Dept. of Human and Animal Cell Lines, DSMZ - German Collection of Microorganisms and Cell Cultures, Inhoffenstr. 7B, 38124 Braunschweig, Germany.
Mol Cancer. 2010 Jun 17;9:151. doi: 10.1186/1476-4598-9-151.
NK- and T-cells are closely related lymphocytes, originating from the same early progenitor cells during hematopoiesis. In these differentiation processes deregulation of developmental genes may contribute to leukemogenesis. Here, we compared expression profiles of NK- and T-cell lines for identification of aberrantly expressed genes in T-cell acute lymphoblastic leukemia (T-ALL) which physiologically regulate the differentiation program of the NK-cell lineage.
This analysis showed high expression levels of HOXA9, HOXA10 and ID2 in NK-cell lines in addition to T-cell line LOUCY, suggesting leukemic deregulation therein. Overexpression experiments, chromatin immuno-precipitation and promoter analysis demonstrated that HOXA9 and HOXA10 directly activated expression of ID2. Concomitantly elevated expression levels of HOXA9 and HOXA10 together with ID2 in cell lines containing MLL translocations confirmed this form of regulation in both ALL and acute myeloid leukemia. Overexpression of HOXA9, HOXA10 or ID2 resulted in repressed expression of apoptosis factor BIM. Furthermore, profiling data of genes coding for chromatin regulators of homeobox genes, including components of polycomb repressor complex 2 (PRC2), indicated lacking expression of EZH2 in LOUCY and exclusive expression of HOP in NK-cell lines. Subsequent treatment of T-cell lines JURKAT and LOUCY with DZNep, an inhibitor of EZH2/PRC2, resulted in elevated and unchanged HOXA9/10 expression levels, respectively. Moreover, siRNA-mediated knockdown of EZH2 in JURKAT enhanced HOXA10 expression, confirming HOXA10-repression by EZH2. Additionally, profiling data and overexpression analysis indicated that reduced expression of E2F cofactor TFDP1 contributed to the lack of EZH2 in LOUCY. Forced expression of HOP in JURKAT cells resulted in reduced HOXA10 and ID2 expression levels, suggesting enhancement of PRC2 repression.
Our results show that major differentiation factors of the NK-cell lineage, including HOXA9, HOXA10 and ID2, were (de)regulated via PRC2 which therefore contributes to T-cell leukemogenesis.
NK 细胞和 T 细胞是密切相关的淋巴细胞，起源于造血过程中同一早期祖细胞。在这些分化过程中，发育基因的失调可能导致白血病的发生。在这里，我们比较了 NK 细胞系和 T 细胞系的表达谱，以鉴定生理上调节 NK 细胞系分化程序的 T 细胞急性淋巴细胞白血病（T-ALL）中异常表达的基因。
该分析表明，除了 T 细胞系 LOUCY 外，NK 细胞系中高表达 HOXA9、HOXA10 和 ID2，提示其白血病失调。过表达实验、染色质免疫沉淀和启动子分析表明，HOXA9 和 HOXA10 直接激活 ID2 的表达。同时，在含有 MLL 易位的细胞系中，HOXA9 和 HOXA10 以及 ID2 的表达水平升高，证实了这种在 ALL 和急性髓细胞白血病中的调节形式。HOXA9、HOXA10 或 ID2 的过表达导致凋亡因子 BIM 的表达受到抑制。此外，同源盒基因染色质调节因子的基因表达谱数据，包括多梳抑制复合物 2（PRC2）的组成部分，表明 LOUCY 中缺乏 EZH2 的表达，而仅在 NK 细胞系中表达 HOP。随后用 EZH2/PRC2 的抑制剂 DZNep 处理 T 细胞系 JURKAT 和 LOUCY，分别导致 HOXA9/10 表达水平的升高和不变。此外，JURKAT 中 EZH2 的 siRNA 介导敲低增强了 HOXA10 的表达，证实了 EZH2 对 HOXA10 的抑制。此外，表达谱数据和过表达分析表明，E2F 辅助因子 TFDP1 的表达降低导致 LOUCY 中缺乏 EZH2。在 JURKAT 细胞中强制表达 HOP 导致 HOXA10 和 ID2 表达水平降低，表明 PRC2 抑制增强。
我们的结果表明，NK 细胞系的主要分化因子，包括 HOXA9、HOXA10 和 ID2，通过 PRC2 （de）调节，从而有助于 T 细胞白血病的发生。
