RESUMO
Mesenchymal hamartoma of the liver (MHL) is a benign tumor affecting children that is characterized by a primitive myxoid stroma with cystically dilated bile ducts. Alterations involving chromosome 19q13 are a recurrent underlying cause of MHL; these alterations activate the chromosome 19 microRNA cluster (C19MC). Other cases remain unexplained. We describe two children with MHLs that harbored germline DICER1 pathogenic variants. Analysis of tumor tissue from one of the children revealed two DICER1 "hits." Mutations in DICER1 dysregulate microRNAs, mimicking the effect of the activation of C19MC. Our data suggest that MHL is a new phenotype of DICER1 syndrome. (Funded by the Canadian Institutes of Health Research and others.).
Assuntos
Cromossomos Humanos Par 19 , RNA Helicases DEAD-box/genética , Mutação em Linhagem Germinativa , Hamartoma/genética , Hepatopatias/genética , MicroRNAs/metabolismo , Síndromes Neoplásicas Hereditárias/genética , Ribonuclease III/genética , Pré-Escolar , Feminino , Predisposição Genética para Doença , Hamartoma/diagnóstico por imagem , Hamartoma/patologia , Humanos , Fígado/diagnóstico por imagem , Fígado/patologia , Hepatopatias/diagnóstico por imagem , Hepatopatias/patologia , Masculino , Mesoderma , Linhagem , FenótipoRESUMO
A variety of unusual tumors are associated with both germline and somatic DICER1 pathogenic variants (PVs), including, in the female genital tract, embryonal rhabdomyosarcoma at various sites and ovarian Sertoli-Leydig cell tumor. There have been occasional reported cases of ovarian germ cell tumors [mainly yolk sac tumor (YST)] harboring DICER1 PVs but, as far as we are aware, none of these has been proven to have a germline provenance. We report an unusual enteric variant of ovarian YST in a 28-yr-old woman associated with a germline PV c.901C>T (p.Gln301Ter) in exon 7 of DICER1, accompanied by a somatic (YST-only) hotspot mutation: c.5437G>A, p.E1813K. To our knowledge, this is the first report of an ovarian germ cell tumor associated with a germline DICER1 PV. We review other reported cases of ovarian germ cell tumor with DICER1 PVs and discuss the differential diagnosis of this unusual variant of YST which was originally diagnosed as a mucinous adenocarcinoma.
Assuntos
Tumor do Seio Endodérmico , Neoplasias Embrionárias de Células Germinativas , Neoplasias Ovarianas , Tumor de Células de Sertoli-Leydig , RNA Helicases DEAD-box/genética , Tumor do Seio Endodérmico/diagnóstico , Tumor do Seio Endodérmico/genética , Feminino , Mutação em Linhagem Germinativa , Humanos , Masculino , Neoplasias Embrionárias de Células Germinativas/genética , Neoplasias Ovarianas/genética , Neoplasias Ovarianas/patologia , Ribonuclease III/genética , Tumor de Células de Sertoli-Leydig/diagnóstico , Tumor de Células de Sertoli-Leydig/genética , Tumor de Células de Sertoli-Leydig/patologiaRESUMO
Germ-line interstitial deletions involving the 14q32 chromosomal region, resulting in 14q32 deletion syndrome, are rare. DICER1 is a recently described cancer-predisposition gene located at 14q32.13. We report the case of a male child with a â¼5.8 Mbp 14q32.13q32.2 germ-line deletion, which included the full DICER1 locus. We reviewed available clinical and pathological material, and conducted genetic analyses. In addition to having congenital dysmorphic features, the child developed multiple DICER1 syndrome-related tumors before age 5 y: a pediatric cystic nephroma (pCN), a ciliary body medulloepithelioma (CBME), and a small lung cyst (consistent with occult pleuropulmonary blastoma Type I/Ir cysts seen in DICER1 mutation carriers). He also developed a cerebral spindle-cell sarcoma with myogenous differentiation. Our investigations revealed that the deletion encompassed 31 protein-coding genes. In addition to the germ-line DICER1 deletion, somatic DICER1 RNase IIIb mutations were found in the CBME (c.5437G > A, p.E1813K), pCN (c.5425G > A, p.G1809R), and sarcoma (c.5125G > A, p.D1709N). The sarcoma also harbored a somatic TP53 mutation: c.844C > T, p.R282W. Additional copy number alterations were identified in the CBME and sarcoma using an OncoScan array. Among the 8 cases with molecularly-defined 14q32 deletions involving DICER1 and for whom phenotypic information is available, our patient and one other developed DICER1-related tumors. Biallelic DICER1 mutations have not previously been reported to cause cerebral sarcoma, which now may be considered a rare manifestation of the DICER1 syndrome. Our study shows that DICER1-related tumors can occur in children with 14q32 deletions and suggests surveillance for such tumors may be warranted.
