.