miRNA expression in colon polyps provides evidence for a multihit model of colon cancer

Changes in miRNA expression are a common feature in colon cancer. Those changes occurring in the transition from normal to adenoma and from adenoma to carcinoma, however, have not been well defined. Additionally, miRNA changes among tumor subgroups of colon cancer have also not been adequately evaluated. In this study, we examined the global miRNA expression in 315 samples that included 52 normal colonic mucosa, 41 tubulovillous adenomas, 158 adenocarcinomas with proficient DNA mismatch repair (pMMR) selected for stage and age of onset, and 64 adenocarcinomas with defective DNA mismatch repair (dMMR) selected for sporadic (n = 53) and inherited colon cancer (n = 11). Sporadic dMMR tumors all had MLH1 inactivation due to promoter hypermethylation. Unsupervised PCA and cluster analysis demonstrated that normal colon tissue, adenomas, pMMR carcinomas and dMMR carcinomas were all clearly discernable. The majority of miRNAs that were differentially expressed between normal and polyp were also differentially expressed with a similar magnitude in the comparison of normal to both the pMMR and dMMR tumor groups, suggesting a stepwise progression for transformation from normal colon to carcinoma. Among the miRNAs demonstrating the largest fold up- or down-regulated changes (≥4), four novel (miR-31, miR-1, miR-9 and miR-99a) and two previously reported (miR-137 and miR-135b) miRNAs were identified in the normal/adenoma comparison. All but one of these (miR-99a) demonstrated similar expression differences in the two normal/carcinoma comparisons, suggesting that these early tumor changes are important in both the pMMR- and dMMR-derived cancers. The comparison between pMMR and dMMR tumors identified four miRNAs (miR-31, miR-552, miR-592 and miR-224) with statistically significant expression differences (≥2-fold change).     

MicroRNA 与垂体腺瘤关系的研究进展

MicroRNA(miRNA)是新发现的一类特殊的小分子RNA,在基因的转录后调控中扮演重要的角色.研究发现很多良恶性肿瘤在发生发展过程中都伴有miRNA的异常表达,所以miRNA的转录后调控机制以及在肿瘤成瘤过程中的作用逐渐成为当下研究的热点,本文就目前垂体腺瘤与miRNA的研究现状做以简要概述.     

Characterization of MicroRNA Expression Profiles and the Discovery of Novel MicroRNAs Involved in Cancer during Human Embryonic Development

MicroRNAs (miRNAs), approximately 22-nucleotide non-coding RNA molecules, regulate a variety of pivotal physiological or pathological processes, including embryonic development and tumorigenesis. To obtain comprehensive expression profiles of miRNAs in human embryos, we characterized miRNA expression in weeks 4-6 of human embryonic development using miRNA microarrays and identified 50 human-embryo-specific miRNAs (HES-miRNAs). Furthermore, we selected three non-conserved or primate-specific miRNAs, hsa-miR-638, -720, and -1280, and examined their expression levels in various normal and tumor tissues. The results show that expression of most miRNAs is extremely low during early human embryonic development. In addition, the expression of some non-conserved or primate-specific miRNAs is significantly different between tumor and the corresponding normal tissue samples, suggesting that the miRNAs are closely related to the pathological processes of various tumors. This study presents the first comprehensive overview of miRNA expression during human embryonic development and offers immediate evidence of the relationship between human early embryonic development and tumorigenesis.     

Genome-Wide Analysis of Small RNA and Novel MicroRNA Discovery in Human Acute Lymphoblastic Leukemia Based on Extensive Sequencing Approach

Background

MicroRNAs (miRNAs) have been proved to play an important role in various cellular processes and function as tumor suppressors or oncogenes in cancers including leukemia. The identification of a large number of novel miRNAs and other small regulatory RNAs will provide valuable insights into the roles they play in tumorgenesis.

Methodology/Principal Findings

To gain further understanding of the role of miRNAs relevant to acute lymphoblastic leukemia (ALL), we employed the sequencing-by-synthesis (SBS) strategy to sequence small RNA libraries prepared from ALL patients and normal donors. In total we identified 159 novel miRNAs and 116 novel miRNA*s from both libraries. Among the 159 novel miRNAs, 42 were identified with high stringency in our data set. Furthermore, we demonstrated the different expression patterns of 20 newly identified and several known miRNAs between ALL patients and normal donors, suggesting these miRNAs may be associated with ALL and could constitute an ALL-specific miRNA signature. Interestingly, GO “biological process” classifications revealed that a set of significantly abnormally expressed miRNAs are associated with disease relapse, which implies that these dysregulated miRNAs might promote the progression of ALL by regulating genes involved in the pathway of the disease development.

