In a previous study we demonstrated high expression of the non-coding BIC gene in the vast majority of Hodgkin's lymphomas (HLs). Evidence suggesting that BIC is a primary microRNA transcript containing the mature microRNA-155 (miR-155) as part of a RNA hairpin is now accumulating. We therefore analysed HL cell lines and tissue samples to determine whether miR-155 is also expressed in HL. High levels of miR-155 could be demonstrated, indicating that BIC is processed into a microRNA in HL. Most non-HL subtypes were negative for BIC as determined by RNA-ISH. However, in diffuse large B cell lymphoma (DLBCL) and primary mediastinal B cell lymphoma (PMBL), significant percentages of positive tumour cells were observed in 12/18 and 8/8 cases. A higher proportion of tumour cells were positive for BIC in DLBCL with activated B cell-like phenotype than in DLBCL with germinal centre B cell-like phenotype. Differential BIC expression was confirmed by qRT-PCR analysis. Northern blot analysis showed expression of miR-155 in all DLBCL and PMBL derived cell lines and tissue samples analysed. In summary, we demonstrate expression of primary microRNA BIC and its derivative miR-155 in HL, PMBL and DLBCL.

In a search for genes specifically expressed in Reed-Sternberg (RS) cells of Hodgkin lymphoma (HL), we applied the serial analysis of gene expression (SAGE) technique on the HL-derived cell line DEV. Genes highly expressed in DEV were subjected to an RT-PCR analysis to confirm the SAGE results. For one of the genes, a high expression was observed in DEV and other HL-derived cell lines but not in non-Hodgkin lymphoma (NHL)-derived cell lines and normal controls, suggesting an HL-specific expression. This gene corresponds to the human BIC gene, a member of the noncoding mRNA-like molecules. RNA in situ hybridization (ISH) indicated an exclusive nucleolar localization of BIC transcripts in all RS cells in 91% of HL cases, including nodular lymphocyte predominance (NLP) HL and classical HL. Analyses of normal human tissues revealed BIC transcripts in only a small number of CD20-positive B-cells in lymph node and tonsil tissue, albeit at a much lower level compared to that of RS cells. BIC RT-PCR in the Burkitt lymphoma-derived cell line Ramos demonstrated a significant up-regulation upon cross-linking of the B-cell receptor (BcR). IkappaBalpha-mediated blocking of NF-kappaB translocation in Ramos did not effect the up-regulation of BIC expression upon BcR triggering, suggesting that activation of NF-kappaB is not involved in regulation of BIC expression. In summary, our data show that expression of BIC is specific for RS cells of HL. In normal tissue, BIC is expressed weakly in a minority of germinal center B cells. Expression of BIC can be modified/influenced by BcR triggering, indicating that BIC might play a role in the selection of B cells.

MicroRNAs (miRNAs) are a set of small, non-protein-coding RNAs that regulate gene expression at the post-transcriptional level. Maturation of miRNAs comprises several regulated steps resulting in~22-nucleotide single-stranded mature miRNAs. Regulation of miRNA expression can occur both at the transcriptional level and at the post-transcriptional level during miRNA processing. Recent studies have elucidated specific aspects of the well-regulated nature of miRNA processing involving various regulatory proteins, editing of miRNA transcripts, and cellular location. In addition, single nucleotide polymorphisms in miRNA genes can also affect the processing efficiency of primary miRNA transcripts. In this review we present an overview of the currently known regulatory pathways of miRNA processing and provide a basis to understand how aberrant miRNA processing may arise and may be involved in pathophysiological conditions such as cancer.

BackgroundObesity promotes inflammation in adipose tissue (AT) and this is implicated in pathophysiological complications such as insulin resistance, type 2 diabetes and cardiovascular disease. Although based on the classical hypothesis, necrotic AT adipocytes (ATA) in obese state activate AT macrophages (ATM) that then lead to a sustained chronic inflammation in AT, the link between human adipocytes and the source of inflammation in AT has not been in-depth and systematically studied. So we decided as a new hypothesis to investigate human primary adipocytes alone to see whether they are able to prime inflammation in AT.Methods and ResultsUsing mRNA expression, human preadipocytes and adipocytes express the cytokines/chemokines and their receptors, MHC II molecule genes and 14 acute phase reactants including C-reactive protein. Using multiplex ELISA revealed the expression of 50 cytokine/chemokine proteins by human adipocytes. Upon lipopolysaccharide stimulation, most of these adipocyte-associated cytokines/chemokines and immune cell modulating receptors were up-regulated and a few down-regulated such as (ICAM-1, VCAM-1, MCP-1, IP-10, IL-6, IL-8, TNF-α and TNF-β highly up-regulated and IL-2, IL-7, IL-10, IL-13 and VEGF down-regulated. In migration assay, human adipocyte-derived chemokines attracted significantly more CD4+ T cells than controls and the number of migrated CD4+ cells was doubled after treating the adipocytes with LPS. Neutralizing MCP-1 effect produced by adipocytes reduced CD4+ migration by approximately 30%.ConclusionHuman adipocytes express many cytokines/chemokines that are biologically functional. They are able to induce inflammation and activate CD4+ cells independent of macrophages. This suggests that the primary event in the sequence leading to chronic inflammation in AT is metabolic dysfunction in adipocytes, followed by production of immunological mediators by these adipocytes, which is then exacerbated by activated ATM, activation and recruitment of immune cells. This study provides novel knowledge about the prime of inflammation in human obese adipose tissue, opening a new avenue of investigations towards obesity-associated type 2 diabetes.