Extrachromosomal DNA in the cancerous transformation of Barrett's oesophagus.

Oncogene amplification on extrachromosomal DNA (ecDNA) drives the evolution of tumours and their resistance to treatment, and is associated with poor outcomes for patients with cancer1-6. At present, it is unclear whether ecDNA is a later manifestation of genomic instability, or whether it can be an early event in the transition from dysplasia to cancer. Here, to better understand the development of ecDNA, we analysed whole-genome sequencing (WGS) data from patients with oesophageal adenocarcinoma (EAC) or Barrett's oesophagus. These data included 206 biopsies in Barrett's oesophagus surveillance and EAC cohorts from Cambridge University. We also analysed WGS and histology data from biopsies that were collected across multiple regions at 2 time points from 80 patients in a case-control study at the Fred Hutchinson Cancer Center. In the Cambridge cohorts, the frequency of ecDNA increased between Barrett's-oesophagus-associated early-stage (24%) and late-stage (43%) EAC, suggesting that ecDNA is formed during cancer progression. In the cohort from the Fred Hutchinson Cancer Center, 33% of patients who developed EAC had at least one oesophageal biopsy with ecDNA before or at the diagnosis of EAC. In biopsies that were collected before cancer diagnosis, higher levels of ecDNA were present in samples from patients who later developed EAC than in samples from those who did not. We found that ecDNAs contained diverse collections of oncogenes and immunomodulatory genes. Furthermore, ecDNAs showed increases in copy number and structural complexity at more advanced stages of disease. Our findings show that ecDNA can develop early in the transition from high-grade dysplasia to cancer, and that ecDNAs progressively form and evolve under positive selection.

Functional analysis of germline VANGL2 variants using rescue assays of vangl2 knockout zebrafish.

Developmental studies have shown that the evolutionarily conserved Wnt Planar Cell Polarity (PCP) pathway is essential for the development of a diverse range of tissues and organs including the brain, spinal cord, heart and sensory organs, as well as establishment of the left-right body axis. Germline mutations in the highly conserved PCP gene VANGL2 in humans have only been associated with central nervous system malformations, and functional testing to understand variant impact has not been performed. Here we report three new families with missense variants in VANGL2 associated with heterotaxy and congenital heart disease p.(Arg169His), non-syndromic hearing loss p.(Glu465Ala) and congenital heart disease with brain defects p.(Arg135Trp). To test the in vivo impact of these and previously described variants, we have established clinically-relevant assays using mRNA rescue of the vangl2 mutant zebrafish. We show that all variants disrupt Vangl2 function, although to different extents and depending on the developmental process. We also begin to identify that different VANGL2 missense variants may be haploinsufficient and discuss evidence in support of pathogenicity. Together, this study demonstrates that zebrafish present a suitable pipeline to investigate variants of unknown significance and suggests new avenues for investigation of the different developmental contexts of VANGL2 function that are clinically meaningful.

The repertoire of mutational signatures in human cancer.

Somatic mutations in cancer genomes are caused by multiple mutational processes, each of which generates a characteristic mutational signature1. Here, as part of the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium2 of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA), we characterized mutational signatures using 84,729,690 somatic mutations from 4,645 whole-genome and 19,184 exome sequences that encompass most types of cancer. We identified 49 single-base-substitution, 11 doublet-base-substitution, 4 clustered-base-substitution and 17 small insertion-and-deletion signatures. The substantial size of our dataset, compared with previous analyses3-15, enabled the discovery of new signatures, the separation of overlapping signatures and the decomposition of signatures into components that may represent associated-but distinct-DNA damage, repair and/or replication mechanisms. By estimating the contribution of each signature to the mutational catalogues of individual cancer genomes, we revealed associations of signatures to exogenous or endogenous exposures, as well as to defective DNA-maintenance processes. However, many signatures are of unknown cause. This analysis provides a systematic perspective on the repertoire of mutational processes that contribute to the development of human cancer.