Conclusion/Significance

The study presents a comprehensive picture of the expression of small RNAs in human acute lymphoblastic leukemia and highlights novel and known miRNAs differentially expressed between ALL patients and normal donors. To our knowledge, this is the first study to look at genome-wide known and novel miRNA expression patterns in in human acute lymphoblastic leukemia. Our data revealed that these deregulated miRNAs may be associated with ALL or the onset of relapse.     

A comprehensive expression profile of microRNAs in porcine pituitary

MicroRNAs (miRNAs) are an abundant class of small RNAs that regulate expressions of most genes. miRNAs play important roles in the pituitary, the "master" endocrine organ.However, we still don't know which role miRNAs play in the development of pituitary tissue or how much they contribute to the pituitary function. By applying a combination of microarray analysis and Solexa sequencing, we detected a total of 450 miRNAs in the porcine pituitary. Verification with RT-PCR showed a high degree of confidence for the obtained data. According to the current miRBase release17.0, the detected miRNAs included 169 known porcine miRNAs, 163 conserved miRNAs not yet identified in the pig, and 12 potentially new miRNAs not yet identified in any species, three of which were revealed using Northern blot. The pituitary might contain about 80.17% miRNA types belonging to the animal. Analysis of 10 highly expressed miRNAs with the Kyoto Encyclopedia of Genes and Genomes (KEGG) indicated that the enriched miRNAs were involved not only in the development of the organ but also in a variety of inter-cell and inner cell processes or pathways that are involved in the function of the organ. We have revealed the existence of a large number of porcine miRNAs as well as some potentially new miRNAs and established for the first time a comprehensive miRNA expression profile of the pituitary. The pituitary gland contains unexpectedly many miRNA types and miRNA actions are involved in important processes for both the development and function of the organ.     

Phenotypical and Pharmacological Characterization of Stem-Like Cells in Human Pituitary Adenomas

The presence and functional role of tumor stem cells in benign tumors, and in human pituitary adenomas in particular, is a debated issue that still lacks a definitive formal demonstration. Fifty-six surgical specimens of human pituitary adenomas were processed to establish tumor stem-like cultures by selection and expansion in stem cell-permissive medium or isolating CD133-expressing cells. Phenotypic and functional characterization of these cells was performed (1) ex vivo, by immunohistochemistry analysis on paraffin-embedded tissues; (2) in vitro, attesting marker expression, proliferation, self-renewal, differentiation, and drug sensitivity; and (3) in vivo, using a zebrafish model. Within pituitary adenomas, we identified rare cell populations expressing stem cell markers but not pituitary hormones; we isolated and expanded in vitro these cells, obtaining fibroblast-free, stem-like cultures from 38 pituitary adenoma samples. These cells grow as spheroids, express stem cell markers (Oct4, Sox2, CD133, and nestin), show sustained in vitro proliferation as compared to primary cultures of differentiated pituitary adenoma cells, and are able to differentiate in hormone-expressing pituitary cells. Besides, pituisphere cells, apparently not tumorigenic in mice, engrafted in zebrafish embryos, inducing pro-angiogenic and invasive responses. Finally, pituitary adenoma stem-like cells express regulatory pituitary receptors (D2R, SSTR2, and SSTR5), whose activation by a dopamine/somatostatin chimeric agonist exerts antiproliferative effects. In conclusion, we provide evidence that human pituitary adenomas contain a subpopulation fulfilling biological and phenotypical signatures of tumor stem cells that may represent novel therapeutic targets for therapy-resistant tumors.     

ADAR1 is required for differentiation and neural induction by regulating microRNA processing in a catalytically independent manner

Adenosine deaminases acting on RNA (ADARs) are involved in adenosine-to-inosine RNA editing and are implicated in development and diseases. Here we observed that ADAR1 deficiency in human embryonic stem cells (hESCs) significantly affected hESC differentiation and neural induction with widespread changes in mRNA and miRNA expression, including upregulation of self-renewal-related miRNAs, such as miR302s. Global editing analyses revealed that ADAR1 editing activity contributes little to the altered miRNA/mRNA expression in ADAR1-deficient hESCs upon neural induction. Genome-wide iCLIP studies identified that ADAR1 binds directly to pri-miRNAs to interfere with miRNA processing by acting as an RNA-binding protein. Importantly, aberrant expression of miRNAs and phenotypes observed in ADAR1-depleted hESCs upon neural differentiation could be reversed by an enzymatically inactive ADAR1 mutant, but not by the RNA-binding-null ADAR1 mutant. These findings reveal that ADAR1, but not its editing activity, is critical for hESC differentiation and neural induction by regulating miRNA biogenesis via direct RNA interaction.     

