HDAC I/IIb selective inhibitor Purinostat Mesylate combined with GLS1 inhibition effectively eliminates CML stem cells

Purinostat Mesylate(PM)is a novel highly selective and active HDAC I/IIb inhibitor,and the injectable formulation of PM(PMF)based on the compound prescription containing cyclodextrin completely can overcome PM’s poor solubility and improves its stability and pharmacokinetic properties.Here,we showed that PM effectively repressed the survival of Ph+leukemia cells and CD34+leukemia cells from CML patients in vitro.In vivo studies demonstrated that PMF significantly prevented BCR-ABL(T315I)induced CML progression by restraining leukemia stem cells(LSCs),which are insensitive to chemotherapy and responsible for CML relapse.Mechanism studies revealed that targeting HDAC I/IIb repressed several important factors for LSCs survival including c-Myc,β-Catenin,E2f,Ezh2,Alox5,and mTOR,as well as interrupted some critical biologic processes.Additionally,PMF increased glutamate metabolism in LSCs by increasing GLS1.The combination of PMF and glutaminase inhibitor BPTES synergistically eradicated LSCs by altering multiple key proteins and signaling pathways which are critical for LSC survival and self-renewal.Overall,our findings represent a new therapeutic strategy for eliminating LSCs by targeting HDAC I/IIb and glutaminolysis,which potentially provides a guidance for PMF clinical trials in the future for TKI resistance CML patients.

TSPAN32 suppresses chronic myeloid leukemia pathogenesis and progression by stabilizing PTEN

We report herein that TSPAN32 is a key node factor for Philadelphia (Ph+) leukemia pathogenesis. We found that TSPAN32expression was repressed by BCR-ABL and ectopic TSPAN32 expression upon Imatinib treatment inhibited the proliferation of Ph+cell lines. Tspan32 overexpression significantly prevented BCR-ABL induced leukemia progression in a murine model and impairedleukemia stem cell (LSC) proliferation. LSCs represent an obstacle for chronic myeloid leukemia (CML) elimination, which continuallyreplenish leukemia cells and are associated with disease relapse. Therefore, the identification of essential targets that contribute tothe survival and self-renewal of LSCs is important for novel curative CML. Mechanistically, TSPAN32 was shown to interact withPTEN, increased its protein level and caused a reduction in PI3K-AKT signaling activity. We also found that TSPAN32 was repressedby BCR-ABL via the suppression of an important transcription factor, TAL1. Ectopic expression of TAL1 significantly increasedTSPAN32 mRNA and protein level, which indicated that BCR-ABL repressed TSPAN32 transcription by decreasing TAL1 expression.Overall, we identified a new signaling axis composed of “BCR-ABL-TAL1-TSPAN32-PTEN-PI3K-AKT”. Our findings furthercomplement the known mechanisms underlying the transformation potential of BCR-ABL in CML pathogenesis. This new signalingaxis also provides a potential means to target PI3K-AKT for CML treatment.