cyclin-d1 and Leukemia--T-Cell

Protein arginine methyltransferase 5 (PRMT5) has been implicated as a key modulator of lymphomagenesis. Whether PRMT5 has overt oncogenic function in the context of leukemia/lymphoma and whether it represents a therapeutic target remains to be established. We demonstrate that inactivation of PRMT5 inhibits colony-forming activity by multiple oncogenic drivers, including cyclin D1, c-MYC, NOTCH1, and MLL-AF9. Furthermore, we demonstrate that PRMT5 overexpression specifically cooperates with cyclin D1 to drive lymphomagenesis in a mouse model, revealing inherent neoplastic activity. Molecular analysis of lymphomas revealed that arginine methylation of p53 selectively suppresses expression of crucial proapoptotic and antiproliferative target genes, thereby sustaining tumor cell self-renewal and proliferation and bypassing the need for the acquisition of inactivating p53 mutations. Critically, analysis of human tumor specimens reveals a strong correlation between cyclin D1 overexpression and p53 methylation, supporting the biomedical relevance of this pathway.. We have identified and functionally validated a crucial role for PRMT5 for the inhibition of p53-dependent tumor suppression in response to oncogenic insults. The requisite role for PRMT5 in the context of multiple lymphoma/leukemia oncogenic drivers suggests a molecular rationale for therapeutic development.

Topics: Adaptor Proteins, Signal Transducing; Amino Acid Substitution; Animals; Apoptosis; Arginine; Cell Transformation, Neoplastic; Cluster Analysis; Cyclin D1; Cyclin-Dependent Kinase 4; Enzyme Activation; Gene Expression Profiling; Humans; Leukemia, T-Cell; Lymphoma; Lymphoma, T-Cell; Methylation; Mice; Mutation; Oncogenes; Phosphorylation; Protein-Arginine N-Methyltransferases; Tumor Suppressor Protein p53

Jurkat human lymphoblastoid cells were incubated in increasing concentrations of doxorubicin (0.05, 0.1 and 0.15 μM) to induce cell death, and their expression of cyclin A, B1 and D1 was evaluated by flow cytometry (cell cycle progression, Annexin V assay, percentages and levels of each of the cyclins), transmission electron microscopy (ultrastructure) and confocal fluorescence microscopy (expression and intracellular localization of cyclins). After low-dose doxorubicin treatment, Jurkat cells responded mainly by G2/M arrest, which was related to increased cyclin B1, A and D1 levels, a low level of apoptosis and/or mitotic catastrophe. The influence of doxorubicin on levels and/or localization of selected cyclins was confirmed, which may in turn contribute to the G2/M arrest induced by the drug.

Topics: Antibiotics, Antineoplastic; Cell Cycle Checkpoints; Cell Death; Cyclin A; Cyclin B1; Cyclin D1; Doxorubicin; Gene Expression Regulation, Leukemic; Humans; Jurkat Cells; Leukemia, T-Cell

Adult T-cell leukemia (ATL) is a fatal malignancy of T lymphocytes caused by infection with human T-cell leukemia virus type I (HTLV-I) and remains incurable. Curcumin (diferuloylmethane), the major pigment of the spice turmeric, can be potentially effective by promoting cell apoptosis. Here we examined whether curcumin is effective in the treatment of ATL. Curcumin prevented cell growth of HTLV-I-infected T-cell lines and primary ATL cells but not of normal peripheral blood mononuclear cells. Curcumin induced cell cycle arrest by reducing the expression of cyclin D1, Cdk1 and Cdc25C and apoptosis by reducing the expression of XIAP and survivin. Most of these genes are known to be regulated by NF-kappaB, which plays a critical role in oncogenesis by HTLV-I. Curcumin suppressed constitutive active NF-kappaB of HTLV-I-infected T-cell lines and primary ATL cells by inhibiting phosphorylation of IkappaBalpha. Curcumin also inhibited Tax-induced NF-kappaB transcriptional activity. However, curcumin-induced suppression of cell growth did not correlate with Tax expression level. Curcumin inhibited the growth of HTLV-I-infected T-cell tumors implanted subcutaneously in SCID mice. Our results indicate that curcumin has tumor-suppressive activity against ATL.