Assuntos
Deleção Cromossômica , RNA Helicases DEAD-box/genética , Síndromes Neoplásicas Hereditárias/genética , Ribonuclease III/genética , Criança , Cromossomos Humanos Par 14 , Mutação em Linhagem Germinativa , Humanos , Masculino , Deleção de SequênciaRESUMO
DICER1 syndrome is an inherited disorder associated with at least a dozen rare, mainly pediatric-onset tumors. Its characterization remains incomplete. Some studies suggested that neuroblastoma (NB) may be involved in this syndrome. Here, we describe the case of a 14-year-old female presenting with a multinodular goiter (MNG) and a collision tumor composed of NB and cystic nephroma (CN). She is a carrier of a deleterious germline mutation in exon 23 of DICER1 and harbored different somatic mutations in the CN and MNG. However, no second hit was found in the NB, questioning its status as a DICER1-related tumor.
Assuntos
RNA Helicases DEAD-box/genética , Éxons , Mutação em Linhagem Germinativa , Bócio Nodular/genética , Síndromes Neoplásicas Hereditárias/genética , Neuroblastoma/genética , Ribonuclease III/genética , Adolescente , Feminino , Bócio Nodular/enzimologia , Humanos , Síndromes Neoplásicas Hereditárias/enzimologia , Neuroblastoma/enzimologiaRESUMO
BACKGROUND: Somatic mosaicism is being increasingly recognised as an important cause of non-Mendelian presentations of hereditary syndromes. A previous whole-exome sequencing study using DNA derived from peripheral blood identified mosaic mutations in DICER1 in two children with overgrowth and developmental delay as well as more typical phenotypes of germline DICER1 mutation. However, very-low-frequency mosaicism is difficult to detect, and thus, causal mutations can go unnoticed. Highly sensitive, cost-effective approaches are needed to molecularly diagnose these persons. We studied four children with multiple primary tumours known to be associated with the DICER1 syndrome, but in whom germline DICER1 mutations were not detected by conventional mutation detection techniques. METHODS AND RESULTS: We observed the same missense mutation within the DICER1 RNase IIIb domain in multiple tumours from different sites in each patient, raising suspicion of somatic mosaicism. We implemented three different targeted-capture technologies, including the novel HaloPlex(HS) (Agilent Technologies), followed by deep sequencing, and confirmed that the identified mutations are mosaic in origin in three patients, detectable in 0.24-31% of sequencing reads in constitutional DNA. The mosaic origin of patient 4's mutation remains to be unequivocally established. We also discovered likely pathogenic second somatic mutations or loss of heterozygosity (LOH) in tumours from all four patients. CONCLUSIONS: Mosaic DICER1 mutations are an important cause of the DICER1 syndrome in patients with severe phenotypes and often appear to be accompanied by second somatic truncating mutations or LOH in the associated tumours. Furthermore, the molecular barcode-containing HaloPlex(HS) provides the sensitivity required for detection of such low-level mosaic mutations and could have general applicability.
