From Lab to Clinic Antitumor Activity of the Antimicrobial Peptide Magainin II against Bladder Cancer Cell Lines § Jan Lehmann a, *, Margitta Retz b , Sukhvinder S. Sidhu b , Henrik Suttmann a , Michael Sell a , Friedrich Paulsen c , Ju ¨ rgen Harder d , Gerhard Unteregger a , Michael Sto ¨ ckle a a Department of Urology and Pediatric Urology, Saarland University, Homburg/Saar, Germany b Biomolecular Sciences Program, Cardiovascular Research Institute and Department of Anatomy, University of California at San Francisco, San Francisco, CA, USA c Department of Anatomy and Cell Biology, Martin-Luther-Universita ¨ t Halle-Wittenberg, Germany d Department of Dermatology, University Hospital Schleswig-Holstein,Campus Kiel, Germany european urology 50 (2006) 141–147 available at www.sciencedirect.com journal homepage: www.europeanurology.com Article info Article history: Accepted December 19, 2005 Published online ahead of print on January 6, 2006 Keywords: Magainin Antimicrobial peptides Bladder cancer Cell proliferation Cytotoxicity Abstract Objective: Magainin II belongs to a family of antimicrobial peptides and has been shown to exhibit antibiotic activity in a wide range of organisms. Recent studies have also reported a significant antitumor effect of magainin II against various cancer cell lines and tumor mice models. In this study, we evaluated the cytotoxic and anti- proliferative potency of magainin II in bladder tumor cells and normal fibroblasts. Methods: The antiproliferative and cytotoxic effect of magainin II was quantified by colorimetric WST-1-, bromodeoxyuridine (BrdU)-, and lactic dehydrogenase (LDH) assays in three bladder cancer cell lines (RT4, 647V, and 486P) and in the murine fibroblast cell line 3T3 as well as in a primary culture from human fibroblasts. The median inhibitory concentration (IC 50 ) values were determined for each assay, repre- senting the concentration at which cell viability was reduced by 50%. Scanning electron microscopy (SEM) was used to visualize the morphologic effects of magainin II on bladder tumor cells and fibroblasts. Results: Magainin II inhibited cell proliferation of bladder cancer cells in a dose- dependent manner. The average IC 50 of magainin II against all bladder cancer cell lines was 198.1 mM (range, 52.4–484.03 mM) for the WST-1 assay and 75.2 mM (range, 31.0–135.3 mM) for the BrdU assay. The normal murine and human fibroblast cell lines were not affected by magainin II and their IC 50 could not be determined at the concentrations of magainin II tested. LDH release was increased in all bladder tumor cell lines in the presence of magainin II, whereas normal fibroblasts showed no cell lysis. SEM demonstrated lethal membrane perforation by peptide pore formation in bladder cancer cells, but not in fibroblasts. Conclusion: Magainin II peptide exerts cytotoxic and antiproliferative efficacy by pore formation in bladder cancer cells but has no effect on normal murine or human fibroblasts. Magainin II may offer a novel therapeutic strategy in the treatment of bladder cancer with potentially low cytotoxic effects on normal cells. # 2005 European Association of Urology. Published by Elsevier B.V. All rights reserved. § This work was supported by the Deutsche Forschungsgemeinschaft (LE 1213/1-1) and Stiftung zur Fo ¨ rderung der Medizinischen Forschung, Universita ¨ t Kiel. * Corresponding author. Department of Urology and Pediatric Urology, Saarland University, Kirrberger Strasse, 66421 Homburg/Saar, Germany. Tel. +49 6841 1624700; Fax: +49 6841 1624795. E-mail address: jan.lehmann@uniklinikum-saarland.de (J. Lehmann). 0302-2838/$ – see back matter # 2005 European Association of Urology. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.eururo.2005.12.043