The rapid spread of the coronavirus disease 2019 (COVID-19) pandemic has rapidly led to the establishment of social distancing measures on a global scale to try to protect the general population as well as patients. 1 An unprecedented wave of dedicated preclinical and clinical research projects has also been launched.

Data regarding coronavirus disease 2019 (COVID-19) description are still limited in pediatric oncology. The French society of pediatric oncology (SFCE) initiated a study to better describe COVID-19 in patients followed in French pediatric oncology and hematology wards. All patients diagnosed with COVID-19 and followed in a SFCE center were enrolled. Data from medical records were analyzed for all patients enrolled up to the end of May 2020. Data were available for 37 patients. Thirty-one were children under 18 years of age. Nineteen patients were female. Seventeen patients had a solid tumor, 16 had a hematological malignancy and four recently underwent hematopoietic stem cell transplantation (HSCT) for non-oncological conditions. Twenty-eight patients presented symptoms, most often with fever, cough, rhinorrhea and asthenia. Ground-glass opacities were the most frequent radiological finding with abnormalities mostly bilateral and peripherally distributed. Twenty-four patients received chemotherapy a month prior to COVID-19 diagnosis. Most patients did not require hospitalization. Three patients required oxygen at the time of diagnosis. In total, five patients were admitted in an intensive care unit because of COVID-19 and one died from the disease. Children and young adults treated for a cancer and/or with a HSCT may be at risk for severe COVID-19 and should be closely monitored.

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Bouttefroy, Nicolas André, and Virginie Gandemer participated in the study and data collection, and read and approved the manuscript as submitted.

Background B Cell Precursor Acute Lymphoblastic Leukemia (BCP-ALL) is the most common pediatric cancer. Identifying key players involved in proliferation of BCP-ALL cells is crucial to propose new therapeutic targets. Runt Related Transcription Factor 1 (RUNX1) and Core-Binding Factor Runt Domain Alpha Subunit 2 Translocated To 3 (CBFA2T3, ETO2, MTG16) are master regulators of hematopoiesis and are implicated in leukemia. Methods We worked with BCP-ALL mononuclear bone marrow patients’ cells and BCP-ALL cell lines, and performed Chromatin Immunoprecipitations followed by Sequencing (ChIP-Seq), co-immunoprecipitations (co-IP), proximity ligation assays (PLA), luciferase reporter assays and mouse xenograft models. Results We demonstrated that CBFA2T3 transcript levels correlate with RUNX1 expression in the pediatric t(12;21) ETV6-RUNX1 BCP-ALL. By ChIP-Seq in BCP-ALL patients’ cells and cell lines, we found that RUNX1 is recruited on its promoter and on an enhancer of CBFA2T3 located − 2 kb upstream CBFA2T3 promoter and that, subsequently, the transcription factor RUNX1 drives both RUNX1 and CBFA2T3 expression. We demonstrated that, mechanistically, RUNX1 and CBFA2T3 can be part of the same complex allowing CBFA2T3 to strongly potentiate the activity of the transcription factor RUNX1. Finally, we characterized a CBFA2T3-mimicking peptide that inhibits the interaction between RUNX1 and CBFA2T3, abrogating the activity of this transcription complex and reducing BCP-ALL lymphoblast proliferation. Conclusions Altogether, our findings reveal a novel and important activation loop between the transcription regulator CBFA2T3 and the transcription factor RUNX1 that promotes BCP-ALL proliferation, supporting the development of an innovative therapeutic approach based on the NHR2 subdomain of CBFA2T3 protein.

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Highlights ETV6-RUNX1 and RUNX1 directly promote RAG1 expression. ETV6-RUNX1 and RUNX1 preferentially bind to the −1200 bp enhancer of RAG1 and the −80 bp promoter of RAG1 gene respectively, and compete for these bindings. ETV6-RUNX1 and RUNX1 induce an excessive RAG recombinase activity. ETV6-RUNX1 participates directly in two events of the multi-hit ALL leukemogenesis: as an initiating event and as an activator of RAG1 expression.

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