Browsing by Author "Vult von Steyern, Fredrik"

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    Comprehensive Genetic Analysis Identifies a Pathognomonic NAB2/STAT6 Fusion Gene, Nonrandom Secondary Genomic Imbalances, and a Characteristic Gene Expression Profile in Solitary Fibrous Tumor
    (Genes, Chromosomes and Cancer, 2013) Mohajeri, Arezoo; Tayebwa, Johnbosco; Collin, Anna; Nilsson, Jenny; Magnusson, Linda; Vult von Steyern, Fredrik; Brosj, Otte; Domanski, Henryk A.; Larsson, Olle; Sciot, Raf; Debiec-Rychter, Maria; Hornick, Jason L.; Mandahl, Nils; Nord, Karolin H.; Mertens, Fredrik
    Solitary fibrous tumor (SFT) is a mesenchymal neoplasm displaying variable morphologic and clinical features. To identify pathogenetically important genetic rearrangements, 44 SFTs were analyzed using a variety of techniques. Chromosome banding and fluorescence in situ hybridization (FISH) showed recurrent breakpoints in 12q13, clustering near the NAB2 and STAT6 genes, and single nucleotide polymorphism array analysis disclosed frequent deletions affecting STAT6. Quantitative real-time PCR revealed high expression levels of the 5’-end of NAB2 and the 3’-end of STAT6, which at deep sequencing of enriched DNA corresponded to NAB2/STAT6 fusions. Subsequent reverse-transcriptase PCR (RT-PCR) analysis identified a NAB2/STAT6 fusion in 37/41 cases, confirming that this fusion gene underlies the pathogenesis of SFT. The hypothesis that the NAB2/STAT6 fusions will result in altered properties of the transcriptional co-repressor NAB2 - a key regulator of the early growth response 1 (EGR1) transcription factor – was corroborated by global gene expression analysis; SFTs showed deregulated expression of EGR1 target genes, as well as of other, developmentally important genes. We also identified several nonrandom secondary changes, notably loss of material from 13q and 14q. As neither chromosome banding nor FISH analysis identify more than a minor fraction of the fusion-positive cases, and because multiple primer combinations are required to identify all possible fusion transcripts by RT-PCR, alternative diagnostic markers might instead be found among deregulated genes identified at global gene expression analysis. Indeed, using immunohistochemistry on tissue microarrays, the top up-regulated gene, GRIA2, was found to be differentially expressed also at the protein level.
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    A novel SERPINE1–FOSB fusion gene results in transcriptional up-regulation of FOSB in pseudomyogenic haemangioendothelioma
    (The Journal of Pathology, 2014) Walther, Charles; Tayebwa, Johnbosco; Lilljebjorn, Henrik; Magnusson, Linda; Nilsson, Jenny; Vult von Steyern, Fredrik; Øra, Ingrid; Domanski, Henryk A.; Fioretos, Thoas; Nord, Karolin H.; Fletcher, Christopher D. M.
    Pseudomyogenic haemangioendothelioma (PHE) is an intermediate malignant vascular soft tissue tumour primarily affecting children and young adults. The molecular basis of this neoplasm is unknown. We here used chromosome banding analysis, fluorescence in situ hybridization (FISH), mRNA sequencing, RT–PCR and quantitative realtime PCR on a series of morphologically well-characterized PHEs to show that a balanced translocation, t(7;19)(q22;q13), detected as the sole cytogenetic aberration in two cases, results in fusion of the SERPINE1 and FOSB genes. This translocation has not been observed in any other bone or soft tissue tumour. Interphase FISH on sections from eight additional PHEs identified the same SERPINE1–FOSB fusion in all cases. The role of SERPINE1, which is highly expressed in vascular cells, in this gene fusion is probably to provide a strong promoter for FOSB, which was found to be expressed at higher levels in PHEs than in other soft tissue tumours. FOSB encodes a transcription factor belonging to the FOS family of proteins, which, together with members of the JUN family of transcription factors, are major components of the activating protein 1 (AP-1) complex. Further studies are needed to understand the cellular impact of the aberrant expression of the FOSB gene, but as the t(7;19) resulting in the SERPINE1–FOSB fusion seems to be pathognomonic for PHE, FISH or RT–PCR could be useful for differential diagnostic purposes.
