CSF3R Gene Mutations In Myeloid Malignancy Of Childhood
Authors: Sano Hitoshi , Ohki Kentaro , Park Myoung-ja , Hara Yusuke , Shiba Norio , Tomizawa Daisuke , Taga Takashi , Saito Akiko Moriya , Fujimoto Junichiro , Tawa Akio , Horibe Keizo , Adachi Souichi , Hayashi Yasuhide 
Published: October 2019

Abstract

Background
Granulocyte colony-stimulating factor (G-CSF; CSF3) and its receptor (G-CSFR; CSF3R) control neutrophil production under basal circumstances and during episodes of bacterial infections. Mutations in a region of the CSF3R gene coding for the intracytoplasmic domain of the G-CSFR have been discovered in patients with severe congenital neutropenia (CN) and were initially suggested to be the cause of CN. Mutations in CSF3R gene are regarded as an early marker of malignant transformation in CN. Common genetic abnormalities like acquired clonal cytogenetic alterations or activating RAS mutations have also been observed to be associated with CN-related myelodysplastic syndrome(MDS)/leukemia. In adults, a frequency of CSF3R mutation was common (59%) in patients with chronic neutrophilic leukemia (CNL) and atypical (BCR-ABL1–negative) chronic myeloid leukemia (CML), whereas that was low (1%) in patients with de novo acute myeloid leukemia (AML). Sequence variants that were identified included membrane proximal mutations and a number of different frameshift or nonsense mutations that truncate the cytoplasmic tail of CSF3R. These mutations segregate within two distinct regions of CSF3R and lead to preferential downstream kinase signaling through SRC family-TNK2 or JAK kinases and differential sensitivity to kinase inhibitors. However, little is known about the incidence and prognostic values of CSF3R mutations in pediatric myeloid malignancies.

Methods
CSF3R mutations (exon14 and 17) in a total of 376 samples of pediatric de novo AML, 40 samples of juvenile myelomonocytic leukemia (JMML), and 20 samples of MDS were analyzed from gDNA or cDNA extracted from diagnostic bone marrow samples using direct sequencing. Moreover, we assessed whether CSF3R mutations overlap with known gene abnormalities, such as FLT3, c-KIT, NPM1 and SETBP-1. Mutational analyses of FLT3, c-KIT, NPM1 and SETBP-1 were also performed in AML samples.

Results
We identified a CSF3R mutation in 5 of 376 patients (1.3%) with AML, 2 frameshift mutations (E788X) and 3 missense mutations (L777F and T618I). The patients with 3 (L777F and E788X) of these 5 mutations had complex chromosomal abnormalities involved in chromosome 8 and 21 (t(8;21) and ins(21;8); AML1/ETO). The other 2 patients with missense mutations (T618I) had normal karyotype. They presented with a relatively high WBC counts of 100.6×10*9/l and 159.5×10*9/l. Although 2 of 5 these patients relapsed, all of them were salvaged successfully. Two of 5 had c-KIT mutations, while none of them had FLT3, NPM1, and SETBP-1 mutations. No mutations of CSF3R in JMML and MDS patients were found.

Conclusions
To our knowledge, this is the first report to describe the CSF3R mutation in a pediatric de novo AML patient. In our study, CSF3R mutation is detected in 1.3% in childhood de novo AML, which suggests the involvements of CSF3R mutations in the pathogenesis of pediatric de novo AML, JMML and MDS are extremely rare compared with those in SCN and adult CNL and atypical CML cases. Since CSF3R mutation is rare event, the prognostic values of CSF3R mutations in de novo AML are still unclear. Further data accumulation is necessary.

Disclosures:
No relevant conflicts of interest to declare.