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Related Collections Neoplasia Oncogenes and Tumor Suppressors Gene Expression Social Bookmarking                   What's this?  Previous Article  |  Table of Contents  |  Next Article  Blood, 1 May 2002, Vol. 99, No. 9, pp. 3367-3375 NEOPLASIA MDM2 induces NF-B/p65 expression transcriptionally through Sp1-binding sites: a novel, p53-independent role of MDM2 in doxorubicin resistance in acute lymphoblastic leukemia Lubing Gu, Harry W. Findley, and Muxiang Zhou From the Division of Pediatric Hematology/Oncology/BMT, Emory University School of Medicine, Atlanta, GA. MDM2 protein is thought to exhibit tumorigenic activity by binding to the p53 tumor-suppressor protein and inhibiting its function. Alternatively, MDM2 may have oncogenic roles other than those resulting from p53 interactions. Here we report that MDM2 can induce expression of the p65 subunit of NF-B, which is an anti-apoptotic factor expressed in certain neoplastic cells in response to chemotherapy. Initially, we noted that the overexpression of MDM2 protein in leukemic bone marrow cells of patients with B-cell precursor acute lymphoblastic leukemia (BCP-ALL), and an ALL cell line (EU-4) transfected with the MDM2 gene was associated with elevated expression of p65 and in vitro resistance to doxorubicin (Adriamycin). By cotransfection of the MDM2 gene and p65-promoter-reporter constructs into EU-4 cells, we found that transient and high-level MDM2 expression induced p65 promoter activity. In the presence of wild-type (wt) p53, MDM2 increased p65 promoter activity by reversing p53-mediated suppression of p65. In the absence of p53, MDM2 directly increased p65 promoter activity. Deletion and mutation analysis of the p65 promoter indicated that the region between nt 575 and 178, which contains the first and second Sp1-binding sites, was required for activation by MDM2. Further studies using chromatin immunoprecipitation (CHIP) and electrophoretic mobility shift assay (EMSA) showed that MDM2 was able to directly bind to the Sp1 site of the p65 promoter. Our findings suggest that by inducing p65 expression, MDM2 has a p53-independent role in tumorigenesis, which may further elucidate the association between MDM2 overexpression and resistant disease in childhood ALL. © 2002 by The American Society of Hematology.   CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this? This article has been cited by other articles: G. Chadalapaka, I. Jutooru, S. Chintharlapalli, S. Papineni, R. Smith III, X. Li, and S. Safe Curcumin Decreases Specificity Protein Expression in Bladder Cancer Cells Cancer Res., July 1, 2008; 68(13): 5345 - 5354. [Abstract] [Full Text] [PDF] N. Zhu, L. Gu, H. W. Findley, C. Chen, J.-T. Dong, L. Yang, and M. Zhou KLF5 Interacts with p53 in Regulating Survivin Expression in Acute Lymphoblastic Leukemia J. Biol. 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