Families' experiences accessing care after genomic sequencing in the pediatric cancer context: "It's just been a big juggle".

Access to genomic sequencing (GS) and resulting recommendations have not been well described in pediatric oncology. GS results may provide a cancer predisposition syndrome (CPS) diagnosis that warrants screening and specialist visits beyond cancer treatment, including testing or surveillance for family members. The Texas KidsCanSeq (KCS) Study evaluated implementation of GS in a diverse pediatric oncology population. We conducted semi-structured interviews (n = 20) to explore experiences of KCS patients' families around learning about a CPS diagnosis and following up on recommended care. We used qualitative content analysis to develop themes and subthemes across families' descriptions of their experiences accessing care and to understand which factors presented barriers and/or facilitators. We found participants had difficulty differentiating which follow-up care recommendations were made for their child's current cancer treatment versus the CPS. In families' access to follow-up care for CPS, organizational factors were crucial: travel time and distance were common hardships, while coordination of care to streamline multiple appointments with different providers helped facilitate CPS care. Financial factors also impacted families' access to CPS-related follow-up care: having financial assistance and insurance were facilitators for families, while costs and lack of insurance posed as barriers for patients who lost coverage during transitions from pediatric to adult care, and for adult family members who had no coverage. Factors related to beliefs and perceptions, specifically perceiving the risk as less salient to them and feeling overwhelmed with the patient's cancer care, presented barriers to follow-up care primarily for family members. Regarding social factors, competing life priorities made it difficult for families to access follow-up care, though having community support alleviated these barriers. We suggest interventions to improve coordination of cancer treatment and CPS-related care and adherence to surveillance protocols for families as children age, such as care navigators and integrating longitudinal genetic counseling into hereditary cancer centers.

Circulating tumor DNA sequencing of pediatric solid and brain tumor patients: An institutional feasibility study.

The potential of circulating tumor DNA (ctDNA) analysis to serve as a real-time "liquid biopsy" for children with central nervous system (CNS) and non-CNS solid tumors remains to be fully elucidated. We conducted a study to investigate the feasibility and potential clinical utility of ctDNA sequencing in pediatric patients enrolled on an institutional clinical genomics trial. A total of 240 patients had tumor DNA profiling performed during the study period. Plasma samples were collected at study enrollment from 217 patients and then longitudinally from a subset of patients. Successful cell-free DNA extraction and quantification occurred in 216 of 217 (99.5%) of these initial samples. Twenty-four patients were identified whose tumors harbored 30 unique variants that were potentially detectable on a commercially-available ctDNA panel. Twenty of these 30 mutations (67%) were successfully detected by next-generation sequencing in the ctDNA from at least one plasma sample. The rate of ctDNA mutation detection was higher in patients with non-CNS solid tumors (7/9, 78%) compared to those with CNS tumors (9/15, 60%). A higher ctDNA mutation detection rate was also observed in patients with metastatic disease (9/10, 90%) compared to non-metastatic disease (7/14, 50%), although tumor-specific variants were detected in a few patients in the absence of radiographic evidence of disease. This study illustrates the feasibility of incorporating longitudinal ctDNA analysis into the management of relapsed or refractory patients with childhood CNS or non-CNS solid tumors.

Genetic markers for treatment-related pancreatitis in a cohort of Hispanic children with acute lymphoblastic leukemia.