Assuntos
RNA Helicases DEAD-box/genética , Estudos de Associação Genética , Sequenciamento de Nucleotídeos em Larga Escala/métodos , Mosaicismo , Mutação , Neoplasias Primárias Múltiplas/genética , Ribonuclease III/genética , Criança , Pré-Escolar , Biologia Computacional/métodos , Análise Mutacional de DNA , Feminino , Sequenciamento de Nucleotídeos em Larga Escala/normas , Humanos , Perda de Heterozigosidade , Masculino , Neoplasias Primárias Múltiplas/diagnóstico , Fenótipo , Sensibilidade e Especificidade , SíndromeAssuntos
Anaplasia/patologia , RNA Helicases DEAD-box/genética , Neoplasias Renais/patologia , Mutação , Síndromes Neoplásicas Hereditárias/patologia , Neuroblastoma/patologia , Ribonuclease III/genética , Sarcoma/patologia , Anaplasia/complicações , Anaplasia/genética , Criança , Humanos , Neoplasias Renais/complicações , Neoplasias Renais/genética , Masculino , Síndromes Neoplásicas Hereditárias/complicações , Síndromes Neoplásicas Hereditárias/genética , Neuroblastoma/complicações , Neuroblastoma/genética , Prognóstico , Sarcoma/complicações , Sarcoma/genéticaAssuntos
RNA Helicases DEAD-box/genética , Deleção de Genes , Síndromes Neoplásicas Hereditárias/diagnóstico , Síndromes Neoplásicas Hereditárias/genética , Ribonuclease III/genética , Adolescente , Alelos , Cromossomos Humanos Par 14 , Hibridização Genômica Comparativa , Feminino , Mutação em Linhagem Germinativa , Heterozigoto , Humanos , Imageamento por Ressonância Magnética , Linhagem , FenótipoRESUMO
Germ-line RB-1 mutations predispose to pineoblastoma (PinB), but other predisposing genetic factors are not well established. We recently identified a germ-line DICER1 mutation in a child with a PinB. This was accompanied by loss of heterozygosity (LOH) of the wild-type allele within the tumour. We set out to establish the prevalence of DICER1 mutations in an opportunistically ascertained series of PinBs. Twenty-one PinB cases were studied: Eighteen cases had not undergone previous testing for DICER1 mutations; three patients were known carriers of germ-line DICER1 mutations. The eighteen PinBs were sequenced by Sanger and/or Fluidigm-based next-generation sequencing to identify DICER1 mutations in blood gDNA and/or tumour gDNA. Testing for somatic DICER1 mutations was also conducted on one case with a known germ-line DICER1 mutation. From the eighteen PinBs, we identified four deleterious DICER1 mutations, three of which were germ line in origin, and one for which a germ line versus somatic origin could not be determined; in all four, the second allele was also inactivated leading to complete loss of DICER1 protein. No somatic DICER1 RNase IIIb mutations were identified. One PinB arising in a germ-line DICER1 mutation carrier was found to have LOH. This study suggests that germ-line DICER1 mutations make a clinically significant contribution to PinB, establishing DICER1 as an important susceptibility gene for PinB and demonstrates PinB to be a manifestation of a germ-line DICER1 mutation. The means by which the second allele is inactivated may differ from other DICER1-related tumours.
Assuntos
Neoplasias Encefálicas/genética , RNA Helicases DEAD-box/genética , Mutação em Linhagem Germinativa/genética , Glândula Pineal/patologia , Pinealoma/genética , Ribonuclease III/genética , Adolescente , Criança , Pré-Escolar , Análise Mutacional de DNA , Saúde da Família , Feminino , Humanos , Lactente , Masculino , Adulto JovemRESUMO
Individuals harboring germ-line DICER1 mutations are predisposed to a rare cancer syndrome, the DICER1 Syndrome or pleuropulmonary blastoma-familial tumor and dysplasia syndrome [online Mendelian inheritance in man (OMIM) #601200]. In addition, specific somatic mutations in the DICER1 RNase III catalytic domain have been identified in several DICER1-associated tumor types. Pituitary blastoma (PitB) was identified as a distinct entity in 2008, and is a very rare, potentially lethal early childhood tumor of the pituitary gland. Since the discovery by our team of an inherited mutation in DICER1 in a child with PitB in 2011, we have identified 12 additional PitB cases. We aimed to determine the contribution of germ-line and somatic DICER1 mutations to PitB. We hypothesized that PitB is a pathognomonic feature of a germ-line DICER1 mutation and that each PitB will harbor a second somatic mutation in DICER1. Lymphocyte or saliva DNA samples ascertained from ten infants with PitB were screened and nine were found to harbor a heterozygous germ-line DICER1 mutation. We identified additional DICER1 mutations in nine of ten tested PitB tumor samples, eight of which were confirmed to be somatic in origin. Seven of these mutations occurred within the RNase IIIb catalytic domain, a domain essential to the generation of 5p miRNAs from the 5' arm of miRNA-precursors. Germ-line DICER1 mutations are a major contributor to PitB. Second somatic DICER1 "hits" occurring within the RNase IIIb domain also appear to be critical in PitB pathogenesis.
