Molecular classification of the pediatric ependymomas

Author(s)

Graziella Ribeiro de Sousa

• Document type: Master's Dissertation
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina de Ribeirão Preto (PCARP/BC)
• Defense date: 2018-08-29

Examining board members

Luiz Gonzaga Tone; Andréia Machado Leopoldino; Elvis Terci Valera

• Advisor: Luiz Gonzaga Tone

Abstract

Introduction: Ependymomas are rare glial cell-derived tumors and comprise the third most frequent central nervous system tumor in childhood. Despite the therapeutic advances, about 50% of patients develop local recurrence and 40% of patients go to death. One of the causes of the failure of the therapies is the high tumor heterogeneity and the inconsistency of the histological diagnosis. In 2015, the molecular characterization of ependymomas was published for the first time, and nine tumor subgroups with distinct clinical, demographic and molecular profiles were described. Aim: To establish and standardize molecular classification in pediatric ependymoma samples and to correlate the classification with clinical data of the patients. Methods: We studied 65 cases of ependymomas, diagnosed between 2001 and 2016, from the Clinics Hospital of the Medical School of Ribeirão Preto and São Paulo and the Boldrini Children\'s Center-Campinas. Twenty-six cases were supratentorial ependymomas, classified based on the presence of gene fusions C11orf95- RELA, YAP1-MAMLD1 and YAP1-FAM118B using RT-PCR followed by Sanger sequencing. Thirty-nine posterior fossa cases were classified into Groups A, B or non A and B through the protein and gene expression profile of the markers: LAMA2, NELL2 and TNC using immunohistochemistry and quantitative real-time PCR, respectively. Results: Among the supratentorial ependymomas, three primary samples and five relapsed samples with RELA fusion, mean age of 7 years (range of 2.6-13.7 years), male predominance, and degree of complete surgical resection were identified. The YAP1-MAMLD1 fusion was identified in four cases, diagnosed in younger children, mean age 0.9 years (range of 0.75-2 years). In addition, a variant case was found in supratentorial ependymoma, called fusion C11orf95- LOC-RELA. Twenty-six primary samples and seven recurrences suggestive of Group A (LAMA2 + / NELL2-) and six non-A and non-B Group samples (LAMA2 + / NELL2 + and LAMA2 - / NELL2-). Among the patients considered Group A, 90% (24/28) presented positive staining for TNC, indicating that tumors had a worse prognosis. The gene expression of LAMA2 and NELL2 presented negative correlation and the TNC and LAMA2 genes had a positive correlation, p <0.01 and p <0.05, respectively. In the group A posterior fossa ependymoma, patients submitted to complete and incomplete surgical presented a significant difference in overall survival (5 years) of 71.2% ± 14.5% versus 21.4% ± 17.8%, p <0 , 01 and in SLE (2 years) 63.5% ± 14.8% versus 25% ± 15.3%, p <0.001. Conclusions: According to the results obtained, it was possible to establish the molecular classification in a Brazilian cohort, following the standards described in the literature. Data generated from this standardization will be of fundamental importance for the improvement of tumor stratification, contributing both to the determination of subgroup-specific therapeutic strategies and to the search for new therapeutic targets. (AU)

• FAPESP's process: 16/23972-6 - Molecular classification of pediatric ependymomas
• Grantee: Graziella Ribeiro de Sousa
• Support Opportunities: Scholarships in Brazil - Master