Although the role of APP and PSEN genes in genetic Alzheimer's disease (AD) cases is well established, fairly little is known about the molecular mechanisms affecting Aβ generation in sporadic AD. Deficiency in Aβ clearance is certainly a possibility, but increased expression of proteins like APP or BACE1/β-secretase may also be associated with the disease. We therefore investigated changes in microRNA (miRNA) expression profiles of sporadic AD patients and found that several miRNAs potentially involved in the regulation of APP and BACE1 expression appeared to be decreased in diseased brain. We show here that miR-29a, -29b-1, and -9 can regulate BACE1 expression in vitro . The miR-29a/b-1 cluster was significantly (and AD-dementia-specific) decreased in AD patients displaying abnormally high BACE1 protein. Similar correlations between expression of this cluster and BACE1 were found during brain development and in primary neuronal cultures. Finally, we provide evidence for a potential causal relationship between miR-29a/b-1 expression and Aβ generation in a cell culture model. We propose that loss of specific miRNAs can contribute to increased BACE1 and Aβ levels in sporadic AD.

MicroRNA-122 (miR-122) is an abundant liver-specific miRNA, implicated in fatty acid and cholesterol metabolism as well as hepatitis C viral replication. Here, we report that a systemically administered 16-nt, unconjugated LNA (locked nucleic acid)-antimiR oligonucleotide complementary to the 5' end of miR-122 leads to specific, dose-dependent silencing of miR-122 and shows no hepatotoxicity in mice. Antagonism of miR-122 is due to formation of stable heteroduplexes between the LNA-antimiR and miR-122 as detected by northern analysis. Fluorescence in situ hybridization demonstrated uptake of the LNA-antimiR in mouse liver cells, which was accompanied by markedly reduced hybridization signals for mature miR-122 in treated mice. Functional antagonism of miR-122 was inferred from a low cholesterol phenotype and de-repression within 24 h of 199 liver mRNAs showing significant enrichment for miR-122 seed matches in their 3' UTRs. Expression profiling extended to 3 weeks after the last LNA-antimiR dose revealed that most of the changes in liver gene expression were normalized to saline control levels coinciding with normalized miR-122 and plasma cholesterol levels. Combined, these data suggest that miRNA antagonists comprised of LNA are valuable tools for identifying miRNA targets in vivo and for studying the biological role of miRNAs and miRNA-associated gene-regulatory networks in a physiological context.

MicroRNAs (miRNAs) are a new class of short noncoding regulatory RNAs (18–25 nucleotides) that are involved in diverse developmental and pathologic processes. Altered miRNA expression has been associated with several types of human cancer. However, most studies did not establish whether miRNA expression changes occurred within cells undergoing malignant transformation. To obtain insight into miRNA deregulation in breast cancer, we implemented an in situ hybridization (ISH) method to reveal the spatial distribution of miRNA expression in archived formalin-fixed, paraffin-embedded specimens representing normal and tumor tissue from >100 patient cases. Here, we report that expression of miR-145 and miR-205 was restricted to the myoepithelial/basal cell compartment of normal mammary ducts and lobules, whereas their accumulation was reduced or completely eliminated in matching tumor specimens. Conversely, expression of other miRNAs was detected at varying levels predominantly within luminal epithelial cells in normal tissue; expression of miR-21 was frequently increased, whereas that of let-7a was decreased in malignant cells. We also analyzed the association of miRNA expression with that of epithelial markers; prognostic indicators such as estrogen receptor, progesterone receptor, and HER2; as well as clinical outcome data. This ISH approach provides a more direct and informative assessment of how altered miRNA expression contributes to breast carcinogenesis compared with miRNA expression profiling in gross tissue biopsies. Most significantly, early manifestation of altered miR-145 expression in atypical hyperplasia and carcinoma in situ lesions suggests that this miRNA may have a potential clinical application as a novel biomarker for early detection. [Cancer Res 2007;67(24):11612–20]

