Genomic and transcriptomic analyses of thyroid cancers identify DICER1 somatic mutations in adult follicular-patterned RAS-like tumors.

Background: Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer (TC). Several genomic and transcriptomic studies explored the molecular landscape of follicular cell-derived TCs, and BRAFV600E, RAS mutations, and gene fusions are well-established drivers. DICER1 mutations were described in specific sets of TC patients but represent a rare event in adult TC patients. Methods: Here, we report the molecular characterization of 30 retrospective follicular cell-derived thyroid tumors, comprising PTCs (90%) and poorly differentiated TCs (10%), collected at our Institute. We performed DNA whole-exome sequencing using patient-matched control for somatic mutation calling, and targeted RNA-seq for gene fusion detection. Transcriptional profiles established in the same cohort by microarray were investigated using three signaling-related gene signatures derived from The Cancer Genome Atlas (TCGA). Results: The occurrence of BRAFV600E (44%), RAS mutations (13%), and gene fusions (13%) was confirmed in our cohort. In addition, in two patients lacking known drivers, mutations of the DICER1 gene (p.D1709N and p.D1810V) were identified. DICER1 mutations occur in two adult patients with follicular-pattern lesions, and in one of them a second concurrent DICER1 mutation (p.R459*) is also observed. Additional putative drivers include ROS1 gene (p.P2130A mutation), identified in a patient with a rare solid-trabecular subtype of PTC. Transcriptomics indicates that DICER1 tumors are RAS-like, whereas the ROS1-mutated tumor displays a borderline RAS-/BRAF-like subtype. We also provide an overview of DICER1 and ROS1 mutations in thyroid lesions by investigating the COSMIC database. Conclusion: Even though small, our series recapitulates the genetic background of PTC. Furthermore, we identified DICER1 mutations, one of which is previously unreported in thyroid lesions. For these less common alterations and for patients with unknown drivers, we provide signaling information applying TCGA-derived classification.

The genomics of desmoplastic small round cell tumor reveals the deregulation of genes related to DNA damage response, epithelial-mesenchymal transition, and immune response.

BACKGROUND: Desmoplastic small round cell tumor (DSRCT) is a rare, aggressive, and poorly investigated simple sarcoma with a low frequency of genetic deregulation other than an Ewing sarcoma RNA binding protein 1 (EWSR1)-Wilm's tumor suppressor (WT1) translocation. We used whole-exome sequencing to interrogate six consecutive pre-treated DSRCTs whose gene expression was previously investigated. METHODS: DNA libraries were prepared from formalin-fixed, paraffin-embedded archival tissue specimens following the Agilent SureSelectXT2 target enrichment protocol and sequenced on Illumina NextSeq 500. Raw sequence data were aligned to the reference genome with Burrows-Wheeler Aligner algorithm. Somatic mutations and copy number alterations (CNAs) were identified using MuTect2 and EXCAVATOR2, respectively. Biological functions associated with altered genes were investigated through Ingenuity Pathway Analysis (IPA) software. RESULTS: A total of 137 unique somatic mutations were identified: 133 mutated genes were case-specific, and 2 were mutated in two cases but in different positions. Among the 135 mutated genes, 27% were related to two biological categories: DNA damage-response (DDR) network that was also identified through IPA and mesenchymal-epithelial reverse transition (MErT)/epithelial-mesenchymal transition (EMT) already demonstrated to be relevant in DSRCT. The mutated genes in the DDR network were involved in various steps of transcription and particularly affected pre-mRNA. Half of these genes encoded RNA-binding proteins or DNA/RNA-binding proteins, which were recently recognized as a new class of DDR players. CNAs in genes/gene families, involved in MErT/EMT and DDR, were recurrent across patients and mostly segregated in the MErT/EMT category. In addition, recurrent gains of regions in chromosome 1 involving many MErT/EMT gene families and loss of one arm or the entire chromosome 6 affecting relevant immune-regulatory genes were recorded. CONCLUSIONS: The emerging picture is an extreme inter-tumor heterogeneity, characterized by the concurrent deregulation of the DDR and MErT/EMT dynamic and plastic programs that could favour genomic instability and explain the refractory DSRCT profile.

Whole exome sequencing and single nucleotide polymorphism array analyses to identify germline alterations in genes associated with testosterone metabolism in a patient with androgen insensitivity syndrome and early-onset colorectal cancer.

BACKGROUND: Androgen insensitivity syndrome (AIS), a disorder of sexual development in 46, XY individuals, is caused by loss-of-function mutations in the androgen receptor (AR) gene. A variety of tumors have been reported in association with AIS, but no cases with colorectal cancer (CRC) have been described. CASE PRESENTATION: Here, we present a male patient with AIS who developed multiple early-onset CRCs and his pedigree. His first cousin was diagnosed with AIS and harbored the same AR gene mutation, but with no signs of CRC. The difference in clinical management for the two patients was that testosterone treatment was given to the proband for a much longer time compared with the cousin. The CRC family history was negative, and no germline mutations in well-known CRC-related genes were identified. A single nucleotide polymorphism array revealed a microduplication on chromosome 22q11.22 that encompassed a microRNA potentially related to CRC pathogenesis. In the proband, whole exome sequencing identified a polymorphism in an oncogene and 13 rare loss-of-function variants, of which two were in CRC-related genes and four were in genes associated with other human cancers. CONCLUSIONS: By pathway analysis, all inherited germline genetic events were connected in a unique network whose alteration in the proband, together with continuous testosterone stimulation, may have played a role in CRC pathogenesis.