Update on cancer predisposition syndromes and surveillance guidelines for childhood brain tumors

Tumors of the central nervous system (CNS) comprise the second most common group of neoplasms in childhood. The incidence of germline predisposition among children with brain tumors continues to grow as our knowledge on disease aetiology increases. Some children with brain tumors may present with non-malignant phenotypic features of specific syndromes (e.g. nevoid basal cell carcinoma syndrome, neurofibromatosis type 1 and type 2, DICER1 syndrome, and constitutional mismatch repair deficiency), while others may present with a strong family history of cancer (e.g. Li-Fraumeni syndrome), or with a rare tumor commonly found in the context of germline predisposition (e.g. rhabdoid tumor predisposition syndrome). Approximately 50% of patients with a brain tumor may be the first in a family identified to have a predisposition. The past decade has witnessed a rapid expansion in our molecular understanding of CNS tumors. A significant proportion of CNS tumors are now well characterized and known to harbor specific genetic changes that can be found in the germline. Additional novel predisposition syndromes are also being described. Identification of these germline syndromes in individual patients has not only enabled cascade testing of family members and early tumor surveillance but increasingly has also impacted cancer management in those patients. Therefore, the AACR Cancer Predisposition Working Group chose to highlight these advances in CNS tumor predisposition and summarize and/or generate surveillance recommendations for established and more recently emerging pediatric brain tumor predisposition syndromes.

Pediatric cancer incidence among individuals with overgrowth syndromes and overgrowth features: A population-based assessment in seven million children

BACKGROUND

Overgrowth syndromes (e.g., Beckwith-Wiedemann) are associated with an increased risk of pediatric cancer, although there are few population-based estimates of risk. There are also limited studies describing associations between other overgrowth features (e.g., hepatosplenomegaly) and pediatric cancer. Therefore, cancer risk among children with these conditions was evaluated with data from a large, diverse population-based registry linkage study.

METHODS

This study includes all live births in Texas during the years 1999-2017. Children with overgrowth features and syndromes were identified from the Texas Birth Defects Registry; children with cancer were identified by linkage to the Texas Cancer Registry. Cox regression models were used to estimate the hazard ratio (HR) and 95% confidence interval (CI) for the association between each overgrowth syndrome/feature and cancer, which were adjusted for infant sex and maternal age.

RESULTS

In the total birth cohort (n = 6,997,422), 21,207 children were identified as having an overgrowth syndrome or feature. Children with Beckwith-Wiedemann syndrome were 42 times more likely to develop pediatric cancer (95% CI, 24.20-71.83), with hepatoblastoma being the most common, followed by Wilms tumor. The presence of any isolated overgrowth feature was associated with increased cancer risk (HR, 4.70; 95% CI, 3.83-5.77); associations were strongest for hepatosplenomegaly (HR, 23.04; 95% CI, 13.37-39.69) and macroglossia (HR, 11.18; 95% CI, 6.35-19.70).

CONCLUSIONS

This population-based assessment confirmed prior findings that children with either overgrowth syndromes or features were significantly more likely to develop cancer. Overall, this study supports recommendations for cancer surveillance in children with these conditions and may also inform future research into cancer etiology.

Combined Bioinformatic and Splicing Analysis of Likely Benign Intronic and Synonymous Variants Reveals Evidence for Pathogenicity

Background

Current clinical variant analysis pipelines focus on coding variants and intronic variants within 10-20 bases of an exon-intron boundary that may affect splicing. The impact of newer splicing prediction algorithms combined with in vitro splicing assays on rare variants currently considered Benign/Likely Benign (B/LB) is unknown.

Methods

Exome sequencing data from 576 pediatric cancer patients enrolled in the Texas KidsCanSeq study were filtered for intronic or synonymous variants absent from population databases, predicted to alter splicing via SpliceAI (>0.20), and scored as potentially deleterious by CADD (>10.0). Total cellular RNA was extracted from monocytes and RT-PCR products analyzed. Subsequently, rare synonymous or intronic B/LB variants in a subset of genes submitted to ClinVar were similarly evaluated. Variants predicted to lead to a frameshifted splicing product were functionally assessed using an in vitro splicing reporter assay in HEK-293T cells.

