The Application Of RNA-sequencing In Pediatric B-cell Acute Lymphoblastic Leukemia And A Case Report Of An Infant Leukemia With KMT2A-USP2 And Literature Review

PARTⅠ THE APPLICATION OF RNA-SEQUENCING IN PEDIATRIC B-CELLACUTE LYMPHOBLASTIC LEUKEMIAObjective 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)in pediatric B-ALL.Methods The clinical and experimental data of newly diagnosed B-ALL children who were given treatment in the Hematology Department of Children 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.Results There were 72 males and 57 females with an average age of69 ± 47 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 of66.7%.There was no significant difference in the detection rates of ETV6-RUNX1,BCR-ABL1,TCF3-PBX1 and KMT2 A 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 fusion genes,5 cases of MEF2 D rearrangements,5 cases of PAX5 rearrangements,3 cases of ZNF384 rearrangements,and fusion genes whose significance were not clear or had not been reported in leukemia.Besides,ALL patients with ETV6-RUNX1 fusion had good response to induction of remission,while children with BCR-ABL1 and ZNF384 rearrangement had poor response to induction of remission(P < 0.05).Conclusion 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.PARTⅡ A CASE REPORT OF AN INFANT LEUKEMIA WITH KMT2A-USP2 AND LITERATURE REVIEWObjective To investigate the clinical and genetic characteristics of pediatric acute lymphoblastic leukemia(ALL)with KMT2A-USP2 fusion gene by the first case report in China and literature review,and to provide the reference for the diagnosis and treatment of infant leukemia.Methods The clinical data of an infant with ALL harboring KMT2A-USP2 fusion gene in Department of Hematology in August 2018 were collected and the literature was reviewed.Results FISH and Multiple-nested RT-PCR showed negative results.WES indicated pathogenic mutated genes of ATM,CASC5,LPP and PDGFRB,and RNA-sequencing detected the KMT2A-USP2 fusion gene.After diagnosis,the infant was treated with CCCG-ALL-2015 protocol,presenting a poor response to induction.Up to the follow-up time of the children,complete remission(CR)has been achieved for 25 months.Conclusion KMT2 A rearrangement is very common in infant leukemia.The next generation sequencing(NGS)technology should be carried out to detect rare KMT2 A rearrangement in infants with leukemia who showed negative KMT2 A rearrangement by conventional screening approaches.Meanwhile,chemotherapy intensity should be strengthened to achieve MRD remission,and allogeneic hematopoietic stem cell transplantation should be considered if possible.