Synthetic Lethality Of Combined AT-101 With IDA In Acute Myeloid Leukemia Via Blockage Of DNA Repair And Activation Of Intrinsic Apoptotic Pathway

Acute myeloid leukemia(AML)is a heterogeneous hematological malignancy characterized by uncontrolled clonal expansion of hematopoietic progenitor cells.Despite the continuous optimization of therapeutic strategies,which led to a 65%～75%complete remission rate in adult AML patients,most patients will eventually relapse with a poor prognosis.In additon,traditional high-dose chemotherapy with strong side effects and drug resistance significantly affected the survival time of AML patients and ultimately led to death.Currently,five-year survival rate of AML patients is only 27.4%.The development of new drugs is a costly and time-consuming process.Therefore,exploring new drug combination of existing clinical agents targeting different pathways to effectively eliminate leukemia cells have attracted great attention,which can enhance the efficacy and reduce the amount of medication,so as to reduce the side effects of traditional chemotherapy and improve the cure rate.,Idarubicin(IDA)is a novel anthracycline anti-leukemic drug that can intercalates DNA and inhibits DNA synthesis by interfering with the enzyme topoisomerase Ⅱ.It is a first line treatment of induction therapy for AML.AT-101,a pan-Bcl-2 inhibitor,exhibits high affinity to all major anti-apoptotic proteins and thus displays cytotoxic activity against diverse tumor types via the activation of mitochondrial apoptotic pathways.Our previous work has shown that AT-101 alone can safely and effectively kill AML cells in vitro.However,considering that AML is unlikely to be cured with monotherapy and Bcl-2 expression level is closely related to chemotherapy resistance,we wonder whether inhibition of anti-apoptotic Bcl-2 family members with AT-101 will synergistically enhance the anti-leukemic effects of idarubicin.It might represent an attractive and promising avenue strategy to reduce the dosage of harmful idarubicin and overcome resistance to conventional anti-tumor therapy.In this study,we used AML cell lines(KG-la and Kasumi-1)demonstrated that AT-101/IDA combined application can result in a synergetic anti-AML activity(proliferation inhibition and apoptosis induction)in vitro.Furthermore,it was confirmed that AT-101/IDA combination can target killing AML cells without involving normal cells in primary AML patient samples.Next,the anti-leukemia property of AT-101/IDA is further confirmed using PDX models generated from a refractory/relapsed AML patient carrying FLT3-ITD mutation,implying that AT-101/IDA treatment may benefit patients carrying FLT3-ITD mutation.Mechanistically,these events might attribute to the fact that IDA induces severe DNA damage in tumor cells,while AT-101 impairs the repair capacity of DNA damage and inhibits the expression of anti-apoptotic proteins,resulting in mitochondrial outer membrane permeabilization and activation of the executioner caspase-3,ultimately inducing apoptosis.In summary,this study has demonstrated that AT-101 in combination with IDA has a synergetic and selective anti-AML activity in vitro and in vivo against AML cells.Furthermore,these events are mechanistically associated with the disruption of DNA damage repair response as well as the activation of mitochondria apoptosis pathway.Thus,our study provides experimental and theoretical support for the development of a novel combinatorial approach in the treatment of AML patients.