Circulating tumor DNA (ctDNA) is a powerful tool for the molecular characterization of cancer. The most frequent pediatric kidney tumors (KT) are Wilms’ tumors (WT), but other diagnoses may occur. ...According to the SIOP strategy, in most countries pediatric KT have a presumptive diagnosis of WT if they are clinically and radiologically compatible. The histologic confirmation is established after post‐chemotherapy nephrectomy. Thus, there is a risk for a small fraction of patients to receive neoadjuvant chemotherapy that is not adapted to the disease. The aim of this work is to perform molecular diagnosis of pediatric KT by tumor genetic characterization based on the analysis of ctDNA. We analyzed ctDNA extracted from plasma samples of 18 pediatric patients with KT by whole‐exome sequencing and compared the results to their matched tumor and germline DNA. Copy number alterations (CNAs) and single nucleotide variations (SNVs) were analyzed. We were able to detect tumor cell specific genetic alterations—CNAs, SNVs or both—in ctDNA in all patients except in one (for whom the plasma sample was obtained long after nephrectomy). These results open the door to new applications for the study of ctDNA with regards to the molecular diagnosis of KT, with a possibility of its usefulness for adapting the treatment early after diagnosis, but also for disease monitoring and follow up.
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The analysis of cell‐free DNA (cfDNA) in pediatric patients with kidney tumors is of interest for the molecular diagnosis and early identification of aggressive disease subtypes. In this study, significant amounts of circulating tumor DNA (ctDNA) were successfully isolated from pediatric patients with malignant kidney tumors. Accurate copy number profile and mutation calling to identify specific tumor cell genetic alterations was performed with whole‐exome sequencing using only low volumes of blood (≥100 μL) and low amounts of cfDNA (≥4 ng). The findings suggest that ctDNA analysis can facilitate the molecular diagnosis of specific subtypes of pediatric kidney tumors, potentially enabling earlier treatment.
In the clinical management of paediatric solid tumours, histological examination of tumour tissue obtained by a biopsy remains the gold standard to establish a conclusive pathological diagnosis. The ...DNA methylation pattern of a tumour is known to correlate with the histopathological diagnosis across cancer types and is showing promise in the diagnostic workup of tumour samples. This methylation pattern can be detected in the cell-free DNA. Here, we provide proof-of-concept of histopathologic classification of paediatric tumours using cell-free reduced representation bisulphite sequencing (cf-RRBS) from retrospectively collected plasma and cerebrospinal fluid samples. We determined the correct tumour type in 49 out of 60 (81.6%) samples starting from minute amounts (less than 10 ng) of cell-free DNA. We demonstrate that the majority of misclassifications were associated with sample quality and not with the extent of disease. Our approach has the potential to help tackle some of the remaining diagnostic challenges in paediatric oncology in a cost-effective and minimally invasive manner.
Liquid biopsies are revolutionary tools used to detect tumor-specific genetic alterations in body fluids, including the use of cell-free DNA (cfDNA) for molecular diagnosis in cancer patients. In ...brain tumors, cerebrospinal fluid (CSF) cfDNA might be more informative than plasma cfDNA. Here, we assess the use of CSF cfDNA in pediatric embryonal brain tumors (EBT) for molecular diagnosis.
The CSF cfDNA of pediatric patients with medulloblastoma (
= 18), ATRT (
= 3), ETMR (
= 1), CNS NB FOXR2 (
= 2) and pediatric EBT NOS (
= 1) (mean cfDNA concentration 48 ng/mL; range 4-442 ng/mL) and matched tumor genomic DNA were sequenced by WES and/or a targeted sequencing approach to determine single-nucleotide variations (SNVs) and copy number alterations (CNA). A specific capture covering transcription start sites (TSS) of genes of interest was also used for nucleosome footprinting in CSF cfDNA.
15/25 CSF cfDNA samples yielded informative results, with informative CNA and SNVs in 11 and 15 cases, respectively. For cases with paired tumor and CSF cfDNA WES (
= 15), a mean of 83 (range 1-160) shared SNVs were observed, including SNVs in classical medulloblastoma genes such as SMO and KMT2D. Interestingly, tumor-specific SNVs (mean 18; range 1-62) or CSF-specific SNVs (mean 5; range 0-25) were also observed, suggesting clonal heterogeneity. The TSS panel resulted in differential coverage profiles across all 112 studied genes in 7 cases, indicating distinct promoter accessibility.
