cyclin-d1 and Leukemia--Lymphoid

Multiple studies have established that microRNAs (miRNAs) are involved in the initiation and progression of cancer. Notably, miR-155 is one of the most overexpressed miRNAs in several solid and hematological malignancies. Ectopic miR-155 expression in mice B cells (Eμ-miR-155 transgenic mice) has been shown to induce pre-B-cell proliferation followed by high-grade lymphoma/leukemia. Loss of miR-155 in mice resulted in impaired immunity due to defective T-cell-mediated immune response. Here we provide a mechanistic insight into miR-155-induced leukemogenesis in the Eμ-miR-155 mouse model through genome-wide transcriptome analysis of naïve B cells and target studies. We found that a key transcriptional repressor and proto-oncogene, Bcl6 is significantly down-regulated in Eμ-miR-155 mice. The reduction of Bcl6 subsequently leads to de-repression of some of the known Bcl6 targets like inhibitor of differentiation (Id2), interleukin-6 (IL6), cMyc, Cyclin D1, and Mip1α/ccl3, all of which promote cell survival and proliferation. We show that Bcl6 is indirectly regulated by miR-155 through Mxd1/Mad1 up-regulation. Interestingly, we found that miR-155 directly targets HDAC4, a corepressor partner of BCL6. Furthermore, ectopic expression of HDAC4 in human-activated B-cell-type diffuse large B-cell lymphoma (DLBCL) cells results in reduced miR-155-induced proliferation, clonogenic potential, and increased apoptosis. Meta-analysis of the diffuse large B-cell lymphoma patient microarray data showed that miR-155 expression is inversely correlated with Bcl6 and Hdac4. Hence this study provides a better understanding of how miR-155 causes disruption of the BCL6 transcriptional machinery that leads to up-regulation of the survival and proliferation genes in miR-155-induced leukemias.

Topics: Animals; B-Lymphocytes; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; Cell Line; Cyclin D1; Flow Cytometry; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Histone Deacetylases; Humans; Immunoblotting; Inhibitor of Differentiation Protein 2; Interleukin-6; Leukemia, Lymphoid; Luciferases; Mice; Mice, Transgenic; Microarray Analysis; MicroRNAs; Proto-Oncogene Mas; Proto-Oncogene Proteins c-bcl-6; Real-Time Polymerase Chain Reaction; Repressor Proteins; Signal Transduction; Transcription, Genetic

The ubiquitin-proteasome system (UPS) participates in both physiological and pathological processes through the posttranslational regulation of intracellular signal transduction pathways. F-box and WD-40 domain protein 11 (Fbxw11) is a component of the SCF (Skp1-Cul1-F-box) E3 ubiquitin ligase complex. Fbxw11 regulates various signal transduction pathways, and it may have pathological roles in tumorigenesis. However, the role of Fbxw11 in the development of leukemia and the underlying mechanisms remain largely unknown. In this study, Fbxw11 expression was aberrantly upregulated in patients with lymphocytic leukemia. Its expression was dramatically decreased in patients who achieved complete remission (CR) after chemotherapy. The high level of Fbxw11 expression in L1210 lymphocytic leukemia cells stimulated cell proliferation in vitro and tumor formation in vivo. The effects were mediated by the stimulation of cell cycle progression rather than the induction of apoptosis. Furthermore, a bioinformatics analysis suggested concomitant activation of the NF-κB and β-catenin/TCF signaling pathways, which were confirmed by reporter gene assays. Moreover, blocking experiments suggested the involvement of both pathways in the growth-promoting effects of Fbxw11. Our results reveal the role of Fbxw11 in lymphocytic leukemia cells and imply that Fbxw11 may serve as a potential molecular target for the treatment of lymphocytic leukemia.

Topics: Animals; beta Catenin; beta-Transducin Repeat-Containing Proteins; Cell Cycle Checkpoints; Cell Line, Tumor; Cell Proliferation; Cyclin D1; Female; Humans; Leukemia, Lymphoid; Mice; Mice, Inbred DBA; NF-kappa B; Protein Isoforms; RNA Interference; RNA, Small Interfering; Signal Transduction; TCF Transcription Factors; Transcriptome; Transplantation, Heterologous; Ubiquitin-Protein Ligases

Most lymphoid malignancies are initiated by specific chromosomal translocations between immunoglobulin (Ig)/T cell receptor (TCR) gene segments and cellular proto-oncogenes. In many cases, illegitimate V(D)J recombination has been proposed to be involved in the translocation process, but this has never been functionally established. Using extra-chromosomal recombination assays, we determined the ability of several proto-oncogenes to target V(D)J recombination, and assessed the impact of their recombinogenic potential on translocation rates in vivo. Our data support the involvement of 2 distinct mechanisms: translocations involving LMO2, TAL2, and TAL1 in T cell acute lymphoblastic leukemia (T-ALL), are compatible with illegitimate V(D)J recombination between a TCR locus and a proto-oncogene locus bearing a fortuitous but functional recombination site (type 1); in contrast, translocations involving BCL1 and BCL2 in B cell non-Hodgkin's lymphomas (B-NHL), are compatible with a process in which only the IgH locus breaks are mediated by V(D)J recombination (type 2). Most importantly, we show that the t(11;14)(p13;q32) translocation involving LMO2 is present at strikingly high frequency in normal human thymus, and that the recombinogenic potential conferred by the LMO2 cryptic site is directly predictive of the in vivo level of translocation at that locus. These findings provide new insights into the regulation forces acting upon genomic instability in B and T cell tumorigenesis.

Topics: Adaptor Proteins, Signal Transducing; Animals; Basic Helix-Loop-Helix Transcription Factors; Child; Cyclin D1; DNA-Binding Proteins; Humans; Leukemia-Lymphoma, Adult T-Cell; Leukemia, Lymphoid; LIM Domain Proteins; Lymphoma; Metalloproteins; Mice; Models, Genetic; Neoplasm Proteins; Proto-Oncogene Mas; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Recombination, Genetic; T-Cell Acute Lymphocytic Leukemia Protein 1; Thymus Gland; Transcription Factors; Translocation, Genetic

Twenty-three patients with marked leukemic involvement by mantle cell lymphoma (MCL) are described. Each patient had an absolute lymphocyte count more than 10 x 10(9)/L. The diagnosis of MCL was supported by compatible immunophenotypic findings and the t(11;14)(q13;q32) in all cases. Morphologically, these cases exhibited a spectrum of findings that we divided into two groups using a cutoff of 20% large or blastoid cells (log rank test, P =.004). Patients with small-cell (<20%) morphologic features survived longer than patients with large/blastoid (> or =20%) morphologic features, (P =.003, log rank test). The most common additional karyotypic abnormality identified in this study involved chromosome 17, in 13 of 23 (56.5%) cases, which correlated with p53 overexpression but not with cytologic features. We conclude that cytologic features of MCL predict the prognosis of patients with marked leukemic involvement. Chromosome 17 abnormalities are common in leukemic MCL, may be involved in pathogenesis, and are associated with p53 expression.

Topics: Adult; Aged; Antigens, CD19; Antigens, CD20; CD5 Antigens; Chromosomes, Human, Pair 11; Chromosomes, Human, Pair 14; Cyclin D1; Female; Glycoproteins; Humans; Immunoglobulin Light Chains; Immunohistochemistry; Immunophenotyping; Leukemia, Lymphoid; Lymphoma, Mantle-Cell; Male; Middle Aged; Survival Analysis; Translocation, Genetic; Tumor Suppressor Protein p53