Confocal microscopy of idarubicin localisation in sensitive and multidrug-resistant bladder cancer cell lines.

Idarubicin is a highly lipophilic anthracycline and appears effective against tumours resistant to conventional anthracyclines. Confocal microscopy demonstrates predominantly cytoplasmic idarubicin accumulation. This distribution is unaltered by resistance status or the resistance reversing agent verapamil. Our results contrast with studies on conventional anthracyclines and suggest that nuclear accumulation may not be a prerequisite for anthracycline cytotoxicity.