Understanding the malignant potential of gastric metaplasia of the oesophagus and its relevance to Barrett's oesophagus surveillance: individual-level data analysis.

OBJECTIVE: Whether gastric metaplasia (GM) of the oesophagus should be considered as Barrett's oesophagus (BO) is controversial. Given concern intestinal metaplasia (IM) may be missed due to sampling, the UK guidelines include GM as a type of BO. Here, we investigated whether the risk of misdiagnosis and the malignant potential of GM warrant its place in the UK surveillance. DESIGN: We performed a thorough pathology and endoscopy review to follow clinical outcomes in a novel UK cohort of 244 patients, covering 1854 person years of follow-up. We complemented this with a comparative genomic analysis of 160 GM and IM specimens, focused on early molecular hallmarks of BO and oesophageal adenocarcinoma (OAC). RESULTS: We found that 58 of 77 short-segment (<3 cm) GM (SS-GM) cases (75%) continued to be observed as GM-only across a median of 4.4 years of follow-up. We observed that disease progression in GM-only cases and GM+IM cases (cases with reported GM on some occasions, IM on others) was significantly lower than in the IM-only cases (Kaplan-Meier, p=0.03). Genomic analysis revealed that the mutation burden in GM is significantly lower than in IM (p<0.01). Moreover, GM does not bear the mutational hallmarks of OAC, with an absence of associated signatures and driver gene mutations. Finally, we established that GM found adjacent to OAC is evolutionarily distant from cancer. CONCLUSION: SS-GM is a distinct entity from SS-IM and the malignant potential of GM is lower than IM. It is questionable whether SS-GM warrants inclusion in BO surveillance.

Global Epidemiology and Genetics of Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is one of the leading cancers worldwide. Classically, HCC develops in genetically susceptible individuals who are exposed to risk factors, especially in the presence of liver cirrhosis. Significant temporal and geographic variations exist for HCC and its etiologies. Over time, the burden of HCC has shifted from the low-moderate to the high sociodemographic index regions, reflecting the transition from viral to nonviral causes. Geographically, the hepatitis viruses predominate as the causes of HCC in Asia and Africa. Although there are genetic conditions that confer increased risk for HCC, these diagnoses are rarely recognized outside North America and Europe. In this review, we will evaluate the epidemiologic trends and risk factors of HCC, and discuss the genetics of HCC, including monogenic diseases, single-nucleotide polymorphisms, gut microbiome, and somatic mutations.

Characterization of colibactin-associated mutational signature in an Asian oral squamous cell carcinoma and in other mucosal tumor types.

Mutational signatures can reveal the history of mutagenic processes that cells were exposed to before and during tumorigenesis. We expect that as-yet-undiscovered mutational processes will shed further light on mutagenesis leading to carcinogenesis. With this in mind, we analyzed the mutational spectra of 36 Asian oral squamous cell carcinomas. The mutational spectra of two samples from patients who presented with oral bacterial infections showed novel mutational signatures. One of these novel signatures, SBS_AnT, is characterized by a preponderance of thymine mutations, strong transcriptional strand bias, and enrichment for adenines in the 4 bp 5' of mutation sites. The mutational signature described in this manuscript was shown to be caused by colibactin, a bacterial mutagen produced by E. coli carrying the pks-island. Examination of publicly available sequencing data revealed SBS_AnT in 25 tumors from several mucosal tissue types, expanding the list of tissues in which this mutational signature is observed.

Inactivation of DRG1, encoding a translation factor GTPase, causes a recessive neurodevelopmental disorder.

