While the long non-coding RNAs (ncRNAs) constitute a large portion of the mammalian transcriptome, their biological functions has remained elusive. A few long ncRNAs that have been studied in any detail silence gene expression in processes such as X-inactivation and imprinting. We used a GENCODE annotation of the human genome to characterize over a thousand long ncRNAs that are expressed in multiple cell lines. Unexpectedly, we found an enhancer-like function for a set of these long ncRNAs in human cell lines. Depletion of a number of ncRNAs led to increased expression of their neighboring protein-coding genes, including the master regulator of hematopoiesis, SCL (also called TAL1), Snai1 and Snai2. Using heterologous transcription assays we demonstrated a requirement for the ncRNAs in mediating such enhancement of gene expression. These results reveal an unanticipated role for a class of long ncRNAs in activation of critical regulators of development and differentiation.

MicroRNAs (miRNAs) are single-stranded, noncoding RNAs that are important in many biological processes. Although the oncogenic and tumour-suppressive functions of several miRNAs have been characterized, the role of miRNAs in mediating tumour metastasis was addressed only recently and still remains largely unexplored. To identify potential metastasis-promoting miRNAs, we set up a genetic screen using a non-metastatic, human breast tumour cell line that was transduced with a miRNA-expression library and subjected to a trans-well migration assay. We found that human miR-373 and miR-520c stimulated cancer cell migration and invasion in vitro and in vivo, and that certain cancer cell lines depend on endogenous miR-373 activity to migrate efficiently. Mechanistically, the migration phenotype of miR-373 and miR-520c can be explained by suppression of CD44. We found significant upregulation of miR-373 in clinical breast cancer metastasis samples that correlated inversely with CD44 expression. Taken together, our findings indicate that miRNAs are involved in tumour migration and invasion, and implicate miR-373 and miR-520c as metastasis-promoting miRNAs.

To study mechanisms by which free fatty acids (FFAs) cause hepatic insulin resistance, we have used euglycemichyperinsulinemic clamping with and without infusion of lipid/heparin (to raise or to lower plasma FFAs) in alert male rats. FFA-induced hepatic insulin resistance was associated with increased hepatic diacylglycerol content (؉210%), increased activities of two serine/threonine kinases (protein kinase C-␦ and inhibitor of B [IB] kinase-␤), increased activation of the proinflammatory nuclear factor-B (NF-B) pathway (IB kinase-␤, ؉640%; IB-␣, ؊54%; and NF-B, ؉73%), and increased expression of inflammatory cytokines (tumor necrosis factor-␣, ؉1,700% and interleukin-1␤, ؉440%) and plasma levels of monocyte chemoattractant protein-1 (؉220%). We conclude that FFAs caused hepatic insulin resistance, which can produce overproduction of glucose and hyperglycemia, and initiated inflammatory processes in the liver that could potentially result in the development of steatohepatitis. Diabetes 54: 3458 -3465, 2005 O besity is closely associated with insulin resistance, type 2 diabetes, and the metabolic syndrome (also called the insulin resistance syndrome) (1). Obesity is also associated with increased presence in the circulation of several proinflammatory cytokines and chemokines and because of that has also been considered an inflammatory condition (rev. in 2). Whereas the reason for these associations is not entirely clear, it has been established that free fatty acids (FFAs) are a major link between obesity and insulin resistance/type 2 diabetes. This is based on the following evidence: most obese people have elevated plasma FFA levels, and FFAs cause insulin resistance dose dependently in skeletal muscle and liver (rev in 3). In skeletal muscle, FFAs inhibit insulin-stimulated glucose uptake at the level of glucose transport and/or phosphorylation (4,5) through mechanisms that involve intramyocellular accumulation of diacylglycerol (DAG) and long-chain acyl-CoA, activation of protein kinase C (PKC), and decreased tyrosine phosphorylation of insulin receptor substrate 1/2 (IRS-1/2) (6,7). The mechanisms by which FFAs cause hepatic insulin resistance have been directly addressed by only one study. In that study, Lam et al. (8) have shown that infusion of lipids (which increased plasma FFA levels) resulted in activation of PKC-␦ in rat liver.In the present study, we have used the lipid/heparin infusion to study effects of acutely elevated plasma FFA levels on insulin action in the rat liver. In this model, plasma FFA levels rise about equally in the systemic and the portal circulation. This is similar to the situation in postabsorptive, obese individuals who have ϳ80% of their fat in subcutaneous and intramuscular adipose tissue (releasing FFAs into the peripheral circulation) and ϳ20% of their fat in visceral adipose tissue (releasing FFAs at an increased rate into the portal circulation) (9,10). RESEARCH DESIGN AND METHODSAdult male Sprague-Dawley rats (250 -300 g) were purchased from Charles River Laboratorie...

Elevated expression of polo-like kinase1 (Plk1) has been reported in many human tumors, and inhibition of Plk1 activity results in their mitotic arrest and apoptosis. Here we describe the profile of ON01910, a small molecule inhibitor of Plk1 activity, which induces mitotic arrest of tumor cells characterized by spindle abnormalities leading to their apoptosis. This compound was not ATP-competitive, but competed for the substrate binding site of the enzyme. In vivo, this compound did not exhibit hematotoxicity, liver damage, or neurotoxicity, and was a potent inhibitor of tumor growth in a variety of xenograft nude mouse models. ON01910 showed strong synergy with several chemotherapeutic agents, often inducing complete regression of tumors.

Short, but significant, microRNAs (miRNAs) are an important class of gene regulators. Small‐molecule modifiers of miRNA function, such as 1 (see schematic representation), were identified in a cellular screen for miRNA‐pathway inhibitors. Such compounds are expected to be useful tools for the elucidation of detailed mechanisms of miRNA action and may serve as lead structures for the development of new therapeutic agents.