title: Role of transferrin receptor and the ABC transporters ABCB6 and ABCB7 for resistance and differentiation of tumor cells towards artesunate.
abstract: The anti-malarial artesunate also exerts profound anti-cancer activity. The susceptibility of tumor cells to artesunate can be enhanced by ferrous iron. The transferrin receptor (TfR) is involved in iron uptake by internalization of transferrin and is over-expressed in rapidly growing tumors. The ATP-binding cassette (ABC) transporters ABCB6 and ABCB7 are also involved in iron homeostasis. To investigate whether these proteins play a role for sensitivity towards artesunate, Oncotest's 36 cell line panel was treated with artesunate or artesunate plus iron(II) glycine sulfate (Ferrosanol). The majority of cell lines showed increased inhibition rates, for the combination of artesunate plus iron(II) glycine sulfate compared to artesunate alone. However, in 11 out of the 36 cell lines the combination treatment was not superior. Cell lines with high TfR expression significantly correlated with high degrees of modulation indicating that high TfR expressing tumor cells would be more efficiently inhibited by this combination treatment than low TfR expressing ones. Furthermore, we found a significant relationship between cellular response to artesunate and TfR expression in 55 cell lines of the National Cancer Institute (NCI), USA. A significant correlation was also found for ABCB6, but not for ABCB7 in the NCI panel. Artesunate treatment of human CCRF-CEM leukemia and MCF7 breast cancer cells induced ABCB6 expression but repressed ABCB7 expression. Finally, artesunate inhibited proliferation and differentiation of mouse erythroleukemia (MEL) cells. Down-regulation of ABCB6 by antisense oligonucleotides inhibited differentiation of MEL cells indicating that artesunate and ABCB6 may cooperate. In conclusion, our results indicate that ferrous iron improves the activity of artesunate in some but not all tumor cell lines. Several factors involved in iron homeostasis such as TfR and ABCB6 may contribute to this effect.
authors.affiliation: Oncotest GmbH, Institute of Experimental Oncology, Freiburg, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Kelter
authors.forename: Daniel
authors.initials: D
authors.lastname: Steinbach
authors.forename: Venkata Badireenath
authors.initials: VB
authors.lastname: Konkimalla
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Tahara
authors.forename: Shigeru
authors.initials: S
authors.lastname: Taketani
authors.forename: Heinz-Herbert
authors.initials: HH
authors.lastname: Fiebig
authors.forename: Thomas
authors.initials: T
authors.lastname: Efferth
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D037621:Artemisinins / Q000494:pharmacology*; D000077332:Artesunate; D002454:Cell Differentiation / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D019008:Drug Resistance, Neoplasm; D006801:Humans; D051379:Mice; D011990:Receptors, Transferrin / Q000378:metabolism*
chemical_list: C107991:ABCB6 protein, human; C113037:ABCB7 protein, human; D018528:ATP-Binding Cassette Transporters; D000970:Antineoplastic Agents; D037621:Artemisinins; D011990:Receptors, Transferrin; D000077332:Artesunate