bay-11-7082 and Leukemia-Lymphoma--Adult-T-Cell

Topics: Animals; Antineoplastic Agents; Apoptosis; Arsenic Trioxide; Arsenicals; Drug Delivery Systems; Gene Expression Regulation; Gene Products, tax; Human T-lymphotropic virus 1; Humans; Leukemia-Lymphoma, Adult T-Cell; NF-kappa B; Nitriles; Oxides; Proteasome Inhibitors; Sulfones; T-Lymphocytes

The high mobility group box 1 (HMGB1) protein is a multifunctional cytokine-like molecule that plays an important role in the pathogenesis of tumors. In this study, real-time polymerase chain reactions and Western blot assays indicated that HMGB1 transcriptional activity and protein level are increased in Tax+-T cells (TaxP). To clarify the mechanisms, a series of HMGB1 deletion reporter plasmids (pHLuc1 to pHLuc6) were transfected into Tax--T cells (TaxN, Jurkat) and Tax+-T cells (TaxP). We found that promoter activity in Tax+-T cells to be higher than that in Tax--T cells, indicating a significant increase in pHLuc6. Bay11-7082 (NF-κB inhibitor) treatment did not block the enhancing effect. Chromatin immunoprecipitation assays revealed that Tax was retained on a HMGB1 promoter fragment encompassing -1163 to -975. Bioinformatics analysis showed six characteristic cis-elements for CdxA, AP-1, AML-1a, USF, v-Myb, and C/EBP in the fragment in question. Mutation of cis- elements for C/EBP reduced significant HMGB1 promoter activity induced by Tax. These findings indicate that Tax enhances the expression of HMGB1 gene at the transcriptional level, possibly by interacting with C/EBP.

Topics: CCAAT-Enhancer-Binding Proteins; Gene Expression Regulation, Leukemic; Gene Products, tax; Genes, Reporter; HMGB1 Protein; Humans; Jurkat Cells; Leukemia-Lymphoma, Adult T-Cell; NF-kappa B; Nitriles; Promoter Regions, Genetic; Sulfones; T-Lymphocytes; Transfection; Up-Regulation; Upstream Stimulatory Factors

Human T cell leukemia virus type 1 (HTLV-1) Tax-induced persistent activation of the NF-κB pathway is perceived as the primary cause of adult T cell leukemia (ATL), an aggressive leukemia caused by HTLV-1. Although elevated oncoprotein Bcl-3 levels are found in many HTLV-1-infected T cell lines and ATL cells, the role of Bcl-3 in the malignant progression caused by HTLV-1 retrovirus remains poorly understood. We confirmed, in the present study, that the Tax-induced NF-κB activation involves the regulation of Bcl-3. Both knockdown and overexpression of Bcl-3 inhibit the Tax-induced NF-κB activation. Similarly, excessive Bcl-3 inhibits the NF-κB/DNA binding activity and significantly decreases Tax-induced p65 nuclear translocation. The present results demonstrate the pleiotropic roles of Bcl-3 in Tax-induced NF-κB activation and indicate that a balance in the aberrant Bcl-3 expression may be established to play an important role in the maintenance of proliferation and inhibition of apoptosis in HTLV-1-infected and ATL cells.

Topics: Adult; Apoptosis; B-Cell Lymphoma 3 Protein; Blotting, Western; Cell Nucleus; Cell Proliferation; Cytoplasm; Electrophoretic Mobility Shift Assay; Fluorescent Antibody Technique; Gene Products, tax; Human T-lymphotropic virus 1; Humans; Leukemia-Lymphoma, Adult T-Cell; NF-kappa B; Nitriles; Plasmids; Protein Transport; Proto-Oncogene Proteins; RNA, Small Interfering; Sulfones; Transcription Factor RelA; Transcription Factors; Tumor Cells, Cultured

We established a novel experimental model for human T-cell leukemia virus type 1 (HTLV-1)-induced tumor using NOD-SCID/gammac(null) (NOG) mice. This model is very useful for investigating the mechanism of tumorigenesis and malignant cell growth of adult T-cell leukemia (ATL)/lymphoma, which still remains unclear. Nine HTLV-1-infected cell lines were inoculated subcutaneously in the postauricular region of NOG mice. As early as 2 to 3 weeks after inoculation, seven cell lines produced a visible tumor while two transformed cell lines failed to do so. Five of seven lines produced a progressively growing large tumor with leukemic infiltration of the cells in various organs that eventually killed the animals. Leukemic cell lines formed soft tumors, whereas some transformed cell lines developed into hemorrhagic hard tumors in NOG mice. One of the leukemic cell lines, ED-40515(-), was unable to produce visible tumors in NOD-SCID mice with a common gamma-chain after 2 weeks. In vivo NF-kappaB DNA binding activity of the ED-40515(-) cell line was higher and the NF-kappaB components were changed compared to cells in vitro. Bay 11-7082, a specific and effective NF-kappaB inhibitor, prevented tumor growth at the sites of the primary region and leukemic infiltration in various organs of NOG mice. This in vivo model of ATL could provide a novel system for use in clarifying the mechanism of growth of HTLV-1-infected cells as well as for the development of new drugs against ATL.

Topics: Animals; Antineoplastic Agents; Cell Line, Transformed; Disease Models, Animal; Graft Survival; HTLV-I Infections; Human T-lymphotropic virus 1; Humans; Leukemia-Lymphoma, Adult T-Cell; Leukemia, T-Cell; Lymphoma; Mice; Mice, Inbred NOD; Mice, SCID; Neoplasm Transplantation; Neoplasms, Experimental; NF-kappa B; Nitriles; Organic Chemicals; Sulfones

Human T-cell leukemia virus type I (HTLV-I) is the causative agent of an aggressive form of leukemia designated adult T-cell leukemia (ATL). We have previously demonstrated that all T-cell lines infected with HTLV-I and primary leukemic cells from ATL patients display constitutively high activity of transcription factor NF-kappaB. In this study we showed that Bay 11-7082, an inhibitor of NF-kappaB, induced apoptosis of HTLV-I-infected T-cell lines but only negligible apoptosis of HTLV-I-negative T cells. Bay 11-7082 rapidly and efficiently reduced the DNA binding of NF-kappaB in HTLV-I-infected T-cell lines and down-regulated the expression of the antiapoptotic gene, Bcl-x(L), regulated by NF-kappaB, whereas it had little effect on the DNA binding of another transcription factor, AP-1. Although the viral protein Tax is an activator of NF-kappaB, Bay 11-7082-induced apoptosis of HTLV-I-infected cells was not associated with reduced expression of Tax. Furthermore, Bay 11-7082- induced apoptosis of primary ATL cells was more prominent than that of normal peripheral blood mononuclear cells, and apoptosis of these cells was also associated with down-regulation of NF-kappaB activity. Our results indicate that NF-kappaB plays a crucial role in the pathogenesis and survival of HTLV-I-infected leukemic cells and that it is a suitable target for the prevention and treatment of ATL.

Topics: Adult; Antineoplastic Agents; Apoptosis; Down-Regulation; Human T-lymphotropic virus 1; Humans; Leukemia-Lymphoma, Adult T-Cell; NF-kappa B; Nitriles; Organic Chemicals; Sulfones; T-Lymphocytes; Tumor Cells, Cultured