RARB Translocations in Acute Promyelocytic Leukemia without Rara translocation-猫眼课题宝

DOI：

10.1182/blood.v130.suppl_1.104.104

发表时间：

2017-12

期刊：

Blood

影响因子：

20.3

通讯作者：

中科院分区：

医学1区

文献类型：

作者：

Motohiro Kato;T. Osumi;Shinichi Tsujimoto;Moe Tamura;Meri Uchiyama;K. Nakabayashi;K. Okamura;D. Tomizawa;A. Watanabe;Hiroyuki Takahashi;T. Hori;Shohei Yamamoto;K. Hamamoto;M. Migita;Hiroko Ogata-Kawata;T. Uchiyama;Hiroe Kizawa;Hitomi Ueno-Yokohata;Ryota Shirai;Masanori Yoshida;M. Seki;K. Oki;J. Takita;S. Ogawa;T. Kitamura;Kimikazu Matsumoto;K. Hata;S. Goyama;N. Kiyokawa

前言：急性早幼粒细胞白血病(APL)具有独特的形态特征，典型的异常早幼粒细胞内含有天青颗粒。APL的基因组基础是t(15；17)(q22；q21)易位，诱导早幼粒细胞白血病(PML)与维甲酸受体-a(RARA)融合。带有PML-RARA的APL细胞对全反式维甲酸(ATRA)和三氧化二砷(ATO)有反应，最近的临床试验对典型的PML-RARA APL取得了良好的结果。虽然部分APL患者缺乏PMR-RARA，但大多数APL患者存在易位，包括RARA和其他基因，即PLZF、NPM和TBL1XR1。最终，所有已知的与APL相关的易位都涉及RARA，占APL的99%。然而，在其余的APL病例中无法检测到RARA重排，而这一小部分的分子机制仍不清楚。我们在这里分析了没有RARA易位的APL病例，并在大多数RARA阴性的APL患者中发现了一种新的RARB融合。材料和方法：我们首先进行了全基因组测序，以确定在一例RARA阴性的APL患者中潜在的基因组改变，并成功地确定了TBL1XR1和RARB之间的框内融合。由于编码视黄酸受体-b的RARB和RARA都是核受体超家族的成员，我们根据样本的可获得性，利用全转录组测序、RT-PCR和FISH，进一步寻找另外4例APL形态上缺乏RARA易位的RARB改变。5例RARA阴性的急性早幼粒细胞白血病病例包括1名男性和4名女性，患者的中位年龄为3岁(范围2-4岁)。所有病例均对全反式维甲酸耐药，多药化疗均为急性髓系白血病，但4例复发或未能缓解。为了研究这种新型融合在白血病发生中的功能作用，我们用TBL1XR1-RARB、RARB和PML-RARA转导了小鼠细胞系、小鼠骨髓细胞和人脐血。同时观察全反式维甲酸(ATRA)、三氧化二砷(ATO)的影响。结果：5例中有4例(80%)存在RARB易位(3例为TBL1XR1-RARB融合(图)，1例FISH检测到RARB重排，但无法确定其配对基因)。新的融合蛋白TBL1XR1-RARB可以同源二聚，并降低转录活性，对RARA和RARB都有显性的负面影响。转导TbL1XR1-RARB的U937细胞在全反式维甲酸作用下，细胞分化明显，CD11b表达增加，中性粒细胞分化明显。给予ATRA后，TBL1XR1-RARB的这些作用被ATRA取消，但与PML-RARA相比影响较小。ATO通过结合PML而导致PML-RARA的降解，但不影响转导TBL1XR1-RARB的细胞系。克隆复制实验表明，该重组TbL1XR1-RARB能增强小鼠骨髓的复制能力。TbL1XR1-RARB和PML-RAR均能阻断人脐血的分化，这一点也得到了形态特征的证实。结论：我们发现大多数RARA阴性的APL存在RARB易位，这在APL中定义了一个新的遗传亚群。与野生型RARB不同，TBL1XR1-RARB蛋白均二聚体，抑制维甲酸途径，并被证实具有致癌活性，PML-RARA也是如此。我们的研究证实维甲酸途径失调是APL的一个标志，但对ATRA的反应是部分的，这与RAR A阴性的APL对ATRA的临床耐药相一致。因此，在精确医学的背景下，应该对RARA阴性的APL病例进行RARB改变的筛查。披露北村：第一三共：研究资助。

