Germline (epi)genetics reveals high predisposition in females: a 5-year, nationwide, prospective Wilms tumour cohort

Environmental risk factors of Wilms tumour: A systematic review and meta-analysis

Wilms tumour (WT) is the fourth leading cause of cancer death in children. Elucidating modifiable risk factors is crucial in identifying venues for primary prevention of the disease. This study aimed to review literature and synthesize environmental risk factors for WT. We conducted a systematic review and meta-analysis of epidemiological studies using PubMed, Web of Science, and Embase databases. Studies were included if they were case-control or cohort studies of children under the age of 20 years at diagnosis and reported Relative Risks (RRs) with 95 % confidence intervals (CIs). Pooled effect sizes (ES) and 95 % CIs for risk factors associated with WT were estimated using random-effects models. We included 58 eligible studies from Asia, Europe, Latin and North America, and Oceania totalling approximately10000 cases of WT diagnosed between 1953 and 2019. We confirmed an association between high birthweight ((>4000 g) ES 1.54, CI 1.20-1.97) and WT. Similarly, consistent associations were suggested for Caesarean section (ES 1.23, CI 1.07-1.42), gestational age <37 weeks (ES 1.45, CI 1.21-1.74), and large-for-gestational age (ES 1.52, CI 1.09-2.12). Parental occupational exposure to pesticides during preconception / pregnancy also showed increased risks of WT (maternal ES 1.28, CI 1.02-1.60, paternal ES 1.48, CI 0.98-2.24). There were inverse associations for breastfeeding (ever breastfed = ES 0.71, CI 0.56-0.89; < 6 months ES 0.67, CI 0.49-0.91; and ≥6 months ES 0.75, CI 0.59-0.97), and maternal intake of vitamins (unspecified) and folic acid during pregnancy (ES 0.78, CI 0.69-0.89). Among factors showing no associations were low birthweight (<2500 g), small-for-gestational age, assisted reproductive technology, parental age, and smoking or alcohol consumption during preconception / pregnancy, paternal occupational extremely low frequency magnetic fields (ELF-MF) exposures, and maternal X-ray exposure during pregnancy. Our findings suggest that modifiable risk factors of WT are parental occupational exposure to pesticides, breastfeeding (beneficial), and intake of folic acid during preconception / pregnancy (beneficial), but all associations were rather modest in strength.

Long-term outcomes and patterns of relapse in patients with bilateral Wilms tumor or bilaterally predisposed unilateral Wilms tumor, a report from the COG AREN0534 study

The objective of this study is to report the long-term timing and patterns of relapse for children enrolled in Children's Oncology Group AREN0534, a multicenter phase III clinical trial conducted from 2009 to 2015. Participants included children with bilateral Wilms tumor (BWT) or unilateral WT with genetic predisposition to develop BWT followed for up to 10 years. Smoothed hazard (risk) functions for event-free survival (EFS) were plotted so that the timing of events could be visualized, both overall and within pre-specified groups. Two hundred and twenty-two children (190 BWT and 32 unilateral WT with BWT predisposition) were followed for a median of 8.6 years. Fifty events were reported, of which 48 were relapse/progression. The overall 8-year EFS was 75% (95% confidence interval: 69%-83%). The highest risk for an EFS event was immediately after diagnosis with a declining rate over 2 years. A second peak of events was observed around 4 years after diagnosis, and a small number of events were reported until the end of the follow-up period. In subset analyses, later increases in risk were more commonly observed in patients with female sex, anaplastic histology, negative lymph nodes or margins, and favorable histology Wilms tumor patients with post-chemotherapy intermediate risk. Among relapses that occurred after 2 years, most were to the kidney. These patterns suggest that late events may be second primary tumors occurring more commonly in females, although more investigation is required. Clinicians may consider observation of patients with BWT beyond 4 years from diagnosis.

