Role of CXCR4 antagonist in megakaryocyte reinstatement with increased sinusoidal vessel density

The bone marrow microenvironment (BMM) provides a protective niche that supports the growth and survival of leukemic stem cells. It is known that a regulation of homing to BM and retention of hematopoietic stem cells (HSCs) occur by SDF-1/CXCR4 axis in BMM. Previously, we found that altering the BMM by the CXCR4 antagonist led to enhanced cytotoxic activity of immune cells, which leads to increased susceptibility of leukemic cells to chemotherapeutic agents such as cytosine arabinoside (Ara-C) in leukemic BMM. However, no reports have yet shown an architectural change of BMM such as the sinusoidal vessel and megakaryocyte by plerixafor treatment. Thus, we performed immunohistochemistry and observed that the capillary density of sinusoidal vessels was highly increased by CXCR4 antagonist with Ara-C in leukemia, showing the reconstruction of BMM with megakaryocytes in sinusoidal vessels by dual treatment. The number of megakaryocytes was also increased in the Plerixafor treated group, compared to that of leukemic or wild groups. Ultimately, we addressed the normalization of megakaryocyte and BMM in leukemia by showing the reconstitution of the sinusoidal vasculature by Plerixafor. This study proposed that chemotherapy with CXCR4 antagonist represents an advanced therapeutic strategy of targeting the leukemic niche.