Fusion Gene In Acute Promyelocytic Leukemia Research Articles

Identification of a novel fusion gene, RARA::ANKRD34C, in acute promyelocytic leukemia.

Acute promyelocytic leukemia (APL) is a specific subtype of acute myeloid leukemia that is distinguished by the chromosomal translocation t(15;17)(q24;q21), which leads to the fusion of the promyelocytic leukemia (PML) gene with the retinoic acid receptor alpha (RARA). Recently, we identified a novel fusion gene in APL, RARA::ankyrin repeat domain 34C (ANKRD34C), identified its functions by morphological, cytogenetic, molecular biological and multiplex fluorescence in situ hybridization analyses, and demonstrated the potential therapeutic effect clinically and experimentally of all-trans retinoic acid (ATRA); the findings have important implications for the diagnosis and treatment of atypical APL.

Effects of interferon regulatory factor 9 on the biological phenotypes in PML-RARα-induced promyelocytic leukemia

目的研究急性早幼粒细胞白血病（APL）中干扰素调节因子9（IRF9）的表达特征、预后意义和生物学功能，探索IRF9作为潜在治疗靶点的临床转化意义。方法挖掘TCGA公共数据分析IRF9在APL中的表达水平及其表达高低对患者生存的影响；利用Dox诱导的慢病毒载体系统构建可诱导表达PML-RARα（PR）融合基因的U937细胞系，诱导PR融合基因早期表达并加入全反式维甲酸（ATRA）检测IRF9表达变化；构建可诱导表达IRF9的NB4细胞系，进行细胞分化和集落形成实验，初步探讨IRF9诱导表达对NB4白血病细胞生物学功能的影响。结果①TCGA数据库分析显示，在各种类型的AML中，IRF9在APL中表达水平最低且与预后不良相关。②成功构建可诱导表达PR融合基因的U937细胞系；PR表达引起IRF9蛋白水平下调，在NB4细胞系中IRF9表达缺失，ATRA处理后可表达上调。③成功构建可诱导表达IRF9的NB4细胞系，IRF9诱导表达促进NB4细胞的分化，且与较低剂量ATRA有协同促分化作用；IRF9诱导表达显著抑制了NB4细胞的集落形成能力。结论IRF9在APL中低表达且与预后不良相关，提示存在特异性调控机制；上调IRF9表达可发挥抗白血病效应，为其成为临床潜在治疗靶点奠定生物学基础。

Electrochemical DNA biosensor based on aldehyde-agarose hydrogel modified glassy carbon electrode for detection of PML/RARa fusion gene

A novel electrochemical biosensor based on a glassy carbon electrode (GCE) modified with aldehyde-agarose hydrogel films was developed for the detection of PML/RARa fusion gene in acute promyelocytic leukemia (APL). To generate the aldehyde groups that will react with probe, the diol groups in the activated agarose gels were transformed into aldehyde groups by reaction with NaIO 4. Immobilization is based on the reaction between aldehyde groups in aldehyde-agarose and primary amino groups in the probe. The probe was covalently immobilized on the surface of the GCE. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) was used to detect PML/RARa fusion gene in APL based on methylene blue (MB) as an electrochemical indicator. The electrochemical behavior and the determination of the probe in APL PML/RARa fusion gene using GCE were studied by DPV. The results indicated that in Tris–HCl buffer solution (pH 7.0), the relationship between the oxidation peak current of MB and the concentration of complementary strand was linear in the range of 4.0 × 10 −12 to 1.2 × 10 −11 M. The detection limit was estimated as 4.0 × 10 −12 M. The presented method exhibited excellent specificity for complementary and single-mismatch dsDNA after hybridization and will be applied to the assay of PCR-amplified DNA extracted from real sample showing the potentialities of this approach for routine analysis.

Nuclear Localization of the NuMA-RARα/RXRα Complex Is Necessary for Leukemogenesis in hCG-NuMA-RARα Transgenic Mice.

Acute promyelocytic leukemia (APL) is a model system for the role of aberrant transcription in cancer, and differentiation therapy in cancer treatment. APL is characterized by accumulation of abnormal promyelocytes in patient bone marrow, and by reciprocal chromosomal translocations involving retinoic acid receptor alpha (RARα). RARα heterodimerizes with the retinoid X receptor alpha (RXRα) and regulates transcription of genes associated with myeloid differentiation, in response to all trans retinoic acid (ATRA). Though PML-RARα is the most prevalent fusion gene in APL, four variant fusion genes (X-RARα) are currently known. By understanding the role that each fusion gene plays in APL, we may better understand the mechanism of this leukemia, and, by extension, the role of aberrant transcription factors and transcriptional regulation in cancer. Several lines of evidence suggest that X-RARα interact with and delocalize RXRα. We previously characterized the phenotype of the hCG-NuMA-RARα transgenic model (Sukhai et al, Oncogene, 2004). We observed that mice developed a myeloproliferative disease-like myeloid leukemia with promyelocytic features, with a variable onset peripheral blood phenotype (2–17 months). To further elucidate the role of RXRα in APL, we conditionally knocked out RXRα in hCG-NuMA-RARα mice. Phenotype analysis of NuMA-RARα+ mice was consistent with our previous results; animals developed a myeloproliferative disease-like myeloid leukemia within 4 months of birth. Hemizygous and homozygous RXRα conditional knockout mice were phenotypically normal as late as 12 months of age. The leukemic phenotype in NuMA-RARα+ mice was dependent on the presence of functional RXRα, as indicated by a progressive decrease in accumulation of promyelocytes, as well as Gr-1+, CD11b+, CD13+ and CD117+ cells in the bone marrow and peripheral blood of NuMA-RARα+ mice hemizygous and homozygous for the RXRα mutation, as compared to NuMA-RARα+ RXRα+/+ controls. We further observed that downstream target genes (e.g., C/EBPα) of NuMA-RARα were regulated in an RXRα-dependent manner, as these genes exhibited the greatest extent of deregulation in the presence of both alleles of functional RXRα, but had progressively less deregulated expression with loss of one or two functional alleles of RXRα. Furthermore, the NuMA-RARα/RXRα heterodimer was observed to bind to retinoic acid response elements in vitro. Strikingly, these observations mirrored what we observed in single transgenic mice with low vs. high transgene copy number. Mice with low copy number exhibited nuclear localization of the NuMA-RARα/RXRα complex, the greatest extent of deregulation of gene expression, and a rapid-onset phenotype. On the other hand, mice with high transgene copy number exhibited cytoplasmic localization of NuMA-RARα/RXRα, the least extent of gene deregulation, and an ameliorated leukemia similar to that observed in NuMA-RARα mice carrying the conditional mutation in RXRα. We therefore propose that NuMA-RARα cooperates with RXRa in the development of leukemia in hCG-NuMA-RARα transgenic mice, and that the localization of this complex to the nucleus is required for leukemogenesis in transgenic mice.