Hunter J E, Butterworth J A, Zhao B, Sellier H, Campbell K J, Thomas H D, Bacon C M, Cockell S J, Gewurz B E, Perkins N D
Institute for Cell and Molecular Biosciences (ICaMB), Newcastle University Medical School, Newcastle Upon Tyne, UK.
Brigham and Women's Hospital, Boston, MA, USA.
Oncogene. 2016 Jun 30;35(26):3476-84. doi: 10.1038/onc.2015.399. Epub 2015 Nov 2.
The REL gene, encoding the NF-κB subunit c-Rel, is frequently amplified in B-cell lymphoma and functions as a tumour-promoting transcription factor. Here we report the surprising result that c-rel-/- mice display significantly earlier lymphomagenesis in the c-Myc driven, Eμ-Myc model of B-cell lymphoma. c-Rel loss also led to earlier onset of disease in a separate TCL1-Tg-driven lymphoma model. Tumour reimplantation experiments indicated that this is an effect intrinsic to the Eμ-Myc lymphoma cells but, counterintuitively, c-rel-/- Eμ-Myc lymphoma cells were more sensitive to apoptotic stimuli. To learn more about why loss of c-Rel led to earlier onset of disease, microarray gene expression analysis was performed on B cells from 4-week-old, wild-type and c-rel-/- Eμ-Myc mice. Extensive changes in gene expression were not seen at this age, but among those transcripts significantly downregulated by the loss of c-Rel was the B-cell tumour suppressor BTB and CNC homology 2 (Bach2). Quantitative PCR and western blot analysis confirmed loss of Bach2 in c-Rel mutant Eμ-Myc tumours at both 4 weeks and the terminal stages of disease. Moreover, Bach2 expression was also downregulated in c-rel-/- TCL1-Tg mice and RelA Thr505Ala mutant Eμ-Myc mice. Analysis of wild-type Eμ-Myc mice demonstrated that the population expressing low levels of Bach2 exhibited the earlier onset of lymphoma seen in c-rel-/- mice. Confirming the relevance of these findings to human disease, analysis of chromatin immunoprecipitation sequencing data revealed that Bach2 is a c-Rel and NF-κB target gene in transformed human B cells, whereas treatment of Burkitt's lymphoma cells with inhibitors of the NF-κB/IκB kinase pathway or deletion of c-Rel or RelA resulted in loss of Bach2 expression. These data reveal a surprising tumour suppressor role for c-Rel in lymphoma development explained by regulation of Bach2 expression, underlining the context-dependent complexity of NF-κB signalling in cancer.
编码核因子κB亚基c-Rel的REL基因在B细胞淋巴瘤中经常扩增，并作为一种促进肿瘤的转录因子发挥作用。在此，我们报告了一个惊人的结果：在c-Myc驱动的Eμ-Myc B细胞淋巴瘤模型中，c-rel-/-小鼠的淋巴瘤发生明显更早。在另一个TCL1-Tg驱动的淋巴瘤模型中，c-Rel缺失也导致疾病更早发作。肿瘤再植入实验表明，这是Eμ-Myc淋巴瘤细胞固有的效应，但与直觉相反的是，c-rel-/- Eμ-Myc淋巴瘤细胞对凋亡刺激更敏感。为了进一步了解c-Rel缺失导致疾病更早发作的原因，对4周龄野生型和c-rel-/- Eμ-Myc小鼠的B细胞进行了微阵列基因表达分析。在这个年龄段未观察到基因表达的广泛变化，但在那些因c-Rel缺失而显著下调的转录本中，有B细胞肿瘤抑制因子BTB和CNC同源物2（Bach2）。定量PCR和蛋白质印迹分析证实，在4周龄和疾病末期的c-Rel突变Eμ-Myc肿瘤中，Bach2均缺失。此外，在c-rel-/- TCL1-Tg小鼠和RelA Thr505Ala突变Eμ-Myc小鼠中，Bach2表达也下调。对野生型Eμ-Myc小鼠的分析表明，表达低水平Bach2的群体表现出c-rel-/-小鼠中所见的更早淋巴瘤发作。对染色质免疫沉淀测序数据的分析证实了这些发现与人类疾病的相关性，结果显示Bach2是转化的人类B细胞中的c-Rel和核因子κB靶基因，而用核因子κB/IκB激酶途径抑制剂处理伯基特淋巴瘤细胞或缺失c-Rel或RelA会导致Bach2表达丧失。这些数据揭示了c-Rel在淋巴瘤发展中出人意料的肿瘤抑制作用，这一作用可通过对Bach2表达的调控来解释，突显了核因子κB信号在癌症中依赖于背景的复杂性。