PURPOSE: Developmentally regulated Guanosine-5'-triphosphate-binding protein 1 (DRG1) is a highly conserved member of a class of GTPases implicated in translation. Although the expression of mammalian DRG1 is elevated in the central nervous system during development, and its function has been implicated in fundamental cellular processes, no pathogenic germline variants have yet been identified. Here, we characterize the clinical and biochemical consequences of DRG1 variants. METHODS: We collate clinical information of 4 individuals with germline DRG1 variants and use in silico, in vitro, and cell-based studies to study the pathogenicity of these alleles. RESULTS: We identified private germline DRG1 variants, including 3 stop-gained p.Gly54∗, p.Arg140∗, p.Lys263∗, and a p.Asn248Phe missense variant. These alleles are recessively inherited in 4 affected individuals from 3 distinct families and cause a neurodevelopmental disorder with global developmental delay, primary microcephaly, short stature, and craniofacial anomalies. We show that these loss-of-function variants (1) severely disrupt DRG1 messenger RNA/protein stability in patient-derived fibroblasts, (2) impair its GTPase activity, and (3) compromise its binding to partner protein ZC3H15. Consistent with the importance of DRG1 in humans, targeted inactivation of mouse Drg1 resulted in preweaning lethality. CONCLUSION: Our work defines a new Mendelian disorder of DRG1 deficiency. This study highlights DRG1's importance for normal mammalian development and underscores the significance of translation factor GTPases in human physiology and homeostasis.

Impact of neurofibromatosis type 1 with plexiform neurofibromas on the health-related quality of life and work productivity of adult patients and caregivers in the UK: a cross-sectional survey.

BACKGROUND: Plexiform neurofibromas (PN) are complex, benign nerve-sheath tumours that occur in 30-50% of patients with neurofibromatosis type 1 (NF1), a rare, genetic disorder. PN are associated with substantial, heterogeneous morbidities that impact health-related quality of life (HRQoL), including affecting motor function and causing pain, though HRQoL and work productivity data are scarce. This UK cross-sectional study explored HRQoL and work productivity in adult patients with NF1 PN and caregivers of paediatric patients. METHODS: Adult patients and caregivers of paediatric patients self-enrolled in an online survey (March-April 2021). Outcomes included EQ-5D-5L, PROMIS® GH and INF1-QOL (adult patients only), and EQ-5D-5L, CarerQol and WPAI (caregivers only). Utilities were estimated from EQ-5D-5L responses using the UK crosswalk value set. Linear regression models explored univariable associations between adult patient characteristics and HRQoL. RESULTS: Mean (± standard deviation) EQ-5D utility in adult patients with NF1 PN was 0.65 (± 0.29; n = 35; age-/sex-matched norm: 0.89 [± 0.04]). Moderate-extreme pain/discomfort and anxiety/depression were reported by 14/35 (40.0%) and 18/35 (51.4%) patients, respectively. Mean PROMIS® GH physical and mental health scores were 43.6 (± 9.19) and 41.7 (± 11.5; n = 35; matched norm: 50.0 [± 10.0]). Mean INF1-QOL score was 11.03 (± 6.02; n = 33). Chronic itching, at least one symptom, at least one comorbidity, PN location at extremities (arms/legs) and pain were associated with worse HRQoL scores. Mean caregiver EQ-5D utility was 0.72 (± 0.24; n = 8; age-/sex-matched norm: 0.88 [± 0.03]). Moderate pain/discomfort and moderate-severe anxiety/depression were reported by 4/8 (50.0%) and 2/8 (25.0%) caregivers, respectively. Mean CarerQol score was 69.3 (± 13.9; n = 8). Mean WPAI regular activity productivity loss was 36.3% (± 31.6%; n = 8). CONCLUSIONS: NF1 PN worsens adult patient and caregiver HRQoL compared to the general population, notably affecting pain and discomfort, anxiety and depression and caregiver productivity.

Experimental and pan-cancer genome analyses reveal widespread contribution of acrylamide exposure to carcinogenesis in humans.