Results

KidsCanSeq exome data analysis revealed a rare, heterozygous, intronic variant (NM_177438.3(DICER1):c.574-26A>G) predicted by SpliceAI to result in gain of a secondary splice acceptor site. The proband had a personal and family history of pleuropulmonary blastoma consistent with DICER1 syndrome but negative clinical sequencing reports. Proband RNA analysis revealed alternative DICER1 transcripts including the SpliceAI-predicted transcript.Similar bioinformatic analysis of synonymous or intronic B/LB variants (n=31,715) in ClinVar from 61 Mendelian disease genes yielded 18 variants, none of which could be scored by MaxEntScan. Eight of these variants were assessed (DICER1 n=4, CDH1 n=2, PALB2 n=2) using in vitro splice reporter assay and demonstrated abnormal splice products (mean 66%; range 6% to 100%). Available phenotypic information from submitting laboratories demonstrated DICER1 phenotypes in 2 families (1 variant) and breast cancer phenotypes for PALB2 in 3 families (2 variants).

Conclusions

Our results demonstrate the power of newer predictive splicing algorithms to highlight rare variants previously considered B/LB in patients with features of hereditary conditions. Incorporation of SpliceAI annotation of existing variant data combined with either direct RNA analysis or in vitro assays has the potential to identify disease-associated variants in patients without a molecular diagnosis.

Collaboration to Promote Research and Improve Clinical Care in the Evolving Field of Childhood Cancer Predisposition

Germline pathogenic variants in cancer susceptibility genes are identified in up to 18% of all children with cancer. Because pediatric cancer predisposition syndromes (CPS) themselves are rare and underrecognized, there are limited data to guide the diagnosis and management of affected children and at-risk relatives. Furthermore, the care of affected children requires distinct considerations given the early onset of cancers, lifelong risks of additional cancers, and potential late effects of therapy. Herein, we discuss efforts to leverage existing infrastructure, organize experts, and develop a new consortium to optimize care and advance research for children with CPS. A 2016 workshop organized by the American Association for Cancer Research united many experts in childhood cancer predisposition and resulted in publication of multiple consensus guidelines for tumor surveillance. More recently, several of these authors established the Consortium for Childhood Cancer Predisposition (C3P), a multi-institutional collaboration that provides a structure for systematic research in cancer predisposition, screening, and prevention in children. The Consortium intends to work with other cooperative groups to merge longitudinal data from children with CPS throughout the continuum of the cancer risk period, as well as cancer treatment and survivorship care, to optimize overall outcomes.

Gadolinium is not necessary for surveillance MR imaging in children with chiasmatic-hypothalamic low-grade glioma

BACKGROUND

Patients with chiasmatic-hypothalamic low-grade glioma (CHLGG) have frequent MRIs with gadolinium-based contrast agents (GBCA) for disease monitoring. Cumulative gadolinium deposition in the brains of children is a potential concern. The purpose of this study is to evaluate whether MRI with GBCA is necessary for determining radiographic tumor progression in children with CHLGG.

METHODS

Children who were treated for progressive CHLGG from 2005 to 2019 at Texas Children's Cancer Center were identified. Pre- and post-contrast MRI sequences were separately reviewed by one neuroradiologist who was blinded to the clinical course. Three dimensional measurements and tumor characteristics were evaluated. Radiographic progression was defined as a 25% increase in size (product of two largest dimensions) compared with baseline or best response after initiation of therapy.

RESULTS

A total of 28 patients with progressive CHLGG were identified with a total of 683 MRIs with GBCA reviewed (mean 24 MRIs/patient; range, 11-43 MRIs). Radiographic progression was observed 92 times, 91 (99%) on noncontrast and 90 (98%) on contrast imaging. Sixty-seven progressions necessitating management changes were identified in all (100%) noncontrast sequences and 66 (99%) contrast sequences. Tumor growth > 2 mm in any dimension was identified in 184/187 (98%) noncontrast and 181/187 (97%) with contrast imaging. Metastatic tumors were better visualized on contrast imaging in 4/7 (57%).

