Shuoguo Wang

Germline Mutations in Predisposition Genes in Pediatric Cancer

BACKGROUND The prevalence and spectrum of predisposing mutations among children and adolescents with cancer are largely unknown. Knowledge of such mutations may improve the understanding of tumorigenesis, direct patient care, and enable genetic counseling of patients and families. METHODS In 1120 patients younger than 20 years of age, we sequenced the whole genomes (in 595 patients), whole exomes (in 456), or both (in 69). We analyzed the DNA sequences of 565 genes, including 60 that have been associated with autosomal dominant cancer-predisposition syndromes, for the presence of germline mutations. The pathogenicity of the mutations was determined by a panel of medical experts with the use of cancer-specific and locus-specific genetic databases, the medical literature, computational predictions, and second hits identified in the tumor genome. The same approach was used to analyze data from 966 persons who did not have known cancer in the 1000 Genomes Project, and a similar approach was used to analyze data from an autism study (from 515 persons with autism and 208 persons without autism). RESULTS Mutations that were deemed to be pathogenic or probably pathogenic were identified in 95 patients with cancer (8.5%), as compared with 1.1% of the persons in the 1000 Genomes Project and 0.6% of the participants in the autism study. The most commonly mutated genes in the affected patients were TP53 (in 50 patients), APC (in 6), BRCA2 (in 6), NF1 (in 4), PMS2 (in 4), RB1 (in 3), and RUNX1 (in 3). A total of 18 additional patients had protein-truncating mutations in tumor-suppressor genes. Of the 58 patients with a predisposing mutation and available information on family history, 23 (40%) had a family history of cancer. CONCLUSIONS Germline mutations in cancer-predisposing genes were identified in 8.5% of the children and adolescents with cancer. Family history did not predict the presence of an underlying predisposition syndrome in most patients. (Funded by the American Lebanese Syrian Associated Charities and the National Cancer Institute.).

Germline genetic variation in ETV6 and risk of childhood acute lymphoblastic leukaemia: a systematic genetic study

Background Hereditary predisposition is rarely suspected for childhood acute lymphoblastic leukemia (ALL). Recent studies identified germline ETV6 variations associated with marked familial clustering of hematologic malignancies, pointing to this gene as a potentially important genetic determinant for ALL susceptibility. The aims of the current study are to comprehensively identify ALL predisposition variants in ETV6 and to determine the extent to which they contribute to the overall risk of childhood ALL. Methods Whole-exome sequencing of an index family with multiple cases of ALL was performed to identify causal variants for ALL predisposition. Targeted sequencing of ETV6 was done in 4,405 children from the Childrens Oncology Group (COG) and St. Jude Childrens Research Hospital frontline ALL trials. Patients were included in this study on the basis of their enrollment in these clinical trials and the availability of germline DNA. ETV6 variant genotypes were compared with non-ALL controls to define ALL-related germline risk variants. ETV6 variant function was characterized bioinformatically and correlated with clinical and demographic features in 2,021 children with ALL. Findings We identified a novel nonsense ETV6 variant (p.R359X) with a high penetrance of familial ALL. Subsequent targeted sequencing of ETV6 in 4,405 childhood ALL cases discovered 31 exonic variants (4 nonsense, 21 missense, 1 splice site, and 5 frame shift variants) that are potentially related to ALL risk in 35 cases (0.79%). Fifteen (48%) of the 31 ALL-related ETV6 variants clustered in the ETS domain and predicted to be highly deleterious. Children with ALL-related ETV6 variants were significantly older at leukemia diagnosis than others (10.2 years [IQR 5.3-13.8] vs 4.7 years [IQR 3.0-8.7], P=0.017). The hyperdiploid leukemia karyotype was strikingly overrepresented in ALL cases harboring germline ETV6 risk variants compared to the wildtype group (9 of 14 cases [64.3%] vs 538 of 2,007 cases [26.8%]; P=0.0050). Interpretation Our findings indicated germline ETV6 variations as the basis of a novel genetic syndrome associated with predisposition to childhood ALL. Funding This study was supported by the National Institutes of Health and by the American Lebanese Syrian Associated Charities.

