Differences in intracellular sites of action of Adriamycin in neoplastic and normal differentiated cells

Abstract

Purpose: This study was performed to clarify the intracellular specificity of the differential cytotoxic effects of Adriamycin (ADM) on neoplastic and normal cells. Methods: The mouse lymphocytic leukemia cell line L1210 and pig kidney proximal tubular epithelial cell line LLC-PK₁ were used as neoplastic and normal cells, respectively. These cells were treated with various concentrations of ADM for 24 h and toxicological parameters were determined. Results: ADM (0.1–10 µM) significantly down-regulated cell growth rate and [³H]thymidine incorporation into DNA in the log phase, and at concentrations of more than 1 µM reduced the viability of both cell lines. Lipid peroxidation was increased at 1 µM ADM in L1210 cells and at 10 µM ADM in LLC-PK₁ cells. The microsomal and nuclear fractions of both cell lines showed approximately the same level of ADM-induced superoxide anion (O₂ ^–) production, while the mitochondrial fraction of differentiated LLC-PK₁ cells produced the highest levels of O₂ ^–. Differentiated LLC-PK₁ cells showed the highest mitochondrial NADH-cytochrome c reductase activity. L1210 cells showed lower mitochondrial activities of enzymes involved in scavenging of reactive oxygen species, such as superoxide dismutase, glutathione peroxidase and catalase, than the other cells. Conclusions: These results suggest that ADM exerts cytostatic effects on neoplastic and normal undifferentiated cells through the inhibition of DNA synthesis by DNA intercalation, and cytotoxic effects on neoplastic cells through the accumulation of reactive oxygen species resulting from low scavenger enzyme activities. The cytotoxic effects on normal differentiated cells may be related to the high levels of production of reactive oxygen species due to high mitochondrial NADH-cytochrome c reductase activity.