Humans are frequently exposed to acrylamide, a probable human carcinogen found in commonplace sources such as most heated starchy foods or tobacco smoke. Prior evidence has shown that acrylamide causes cancer in rodents, yet epidemiological studies conducted to date are limited and, thus far, have yielded inconclusive data on association of human cancers with acrylamide exposure. In this study, we experimentally identify a novel and unique mutational signature imprinted by acrylamide through the effects of its reactive metabolite glycidamide. We next show that the glycidamide mutational signature is found in a full one-third of approximately 1600 tumor genomes corresponding to 19 human tumor types from 14 organs. The highest enrichment of the glycidamide signature was observed in the cancers of the lung (88% of the interrogated tumors), liver (73%), kidney (>70%), bile duct (57%), cervix (50%), and, to a lesser extent, additional cancer types. Overall, our study reveals an unexpectedly extensive contribution of acrylamide-associated mutagenesis to human cancers.

Multicenter study on the genetics of glomerular diseases among southeast and south Asians: Deciphering Diversities - Renal Asian Genetics Network (DRAGoN).

Multinational studies have reported monogenic etiologies in 25%-30% of children with steroid-resistant nephrotic syndrome. Such large studies are lacking in Asia. We established Deciphering Diversities: Renal Asian Genetics Network (DRAGoN) and aimed to describe the genetic and clinical spectrums in Asians. We prospectively studied a cohort of 183 probands with suspected genetic glomerulopathies from South and Southeast Asia, of whom 17% had positive family history. Using multi-gene panel sequencing, we detected pathogenic variants in 26 (14%) probands, of whom one-third had COL4A4 or COL4A5 variants (n = 9, 5%). Of those with COL4A5 defects, only 25% had features suggestive of Alport syndrome. Besides traditional predictors for genetic disease (positive family history and extrarenal malformations), we identified novel predictors, namely older age (6.2 vs. 2.4 years; p = 0.001), hematuria (OR 5.6; 95% CI 2.1-14.8; p < 0.001), and proteinuria in the absence of nephrotic syndrome (OR 4.6; 95% CI 1.8-11.8; p = 0.001) at first manifestation. Among patients who first presented with proteinuria without nephrotic syndrome, the genetic diagnostic rates were >60% when a second risk factor (positive family history or extrarenal manifestation) co-existed. The genetic spectrum of glomerulopathies appears different in Asia. Collagen IV genes may be included in sequencing panels even when suggestive clinical features are absent.

Real-world evaluation of osteoporotic fractures using the Japan Medical Data Vision database.

In Japanese patients who experienced an osteoporotic fracture, 10.8% and 18.6% had a subsequent fracture within 1 and 2 years of follow-up, respectively. Although the burden of hip and vertebral fractures has been reported widely, we found that patients with non-hip non-vertebral (NHNV) fractures had a 26% higher risk of subsequent fracture than patients with hip fractures; therefore, NHNV fractures should also be considered an important risk factor for subsequent fracture. INTRODUCTION: To investigate imminent risk and odds of subsequent osteoporotic fractures and associated risk factors in patients who experienced an initial osteoporotic fracture. METHODS: Patients aged ≥ 50 years with ≥ 1 osteoporotic fracture were analyzed from Japan's Medical Data Vision (MDV) database of claims from acute-care hospitals (January 2012-January 2017). Multivariable models were constructed to explore the impact of key comorbidities and medications on the subsequent fracture risk: Cox proportional hazards model for time to subsequent fracture and logistic regression models for odds of subsequent fracture within 1 and 2 years from index fracture. RESULTS: In total, 32,926 patients were eligible with a median follow-up duration of 12.3 months. The percentage of patients experiencing subsequent fractures was 14.1% across the study duration, and 10.8% and 18.6% in patients with 1 and 2 years of follow-up, respectively. In the Cox proportional hazards model, patients with vertebral or NHNV index fractures had a higher subsequent fracture risk than patients with a hip index fracture (adjusted hazard ratio [aHR] 1.11 and 1.26, respectively); subsequent fracture risk was lower in males than females (aHR 0.89). Patients with baseline claims for tranquilizers and glucocorticoids had a higher subsequent fracture risk than those without (aHR 1.14 and 1.08, respectively). Additionally, baseline claims for anti-Parkinson's medications, alcoholism, and stage 4/5 chronic kidney disease were significantly associated with higher odds of subsequent fracture in the logistic regression models. CONCLUSION: Several clinical and demographic factors were associated with a higher risk and odds of subsequent fracture. This may help to identify patients who should be prioritized for osteoporosis treatment.

