Identification Of Bone Marrow Mesenchymal Stem Cell In Acute Myeloid Leukemia

Recently several studies demonstrated that there may be a relationship between some malignancy diseases and their microenvironment. The bone marrow mesenchymal stem cells (MSCs), which only long-lived cells of the bone marrow microenvironment, are abnormal in some hematologic malignancy diseases and involved in the etiology and progression of the diseases. The role of MSC in acute myeloid leukemia (AML) is still unclear. Here, we identified and addressed the role of MSC in AML.Firstly, we isolated bone marrow MSC from AML patients and healthy agematched persons. MSC derived from AML was then compared with normal adults derived MSC in morphology, phenotype, growth properties and function. The results showed that there were no significant differences between AML derived MSC and normal adult MSC in morphology, phenotype and growth properties, except that the content of AML derived MSC in unit volume bone marrow was increased along with the mononuclear cells number augmentation. Differentiation assays indicated that MSC isolated from AML patient can be differentiated into adipocytes, osteoblasts, and chondrocytes resemble those from normal adults. However, the osteogenic differentiation ability in AML derived MSC was obviously increased than those of normal adult MSC. Moreover, MSC derived from normal adults or AML patients can inhibit cellular or nonspecific mitogenic stimuli induced T cell proliferation with a dose-dependent manner. Real-time PCR also demonstrated that they expressed the similar immune cytokine. AML derived MSC showed a normal karyotype, and no leukemic related genes were detected.Secondly, to evaluate whether AML derived MSC was capable of supporting short-term or long-term hematopoietic expansion, AML derived MSC was as a feed-layer and cocultured with CD34+ cells from mobilized peripheral blood in long-term medium. As control, CD34+ cells were overlaid on wells with normal adults MSC. Consistent with previous reports, AML derived MSC could support long-term hematopoietic expansion in vitro. Real-time PCR assay showed a similar expression of hematopoietic cytokines in MSC derived from normal adults and AML.Finally, to determine whether expansion of HL-60 cells proliferation was caused by normal adults MSC or AML derived MSC, we cocultured HL-60 cells with AML derived MSC or normal adults MSC. Under these coculture condition, suppression of HL-60 proliferation was detected in coculture system with a dose dependent in vitro. Cell cycle analysis showed that HL-60 cells cocultured with MSC were blocked in G0/G1 phase and dramatic decreased entering S phase. Furthermore, HL-60 in coculture system displayed lower expression of CD11a and CD154 and had a significantly disadvantage in coculture group with AML derived MSC and HL-60, resulting in a obviously decreased expression cell phenotype. Moreover, the apoptosis from HL-60 induced by daunomycin (DNR) was suppressed by MSC derived from BM and AML and no significant difference in these two groups, correlating with the effect of MSC on the HL-60 cells, such as cell cycle, phenotype, and promoting antiapoptosis gene survivin exppression .In conclusion, our data suggested for the first time that AML derived MSCs possessed evident osteogenic differentiation, inhibition of T cell proliferation, supporting long-term hematopoietic expansion. Otherwise, MSCs derived from AML had an inhibitory effect on HL-60 cells apoptosis by DNR, and this effect was correlate with the alteration of cell cycle and phenotype, inhibition of proliferation, and up-regulation of antiapoptosis gene survivin in HL-60 cells by MSC. This study will be benefit for the following experimental explore, providing a new insight for AML hematoregulatory mechanism.