Aims: The mechanisms behind cellular anthracycline uptake are not completely understood. Knowledge about
uptake mechanisms could be used to increase the selectivity of the drugs. We compared the uptake patterns of, daunorubicin
(DNR), doxorubicin (DOX), epirubicin (EPI), idarubicin (IDA), and pirarubicin (PIRA) by cultured leukemic cells
and investigated possible involvement of specific carriers. Methods: HL-60 cells were incubated with anthracyclines for 1
hour in the absence or presence of transport inhibitors, suramin, or nucleosides and cellular drug uptake was determined.
Cell survival was also determined. MCF-7 breast cancer cells were used as a negative control for concentrative nucleoside
transporters (CNTs). Anthracycline concentration was determined with HPLC and fluorometric detection and apoptosis
was determined with propidium iodide and flow cytometry. Results: DNR, IDA, and PIRA had higher uptake than DOX
and EPI with a prominent increase in uptake at concentrations > 1 µM. Uptake of all anthracyclines was greatly reduced at
0°C. Suramin, a purinergic-2-receptor inhibitor, strongly inhibited the uptake of all anthracyclines except PIRA and increased
cell survival. Dipyridamole, an equilibrative NT (ENT) inhibitor, significantly inhibited the uptake of DNR only.
The addition of nucleosides significantly inhibited the uptake of DNR, IDA, and PIRA but not in MCF-7 cells lacking
functional CNTs. Conclusion: Our results suggest different uptake mechanisms for the anthracyclines studied. We found
evidence for carrier mediated uptake mechanisms, supporting involvement of NTs in transmembrane transport of DNR,
IDA, and PIRA. The results also showed a strong inhibition of suramin on anthracycline uptake by so far unknown