PURPOSE: Treatment-related pancreatitis (TRP) is a serious complication occurring in children with acute lymphoblastic leukemia (ALL). Those affected are at high risk for severe organ toxicity and treatment delays that can impact outcomes. TRP is associated with asparaginase, a standard therapeutic agent in childhood ALL. Native American ancestry, older age, high-risk leukemia, and increased use of asparaginase are linked to pancreatitis risk. However, dedicated genetic studies evaluating pancreatitis in childhood ALL include few Hispanics. Thus, the genetic basis for higher risk of pancreatitis among Hispanic children with ALL remains unknown. METHODS: Cases of children with ALL treated in from 1994 through 2013 were reviewed and identified 14, all Hispanic, who developed pancreatitis related to asparaginase therapy. Forty-six controls consisting of Hispanic children treated on the same regimens without pancreatitis were selected for comparison. Total DNA isolated from whole blood was used for targeted DNA sequencing of 23 selected genes, including genes associated with pancreatitis without ALL and genes involved in asparagine metabolism. RESULTS: Non-synonymous polymorphisms and frameshift deletions were detected in 15 genes. Most children with TRP had variants in ABAT, ASNS, and CFTR. Notably, children with TRP harbored many more CFTR variants (71.4%) compared with controls (39.1%). Among these, V470M (rs213950) was most frequent (OR 4.27, p = 0.025). CONCLUSIONS: This is the first study of genetic factors in treatment-related pancreatitis in Hispanic children with ALL. Identifying correlative variants in ethnically vulnerable populations may improve screening to identify which patients with ALL are at greatest risk for pancreatitis.

Characterization of pediatric hepatocellular carcinoma reveals genomic heterogeneity and diverse signaling pathway activation.

BACKGROUND: Pediatric hepatocellular carcinoma (HCC) is a rare liver tumor in children with a poor prognosis. Comprehensive molecular profiling to understand the underlying genomic drivers of this tumor has not been completed, and it is unclear whether nonfibrolamellar pediatric HCC is more genomically similar to hepatoblastoma or adult HCC. PROCEDURE: To characterize the molecular landscape of these tumors, we analyzed a cohort of 15 pediatric non-FL-HCCs by sequencing a panel of cancer-associated genes and conducting copy-number and gene-expression analyses. RESULTS: We detected multiple types of molecular alterations in Wnt signaling genes, including APC inversion, AMER1 somatic mutation, and most commonly CTNNB1 intragenic deletions. There were multiple alterations to the telomerase pathway via TERT activation or ATRX mutation. Therapeutically targetable activating mutations in MAPK/ERK signaling pathway genes, including MAPK1 and BRAF, were detected in 20% of tumors. TP53 mutations occurred far less frequently in our pediatric HCC cohort than reported in adult cohorts. Tumors arising in children with underlying liver disease were found to be molecularly distinct from the remainder and lacking detectable oncogenic drivers, as compared with those arising in patients without a history of underlying liver disease; the majority of both types were positive for glypican-3, another potential therapeutic target. CONCLUSION: Our study revealed pediatric HCC to be a molecularly heterogeneous group of tumors. Those non-FL-HCC tumors arising in the absence of underlying liver disease harbor genetic alterations affecting multiple cancer pathways, most notably Wnt signaling, and share some characteristics with adult HCC.

Genomic analysis of hepatoblastoma identifies distinct molecular and prognostic subgroups.

Despite being the most common liver cancer in children, hepatoblastoma (HB) is a rare neoplasm. Consequently, few pretreatment tumors have been molecularly profiled, and there are no validated prognostic or therapeutic biomarkers for HB patients. We report on the first large-scale effort to profile pretreatment HBs at diagnosis. Our analysis of 88 clinically annotated HBs revealed three risk-stratifying molecular subtypes that are characterized by differential activation of hepatic progenitor cell markers and metabolic pathways: high-risk tumors were characterized by up-regulated nuclear factor, erythroid 2-like 2 activity; high lin-28 homolog B, high mobility group AT-hook 2, spalt-like transcription factor 4, and alpha-fetoprotein expression; and high coordinated expression of oncofetal proteins and stem-cell markers, while low-risk tumors had low lin-28 homolog B and lethal-7 expression and high hepatic nuclear factor 1 alpha activity. CONCLUSION: Analysis of immunohistochemical assays using antibodies targeting these genes in a prospective study of 35 HBs suggested that these candidate biomarkers have the potential to improve risk stratification and guide treatment decisions for HB patients at diagnosis; our results pave the way for clinical collaborative studies to validate candidate biomarkers and test their potential to improve outcome for HB patients. (Hepatology 2017;65:104-121).

