Expression of Bcl-2 and Bax in cis-Diamminedichloroplatinum (II)-Resistant Bladder Cancer Cell Lines

Song, Cheryn; Kang, Tae jin; You, Dal san; Hong, Jun Hyuk; Ahn, Han jong

Abstract

PURPOSE: Development of drug resistance has been the major obstacle in cis-Diamminedichloroplatinum (II) (cisplatin)-based combination chemotherapy in the treatment of advanced bladder cancer for which a variety of mechanisms has been suggested. We investigated to determine the changes of expression of apoptotic regulator proteins Bcl-2 and Bax in cisplatin-resistant bladder cancer cell lines and the reversibility of chemoresistance with antisense oligonucleotide against Bcl-2.
MATERIALS AND METHODS
In T24, J82, 253J, 253J-BV and HT-1376 bladder cancer cell lines, we established cisplatin-resistance using stepwise exposure to cisplatin. The changes of Bcl-2 and Bax proteins in the resistant cell lines were determined by Western blot. Then, after administration of antisense oligonucleotide targeting the Bcl-2 coding sequence to the T24, T24-R1, and T24-R2 cell lines with lipofectamine, changes of Bcl-2 expression were determined along with cisplatin cytotoxicity before and after transfection.
RESULTS
We confirmed the acquisition of cisplatin resistance in all 5 cell lines as the percent increase of IC50 in each cell lines were 210%, 175%, 181%, 280% and 153%, respectively. The expression of Bcl-2 protein increased in all 5 cisplatin-resistant cell lines, while the expressions of Bax decreased in 4 of 5 cisplatin-resistant cell lines. Treatment with antisense oligonucleotide significantly enhanced the cytotoxicity of cisplatin in T24, T24-R1 and T24-R2 cell lines.
CONCLUSIONS
These results suggest that the up-regulation of Bcl-2 expression as well as down-regulation of Bax expression may be one of the mechanisms of cisplatin resistance in bladder cancer cells, and antisense Bcl-2 oligonucleotide may be helpful in chemotherapy of bladder cancer by reversing cisplatin resistance.