Assuntos
RNA Helicases DEAD-box/genética , Mutação , Neoplasias Complexas Mistas/genética , Neoplasias Complexas Mistas/patologia , Neoplasias Hipofisárias/genética , Neoplasias Hipofisárias/patologia , Ribonuclease III/genética , Pré-Escolar , Análise Mutacional de DNA , Evolução Fatal , Mutação em Linhagem Germinativa , Humanos , Imuno-Histoquímica , Lactente , Imageamento por Ressonância Magnética , Neoplasias Complexas Mistas/cirurgia , Linhagem , Neoplasias Hipofisárias/cirurgia , Radiografia Torácica , Tomografia Computadorizada por Raios X , Resultado do TratamentoRESUMO
BACKGROUND: PALB2 has emerged as a breast cancer susceptibility gene. Mutations in PALB2 have been identified in almost all breast cancer populations studied to date, but the rarity of these mutations and lack of information regarding their penetrance makes genetic counseling for these families challenging. We studied BRCA1/2 -negative breast and/or ovarian cancer families to a) assess the contribution of PALB2 mutations in this series and b) identify clinical, pathological and family history characteristics that might make PALB2 screening more efficient. METHODS: The coding region of the PALB2 gene was analyzed in 175 probands with family histories of breast and/or ovarian cancer ascertained from a single Canadian institution in Eastern Ontario. RESULTS: We identified 2 probands with PALB2 mutations that are known or strongly considered to be pathogenic and 3 probands with missense mutations that are possibly pathogenic. One of the identified truncating mutations [c.3113G > A (p.Gly1000_Trp1038del - major product)], has been previously described while the other four mutations [c.3507_3508delTC (p.H1170Ffs*19), c.1846G > C (p.D616H), c.3418 T > G (p.W1140G), c.3287A > G (p.N1096S)] have not been previously reported. Loss of heterozygosity was detected in two breast tumors from one c.3507_3508delTC mutation carrier but not in other available tumors from that family or in tumors from carriers of other mutations. CONCLUSIONS: PALB2 mutation screening identifies a small, but significant number of mutations in BRCA1/2 -negative breast and/or ovarian cancer families. We show that mutations are more likely to be found in families with three or more breast cancers as well as other BRCA2-related cancers. In our cohort, both clearly pathogenic mutations were identified in premenopausal breast cancer cases (2/77, 2.6%). Testing should be preferentially offered to affected women from such families.
RESUMO
PALB2/FANCN is a BRCA1- and BRCA2-interacting Fanconi Anemia (FA) protein crucial for key BRCA2 genome caretaker functions. Heterozygous germline mutations in PALB2 predispose to breast cancer and biallelic mutations cause FA. FA proteins play a critical role in the telomere maintenance pathway, with telomeric shortening observed in FA cells. Less is known about telomere maintenance in the heterozygous state. Here, we investigate the roles of PALB2 heterozygous mutations in genomic instability, an important carcinogenesis precursor. Patient-derived lymphoblastoid (LCL) and fibroblast (FCL) cell lines with monoallelic truncating PALB2 mutations were investigated using a combination of molecular imaging techniques including centromeric FISH, telomeric Q-FISH and spectral karyotyping (SKY). Mitomycin C and Cisplatin sensitivity was assayed via cellular metabolism of WST-1. The PALB2 c.229delT FCL showed increases in telomere counts associated with increased mean intensity compared with two wild-type FCLs generated from first-degree relatives (P =1.04E-10 and P =9.68E-15) and it showed evidence of chromosomal rearrangements. Significant differences in centromere distribution were observed in one of three PALB2 heterozygous FCLs analyzed when compared with PALB2 wild-type, BRCA1 and BRCA2 heterozygous FCLs. No significant consistently increased sensitivity to Mitomycin C or Cisplatin was observed in LCLs. Our results are suggestive of an altered centromere distribution profile and a telomere instability phenotype. Together, these may indicate critical nuclear organization defects associated with the predisposition to transformation and early stage development of PALB2-related cancers.
