Table_3_Pro-inflammatory Cytokines Alter the Immunopeptidome Landscape by Modulation of HLA-B Expression.XLSX

Antigen presentation on HLA molecules is a major mechanism by which the immune system monitors self and non-self-recognition. Importantly, HLA-I presentation has gained much attention through its role in eliciting anti-tumor immunity. Several determinants controlling the peptides presented on HLA have been uncovered, mainly through the study of model substrates and large-scale immunopeptidome analyses. These determinants include the relative abundances of proteins in the cell, the stability or turnover rate of these proteins and the binding affinities of a given peptide to the HLA haplotypes found in a cell. However, the regulatory principles involved in selection and regulation of specific antigens in response to tumor pro-inflammatory signals remain largely unknown. Here, we chose to examine the effect that TNFα and IFNγ stimulation may exert on the immunopeptidome landscape of lung cancer cells. We show that the expression of many of the proteins involved in the class I antigen presentation pathway are changed by pro-inflammatory cytokines. Further, we could show that increased expression of the HLA-B allomorph drives a significant change in HLA-bound antigens, independently of the significant changes observed in the cellular proteome. Finally, we observed increased HLA-B levels in correlation with tumor infiltration across the TCGA lung cancer cohorts. Taken together, our results suggest that the immunopeptidome landscape should be examined in the context of anti-tumor immunity whereby signals in the microenvironment may be critical in shaping and modulating this important aspect of host-tumor interactions.

人类白细胞抗原（HLA）分子上的抗原呈递是免疫系统监控自我与非自我识别的核心机制之一。尤为重要的是，HLA-I类分子呈递因其在诱导抗肿瘤免疫中的关键作用而受到广泛关注。目前已有多项调控HLA结合肽段的决定因素被揭示，相关研究主要基于模式底物分析与大规模免疫肽组（immunopeptidome）分析展开。这些决定因素包括细胞内蛋白质的相对丰度、蛋白质的稳定性或周转速率，以及特定肽段与细胞内存在的HLA单倍型之间的结合亲和力。然而，在响应肿瘤促炎信号的过程中，调控特定抗原的选择与表达的核心机制仍未被充分阐明。本研究选取肺癌细胞为研究对象，探究肿瘤坏死因子α（TNFα）与干扰素γ（IFNγ）的刺激对其免疫肽组图谱的调控效应。研究发现，促炎细胞因子可显著改变I类抗原呈递通路中多数蛋白质的表达水平。进一步研究表明，HLA-B等位基因变异体的表达上调可显著改变HLA结合抗原的谱型，且该效应独立于细胞蛋白质组所发生的显著变化。最后，基于癌症基因组图谱（The Cancer Genome Atlas, TCGA）肺癌队列的数据，我们观察到HLA-B的表达水平与肿瘤浸润程度呈正相关。综上，本研究结果表明，在抗肿瘤免疫的研究框架下应充分考量免疫肽组图谱的变化——肿瘤微环境中的信号分子在塑造与调控宿主-肿瘤相互作用这一关键环节中发挥着至关重要的作用。