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Abstract
CXCR4 / CXCL12 interaction plays an important role in both homing and retention of hematopoietic stem cells in the bone marrow. Leukemic cells express high levels of CXCR4, and this pathway plays a critical role in their migration into the bone marrow which supports their growth and survival. Antagonism of CXCR4 mobilizes stem cells into the bloodstream e.g. by AMD3100. MiRNA146a is one of the miRNAs most downmodulated in AML blasts. A highly significant inverse correlation between miR-146a expression and CXCR4 membrane protein level was found. Thus, upregulation of MiRNA146 may lead to down regulation of the CXCR4 protein levels and this relation may be used as a therapeutic modality. Thirty six denovo AML cases were selected. MiRNA146-a gene expression by real time PCR quantitation in leukemic cells before and after stimulation with vitamin D3 and AMD3100 was performed. Immunophenotypic characterization of surface and cytoplasmic expression of CXCR4 of isolated leukemic cells. Twenty four-hour stimulation with Vitamin D3 and AMD3100 was done followed by reestimation of surface and cytoplasmic expression of CXCR4. Cells were also cultured in special in vitro cell migration assay wells to detect effect of Vit D3 and AMD3100 on cell migration. AMD3100 increased miR146a expression which in turn downmodulated CXCR4 expression. Vit D3 also increased miRNA expression but less significantly. There was no statistically significant difference between effects of AMD3100 and Vit D3 on CXCR4 expression and cell migration. These findings suggest that Vit D3 may be considered as an alternative to AMD3100. Further research will indicate whether Vit D3 can be used as an adjuvant therapy to increase mobilization of leukemic stem cells from the bone marrow and improve response to chemotherapy