CSF cfDNA sequencing yielded informative results in 60% (15/25) of all cases, with informative results in 83% (15/18) of all cases analyzed by WES. These results pave the way for the implementation of these novel approaches for molecular diagnosis and minimal residual disease monitoring.
Sequencing of cell-free DNA in the blood of cancer patients (liquid biopsy) provides attractive opportunities for early diagnosis, assessment of treatment response, and minimally invasive disease ...monitoring. To unlock liquid biopsy analysis for pediatric tumors with few genetic aberrations, we introduce an integrated genetic/epigenetic analysis method and demonstrate its utility on 241 deep whole-genome sequencing profiles of 95 patients with Ewing sarcoma and 31 patients with other pediatric sarcomas. Our method achieves sensitive detection and classification of circulating tumor DNA in peripheral blood independent of any genetic alterations. Moreover, we benchmark different metrics for cell-free DNA fragmentation analysis, and we introduce the LIQUORICE algorithm for detecting circulating tumor DNA based on cancer-specific chromatin signatures. Finally, we combine several fragmentation-based metrics into an integrated machine learning classifier for liquid biopsy analysis that exploits widespread epigenetic deregulation and is tailored to cancers with low mutation rates. Clinical associations highlight the potential value of cfDNA fragmentation patterns as prognostic biomarkers in Ewing sarcoma. In summary, our study provides a comprehensive analysis of circulating tumor DNA beyond recurrent genetic aberrations, and it renders the benefits of liquid biopsy more readily accessible for childhood cancers.
The majority of patients with neuroblastoma have tumors that initially respond to chemotherapy, but a large proportion will experience therapy-resistant relapses. The molecular basis of this ...aggressive phenotype is unknown. Whole-genome sequencing of 23 paired diagnostic and relapse neuroblastomas showed clonal evolution from the diagnostic tumor, with a median of 29 somatic mutations unique to the relapse sample. Eighteen of the 23 relapse tumors (78%) showed mutations predicted to activate the RAS-MAPK pathway. Seven of these events were detected only in the relapse tumor, whereas the others showed clonal enrichment. In neuroblastoma cell lines, we also detected a high frequency of activating mutations in the RAS-MAPK pathway (11/18; 61%), and these lesions predicted sensitivity to MEK inhibition in vitro and in vivo. Our findings provide a rationale for genetic characterization of relapse neuroblastomas and show that RAS-MAPK pathway mutations may function as a biomarker for new therapeutic approaches to refractory disease.
Abstract
Liquid biopsies are revolutionary tools to detect tumour-specific genetic alterations in body fluids. Here, we assess whether the circulating tumor DNA (ctDNA) in Cerebral Spinal Fluid (CSF) ...could be used for the tumor genetic profiling of pediatric embryonal brain tumors (EBT). Cell free DNA extracted from CSF from 4-5 lumbar puncture droplets from patients with Medulloblastoma (n=18), ATRT (n=3), ETMR(n=1), FOXR2 EBT (n=2) or other pediatric EBT (n=1) (cfDNA mean quantity 48 ng/ml ; range 5.6 - 442 ng/ml) and matched genomic DNA from primary tumors were sequenced by WES (Illumina 100PE) using Nimblegen Medexome Capture. SNVs/mutations were called using GATK-UnifiedGenotyper, GATK-HaplotypeCaller and Samtools. Copy Number profiles were generated with CNVkits. 10/13 cfDNA WES yielded satisfactory depth (>10x). A mean of 466 (range 93-945) SNVs were detected in the primary tumor and 474 (range 18-922) in the CSF. A mean of 416 (range 18-872) commons SNVs were observed between the cfDNA and the primary tumor, comprising classical medulloblastoma genes such as SMO or MLL2. Interestingly, several SNVs were observed either in the tumor only (mean 50 ; range 3-115) or in CSF only (mean 58 ; range 0-148) suggesting a clonal heterogeneity. For 5 cases, Copy Number profiles were also available, allowing the detection of MYCN amplification or 19q13 miRNA cluster amplification. Altogether, we demonstrate the feasibility of WES on CSF with a low input of ctDNA. These results may pave the way for new tumor monitoring tools.