MicroRNAs are ∼22 nucleotide endogenous noncoding RNAs that post-transcriptionally repress expression of protein-coding genes by base-pairing with the 3′-untranslated regions of the target mRNAs. We present here an inventory of miRNA expression profiles from 13 neuroanatomically distinct areas of the adult mouse central nervous system (CNS). Microarray profiling in combination with real-time RT-PCR and LNA (locked nucleic acid)-based in situ hybridization uncovered 44 miRNAs displaying more than threefold enrichment in the spinal cord, cerebellum, medulla oblongata, pons, hypothalamus, hippocampus, neocortex, olfactory bulb, eye, and pituitary gland. These findings suggest that a large number of mouse CNS-expressed miRNAs may be associated with specific functions within these regions. Notably, more than 50% of the identified mouse CNS-enriched miRNAs showed different expression patterns compared to those reported in zebrafish, although the mature miRNA sequences are nearly 100% conserved between the two vertebrate species. The inventory of miRNA profiles in the adult mouse CNS presented here provides an important step toward further elucidation of miRNA function and miRNA-related gene regulatory networks in the mammalian central nervous system.

MicroRNAs (miRNA) are a class of small noncoding RNAs with important posttranscriptional regulatory functions. Recent data suggest that miRNAs are aberrantly expressed in many human cancers and that they may play significant roles in carcinogenesis. Here, we used microarrays to profile the expression of 315 human miRNAs in 10 normal mucosa samples and 49 stage II colon cancers differing with regard to microsatellite status and recurrence of disease. Several miRNAs were differentially expressed between normal tissue and tumor microsatellite subtypes, with miR-145 showing the lowest expression in cancer relative to normal tissue. Microsatellite status for the majority of cancers could be correctly predicted based on miRNA expression profiles. Furthermore, a biomarker based on miRNA expression profiles could predict recurrence of disease with an overall performance accuracy of 81%, indicating a potential role of miRNAs in determining tumor aggressiveness. The expression levels of miR-320 and miR-498, both included in the predictive biomarker, correlated with the probability of recurrence-free survival by multivariate analysis. We successfully verified the expression of selected miRNAs using real-time reverse transcription-PCR assays for mature miRNAs, whereas in situ hybridization was used to detect the accumulation of miR-145 and miR-320 in normal epithelial cells and adenocarcinoma cells. Functional studies showed that miR-145 potently suppressed growth of three different colon carcinoma cell lines. In conclusion, our results suggest that perturbed expression of numerous miRNAs in colon cancer may have a functional effect on tumor cell behavior, and, furthermore, that some miRNAs with prognostic potential could be of clinical importance. [Cancer Res 2008;68(15):6416–24]

MicroRNAs (miRNA) are involved in cancer development and progression, acting as tumor suppressors or oncogenes. Here, we profiled the expression of 290 unique human miRNAs in 11 normal and 106 bladder tumor samples using spotted locked nucleic acid–based oligonucleotide microarrays. We identified several differentially expressed miRNAs between normal urothelium and cancer and between the different disease stages. miR-145 was found to be the most down-regulated in cancer compared with normal, and miR-21 was the most up-regulated in cancer. Furthermore, we identified miRNAs that significantly correlated to the presence of concomitant carcinoma in situ. We identified several miRNAs with prognostic potential for predicting disease progression (e.g., miR-129, miR-133b, and miR-518c*). We localized the expression of miR-145, miR-21, and miR-129 to urothelium by in situ hybridization. We then focused on miR-129 that exerted significant growth inhibition and induced cell death upon transfection with a miR-129 precursor in bladder carcinoma cell lines T24 and SW780 cells. Microarray analysis of T24 cells after transfection showed significant miR-129 target down-regulation (P = 0.0002) and pathway analysis indicated that targets were involved in cell death processes. By analyzing gene expression data from clinical tumor samples, we identified significant expression changes of target mRNA molecules related to the miRNA expression. Using luciferase assays, we documented a direct link between miR-129 and the two putative targets GALNT1 and SOX4. The findings reported here indicate that several miRNAs are differentially regulated in bladder cancer and may form a basis for clinical development of new biomarkers for bladder cancer. [Cancer Res 2009;69(11):4851–60]