Research paper Pentoxifylline as a modulator of anticancer drug doxorubicin. Part II: Reduction of doxorubicin DNA binding and alleviation of its biological effects Grzegorz Golu  nski a , Agnieszka Borowik a , Natalia Derewo  nko b , Anna Kawiak c, d , Michal Rychlowski b , Anna Woziwodzka a, ** , Jacek Piosik a, * a Laboratory of Biophysics, Intercollegiate Faculty of Biotechnology UG-MUG, Abrahama 58, 80-307 Gda nsk, Poland b Laboratory of Virus Molecular Biology, Intercollegiate Faculty of Biotechnology UG-MUG, Abrahama 58, 80-307 Gda nsk, Poland c Division of Plant Protection and Biotechnology, Department of Biotechnology, Intercollegiate Faculty of Biotechnology, University of Gdansk and Medical University of Gdansk, Abrahama 58, 80-307 Gda nsk, Poland d Laboratory of Human Physiology, Medical University of Gdansk, Tuwima 15, 80-210 Gda nsk, Poland article info Article history: Received 4 November 2015 Accepted 2 February 2016 Available online 5 February 2016 Keywords: Cytotoxicity Mutagenicity Cell cycle Confocal microscopy abstract Anticancer drug doxorubicin is commonly used in cancer treatment. However, drug's severe side effects make toxicity reduction important matter. Another biologically active aromatic compound, pentoxifyl- line, can sequester aromatic compounds in stacking complexes reducing their bioactivity. This work deals with the problem of alleviating doxorubicin side effects by pentoxifylline. We employed a wide spectrum of prokaryotic and eukaryotic cellular assays. In addition, we used the doxorubicin-pentoxifylline mixed association constant to quantitatively assess pentoxifylline influence on the doxorubicin mutagenic ac- tivity. Obtained results indicate strong protective effects of pentoxifylline towards doxorubicin, observed on bacteria and human keratinocytes with no such effects observed on the cancer cells. It may be hy- pothesized that, considering much shorter half-life of pentoxifylline than doxorubicin, simultaneous administration of doxorubicin and pentoxifylline will lead to gradual release of doxorubicin from com- plexes with pentoxifylline to reach desired therapeutic concentration. Proposed results shed light on the possible doxorubicin chemotherapy modification and its side effects reduction without the loss of its therapeutic potential. © 2016 Elsevier B.V. and Soci et e Française de Biochimie et Biologie Mol eculaire (SFBBM). All rights reserved. 1. Introduction Cancer is one of the most common life-threatening diseases diagnosed in the modern world. Despite increasing 5-year survival rate (69% in 2003e2009 period compared to 49% in 1975e1979), which may be attributed to improvements in both diagnosis and treatment, almost 1 out of 4 deaths in US is due to cancer (American Cancer Society e Facts and Figures). Because of such a massive death toll searching for more effective cancer therapies appears to be one of the most important challenges of nowadays biomedical sciences. The research progresses in two main directions: devel- oping new anticancer drugs and improving already developed therapies to enhance their effectiveness and/or limit their side effects. Doxorubicin (DOX) is an anticancer drug routinely used in treatment of numerous cancers from leukemia to thyroid cancer [1]. DOX mechanism of action is complex, however three main modes of action may be distinguished: direct interactions with DNA (intercalation) [2], topoisomerase II inhibition [3], and generation of free radicals [4]. As most of anticancer antibiotics, DOX has numerous toxic effects, both systemic and at the injection sites. The latter include tissue necrosis and vein inflammation [1,5,6]. Considering these severe side effects, new, improved methods of DOX administration are constantly under development [7]. Pentoxifylline (PTX) is a synthetic derivative of purine alkaloids e methylxanthines. PTX is broadly used for medicinal purposes Abbreviations: DOX, doxorubicin; PTX, pentoxifylline. * Corresponding author. ** Corresponding author. E-mail addresses: anna.woziwodzka@biotech.ug.edu.pl (A. Woziwodzka), piosik@biotech.ug.edu.pl (J. Piosik). Contents lists available at ScienceDirect Biochimie journal homepage: www.elsevier.com/locate/biochi http://dx.doi.org/10.1016/j.biochi.2016.02.003 0300-9084/© 2016 Elsevier B.V. and Soci et e Française de Biochimie et Biologie Mol eculaire (SFBBM). All rights reserved. Biochimie 123 (2016) 95e102