Assuntos
Neoplasias da Mama/genética , Carcinoma Ductal de Mama/genética , Carcinoma Intraductal não Infiltrante/genética , Núcleo Celular/metabolismo , Síndrome Hereditária de Câncer de Mama e Ovário/genética , Proteínas Nucleares/genética , Proteínas Supressoras de Tumor/genética , Adolescente , Adulto , Antineoplásicos/farmacologia , Neoplasias da Mama/patologia , Carcinoma Ductal de Mama/patologia , Carcinoma Intraductal não Infiltrante/patologia , Estudos de Casos e Controles , Sobrevivência Celular/efeitos dos fármacos , Centrômero/metabolismo , Cisplatino/farmacologia , Proteína do Grupo de Complementação N da Anemia de Fanconi , Feminino , Estudos de Associação Genética , Predisposição Genética para Doença , Síndrome Hereditária de Câncer de Mama e Ovário/patologia , Heterozigoto , Humanos , Cariótipo , Masculino , Pessoa de Meia-Idade , Mitomicina/farmacologia , Telômero/metabolismo , Células Tumorais CultivadasRESUMO
Lynch syndrome is an autosomal dominant disorder that usually results from a pathogenic germline variant in one of four genes (MSH2, MSH6, MLH1, PMS2) involved in DNA mismatch repair. Carriers of such variants are at risk of developing numerous cancers during adulthood. Here we report on a family suspected of having Lynch syndrome due to a history of endometrial adenocarcinoma, ovarian clear cell carcinoma, and adenocarcinoma of the duodenum in whom we identified a germline 29 nucleotide in-frame inversion in exon 3 of MSH2. We further show that this variant is almost completely absent at the protein level, and that the associated cancers have complete loss of MSH2 and MSH6 expression by immunohistochemistry. Functional investigation of this inversion in a laboratory setting revealed a resultant abnormal protein function. Thus, we have identified an unusual, small germline inversion in a mismatch repair gene that does not lead to a premature stop codon yet appears likely to be causal for the observed cancers.
Assuntos
Adenocarcinoma , Neoplasias Colorretais Hereditárias sem Polipose , Humanos , Adulto , Neoplasias Colorretais Hereditárias sem Polipose/patologia , Proteína 2 Homóloga a MutS/genética , Proteína 2 Homóloga a MutS/metabolismo , Mutação em Linhagem Germinativa , Adenocarcinoma/genética , Éxons , Reparo de Erro de Pareamento de DNA/genética , Proteína 1 Homóloga a MutL/genética , Endonuclease PMS2 de Reparo de Erro de Pareamento/genética , Endonuclease PMS2 de Reparo de Erro de Pareamento/metabolismoRESUMO
DICER1 tumor predisposition syndrome is a pleiotropic disorder that gives rise to various mainly pediatric-onset lesions. We report an extraskeletal chondroma (EC) of the great toe occurring in a child who, unusually, carries a germline "hotspot" missense DICER1 variant rather than the more usual loss-of-function (LOF) variant. No heterozygous LOF allele was identified in the EC. We demonstrate this variant impairs 5p cleavage of precursor-miRNA (pre-miRNA) and competes with wild-type (WT) DICER1 protein for pre-miRNA processing. These results suggest a mechanism through which a germline RNase IIIb variant could impair pre-miRNA processing without complete LOF of the WT DICER1 allele.
Assuntos
Condroma , RNA Helicases DEAD-box , Predisposição Genética para Doença , Ribonuclease III , Humanos , Ribonuclease III/genética , RNA Helicases DEAD-box/genética , Condroma/genética , Condroma/patologia , Criança , Masculino , Mutação em Linhagem Germinativa , Feminino , Dedos do Pé/patologiaRESUMO
OBJECTIVE: Pulmonary blastoma is a rare, biphasic, adult-onset lung tumor. In this study, we investigate whether DICER1 pathogenic variants are a feature of pulmonary blastomas through in-depth analysis of the molecular events defining them. METHODS: We performed exome-wide sequencing and DNA methylation profiling of 8 pulmonary blastomas from 6 affected persons. RESULTS: We identified biallelic somatic DICER1 pathogenic variants in 7 of 8 cases. The remaining case had a solitary missense pathogenic variant in the RNase IIIb domain of DICER1. Six of 8 cases carried a CTNNB1 hotspot variant and 4 of 8 had a somatic pathogenic variant in TP53. Methylation analysis showed that the pulmonary blastomas clustered with other DICER1-mutated tumors and not with other more common types of lung cancer. CONCLUSION: We conclude somatic DICER1 pathogenic variants are the major driver of pulmonary blastoma and are likely to act in conjunction with CTNNB1 hotspot variants that are often present.