Mutations of 1p genes do not consistently abrogate tumor suppressor functions in 1p-intact neuroblastoma.

BACKGROUND: Deletion of 1p is associated with poor prognosis in neuroblastoma, however selected 1p-intact patients still experience poor outcomes. Since mutations of 1p genes may mimic the deleterious effects of chromosomal loss, we studied the incidence, spectrum and effects of mutational variants in 1p-intact neuroblastoma. METHODS: We characterized the 1p status of 325 neuroblastoma patients, and correlated the mutational status of 1p tumor suppressors and neuroblastoma candidate genes with survival outcomes among 100 1p-intact cases, then performed functional validation of selected novel variants of 1p36 genes identified from our patient cohort. RESULTS: Among patients with adverse disease characteristics, those who additionally had 1p deletion had significantly worse overall survival. Among 100 tumor-normal pairs sequenced, somatic mutations of 1p tumor suppressors KIF1Bß and CHD5 were most frequent (2%) after ALK and ATRX (8%), and BARD1 (3%). Mutations of neuroblastoma candidate genes were associated with other synchronous mutations and concurrent 11q deletion (P = 0.045). In total, 24 of 38 variants identified were novel and predicted to be deleterious or pathogenic. Functional validation identified novel KIF1Bß I1355M variant as a gain-of-function mutation with increased expression and tumor suppressive activity, correlating with indolent clinical behavior; another novel variant CHD5 E43Q was a loss-of-function mutation with decreased expression and increased long-term cell viability, corresponding with aggressive disease characteristics. CONCLUSIONS: Our study showed that chromosome 1 gene mutations occurred frequently in 1p-intact neuroblastoma, but may not consistently abrogate the function of bonafide 1p tumor suppressors. These findings may augment the evolving model of compounding contributions of 1p gene aberrations toward tumor suppressor inactivation in neuroblastoma.

Bilateral Atypical Femur Fractures After Denosumab in a Bisphosphonate Naive Patient: A Case Report.

A case report of bilateral atypical femur fractures (AFF) in a bisphosphonate naive patient. A 62-year-old female bisphosphonate naive patient was started on denosumab for osteoporosis. Approximately 3 years later she complained of right hip pain and was found to have a bilateral incomplete AFFs. She was asymptomatic on the left lower limb. Patient was managed conservatively and placed on protected weight bearing on both legs. Symptoms subsequently resolved over a period of 3 months, although radiographic findings remained at approximately 1 year. AFFs may be associated with patients on denosumab therapy even without a prior history of bisphosphonate use. Patients should be counselled appropriately and monitored for such complications.

Characteristics and Healthcare Costs in the Aging Hepatitis B Population of Japan: A Nationwide Real-World Analysis.

INTRODUCTION: Advancing age, comorbidity, and financial burden have been observed in chronic hepatitis B (CHB) patients globally. As Japan is leading the world in aging demographics, similar real-world data are urgently needed for its CHB population to inform all stakeholders. METHODS: This cross-sectional study characterized the demographics, comorbidities, and healthcare costs of a large Japanese real-world adult (≥18 years) CHB patient (ICD-10: B18.1) population from the Medical Data Vision database from January 01, 2012, to December 31, 2016. Comorbidities were identified by ICD-10 codes, and the annual point prevalence and Charlson Comorbidity Index (CCI) score were calculated. Annual mean and median all-cause healthcare utilization and costs per patient were calculated. Comparison tests were conducted for CCI scores, prevalence of comorbidities, and healthcare resource utilization and costs. RESULTS: We identified 11,125 CHB patients. Between 2012 and 2016, the mean age increased from 62.0 to 65.2 years, and the percentage of those aged ≥65 years increased from 45.6% to 60.7%. The prevalence of cirrhosis remained similar (5.8% in 2012 and 5.6% in 2016, p = 0.69) while hepatocellular carcinoma decreased from 6.3% to 4.5% (p < 0.01). The prevalence of nonliver comorbidities increased (40.9-52.0% for cancer [p < 0.01], 12.1-17.7% for osteoporosis [p < 0.01], and 10.7-15.0% for renal impairment [p < 0.01]). Healthcare resource utilization and costs also increased, with a 119.3% increase in median total healthcare costs from JPY 229,143 in 2012 to 502,467 in 2016 (p < 0.01). CONCLUSIONS: The CHB population of Japan is predominantly elderly and carry a high nonliver comorbidity burden, while incurring increasing healthcare costs.

