Taxol resistance and its reversal by synthetic isoprenoids in human bladder cancer cell line.

Purpose: We investigated the mechanism of action of reversal agents for taxol-resistance in bladder cancers.

Materials And Methods: We isolated a taxol-resistant cell line (KK47/TX30) from a human KK47 bladder cancer cell line (KK47/WT). We characterized KK47/TX30 cells and screened reversal agents for taxol-resistance.

Results: KK47/TX30 cells exhibited approximately 700-fold resistance to taxol and cross-resistance to Vinca alkaloids and topoisomerase II inhibitors. Western blot analysis demonstrated P-glycoprotein (P-gp) overexpression in taxol-resistant cells. Drug accumulation and efflux studies showed that the decreased taxol accumulation in the resistant cell line was due to enhanced taxol efflux. We synthesized 31 isoprenoids based on the structure of N-solanesyl-N,N'-bis(3,4-dimethoxybenzyl)ethylenediamine (SDB), which could completely reverse multidrug resistance (MDR) as shown previously. Among those examined, trans-N,N'-bis(3,4-dimethoxybenzyl)-N-solanesyl-1,2-diaminocyclohexane (N-5228) could completely reverse taxol-resistance in KK47/TX30 cells. Results of a structure-activity relationship study of isoprenoids suggested that the following structural features were important for overcoming taxol-resistance: (1) a basic structure of 8 to 10 isoprene units, (2) a cyclohexane ring or benzene ring within the framework, (3) two cationic sites in close proximity to each other, and (4) a benzyl group with 3,4-dimethoxy functionalities with moderate electron-donation.

Conclusions: Taxol-resistance was primarily mediated by P-gp overexpression in KK47/TX30 cells. One of the synthetic isoprenoids, N-5228 could completely reverse taxol-resistance in KK47/TX30 cells.