ABSTRACT: Retroviral Integration Mutagenesis in Mice and Comparative Analysis in Human AML Identify Reduced PTP4A3 Expression as a Prognostic Indicator
Project description:Acute myeloid leukemia (AML) results from multiple genetic and epigenetic aberrations, many of which remain unidentified. Frequent loss of large chromosomal regions marks haplo-insufficiency as one of the major mechanisms contributing to leukemogenesis. However, which haplo-insufficient genes (HIGs) are involved in leukemogenesis is largely unknown and powerful experimental strategies aimed at their identification are currently lacking. Here, we present a new approach to discover HIGs, using retroviral integration mutagenesis in mice in which methylated viral integration sites and neighbouring genes were identified. In total we mapped 6 genes which are flanked by methylated viral integration sites (mVIS). Three of these, i.e., Lrmp, Hcls1 and Prkrir, were up regulated and one, i.e., Ptp4a3, was down regulated in the affected tumor. Next, we investigated the role of PTP4A3 in human AML and we show that PTP4A3 expression is a negative prognostic indicator, independent of other prognostic parameters. In conclusion, our novel strategy has identified PTP4A3 to potentially have a role in AML, on one hand as a candidate HIG contributing to leukemogenesis in mice and on the other hand as a prognostic indicator in human AML. We designed a new strategy to specifically identify DNA methylated proviral integrations on a large scale by combining methylated DNA immunoprecipitation (MeDIP), inverse PCR and promoter array hybridization. We used 6 murine leukemia samples from a previous screen that were induced by injecting Gr 1.4 MLV into newborn mice.
Project description:Acute myeloid leukemia (AML) results from multiple genetic and epigenetic aberrations, many of which remain unidentified. Frequent loss of large chromosomal regions marks haplo-insufficiency as one of the major mechanisms contributing to leukemogenesis. However, which haplo-insufficient genes (HIGs) are involved in leukemogenesis is largely unknown and powerful experimental strategies aimed at their identification are currently lacking. Here, we present a new approach to discover HIGs, using retroviral integration mutagenesis in mice in which methylated viral integration sites and neighbouring genes were identified. In total we mapped 6 genes which are flanked by methylated viral integration sites (mVIS). Three of these, i.e., Lrmp, Hcls1 and Prkrir, were up regulated and one, i.e., Ptp4a3, was down regulated in the affected tumor. Next, we investigated the role of PTP4A3 in human AML and we show that PTP4A3 expression is a negative prognostic indicator, independent of other prognostic parameters. In conclusion, our novel strategy has identified PTP4A3 to potentially have a role in AML, on one hand as a candidate HIG contributing to leukemogenesis in mice and on the other hand as a prognostic indicator in human AML.
Project description:High VEGFC mRNA expression of AML blasts is related to increased in vitro and in vivo drug resistance. The prognostic significance of VEGFC on long-term outcome and its associated gene expression profiles remain to be defined. We studied the effect of VEGFC on treatment outcome and investigated gene expression profiles associated with VEGFC using microarray data of 525 adult and 100 pediatric AML patients. High VEGFC expression appeared strongly associated with reduced complete remission rate, reduced overall and event-free survival (OS and EFS) in adult AML. Multivariable analysis established high VEGFC as prognostic indicator independent of cytogenetic risk, FLT3-ITD, NPM1, CEBPA, age and WBC. Also in pediatric AML high VEGFC was related to reduced OS. A unique series of differentially expressed genes was identified that distinguished AML with high VEGFC from AML with low VEGFC, i.e., 331 upregulated genes (representative of proliferation, VEGF-receptor activity, signal transduction) and 44 downregulated genes (e.g. related to apoptosis) consistent with a role in enhanced chemoresistance. In conclusion, high VEGFC predicts adverse long-term prognosis and provides prognostic information in addition to well-known prognostic factors. 98 bone marrow and peripheral blood samples were collected at diagnosis and frozen. They were later thawed and hybridized to Affymetrix U133 Plus 2.0 arrays.
