The Role Of HNRPDL In Chronic Myelogenous Leukemia Cells

Objective: This thesis aims to delineate the functions and molecular mechanisms of heterogeneous nuclear ribonucleoprotein D-like(HNRPDL)in chronic myeloid leukemia cells.Methods:(1)HNRPDL overexpressed Ba F3 cells were injected into lethally irradiated mice to study whether HNRPDL had transform ability.(2)Using Ba F3/BCR-ABL cells as model,the effects of HNRPDL silencing and HNRPDL overexpression on the malignant transformation ability of BCR-ABL were investigated.(3)The effects of HNRPDL silencing and HNRPDL overexpression on IM sensitivity of CML cells were studied.(4)The differentially expressed genes were identified with microarray data comparing HNRPDL silenced and control K562 cells.(5)The effect of PBX1 silencing on the growth,colony-forming cell ability and imatinib sensitivity was studied.(6)HNRPDL silenced K562 cells were infected with PBX1 overexpression vector,and whether the effects caused by HNRPDL silencing could be rescuded by PBX1 was studied.(7)The luciferase reporter assay and RNA immunoprecipitation(RIP)were performed to study the mechanism HNRPDL utilized to regulate the expression of PBX1.Results:(1)HNRPDL was able to transform Ba F3 cells and induce lethal mice leukemia(control,0/8;HNRPDL,7/8).(2)HNRPDL silencing inhibited the in vitro growth of Ba F3/BCR-ABL cells,in addition HNRPDL silencing attenuated the transform ability of BCR-ABL.Conversely,HNRPDL accelerated BCR-ABL induced mice leukemia.HNRPDL had higher expression in CD34+ cells from CML patients in blast crisis than those in chronic phase.(3)HNRPDL silencing enhanced imatinib sensitivity of K562 cells,while over-expression of HNRPDL enhanced the imatinibtolerance of K562 cells.Apoptosis detection showed that HNRPDL silencing enhanced the apoptosis induced by imatibib,while over-expression HNRPDL decreased the apoptosis induced by imatinib.(4)Microarray analysis and following validation showed that the expression of PBX1(pre-B-cell Leukemia Homeobox 1),MEIS2(Myeloid Ecotropic Viral Integration Site 1 Homolog 2)and m RAS(muscle RAS oncogene homolog)were significantly reduced upon HNRPDL silencing.Using CD34+ cells of CML patients as model,only PBX1 was significantly reduced after silencing HNRPDL.(5)Silence of PBX1 inhibited the growth of K562 and CML CD34+ cells,while silence of PBX1 increased imatinib sensitivity of K562 cells.(6)Overexpression of PBX1 was able to "rescue" the inhibitory effect on cell growth and elevated imatinib sensitivity caused by HNRPDL silencing.(7)Silence of HNRPDL reduced m RNA stability of PBX1.The luciferase reporter assay and RNA immunoprecipitaion(RIP)together demonstrated that PBX1 m RNA was direct target of HNRPDL.Conclusion: HNRPDL is essentially a proto-oncogene,its overexpression leads to malignant transformation of Ba F3 cells.HNRPDL and BCR-ABL collaboratively controls the in vitro and in vivo growth of Ba F3 cells.HNRPDL plays a pivotal role in imatinib response of CML cells.Mechanistically,the present study reveals a novel HNRPDL/PBX1 axis to regulate the growth and imatinib response of CML cells.