Paraneoplastic Galactorrhea in Childhood T-ALL: An Evaluation of Tumor-derived Prolactin.

T-cell acute lymphoblastic leukemia (T-ALL) comprises 15% of childhood leukemia. Although multiagent pulse chemotherapy has improved event-free survival in recent decades, the lack of reliable prognosticators and high rate of relapse remain a challenge. Described is a novel discovery of tumor-derived hyperprolactinemia in childhood T-ALL through a case associated with paraneoplastic galactorrhea. Prolactin production by tumor cells, although a rare phenomenon, is previously demonstrated in several adult cancers and 2 pediatric malignancies with unknown implications. This is the first report demonstrating tumor-derived prolactin in pediatric T-ALL and offers potential as a disease marker and therapeutic drug target.

Long-term risk of medical conditions associated with breast cancer treatment.

Early and late effects of cancer treatment are of increasing concern with growing survivor populations, but relevant data are sparse. We sought to determine the prevalence and hazard ratio of such effects in breast cancer cases. Women with invasive breast cancer and women with no cancer history recruited for a cancer research cohort completed a mailed questionnaire at a median of 10 years post-diagnosis or matched reference year (for the women without cancer). Reported medical conditions including lymphedema, osteopenia, osteoporosis, and heart disease (congestive heart failure, myocardial infarction, coronary heart disease) were assessed in relation to breast cancer therapy and time since diagnosis using Cox regression. The proportion of women currently receiving treatment for these conditions was calculated. Study participants included 2,535 women with breast cancer and 2,428 women without cancer (response rates 66.0 % and 50.4 %, respectively) Women with breast cancer had an increased risk of lymphedema (Hazard ratio (HR) 8.6; 95 % confidence interval (CI) 6.3-11.6), osteopenia (HR 2.1; 95 % CI 1.8-2.4), and osteoporosis (HR 1.5; 95 % CI 1.2-1.9) but not heart disease, compared to women without cancer Hazard ratios varied by treatment and time since diagnosis. Overall, 49.3 % of breast cancer cases reported at least one medical condition, and at 10 or more years post-diagnosis, 37.7 % were currently receiving condition-related treatment. Responses from survivors a decade following cancer diagnosis demonstrate substantial treatment-related morbidity, and emphasize the need for continued medical surveillance and follow-up care into the second decade post-diagnosis.

Use of risk-reducing surgeries in a prospective cohort of 1,499 BRCA1 and BRCA2 mutation carriers.

Inherited mutations in BRCA1 or BRCA2 (BRCA1/2) confer very high risk of breast and ovarian cancers. Genetic testing and counseling can reduce risk and death from these cancers if appropriate preventive strategies are applied, including risk-reducing salpingo-oophorectomy (RRSO) or risk-reducing mastectomy (RRM). However, some women who might benefit from these interventions do not take full advantage of them. We evaluated RRSO and RRM use in a prospective cohort of 1,499 women with inherited BRCA1/2 mutations from 20 centers who enrolled in the study without prior cancer or RRSO or RRM and were followed forward for the occurrence of these events. We estimated the age-specific usage of RRSO/RRM in this cohort using Kaplan-Meier analyses. Use of RRSO was 45% for BRCA1 and 34% for BRCA2 by age 40, and 86% for BRCA1 and 71% for BRCA2 by age 50. RRM usage was estimated to be 46% by age 70 in both BRCA1 and BRCA2 carriers. BRCA1 mutation carriers underwent RRSO more frequently than BRCA2 mutation carriers overall, but the uptake of RRSO in BRCA2 was similar after mutation testing and in women born since 1960. RRM uptake was similar for both BRCA1 and BRCA2. Childbearing influenced the use of RRSO and RRM in both BRCA1 and BRCA2. Uptake of RRSO is high, but some women are still diagnosed with ovarian cancer before undergoing RRSO. This suggests that research is needed to understand the optimal timing of RRSO to maximize risk reduction and limit potential adverse consequences of RRSO.

Towards an international pediatric liver tumor consensus classification: proceedings of the Los Angeles COG liver tumors symposium.

Liver tumors are rare in children, and their diagnoses may be challenging particularly because of the lack of a current consensus classification system. Systematic central histopathological review of these tumors performed as part of the pediatric collaborative therapeutic protocols has allowed the identification of histologic subtypes with distinct clinical associations. As a result, histopathology has been incorporated within the Children's Oncology Group (COG) protocols, and only in the United States, as a risk-stratification parameter and for patient management. Therefore, the COG Liver Tumor Committee sponsored an International Pathology Symposium in March 2011 to discuss the histopathology and classification of pediatric liver tumors, and hepatoblastoma in particular, and work towards an International Pediatric Liver Tumors Consensus Classification that would be required for international collaborative projects. Twenty-two pathologists and experts in pediatric liver tumors, including those serving as central reviewers for the COG, European Société Internationale d'Oncologie Pédiatrique, Gesellschaft für Pädiatrische Onkologie und Hämatologie, and Japanese Study Group for Pediatric Liver Tumors protocols, as well as pediatric oncologists and surgeons specialized in this field, reviewed more than 50 pediatric liver tumor cases and discussed classic and newly reported entities, as well as criteria for their classification. This symposium represented the first collaborative step to develop a classification that may lead to a common treatment-stratification system incorporating tumor histopathology. A standardized, clinically meaningful classification will also be necessary to allow the integration of new biological parameters and to move towards clinical algorithms based on patient characteristics and tumor genetics, which should improve future patient management and outcome.

Congenital abnormalities and hepatoblastoma: a report from the Children's Oncology Group (COG) and the Utah Population Database (UPDB).

Beckwith-Wiedemann Syndrome (BWS) and familial adenomatous polyposis (FAP) are known to predispose to hepatoblastoma (HB). A case-control study was conducted through the Children's Oncology Group (COG) to study the association of HB with isolated congenital abnormalities. Cases (N = 383) were diagnosed between 2000 and 2008. Controls (N = 387) were recruited from state birth registries, frequency matched for sex, region, year of birth, and birth weight. Data on congenital abnormalities among subjects and covariates were obtained by maternal telephone interview. Odds ratios (OR) and 95% confidence intervals (CI) describing the association between congenital abnormalities with HB, adjusted for sex, birth weight, maternal age and maternal education, were calculated using unconditional logistic regression. There was a significant association of HB with kidney, bladder, or sex organ abnormalities (OR = 4.75; 95% CI: 1.74-13) which appeared to be specific to kidney/bladder defects (OR = 4.3; 95% CI: 1.2-15.3) but not those of sex organs (OR = 1.24; 95% CI: 0.37-4.1). Elevated but non-significant ORs were found for spina bifida or other spinal defects (OR = 2.12; 95% CI: 0.39-11.7), large or multiple birthmarks (OR = 1.33; 95% CI: 0.81-2.21). The results were validated through the Utah Population Database (UPDB), a statewide population-based registry linking birth certificates, medical records, and cancer diagnoses. In the UPDB, there were 29 cases and 290 population controls matched 10:1 on sex and birth year. Consistent with the COG findings, kidney/bladder defects were associated with hepatoblastoma. These results confirm the association of HB with kidney/bladder abnormalities.

Neonatal medical exposures and characteristics of low birth weight hepatoblastoma cases: a report from the Children's Oncology Group.