Project description:High VEGFC mRNA expression of AML blasts is related to increased in vitro and in vivo drug resistance. The prognostic significance of VEGFC on long-term outcome and its associated gene expression profiles remain to be defined. We studied the effect of VEGFC on treatment outcome and investigated gene expression profiles associated with VEGFC using microarray data of 525 adult and 100 pediatric AML patients. High VEGFC expression appeared strongly associated with reduced complete remission rate, reduced overall and event-free survival (OS and EFS) in adult AML. Multivariable analysis established high VEGFC as prognostic indicator independent of cytogenetic risk, FLT3-ITD, NPM1, CEBPA, age and WBC. Also in pediatric AML high VEGFC was related to reduced OS. A unique series of differentially expressed genes was identified that distinguished AML with high VEGFC from AML with low VEGFC, i.e., 331 upregulated genes (representative of proliferation, VEGF-receptor activity, signal transduction) and 44 downregulated genes (e.g. related to apoptosis) consistent with a role in enhanced chemoresistance. In conclusion, high VEGFC predicts adverse long-term prognosis and provides prognostic information in addition to well-known prognostic factors.
Project description:Retroviral insertional mutagenesis (RIM) is a powerful tool in cancer genomics. Transgenic mice expressing two potent collaborating oncogenes in the germline, Myc and Runx2, develop rapid onset tumours that can be accelerated and rendered polyclonal by neonatal infection with MoMLV. Deep sequencing of lymphomas from infected Runx2/Myc mice revealed a network of progression genes. Transcriptional analysis of basal expression levels in transgenic cells showed that the progression network showed strong evidence of clonal selection beyond gene expression level. We examined the gene expression profile of triplicate 10 day old thymus from CD2-Myc/CD2-Runx2 and C57/CBA mice to examine early gene changes in comparison to RIM targets in end stage tumours. We found no significant relationship between basal expression in the transgenic system and genes that were targets for retroviral integration.
Project description:The CCAAT enhancer binding protein alpha (C/EBPalpha) transcription factor plays a key role in the regulation of growth and differentiation of the granulocytic lineage in the hematopoietic system and CEBPA (encoding C/EBPalpha) is often mutated or deregulated in AML patients. Consistently, mice lacking C/EBPalpha have no mature neutrophils and die within a few hours. However, homozygous knockin mice in which wild type Cebpa has been replaced with a mutant allele (BRM2), which abolish the growth-repressing ability of C/EBPalpha, are viable, but at 8 weeks of age they display myeloid dysplasia with absence of neutrophil granulocytes. Strikingly, in older CebpaBRM2/BRM2 knockin mice the myeloid dysplastic phenotype progress into other myeloid malignancies such as myeloid proliferative syndrome and acute myeloid leukemia-like malignancy. This strongly suggests that secondary mutations in other loci must occur when developing leukemia in the CebpaBRM2/BRM2. In order to identify genes that cooperate with Cebpa mutations in the development of leukemia in CebpaBRM2/BRM2 mice a so-called retroviral insertion mutagenesis screen was performed. Inbred newborn CebpaBRM2/BRM2 and wildtype mice were injected with SRS19-6 retrovirus, which incorporated into the genome and resulted in activation of oncogenes and leukemic progression. When leukemia was evident the mice were euthanized and analyzed. As expected the CebpaBRM2/BRM2 mice had a shorter latency than wildtype mice (186 vs. 276 days). The mice had enlarged spleen, thymus, and/or lymph nodes and were thoroughly investigated by histology, flow cytometry and southern in order to determine the leukemic phenotypes. Most of the CebpaBRM2/BRM2 mice developed an AML-like phenotype, whereas T cell leukemias were most prominent in wildtype mice, showing that mutating Cebpa specifically directs leukemic progression towards a myeloid direction. Genomic instability was analyzed by CGH. Finally, the retroviral insertion loci were identified through a splinkerette-aided PCR strategy. This led to the identification of several novel putative and previously unexplored oncogenes, which might collaborate with mutated Cebpa in the development of AML. Keywords: Disease state analysis In order to identify genes that cooperate with Cebpa mutations in the development of leukemia in CebpaBRM2/BRM2 mice a so-called retroviral insertion mutagenesis screen was performed. Inbred newborn CebpaBRM2/BRM2 and wildtype mice were injected with SRS19-6 retrovirus, which incorporated into the genome and resulted in activation of oncogenes and leukemic progression. When leukemia was evident the mice were euthanized and analyzed. GDNA from tumour tissues were analyzed by CGH using tail gDNA as reference.
