Tumor suppressor functions of DAXX through histone H3.3/H3K9me3 pathway in pancreatic NETs.
Tumor suppressor functions of DAXX through histone H3.3/H3K9me3 pathway in pancreatic NETs.
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DOI：
10.1530/erc-17-0328
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发表时间：
2018-06
影响因子：
3.9
通讯作者：
H. Ueda;Y. Akiyama;S. Shimada;K. Mogushi;Misaki Serizawa;S. Matsumura;Y. Mitsunori;Arihiro Aihara-Arihiro-Aihar
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文献类型：
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作者：
H. Ueda;Y. Akiyama;S. Shimada;K. Mogushi;Misaki Serizawa;S. Matsumura;Y. Mitsunori;Arihiro Aihara-Arihiro-Aihar
胰腺神经内分泌肿瘤（PanNET）具有相当大的恶性潜力。在PanNET中发现了频繁的体细胞突变和DAXX蛋白表达的缺失。DAXX被认为是一种转录抑制因子;然而，在PanNET中DAXX缺失的分子功能仍然不清楚。我们通过免疫组化评估了44个PanNET中DAXX的表达。对DAXX-敲低（KD）和-敲低（KO）PanNET细胞进行体外和体内分析。通过微阵列和染色质免疫沉淀（ChIP）测定法筛选DAXX、组蛋白H3.3和H3 K9 me 3复合物的靶基因。在临床病理特征中，DAXX低表达与无功能性肿瘤、Ki-67指数和WHO分级显著相关。DAXX-KD/KO的基因芯片和ChIP分析鉴定了12个基因为DAXX转录抑制子的直接靶基因。其中包括STC 2在内的5个基因的表达受到DAXX/H3.3/H3 K9 me 3途径的抑制。DAXX-KD/KO细胞增强球体形成活性，但其作用被STC 2的敲低抑制。在异种移植模型中，具有高表达STC 2的DAXX-KO细胞的致瘤性和肿瘤血管密度显著增加。DAXX低表达和STC 2高表达的PanNET患者复发率高于其他患者（P = 0.018）。我们的数据表明，DAXX作为肿瘤抑制因子发挥作用，DAXX/H3.3复合物通过促进PanNET中的H3 K9 me 3来抑制靶基因。DAXX缺失和其靶基因STC 2过表达的组合可能是有效的生物标志物和治疗候选物。
Pancreatic neuroendocrine tumors (PanNETs) have considerable malignant potential. Frequent somatic mutations and loss of DAXX protein expression have been found in PanNETs. DAXX is known as a transcriptional repressor; however, molecular functions underlying DAXX loss remain unclear in PanNETs. We evaluated DAXX expression by immunohistochemistry in 44 PanNETs. DAXX-knockdown (KD) and -knockout (KO) PanNET cells were analyzed for in vitro and vivo The target genes were screened by microarray and chromatin immunoprecipitation (ChIP) assays for DAXX, histone H3.3 and H3K9me3 complex. In clinicopathological features, low DAXX expression was significantly correlated with nonfunctional tumors, higher Ki-67 index and WHO grade. Microarray and ChIP assays of DAXX-KD/KO identified 12 genes as the direct targets of DAXX transcriptional repressor. Among them, expression of five genes including STC2 was suppressed by DAXX/H3.3/H3K9me3 pathway. DAXX-KD/KO cells enhanced sphere forming activity, but its effect was suppressed by knockdown of STC2 In xenograft models, tumorigenicity and tumor vessel density were significantly increased in DAXX-KO cells with high expression of STC2. Clinically, higher recurrence rate was recognized in PanNETs with low expression of DAXX and high expression of STC2 than others (P = 0.018). Our data suggest that DAXX plays as a tumor suppressor and DAXX/H3.3 complex suppresses target genes by promoting H3K9me3 in PanNETs. Combination of DAXX loss and its target gene STC2 overexpression might be effective biomarkers and therapeutic candidates.