In-depth characterization of the cisplatin mutational signature in human cell lines and in esophageal and liver tumors.

Cisplatin reacts with DNA and thereby likely generates a characteristic pattern of somatic mutations, called a mutational signature. Despite widespread use of cisplatin in cancer treatment and its role in contributing to secondary malignancies, its mutational signature has not been delineated. We hypothesize that cisplatin's mutational signature can serve as a biomarker to identify cisplatin mutagenesis in suspected secondary malignancies. Knowledge of which tissues are at risk of developing cisplatin-induced secondary malignancies could lead to guidelines for noninvasive monitoring for secondary malignancies after cisplatin chemotherapy. We performed whole genome sequencing of 10 independent clones of cisplatin-exposed MCF-10A and HepG2 cells and delineated the patterns of single and dinucleotide mutations in terms of flanking sequence, transcription strand bias, and other characteristics. We used the mSigAct signature presence test and nonnegative matrix factorization to search for cisplatin mutagenesis in hepatocellular carcinomas and esophageal adenocarcinomas. All clones showed highly consistent patterns of single and dinucleotide substitutions. The proportion of dinucleotide substitutions was high: 8.1% of single nucleotide substitutions were part of dinucleotide substitutions, presumably due to cisplatin's propensity to form intra- and interstrand crosslinks between purine bases in DNA. We identified likely cisplatin exposure in nine hepatocellular carcinomas and three esophageal adenocarcinomas. All hepatocellular carcinomas for which clinical data were available and all esophageal cancers indeed had histories of cisplatin treatment. We experimentally delineated the single and dinucleotide mutational signature of cisplatin. This signature enabled us to detect previous cisplatin exposure in human hepatocellular carcinomas and esophageal adenocarcinomas with high confidence.

Loss-of-Function Mutations in LGI4, a Secreted Ligand Involved in Schwann Cell Myelination, Are Responsible for Arthrogryposis Multiplex Congenita.

Arthrogryposis multiplex congenita (AMC) is a developmental condition characterized by multiple joint contractures resulting from reduced or absent fetal movements. Through genetic mapping of disease loci and whole-exome sequencing in four unrelated multiplex families presenting with severe AMC, we identified biallelic loss-of-function mutations in LGI4 (leucine-rich glioma-inactivated 4). LGI4 is a ligand secreted by Schwann cells that regulates peripheral nerve myelination via its cognate receptor ADAM22 expressed by neurons. Immunolabeling experiments and transmission electron microscopy of the sciatic nerve from one of the affected individuals revealed a lack of myelin. Functional tests using affected individual-derived iPSCs showed that these germline mutations caused aberrant splicing of the endogenous LGI4 transcript and in a cell-based assay impaired the secretion of truncated LGI4 protein. This is consistent with previous studies reporting arthrogryposis in Lgi4-deficient mice due to peripheral hypomyelination. This study adds to the recent reports implicating defective axoglial function as a key cause of AMC.

CDK10 Mutations in Humans and Mice Cause Severe Growth Retardation, Spine Malformations, and Developmental Delays.

