Isolation and characterization of a cell line resistant to 5-[3-(2-nitro-1-imidazoyl)-propyl]-phenanthridinium bromide (2-NLP-3), a DNA-intercalating hypoxic cell radiosensitizer and cytotoxin.
A DNA-targeted hypoxic cell radiosensitizer and cytotoxin, 5-[3-(2-nitro-1-imidazoyl)-propyl]-phenanthridinium bromide (2-NLP-3), has been shown previously to have increased efficacy over untargeted analogues in vitro. To further study the mechanism of action of this compound, a cell line, CHO-1000, derived from Chinese hamster ovary (CHO) AA8-4 cells was isolated. This cell line is capable of continuously growing in a concentration of 2-NLP-3 approximately 10-fold greater than that tolerated by wild-type CHO cells. The resistance of CHO-1000 to 2-NLP-3 was compared with that of the P-glycoprotein overexpressing, multidrug resistant Chinese hamster cell line CHR-C5 (C5). The resistance of CHO-1000 cells to the acute toxic effects of 2-NLP-3 under both hypoxic and aerobic exposure conditions was intermediate to that of the sensitive CHO wild-type cells and the resistant C5 cells. A similar pattern was seen for the hypoxic cell radiosensitizing ability of 2-NLP-3. 2-NLP-3 produced significant depletion of glutathione under both hypoxic and aerobic conditions in all three cell lines studied, and the degree of depletion was correlated with drug toxicity. CHO-1000 and C5 cells were significantly more resistant to colchicine and doxorubicin compared with wild-type cells. The toxicity pattern of 2-NLP-3 and its comparison phenanthridinium ion, P3, was not the same for CHO-1000 cells compared with C5 cells. Verapamil was an effective agent for reversing the hypoxic resistance to 2-NLP-3 in both CHO-1000 and C5 cells, but only a partial reversal of aerobic resistance was observed in CHO-1000 cells. These results indicate that the resistant phenotype of CHO-1000 is mediated to some degree by P-glycoprotein expression, but that other as yet unidentified factors are also involved.
Cowan
D S
DS
Experimental Therapeutics Division, Ontario Cancer Institute, Toronto, Canada.
McClelland
R A
RA
Rauth
A M
AM
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000502:physiology; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D016466:CHO Cells / Q000187:drug effects*; D015687:Cell Hypoxia; D002469:Cell Separation; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D006224:Cricetinae; D004351:Drug Resistance; D005978:Glutathione / Q000378:metabolism; D007364:Intercalating Agents / Q000494:pharmacology*; D009593:Nitroimidazoles; D010617:Phenanthridines / Q000494:pharmacology*; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D007364:Intercalating Agents; D009593:Nitroimidazoles; D010617:Phenanthridines; D011838:Radiation-Sensitizing Agents; C059179:NLP 1; D005978:Glutathione