Institute of Pathology, University Medical Centre Mannheim, University of Heidelberg Mannheim, Germany.
Department of Neurology, University of Regensburg Regensburg, Germany.
Ann Clin Transl Neurol. 2015 Sep;2(9):894-905. doi: 10.1002/acn3.210. Epub 2015 Jul 22.
The capacity of thymomas to generate mature CD4+ effector T cells from immature precursors inside the tumor and export them to the blood is associated with thymoma-associated myasthenia gravis (TAMG). Why TAMG(+) thymomas generate and export more mature CD4+ T cells than MG(-) thymomas is unknown.
Unfixed thymoma tissue, thymocytes derived thereof, peripheral blood mononuclear cells (PBMCs), T-cell subsets and B cells were analysed using qRT-PCR and western blotting. Survival of PBMCs was measured by MTT assay. FAS-mediated apoptosis in PBMCs was quantified by flow cytometry. NF-κB in PBMCs was inhibited by the NF-κB-Inhibitor, EF24 prior to FAS-Ligand (FASLG) treatment for apoptosis induction.
Expression levels of the apoptosis inhibitor cellular FLICE-like inhibitory protein (c-FLIP) in blood T cells and intratumorous thymocytes were higher in TAMG(+) than in MG(-) thymomas and non-neoplastic thymic remnants. Thymocytes and PBMCs of TAMG patients showed nuclear NF-κB accumulation and apoptosis resistance to FASLG stimulation that was sensitive to NF-κB blockade. Thymoma removal reduced cFLIP expression in PBMCs.
We conclude that thymomas induce cFLIP overexpression in thymocytes and their progeny, blood T cells. We suggest that the stronger cFLIP overexpression in TAMG(+) compared to MG(-) thymomas allows for the more efficient generation of mature CD4+ T cells in TAMG(+) thymomas. cFLIP overexpression in thymocytes and exported CD4+ T cells of patients with TAMG might contribute to the pathogenesis of TAMG by impairing central and peripheral T-cell tolerance.
胸腺瘤内不成熟前体在肿瘤内产生成熟 CD4+效应 T 细胞并输出到血液中的能力与胸腺瘤相关重症肌无力（TAMG）有关。为什么 TAMG(+)胸腺瘤比 MG(-)胸腺瘤产生和输出更多成熟的 CD4+T 细胞尚不清楚。
使用 qRT-PCR 和 Western blot 分析固定的胸腺瘤组织、从中衍生的胸腺细胞、外周血单核细胞 (PBMC)、T 细胞亚群和 B 细胞。通过 MTT 测定法测量 PBMC 的存活率。通过流式细胞术定量测定 PBMC 中 FAS 介导的细胞凋亡。在 FASL（FAS 配体）诱导凋亡之前，用 NF-κB 抑制剂 NF-κB-Inhibitor，EF24 抑制 PBMC 中的 NF-κB。
TAMG(+)胸腺瘤和非肿瘤性胸腺残体中，T 细胞和肿瘤内胸腺细胞中凋亡抑制剂细胞 FLICE 样抑制蛋白 (c-FLIP) 的表达水平高于 MG(-)胸腺瘤。TAMG 患者的胸腺细胞和 PBMC 显示核 NF-κB 积累，并且对 FASLG 刺激的细胞凋亡具有抗性，这种抗性对 NF-κB 阻断敏感。胸腺瘤切除减少了 PBMC 中的 cFLIP 表达。
我们得出结论，胸腺瘤诱导胸腺细胞及其祖细胞、血液 T 细胞中 cFLIP 的过度表达。我们认为，与 MG(-)胸腺瘤相比，TAMG(+)胸腺瘤中更强的 cFLIP 过表达允许在 TAMG(+)胸腺瘤中更有效地产生成熟的 CD4+T 细胞。TAMG 患者的胸腺细胞和输出的 CD4+T 细胞中 cFLIP 的过度表达可能通过损害中枢和外周 T 细胞耐受而有助于 TAMG 的发病机制。
