The SOX (Sry-related HMG box) genes belong to a family of transcription factors containing a High-Mobility-Group box domain. In an initial screen, SOX7 was uniquely down-regulated in myeloid malignancies compared with most cases of precursor B-cell acute lymphoblastic leukemia (ALL) and normal bone marrow cell, leading us to examine the expression and function of SOX7 during normal hematopoietic differentiation and in acute lymphoblastic leukemia. By studying human umbilical cord blood (UCB), SOX7 expression in different hematopoietic lineages was evaluated by RT-PCR. SOX7 was preferentially expressed in CD34+CD38- compared with CD34+CD38+ population and in CD34-CD19+ compared with CD34-CD33+ cells. SOX7 expression was down-regulated in colonies in CFU assay and in engrafting myeloid cells in NOD/SCID mouse transplantation. Transfecting SOX7 siRNA into CD34+ cells reduced cell growth and the CD34+CD33+ population in 3-day culture; induced cell-cycle arrest at G1 phase; reduced clonogenic activities but had no effect on apoptosis. Overall engraftment into NOD/SCID mice were not affected but the engrafting myeloid populations were reduced. In acute lymphoblastic leukemia, SOX7 was robustly expressed, compared with that in normal UCB and acute myeloid leukemia (AML). In 5 ALL patients in whom the coding sequence of SOX7 was examined, 3 of them showed mutations (amino acid change) in the SOX C-terminal transactivation domain. No mutation was observed in the β-catenin binding site. Knockdown of SOX7 with specific siRNA significantly increased appoptosis and decreased cell proliferation. SOX7 knockdown by shRNA in a precursor B-cell ALL cell line Nalm20 significantly reduced its engraftment into NOD/SCID mice. In summary, SOX7 is preferentially expressed in early hematopoietic stem and progenitor cells and is important for the maintenance of myeloid progenitor. It is also expressed in the primitive population of ALL and is important for leukemia initiation in ALL. The present study has generated important information about the regulation of normal hematopoiesis and acute lymphoblastic leukemia / published_or_final_version / Medicine / Doctoral / Doctor of Philosophy

T-cell acute lymphoblastic leukemia (T-ALL) is a lymphoid disorder that results from an over proliferation of immature lymphocytes in the blood and bone marrow. It has been determined that 60% of patients stricken with T-ALL aberrantly express TAL-1 and have been shown to respond poorly to chemotherapy. This research sought to determine if TAL-1 influences the expression of the Bcl-2 family members Bcl-2 (anti-apoptotic), Bad and Bax (pro-apoptotic). TAL-1 and Bcl-2 levels were elevated while Bad and Bax levels were lower in etoposide-treated Jurkat cells as compared to TRAIL-treated and dual-treated Jurkat cells in which TAL-1 and Bcl-2 levels were lower while Bad and Bax levels were elevated. These results suggest TAL-1 up-regulates Bcl-2 and suppress Bad and Bax expression in response to etoposide treatment, thus inducing an anti-apoptotic response in the cell. These results also suggest that TRAIL and the dual treatment of etoposide and TRAIL down-regulates TAL-1 and Bcl-2 expression while up-regulating Bad and Bax, thus inducing a pro-apoptotic response in the cell. / Department of Biology

TAL-1, ectopically expressed in 60% of T-cell acute lymphoblastic leukemia (T-ALL) patients, may contribute to poor chemotherapy response. This research sought to determine if TAL-1 influences expression of proteins involved in the NF-kB signaling pathway and thus, resistance to cell death. NF-kB, IKKy, and TRAF-2 expression levels were found to be TAL-1 dependent. Cell death levels were higher in staurosporine-treated cells compared to tumor necrosis factor a-treated or dual-treated cells. TAL-1, NF-kB, IKKy, and TRAF-2 expression levels were elevated in tumor necrosis factor a-treated cells and reduced in staurosporine-treated or dual treated cells compared to untreated cells. These results suggest TAL-1 influences expression of proteins involved in the NF-kB signaling pathway, thus inducing an anti-apoptotic response in the cell. / Department of Biology