molecules Article Differential Response of Two Human Breast Cancer Cell Lines to the Phenolic Extract from Flaxseed Oil † Angela Sorice 1 , Eliana Guerriero 1,‡ , Maria Grazia Volpe 2,‡ , Francesca Capone 1,‡ , Francesco La Cara 3 , Gennaro Ciliberto 4 , Giovanni Colonna 5, * and Susan Costantini 1, * 1 CROM, Istituto Nazionale Tumori “Fondazione G. Pascale”-IRCCS, Napoli 80131, Italy; a.sorice@istitutotumori.na.it (A.S.); e.guerriero@istitutotumori.na.it (E.G.); f.capone@istitutotumori.na.it (F.C.) 2 Istituto di Scienze dell'Alimentazione, CNR, Avellino 83100, Italy; mgvolpe@isa.cnr.it 3 Istituto di Biologia Agro-ambientale e Forestale, CNR, UOS di Napoli, Napoli 80131, Italy; francesco.lacara@cnr.it 4 Direttore Scientifico, Istituto Nazionale Tumori “Fondazione G. Pascale”-IRCCS, Napoli 80131, Italy; g.ciliberto@istitutotumori.na.it 5 Servizio di Informatica Medica, Azienda Ospedaliera Universitaria, Seconda Università di Napoli, Napoli 80138, Italy * Correspondence: giovanni.colonna@unina2.it (G.C.); s.costantini@istitutotumori.na.it (S.C.); Tel.: +39-081-566-6574 (G.C.); +39-082-519-11729 (S.C.) † Dedicated to the birth of Mattia Evangelista with wishes for a long and peaceful life. ‡ These authors contributed equally to this work. Academic Editor: Derek J. McPhee Received: 30 January 2016 ; Accepted: 2 March 2016 ; Published: 8 March 2016 Abstract: Many studies have evidenced that the phenolic components from flaxseed (FS) oil have potential health benefits. The effect of the phenolic extract from FS oil has been evaluated on two human breast cancer cell lines, MCF7 and MDA-MB231, and on the human non-cancerous breast cell line, MCF10A, by SRB assay, cellular death, cell cycle, cell signaling, lipid peroxidation and expression of some key genes. We have evidenced that the extract shows anti-proliferative activity on MCF7 cells by inducing cellular apoptosis, increase of the percentage of cells in G0/G1 phase and of lipid peroxidation, activation of the H2AX signaling pathway, and upregulation of a six gene signature. On the other hand, on the MDA-MB2131 cells we verified only an anti-proliferative activity, a weak lipid peroxidation, the activation of the PI3K signaling pathway and an up-regulation of four genes. Overall these data suggest that the extract has both cytotoxic and pro-oxidant effects only on MCF7 cells, and can act as a metabolic probe, inducing differences in the gene expression. For this purpose, we have performed an interactomic analysis, highlighting the existing associations. From this approach, we show that the phenotypic difference between the two cell lines can be explained through their differential response to the phenolic extract. Keywords: flaxseed; phenolic extract; breast cancer cell lines; gene regulation 1. Introduction Recent independent findings have assessed that dietary phenols have been shown to possess anti-cancer properties by acting as key modulators of signaling pathways and, therefore, they can be considered as chemo-preventive agents [1,2]. This is supported by epidemiological studies, which suggest that a high consumption of plant derived foods decreases the incidence rates of various cancers [1,2]. However, the cellular mechanisms by which the phenols elicit these anti-cancer effects are multifaceted because they include the regulation of growth factor-receptor interaction and the cell signaling cascades such as the altering of the redox state of the cell, which modulate Molecules 2016, 21, 319; doi:10.3390/molecules21030319 www.mdpi.com/journal/molecules