Transfer Of IGF2BP3 Through Ara-C-induced Apoptotic Bodies Promotes Survival Of Recipient Cells

The antipyrimidine chemotherapy drug cytarabine(Ara-C)is one of the most common chemotherapy drugs in the treatment of acute myeloid leukemia(AML)and myelodysplasia syndrome(MDS).Cytarabine is often used in combination with anthracyclines,and the clinical scheme "3 + 7" refers to the combination of 3 days of anthracycline plus 7 days of cytarabine.Considerable progress has been made in development of new treatments for MDS/AML patients,but drug resistance remains a major clinical problem.Apoptotic bodies(ABs),produced by late apoptotic cells,can enclose bioactive components that affect cell-cell interactions and disease progression.They contain a variety of bioactive molecules,including DNAs,RNAs,and proteins,which are involved in communication with surrounding cells.In this study,the sensitivity of four MDS/AML cell lines,KG1 a,OCI-AML3,SKM1 and ML-1,to cytarabine was detected.KG1 a and OCI-AML3 were selected as donor cells.The ABs from donor cells produced by serum starvation vs.cytosine arabinoside(Ara-C)treatment of malignant hematopoietic cells were obtained.Then recipient cells were treated with two types of ABs.The functional differences of recipient cells such as proliferation,cell cycle and apoptosis were examined.It was found that ABs produced by Ara-C-treated cells enhanced proliferation and anti-apoptosis capacity of recipient cells.We used a proteomic approach to identify 1577 proteins that were differentially expressed in above two types of ABs.Treatment with chemotherapeutic agents significantly increased content of IGF2BP3,a potential oncoprotein,in ABs from Ara-C-treated cells.We observed that IGF2BP3 carried by ABs was phagocytosed by recipient cells.Following phagocytosis,IGF2BP3 promoted expression of oncoprotein c-Myc,which in turn activated PI3K-AKT and P42-44 MAPK signaling pathways.Activation of these pathways further promoted cell proliferation,anti-apoptotic capacity,and drug resistance of recipient cells.Treatment with JQ-1,a bromine terminal inhibitor of IGF2BP3,reversed above phenomenon induced by IGF2BP3.Mouse model in vivo confirmed ABs produced by Ara-C-treated cells promoted the tumorigenesis of SKM1 cells in mice by activating the expression of PI3K/AKT and P42-44 MAPK signaling pathway.Moreover,analysis of clinical samples showed that high level of IGF2BP3 expression was negatively correlated with the quality of life and prognosis of MDS/AML patients.ABs from drug-resistant patients enhanced the proliferative and anti-apoptotic abilities of the recipient cells.Taken together,protein IGF2BP3 was enriched in ABs secreted by Ara-C-resistant cells,phagocytosed by Ara-C-sensitive cells,and enhanced the ability of these cells to evade apoptosis under chemotherapy.Cargoes(particularly IGF2BP3)that are overexpressed in donor cells and packaged into ABs are therefore potentially useful targets for more effective chemotherapy of MDS or AML patients.