Protocolo Latino-Americano de Sarcoma de Ewing : um estudo sobre as características clínicas e patológicas dos pacientes

Introdução: O Sarcoma de Ewing (SE) e o Tumor Neuroectodérmico Periférico (PNET) são tumores pequenos, redondos, de células azuis da infância e adolescência, que apresentam translocação cromossômica EWS em 85% dos casos, e imuno-histoquímica com expressão de superfície glicoproteína CD99. O diagnóstico pode ser desafiador e requer um patologista experiente em tumores ósseos e malignidades pediátricas. Métodos: O estudo atual do Grupo Cooperativo Latino-Americano de Sarcoma foi projetado para determinar a eficácia e segurança de um regime de quimioterapia com intervalo comprimido e a incorporação de quimioterapia metronômica para pacientes com SE recém-diagnosticada. Os relatórios de patologia de todos os centros com painel de imuno-histoquímica e translocações EWS foram recuperados dos prontuários médicos retrospectivamente e são descritos juntamente com dados demográficos e dados prognósticos e de sobrevida. Resultados: Foram analisados 400 pacientes em 31 centros com laudos completos de patologia. A translocação EWS foi feita em 20% dos pacientes (87/400). A Argentina realizou confirmação genética em pelo menos 40% dos pacientes, enquanto centros no Brasil, Chile e Uruguai somente solicitam quando o diagnóstico diferencial é necessário. NKX2-2 foi realizado em 61 pacientes (15,25%) e foi positivo em 95% dos casos. 7,5% dos pacientes foram diagnosticados com PNET. Os marcadores de diferenciação muscular mais frequentes foram a desmina e a miogenina. A sinaptofisina parece ser o marcador neural mais frequente, juntamente com LCA/CD45 e TdT como marcadores linfóides. Marcadores diferenciais epiteliais não foram comumente solicitados, mas foram positivos em cerca de 10% dos casos. O KI67 foi analisado em menos de 20% dos pacientes e a maioria apresentou índice alto (>30%). A idade mediana ao diagnóstico foi de 10,72 anos (variação de 0,02 a 32,85 anos). Os membros inferiores foram o local de tumor primário mais frequente (28,3%), seguido de tórax (21,9%), pelve (16,8%). A taxa de resposta geral foi de 82,5% (RC 18,8%, PR 63,6%), enquanto 10 pacientes (3,3%) apresentaram doença progressiva (DP). A ressecção cirúrgica do tumor foi realizada em 160 (50,8%) pacientes, cirurgia em combinação com radioterapia em 71 (28%) pacientes e radioterapia isolada em 51 (21%) pacientes. A análise da resposta histológica à quimioterapia pré-operatória de acordo com os critérios do Índice de Necrose (NI) foi determinada em 123 pacientes, e a distribuição mostrou que 54,5% e 45,5% tinham NI 30%). The median age at diagnosis was 10.72 years (range 0.02 to 32.85 years). Lower limbs were the most frequent primary tumor site (28.3%), followed by chest (21.9%), pelvis (16.8%). Overall response rate was 82.5% (CR 18.8%, PR 63.6%), while 10 patients (3.3%) had progressive disease (PD). Surgical tumor resection was performed in 160 (50.8%) patients, surgery in combination with radiation in 71 (28%) patients, and radiation alone in 51 (21%) patients. Analysis of histological response to preoperative chemotherapy according to Necrosis Index (NI) criteria was determined in 123 patients, and the distribution showed that 54.5% and 45.5% had NI <99% and 100%, respectively.Conclusion: Implementation of a multi-institutional protocol was feasible and resulted in outcomes that are comparable to those of groups in high-income countries. Only a minority of patients perform molecular testing and broad panel immunohistochemistry due to limited resources. Further collaboration is underway to standardize pathological diagnosis and molecular testing

EHMT2/G9a as an epigenetic target in pediatric and adult brain tumors

Epigenetic mechanisms, including post-translational modifications of DNA and histones that influence chromatin structure, regulate gene expression during normal development and are also involved in carcinogenesis and cancer progression. The histone methyltransferase G9a (euchromatic histone lysine methyltransferase 2, EHMT2), which mostly mediates mono- and dimethylation by histone H3 lysine 9 (H3K9), influences gene expression involved in embryonic development and tissue differentiation. Overexpression of G9a has been observed in several cancer types, and different classes of G9a inhibitors have been developed as potential anticancer agents. Here, we review the emerging evidence suggesting the involvement of changes in G9a activity in brain tumors, namely glioblastoma (GBM), the main type of primary malignant brain cancer in adults, and medulloblastoma (MB), the most common type of malignant brain cancer in children. We also discuss the role of G9a in neuroblastoma (NB) and the drug development of G9a inhibitors

Gene expression changes associated with chemotherapy resistance in Ewing sarcoma cells

Ewing Sarcoma (ES) is a highly aggressive bone and soft tissue childhood cancer. The development of resistance to chemotherapy is common and remains the main cause of treatment failure. We herein evaluated the expression of genes associated with chemotherapy resistance in ES cell lines. A set of genes (CCAR1, TUBA1A, POLDIP2, SMARCA4 and SMARCB1) was data-mined for resistance against doxorubicin and vincristine, which are the standard drugs used in the treatment of patients with ES. The expression of each gene in SK-ES-1 ES cells was reported before and after exposure to a drug resistance-inducing protocol. There was a significant downregulation of CCAR1 and TUBA1A in doxorubicin-resistant cells, with low expression of TUBA1A in vincristine-resistant cells. By contrast, POLDIP2 was significantly upregulated in cells resistant to either drug, and the expression of the SMARCB1 and SMARCA4 genes was upregulated in doxorubicin-resistant cells. These findings indicate that resistance to specific chemotherapeutic agents was accompanied by differential changes in gene expression in ES tumors

Reverse engineering of Ewing Sarcoma regulatory network uncovers PAX7 and RUNX3 as master regulators associated with good prognosis

Ewing Sarcoma (ES) is a rare malignant tumor occurring most frequently in adolescents and young adults. The ES hallmark is a chromosomal translocation between the chromosomes 11 and 22 that results in an aberrant transcription factor (TF) through the fusion of genes from the FET and ETS families, commonly EWSR1 and FLI1. The regulatory mechanisms behind the ES transcriptional alterations remain poorly understood. Here, we reconstruct the ES regulatory network using public available transcriptional data. Seven TFs were identified as potential MRs and clustered into two groups: one composed by PAX7 and RUNX3, and another composed by ARNT2, CREB3L1, GLI3, MEF2C, and PBX3. The MRs within each cluster act as reciprocal agonists regarding the regulation of shared genes, regulon activity, and implications in clinical outcome, while the clusters counteract each other. The regulons of all the seven MRs were differentially methylated. PAX7 and RUNX3 regulon activity were associated with good prognosis while ARNT2, CREB3L1, GLI3, and PBX3 were associated with bad prognosis. PAX7 and RUNX3 appear as highly expressed in ES biopsies and ES cell lines. This work contributes to the understanding of the ES regulome, identifying candidate MRs, analyzing their methilome and pointing to potential prognostic factors