CONCLUSION

MRI without GBCA effectively identifies patients with progressive disease. When imaging children with CHLGG, eliminating GBCA should be considered unless monitoring patients with metastatic disease.

Impact of vascular anomalies on the PTEN phenotype in children and young adults

Germline PTEN (phosphatase and tensin homolog) mutations lead to inappropriate cell survival and growth, and a predisposition to multiple cancers. Some patients also have vascular anomalies (VAs), and it is unclear whether these patients have different phenotypes or oncologic risks. We conducted a two-institution retrospective cohort study to better understand the phenotypes of children and young adults with PTEN mutations, and to compare individuals with VA to those without. Almost half of the patients had thyroid tumors and nearly one quarter developed gastrointestinal tumors before 30 years of age. The presence of VA was positively associated with bulky overgrowth but did not appear to modify oncologic risk.

Abstract 1575: DNA methylation-derived neutrophil-to-lymphocyte ratio and survival among pediatric medulloblastoma patients

Background/Objectives: Medulloblastoma is the most common malignant brain tumor diagnosed in children. Current risk-stratification methods of pediatric medulloblastoma do not fully explain the observed variability in clinical outcomes. Methylation-derived neutrophil-to-lymphocyte ratio (mdNLR) captures immune-specific information and has been identified as a potential prognostic biomarker of outcomes in various cancers, including adult brain tumors. Therefore, we evaluated the association between blood-derived mdNLR and overall survival in a cohort of patients with pediatric medulloblastoma.

Design/Methods: We identified pediatric patients diagnosed and treated for medulloblastoma at Texas Children’s Cancer Center between 1995 and 2015. Peripheral blood DNA methylation was measured using the Infinium Human Methylation 450K Beadchip. Methylation data underwent quality control, including beta-mixture quantile normalization and batch correction. Immune cell proportions (CD4+ T-Cells, CD8+ T-Cells, B-cells, natural killer cells, monocytes, and granulocytes) were estimated using cellular deconvolution methods and used to estimate mdNLR, which was then log-transformed to improve normality. Cox regression models were estimated to evaluate the association between mdNLR and overall survival.

Results: Of the 78 eligible patients include in this analysis, 83% (n=65) were alive at last follow-up (median follow-up=7.8 years). Deceased patients (n=13; median follow-up=2.6 years) had a higher mean mdNLR than patients who were alive at last contact (12.3 vs. 4.0, P = 0.046). Elevated log-transformed mdNLR was associated with an increased risk of death in both unadjusted models (HR=1.68, 95%CI: 1.11-2.55) and models accounting for age, sex, race, and clinical risk group (HR=1.97, 95%CI: 1.12-3.45).

Conclusion: We identified a significant association between peripheral blood mdNLR and survival in pediatric medulloblastoma. As a promising prognostic biomarker of outcomes, mdNLR captures immune-specific information and is a potential avenue of research in settings where cytologic determination of NLR may not be possible. Future work should investigate the relationship between elevated mdNLR and specific pediatric medulloblastoma molecular subtypes.

Citation Format: Vidal M. Arroyo, Philip J. Lupo, Michael E. Scheurer, Surya P. Rednam, Jeffrey C. Murray, M F. Okcu, Murali M. Chintagumpala, Austin L. Brown. DNA methylation-derived neutrophil-to-lymphocyte ratio and survival among pediatric medulloblastoma patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1575.