Project description:Retroviral integration sites were mapped using inverse PCR to assess preferred integration sites of this virus in the genome after infection with the retrovirus and its impact on gene expression. Inverse PCR was applied on genomic DNA to identify retroviral integration sites. Inverse PCR allows to identify multiple genomic insertions of a gene trap virus in parallel.
Project description:Acute myeloid leukemia (AML) is a heterogeneous hematologic malignancy driven largely by gene mutations and epigenetic modifications. The Nucleoporin 98kDa (NUP98) gene is a component of the nuclear pore complex that also plays a role as an intranuclear transcription scaffold. Fusion genes involving NUP98 have been recognized in a wide array of hematologic malignancy, most commonly AML4. Among over 30 partner genes known to be fused to NUP98 in human leukemia, NSD1 (for Nuclear receptor-binding SET Domain protein 1) (NSD1) is the most common. Patients with NUP98::NSD1 gene fusions have a poor prognosis, and the leukemic blasts frequently have an internal tandem duplication (ITD) of the FMS-related tyrosine kinase 3 gene (FLT3) gene accompanying the NUP98::NSD1 fusion. Previous reports have utilized BM transduction with retroviral vectors followed by transplantation into recipient mice to model AML driven by a NUP98::NSD1 fusion. Given that genetically engineered mice offer certain advantages over retroviral transduction models, such as consistent transgene expression and integration effects, lack of ionizing radiation, and transferability between investigators, we generated NUP98::Nsd1 transgenic mice.
Project description:To examine the role of PAX5 alterations in leukemogenesis, we performed mutagenesis screens of mice heterozygous for a loss-of-function Pax5 allele. Both chemical and retroviral mutagenesis resulted in a significantly increased penetrance and reduced latency of leukemia, with a shift to B-lymphoid lineage. We observed a range of maturation of lymphoid tumors, and genomic profiling identified a high frequency of secondary genomic mutations, deletions and retroviral insertions targeting B-lymphoid development, including Pax5, and additional genes and pathways known to be mutated in ALL, including tumor suppressors, Ras and JAK-STAT signaling. These results support the notion that loss-of-function of PAX5 is a central event in leukemogenesis and contributes to the arrest in lymphoid maturation characteristic of this disease. Moreover, we validate the role of mutations in additional pathways and demonstrate that sequential acquisition of genetic alterations is required for establishment of leukemia.
Project description:Acute myeloid leukemia (AML) is a malignant tumor of the hematological system. Because of its characteristics of recurrence, refractory and chemoresistance, new therapeutic targets need to be identified. Adhesion and proliferation are characteristics of AML cells, and critical steps in inducing chemotherapy resistance. In this study, we reported that UNC5B inhibits AML cell bone marrow adhesion, inhibits AML cell proliferation and increases sensitivity to chemotherapy. Mechanistically, RNA sequencing (RNA-seq) and experimental results revealed that overexpression of UNC5B inhibits adhesion and proliferation signaling pathways and inhibits the expression of MPZL1, CLDN23, IGF2 and WNT7B. In conclusion, our findings suggest that UNC5B serves as a prognostic indicator and a potential therapeutic target for AML.