Short communication Apoptotic mechanisms of the biotechnologically produced arylnaphtalene lignan justicidin B in the acute myeloid leukemia-derived cell line HL-60 Georgi Momekov a, *, Deyan Yossifov a , Margarita Guenova b , Albena Michova b,c , Nikolay. Stoyanov b , Spiro Konstantinov a , Todor Ionkov d , Pavlina Sacheva e , Iliana Ionkova e a Department of Pharmacology, Pharmacotherapy and Toxicology, Faculty of Pharmacy, Medical University of Sofia, Sofia, Bulgaria b Laboratory of Haematopathology and Immunology, National Specialised Hospital for Active Treatment of Haematological Diseases, Sofia, Bulgaria c Department of Immunology, National Center of Infectious and Parasitic Diseases, Sofia, Bulgaria d Department of Automation, Faculty of Automatics, Technical University of Sofia, Sofia, Bulgaria e Department of Pharmacognosy, Faculty of Pharmacy, Medical University of Sofia, Sofia, Bulgaria Introduction Lignans encompass an important class of secondary plant metabolites, which have drawn much attention since the discovery of the aryltetralin lignan podophyllotoxin, the establishment of its potent cytotoxic effects and the successful commercialization of its semisynthetic derivatives etoposide and teniposide [1–3]. These agents represent an important class of antineoplastic agents used for the chemotherapy of Hodgkin’s disease, small cell lung cancer and testicular cancer, etc. [4,5]. The large-scale semisynthetic production of etoposide and teniposide relies solely on naturally occurring podophyllotoxin as starting material [2]. The latter is extracted from the rhizomes of Podophyllum peltatum and Podophyllum hexandrum (Berberidaceae), which, however are becoming increasingly limited due to extensive over-exploitation [2]. On this basis, much effort has been focused on the search for alternative sources of podophyllotoxin, including identification of alternative plant sources, and elaboration of Pharmacological Reports 66 (2014) 1073–1076 A R T I C L E I N F O Article history: Received 6 December 2013 Received in revised form 18 June 2014 Accepted 18 July 2014 Available online 2 August 2014 Keywords: Justicidin B Cytotoxicity Apoptosis HL-60 Caspases A B S T R A C T Background: The present study aimed at optimization of the biotechnological production of the lignan justicidin B by genetically transformed cultures of Linum leonii and the pharmacological evaluation of the pro-apoptotic effects of the compound in HL-60 cells. Methods: A rapidly growing selected root line of L. leonii was grown in 2-L bioreactor for period of 40 days and the protocols for obtaining of the compound have been optimized. The pharmacological study included evaluation of the cytotoxicity of the compound in HL-60 cells (MTT-assay), its apoptogenic effects and its effects on caspase 3,8 and 9 activation. Results: After 40 days of sterile run scale up of hairy root culture in bioreactor, 27.2 g/L dry weight of root biomass was harvested from the bioreactor culture vessel, recording about nine times increase over initial inoculum (3.0 g), with 1.55%  0.07 Justicidin B, greater than yields from 300 ml flasks. Our findings are the first work toward the scale up of L. leonii hairy roots-based biotechnological production of Justicidin B, employing bioreactors for high biomass production to meet the industrial requirement. The results from the pharmacological evaluation have shown that the tested arylnaphtalene lignan is a potent cytotoxic and proapoptotic agent against HL-60. The induction of apoptosis proceeds via activation of the intrinsic mitochondrial cell-death signaling pathways. Conclusion: The potent activity at low micromolar concentration and the feasibility of biotechnological production of justicidin B implies that there is enormous scope in its further evaluation as possible antineoplastic drug candidate. ß 2014 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved. * Corresponding author. E-mail addresses: gmomekov@gmail.com, gmomekov@cetrh.org (G. Momekov). Contents lists available at ScienceDirect Pharmacological Reports jou r nal h o mep ag e: w ww .elsevier .co m /loc ate/p h arep http://dx.doi.org/10.1016/j.pharep.2014.07.005 1734-1140/ß 2014 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved.