Germinal and somatic genetic variants of NF1 in neuroblastoma: own experience and literature review

Abstract

Introduction. Neuroblastoma (NB) is the most common embryonic extracranial malignant neoplasm in children. The contribution of the NF1 gene to the development of NB is discussed in the literature, but there is no evidence of the pathogenetic role of NF1 gene aberrations in NB. According to various literature sources, the occurrence of pathogenic variants in the NF1 gene in the general cohort of patients with NB does not exceed 1–6 %.Materials and methods. The molecular genetic examination by next generation sequencing (NGS) was performed in 77 patients with NB during the period from April 2019 to July 2021 in the Laboratory of Molecular Oncology Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology, Immunology. The staging of patients was carried out within the framework of the international staging system, stratification into risk groups and therapy according to the protocol of the German Group for the study of NB GPOH NB-2004. International criteria of the response assessment system for patients with NB were used to assess the response to treatment. Calculations of event-free and overall survival by the Kaplan–Mayer method for the follow-up period up to 12.01.2022 were performed.Results and discussion. The cohort of patients included in the study was represented by patients with an initially unfavorable prognosis. Patients were divided into 3 groups: without pathogenic variants in genes belonging to the RAS-RAF-MEK pathway and TP53 – “RAS-/ TP53-” (n = 43), with clinically significant variants in the NF1 gene – “NF1+” (n = 12), clinically significant variants in the genes of RAS-RAF-MEK and TP53 pathway – “RAS+/TP53+” except NF1 (n = 22). The median age for the entire group of patients at the time of diagnosis was 41 months (0.1–173 months). Boys prevailed over girls with a ratio of 1.5:1. Patients with stage 4 of the disease according to the INSS classification prevailed – 81.8 % (63/77), high-risk groups according to the NB-2004 protocol – 77.9 % (60/77).In our study 13 clinically significant variants in NF1 were identified in 12 patients (15.6 %), of which 4 were germinal, 9 were somatic. The frequency of detection of pathogenic aberrations in the NF1 gene was much higher than the literature data, which can be associated with a selective cohort of studied patients with an unfavorable prognosis and patients with suspected hereditary genetic syndrome. The presentation of adverse events was observed in 83.3 % of patients, more often against the background of specific therapy (in 60 % of cases), which may be due to the rapid acquisition of NB chemoresistance, among other things. When comparing the three groups, it was shown that the frequency of objective responses to induction therapy was statistically significantly lower in the group of patients “NF1+”, when compared with other groups (p = 0.015; p = 0.024), which may also indicate the chemoresistance of NF1-aberrated NB. When analyzing survival there was no statistical difference between the compared groups.Conclusions. The data obtained by us do not allow us to consider the presence of genetic variants in NF1 separately as a prognostic factor, however, it can be assumed that a group of patients with an unfavorable prognosis may be enriched with cases with mutations in the NF1 gene. Refractory course of the disease/development of adverse events in the presence of genetic variants of NF1, causing the activation of the RASRAF- MEK signaling pathway, leads to the induction of tumor chemoresistance. The presence of clinical significance of aberrations in the NF1 gene does not lead to a statistically significant difference in prognosis when compared with patients with aberrations in other components of the RAS-RAF-MEK pathway, however, longer catamnestic follow-up of patients is necessary.Currently, there are no effective drugs for the treatment of NF1-associated NB in clinical practice that requires further study of the mechanisms of chemoresistance development in such patients. Understanding the molecular and genetic features of the course of NF1-associated NB can become the basis for the development of personalized therapy in the future.