Two-hit mutation causes Wilms tumor in an individual with FBXW7-related neurodevelopmental syndrome

FBXW7 (F-box and WD-repeat domain-containing 7) is a tumor suppressor gene, and its germline variants have been causally linked to Wilms tumors. Furthermore, germline variants of FBXW7 have also been implicated in a neurodevelopmental syndrome. However, little is known regarding the occurrence of Wilms tumor in patients with FBXW7-related neurodevelopmental syndrome. We identified a novel constitutional pathogenic variant of FBXW7 in a patient with intellectual disability, who also developed Wilms tumor. The variant was derived from his apparently normal mother, and was also detected in his sister who exhibited developmental delay. Furthermore, we detected a somatic nonsense variant on the paternal allele of FBXW7 in the tumor DNA. These results suggest that the development of Wilms tumor along with FBXW7-related neurodevelopmental syndrome follows the two-hit model, which needs to be validated to establish appropriate follow-up management and tumor surveillance.

Further evidence that the neurodevelopmental gene FBXW7 predisposes to Wilms tumor

Somatic variants in the NOTCH pathway regulator FBXW7 are frequently seen in a variety of malignancies. Heterozygous loss-of-function germline variants in FBXW7 have recently been described as causative for a neurodevelopmental syndrome. Independently, FBXW7 was also considered as a susceptibility gene for Wilms tumor due to a few observations of heterozygous germline variants in patients with Wilms tumor. Whether the same FBXW7 variants are implicated in both, neurodevelopmental delay and Wilms tumor formation, remained unclear. By clinical testing, we now observed a patient with neurodevelopmental delay due to a de novo constitutional mosaic FBXW7 splice site pathogenic variant who developed Wilms tumor. In the tumor, we identified a second hit frameshift variant in FBXW7. Immunohistochemical staining was consistent with mosaic loss of FBXW7 protein expression in the tumor. Our data support the role of constitutional FBXW7 pathogenic variants in both, neurodevelopmental disorder and the etiology of Wilms tumor. Therefore, Wilms tumor screening should be considered in individuals with constitutional or germline pathogenic variants in FBXW7 and associated neurodevelopmental syndrome.

11p15 Epimutations in Pediatric Embryonic Tumors: Insights from a Methylome Analysis

Embryonic tumors share few recurrent mutations, suggesting that other mechanisms, such as aberrant DNA methylation, play a prominent role in their development. The loss of imprinting (LOI) at the chromosome region 11p15 is the germline alteration behind Beckwith-Wiedemann syndrome that results in an increased risk of developing several embryonic tumors. This study analyzed the methylome, using EPIC Beadchip arrays from 99 sporadic embryonic tumors. Among these tumors, 46.5% and 14.6% presented alterations at imprinted control regions (ICRs) 1 and 2, respectively. Based on the methylation levels of ICR1 and ICR2, four clusters formed with distinct methylation patterns, mostly for medulloblastomas (ICR1 loss of methylation (LOM)), Wilms tumors, and hepatoblastomas (ICR1 gain of methylation (GOM), with or without ICR2 LOM). To validate the results, the methylation status of 29 cases was assessed with MS-MLPA, and a high level of agreement was found between both methodologies: 93% for ICR1 and 79% for ICR2. The MS-MLPA results indicate that 15 (51.7%) had ICR1 GOM and 11 (37.9%) had ICR2 LOM. To further validate our findings, the ICR1 methylation status was characterized via digital PCR (dPCR) in cell-free DNA (cfDNA) extracted from peripheral blood. At diagnosis, we detected alterations in the methylation levels of ICR1 in 62% of the cases, with an agreement of 76% between the tumor tissue (MS-MLPA) and cfDNA methods. Among the disagreements, the dPCR was able to detect ICR1 methylation level changes presented at heterogeneous levels in the tumor tissue, which were detected only in the methylome analysis. This study highlights the prevalence of 11p15 methylation status in sporadic embryonic tumors, with differences relating to methylation levels (gain or loss), location (ICR1 or ICR2), and tumor types (medulloblastomas, Wilms tumors, and hepatoblastomas).