OBJECTIVE To investigate the effect and potential mechanism of toosendanin in enhancing the antileukemic activity of cytosine arabinoside against acute myeloid leukemia （AML） based on the mammalian target of rapamycin complex 1 （mTORC1） signaling pathway.METHODS Female NSG immunodeficient mice were used to establish an AML model via a single γ-ray irradiation followed by a single tail-vein injection of a U937 cell suspension. The effects of cytosine arabinoside （2.5 mg/kg）， toosendanin （1.0 mg/kg）， and cytosine arabinoside+toosendanin （2.5 mg/kg+1.0 mg/kg） on body weight， survival time， peripheral blood routine indicators， histopathological morphology， and the expressions of autophagy-related proteins were explored. Using U937 cells as the subject， the effects of cytosine arabinoside （1 μmol/L）， toosendanin （160 nmol/L）， and cytosine arabinoside+toosendanin （1 μmol/L+160 nmol/L） on the expressions of autophagy-related proteins， mTORC1 signaling pathway-related proteins and mRNAs were investigated. The targeting relationship between toosendanin and the selective autophagy ligand 1 （also known as p62） was validated， and the Gene Ontology （GO） and Kyoto Encyclopedia of Genes and Genomes （KEGG） enrichment analyses， as well as molecular docking， were performed. A p62 -knockdown U937 stable cell line was constructed， and the underlying mechanism of toosendanin-induced sensitization was verified.RESULTS Animal experiments confirmed that the combination of toosendanin and cytosine arabinoside significantly improved body weight， survival time and peripheral blood routine indicators in AML mice （ P ＜0.05）， alleviated pathological changes such as leukemic cell infiltration and focal necrosis in bone marrow， liver， and spleen tissues， and modulated the expressions of autophagy-related proteins. Cell experiments confirmed that toosendanin could reverse cytosine arabinoside-induced activation of the autophagy cascade （manifested by downregulation of the protein expressions of microtubule-associated protein 1 light chain 3B and Beclin-1， upregulation the protein expression of p62）， and might inhibit the expression of the downstream Unc-51-like autophagy activating kinase 1 （ULK1） complex （including ULK1， ULK2， autophagy-related protein 13， and FAK family interacting protein of 200 kDa） by activating the mTORC1 signaling pathway （ P ＜0.05）. The sensitizing effect of toosendanin was associated with the inhibition of autophagy and the regulation of the mTORC1 signaling pathway； it could stably bind to p62 via hydrophobic interactions. Mechanism verification experiments indicated that upon p62 knockdown， toosendanin was no longer able to activate the mTORC1 signaling pathway or inhibit autophagy.CONCLUSIONS Toosendanin may enhance chemo-sensitivity of AML cells to cytosine arabinoside by directly targeting the p62 protein， which subsequently activates the mTORC1 signaling pathway， and thereby suppresses cytosine arabinoside-induced protective autophagy.

Objectives To explore the differences in therapeutic efficacy between decitabine combined with low dose HAG(D+ HAG)and CAG in elderly patients with acute myeloid leukemia (AML).Methods Totally 32 elderly patients with AML in our department from July 2012 to July 2015 were retrospectively analyzed.15 patients were on a therapy of decitabine combined with low dose HAG,and 17 patients with CAG.Efficacy and side effects were compared between the two groups.Results In(D+HAG)versus CAG groups,the complete remission(CR)was 10 cases(66.7％)vs.6 cases (35.3 ％),partial remission(PR) was 2 cases (13.3％) vs.1 case(5.9 ％),non-remission(NR) was 3 cases(20％)vs.10 cases(58.8％),and the total efficacy rate(CR+PR)was 80％vs.41.2％ (P＜0.05).The side effects in two groups mainly included bone marrow depression,respiratory tract infection,gastrointestinal reaction,which were all alleviated after symptomatic treatments.The incidence rate of side effects had no statistical difference (P ＞ 0.05).Conclusions The treatment of decitabine combined with low dose of HAG is prior to CAG,and the side effects are all tolerated.So decitabine combined with low dose of HAG can be served as the first-line therapy for elderly AML patients.