Novel MEIS1-FOXO1 Fusion Gene in a Case of Pediatric B-Cell Precursor Acute Lymphoblastic Leukemia

Abstract Background: Thanks to the total therapy and systemic basic-translation research, the overall survival rate in children with acute lymphoblastic leukemia (ALL) has dramatically improved to almost 90% over these past few decades. FOXO1 gene belongs to the forkhead family of transcription factors, which play roles in myogenic growth and differentiation. Translocation of FOXO1 with PAX3 has been reported in pediatric alveolar rhabdomyosarcoma. In B-cell precursor ALL, two cases with FOXO1 fusions have been identified already, while its function on ALL remains unknown. Here, we report a novel MEIS1-FOXO1 fusion gene in a case with B-ALL. Methods: Flowcytometery, karyotype, RT-PCR and fluorescence in were employed, MEIS1-FOXO1 was identified as novel fusion gene in a case of pediatric BCP-ALL. Using IL-3 dependent BaF3 cells as study model to test the leukemia transformation potential of MEIS1-FOXO1. Results: A novel MEIS1-FOXO1 fusion was identified in one cease of pediatric B-ALL. Panel next generation sequencing (NGS) showed that the leukemia clone had concurrent NRASG12D, TP53R273H, WHSC1E1099K, ABCC1R1166X, PHGR1H37P, HOXA3P219L and DSTP4606L somatic mutation. This patient was enrolled in CCCG-ALL2015 clinical trial (ChiCTR-IPR-14005706) and achieved completed remission and low minimal residual disease (MRD) level (MRD<0.01%) at day 19 from induction therapy. Functional study showed that MEIS1-FOXO1 fusion gene can potentiate BaF3 cells growth independent of IL3 supplement, as compared to those without MEIS1-FOXO1 fusion transduction. In the meanwhile, we have found that MEIS1-FOXO1 fusion gene can drive cells into S-phase with concurrent decreased G0/G1 phase, which might be its oncogenic role in leukemogenesis. Using qPCR methods, we have found that MEIS1-FOXO1 fusion gene altered the cell cycle related genes expression. Conclusions: Integrating the FOXO1-fusion reports, our data have added more evidence to underline the role of FOXO1 deregulation in the pathogenesis of acute lymphoblastic leukemia. Novel fusion of MEIS1-FOXO1 can potentiate B-ALL via cell cycle entry. Detailed mechanisms involved into the MEIS1-FOXO1 should be further investigated. Figure. Figure. Disclosures No relevant conflicts of interest to declare.