Venetoclax Enhances The Antileukemic Activity Of CRM1 Inhibitors Against Acute Myeloid Leukemia By Enhancing DNA Damage

Acute myeloid leukemia(AML)is a highly heterogeneous hematologic malignancy,representing about 70% of adult acute leukemias.AML is uncontrolled proliferation of immature blood precursor cells at an arrested stage of differentiation.AML cells infiltrate into non-hematopoietic tissues and organs and interfere with the function of normal hematopoietic cells.To date,the cytarabine and daunorubicin based "7+3" chemotherapy remains the standard of care for the treatment of AML.Although most patients can achieve complete remission after chemotherapy,the relapse rate of AML is very high.Further,patients with relapsed AML generally do not respond to chemotherapy and may have other medical complications.The 5-year overall survival rate of adult patients with AML is only 26%,and less than 10% for those over 60 years old.Therefore,there is an urgent need of new therapies to improve the survival rate and quality of life of patients with AML.Exportin 1(XPO1),also known as chromosome region maintenance 1(CRM1),is a member of the Karyopherin family.CRM1 is responsible for the nuclear export of many tumor suppressors,growth regulators and other substrates.CRM1 has been found to be overexpressed in a variety of solid tumors and hematological malignancies and its overexpression is associated with poor prognosis.KPT-330(Selinexor)and KPT-8602(Eltanexor)are newly developed oral selective CRM1 inhibitors that can selectively target cancer cells,demonstrating great potential for the treatment of cancer.KPT-330 in combination with dexamethasone has been approved by the U.S.Food and Drug Administration(FDA)for the treatment of recurrent or refractory multiple myeloma.Venetoclax(ABT-199),a potent selective inhibitor of Bcl-2,has been approved by the U.S.FDA for the treatment of AML.A previous study from our lab demonstrated synergistic antileukemic interactions between KPT-330 and Venetoclax in preclinical models of AML which was partially meditated by Mcl-1.Therefore,the underlying molecular mechanism needs to be further elucidated.Studies from our lab also demostrated that Venetoclax can enhance the antileukemic activity of DNA damaging drugs via enhancing DNA damage induced by these agents,leading to synergistic antileukemic activity against AML.It has been reported that KPT-330 can induce DNA damage in cancer cells.Thus,we hypothesized that Venetoclax can enhance DNA damage induced by CRM1 inhibitors,resulting in synergistic antileukemic activity against AML.To test this hypothesis,we first investigated the effects of KPT-330 and KPT-8602 on DNA damage/repair-related proteins in AML cells.The results showed that CRM1 inhibitors down-regulated CHK1,WEE1,RAD51,RRM2 and c-Myc,accompanied by DNA damage and apoptosis.Additional studies revealed that Venetoclax could enhance DNA damage induced by the CRM1 inhibitors through inhibition of DNA damage repair,leading to accumulation of DNA damage and eventually apoptosis.This study further establishes the molecular mechanism underlying the synergistic antileukemic activity of Venetoclax and CRM1 inhibitors,and provides both theoretical and experimental support of the clinical evaluation of this promising combination therapy for the treatment of AML.