| Affiliations | Department of Pathology, Sapporo Medical University School of Medicine, South-1 West-17, Chuo-Ku, Sapporo, Hokkaido, 060-8556, Japan; Department of Renal and Genitourinary Surgery, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, 060-8648, Japan; Department of Pathology, Sapporo Medical University School of Medicine, South-1 West-17, Chuo-Ku, Sapporo, Hokkaido, 060-8556, Japan. hirohash@sapmed.ac.jp; Department of Molecular Pathophysiology, Institute of Advanced Medicine, Wakayama Medical University, Wakayama, Wakayama, 641-8509, Japan; Department of Pathology, Sapporo Medical University School of Medicine, South-1 West-17, Chuo-Ku, Sapporo, Hokkaido, 060-8556, Japan. torigoe@sapmed.ac.jp. | |
| Abstract | Recent studies have revealed that treatment-resistant cancer stem-like cells (CSCs)/cancer-initiating cells (CICs) can be targeted by cytotoxic T lymphocytes (CTLs). CTLs recognize antigenic peptides derived from tumor-associated antigens; thus, the identification of tumor-associated antigens expressed by CSCs/CICs is essential. Human leucocyte antigen (HLA) ligandome analysis using mass spectrometry enables the analysis of naturally expressed antigenic peptides; however, HLA ligandome analysis requires a large number of cells and is challenging for CSCs/CICs. In this study, we established a novel bladder CSC/CIC model from a bladder cancer cell line (UM-UC-3 cells) using an ALDEFLUOR assay. CSCs/CICs were isolated as aldehyde dehydrogenase (ALDH)-high cells and several ALDH<sup>high</sup> clone cells were established. ALDH<sup>high</sup> clone cells were enriched with CSCs/CICs by sphere formation and tumorigenicity in immunodeficient mice. HLA ligandome analysis and cap analysis of gene expression using ALDH<sup>high</sup> clone cells revealed a distinctive antigenic peptide repertoire in bladder CSCs/CICs, and we found that a glutamate receptor, ionotropic, kainite 2 (GRIK2)-derived antigenic peptide (LMYDAVHVV) was specifically expressed by CSCs/CICs. A GRIK2 peptide-specific CTL clone recognized GRIK2-overexpressing UM-UC-3 cells and ALDH<sup>high</sup> clone cells, indicating that GRIK2 peptide can be a novel target for bladder CSC/CIC-targeting immunotherapy. | |