An elongation factor-like protein (EF-Tu) elicits a humoral response in infiltrating ductal breast carcinomas: An immunoproteomics investigation Bechr Hamrita a, 1 , Hela Ben Nasr a, 1 , Philippe Hammann b , Lauriane Kuhn b , Christelle-Lemaitre Guillier c , Anouar Chaieb a, d , Hedi Khairi a, d , Karim Chahed a, e, ⁎ a Laboratoire d'Immuno-Oncologie Moléculaire, Faculté de Médecine de Monastir, Tunisia b Plate Forme Protéomique, Institut de Biologie Moléculaire et Cellulaire, CNRS, 67084 Strasbourg, France c UMR INRA/CNRS/Université de Bourgogne, Plante Microbe Environnement (PME), France d Service d'Obstétrique et des maladies féminines, Centre Hospitalo-Universitaire-Farhat-Hached, Sousse, Tunisia e Faculty of Sciences, Sfax, Tunisia abstract article info Article history: Received 25 March 2011 Received in revised form 30 May 2011 Accepted 1 June 2011 Available online 17 June 2011 Keywords: Autoantibody Elongation factor Tu Infiltrating ductal breast carcinomas Immunoproteomics SERPA Objectives: In the current study, we have used an immunoproteomics approach to identify proteins that commonly elicit a humoral response in patients with infiltrating ductal carcinomas of the breast. Design and methods: Sera obtained at the time of diagnosis from 40 patients with invasive breast cancer and 42 healthy controls were screened for the presence of IgG antibodies to MCF-7 cell line proteins using a serological proteomics-based approach. Results: An immunoreactive protein detected in sera from 21 of 40 patients was isolated and subsequently identified as elongation factor-Tu. Conclusions: The immunoproteomic approach implemented here offers a powerful tool for determining novel tumor antigens that induce a humoral immune response in cancer patients. From our findings, the immunoreactive EF-Tu protein and/or the related circulating antibodies may display clinical usefulness as potential diagnostic markers and provide a means for a better understanding of the molecular mechanisms underlying breast cancer development. © 2011 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved. 1. Introduction Breast cancer remains one of the leading causes of death among women worldwide. The incidence rate of this malignancy is steadily rising in developing countries. In Tunisia, the incidence of breast cancer is approximately 19 new cases per 100,000 women per year [1]. Invasive carcinomas where the basement membrane is totally or partially destroyed represent 70–80% of all breast cancer. Among these, infiltrating ductal carcinomas (IDCA) are the most aggressive forms and have a poor prognosis. Up to now, poor diagnosis of breast cancer is due in great part to a lack of specific biomarkers of this disease. In addition to CA 15–3 and CA 27.29 which are used clinically as serum markers for detection of breast cancer, other breast tumor biomarkers have been recently identified [2]. Among these, the most extensively investigated circulating biomarkers include MAGE family members, NY-ESO-1, HER-2/neu, MUC1, mutant p53 and c-myc [3]. Unfortunately, depending on the stage and histology of disease, the percentage of breast cancer patients who have elevated serum protein levels of any one of the above markers is less than 36%, and combination of these markers ranges from 20% to 73%. As such, the clinical application of these markers is limited when assayed indepen- dently, although using combinations of markers has somewhat enhanced diagnostic value. Actually, there is much interest in identifying useful bio-markers that can help not only in detection but also for typing and treatment [4]. Currently, the search for specific cancer-related alterations largely focus upon clinically relevant biologically fluids such as serum which may contain at very low levels peptides or proteins that are aberrantly shed or secreted from necrotic or apoptotic cells in response to a disease. Interestingly, tumor antigens released in the bloodstream by cancer cells may induce a humoral immune response and generate autoanti- bodies that could be useful for cancer screening, diagnosis, as well as, in immunotherapy [5]. Although the mechanisms by which these antigens elicit autoantibody formation in cancer remain largely unknown, the Clinical Biochemistry 44 (2011) 1097–1104 Abbreviations: 2-DE, two-dimensional gel electrophoresis; 2D-blotting, western blotting following 2-DE; IDCA, infiltrating ductal carcinoma; MALDI-TOF-MS, matrix assisted laser desorption/ionization time of flight mass spectrometry; PVDF, poly- vinylidene difluoride; SERPA, serological proteome analysis. ⁎ Corresponding author at: Laboratoire d'Immuno-Oncologie Moléculaire, Faculté de Médecine de Monastir, 5019 Monastir, Tunisia. Fax: +216 73 230 932. E-mail address: k.chahed@yahoo.fr (K. Chahed). 1 Bechr Hamrita and Hela ben Nasr contributed equally to the study. 0009-9120/$ – see front matter © 2011 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved. doi:10.1016/j.clinbiochem.2011.06.005 Contents lists available at ScienceDirect Clinical Biochemistry journal homepage: www.elsevier.com/locate/clinbiochem