Topics: Adult; Animals; Antineoplastic Agents; Apoptosis; CDC2 Protein Kinase; cdc25 Phosphatases; Cell Cycle; Cell Cycle Proteins; Cell Proliferation; Curcumin; Cyclin D1; Female; Gene Products, tax; Human T-lymphotropic virus 1; Humans; Inhibitor of Apoptosis Proteins; Leukemia-Lymphoma, Adult T-Cell; Leukemia, T-Cell; Mice; Mice, Inbred ICR; Mice, SCID; Microtubule-Associated Proteins; Neoplasm Proteins; NF-kappa B; Survivin; T-Lymphocytes; Tumor Cells, Cultured; X-Linked Inhibitor of Apoptosis Protein

Adult T-cell leukemia (ATL) is caused by human T-cell leukemia virus type I (HTLV-I) and remains incurable. NIK-333, a novel synthetic retinoid, prevents the recurrence of human hepatoma after surgical resection of primary tumors. We explored the effects of NIK-333 on HTLV-I-infected T-cell lines and ATL cells. NIK-333 inhibited cell proliferation, induced G1 arrest, and resulted in massive apoptosis in all tested HTLV-I-infected T-cell lines and ATL cells, whereas little effect was observed on normal peripheral blood mononuclear cells. NIK-333 treatment decreases the levels of cyclin D1, cyclin D2, cIAP2, and XIAP proteins. Further analysis showed that NIK-333 inactivated nuclear factor-kappaB in HTLV-I-infected T-cell lines. In animal studies, treatment with NIK-333 (100 mg/kg given orally every other day) produced partial inhibition of growth of tumors of a HTLV-I-infected T-cell line transplanted s.c. in severe combined immunodeficient mice. Our results indicate that NIK-333 is a potentially useful therapeutic agent for patients with ATL.

Topics: Animals; Apoptosis; Cell Line, Transformed; Cell Line, Tumor; Cyclin D1; Cyclin D2; Cyclins; Down-Regulation; Female; HTLV-I Infections; Human T-lymphotropic virus 1; Humans; Inhibitor of Apoptosis Proteins; Leukemia-Lymphoma, Adult T-Cell; Leukemia, T-Cell; Mice; Mice, Inbred Strains; NF-kappa B; Retinoids; Signal Transduction; T-Lymphocytes; X-Linked Inhibitor of Apoptosis Protein

The D-type cyclins (cyclins D1, D2, and D3) are components of the core cell cycle machinery in mammalian cells. Cyclin D3 gene is rearranged and the protein is overexpressed in several human lymphoid malignancies. In order to determine the function of cyclin D3 in development and oncogenesis, we generated and analyzed cyclin D3-deficient mice. We found that cyclin D3(-/-) animals fail to undergo normal expansion of immature T lymphocytes and show greatly reduced susceptibility to T cell malignancies triggered by specific oncogenic pathways. The requirement for cyclin D3 also operates in human malignancies, as knock-down of cyclin D3 inhibited proliferation of acute lymphoblastic leukemias deriving from immature T lymphocytes. These studies point to cyclin D3 as a potential target for therapeutic intervention in specific human malignancies.

Topics: Animals; Bone Marrow; Cell Cycle; Cell Differentiation; Cyclin D1; Cyclin D2; Cyclin D3; Cyclins; Flow Cytometry; Humans; Leukemia, T-Cell; Lymphocyte Specific Protein Tyrosine Kinase p56(lck); Lymphocytes; Membrane Proteins; Mice; Mice, Knockout; Models, Animal; Oligonucleotide Array Sequence Analysis; Receptors, Notch; RNA, Small Interfering; Tumor Cells, Cultured; Tumor Suppressor Protein p53

Our aim was to examine the involvement of G(1) cell-cycle regulators in cell growth dysregulation induced by HTLV-I. Compared to uninfected cells, higher expression levels of cyclin D1 and D2 mRNA were detected in HTLV-I-infected T-cell lines, which were at least in part mediated by the viral transforming protein Tax since Tax activated both cyclin D1 and D2 promoters in the human T-cell line Jurkat. A Tax mutant that did not activate NF-kappaB failed to activate cyclin D1 and D2 promoters. Inhibitors of NF-kappaB (dominant negative IkappaBs mutants) suppressed Tax-dependent activation of cyclin D1 and D2 promoters, indicating that Tax-induced activation was mediated by NF-kappaB. Wild-type and mutant Tax capable of activating NF-kappaB, but not Tax mutant incapable of activating NF-kappaB, converted cell growth of a T-cell line from being IL-2-dependent to being IL-2-independent; and this conversion was associated with IL-2-independent induction of cyclins D1 and D2. Our data suggest that induction of cyclins D1 and D2 by Tax is involved in IL-2-independent cell-cycle progression as well as IL-2-independent transformation of primary human T cells by HTLV-I. High expression levels of cyclin D1 and D2 mRNAs were also detected in some patients with ATL. Our findings link HTLV-I infection to changes in cellular D-type cyclin gene expression, transformation of T cells and subsequent development of T-cell leukemia.

Topics: Animals; Blotting, Northern; Blotting, Western; Cell Cycle; Cell Division; Cyclin D1; Cyclin D2; Cyclins; Gene Products, tax; Humans; Interleukin-2; Kinetics; Leukemia, T-Cell; Mice; NF-kappa B; Plasmids; Promoter Regions, Genetic; RNA, Messenger; T-Lymphocytes; Transcription, Genetic; Transcriptional Activation; Transfection; Tumor Cells, Cultured