Oncogene Regulation Iaspp And Iasppsv Of Hematopoietic Stem Cells And Its Pathogenic Role In Leukemia

Objective:To investigate the role of iASPP and iASPPsv expression levels in acute leukemia (AL) and its clinical significance, explore the possible mechanisms for those two p53-induced apoptosis repressors in term of self-renewal, proliferation and differentiation of HSCs by hematopietic-specific promoter HS21/45 vav to high expression iASPP and iASPPsv in vivo. Characterize the relationship between those two p53-induced repressor proteins and biofunctions of HSCs with transgenic mice models.Methods:We examined mRNA expression levels of iASPP and iASPPsv in bone marrow sample from 147 patients and 20 normal controls by reverse transcription PCR (RT-PCR) and detected proteins expression of some samples level by Western-blot. The transgenic plasmids of iASPP and iASPPsv were microinjected into C57BL/6J fertilized egg. RT-PCR and Western blot analysis confirmed that iASPPs were abundantly expressed in hematopoietic tissues of the transgenic mice, including bone marrow, thymus and spleen, from hematopoietic stem cells (HSC), multipotent progenitor cells to more differentiated cells, but not in control littermates. To analysis biological functions of those oncoproteins on HSCs self-renewal, differentiation and proliferation by competitive BM transplantation, serial transplantation experiments, limited dilution transplantation, apoptosis and cell migration assay.Results:Expression levels of oncogenes iASPP and iASPPsv mRNA in bone marrow of AL patients were unregulated, especially of iASPPsv (p=0.034 and p<0.01). FSC analysis change on hematopoietic stem cells (HSCs) and multipotent progenitor cells in those mice and those oncoproteins exhibited distinct biofunction on HSCs and hematological malignancies. Interestingly, about 30 percent iASPP and iASPPsv transgenic mice developed dyshematopoiesis in 16 months and 11 months, respectively, whereas nontransgenic littermates mice remained disease-free. The possibility of iASPP to increasing percentage of long-term (LT) hematopoietic stem cells, common myeloid progenitors (CMPs) and granulocyte-macrophage progenitors (GMPs) was impaction on stimulating proliferation on HSCs to strengthen its bone marrow reconstitute ability. On the other hand, iASPPsv decreased HSCs percentage of transgenic mice leading to ineffective hematopoiesis by accelerating their self-renewal. Furthermore, LSK cells of those two mice models exhibited resistance to radiation-induced apoptosis and enhanced cellular repairment, suggesting a mechanism leading to ineffective hematopoiesis and increasing the risk of accumulation on genetic mutation in the presence of a hypercellular bone marrow.Conclusion:Oncoproteins iASPP and iASPPsv could strengthen HSCs self-renewal, differentiation and proliferation by increasing resistance to radiation-induced apoptosis suggesting they involved in process of HSCc transformed into leukemia stem cells. These results demonstrate the coupling of p53 tumor suppressive proteins with HSCs self-renewal and highlight the roles of iASPP in leukemogenesis, hence facilitating specific therapeutic strategies for hematological malignancies.