Immunology Laboratory Willem-Alexander Children's Hospital, Leiden University Medical Center, Leiden, Netherlands.
Department of Immunology, Erasmus University Medical Center, Rotterdam, Netherlands.
Front Immunol. 2020 Jan 10;10:3045. doi: 10.3389/fimmu.2019.03045. eCollection 2019.
Langerhans Cell Histiocytosis (LCH) is a neoplastic disorder of hematopoietic origin characterized by inflammatory lesions containing clonal histiocytes (LCH-cells) intermixed with various immune cells, including T cells. In 50-60% of LCH-patients, the somatic driver mutation, which is common in many cancers, is detected in these LCH-cells in an otherwise quiet genomic landscape. Non-synonymous mutations like can be a source of neoantigens capable of eliciting effective antitumor CD8 T cell responses. This requires neopeptides to be stably presented by Human Leukocyte Antigen (HLA) class I molecules and sufficient numbers of CD8 T cells at tumor sites. Here, we demonstrate substantial heterogeneity in CD8 T cell density in = 101 LCH-lesions, with mutated lesions displaying significantly lower CD8 T cell:CD1a LCH-cell ratios ( = 0.01) than wildtype lesions. Because LCH-lesional CD8 T cell density had no significant impact on event-free survival, we investigated whether the intracellularly expressed protein is degraded into neopeptides that are naturally processed and presented by cell surface HLA class I molecules. Epitope prediction tools revealed a single HLA class I binding derived neopeptide (KIGDFGLATK), which indeed displayed strong to intermediate binding capacity to HLA-A03:01 and HLA-A11:01 in an peptide-HLA binding assay. Mass spectrometry-based targeted peptidomics was used to investigate the presence of this neopeptide in HLA class I presented peptides isolated from several expressing cell lines with various HLA genotypes. While the HLA-A02:01 binding wildtype peptide KIGDFGLATV was traced in peptides isolated from all five cell lines expressing this HLA subtype, KIGDFGLATK was not detected in the HLA class I peptidomes of two distinct transduced cell lines with confirmed expression of HLA-A03:01 or HLA-A11:01. These data indicate that the predicted HLA class I binding and proteasome-generated neopeptides derived from the protein are not presented by HLA class I molecules. Given that the mutation is highly prevalent in chemotherapy refractory LCH-patients who may qualify for immunotherapy, this study therefore questions the efficacy of immune checkpoint inhibitor therapy in LCH.
朗格汉斯细胞组织细胞增生症（LCH）是一种造血来源的肿瘤性疾病，其特征为炎症性病变中存在克隆性组织细胞（LCH 细胞），与各种免疫细胞混合存在，包括 T 细胞。在 50-60%的 LCH 患者中，这些 LCH 细胞中存在体细胞驱动突变，这种突变在许多癌症中都很常见，而在其他情况下基因组则处于静止状态。非同义突变，如，可以作为新抗原的来源，能够引发有效的抗肿瘤 CD8 T 细胞反应。这需要新肽能够由人类白细胞抗原（HLA）I 类分子稳定呈递，并且在肿瘤部位有足够数量的 CD8 T 细胞。在这里，我们在 101 个 LCH 病变中证明了 CD8 T 细胞密度存在显著异质性，突变病变的 CD8 T 细胞：CD1a LCH 细胞比值显著低于野生型病变（=0.01）。由于 LCH 病变中的 CD8 T 细胞密度对无事件生存没有显著影响，我们研究了细胞内表达的蛋白是否会降解成新肽，这些新肽可以被细胞表面 HLA I 类分子自然加工和呈递。表位预测工具揭示了一个单一的 HLA I 类结合的新肽（KIGDFGLATK），该新肽在 HLA 肽-HLA 结合测定中确实显示出对 HLA-A03:01 和 HLA-A11:01 的强至中等结合能力。基于质谱的靶向肽组学用于研究该新肽在几种具有不同 HLA 基因型的表达 蛋白的细胞系中分离的 HLA I 呈递肽中的存在。虽然在表达此 HLA 亚型的五个细胞系中分离的肽中均追踪到 HLA-A02:01 结合的野生型肽 KIGDFGLATV，但在两个经证实表达 HLA-A03:01 或 HLA-A11:01 的不同 转导细胞系的 HLA 类 I 肽组中未检测到 KIGDFGLATK。这些数据表明，从 蛋白预测的 HLA I 类结合和蛋白酶体产生的新肽未被 HLA I 类分子呈递。鉴于该 突变在化疗耐药的 LCH 患者中非常普遍，这些患者可能有资格接受免疫治疗，因此该研究质疑免疫检查点抑制剂治疗在 LCH 中的疗效。