BACKGROUND: Hepatoblastoma is a malignancy of young children. Low birth weight is associated with significantly increased risk of hepatoblastoma and neonatal medical exposures are hypothesized as contributors. This study represents the largest case-control study of hepatoblastoma to date and aimed to define the role of neonatal exposures in hepatoblastoma risk among low birth weight children. PROCEDURE: Incident hepatoblastoma cases who were born <2,500 g (N = 60), diagnosed between 2000 and 2008, were identified through the Children's Oncology Group. Controls were recruited through state birth registries (N = 51). Neonatal medical exposures were abstracted from medical records. Subjects from the Vermont Oxford Network were used for further comparisons, as were existing reports on neonatal medical exposures. RESULTS: Case-control comparisons were hindered by poor matching within birth weight strata. Cases were smaller and received more aggressive neonatal treatment compared to controls, and reflected high correlation levels between birth weight and treatments. Similar difficulty was encountered when comparing cases to Vermont Oxford Network subjects; cases were smaller and required more aggressive neonatal therapy. Furthermore, it appears hepatoblastoma cases were exposed to a greater number of diagnostic X-rays than in case series previously reported in the neonatal literature. CONCLUSIONS: This study presents the largest case series of hepatoblastoma in <2,500 g birth weight infants with accompanying neonatal medical exposure data. Findings confirm that birth weight is highly correlated with exposure intensity, and neonatal exposures are themselves highly correlated, which hampers the identification of a causal exposure among hepatoblastoma cases. Experimental models or genetic susceptibility testing may be more revealing of etiology.

Correction: Childhood cancer survival in the highly vulnerable population of South Texas: A cohort study.

[This corrects the article DOI: 10.1371/journal.pone.0278354.].

Disparate Rates of Germline Variants in Cancer Predisposition Genes in African American/Black Compared With Non-Hispanic White Individuals Between 2015 and 2022.

PURPOSE: African American/Black (AA/B) individuals are under-represented in genomic databases and thus less likely to receive definitive information from germline genetic testing (GGT) than non-Hispanic White (NHW) individuals. With nearly 500,000 AA/B and NHW individuals having undergone multigene panel testing (MGPT) for hereditary cancer risk at a single commercial laboratory, to our knowledge, we present the largest study to date investigating cancer GGT results in AA/B and NHW individuals. METHODS: MGPT results from a retrospective cohort of AA/B (n = 48,684) and NHW (n = 444,831) patients were evaluated. Frequencies of pathogenic germline variants (PGVs) and variants of uncertain significance (VUS) were compared between AA/B and NHW individuals. Changes in frequency of VUS over time were determined. Pearson's chi-squared test was used to compare categorical variables among groups. All significance tests were two-tailed, and P < .05 was considered statistically significant. RESULTS: Between 2015 and 2022, rates of VUS decreased 2.3-fold in AA/B and 1.8-fold in NHW individuals; however, frequencies of VUS and PGV remained significantly higher (46% v 32%; P < .0001) and lower (9% v 13%; P < .0001) in AA/B compared with NHW individuals. Rates of VUS in ATM, BRCA1, BRCA2, PALB2, and PMS2 were significantly higher in AA/B compared with NHW individuals, whereas rates of PGV in BRCA1, BRCA2, and PALB2 were higher in AA/B compared with NHW individuals (P < .001). CONCLUSION: Despite reductions in VUS frequencies over time, disparities in definitive GGT results persist. Increasing inclusion of AA/B populations in both testing and research will further increase knowledge of genetic variants across these racial groups.

The transcription factor Wilms tumor 1 confers resistance in myeloid leukemia cells against the proapoptotic therapeutic agent TRAIL (tumor necrosis factor α-related apoptosis-inducing ligand) by regulating the antiapoptotic protein Bcl-xL.

