Project description:Acute promyelocytic leukemia (APL) is characterized by a specific t(15;17) chromosome translocation that generates the promyelocytic leukemia/retinoic acid receptor-α (PML/RARα) fusion gene. However, the global association between PML/RARα and transcriptional co-regulators, and the rules of their association in governing the key processes during the leukemogenesis remain obscure. Here, we performed the genome-wide binding profiling of PML/RARα, HDAC1 and P300, in NB4, an APL patient-derived cell line. We found that PML/RARα targets could be classified into two classes. Moreover, we also performed ChIP-seq of H3K27ac to determine super-enhancers in NB4. We identified a novel function of PML/RARα in super-enhancer regulation during the leukemogenesis of APL.
Project description:We defined the RARα interactome in the MDA-MB453 breast cancer cell line genetically engineered to over-express an N-terminally tagged version of the nuclear retinoic acid receptor. Twenty eight nuclear proteins which interact with RARα and whose interaction is stimulated or reduced by the pan-RAR ligand, all-trans retinoic acid (ATRA) were identified. Given the potential significance of the S100A3 calcium-binding protein in the control of tumor progression, we focused our attention on this factor. Using the two models represented by the ATRA-sensitive SKBR3 and MCF7 breast cancer cell lines characterized by constitutive expression of S100A3 and RARα, we demonstrate that the endogenous forms of S100A3 and RARα interact in physiological conditions. The interaction of S100A3 with RARα is cell context independent and it is observed not only in breast cancer but also in acute promyelocytioc leukemia (APL) cells, characterized by expression of the RARα-derived PML-RARα oncogene, which is the product of the t(15:17) chromosomal translocation. S100A3 interacts directly and specifically with RARα and PML-RARα, being unable to bind other members of the RAR/RXR family of retinoid nuclear receptors. The interaction surface maps to the carboxyl-terminal region of the RARα ligand binding domain. Binding of S100A3 to RARα and PML-RARα controls the constitutive and ATRA-dependent degradation of the two receptors. Silencing of the S100A3 gene decreases the amounts of RARα in breast SK-BR-3 and lung A549 cancer cells, rendering them more refractory to the anti-proliferative action of ATRA. In SK-BR-3 cells, this effect is accompanied by a decrease in the lactogenic/differentiating action of ATRA. In APL-derived NB4 cells, S100A3 knock-down reduces the amounts of both RARα and PML-RARα. Contemporaneous down-regulation of the two receptors is associated with an increase in the basal and ATRA-induced expression of many granulocytic differentiation markers. Opposite on RARα and PML-RARα levels as well as ATRA induced differentiation markers are observed upon over-expression of S100A3 in NB4 cells.
Project description:Acute promyeloid leukemia (APL) is characterized by the oncogenic fusion protein PML/RARα, a major etiological agent in APL. Although PML/RARα is critical, the molecular mechanisms remains largely unknown. Here, using an inducible system, we comprehensively analyzed the 3D genome organization in myloid cells and its reorganizationn after PML/RARα induction, and performed additional analysis in patient-derived APL cells with native PML/RARα. We discovered that PML/RARα mediate extensive chromatin interactions genome-wide. Globally, it redefine the chromatin topology of the in myloid genome toward a more condensed configuration in APL cells; locally, it intrude RNAPII-associated interaction dmains, interrupt myeloid-specific transcription factors binding at enhancers and super-enahncers, and lead to transcriptional repression of genes critical for myeloid differentiation and maturation. Together, our results provide novel insights of a topological framework for PML/RARα’s roles in transforming myeloid into leukemia, likely a general mechanism for oncogenic fusion proteins in cancers.
Project description:Acute promyeloid leukemia (APL) is characterized by the oncogenic fusion protein PML/RARα, a major etiological agent in APL. Although PML/RARα is critical, the molecular mechanisms remains largely unknown. Here, using an inducible system, we comprehensively analyzed the 3D genome organization in myloid cells and its reorganizationn after PML/RARα induction, and performed additional analysis in patient-derived APL cells with native PML/RARα. We discovered that PML/RARα mediate extensive chromatin interactions genome-wide. Globally, it redefine the chromatin topology of the in myloid genome toward a more condensed configuration in APL cells; locally, it intrude RNAPII-associated interaction dmains, interrupt myeloid-specific transcription factors binding at enhancers and super-enahncers, and lead to transcriptional repression of genes critical for myeloid differentiation and maturation. Together, our results provide novel insights of a topological framework for PML/RARα’s roles in transforming myeloid into leukemia, likely a general mechanism for oncogenic fusion proteins in cancers.
Project description:Acute promyeloid leukemia (APL) is characterized by the oncogenic fusion protein PML/RARα, a major etiological agent in APL. Although PML/RARα is critical, the molecular mechanisms remains largely unknown. Here, using an inducible system, we comprehensively analyzed the 3D genome organization in myloid cells and its reorganizationn after PML/RARα induction, and performed additional analysis in patient-derived APL cells with native PML/RARα. We discovered that PML/RARα mediate extensive chromatin interactions genome-wide. Globally, it redefine the chromatin topology of the in myloid genome toward a more condensed configuration in APL cells; locally, it intrude RNAPII-associated interaction dmains, interrupt myeloid-specific transcription factors binding at enhancers and super-enahncers, and lead to transcriptional repression of genes critical for myeloid differentiation and maturation. Together, our results provide novel insights of a topological framework for PML/RARα’s roles in transforming myeloid into leukemia, likely a general mechanism for oncogenic fusion proteins in cancers.