Introduction: Acute promyelocytic leukemia (APL) is defined by unique morphological features, typically abnormal promyelocytes containing azurophilic granules. Genomic basis of APL is characterized by the translocation t(15;17)(q22;q21), inducing fusions between promyelocytic leukemia (PML) and retinoic acid receptor-a (RARA). APL cells with PML-RARA respond to all-trans retinoic acid (ATRA) and arsenic trioxide (ATO), and recent clinical trials have achieved excellent outcome for typical APL with PML-RARA . Although a certain fraction of APL cases lacks PMR-RARA, most of them had translocation including RARA and other genes, namely, PLZF, NPM, and TBL1XR1 . Eventually, all known APL-associated translocations involve RARA, accounting for 99% of APL. However, RARA rearrangement is unable to be detected in the rest of APL cases, and molecular mechanisms underlying this small subset is still unclear. We here analyzed APL cases without RARA translocation, and identified a novel RARB fusion in the majority of patients with RARA -negative APL. Materials and methods: We first performed whole-genome sequencing to identify potential genomic alterations in a case with RARA -negative APL, and successfully identified an in-frame fusion between TBL1XR1 and RARB . As RARB, encodes retinoic acid receptor-b, and RARA are both members of the nuclear receptor superfamily, we further searched for RARB alterations in additional 4 cases diagnosed APL morphologically lacking RARA translocation, using whole-transcriptome sequencing, RT-PCR, and FISH, according to sample availability. The five RARA -negative APL cases consist of one male and four females, and the median age of the cases were 3 years (range, 2-4 years of age). All cases were refractory to ATRA, and multiagent chemotherapy was given as acute myeloblastic leukemia but four cases suffered relapse or failed to achieve remission. To investigate functional effect of this novel fusion on leukemogenesis, we then transduced cell lines, bone marrow cells of mice, and human cord blood with TBL1XR1-RARB, RARB, and PML-RARA . Influence of all-trans retinoic acid (ATRA), arsenic trioxide (ATO) was also assessed. Results: Four of the five (80%) cases had RARB translocations (three had the TBL1XR1-RARB fusion (Figure), and one had RARB rearrangement detected by FISH although partner gene of the case could not be determined). The novel fusion protein, TBL1XR1-RARB, could homodimerize, and diminished transcriptional activity with a dominant negative effect on both RARA and RARB. Transduced U937 cell lines with TBL1XR1-RARB showed cell differentiation with increased expression of CD11b when treated with ATRA, and neutrophil differentiation was confirmed by morphology. These effect of TBL1XR1-RARB were cancelled by administration of ATRA, although the impact was partial compared to that of PML-RARA. ATO, leading PML-RARA degradation by biding PML, could not affect TBL1XR1-RARB transduced cell lines. Colony replating assay demonstrated that this TBL1XR1-RARB could enhance replating ability of murine bone marrow. Differentiation of human cord blood was blocked by TBL1XR1-RARB, as well as PML-RAR, which was also confirmed by morphological features. Conclusion: We found that the majority of RARA-negative APL had RARB translocation, defining a novel genetic subgroup in APL. Unlike wild type RARB, the TBL1XR1-RARB proteins homodimerize, suppress retinoic acid pathway, and are confirmed as having oncogenic potency, as well as PML-RARA. Our study confirmed that dysregulation in retinoic acid pathway was a hallmark of APL, however, response to ATRA was partial, which is concordant to clinical resistance to ATRA of RARA -negative APL. Thus, in the context of precision medicine, RARB alteration should be screened for RARA -negative APL cases. Disclosures Kitamura: Daiichi Sankyo: Research Funding.

RARB Translocations in Acute Promyelocytic Leukemia without Rara translocation

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