Antigenic evolution of H9N2 chicken influenza viruses isolated in China during 2009-2013 and selection of a candidate vaccine strain with broad cross-reactivity.

We previously demonstrated that H9N2 subtype avian influenza viruses (AIVs) isolated from 1994 to 2008 evolved into distinct antigenic groups (C, D, and E) and then underwent antigenic drift from commercial vaccines, causing a country-wide outbreak during 2010-2013. In this study, H9N2 AIVs isolated from chickens during 2009-2013 were antigenically analyzed by performing hemagglutination inhibition and neutralization assays using a panel of polyclonal antibodies. Our findings confirmed the antigenic drift of recent H9N2 viruses from the commercial vaccine and showed that most of these antigenic variants form a novel HI antigenic group, F, with a few belonging to groups D and E. Slight antigenic variation was observed in group F viruses. Genetic analysis of amino acid sequences deduced from hemagglutinin (HA) gene sequences indicated that 9 of 15 mutations predominant in the 2009-2013 viruses can be mapped to known antigenic sites, which might be responsible for the novel antigenicity of group F. These antigenic changes make it necessary to modify the influenza vaccine to ensure efficient protection. A vaccine candidate, Ck/HeB/YT/10, was selected and provided significant protection against viruses from different antigenic groups in terms of reduction in virus shedding, suggesting broad cross-reactivity. Taken together, our results indicate that the H9N2 chicken influenza viruses in China have evolved from distinct antigenic groups into a novel group F that became dominant during the country-wide outbreak and now seems to be undergoing new antigenic divergence. Systematic surveillance and timely updating of vaccine strains are important for viral prevention and control in the future.

Comparison of genome sequencing and clinical genotyping for pharmacogenes

We compared whole exome sequencing (WES, n = 176 patients) and whole genome sequencing (WGS, n = 68) and clinical genotyping (DMET array‐based approach) for interrogating 13 genes with Clinical Pharmacogenetics Implementation Consortium (CPIC) guidelines. We focused on 127 CPIC important variants: 103 single nucleotide variations (SNV), 21 insertion/deletions (Indel), HLA‐B alleles, and two CYP2D6 structural variations. WES and WGS provided interrogation of nonoverlapping sets of 115 SNV/Indels with call rate >98%. Among 68 loci interrogated by both WES and DMET, 64 loci (94.1%, confidence interval [CI]: 85.6–98.4%) showed no discrepant genotyping calls. Among 66 loci interrogated by both WGS and DMET, 63 loci (95.5%, CI: 87.2–99.0%) showed no discrepant genotyping calls. In conclusion, even without optimization to interrogate pharmacogenetic variants, WES and WGS displayed potential to provide reliable interrogation of most pharmacogenes and further validation of genome sequencing in a clinical lab setting is warranted.

The genomic landscape of pediatric myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are uncommon in children and have a poor prognosis. In contrast to adult MDS, little is known about the genomic landscape of pediatric MDS. Here, we describe the somatic and germline changes of pediatric MDS using whole exome sequencing, targeted amplicon sequencing, and/or RNA-sequencing of 46 pediatric primary MDS patients. Our data show that, in contrast to adult MDS, Ras/MAPK pathway mutations are common in pediatric MDS (45% of primary cohort), while mutations in RNA splicing genes are rare (2% of primary cohort). Surprisingly, germline variants in SAMD9 or SAMD9L were present in 17% of primary MDS patients, and these variants were routinely lost in the tumor cells by chromosomal deletions (e.g., monosomy 7) or copy number neutral loss of heterozygosity (CN-LOH). Our data confirm that adult and pediatric MDS are separate diseases with disparate mechanisms, and that SAMD9/SAMD9L mutations represent a new class of MDS predisposition.Myelodysplastic syndromes (MDS) are uncommon in children and have poor prognosis. Here, the authors interrogate the genomic landscape of MDS, confirming adult and paediatric MDS are separate diseases with disparate mechanisms, and highlighting that SAMD9/SAMD9L mutations represent a new class of MDS predisposition.

