Kochin Vitaly, Kanaseki Takayuki, Tokita Serina, Miyamoto Sho, Shionoya Yosuke, Kikuchi Yasuhiro, Morooka Daichi, Hirohashi Yoshihiko, Tsukahara Tomohide, Watanabe Kazue, Toji Shingo, Kokai Yasuo, Sato Noriyuki, Torigoe Toshihiko
Department of Pathology, Sapporo Medical University, Sapporo, Japan.
Department of Immunology, Nagoya University Graduate School of Medicine, Nagoya, Japan.
Oncoimmunology. 2017 Feb 16;6(4):e1293214. doi: 10.1080/2162402X.2017.1293214. eCollection 2017.
This study focused on HLA-A24 and comprehensively analyzed the ligandome of colon and lung cancer cells without the use of MHC-binding prediction algorithms. Affinity purification using the antibody specific to HLA-A24 followed by LC-MS/MS sequencing was used to detect peptides, which harbored the known characteristics of HLA-A24 peptides in terms of length and anchor motifs. Ligandome analysis demonstrated the natural presentation of two different types of novel tumor-associated antigens. The ligandome contained a peptide derived from , a gene found to be expressed in a variety of cancers but not in normal tissues (except for the testis). The SUV39H2 peptide is immunogenic and elicits cytotoxic CD8 T-cell (CTL) responses against cancer cells and is thus a novel cancer-testis antigen. Moreover, we found that microsatellite instability (MSI)-colon cancer cells displayed a neoepitope with an amino-acid substitution, while microsatellite stable (MSS)-colon and lung cancer cells displayed its counterpart peptide without the substitution. Structure modeling of peptide-HLA-A24 complexes predicted that the mutated residue at P8 was accessible to T-cell receptors. The neoepitope readily elicited CTL responses, which discriminated it from its wild-type counterpart, and the CTLs exhibited considerably high cytotoxicity against MSS-colon cancer cells carrying the responsible gene mutation. The specific and strong CTL lysis observed in this study fosters our understanding of immune surveillance against neoantigens.
本研究聚焦于HLA - A24，在不使用MHC结合预测算法的情况下，全面分析了结肠癌细胞和肺癌细胞的配体组。采用针对HLA - A24的特异性抗体进行亲和纯化，随后进行液相色谱 - 串联质谱测序以检测肽段，这些肽段在长度和锚定基序方面具有HLA - A24肽段的已知特征。配体组分析揭示了两种不同类型新型肿瘤相关抗原的天然呈递情况。该配体组包含一种源自SUV39H2的肽段，SUV39H2是一个在多种癌症中表达但在正常组织（睾丸除外）中不表达的基因。SUV39H2肽具有免疫原性，可引发针对癌细胞的细胞毒性CD8 T细胞（CTL）反应，因此是一种新型癌 - 睾丸抗原。此外，我们发现微卫星不稳定（MSI）的结肠癌细胞显示出一个带有氨基酸替换的新表位，而微卫星稳定（MSS）的结肠癌细胞和肺癌细胞则显示出其未发生替换的对应肽段。肽 - HLA - A24复合物的结构建模预测，P8位点的突变残基可被T细胞受体识别。该新表位很容易引发CTL反应，使其与野生型对应物区分开来，并且CTL对携带相关基因突变的MSS结肠癌细胞表现出相当高的细胞毒性。本研究中观察到的特异性且强烈的CTL裂解作用有助于我们理解针对新抗原的免疫监视机制。
