MOLECULAR CARCINOGENESIS LoVo Colon Cancer Cells Resistant to Oxaliplatin Overexpress c-MET and VEGFR-1 and Respond to VEGF With Dephosphorylation of c-MET Bel  en Mezquita, 1,2 Estela Pineda, 3 Jovita Mezquita, 1 Pau Mezquita, 2 Montserrat Pau, 1 Jordi Codony-Servat, 3 Eva Martínez-Balibrea, 4 Conchi Mora, 5 Joan Maurel, 3 and Cristóbal Mezquita 1 * 1 Departament de Cie `ncies Fisiolo `giques I. Laboratori de Gene `tica Molecular, IDIBAPS, Facultat de Medicina, Universitat de Barcelona, Barcelona, Spain 2 Departament de Cie `ncies Ba ` siques, Universitat Internacional de Catalunya, Barcelona, Spain 3 Medical Oncology Department, Hospital Clı ´nic, University of Barcelona, Barcelona, Spain 4 Medical Oncology Service, Institut Catala ` d’Oncologia-Hospital Germans Trias i Pujol, Badalona, Spain 5 Departament de Medicina Experimental, Universitat de Lleida, Alcalde Rovira Roure, Lleida, Spain Oxaliplatin-resistant LoVo colon cancer cells overexpressing c-MET and VEGFR-1 were selected to study several signaling pathways involved in chemoresistance, as well as the effect of increasing amounts of VEGF in the regulation of c-MET. In comparison with chemosensitive LoVo colon cancer cells, oxaliplatin-resistant cells (LoVoR) overexpress and phosphorylate c-MET, upregulate the expression of transmembrane and soluble VEGFR-1 and, unexpectedly, downregulate VEGF. In addition, LoVoR cells activate other transduction pathways involved in chemoresistance such as Akt, b-catenin-TCF4 and E-cadherin. While c-MET is phosphorylated in LoVoR cells expressing low levels of VEGF, c-MET phosphorylation decreases when recombinant VEGF is added into the culture medium. Inhibition of c-MET by VEGF is mediated by VEGFR-1, since phosphorylation of c-MET in the presence of VEGF is restored after silencing VEGFR-1. Dephosphorylation of c-MET by VEGF suggests that tumors coexpressing VEGFR-1 and c-MET may activate c-MET as a result of anti-VEGF therapy. © 2015 Wiley Periodicals, Inc. Key words: chemoresistance; VEGFR-1/c-MET; b-catenin-TCF4E; LoVo colon cancer cells INTRODUCTION Colorectal cancer is one of the most common cancers and the second-leading cause of cancer- related deaths in the western world [1]. Nearly 50% of colon cancer patients show recurrence of the disease [1]. Oxaliplatin (1,2-diaminocyclohexane- oxalate platinum) is a third-generation platinum compound with activity in colon cancer [2]. Ox- aliplatin and infusional fluorouracil (FU) combina- tion have significantly longer progression free survival (PFS) and better response rate when com- pared to FU alone in metastatic colorectal cancer (mCRC) [3]. One of the current standard schedules in first-line therapy in mCRC is the combination of FOLFOX (fluorouracil/folinic acid plus oxaliplatin) or XELOX (capecitabine plus oxaliplatin) plus bevacizumab [4]. Despite of this, the median PFS is only between 9–10 months and acquired resistance to both anti-VEGF therapy (bevacizumab) and chemotherapy is almost universal [4]. The mechanisms involved in oxaliplatin resistance are poorly understood. Chronic exposure to oxalipla- tin induces different gene expression patterns in several colorectal cancer cell lines [5,6]. Despite the heterogeneity of the response to oxaliplatin, the study of induced signaling pathways by prolonged oxali- platin exposure in vitro may reveal novel molecular targets for therapeutic intervention to restore sensi- tivity to chemotherapy. c-MET is a receptor tyrosine kinase activated by its natural ligand hepatocyte growth factor (HGF) [7]. Signaling through HGF/c-MET is essential for prolif- eration, migration and tissue regeneration. This signaling pathway is upregulated in human cancers and contributes to disease progression, metastasis and resistance to treatment [8–11]. Transgenic mice over- expressing c-MET display a tumorigenic and meta- static phenotype [12,13]. Overexpression of c-MET and increased production of HGF have been related to aggressive tumor growth as well as poor therapeutic outcome [14]. c-MET overexpression has further been associated with a chemoresistant phenotype [15–18]. For these reasons it is interesting to study the Conflicts of interest: None. *Correspondence to: Cristóbal Mezquita, Departament de Ciències Fisiològiques I, Facultat de Medicina, Universitat de Barcelona, Casanova 143, 08036 Barcelona, Spain. Received 17 July 2014; Revised 5 December 2014; Accepted 18 December 2014 DOI 10.1002/mc.22289 Published online in Wiley Online Library (wileyonlinelibrary.com). ß 2015 WILEY PERIODICALS, INC.