Tumor necrosis factor α-related apoptosis-inducing ligand (TRAIL) is considered a promising cancer therapeutic agent due to its ability to induce apoptosis in a variety of cancer cells, while sparing normal cells. However, many human tumors including acute myeloid leukemia (AML) are partially or completely resistant to monotherapy with TRAIL, limiting its therapeutic utility. Therefore, identification of factors that contribute to TRAIL resistance may facilitate future development of more effective TRAIL-based cancer therapies. Here, we report a previously unknown role for WT1 in mediating TRAIL resistance in leukemia. Knockdown of WT1 with shRNA rendered TRAIL-resistant myeloid leukemia cells sensitive to TRAIL-induced cell death, and re-expression of shRNA-resistant WT1 restored TRAIL resistance. Notably, TRAIL-mediated apoptosis in WT1-silenced cells was largely due to down-regulation of the antiapoptotic protein Bcl-xL. Moreover, WT1 expression strongly correlated with overexpression of Bcl-xL in AML cell lines and blasts from AML patients. Furthermore, we found that WT1 transactivates Bcl-xL by directly binding to its promoter. We previously showed that WT1 is a novel client protein of heat shock protein 90 (Hsp90). Consistent with this, pharmacological inhibition of Hsp90 resulted in reduced WT1 and Bcl-xL expression leading to increased sensitivity of leukemia cells to TRAIL-mediated apoptosis. Collectively, our results suggest that WT1-dependent Bcl-xL overexpression contributes to TRAIL resistance in myeloid leukemias.

Clinical, histologic, and genetic features of mesothelioma in a 7-year-old child.

Malignant mesothelioma (MM) is a highly aggressive malignancy that is extremely rare in children. This case report documents a 7-year-old male without previous asbestos exposure with peritoneal MM that initially responded to chemotherapy with cisplatin and gemcitabine but ultimately metastasized to his chest. He was diagnosed with MM based on histology, extensive immunohistochemical analyses, and an elevated serum CA-125 level. Cytogenetics and comparative genomic hybridization (CGH) analysis of his tumor identified a single extra copy number of chromosome 11 with few other changes noted.

Children's Oncology Group's 2013 blueprint for research: rare tumors.

In the US, approximately 2,000 children are diagnosed with rare cancers each year, with 5-year survival ranging from <20% for children with advanced carcinomas to >95% for children with intraocular retinoblastoma or localized germ cell tumors. During the last years, 12 clinical studies have been successfully completed in children with retinoblastoma, liver tumors, germ cell tumors, and infrequent malignancies, including therapeutic, epidemiologic, and biologic studies. Current efforts are centered in the development of large international collaborations to consolidate evidence-based definitions and risk stratifications that will support international Phase 3 clinical trials in germ cell tumors, hepatoblastoma, and other rare cancers.

Outcomes for patients with congenital hepatoblastoma.

BACKGROUND: Congenital hepatoblastoma, diagnosed in the first month of life, has been reported to have a poor prognosis; however, a comprehensive evaluation of this entity is lacking. PROCEDURE: We retrospectively reviewed two patients from the senior authors' personal series and 25 cases identified in the databases of several multicenter group studies (INT-0098, P9645, 881, P9346, HB 89, HB94, and HB 99). We compared this series with cases of congenital hepatoblastoma previously published in the literature. RESULTS: The 3-year survival in our case series was 86% (18/21) with a follow-up of 44-230 months (median 85.5 months). Presentation and treatment were not substantially different from hepatoblastoma cohorts unselected for age. Survival was comparable to the reported disease free survival for a similar cohort of hepatoblastoma patients unselected for age between 1986 and 2002 (82.5%) [von Schweinitz et al., Eur J Cancer 1997; 33:1243-1249]. The 2-year survival of cases reported in the literature was 0% (0/9) and 42% (10/24) for patients reported before and after 1990, respectively. CONCLUSIONS: Congenital hepatoblastoma does not appear to confer a worse prognosis. The improved survival of our current series of patients, collected from the past 20 years of German and American multicenter trials and personal series, suggests that the outcome of hepatoblastoma at this young age is much better than has been historically reported. More rigorous analysis should be conducted in future multicenter trials. It is possible that congenital hepatoblastoma should be treated like all other patients with hepatoblastoma provided that the child is stable enough to proceed with surgery and chemotherapy.

Childhood cancer survival in the highly vulnerable population of South Texas: A cohort study.

