c-myc Plays Part in Drug Resistance Mediated by Bone Marrow Stromal Cells in Acute Myeloid Leukemia (#240)
Acute myeloid leukemia (AML) is a malignant disease not sensitive to chemotherapy. The dynamic interaction between AML cells and bone marrow (BM) microenvironment plays a critical role in response of this disease to chemotherapy. It’s reported that marrow stromal cells (MSC) are essential component of bone marrow microenvironment which affects the survival of AML cells. The aim of our research is to elucidate the mechanism of drug resistance of AML cells associating with MSC. We found that adhesion of AML cell lines U937, KG1a and primary AML cells to MSC inhibited cytotoxic drug-induced apoptosis. Western blot showed that c-myc of AML cells cocultured with stroma was up-regulated. Treatment with 10058-F4, a small molecule inhibitor of MYC-MAX heterodimerization, or c-myc siRNA significantly induced apoptosis. Western blot analysis further showed that inhibition of c-Myc increased expression of caspases-3, cleavage of PARP and reduced expression of Bcl-2, Bcl-xL and vascular endothelial growth factor (VEGF). Thus, we conclude that MSCs protected leukemia cells from apoptosis, at least in part, through c-Myc dependent mechanisms, and that c-myc contributed to microenvironment induced drug resistance in AML. In summary, we declared that c-Myc is a potential therapeutic target which mediated drug resistance in AML.