Cellular resistance against the novel hybrid anthracycline N-(2-chloroethyl)-N-nitrosoureidodaunorubicin (AD 312) is mediated by combined altered topoisomerase II and O6-methylguanine-DNA methyltransferase activities.
N-(2-Chloroethyl)-N-nitrosoureidodaunorubicin (AD 312), a novel semisynthetic compound with combined anthracycline and nitrosourea alkylating functionalities, circumvents resistance conferred by either reduced DNA topoisomerase II (topo II) or increased P-glycoprotein expression with less myelosuppression and cardiotoxicity than adriamycin (doxorubicin; ADR). Cellular resistance to AD 312 could arise from a novel mechanism that confers resistance to both functions simultaneously, or one or more mechanisms common to anthracyclines and/or alkylating agents. The mechanism contributing to AD 312 resistance was investigated following selection of AD 312-resistant murine J774.2 macrophage-like cells and human NCI-H460 non-small-cell lung carcinoma cells. Murine J/312-400 (> 4.7-fold) and human H/312-40 cells (6.3-fold) were cross-resistant to topo II inhibitors (ADR, teniposide, etoposide) and nitrosoureas (carmustine, lomustine) but remained sensitive to vinblastine, colchicine, and camptothecin. There was approximately a twofold decrease in topo II decatenation activity and protein. Decreased net intracellular drug accumulation was not observed. There were no increases in glutathione content or glutathione-S-transferase activity. Increased O6-methylguanine-DNA methyltransferase (MGMT) activity (2.3-fold) was detected in J/312-400, and AD 312 resistance was partially reversed by O6-benzylguanine, a potent inhibitor of MGMT activity. The results suggest that AD 312 resistance arose through selective pressure by both cytotoxic functions in a serial manner.
University of Tennessee Health Science Center, Department of Pharmacology, Memphis 38163, USA.
C A
CA
Pawlik
M
M
Israel
T W
TW
Sweatman
L
L
Lothstein
D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D015153:Blotting, Western; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy / Q000201:enzymology; D002478:Cells, Cultured; D004250:DNA Topoisomerases, Type II / Q000187:drug effects* / Q000378:metabolism*; D019008:Drug Resistance, Neoplasm; D005978:Glutathione / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy / Q000201:enzymology; D008264:Macrophages / Q000187:drug effects / Q000201:enzymology; D051379:Mice; D009607:Nitrosourea Compounds / Q000494:pharmacology*; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000187:drug effects* / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D000903:Antibiotics, Antineoplastic; C115801:N-(2-chloroethyl)-N-nitrosoureidodaunorubicin; D009607:Nitrosourea Compounds; D019853:O(6)-Methylguanine-DNA Methyltransferase; D005982:Glutathione Transferase; D004250:DNA Topoisomerases, Type II; D005978:Glutathione