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“Introduction Chronic Myeloid Leukemia(CML) is a malignant selleckchem myeloproliferative disorder originating from a pluripotent stem cell that expresses the BCR/ABL oncogene and is characterized by abnormal release of the expanded, malignant stem cell clone from the bone marrow into the circulation[1, 2]. The discovery of the Philadelphia chromosome followed by identification of its BCR/ABL fusion gene product and the resultant constitutively active P210 BCR/ABL tyrosine kinase prompted the unravelling

of the molecular pathogenesis of CML. However, regardless of greatly reduced mortality rates with BCR/ABL targeted therapy, most patients harbor quiescent CML stem cells that may be a reservoir for disease progression to blast crisis. Under steady-state conditions, these cancer stem cells are localized in a microenvironment known as the stem cell “”niche”", where they are maintained in an undifferentiated and quiescent state. These niches are critical for regulating the self-renewal and cell fate decisions, yet why and how these cells are recruited to affect leukemia progression are not well known. Local secretion of proteases has been implicated in this tumor-stroma crosstalk. Matrix metalloproteinase-9 (MMP-9) is one of the proteases

that has the preferential ability to degrade denatured collagens (gelatin) and collagen type IV, the 2 main components of basement membranes and therefore plays a critical role in tumor p38 MAPK apoptosis progression and metastasis[3, 4]. Previous studies have demonstrated localization of MMP-9 on the plasma membrane of various tumor cells[5–7] and recently, the role of MMP-9 in CML pathogenesis has became a focus of attention[8–11]. But the research is mainly focusing on the MMP-9 inducing molecules[12–14] or the effect of MMP-9 inhibitors[15]. However, it has become clear that the role of MMP-9 in CML is not limited to simple extracellular

matrix (ECM) degradation[16]. The regulation of MMP-9 is found to be involved in multiple ZD1839 clinical trial pathways induced by different kinds of cytokines in different cell types and illness[17, 18]. Therefore, it is necessary to verify a specific MMP-9 induced pathway in a given cell type. Recent research[6, 10, 4] showed that T lymphocytes isolated from CML patients suppressed the forming of CFU-GM (colony forming unit-granulocyte and macrophage) and CFU-E (colony forming unit-erythroid) and furthermore this kind of inhibition could be blocked by CsA(cyclosporine A)[19, 20];besides, the rate of the forming of the HSCs (hematopoietic stem cells) increased with the removal of T lymphocytes. Therefore, immunological inhibitors like CsA. and ATG (anti-human thymocyte globulin) was helpful for CML patients and was widely used in clinic therapy[21–23].