This study examines childhood cancer survival rates and prognostic factors related to survival in the majority Hispanic population of South Texas. The population-based cohort study used Texas Cancer Registry data (1995-2017) to examine survival and prognostic factors. Cox proportional hazard models and Kaplan-Meier survival curves were used for survival analyses. The 5-year relative survival rate for 7,999 South Texas cancer patients diagnosed at 0-19 years was 80.3% for all races/ethnicities. Hispanic patients had statistically significant lower 5-year relative survival rates than non-Hispanic White (NHW) patients for male and female together diagnosed at age≥5 years. When comparing survival among Hispanic and NHW patients for the most common cancer, acute lymphocytic leukemia (ALL), the difference was most significant in the 15-19 years age range, with 47.7% Hispanic patients surviving at 5 years compared to 78.4% of NHW counterparts. The multivariable-adjusted analysis showed that males had statistically significant 13% increased mortality risk than females [hazard ratio (HR): 1.13, 95% confidence interval (CI):1.01-1.26] for all cancer types. Comparing to patients diagnosed at ages 1-4 years, patients diagnosed at age < 1 year (HR: 1.69, 95% CI: 1.36-2.09), at 10-14 year (HR: 1.42, 95% CI: 1.20-1.68), or at 15-19 years (HR: 1.40, 95% CI: 1.20-1.64) had significant increased mortality risk. Comparing to NHW patients, Hispanic patients showed 38% significantly increased mortality risk for all cancer types, 66% for ALL, and 52% for brain cancer. South Texas Hispanic patients had lower 5-year relative survival than NHW patients especially for ALL. Male gender, diagnosis at age<1 year or 10-19 years were also associated with decreased childhood cancer survival. Despite advances in treatment, Hispanic patients lag significantly behind NHW patients. Further cohort studies in South Texas are warranted to identify additional factors affecting survival and to develop interventional strategies.

Defining function of wild-type and three patient-specific TP53 mutations in a zebrafish model of embryonal rhabdomyosarcoma.

In embryonal rhabdomyosarcoma (ERMS) and generally in sarcomas, the role of wild-type and loss- or gain-of-function TP53 mutations remains largely undefined. Eliminating mutant or restoring wild-type p53 is challenging; nevertheless, understanding p53 variant effects on tumorigenesis remains central to realizing better treatment outcomes. In ERMS, >70% of patients retain wild-type TP53, yet mutations when present are associated with worse prognosis. Employing a kRASG12D-driven ERMS tumor model and tp53 null (tp53-/-) zebrafish, we define wild-type and patient-specific TP53 mutant effects on tumorigenesis. We demonstrate that tp53 is a major suppressor of tumorigenesis, where tp53 loss expands tumor initiation from <35% to >97% of animals. Characterizing three patient-specific alleles reveals that TP53C176F partially retains wild-type p53 apoptotic activity that can be exploited, whereas TP53P153Δ and TP53Y220C encode two structurally related proteins with gain-of-function effects that predispose to head musculature ERMS. TP53P153Δ unexpectedly also predisposes to hedgehog-expressing medulloblastomas in the kRASG12D-driven ERMS-model.

Comprehensive characterization of patient-derived xenograft models of pediatric leukemia.

Patient-derived xenografts (PDX) remain valuable models for understanding the biology and for developing novel therapeutics. To expand current PDX models of childhood leukemia, we have developed new PDX models from Hispanic patients, a subgroup with a poorer overall outcome. Of 117 primary leukemia samples obtained, successful engraftment and serial passage in mice were achieved in 82 samples (70%). Hispanic patient samples engrafted at a rate (51/73, 70%) that was similar to non-Hispanic patient samples (31/45, 70%). With a new algorithm to remove mouse contamination in multi-omics datasets including methylation data, we found PDX models faithfully reflected somatic mutations, copy-number alterations, RNA expression, gene fusions, whole-genome methylation patterns, and immunophenotypes found in primary tumor (PT) samples in the first 50 reported here. This cohort of characterized PDX childhood leukemias represents a valuable resource in that germline DNA sequencing has allowed the unambiguous determination of somatic mutations in both PT and PDX.