HLA-DRB1*0410-Restricted Recognition of XAGE-1b37-48 Peptide by CD4 T Cells

Computational prediction of vaccine potential epitopes and 3-dimensional structure of XAGE-1b for non-small cell lung cancer immunotherapy

BACKGROUND

XAGE-1b is shown to be overexpressed in lung adenocarcinoma and to be a strong immunogenic antigen among non-small cell lung cancer (NSCLC) patients. However, 3D structure of XAGE-1b is not available and its confirmation has not been solved yet.

METHODS

Multiple sequence alignment was run to select the most reliable templates. Homology modeling technique was performed using computer-based tool to generate 3-dimensional structure models, eight models were generated and assessed on basis of local and global quality. Immune Epitope Database (IEDB) tools were then used to determine potential B-Cell epitopes while NetMHCpan algorithms were used to enhance the determination for potential epitopes of both Cytotoxic T-lymphocytes and T-helper cells.

RESULTS

Computational prediction was performed for B-Cell epitopes, prediction results generated; 3 linear epitopes where XAGE-1b (13-21) possessed the best score of 0.67, 5 discontinuous epitopes where XAGE-1b (40-52) possessed the best score of 0.67 based on the predicted model of the finest quality. For a potential vaccine design, computational prediction yielded potential Human Leukocyte Antigen (HLA) class I epitopes including HLA-B*08:01-restricted XAGE-1b (3-11) epitope which was the best with 0.2 percentile rank. Regarding HLA Class II epitopes, HLA-DRB1*12:01-restricted XAGE-1b (25-33) was the most antigenic epitope with 5.91 IC50 value. IC50 values were compared with experimental values and population coverage percentages of epitopes were computed.

CONCLUSIONS

This study predicted a model of XAGE-1b tertiary structure which could explain its antigenic function and facilitate usage of predicted peptides for experimental validation towards designing immunotherapies against NSCLC.

Immune Responses to the Cancer Testis Antigen XAGE-1b in Non Small Cell Lung Cancer Caucasian Patients

Immunotherapy approaches using checkpoint blockade, alone, or in combination with tumor antigen vaccination, or adoptive cell transfer, are emerging as promising approaches for the treatment of non-small cell lung cancer (NSCLC). In preparation for upcoming combined immunotherapy approaches in NSCLC, here, we have assessed spontaneous immune responses to XAGE-1b, a tumor specific antigen of the Cancer Testis Antigen group that has been previously reported to be spontaneously immunogenic in the Japanese population, in a cohort of Caucasian patients with NSCLC. We found spontaneous serological responses to XAGE-1b in 9% of the patients. Importantly, these responses were limited to, and represented 13% of, patients with adenocarcinoma tumors, the most frequent histological subtype, for which immunotherapy approaches are under development. Using a set of overlapping peptides spanning the entire XAGE-1b protein, and in support of the serological data, we detected significant XAGE-1b specific CD4⁺ T cell responses in all XAGE-1b seropositive patients and identified several CD4⁺ T cell epitopes. Altogether, our results support the relevance of the XAGE-1b antigen in Caucasians NSCLC patients with adenocarcinoma, and the implementation of future immunotherapies exploiting the high immunogenicity of the antigen in this patient population.

Hepatocellular carcinoma patients highly and specifically expressing XAGE-1 exhibit prolonged survival

XAGE-1 is classified into the group of a new family of cancer-testis antigens (CTA) and has the four transcript variants of XAGE-1a, XAGE-1b, XAGE-1c and XAGE-1d. Immunohistochemistry was used to investigate the expression of XAGE-1 transcript variants in Chinese patients with hepatocellular carcinoma (HCC). Reverse transcription-polymerase chain reaction (RT-PCR) and real-time RT-PCR were used to analyze XAGE-1 gene expression, and XAGE-1 protein expression was examined by immunohistochemistry. Furthermore, the clinical correlation of XAGE-1 expression was analyzed. The expression of the XAGE-1 mRNA was investigated in the tissues of 96 HCC patients and all XAGE-1 isoforms were detected in these tissues. Three types of XAGE-1 transcript variants (XAGE-1b, XAGE-1c and XAGE-1d) showed high specific and frequent expression in HCC tissues, with the positive expression rate of XAGE-1b, XAGE-1c and XAGE-1d being 41.7% (40/96), 15.6% (15/96) and 26.0% (25/96), respectively. XAGE-1b was the dominant type, but none of the three were detected in adjacent non-HCC tissues. Only 2 cases of XAGE-1a mRNA expression were observed. Moreover, XAGE-1 protein was detected in 39 of 96 HCC patients, but none in the adjacent non-cancerous tissue and normal liver tissue. No relationship was found between the expression of XAGE-1 and clinical parameters, such as age, gender, tumor size, TNM staging, serum AFP level and infection with hepatitis virus. Patients with XAGE-1b-positive transcript variant exhibited shorter 2-year survival times. The high frequency and specificity of XAGE-1, particularly XAGE-1b, in HCC indicates that their products may predict the prognosis of HCC patients and be novel targets for antigen-specific immunotherapy to HCC.

[Association of XAGE-1 gene expression with clinical characteristics of lung cancer]

背景与目的

研究证实XAGE-1作为一种癌胚抗原在多种肿瘤中高表达。本研究旨在探讨XAGE-1基因在肺癌组织中的表达水平及其与临床特点的关系。

方法

肺癌患者85例，提取肺癌组织和癌旁组织总RNA，巢式PCR反应扩增XAGE-1四种剪接体基因，分析基因表达情况及其与临床特点的关系。

结果

32.94%（28/85）肺癌患者癌组织阳性表达XAGE-1基因，在各种类型肺癌中，59.46%（22/37）的腺癌与21.74%（5/23）鳞癌患者癌组织阳性表达XAGE-1基因；XAGE-1b基因的表达与肺癌病理类型有相关性（P < 0.05），腺癌阳性表达率明显高于鳞癌，而与肺癌的性别、年龄及临床分期无相关性（P > 0.05）。

结论

XAGE-1基因在肺癌尤其腺癌组织中高表达，该基因可以作为免疫治疗的靶基因。

mRNA expression of the XAGE-1 gene in human acute leukemia

XAGE-1 is a cancer-testis antigen, which was demonstrated to be expressed at a significant frequency and to be immunogenic in some solid tumors. We analyzed the expression of 4 XAGE-1 transcript variant gene in human acute leukemias by reverse-transcription polymerase chain reaction. Among the 114 acute leukemias, 14/63 (22.22%) of the acute myeloid leukemia samples were positive for XAGE-1b genes. XAGE-1b mRNA expression was detected in 10/51 (19.61%) of the acute lymphocyte leukemia samples. However, we did not find any important correlation between XAGE-1b mRNA expression and clinical characteristics, such as sex, leukemia type, response to therapy and the percentage of blast in the first diagnosed bone marrow. We concluded that the XAGE-1b gene was expressed at the mRNA level in a proportion of human acute leukemia.