In five separate families, we identified nine individuals affected by a previously unidentified syndrome characterized by growth retardation, spine malformation, facial dysmorphisms, and developmental delays. Using homozygosity mapping, array CGH, and exome sequencing, we uncovered bi-allelic loss-of-function CDK10 mutations segregating with this disease. CDK10 is a protein kinase that partners with cyclin M to phosphorylate substrates such as ETS2 and PKN2 in order to modulate cellular growth. To validate and model the pathogenicity of these CDK10 germline mutations, we generated conditional-knockout mice. Homozygous Cdk10-knockout mice died postnatally with severe growth retardation, skeletal defects, and kidney and lung abnormalities, symptoms that partly resemble the disease's effect in humans. Fibroblasts derived from affected individuals and Cdk10-knockout mouse embryonic fibroblasts (MEFs) proliferated normally; however, Cdk10-knockout MEFs developed longer cilia. Comparative transcriptomic analysis of mutant and wild-type mouse organs revealed lipid metabolic changes consistent with growth impairment and altered ciliogenesis in the absence of CDK10. Our results document the CDK10 loss-of-function phenotype and point to a function for CDK10 in transducing signals received at the primary cilia to sustain embryonic and postnatal development.

Genome-scale mutational signatures of aflatoxin in cells, mice, and human tumors.

Aflatoxin B1 (AFB1) is a mutagen and IARC (International Agency for Research on Cancer) Group 1 carcinogen that causes hepatocellular carcinoma (HCC). Here, we present the first whole-genome data on the mutational signatures of AFB1 exposure from a total of >40,000 mutations in four experimental systems: two different human cell lines, in liver tumors in wild-type mice, and in mice that carried a hepatitis B surface antigen transgene-this to model the multiplicative effects of aflatoxin exposure and hepatitis B in causing HCC. AFB1 mutational signatures from all four experimental systems were remarkably similar. We integrated the experimental mutational signatures with data from newly sequenced HCCs from Qidong County, China, a region of well-studied aflatoxin exposure. This indicated that COSMIC mutational signature 24, previously hypothesized to stem from aflatoxin exposure, indeed likely represents AFB1 exposure, possibly combined with other exposures. Among published somatic mutation data, we found evidence of AFB1 exposure in 0.7% of HCCs treated in North America, 1% of HCCs from Japan, but 16% of HCCs from Hong Kong. Thus, aflatoxin exposure apparently remains a substantial public health issue in some areas. This aspect of our study exemplifies the promise of future widespread resequencing of tumor genomes in providing new insights into the contribution of mutagenic exposures to cancer incidence.

Heterozygous missense variant in EIF6 gene: A novel form of Shwachman-Diamond syndrome?

Shwachman-Diamond syndrome (SDS) is a rare multisystem ribosomal biogenesis disorder characterized by exocrine pancreatic insufficiency, hematologic abnormalities and bony abnormalities. About 90% of patients have biallelic mutations in SBDS gene. Three additional genes-EFL1, DNAJC21 and SRP54 have been reported in association with a SDS phenotype. However, the cause remains unknown for ~10% of patients. Herein, we report a 6-year-old Chinese boy, who presented in the neonatal period with pancytopenia, liver transaminitis with hepatosplenomegaly and developmental delay, and subsequently developed pancreatic insufficiency complicated by malabsorption and poor growth. Exome sequencing identified a novel de novo heterozygous variant in EIF6 (c.182G>T, p.Arg61Leu). EIF6 protein inhibits ribosomal maturation and is removed in the late steps of ribosomal maturation by SBDS and EFL1 protein. Given the interaction of EIF6 with SBDS and EFL1, we postulate heterozygous variants in EIF6 as a novel cause of Shwachman-Diamond-like phenotype. We compared the phenotype of our patient with those in patients with mutation in SBDS, EFL1, DNAJC21, and SRP54 genes to support this association. Identification of more cases of this novel phenotype would strengthen the association with the genetic etiology.