Table of Contents
ISRN Pharmacology
Volume 2011, Article ID 314209, 11 pages
http://dx.doi.org/10.5402/2011/314209
Research Article

Novel Phenazine 5,10-Dioxides Release OH in Simulated Hypoxia and Induce Reduction of Tumour Volume In Vivo

1Grupo de Química Medicinal, Laboratorio de Química Orgánica, Facultad de Ciencias-Facultad de Química, Universidad de la República, 11400 Montevideo, Uruguay
2Cátedra de Análisis Clínicos, Laboratorio Central—Hospital Maciel (Ministerio de Salud Pública), Facultad de Química, Universidad de la República, 11200 Montevideo, Uruguay
3Departamento de Patobiología, Facultad de Veterinaria, Universidad de la República, 11600 Montevideo, Uruguay
4Department of Biochemistry and Molecular Biology, Faculty of Biology, Institute of Biomedicine of University of Barcelona (IBUB) and IDIBAPS, Unit Associated with CSIC, 08028 Barcelona, Spain
5Departamento de Química Inorgánica y Analítica, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, 83800005 Santiago, Chile
6Centro de Investigaciones en Farmacobiología Aplicada, Universidad de Navarra, 31008 Pamplona, Spain

Received 16 February 2011; Accepted 14 April 2011

Academic Editor: P. Cos

Copyright © 2011 María L. Lavaggi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Phenazine 5,10-dioxides (PDOs) are a new class of bioreductive cytotoxins, which could act towards tumours containing hypoxic regions. The PDOs selective-hypoxic bioreduction was probed in vitro; however, the mechanism of action has not been completely explained. Besides, PDOs in vivo antitumour activities have not been demonstrated hitherto. We study the mechanism of hypoxic/normoxic cytotoxicity of PDO representative members. Electron spin resonance is used to confirm OH production, alkaline comet assay to determine genotoxicity, and gel electrophoresis and flow cytometry to analyze DNA fragmentation and cell cycle distribution. Chemically induced rat breast tumours are employed to evaluate in vivo activities. For the most selective cytotoxin, 7(8)-bromo-2-hydroxyphenazine 5,10-dioxide (PDO1), exclusive hypoxic OH production is evidenced, while for the unselective ones, OH is produced in both conditions (normoxia and simulated hypoxia). In normoxia (Caco-2 cells), PDO1 induces cell-cycle arrest and DNA fragmentation but does not significantly induce apoptosis neither at IC50 nor IC80. No difference in the comet-assay scores are observed in normoxia and simulated hypoxia being the unselective 2-amino-7(8)-bromophenazine 5,10-dioxide (PDO2) the most genotoxic. The in vivo efficacy with the absence of systemic toxicity of PDO1 and PDO2 is checked out. Results from this study highlight the potential of PDOs as new therapeutics for cancer.