CHARACTERIZATION OF MOUSE LEUKEMIA-L1210 CELLS RESISTANT TO THE RIBONUCLEOTIDE REDUCTASE INHIBITOR 4-METHYL-5-AMINO-1-FORMYLISOQUINOLINE THIOSEMICARBAZONE
Ah. Cory et al., CHARACTERIZATION OF MOUSE LEUKEMIA-L1210 CELLS RESISTANT TO THE RIBONUCLEOTIDE REDUCTASE INHIBITOR 4-METHYL-5-AMINO-1-FORMYLISOQUINOLINE THIOSEMICARBAZONE, Oncology research, 8(10-11), 1996, pp. 449-456
Mouse leukemia L1210 cells were generated for resistance to 4-methyl-5
-amino-1-formylisoquinoline thiosemicarbazone (MAIQ), a potent inhibit
or of ribonucleotide reductase that is directed at the nonheme iron su
bunit (NHI) of the enzyme, The resistant cells, MQ-580, showed an 8-fo
ld increase in IC50 toward MAIQ, a 4-fold increase in IC50 toward hydr
oxyurea, and also showed resistance to other ribonucleotide reductase
inhibitors. In addition, the MQ-580 cell line was resistant to nonribo
nucleotide reductase inhibitors such as etoposide, daunomycin and vinb
lastine, but not to cisplatin, The mRNA for the NHI subunit was increa
sed 7-fold in the MQ-580 cells with essentially no change in the mRNA
level for the effector-binding subunit, The ribonucleotide reductase a
ctivity in the cell-free extracts prepared from the MQ-580 cells was o
nly slightly elevated (30%). However, passage of the cell-free extract
from the MQ-580 cells over Sephadex G-25 resulted in a 4.8-fold incre
ase in specific activity over that of the wild-type cells. While the r
eductase activity in the cell-free extract from the MQ-580 cells did n
ot show altered sensitivity to MAIQ, the reductase activity in the cel
l-free extract from the MQ-580 cells was much more sensitive to the ef
fects of the iron-chelating agents Desferal and EDTA. The cell pellets
from the MQ-580 cells were much darker in color than the pellets from
the wild-type cells or hydroxyurea-resistant cells. The supernatant f
raction from the MQ-580 cells after-SDS-PAGE showed the appearance of
a strong Coomassie blue-staining band at 50 kDa that was not apparent
in either the wild-type or hydroxyurea-resistant cells. This new resis
tant cell line offers an opportunity to explore differences in resista
nce mechanisms of drugs (e.g. MAIQ and hydroxyurea) that are directed
at the same subunit of ribonucleotide reductase. Copyright (C) 1996 El
sevier Science Inc.