Genetic evolution of influenza H9N2 viruses isolated from various hosts in China from 1994 to 2013

Influenza H9N2 subtype viruses and their reassortants (such as H7N9) are posing increasing threats to birds and humans in China. During 2009–2013, multiple novel subtype viruses with H9N2 original genes emerged in China. Yet, the genetic evolution of H9N2 viruses in various host organisms in China has not been systematically investigated since 2009. In the present study, we performed large-scale sequence analysis of H9N2 viral genomes from public databases, representing the spectrum of viruses isolated from birds, mammals and humans in China from 1994 to 2013, and updated the clade classification for each segment. We identified 117 distinct genotypes in 730 H9N2 viruses. We analyzed the sequences of all eight segments in each virus and found three important time points: the years 2000, 2006 and 2010. In the periods divided by these years, genotypic diversity, geographic distribution and host range changed considerably. Genotypic diversity fluctuated greatly in 2000 and 2006. Since 2010, a single genotype became predominant in poultry throughout China, and the eastern coastal region became the newly identified epidemic center. Throughout their 20-year prevalence in China, H9N2 influenza viruses have emerged and adapted from aquatic birds to chickens. The minor avian species and wild birds exacerbated H9N2 genotypes by providing diversified genes, and chickens were the most prevalent vector in which the viruses evolved and expanded their prevalence. It is the necessity for surveillance and disease control on live-bird markets, poultry farms and wild-bird habitats in China. Emerging Microbes & Infections (2017) 6, e106; doi:10.1038/emi.2017.94; published online 29 November 2017

Clonal dynamics of donor-derived myelodysplastic syndrome after unrelated hematopoietic cell transplantation for high-risk pediatric B-lymphoblastic leukemia

Donor-derived hematologic malignancies are rare complications of hematopoietic cell transplantation (HCT). Although these are commonly either a myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML), in general, they are a heterogeneous group of diseases, and a unified mechanism for their development has remained elusive. Here we report next-generation sequencing, including whole-exome sequencing (WES), whole-genome sequencing (WGS), and targeted sequencing, of a case of donor-derived MDS (dMDS) following HCT for high-risk B-lymphoblastic leukemia (B-ALL) in an adolescent. Through interrogation of single-nucleotide polymorphisms (SNPs) in the WGS data, we unequivocally prove that the MDS is donor-derived. Additionally, we sequenced 15 samples from 12 time points, including the initial B-ALL diagnostic sample through several post-HCT remission samples, the dMDS, and representative germline samples from both patient and donor, to show that the MDS-related pathologic mutations, including a canonical ASXL1 (p.Y700*) mutation, were detectable nearly 3 yr prior to the morphological detection of MDS. Furthermore, these MDS mutations were not detectable immediately following, and for >1 yr post-, HCT. These data support the clinical utility of comprehensive sequencing following HCT to detect donor-derived malignancies, while providing insights into the clonal progression of dMDS over a 4-yr period.

Structure and evolution of double minutes in diagnosis and relapse brain tumors.

Double minute chromosomes are extrachromosomal circular DNA fragments frequently found in brain tumors. To understand their evolution, we characterized the double minutes in paired diagnosis and relapse tumors from a pediatric high-grade glioma and four adult glioblastoma patients. We determined the full structures of the major double minutes using a novel approach combining multiple types of supporting genomic evidence. Among the double minutes identified in the pediatric patient, only one carrying EGFR was maintained at high abundance in both samples, whereas two others were present in only trace amounts at diagnosis but abundant at relapse, and the rest were found either in the relapse sample only or in the diagnosis sample only. For the EGFR-carrying double minutes, we found a secondary somatic deletion in all copies at relapse, after erlotinib treatment. However, the somatic mutation was present at very low frequency at diagnosis, suggesting potential resistance to the EGFR inhibitor. This mutation caused an in-frame RNA transcript to skip exon 16, a novel transcript isoform absent in EST database, as well as about 700 RNA-seq of normal brains that we reviewed. We observed similar patterns involving longitudinal copy number shift of double minutes in another four pairs (diagnosis/relapse) of adult glioblastoma. Overall, in three of five paired tumor samples, we found that although the same oncogenes were amplified at diagnosis and relapse, they were amplified on different double minutes. Our results suggest that double minutes readily evolve, increasing tumor heterogeneity rapidly. Understanding patterns of double minute evolution can shed light on future therapeutic solutions to brain tumors carrying such variants.