title: Selenite-induced apoptosis in doxorubicin-resistant cells and effects on the thioredoxin system.
abstract: Selenium treatment of the doxorubicin-resistant cell line, U-1285dox, derived from human small cell carcinoma of the lung, resulted in massive apoptosis. This effect appeared maximal at 2 days after addition of selenite. The apoptosis was caspase-3 independent as revealed by Western blot analysis, activity measurement and by using caspase inhibitors. Induction of apoptosis was significantly more pronounced and occurred after addition of lower concentrations of selenite in the doxorubicin-resistant cells compared to the parental doxorubicin-sensitive cells. High levels of selenite caused necrosis in the doxorubicin-sensitive cells. Analysis of enzymatic activity (insulin reduction) of thioredoxin reductase (TrxR) and TrxR protein concentration, measured by ELISA, revealed increasing activity and protein levels after treatment with increasing concentrations of selenium. Maximum relative increase was induced up to 1 microM in both sublines and at this selenium level the concentrations of TrxR measured as insulin reducing activity or ELISA immunoreactivity were nearly identical. Increasing concentrations of selenite up to 10 microM resulted in increased activity and concentration of TrxR in the sensitive subline but decreasing levels in the resistant subline. The level of truncated Trx (tTrx) was higher in the resistant U-1285dox cells but the level did not change with increasing selenite concentrations. Our results demonstrate pronounced selective selenium-mediated apoptosis in therapy-resistant cells and suggest that redox regulation through the thioredoxin system is an important target for cancer therapy.
authors.affiliation: Division of Hematology and Oncology, Department of Medicine, Karolinska Institutet, Huddinge University Hospital, Stockholm SE-141 86, Sweden.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Jönsson-Videsäter
authors.forename: Linda
authors.initials: L
authors.lastname: Björkhem-Bergman
authors.forename: Akter
authors.initials: A
authors.lastname: Hossain
authors.forename: Anita
authors.initials: A
authors.lastname: Söderberg
authors.forename: Lennart C
authors.initials: LC
authors.lastname: Eriksson
authors.forename: Christer
authors.initials: C
authors.lastname: Paul
authors.forename: Anders
authors.initials: A
authors.lastname: Rosén
authors.forename: Mikael
authors.initials: M
authors.lastname: Björnstedt
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D004317:Doxorubicin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D008938:Mitosis / Q000187:drug effects; D018038:Sodium Selenite / Q000494:pharmacology*; D013880:Thioredoxin-Disulfide Reductase / Q000378:metabolism; D013879:Thioredoxins / Q000187:drug effects / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D013879:Thioredoxins; D004317:Doxorubicin; D013880:Thioredoxin-Disulfide Reductase; D018038:Sodium Selenite