Gliomas in the context of Li-Fraumeni syndrome: An international cohort

1517

Background: Li-Fraumeni syndrome (LFS) is a cancer predisposition syndrome associated with germline mutation in the TP53 tumor suppressor gene. As a result of increased awareness and surveillance imaging, more asymptomatic low-grade brain lesions are being identified, raising important questions regarding the management of those patients. Sporadic low-grade gliomas (LGG) in the pediatric age rarely transform to malignant lesions, whereas the prognosis of high-grade gliomas (HGG) is grim in all age groups. Although HGG is a hallmark of LFS, little is known of the natural history of these lesions in this syndrome. Methods: For this multi-institutional retrospective study, anonymized clinicopathologic data from TP53 mutation carriers with gliomas were collected and analysed. Results: Our cohort included 61 patients, of whom 71% (n = 45) were children or young adults (age < 25 years). 39% of patients with known family history of cancer had a close relative with a brain tumor. Of 31 patients with low grade lesions at presentation, 83% (n = 26) were identified through surveillance. Five-year progression free survival (PFS) for these patients was 48%, though two patients progressed later. Furthermore, at 5 years 25% of these patients had biopsy proven malignant transformation to HGG. This “transformation free survival” rate did not plateau, as at 7 years 56% of patients transformed. When considering death from a brain tumor, the 5- and 10- year overall survival (OS) for the LGG group was 100% and 83%, respectively. Additional 3 patients succumbed to other LFS related malignancies. For the HGG group, consisting of 30 patients, the 5 year OS was 35% (median follow-up 19.5 months), comparing favorably with the sporadic HGG population as reported in the literature. Almost all of these patients presented with clinical symptoms. Notably, 12 (40%) of them had a prior malignancy. Conclusions: Our analysis suggests that the risk of transformation of LGG in the setting of LFS is high and warrants ongoing surveillance. Interestingly, there are a considerable number of long- term survivors in our HGG group, although the median follow up is still short. Further study to examine potential genotype- phenotype correlations in germline TP53 mutation carriers will inform strategies to identify those patients at highest risk of glioma progression.

Pilot study of DNA methylation-derived neutrophil-to-lymphocyte ratio and survival in pediatric medulloblastoma

INTRODUCTION

Methylation-derived neutrophil-to-lymphocyte ratio (mdNLR) has been identified as a potential prognostic biomarker of outcomes in various cancers. We evaluated the prognostic value of blood-derived mdNLR within a retrospective cohort of pediatric medulloblastoma patients.

MATERIALS AND METHODS

DNA methylation was measured in archival peripheral blood samples collected on 56 pediatric medulloblastoma patients. Hazard ratios (HR) and 95% confidence intervals (CI) for the association between mdNLR and survival were evaluated using Cox proportional hazard models.

RESULTS

Compared to patients who were alive at last follow-up (n = 43), the mean mdNLR value was slightly higher in deceased patients (n = 13) (12.3 vs. 5.2,P =  0.163). Elevated log-transformed mdNLR was suggestively associated with an increased likelihood of death in unadjusted models (HR=1.43, 95%CI: 0.92-2.22) and significantly associated with mortality in adjusted models (HR=1.61, 95%CI: 1.01-2.58).

DISCUSSION

Future work is warranted to investigate the relationship between mdNLR outcomes in specific pediatric medulloblastoma molecular subgroups.

Considerations for total thyroidectomy in an adolescent with PTEN mutation

Individuals with PTEN Hamartoma Tumor Syndrome (PHTS) are at greatly increased risk for developing well-differentiated thyroid cancer. Specific circumstances in which total thyroidectomies should be considered have not been defined. A 14-year-old macrocephalic female with history of developmental delay and lipoma over her left flank presented with neck swelling and was found have multinodular goiter and auto-immune thyroiditis. Asymptomatic tracheal narrowing was also detected on her initial diagnostic imaging. Later on, she developed positional dyspnea during sleep. Genetic testing revealed a heterozygous pathogenic variant in the PTEN gene (c.463T>A). A total thyroidectomy was performed. In addition to addressing the symptomology in our case, a total thyroidectomy also fortuitously eliminated the thyroid cancer risk. This case spurred us on further to identify specific clinical scenarios where total thyroidectomy may be considered as a true prophylactic measure to manage thyroid cancer risk in PHTS patients.