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    Recurrent PRDM10 Gene Fusions in Undifferentiated Pleomorphic Sarcoma
    (Clinical Cancer Research, 2015) Hofvander, Jakob; Tayebwa, Johnbosco; Nilsson, Jenny; Magnusson, Linda; Brosjo, Otte; Larsson, Olle; Vult von Steyern, Fredrik; Mandahl, Nils; Fletcher, Christopher D.M.; Mertens, Fredrik
    Undifferentiated pleomorphic sarcoma (UPS) is defined as a sarcoma with cellular pleomorphism and no identifiable line of differentiation. It is typically a high-grade lesion with a metastatic rate of about one third. No tumor-specific rearrangement has been identified, and genetic markers that could be used for treatment stratification are lacking. We performed transcriptome sequencing (RNA-Seq) to search for novel gene fusions. Experimental design: RNA-Seq, FISH, and/or various PCR methodologies were used to search for gene fusions and rearrangements of the PRDM10 gene in 84 soft tissue sarcomas. Results: Using RNA-Seq, two cases of UPS were found to display novel gene fusions, both involving the transcription factor PRDM10 as the 30 partner and either MED12 or CITED2 as the 50 partner gene. Further screening of 82 soft tissue sarcomas for rearrangements of the PRDM10 locus revealed one more UPS with a MED12/PRDM10 fusion. None of these genes has been implicated in neoplasia-associated gene fusions before. Conclusions: Our results suggest that PRDM10 fusions are present in around 5% of UPS. Although the fusion-positive cases in our series showed the same nuclear pleomorphism and lack of differentiation as other UPS, it is noteworthy that all three were morphologically low grade and that none of the patients developed metastases. Thus, PRDM10 fusion-positive sarcomas may constitute a clinically important subset of UPS.
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    RNA sequencing of sarcomas with simple karyotypes: identification and enrichment of fusion transcripts
    (Laboratory Investigation, 2015) Hofvander, Jakob; Tayebwa, Johnbosco; Nilsson, Jenny; Magnusson, Linda; Brosjö, Otte; Larsson, Olle; Vult von Steyern, Fredrik; Domanski, Henryk A.; Mandahl, Nils; Mertens, Fredrik
    Gene fusions are neoplasia-associated mutations arising from structural chromosomal rearrangements. They have a strong impact on tumor development and constitute important diagnostic markers. Malignant soft tissue tumors (sarcomas) constitute a heterogeneous group of neoplasms with 450 distinct subtypes, each of which is rare. In addition, there is considerable morphologic overlap between sarcomas and benign lesions. Several subtypes display distinct gene fusions, serving as excellent biomarkers. The development of methods for deep sequencing of the complete transcriptome (RNA-Seq) has substantially improved the possibilities for detecting gene fusions. With the aim of identifying new gene fusions of biological and clinical relevance, eight sarcomas with simple karyotypes, ie, only one or a few structural rearrangements, were subjected to massively parallel paired-end sequencing of mRNA. Three different algorithms were used to identify fusion transcripts from RNA-Seq data. Three novel (KIAA2026-NUDT11, CCBL1-ARL1, and AFF3-PHF1) and two previously known fusions (FUS-CREB3L2 and HAS2-PLAG1) were found and could be verified by other methods. These findings show that RNA-Seq is a powerful tool for detecting gene fusions in sarcomas but also suggest that it is advisable to use more than one algorithm to analyze the output data as only two of the confirmed fusions were reported by more than one of the gene fusion detection software programs. For all of the confirmed gene fusions, at least one of the genes mapped to a chromosome band implicated by the karyotype, suggesting that sarcomas with simple karyotypes constitute an excellent resource for identifying novel gene fusions.