Down-regulated FOXO1 in Refractory/relapse Childhood B-cell Acute Lymphoblastic Leukemia

Abstract Background Refractory/relapsed acute lymphoblastic leukemia (RR-ALL) remains to be a leading cause of treatment failure and subsequent death. Forkhead box O1 (FOXO1) belongs to the forkhead family of transcription factors, its specific role in RR-ALL has not yet been determined in B-cell ALL (B-ALL). The purpose of this study was to investigate the expression and prognostic value in ALL. Methods RNA sequencing was applied to an ALL case with induction failure to identify the causal events. The transcription activity was examined with luciferase reporter assay. FOXO1 mRNA expression level was examined using real-time quantitative PCR. Association analysis was performed to correlate FOXO1 transcription with childhood B-ALL prognosis and relapse. Results In this ALL case with induction failure, we successfully identified a novel MEIS1-FOXO1 fusion gene. The transcription activity of MEIS1-FOXO1 was significantly abolished as compared to wild-type FOXO1. Low FOXO1 expression level was strongly associate with unfavorable subtype, MRD positivity and relapse. Conclusions FOXO1 loss of function associates with ALL high-risk stratification and relapse, which might be due to drug resistance.