MUC1/KL-6 expression confers an aggressive phenotype upon myeloma cells Shinya Endo a, 1 , Nao Nishimura a, 1 , Yawara Kawano a , Niina Ueno a , Shikiko Ueno a , Hiro Tatetsu a , Yoshihiro Komohara b , Motohiro Takeya b , Hiroyuki Hata c , Hiroaki Mitsuya a , Matsuoka Masao a , Yutaka Okuno a, * a Departments of Hematology, Rheumatology, and Infectious Disease, Kumamoto University Graduate School of Medicine, 1-1-1 Honjo, Chuo-ku, Kumamoto, 860-8556, Japan b Department of Cell Pathology, Graduate School of Medical Sciences, Kumamoto University, 1-1-1 Honjo, Kumamoto, 860-8556, Japan c Division of Informative Clinical Sciences, Faculty of Medical Sciences, Kumamoto University, Kumamoto, Japan article info Article history: Received 25 October 2018 Accepted 4 November 2018 Available online xxx Keywords: Myeloma MUC1 KL-6 EMM1 Apoptosis abstract The sialic glycoprotein, MUC1 , is known to be involved in the pathogenesis of various types of cancers. KL-6 is one of the surface antigens of MUC1 and also a marker of interstitial pneumonitis. A fraction of patients with myeloma (3.9%) have elevated serum KL-6 levels without any evidence of interstitial pneumonitis and their myeloma cells have high MUC1 expression. We established a myeloma cell line designated EMM1 from a patient with multiple myeloma accompanied with elevated serum KL-6. EMM1 cells expressed high levels of MUC1 compared with other myeloma cell lines. Knockdown of MUC1 in EMM1 cells induced cell cycle arrest during S phase and apoptosis, suggesting that the MUC1 expression is involved in accelerated growth of EMM1 cells. RNA-seq analysis suggests that MUC1 expression ac- tivates k-ras and TNFa-induced NFkB pathways in EMM1 cells. We injected EMM1 cells subcutaneously into Rag2 / Jak3 / Balb/c mice to establish a mouse xenograft model. These mice had aggressive tumor growth that was accompanied by high serum KL-6 levels. In addition, MUC1 knockdown in EMM1 cells led to inhibited tumor growth. These findings demonstrate that MUC1 serves as a potential target for developing drugs for treatment of patients with KL-6 þ myeloma, and EMM1 cells and EMM1-engrafted mice are useful tools for the development of such novel agents. © 2018 Elsevier Inc. All rights reserved. 1. Introduction Multiple myeloma is a malignancy of antibody-producing plasma cells and often emerges in elderly people. There are many novel agents for treating myeloma, including the proteasome in- hibitors bortezomib, carfilzomib, and ixazomib; the immunomod- ulatory drugs thalidomide, lenalidomide, and pomalidomide; the histone deacetylase (HDAC) inhibitor panobinostat; and the anti- bodies elotuzumab and daratumumab [1]. Although these novel agents improve overall survival of patients with myeloma, they fail to induce a complete cure, and effective novel drugs are therefore required to eradicate myeloma cells. MUC1 (Mucin 1, cell surface associated) is an oncogene that is involved in many types of cancers [2,3]. MUC1 is cleaved into subunits designated MUC1-N and MUC1-C that form a heterodimer that contributes to the regulation of cell growth, self-renewal, tis- sue invasion, and apoptosis of cancer cells [2]. MUC1 is highly expressed in epithelial tumors and hematological malignancies, including acute myeloid leukemia and multiple myeloma. KL-6 (Krebs von den Lungen-6) is one of the surface antigens of MUC1 that is recognized by an anti-KL-6 antibody and also known as a diagnostic marker of interstitial pneumonitis. The C-terminal sub- unit MUC1-C comprises an extracellular domain of 58 amino acid residues, a transmembrane domain, and an intracellular domain of 72 amino acid residues. The intracellular domain possesses onco- genic properties. Inhibitors of MUC1-C induce increased the pro- duction of reactive oxygen species and apoptosis of AML and myeloma cells in vitro as well as in mouse xenograft models [3]. There are several reports of myeloma patients with elevated serum KL-6 levels [4e6]. We describe here the establishment of a * Corresponding author. E-mail address: yokuno@gpo.kumamoto-u.ac.jp (Y. Okuno). 1 S.E. and N.N. share co-first authorship. Contents lists available at ScienceDirect Biochemical and Biophysical Research Communications journal homepage: www.elsevier.com/locate/ybbrc https://doi.org/10.1016/j.bbrc.2018.11.016 0006-291X/© 2018 Elsevier Inc. All rights reserved. Biochemical and Biophysical Research Communications xxx (xxxx) xxx Please cite this article as: S. Endo et al., MUC1/KL-6 expression confers an aggressive phenotype upon myeloma cells, Biochemical and Biophysical Research Communications, https://doi.org/10.1016/j.bbrc.2018.11.016