Paediatric tumours are often characterised by the presence of recurrent DNA copy number alterations (CNAs). These DNA copy number profiles, obtained from a tissue biopsy, can aid in the correct ...prognostic classification and therapeutic stratification of several paediatric cancer entities (e.g. MYCN amplification in neuroblastoma) and are part of the routine diagnostic practice. Liquid biopsies (LQBs) offer a potentially safer alternative for such invasive tumour tissue biopsies and can provide deeper insight into tumour heterogeneity.
The robustness and reliability of LQB CNA analyses was evaluated. We performed retrospective CNA profiling using shallow whole-genome sequencing (sWGS) on paired plasma circulating cell-free DNA (cfDNA) and tissue DNA samples from routinely collected samples from paediatric patients (n = 128) representing different tumour entities, including osteosarcoma, Ewing sarcoma, rhabdomyosarcoma, Wilms tumour, brain tumours and neuroblastoma.
Overall, we observed a good concordance between CNAs in tissue DNA and cfDNA. The main cause of CNA discordance was found to be low cfDNA sample quality (i.e. the ratio of cfDNA (<700 bp) and high molecular weight DNA (>700 bp)). Furthermore, CNAs were observed that were present in cfDNA and not in tissue DNA, or vice-versa. In neuroblastoma samples, no false-positives or false-negatives were identified for the detection of the prognostic marker MYCN amplification.
In future prospective studies, CNA analysis on LQBs that are of sufficient quality can serve as a complementary assay for CNA analysis on tissue biopsies, as either cfDNA or tissue DNA can contain CNAs that cannot be identified in the other biomaterial.
•Overall, concordance between copy number aberrations in tissue and plasma is good.•Discordance was associated with low-quality cfDNA samples and localised disease.•Copy number aberrations can be unique to either tissue DNA or tumour DNA.•No false-positives or false-negatives were seen for MYCN detection in neuroblastoma cases.
The analysis of circulating tumor DNA (ctDNA), a fraction of total cell-free DNA (cfDNA), might be of special interest in retinoblastoma patients. Because the accessibility to tumor tissue is very ...limited in these patients, either for histopathological diagnosis of suspicious intraocular masses (biopsies are proscribed) or for somatic RB1 studies and genetic counseling (due to current successful conservative approaches), we aim to validate the detection of ctDNA in plasma of non-hereditary retinoblastoma patients by molecular analysis of RB1 gene.
In a cohort of 19 intraocular unilateral non-hereditary retinoblastoma patients for whom a plasma sample was available at diagnosis, we performed high-deep next-generation sequencing (NGS) of RB1 in cfDNA. Two different bioinformatics/statistics approaches were applied depending on whether the somatic RB1 status was available or not.
Median plasma sample volume was 600 μL 100–1000; median cfDNA plasma concentration was 119 38–1980 and 27 11–653 ng/mL at diagnosis and after complete remission, respectively. In the subgroup of patients with known somatic RB1 alterations (n = 11), seven of nine somatic mutations were detected (median allele fraction: 6.7%). In patients without identified somatic RB1 alterations (n = 8), six candidate variants were identified for seven patients.
Despite small tumor size, blood-ocular barrier, poor ctDNA blood release and limited plasma sample volumes, we confirm that it is possible to detect ctDNA with high-deep NGS in plasma from patients with intraocular non-hereditary retinoblastoma. This may aid in diagnosis of suspicious cases, family genetic counseling or follow-up of residual intraocular disease.
•Intraocular nonhereditary retinoblastoma releases circulating tumor DNA into blood.•Study of circulating tumor DNA might be useful in non-hereditary retinoblastoma.•Interest for the molecular diagnosis of suspicious intraocular masses.•Utility for somatic RB1 studies and genetic counseling of non-enucleated cases.
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