U2AF1 mutation promotes tumorigenicity

Mutations in the U2 small nuclear RNA auxiliary factor 1 (U2AF1) gene are the common feature of a major subset in myelodysplastic syndromes (MDS). However, the genetic landscape and molecular pathogenesis of oncogenic U2AF1S34F mutation in MDS are not totally understood. We performed comprehensive analysis for prognostic significance of U2AF1mutations in acute myeloid leukemia (AML) cohort based on The Cancer Genome Atlas (TCGA) database. Functional analysis of U2AF1S34Fmutation was performed in vitro. Differentially expressed genes (DEGs) and significantly enriched pathways were identified by RNA sequencing. The forkhead box protein O3a (FOXO3a) was investigated to mediate the function of U2AF1S34F mutation in cell models using lentivirus.

Chromatin immunoprecipitation, immunoblotting analyses, and immunofluorescence assays were also conducted. U2AF1 mutations were associated with poor prognosis in MDS and AML samples, which significantly inhibited cell proliferation and induced cellular apoptosis in cell models. Our data identified that U2AF1-mutant cell lines undergo FOXO3a-dependent apoptosis and NLRP3 inflammasome activation, which induces pyroptotic cell death. Particularly, an increase in the level of FOXO3a promoted the progression of MDS in association with restored autophagy program leading to NLRP3 inflammasome activation in response to U2AF1S34Fmutation.

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Fig: Mutations of U2AF1 in clinical MDS samples: A The patients carrying the U2AF1 mutations (n = 58) revealed lower peripheral blood cell counts compared with those without a U2AF1 mutation (n = 68). BRelative expression of U2AF1 from TCGA-seq dataset. No significant differences were found for U2AF1 gene expression between mutant and wild-type samples (p > 0.05). C Kaplan–Meier survival analysis indicated that patients with U2AF1mutations were significantly correlated with a shorter overall survival than those without the mutation (p < 0.05). Statistical significance in relative expression analysis was determined by log2(RPKM) test.

Based on the result that U2AF1S34F mutation promoted the transcriptional activity of Bim through upregulating FOXO3a with transactivation of cell cycle regulators p21Cip1 and p27Kip1, FOXO3a, a potentially cancer-associated transcription factor, was identified as the key molecule on which these pathways converge. Overall, our studies provide new insights that U2AF1S34F mutation functions the crucial roles in mediating MDS disease progression via FOXO3a activation, and demonstrate novel targets of U2AF1 mutations to the pathogenesis of MDS.

Zhu, Y., Song, D., Guo, J. et al. U2AF1 mutation promotes tumorigenicity through facilitating autophagy flux mediated by FOXO3a activation in myelodysplastic syndromes. Cell Death Dis 12,655 (2021). https://doi.org/10.1038/s41419-021-03573-3

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