Human T cell leukemia virus type 1 (HTLV-1), an etiological factor that causes adult T cell leukemia and lymphoma (ATL), infects over 20 million people worldwide. About 1 million of HTLV-1-infected patients develop ATL, a highly aggressive non-Hodgkin's lymphoma without an effective therapy. The pX region of the HTLV-1 viral genome encodes an oncogenic protein, Tax, which plays a central role in transforming CD4+ T lymphocytes by deregulating oncogenic signaling pathways and promoting cell cycle progression. Expression of Tax following viral entry is critical for promoting survival and proliferation of human T cells and is required for initiation of oncogenesis. Tax exhibits diverse functions in host cells, and this oncoprotein primarily targets IκB kinase complex in the cytoplasm, resulting in persistent activation of NF-κB and upregulation of its responsive gene expressions that are crucial for T cell survival and cell cycle progression. We here review recent advances for the pathological roles of Tax in modulating IκB kinase activity. We also discuss our recent observation that Tax connects the IκB kinase complex to autophagy pathways. Understanding Tax-mediated pathogenesis will provide insights into development of new therapeutics in controlling HTLV-1-associated diseases.
Autophagy ; CD4-Positive T-Lymphocytes ; metabolism ; virology ; Cell Cycle ; Cell Transformation, Neoplastic ; genetics ; Gene Expression Regulation, Neoplastic ; Gene Products, tax ; genetics ; metabolism ; Human T-lymphotropic virus 1 ; physiology ; Humans ; I-kappa B Kinase ; genetics ; metabolism ; Leukemia-Lymphoma, Adult T-Cell ; genetics ; metabolism ; virology ; Membrane Microdomains ; metabolism ; virology ; NF-kappa B ; genetics ; metabolism ; Protein Binding ; Signal Transduction ; genetics

We experienced a case of adult T cell leukemia/lymphoma (ATLL) in a 48-year-old Korean female, who has never been abroad since birth and no history of blood transfusion. The patient had hypercalcemia and multiple lymphadenopathy. Histopathologic study of left cervical lymph node (LN) and bone marrow (BM) revealed that infiltrates of malignant lymphoid cells were composed of small, medium and large cells with pleomorphic nuclei. Smears of peripheral blood (PB) showed lymphopenia (16%) with the appearance of a few atypical lymphoid cells (less than 2%), but not the typical clover leaf cells seen in ATLL. Immunophenotypic study of LN and BM revealed T cell phenotype. PB showed increased CD4+ T cell (T(H), CD3/CD4+, 57%) and decreased CD8+ T cell counts (T(S), CD3/CD8+, 6.7%). The sera of the patient and her family were reactive for HTLV-I antibody. The specific sequences of pol, env, and tax of HTLV-I DNA were detected in the lymphoma cells and peripheral blood mononuclear cells (PBMC) using polymerase chain reaction. Ultrastructural examination of PBMC confirmed numerous type c virus particles in extracellular space. This case was an acute type of ATLL without overt leukemic features in PB. Despite chemotherapy and intensive conservative treatment, she died 3 months after admission.
Biopsy ; Bone Marrow/pathology ; Case Report ; DNA, Viral/analysis ; Fatal Outcome ; Female ; Flow Cytometry ; Gene Products, env/genetics ; Gene Products, pol/genetics ; Gene Products, tax/genetics ; HTLV-BLV Infections/pathology ; HTLV-I ; Human ; Hypercalcemia/virology ; Hypercalcemia/pathology ; Immunophenotyping ; Korea ; Leukemia, T-Cell/virology ; Leukemia, T-Cell/pathology* ; Leukemia, T-Cell/immunology ; Lymph Nodes/pathology ; Lymphopenia/virology ; Lymphopenia/pathology* ; Lymphopenia/immunology ; Microscopy, Electron ; Middle Age ; Support, Non-U.S. Gov't ; T-Lymphocytes/virology ; T-Lymphocytes/ultrastructure ; T-Lymphocytes/pathology