DNA methylation of a novel PAK4 locus influences ototoxicity susceptibility following cisplatin and radiation therapy for pediatric embryonal tumors

Background

Ototoxicity is a common adverse side effect of platinum chemotherapy and cranial radiation therapy; however, individual susceptibility is highly variable. Therefore, our objective was to conduct an epigenome-wide association study to identify differentially methylated cytosine-phosphate-guanine (CpG) sites associated with ototoxicity susceptibility among cisplatin-treated pediatric patients with embryonal tumors.

Methods

Samples were collected for a discovery cohort (n = 62) and a replication cohort (n = 18) of medulloblastoma and primitive neuroectodermal tumor patients. Posttreatment audiograms were evaluated using the International Society of Paediatric Oncology (SIOP) Boston Ototoxicity Scale. Genome-wide associations between CpG methylation and ototoxicity were examined using multiple linear regression, controlling for demographic and treatment factors.

Results

The mean cumulative dose of cisplatin was 330 mg/m2 and the mean time from end of therapy to the last available audiogram was 6.9 years. In the discovery analysis of 435233 CpG sites, 6 sites were associated with ototoxicity grade (P < 5 × 10-5) after adjusting for confounders. Differential methylation at the top CpG site identified in the discovery cohort (cg14010619, PAK4 gene) was replicated (P = 0.029) and reached genome-wide significance (P = 2.73 × 10-8) in a combined analysis. These findings were robust to a sensitivity analysis evaluating other potential confounders.

Conclusions

We identified and replicated a novel CpG methylation loci (cg14010619) associated with ototoxicity severity. Methylation at cg14010619 may modify PAK4 activity, which has been implicated in cisplatin resistance in malignant cell lines.

Multiple Endocrine Neoplasia and Hyperparathyroid-Jaw Tumor Syndromes: Clinical Features, Genetics, and Surveillance Recommendations in Childhood

Children and adolescents who present with neuroendocrine tumors are at extremely high likelihood of having an underlying germline predisposition for the multiple endocrine neoplasia (MEN) syndromes, including MEN1, MEN2A and MEN2B, MEN4, and hyperparathyroid-jaw tumor (HPT-JT) syndromes. Each of these autosomal dominant syndromes results from a specific germline mutation in unique genes: MEN1 is due to pathogenic MEN1 variants (11q13), MEN2A and MEN2B are due to pathogenic RET variants (10q11.21), MEN4 is due to pathogenic CDKN1B variants (12p13.1), and the HPT-JT syndrome is due to pathogenic CDC73 variants (1q25). Although each of these genetic syndromes share the presence of neuroendocrine tumors, each syndrome has a slightly different tumor spectrum with specific surveillance recommendations based upon tumor penetrance, including the age and location for which specific tumor types most commonly present. Although the recommended surveillance strategies for each syndrome contain similar approaches, important differences do exist among them. Therefore, it is important for caregivers of children and adolescents with these syndromes to become familiar with the unique diagnostic criteria for each syndrome, and also to be aware of the specific tumor screening and prophylactic surgery recommendations for each syndrome. Clin Cancer Res; 23(13); e123-e32. ©2017 AACRSee all articles in the online-only CCR Pediatric Oncology Series.

Von Hippel-Lindau and Hereditary Pheochromocytoma/Paraganglioma Syndromes: Clinical Features, Genetics, and Surveillance Recommendations in Childhood

