[The Application of RNA-Sequencing in Pediatric B-Cell Acute Lymphoblastic Leukemia]

To explore the molecular genetic characteristics of children with B-cell acute lymphoblastic leukemia (B-ALL) and the application value of RNA-sequencing (RNA-seq).

The clinical and laboratory examination data of newly diagnosed B-ALL children who were given treatment in the Department of Hematology, Children's Hospital of Chongqing Medical University from May 2015 to April 2020 were collected and analyzed. All children were confirmed by bone marrow morphology, histochemical staining and flow cytometry, and the karyotype analysis, FISH, RT-PCR and RNA-seq detection were conducted.

There were 71 males and 58 females with a median age of 50(8-190) months in 129 newly diagnosed children with B-ALL. The fusion gene was positive in 99 children (76.7%). A total of 86 leukemia related or possibly related gene mutations were detected, with a positive rate of 66.7%. There was no significant difference in the detection rates of ETV6-RUNX1, BCR-ABL1, TCF3-PBX1 and KMT2A rearrangements among FISH, RT-PCR and RNA-seq. Rare fusion genes were detected by RNA-seq, including 1 case of KMT2A-USP2, 4 cases of Ph-like related fusion genes, 5 cases of MEF2D rearrangement, 5 cases of PAX5 rearrangement, 3 cases of ZNF384 rearrangement, as well as several fusion genes whose significance were not clear or had not been reported in children with leukemia. Besides, children with ETV6-RUNX1 fusion gene had good response to induction of remission, while children with BCR-ABL1 and ZNF384 rearrangement had poor response, the remission rate of minimal residual disease was statistically significant compared with other types (P<0.05).

RNA-seq can not only detect known fusion genes, but also discover new or rare fusion genes and gene mutations. The application of RNA-seq has important guiding significance for risk classification and precise targeted therapy of pediatric B-ALL.