Ybx1 is required for Survival of Leukemia Stem Cells and the Development of Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) is a myeloproliferative disorder derived from hematopoietic stem cells (HSCs) that harbor Philadelphia chromosome (Ph chromosome). Leukemia stem cells (LSCs) in CML are insensitive to TKIs treatment, and are responsible for disease relapse. However, the molecular mechanisms for LSCs survival remains elusive. Here we show that YBX1 plays an important role in regulating survival of CML LSCs. We find that YBX1 expression is significantly increased in CML cells. Using CML patient-derived cell lines and a BCR-ABL-induced CML mouse model, we confirm that YBX1 is required for survival maintenance of LSCs. Deletion of YBX1 impairs the propagation of CML through impairing cell cycle and inducing apoptosis of LSCs. Mechanistically, we find that YBX1 regulates expression of apoptosis-related genes, and YBX1 binds MYC and BCL2 transcripts. YBX1 loss decreases expression of MYC and BCL2 by accelerating their mRNA decay. In addition, restoration of MYC and BCL2 efficiently rescue the defects of YBX1-deficient CML cells. Overall, our findings reveal a critical role of YBX1 in maintaining survival of CML LSCs, which may provide a rationale for targeting YBX1 in CML treatment. RNAseq of WT and YBX1cKO LSCs