Von Hippel-Lindau disease (vHL) is a hereditary tumor predisposition syndrome that places affected individuals at risk for multiple tumors, which are predominantly benign and generally occur in the central nervous system or abdomen. Although the majority of tumors occur in adults, children and adolescents with the condition develop a significant proportion of vHL manifestations and are vulnerable to delayed tumor detection and their sequelae. Although multiple tumor screening paradigms are currently being utilized for patients with vHL, surveillance should be reassessed as the available relevant clinical information continues to expand. We propose a new vHL screening paradigm similar to existing approaches, with important modifications for some tumor types, placing an emphasis on risks in childhood. This includes advancement in the timing of surveillance initiation and increased frequency of screening evaluations. Another neuroendocrine-related familial condition is the rapidly expanding hereditary paraganglioma and pheochromocytoma syndrome (HPP). The tumor spectrum for patients with HPP syndrome includes paragangliomas, pheochromocytomas, renal cancer, and gastrointestinal stromal tumors. The majority of patients with HPP syndrome harbor an underlying variant in one of the SHDx genes (SDHA, SDHB, SDHC, SDHD, SDHA, and SDHAF2), although other genes also have been described (MAX and TMEM127). Annual screening for elevated plasma or urine markers along with complete blood count and biennial whole-body MRI accompanied by focal neck MRI is recommended for older children and adults with HPP syndrome to detect tumors early and to decrease morbidity and mortality from HPP-related tumors. Clin Cancer Res; 23(12); e68-e75. ©2017 AACRSee all articles in the online-only CCR Pediatric Oncology Series.

PTEN, DICER1, FH, and Their Associated Tumor Susceptibility Syndromes: Clinical Features, Genetics, and Surveillance Recommendations in Childhood

PTEN hamartoma tumor syndrome (PHTS), DICER1 syndrome, and hereditary leiomyomatosis and renal cell cancer (HLRCC) syndrome are pleiotropic tumor predisposition syndromes that include benign and malignant neoplasms affecting adults and children. PHTS includes several disorders with shared and distinct clinical features. These are associated with elevated lifetime risk of breast, thyroid, endometrial, colorectal, and renal cancers as well as melanoma. Thyroid cancer represents the predominant cancer risk under age 20 years. DICER1 syndrome includes risk for pleuropulmonary blastoma, cystic nephroma, ovarian sex cord-stromal tumors, and multinodular goiter and thyroid carcinoma as well as brain tumors including pineoblastoma and pituitary blastoma. Individuals with HLRCC may develop multiple cutaneous and uterine leiomyomas, and they have an elevated risk of renal cell carcinoma. For each of these syndromes, a summary of the key syndromic features is provided, the underlying genetic events are discussed, and specific screening is recommended. Clin Cancer Res; 23(12); e76-e82. ©2017 AACRSee all articles in the online-only CCR Pediatric Oncology Series.

Baseline Surveillance in Li-Fraumeni Syndrome Using Whole-Body Magnetic Resonance Imaging: A Meta-analysis

Importance

Guidelines for clinical management in Li-Fraumeni syndrome, a multiple-organ cancer predisposition condition, are limited. Whole-body magnetic resonance imaging (WBMRI) may play a role in surveillance of this high-risk population.

Objective

To assess the clinical utility of WBMRI in germline TP53 mutation carriers at baseline.

Data Sources

Clinical and research surveillance cohorts were identified through the Li-Fraumeni Exploration Research Consortium.

Study Selection

Cohorts that incorporated WBMRI for individuals with germline TP53 mutations from January 1, 2004, through October 1, 2016, were included.

Data Extraction and Synthesis

Data were extracted by investigators from each cohort independently and synthesized by 2 investigators. Random-effects meta-analysis methods were used to estimate proportions.

Main Outcomes and Measures

The proportions of participants at baseline in whom a lesion was detected that required follow-up and in whom a new primary malignant neoplasm was detected.

Results

A total of 578 participants (376 female [65.1%] and 202 male [34.9%]; mean [SD] age, 33.2 [17.1] years) from 13 cohorts in 6 countries were included in the analysis. Two hundred twenty-five lesions requiring clinical follow-up were detected by WBMRI in 173 participants. Sixty-one lesions were diagnosed in 54 individuals as benign or malignant neoplasms. Overall, 42 cancers were identified in 39 individuals, with 35 new localized cancers treated with curative intent. The overall estimated detection rate for new, localized primary cancers was 7% (95% CI, 5%-9%).

