Dataset Information

Sequencing of DICER1 in sarcomas identifies biallelic somatic DICER1 mutations in an adult-onset embryonal rhabdomyosarcoma.

ABSTRACT: Sarcomas are rare and heterogeneous cancers. We assessed the contribution of DICER1 mutations to sarcoma development.The coding region of DICER1 was sequenced in 67 sarcomas using a custom Fluidigm Access Array. The RNase III domains were Sanger sequenced in six additional sarcomas to identify hotspot DICER1 variants.The median age of sarcoma diagnosis was 45.7 years (range: 3 months to 87.4 years). A recurrent embryonal rhabdomyosarcoma (ERMS) of the broad ligament, first diagnosed at age 23 years, harboured biallelic pathogenic somatic DICER1 variants (1 truncating and 1 RNase IIIb missense). We identified nine other DICER1 variants. One somatic variant (p.L1070V) identified in a pleomorphic sarcoma and one germline variant (c.2257-7A>G) may be pathogenic, but the others are considered to be benign.We show that deleterious DICER1 mutations underlie the genetic basis of only a small fraction of sarcomas, in particular ERMS of the urogenital tract.

SUBMITTER: de Kock L

PROVIDER: S-EPMC5518865 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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Sequencing of DICER1 in sarcomas identifies biallelic somatic DICER1 mutations in an adult-onset embryonal rhabdomyosarcoma.

de Kock Leanne L Rivera Barbara B Revil Timothée T Thorner Paul P Goudie Catherine C Bouron-Dal Soglio Dorothée D Choong Catherine S CS Priest John R JR van Diest Paul J PJ Tanboon Jantima J Wagner Anja A Ragoussis Jiannis J Choong Peter Fm PF Foulkes William D WD

British journal of cancer 20170518 12

<h4>Background</h4>Sarcomas are rare and heterogeneous cancers. We assessed the contribution of DICER1 mutations to sarcoma development.<h4>Methods</h4>The coding region of DICER1 was sequenced in 67 sarcomas using a custom Fluidigm Access Array. The RNase III domains were Sanger sequenced in six additional sarcomas to identify hotspot DICER1 variants.<h4>Results</h4>The median age of sarcoma diagnosis was 45.7 years (range: 3 months to 87.4 years). A recurrent embryonal rhabdomyosarcoma (ERMS) ...[more]

PMID: 28524158

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Project description:Embryonal rhabdomyosarcoma (ERMS) of the uterus has recently been shown to frequently harbor DICER1 mutations. Interestingly, only rare cases of extrauterine DICER1-associated ERMS, mostly located in the genitourinary tract, have been reported to date. Our goal was to study clinicopathologic and molecular profiles of DICER1-mutant (DICER1-mut) and DICER1-wild type (DICER1-wt) ERMS in a cohort of genitourinary tumors. We collected a cohort of 17 ERMS including nine uterine (four uterine corpus and five cervix), one vaginal, and seven urinary tract tumors. DNA sequencing revealed mutations of DICER1 in 9/9 uterine ERMS. All other ERMS of our cohort were DICER1-wt. The median age at diagnosis of patients with DICER1-mut and DICER1-wt ERMS was 36 years and 5 years, respectively. Limited follow-up data (available for 15/17 patients) suggested that DICER1-mut ERMS might show a less aggressive clinical course than DICER1-wt ERMS. Histological features only observed in DICER1-mut ERMS were cartilaginous nodules (6/9 DICER1-mut ERMS), in one case accompanied by foci of ossification. Recurrent mutations identified in both DICER1-mut and DICER1-wt ERMS affected KRAS, NRAS, and TP53. Copy number analysis revealed similar structural variations with frequent gains on chromosomes 2, 3, and 8, independent of DICER1 mutation status. Unsupervised hierarchical clustering of array-based whole-genome DNA methylation data of our study cohort together with an extended methylation data set including different RMS subtypes from genitourinary and extra-genitourinary locations (n = 102), revealed a distinct cluster for DICER1-mut ERMS. Such tumors clearly segregated from the clusters of DICER1-wt ERMS, alveolar RMS, and MYOD1-mutant spindle cell and sclerosing RMS. Only one tumor, previously diagnosed as ERMS arising in the maxilla of a 6-year-old boy clustered with DICER1-mut ERMS of the uterus. Subsequent sequencing analysis identified two DICER1 mutations in the latter case. Our results suggest that DICER1-mut ERMS might qualify as a distinct subtype in future classifications of RMS.

Project description:Malignant ectomesenchymoma (MEM) is an exceedingly rare pediatric sarcoma with a predilection for infants and young children and is composed of dual malignant mesenchymal and neuroectodermal components. Microscopically, MEM displays areas of rhabdomyosarcoma (RMS) with intermixed neuronal/neuroblastic foci. The molecular alterations associated with MEM and its relationship with embryonal RMS (ERMS) and malignant peripheral nerve sheath tumor (MPNST) have not yet been elucidated. In this study we used whole-transcriptome sequencing in 2 MEM index cases with available frozen tissue, followed by screening of the identified genetic abnormalities in 5 additional cases. No candidate fusion genes were detected by FusionSeq analysis; however, the mutation detection algorithms revealed HRAS and PTPRD hotspot mutations in both index cases, with 1 case harboring an additional FBXW7 mutation. As these mutation profiles have been previously described in ERMS we have tested their incidence in a control group of 7 age-matched ERMS. In addition, the gene signature of MEM was compared with that of RMS, MPNST, and neuronal lineage. All 7 MEM patients were male, with a mean age of 7.5 months (range, 0.6 to 17 mo). All except 1 occurred in the pelvic/urogenital region. Most cases showed ERMS elements, with occasional spindle or undifferentiated/round cell areas. The intermixed neuroectodermal components were mostly scattered ganglion cells, ganglioneuroma, or ganglioneuroblastoma. By Sanger sequencing, 6 of 7 (86%) MEMs had HRAS mutations, with no additional case harboring PTPRD or FBXW7 mutations. The only case lacking HRAS mutation showed neuroblastic micronodules without ganglion cells. The trimethylation at lysine 27 of histone H3 (H3K27me3) expression, typically lost in MPNST, was retained in all cases. In the control ERMS group, 5 of 7 (71%) showed RAS mutations, equally distributed among NRAS, KRAS, and HRAS genes. The expression profiling of MEM showed upregulation of skeletal muscle and neuronal genes, with no significant overlap with MPNST. Our results of common HRAS mutations and composite gene signature with RMS and neuronal/neuroblastic elements suggest a closer genetic link of MEM to RMS rather than to MPNST.

Dataset Information

Sequencing of DICER1 in sarcomas identifies biallelic somatic DICER1 mutations in an adult-onset embryonal rhabdomyosarcoma.

Publications

Sequencing of DICER1 in sarcomas identifies biallelic somatic DICER1 mutations in an adult-onset embryonal rhabdomyosarcoma.

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