Journal of Steroid Biochemistry & Molecular Biology 113 (2009) 163–170 Contents lists available at ScienceDirect Journal of Steroid Biochemistry and Molecular Biology journal homepage: www.elsevier.com/locate/jsbmb 8-Prenylnaringenin inhibits epidermal growth factor-induced MCF-7 breast cancer cell proliferation by targeting phosphatidylinositol-3-OH kinase activity Elisa Brunelli a , Giulia Pinton a , Federica Chianale b , Andrea Graziani b , Giovanni Appendino a , Laura Moro a,∗ a Dipartimento di Scienze Chimiche, Alimentari, Farmaceutiche e Farmacologiche and Drug and Food Biotechnology Center, Università degli Studi del Piemonte Orientale “Amedeo Avogadro”, 28100 Novara, Italy b Dipartimento di Scienze Mediche, Università degli Studi del Piemonte Orientale “Amedeo Avogadro”, 28100 Novara, Italy article info Article history: Received 9 May 2008 Received in revised form 20 November 2008 Accepted 25 November 2008 Keywords: 8-Prenylnaringenin EGFR receptor Breast cancer Signalling abstract 8-Prenylnaringenin (8PN), one of the strongest plant-derived oestrogen receptors (ERs) ligand, has been suggested to have potential cancer chemo-preventive activities and anti-angiogenic properties. Because published data suggest that ERs serve as nodal point that allows interactions between hormones and growth factors mediated pathways, we decided to investigate the effects exerted by 8PN on Epidermal growth factor (EGF)-elicited pathways in breast cancer cells. Here we show that in ER positive MCF-7 cells, 8PN interferes with EGF induced cell proliferation by strongly inhibiting activation of PI(3)K/Akt pathway, without affecting EGFR expression or tyrosine phosphorylation, and exerting a synergistic activation of Erk1/2 phosphorylation. Moreover, we demonstrate that 8PN is a direct inhibitor of PI(3)K activity as it is shown by in vitro experiments with the purified enzyme and by its inability to impair serine phosphorylation of a constitutive active form of Akt. These findings suggest that inhibition of PI(3)K is a novel mechanism which contributes to 8PN activity to inhibit cancer cell survival and EGF induced proliferation. © 2008 Elsevier Ltd. All rights reserved. 1. Introduction Accumulated evidence in the last few years indicates chemo- prevention as a valuable strategy to either prevent or impair cancer progression [1]. Among chemo-preventive chemicals, natural non- toxic products (or their synthetic analogs), in particular dietary components, have been under scrutiny for their potential to halt or reverse the development or progression of cancer [2]. Studies of several compounds of plant origin, especially the flavonoids, sug- gest that these molecules can harbour cancer chemo-preventive and/or therapeutic activities. Flavonoids are a group of con- stituents of food and drinks commonly consumed by humans, that includes compounds of different chemical classes such as flavones (7,8-benzoflavone), flavonols (quercetin), flavanol (cathechin), Abbreviations: PI, phosphatidylinositol; PI(4,5)P2, phosphatidylinositol-(4,5)- bis-phosphate; PI(3,4,5)P3, phosphatidylinositol-(3,4,5)-tris-phosphate; PI(3)K, phosphatidylinositol-3-OH kinase; PS, phosphatidylserine. ∗ Corresponding author at: Dipartimento di Scienze Chimiche, Alimentari, Far- maceutiche e Farmacologiche Università degli Studi del Piemonte Orientale “A. Avogadro”, Via Bovio 6, 28100 Novara, Italy. Tel.: +39 0321 375820; fax: +39 0321 375821. E-mail address: moro@pharm.unipmn.it (L. Moro). flavanones (naringenin), isoflavones (genistein), and chalcones (xanthohumol) [3]. Among flavonoids, 8-prenylnaringenin (8PN) has been identified as the estrogenic principle of the hop plant (Humulus lupulus L.), that is largely used in the brewing industry as a preservative and flavouring agent to add bitterness and aroma to beer [4]. While the biological effects of the dietary exposure to 8PN are substantially unknown, several intriguing observations have been done regarding its activity at cellular level [5–7]. 8PN is one of the strongest plant-derived estrogenic compounds identified to date. 8PN has been shown to compete strongly with oestradiol for binding to both oestrogen receptor (ER)  and  with a rela- tive binding affinity of about 0.01 (oestradiol = 1), ten times higher than that of the archetypal phytoestrogen genistein [8,9]. ER and ER, belong to the steroid/thyroid hormone family of transcription factors and mediate most of the biological effects of estrogens, by interacting with the transcription machinery [10–13]. Moreover, a small fraction of ERs is associated with the plasma membrane and through concerted activation of the MAP kinase and the PI(3)K/Akt signalling pathways, contribute to regulate cell proliferation and prevent apoptosis [14–20]. In particular, the activation of PI(3)K and the generation of PI(3,4,5)P 3 are both necessary for the phosphory- lation on Thr-308 and Ser-473 of Akt/PKB, a downstream mediator of PI(3)K signalling [21–24]. In different cell types, Akt/PKB has been 0960-0760/$ – see front matter © 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.jsbmb.2008.11.013