Project description:Acute Promyelocytic Leukemia is characterized by the accumulation in the blood and bone marrow of promyelocytes. The PML/RARα fusion protein is identified as the primary abnormality implicated in the pathology, and is believed to prevent transcription of genes necessary for normal myeloid development and differentiation. Identifying its targets is critical to comprehend the road to pathogenesis. To understand how PML/RARα, in the absence of secondary lesions, alters gene expression, DNA methylation and proliferation we used a novel experimental and sorting strategy to study normal versus preleukemic promyelocytes in vivo. Expression and methylation profiling analyses were performed on highly purified samples. Surprisingly, despite its ability to initiate leukemia, PML/RARα had overall minor effects on both the transcriptome and epigenome. Important regulators of the myeloid maturation program were not altered but, remarkably, PML/RARα promyelocytes showed strong downregulation of secondary and tertiary granule genes. Subtle changes were also observed on the DNA methylation profile, with PML/RARα predominantly mediating hypomethylation. We performed intersection studies between altered loci and previously described PML/RARα binding sites but found little overlap. Importantly, we show for the first time that PML/RARα on its own increases proliferation, and that this increased proliferation correlates with the ability to initiate leukemia. DNA methylation profiling in CD34(+) early promyelocytes and CD34(-) late promyelocytes cells from PML-RARa transgenic mice vs. control mice.
Project description:Acute Promyelocytic Leukemia is characterized by the accumulation in the blood and bone marrow of promyelocytes. The PML/RARα fusion protein is identified as the primary abnormality implicated in the pathology, and is believed to prevent transcription of genes necessary for normal myeloid development and differentiation. Identifying its targets is critical to comprehend the road to pathogenesis. To understand how PML/RARα, in the absence of secondary lesions, alters gene expression, DNA methylation and proliferation we used a novel experimental and sorting strategy to study normal versus preleukemic promyelocytes in vivo. Expression and methylation profiling analyses were performed on highly purified samples. Surprisingly, despite its ability to initiate leukemia, PML/RARα had overall minor effects on both the transcriptome and epigenome. Important regulators of the myeloid maturation program were not altered but, remarkably, PML/RARα promyelocytes showed strong downregulation of secondary and tertiary granule genes. Subtle changes were also observed on the DNA methylation profile, with PML/RARα predominantly mediating hypomethylation. We performed intersection studies between altered loci and previously described PML/RARα binding sites but found little overlap. Importantly, we show for the first time that PML/RARα on its own increases proliferation, and that this increased proliferation correlates with the ability to initiate leukemia.
Project description:Histone demethylase KDM3B is considered to play a critical role in leukemogenesis. To the best of our knowledge, this study is the first attempt to probe the detailed genetic and epigenetic mechanisms underlying the regulation of KDM3B in the development of APL from the perspectives of multi-layer omics. Results of the present study demonstrate that KDM3B exerts anti-APL effect by directly modulating H3K9me1/me2 levels to maintain compact chromatin status, but also indicate the interaction between KDM3B and PML/RARα regulates degradation of PML/RARα.
Project description:Histone demethylase KDM3B is considered to play a critical role in leukemogenesis. To the best of our knowledge, this study is the first attempt to probe the detailed genetic and epigenetic mechanisms underlying the regulation of KDM3B in the development of APL from the perspectives of multi-layer omics. Results of the present study demonstrate that KDM3B exerts anti-APL effect by directly modulating H3K9me1/me2 levels to maintain compact chromatin status, but also indicate the interaction between KDM3B and PML/RARα regulates degradation of PML/RARα.
Project description:Epigenetic abnormalities are frequently involved in the initiation and progression of cancers including acute myeloid leukemia (AML). A subtype of AML, Acute promyelocytic leukemia (APL), is mainly driven by a specific oncogenic fusion event of PML-RARα. PML-RARα was reported as a transcription repressor through the interaction with NCoR/HDAC complexes leading to the mis-suppression of its target genes and differentiation blockage. While previous studies were mainly focused on the connection of histone acetylation, it is still largely unknown whether alternative epigenetics mechanisms are involved in APL progression. KDM5A is a demethylase of histone H3 lysine 4 di- and tri- methylations (H3K4me2/3) and a transcription corepressor. Here, we found that the loss of KDM5A led to APL NB4 cell differentiation and retarded growth. Mechanistically, through epigenomics and transcriptomics analyses, we detected KDM5A binding in 1,889 genes, with the majority of the binding events at promoter regions. KDM5A suppressed the expression of 621 genes, including 42 PML-RARα target genes primarily by controlling the H3K4me2 in the promoters and 5’ end intragenic regions. In addition, a recently reported pan-KDM5 inhibitor, CPI-455 on its own could phenocopy the differentiation effects as KDM5A loss in NB4 cells. CPI-455 treatment or KDM5A knockout could greatly sensitize NB4 cells to ATRA induced differentiation. Our findings indicated that KDM5A contributed to the differentiation blockage in the APL cell line NB4, and inhibition of KDM5A could greatly potentiate NB4 differentiation.