RESUMO
SLX4/FANCP is a recently discovered novel disease gene for Fanconi anemia (FA), a rare recessive disorder characterized by chromosomal instability and increased cancer susceptibility. Three of the 15 FA genes are breast cancer susceptibility genes in heterozygous mutation carriers--BRCA2, PALB2, and BRIP1. To investigate if defects in SLX4 also predispose to breast cancer, the gene was sequenced in a cohort of 729 BRCA1/BRCA2-negative familial breast cancer cases. We identified a single splice site mutation (c.2013+2T>A), which causes a frameshift by skipping of exon 8. We also identified 39 missense variants, four of which were selected for functional testing in a Mitomycin C-induced growth inhibition assay, and appeared indistinguishable from wild type. Although this is the first study that describes a truncating SLX4 mutation in breast cancer patients, our data indicate that germline mutations in SLX4 are very rare and are unlikely to make a significant contribution to familial breast cancer.
Assuntos
Neoplasias da Mama Masculina/genética , Neoplasias da Mama/genética , Mutação , Recombinases/genética , Adulto , Idoso , Idoso de 80 Anos ou mais , Estudos de Coortes , Análise Mutacional de DNA , Saúde da Família , Anemia de Fanconi/genética , Feminino , Predisposição Genética para Doença/genética , Humanos , Masculino , Pessoa de Meia-Idade , Mutação de Sentido Incorreto , Sítios de Splice de RNA/genéticaRESUMO
BACKGROUND: The PALB2 c.2323C>T [p.Q775X] mutation has been reported in at least three breast cancer families and breast cancer cases of French Canadian descent and this has been attributed to common ancestors. The number of mutation-positive cases reported varied based on criteria of ascertainment of index cases tested. Although inherited PALB2 mutations are associated with increased risks of developing breast cancer, risk to ovarian cancer has not been fully explored in this demographically unique population. METHODS: We screened the PALB2 p.Q775X variant in 71 families with at least three cases of breast cancer (n=48) or breast and ovarian cancers (n=23) that have previously been found negative for at least the most common BRCA1 and BRCA2 mutations reported in the French Canadian population and in 491 women of French Canadian descent who had invasive ovarian cancer and/or low malignant potential tumors of the major histopathological subtypes. RESULTS: We identified a PALB2 p.Q775X carrier in a breast cancer family, who had invasive ductal breast carcinomas at 39 and 42 years of age. We also identified a PALB2 p.Q775X carrier who had papillary serous ovarian cystadenocarcinoma at age 58 among the 238 serous subtype ovarian cancer cases investigated, who also had breast cancer at age 52. CONCLUSION: Our findings, taken together with previous reports, support adding PALB2 c.2323C>T p.Q775X to the list of cancer susceptibility genes for which founder mutations have been identified in the French Canadian population.
