Molecular Cell Biology The Endosomal Protein CEMIP Links WNT Signaling to MEK1–ERK1/2 Activation in Selumetinib-Resistant Intestinal Organoids Hong Quan Duong 1,2,3,4 , Ivan Nemazanyy 5 , Florian Rambow 6 , Seng Chuan Tang 1,2 , Sylvain Delaunay 1,7 , Lars Tharun 8 , Alexandra Florin 8 , Reinhard B€ uttner 8 , Daniel Vandaele 9 , Pierre Close 1,7 , Jean-Christophe Marine 6 , Kateryna Shostak 1,2 , and Alain Chariot 1,2,10 Abstract MAPK signaling pathways are constitutively active in colon cancer and also promote acquired resistance to MEK1 inhibition. Here, we demonstrate that BRAF V600E -mutated colorectal cancers acquire resistance to MEK1 inhibition by inducing expression of the scaffold protein CEMIP through a b-catenin– and FRA-1–dependent pathway. CEMIP was found in endosomes and bound MEK1 to sustain ERK1/2 activation in MEK1 inhibitor–resistant BRAF V600E -mutated colorectal cancers. The CEMIP-dependent pathway main- tained c-Myc protein levels through ERK1/2 and provided metabolic advantage in resistant cells, potentially by sus- taining amino acids synthesis. CEMIP silencing circum- vented resistance to MEK1 inhibition, partly, through a decrease of both ERK1/2 signaling and c-Myc. Together, our data identify a cross-talk between Wnt and MAPK signaling cascades, which involves CEMIP. Activation of this pathway promotes survival by potentially regulating levels of specific amino acids via a Myc-associated cascade. Targeting this node may provide a promising avenue for treatment of colon cancers that have acquired resistance to targeted therapies. Significance: MEK1 inhibitor–resistant colorectal cancer relies on the scaffold and endosomal protein CEMIP to main- tain ERK1/2 signaling and Myc-driven transcription. Cancer Res; 78(16); 4533–48. Ó2018 AACR. Introduction Colorectal cancer is the second leading cause of death from cancer in Western countries and arises from a variety of genetic alterations that result in the constitutive activation of both Wnt- and ErbB-dependent oncogenic signaling pathways. Among the underlying genetic alterations are loss-of-function mutations of the adenomatous polyposis coli (APC) gene, which leads to b-catenin activation and constitutive Wnt signaling, followed by gain-of-function mutations in KRAS or BRAF proto-oncogenes (1). RAS signals though the RAF Ser/Thr kinase family and triggers the subsequent activation of the mitogen-activated protein/extra- cellular signal–regulated kinase 1 and 2 (MEK1/2) as well as the extracellular signal–regulated kinase 1 and 2 (ERK1/2). This signaling cascade gained significant attention due to the high frequency of KRAS and BRAF mutations found in human cancers (2, 3). Indeed, activating mutations of KRAS are found in 40% of advanced colorectal cancer (4). In addition, the BRAF valine 600 (BRAF V600E ) mutation, which leads to constitutive activation of BRAF, is found in approximately 11% of colorectal cancers and confers poor prognosis (5–7). As the pharmacologic inhibition of KRAS remains challenging, alternative approaches targeting downstream RAS effectors (RAF and MEK1) have been proposed but were poorly effective in monotherapy for the treatment of colorectal cancer, largely because of a feedback reactivation of MAPK signaling (8, 9). This reactivation occurs through the amplification of the driving oncogene KRAS or BRAF in colorectal cells treated with MEK1 inhibitors (10, 11). Other mechanisms involve the EGFR/HER1–dependent reactivation of MAPK in BRAF V600E -mutated colorectal cancer cells treated with a BRAF inhibitor (12, 13). Similarly, MAPK reactivation in KRAS-mutated colorectal cancer cells subjected to MEK1 inhibition also results from the induction of HER3 (14). Clinical trials in which RAF and EGFR or RAF and MEK are cotargeted to suppress the feedback reactivation of MAPK signaling were carried out but patients 1 Interdisciplinary Cluster for Applied Genoproteomics (GIGA), GIGA-Molecular Biology of Diseases, University of Liege, CHU, Sart-Tilman, Li ege, Belgium. 2 Laboratory of Medical Chemistry, University of Liege, CHU, Sart-Tilman, Liège, Belgium. 3 Institute of Research and Development, Duy Tan University, Quang Trung, Danang, Vietnam. 4 Department of Cancer Research, Vinmec Research Institute of Stem Cell and Gene Technology, Hanoi, Vietnam. 5 Paris Descartes University, Sorbonne Paris Cite, Paris, France. 6 Laboratory for Molecular Cancer Biology, VIB Center for Cancer Biology and KULeuven Department of Oncology, Leuven, Belgium. 7 Institute for Pathology, University Hospital Cologne, Cologne, Germany. 8 Laboratory of Cancer Signaling, University of Liege, Li ege, Belgium. 9 Gastroenterology Department, University of Liege, CHU, Sart-Tilman, Li ege, Belgium. 10 Walloon Excellence in Life Sciences and Biotechnology (WELBIO), Wallonia, Belgium. Note: Supplementary data for this article are available at Cancer Research Online (http://cancerres.aacrjournals.org/). K. Shostak and A. Chariot contributed equally to this article. Corresponding Author: Alain Chariot, Laboratory of Medical Chemistry, GIGA Molecular Biology of Diseases, Tour GIGA, þ2 B34, Sart-Tilman, University of Li ege, Li ege 4000, Belgium. Phone: 32-043662472; Fax: 32-043664534; E-mail: Alain.chariot@uliege.be. doi: 10.1158/0008-5472.CAN-17-3149 Ó2018 American Association for Cancer Research. Cancer Research www.aacrjournals.org 4533 Downloaded from http://aacrjournals.org/cancerres/article-pdf/78/16/4533/2774008/4533.pdf by guest on 20 June 2022