Oncogenic transformation of NIH/3T3 cells by the overexpression of L-type amino acid transporter 1, a promising anti-cancer target

// Natsumi Hayashi 1 , 2 , * , # , Akitaka Yamasaki 2 , 3 , * , # , Shiho Ueda 2 , Shogo Okazaki 4 , Yoshiya Ohno 5 , Toshiyuki Tanaka 5 , Yuichi Endo 6 , Yoshihisa Tomioka 3 , Kazue Masuko 2 , Takashi Masuko 2 , 6 and Reiko Sugiura 1 1 Laboratory of Molecular Pharmacogenomics, Faculty of Pharmacy, Kindai University, Higashiosaka-Shi, Osaka, Japan 2 Cell Biology Laboratory, School of Pharmacy, Kindai University, Osaka, Japan 3 Laboratory of Oncology Pharmacy Practice and Science, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai-Shi, Miyagi, Japan 4 Division of Cell Fate Regulation, Research Institute for Biomedical Sciences, Tokyo University of Science, Noda-shi, Chiba, Japan 5 Laboratory of Immunobiology, Department of Pharmacy, School of Pharmacy, Hyogo University of Health Sciences, Kobe-Shi, Hyogo, Japan 6 Natural Drug Resources, Faculty of Pharmacy, Kindai University, Osaka, Japan * Co-first authors # This laboratory (April, 2000~) was closed at the end of March, 2020, after the mandatory retirement of Takashi Masuko Correspondence to: Takashi Masuko, email: masuko@phar.kindai.ac.jp Keywords: CD98; LAT1; monoclonal antibody; NIH/3T3; oncogenicity Received: April 26, 2021     Accepted: May 26, 2021     Published: June 22, 2021 Copyright: © 2021 Hayashi et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. ABSTRACT L-type amino acid transporter 1 (LAT1)/SLC7A5 is the first identified CD98 light chain disulfide linked to the CD98 heavy chain (CD98hc/SLC3A2). LAT1 transports large neutral amino acids, including leucine, which activates mTOR, and is highly expressed in human cancers. We investigated the oncogenicity of human LAT1 introduced to NIH/3T3 cells by retrovirus infection. NIH/3T3 cell lines stably expressing human native (164C) or mutant (164S) LAT1 (naLAT1/3T3 or muLAT1/3T3, respectively) were established. We confirmed that endogenous mouse CD98hc forms a disulfide bond with exogenous human LAT1 in naLAT1/3T3, but not in muLAT1/3T3. Endogenous mouse CD98hc mRNA increased in both naNIH/3T3 and muLAT1/3T3, and a similar amount of exogenous human LAT1 protein was detected in both cell lines. Furthermore, naLAT1/3T3 and muLAT1/3T3 cell lines were evaluated for cell growth-related phenotypes (phosphorylation of ERK, cell-cycle progression) and cell malignancy-related phenotypes (anchorage-independent cell growth, tumor formation in nude mice). naLAT1/3T3 had stronger growth- and malignancy- related phenotypes than NIH/3T3 and muLAT1/3T3, suggesting the oncogenicity of native LAT1 through its interaction with CD98hc. Anti-LAT1 monoclonal antibodies significantly inhibited in vitro cell proliferation and in vivo tumor growth of naLAT1/3T3 cells in nude mice, demonstrating LAT1 to be a promising anti-cancer target.