Histone acetylation and DNA demethylation of T-cells result in an anaplastic large cell lymphoma-like phenotype.. Homo sapiens

A characteristic feature of anaplastic large cell lymphoma (ALCL) is the significant reduction of the T-cell expression program despite its T-cell origin, a finding very similar to the loss of B-cell identity of classical Hodgkin lymphoma (cHL). Previously we demonstrated that epigenetic mechanisms are active in cHL to induce this peculiar phenotype. The results show that combined DNA demethylation and histone acetylation of T-cell lines induce an almost complete extinction of the T-cell phenotype, including the down-regulation of essential T-cell receptor signalling pathway genes such as CD3, LCK and ZAP70, as well as an up-regulation of ALCL-characteristic genes. In contrast, combined DNA demethylation and histone acetylation of ALCL cells is not able to reconstitute their T-cell phenotype. This clearly demonstrates that similar epigenetic mechanisms are active in ALCL and cHL which are responsible for the extinction of their cell type characteristic phenotype. Overall design: We subjected T-cell lymphoma/leukemia cell lines and ALCL cell lines (n=4, each) to epigenetic modifiers to evoke DNA demethylation and the histone acetylation. Global gene expression profiling (Affymetrix) was performed from treated and untreated cell lines which were evaluated by real-time RT-PCR and Western Blot analysis.

间变性大细胞淋巴瘤（anaplastic large cell lymphoma, ALCL）的特征性表现为：尽管其起源于T细胞，但T细胞表达程序显著缺失，这一现象与经典霍奇金淋巴瘤（classical Hodgkin lymphoma, cHL）的B细胞身份丧失极为相似。既往研究证实，表观遗传机制（epigenetic mechanisms）在cHL中发挥作用，诱导产生这种特殊的表型。本研究结果显示，对T细胞系联合实施DNA去甲基化（DNA demethylation）与组蛋白乙酰化（histone acetylation）处理，可几乎完全抑制T细胞表型，包括下调CD3、LCK、ZAP70等核心T细胞受体信号通路基因，同时上调ALCL特征性基因。与之相反，对ALCL细胞联合进行DNA去甲基化与组蛋白乙酰化处理，无法恢复其T细胞表型。该结果明确表明，ALCL与cHL中存在相似的表观遗传机制，二者共同导致细胞类型特异性表型的丧失。整体实验设计：我们分别对T细胞淋巴瘤/白血病细胞系与ALCL细胞系（每组各4株，n=4）施加表观遗传修饰剂，以诱导DNA去甲基化与组蛋白乙酰化。分别从处理组与未处理组细胞系中获取样本，开展全基因组基因表达谱分析（采用Affymetrix芯片），并通过实时荧光定量逆转录聚合酶链反应（real-time RT-PCR）与蛋白质免疫印迹（Western Blot）分析对实验结果进行验证。