Assuntos
Neoplasias da Mama/genética , Efeito Fundador , Mutação em Linhagem Germinativa , Proteínas Nucleares/genética , Neoplasias Ovarianas/genética , Proteínas Supressoras de Tumor/genética , População Branca/genética , Adulto , Idoso , Sequência de Bases , Canadá/etnologia , Família , Proteína do Grupo de Complementação N da Anemia de Fanconi , Feminino , Genes BRCA1 , Genes BRCA2 , Predisposição Genética para Doença , Heterozigoto , Humanos , Pessoa de Meia-Idade , LinhagemRESUMO
The endoribonuclease DICER1 plays an essential role in the microRNA (miRNA) biogenesis pathway, cleaving precursor miRNA (pre-miRNA) stem-loops to generate mature single-stranded miRNAs. Germline pathogenic variants (GPVs) in DICER1 result in DICER1 tumor predisposition syndrome (DTPS), a mainly childhood-onset tumor susceptibility disorder. Most DTPS-causing GPVs are nonsense or frameshifting, with tumor development requiring a second somatic missense hit that impairs the DICER1 RNase IIIb domain. Interestingly, germline DICER1 missense variants that cluster in the DICER1 Platform domain have been identified in some persons affected by tumors that also associate with DTPS. Here, we demonstrate that four of these Platform domain variants prevent DICER1 from producing mature miRNAs and as a result impair miRNA-mediated gene silencing. Importantly, we show that in contrast to canonical somatic missense variants that alter DICER1 cleavage activity, DICER1 proteins harboring these Platform variants fail to bind to pre-miRNA stem-loops. Taken together, this work sheds light upon a unique subset of GPVs causing DTPS and provides new insights into how alterations in the DICER1 Platform domain can impact miRNA biogenesis.
RESUMO
DICER1 syndrome is an inherited condition associated with an increased risk of developing hamartomatous and neoplastic lesions in diverse organs, mainly at early ages. Germline pathogenic variants in DICER1 cause this condition. Detecting a variant of uncertain significance in DICER1 or finding uncommon phenotypes complicate the diagnosis and can negatively impact patient care. We present two unrelated patients suspected to have DICER1 syndrome. Both females (aged 13 and 15 years) presented with multinodular goiter (thyroid follicular nodular disease) and ovarian tumours. One was diagnosed with an ovarian Sertoli-Leydig cell tumour (SLCT) and the other, with an ovarian juvenile granulosa cell tumour, later reclassified as a retiform variant of SLCT. Genetic screening showed no germline pathogenic variants in DICER1. However, two potentially splicing variants were found, DICER1 c.5365-4A>G and c.5527+3A>G. Also, typical somatic DICER1 RNase IIIb hotspot mutations were detected in the thyroid and ovarian tissues. In silico splicing algorithms predicted altered splicing for both germline variants and skipping of exon 25 was confirmed by RNA assays for both variants. The reclassification of the ovarian tumour, leading to recognition of the association with DICER1 syndrome and the characterization of the germline intronic variants were all applied to recently described DICER1 variant classification rules. This ultimately resulted in confirmation of DICER1 syndrome in the two teenage girls.
Assuntos
Síndromes Neoplásicas Hereditárias , Neoplasias Ovarianas , Tumor de Células de Sertoli-Leydig , Masculino , Feminino , Adolescente , Humanos , Tumor de Células de Sertoli-Leydig/diagnóstico , Tumor de Células de Sertoli-Leydig/genética , Tumor de Células de Sertoli-Leydig/patologia , Mutação em Linhagem Germinativa , Neoplasias Ovarianas/diagnóstico , Neoplasias Ovarianas/genética , Neoplasias Ovarianas/patologia , Glândula Tireoide/patologia , Ribonuclease III/genética , Células Germinativas/patologia , Mutação , RNA Helicases DEAD-box/genéticaRESUMO
Germline mutations in the PALB2 gene are associated with an increased risk of developing breast cancer but little is known about the frequencies of rare variants in PALB2 and the nature of the variants that influence risk. We selected participants recruited to the Women's Environment, Cancer, and Radiation Epidemiology (WECARE) Study and screened lymphocyte DNA from cases with contralateral breast cancer (n = 559) and matched controls with unilateral breast cancer (n = 565) for PALB2 mutations. Five pathogenic PALB2 mutations were identified among the cases (0.9%) versus none among the controls (P = 0.04). The first-degree female relatives of these five carriers demonstrated significantly higher incidence of breast cancer than relatives of noncarrier cases, indicating that pathogenic PALB2 mutations confer an estimated 5.3-fold increase in risk (95% CI: 1.8-13.2). The frequency of rare (<1% MAF) missense mutations was similar in both groups (23 vs. 21). Our findings confirm in a population-based study setting of women with breast cancer the strong risk associated with truncating mutations in PALB2 that has been reported in family studies. Conversely, there is no evidence from this study that rare PALB2 missense mutations strongly influence breast cancer risk.