Conclusions and Relevance

These data suggest clinical utility of baseline WBMRI in TP53 germline mutation carriers and may form an integral part of baseline clinical risk management in this high-risk population.

Exploratory analysis of ERCC2 DNA methylation in survival among pediatric medulloblastoma patients

AIM

Medulloblastoma is the most frequent malignant pediatric brain tumor. While survival rates have improved due to multimodal treatment including cisplatin-based chemotherapy, there are few prognostic factors for adverse treatment outcomes. Notably, genes involved in the nucleotide excision repair pathway, including ERCC2, have been implicated in cisplatin sensitivity in other cancers. Therefore, this study evaluated the role of ERCC2 DNA methylation profiles on pediatric medulloblastoma survival.

METHODS

The study population included 71 medulloblastoma patients (age <18years at diagnosis) and recruited from Texas Children's Cancer Center between 2004 and 2009. DNA methylation profiles were generated from peripheral blood samples using the Illumina Infinium Human Methylation 450 Beadchip. Sixteen ERCC2-associated CpG sites were evaluated in this analysis. Multivariable regression models were used to determine the adjusted association between DNA methylation and survival. Cox regression and Kaplan-Meier curves were used to compare 5-year overall survival between hyper- and hypo-methylation at each CpG site.

RESULTS

In total, 12.7% (n=9) of the patient population died within five years of diagnosis. In our population, methylation of the cg02257300 probe (Hazard Ratio=9.33; 95% Confidence Interval: 1.17-74.64) was associated with death (log-rank p=0.01). This association remained suggestive after correcting for multiple comparisons (FDR p<0.2). No other ERCC2-associated CpG site was associated with survival in this population of pediatric medulloblastoma patients.

CONCLUSION

These findings provide the first evidence that DNA methylation within the promoter region of the ERCC2 gene may be associated with survival in pediatric medulloblastoma. If confirmed in future studies, this information may lead to improved risk stratification or promote the development of novel, targeted therapeutics.

Abstract 5576: MnSOD polymorphism is associated with ototoxicity in pediatric medulloblastoma patients

Purpose: The SOD2 gene encodes manganese superoxide dismutase (MnSOD) and is critical for superoxide anion detoxification. Variants in SOD2 have been associated with noise-induced hearing loss, and animal models suggest MnSOD expression is up-regulated in the cochlea after treatment with platinum-based chemotherapeutic agents. Therefore, we examined the role of SOD2 variants on ototoxicity among cisplatin-treated childhood medulloblastoma patients.

Methods: Peripheral blood samples were obtained from 100 patients treated for pediatric medulloblastoma or supratentorial primitive neuroectodermal tumor at Texas Children's Cancer Center or MD Anderson Cancer Center between 1982 and 2009. Demographic, clinical, and treatment information was abstracted from patient medical records. A diagnosis of ototoxicity was assigned to patients whose medical records indicated they had received cisplatin chemotherapy and required the use of a hearing aid ≥1 year following the completion of primary therapy. DNA was genotyped on the Illumina HumanOmni-1 Quad BeadChip (San Diego, CA). A linkage disequilibrium-based single nucleotide polymorphism (SNP) selection strategy was used to identify a minimal set of informative common variants (minor allele frequency ≥5%). The association between each SNP and ototoxicity was assessed using multivariable logistic regression, assuming a log-additive model. Adjusted models included confounders (age at diagnosis, gender, craniospinal radiotherapy dose, cisplatin dose, amifostine therapy, and ethnicity) selected using a change in estimate approach.

Results: Study participants were primarily male (73.2%) and non-Hispanic white (42.3%) with a mean age at diagnosis of 7.3 years. Of the 71 eligible patients with available information, 26 (36.6%) suffered from cisplatin-related ototoxicity. Five SOD2 variants (rs7855, rs5746151, rs5746136, rs2758331, rs4880) identified by the LD-based selection strategy were available in the genotyped data. After correcting for multiple comparisons, the C allele of the rs4880 variant was significantly associated with ototoxicity (OR = 3.00; 95% CI: 1.32-6.82) in adjusted models.

