Stressed Jerusalem artichoke tubers (Helianthus tuberosus L.) excrete a protein fraction with specific cytotoxicity on plant and animal tumour cell B. Griffaut a , E. Debiton b,c,d , J.C. Madelmont b,c,d , J.C. Maurizis b,c,d , G. Ledoigt a, ⁎ a EA 3296 ERTAC, « Tumeurs et Autosurveillance Cellulaire », Université Blaise-Pascal (Clermont-Ferrand II), campus des Cézeaux, 24 avenue des Landais, 63177 Aubière cedex, France b Univ. d’Auvergne, UFR Pharmacie, Laboratoire de Pharmacognosie-Biotechnologies, Clermont-Ferrand, F-63001 France c Inserm, U484, Clermont-Ferrand, F-63005 France d Centre Jean Perrin, Clermont-Ferrand, F-63011 France Received 7 May 2007; received in revised form 15 June 2007; accepted 15 June 2007 Available online 28 June 2007 Abstract Wounds from Jerusalem artichoke (Helianthus tuberosus L.) tubers excrete bioactive metabolites from a variety of structural classes, including proteins. Here we describe a protein specifically active against tumour cells arising either from human, animal or plant tissues. The non-tumour animal cells or the plant callus cells are not sensitive to these excreta. The active product was only obtained after a wound-drought stress of plant tubers. The cytotoxicity varies according to the tumour cell type. For instance, some human tumour cell lines and especially the human mammary tumour cells MDA-MB-231 were shown to be very susceptible to the active product. The active agent is shown to contain an 18-kDa polypeptide with homology to a superoxide dismutase (SOD). A 28-kDa polypeptide, related to an alkaline phosphatase (AP), was shown to be tightly linked to this 18-kDa polypeptide. The excreted 28-kDa polypeptide also displayed a consensus sequence similar to the group of DING proteins, but with a smaller molecular weight. The superoxide dismutase polypeptide was shown to be involved in the antitumour activity, but the presence of smaller factors (MW b 10 kDa), such as salicylic acid, can enhance this activity. © 2007 Elsevier B.V. All rights reserved. Keywords: Helianthus tuberosus; Plant stress; Superoxide dismutase; Alkaline phosphatase; Tumour 1. Introduction Stress can induce defence factors in plants that can be secreted [1]. Tumour tissues trigger a stress physiology in plants [2]. In contrast to animal cancer, plant tumours cannot spread in the plant organism and grow in the same place, under the control of plant. Therefore, specific defence factors may exist to limit the tumour tissue expansion. Thus, our aim was to reveal the intervention of new specific defence factors that would be involved in tumour tissue monitoring. The plant’s defence system contains reactive oxygen species (ROS) which are aggressive products that elicit a wide spectrum of responses [3]. These responses depend upon the severity of the damage, which is further influenced by the cell type, the magnitude of the dose, and the duration of the exposure. Typically, low dose, particularly hydrogen peroxide, are mitogenic and promote cell proliferation, while intermediate doses result in either temporary or permanent growth arrest, such as replicative senescence. Very severe oxidative stress ultimately causes cell death via either apoptotic or necrotic mechanisms [4]. Cells are equipped with enzymatic antioxidative mechanisms that play an important role in the elimination of free radicals. Superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidases are involved in the removal of superoxide and hydrogen peroxide (H 2 O 2 ). SOD catalyses the reduction of superoxide into H 2 O 2 [5]. After a stimulus, plants can synthesize and secrete a large variety of products. Previously, we have shown that wound and desiccation of plant tubers allowed the secretion of cytokinin- like products, which can show a cytotoxic feature according to their molecular structures [6]. Moreover, potato tuber parench- yma was shown to excrete new types of protease inhibitors after this type of stress [7]. Biochimica et Biophysica Acta 1770 (2007) 1324 – 1330 www.elsevier.com/locate/bbagen ⁎ Corresponding author. Tel.: +33 04 73 40 79 08; fax: +33 04 73 40 79 42. E-mail address: Gerard.LEDOIGT@ertac.univ-bpclermont.fr (G. Ledoigt). 0304-4165/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.bbagen.2007.06.007