| Authors |
Eunsik Lee, Cheol Kwak, Seok-Soo Byun, Dae Jung Lim, Jeong Hyun Kim, Soo Woong Kim, Chongwook Lee, Han-Jong Ahn; |
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| Abstract |
This study was designed to develop new cisplatin-resistant bladder tumor
cell lines and to elucidate the underlying mechanism of acquired
resistance to cisplatin. We have established 2 cisplatin-resistant cell
lines, T24R1 and T24R2, from the T24 human bladder transitional carcinoma
cell line, by continuous exposure to increasing concentrations of
cisplatin. To elucidate the mechanisms of cisplatin resistance in these
sublines, we investigated cellular morphology by light microscopy, growth
rate, cell cycle by flow cytometry, glutathione (GSH) content, glutathione
peroxidase (GP) and glutathione S-transferase (GST) activities, GST
isoenzymes, P-glycoprotein expression, and the activity of topoisomerases
I and II. The cytoplasms of the T24R1 and T24R2 cells displayed many
vesicles and contained abundant granular material compared with the parent
cells. Cell growth, DNA synthesis, and cell-cycle distribution of the
cisplatin-resistant sublines did not differ from those of the parental T24
cells. T24R1 and T24R2 were 12.8-and 18-fold more resistant to cisplatin,
respectively, than the parent cells were. GSH content, and GP and GST
activities were elevated in the T24R2 cells compared with the T24 cells
(p<0.05). Western blot analysis revealed that the expression of the GST-
isoenzyme was elevated in T24R2 cells. The sublines showed no induction of
P-glycoprotein or topoisomerases I or II. In conclusion, an elevation in
GSH metabolism and in the expression of the related enzymes appears to
play an important role in the mechanism underlying cisplatin resistance in
the T24R2 subline.
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