Conclusions: In this study, the SOD2 rs4880 variant was associated with ototoxicity. The rs4880 T&gt;C substitution results in a Val&gt;Ala amino acid change at position 16 of the MnSOD mitochondrial targeting sequence. Specifically, the Ala-variant, which has been associated with increased MnSOD activity, was associated with hearing damage in this study. Platinum-based therapies increase the expression of MnSOD, which may result in an abundance of hydrogen peroxide, a reactive oxygen species. Therefore oxidative stress may be an important mechanism in therapy-related cochlear damage. Characterizing genetic predictors of ototoxicity susceptibility may aid in prevention strategies and potentially identify novel antioxidant therapeutic targets.

Citation Format: Austin L. Brown, Philip J. Lupo, Mehmet F. Okcu, Ching C. Lau, Surya P. Rednam, Michael E. Scheurer. MnSOD polymorphism is associated with ototoxicity in pediatric medulloblastoma patients. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5576. doi:10.1158/1538-7445.AM2015-5576

Germ-line and somatic DICER1 mutations in pineoblastoma

Germ-line RB-1 mutations predispose to pineoblastoma (PinB), but other predisposing genetic factors are not well established. We recently identified a germ-line DICER1 mutation in a child with a PinB. This was accompanied by loss of heterozygosity (LOH) of the wild-type allele within the tumour. We set out to establish the prevalence of DICER1 mutations in an opportunistically ascertained series of PinBs. Twenty-one PinB cases were studied: Eighteen cases had not undergone previous testing for DICER1 mutations; three patients were known carriers of germ-line DICER1 mutations. The eighteen PinBs were sequenced by Sanger and/or Fluidigm-based next-generation sequencing to identify DICER1 mutations in blood gDNA and/or tumour gDNA. Testing for somatic DICER1 mutations was also conducted on one case with a known germ-line DICER1 mutation. From the eighteen PinBs, we identified four deleterious DICER1 mutations, three of which were germ line in origin, and one for which a germ line versus somatic origin could not be determined; in all four, the second allele was also inactivated leading to complete loss of DICER1 protein. No somatic DICER1 RNase IIIb mutations were identified. One PinB arising in a germ-line DICER1 mutation carrier was found to have LOH. This study suggests that germ-line DICER1 mutations make a clinically significant contribution to PinB, establishing DICER1 as an important susceptibility gene for PinB and demonstrates PinB to be a manifestation of a germ-line DICER1 mutation. The means by which the second allele is inactivated may differ from other DICER1-related tumours.

USP11 negatively regulates TNFalpha-induced NF-kappaB activation by targeting on IkappaBalpha

IkappaBalpha serves as a central anchoring molecule in the sequestration of NF-kappaB transcription factor in the cytoplasm. Ubiquitination-mediated IkappaBalpha degradation immediately precedes and is required for NF-kappaB nuclear translocation and activation. However, the precise mechanism for the deubiquitination of IkappaBalpha is still not fully understood. Using a proteomic approach, we have identified Ubiquitin Specific Peptidase 11 (USP11) as an IkappaBalpha associated deubiquitinase. Overexpression of USP11 inhibits IkappaBalpha ubiquitination. Recombinant USP11 catalyzes deubiquitination of IkappaBalpha in vitro. Moreover, knockdown of USP11 expression enhances TNFalpha-induced IkappaBalpha ubiquitination and NF-kappaB activation. These data demonstrate that USP11 plays an important role in the downregulation of TNFalpha-mediated NF-kappaB activation through modulating IkappaBalpha stability. In addition, overexpression of a catalytically inactive USP11 mutant partially inhibits TNFalpha- and IKKbeta-induced NF-kappaB activation, suggesting that USP11 also exerts a non-catalytic function in its negative regulation of TNFalpha-mediated NF-kappaB activation. Thus, IkappaBalpha ubiquitination and deubiquitination processes function as a Yin-Yang regulatory mechanism on TNFalpha-induced NF-kappaB activation.