Resveratrol alters microRNA expression profiles in A549 human non-small cell lung cancer cells

Resveratrol is a plant phenolic phytoalexin that has been reported to have antitumor properties in several types of cancers. In particular, several studies have suggested that resveratrol exerts antiproliferative effects against A549 human non-small cell lung cancer cells; however, its mechanism of action remains incompletely understood. Deregulation of microRNAs (miRNAs), a class of small, noncoding, regulatory RNA molecules involved in gene expression, is strongly correlated with lung cancer. In this study, we demonstrated that resveratrol treatment altered miRNA expression in A549 cells. Using microarray analysis, we identified 71 miRNAs exhibiting greater than 2-fold expression changes in resveratrol-treated cells relative to their expression levels in untreated cells. Furthermore, we identified target genes related to apoptosis, cell cycle regulation, cell proliferation, and differentiation using a miRNA target-prediction program. In conclusion, our data demonstrate that resveratrol induces considerable changes in the miRNA expression profiles of A549 cells, suggesting a novel approach for studying the anticancer mechanisms of resveratrol.     

Rare Circulating MicroRNAs as Biomarkers of Colorectal Neoplasia

Background

MicroRNAs (miRNAs) are regulatory RNAs, stable in circulation, and implicated in colorectal cancer (CRC) etiology and progression. Therefore they are promising as early detection biomarkers of colorectal neoplasia. However, many circulating miRNAs are highly expressed in blood cells, and therefore may not be specific to colorectal neoplasia.

Methods

We selected 7 miRNA candidates with previously reported elevated expression in adenoma tissue but low expression in blood cells (“rare” miRNAs), 2 previously proposed as adenoma biomarkers, and 3 implicated in CRC. We conducted a colonoscopy-based case-control study including 48 polyp-free controls, 43 advanced adenomas, 73 non-advanced adenomas, and 8 CRC cases. miRNAs from plasma were quantified by qRT-PCR. Correlations between miRNA expression levels, adjusted for age and sex, were assessed. We used polytomous logistic regression to estimate odds ratios (ORs) and 95% confidence intervals quantifying the association between expression levels of miRNAs and case groups. We also conducted nonparametric receiver operating characteristic (ROC) analyses and estimated area under the curve (AUC).

Results

miRNAs with high expression levels were statistically significantly correlated with one another. No miRNAs were significantly associated with non-advanced or advanced adenomas. Strong (ORs >5) and significant associations with CRC were observed for 6 miRNA candidates, with corresponding AUCs significantly >0.5.

Conclusions

These candidate miRNAs, assayed by qRT-PCR, are probably unsuitable as blood-based adenoma biomarkers. Strong associations between miRNAs and CRC were observed, but primarily with miRNAs highly expressed in blood cells. These results suggest that rare miRNAs will require new detection methods to serve as circulating biomarkers of adenomas.     

Adrenomedullin expression in pituitary adenomas and nontumoral adenohypophyses

Adrenomedullin (ADM) is a novel peptide originally identified in extracts of human pheochromocytoma. It is produced by several tissues, including the pituitary gland. The presence of ADM has been immunohistochemically demonstrated in pathologic pituitary glands, but no systematic study of ADM expression in human pituitary adenomas has been reported. Thus, we investigated ADM immunoexpression in 88 various hormone-secreting and clinically nonfunctioning pituitary adenoma types as well as 30 nontumoral adenohypophyses. Furthermore, ADM immunoreactivity was assessed on a 0 to +3 scale in all samples. We found strong immunoreativity for ADM in normal gonadotrophs also expressing FSH and LH whereas in the other adenohypophysial cell types expression of ADM was mild. Results showed that normal adenohypophyses were strongly immunopositive for ADM (2.18+/-0.11). Our findings demonstrate that ADM expression in the anterior pituitary is diminished in tumors as compared to the normal gland. The physiologic function of ADM is unknown, but it could act as a paracrine or autocrine factor in the adenohypophysis.     

A Ten-MicroRNA Signature Identified from a Genome-Wide MicroRNA Expression Profiling in Human Epithelial Ovarian Cancer

Epithelial ovarian cancer (EOC) is the most common gynecologic malignancy. To identify the micro-ribonucleic acids (miRNAs) expression profile in EOC tissues that may serve as a novel diagnostic biomarker for EOC detection, the expression of 1722 miRNAs from 15 normal ovarian tissue samples and 48 ovarian cancer samples was profiled by using a quantitative real-time polymerase chain reaction (qRT-PCR) assay. A ten-microRNA signature (hsa-miR-1271-5p, hsa-miR-574-3p, hsa-miR-182-5p, hsa-miR-183-5p, hsa-miR-96-5p, hsa-miR-15b-5p, hsa-miR-182-3p, hsa-miR-141-5p, hsa-miR-130b-5p, and hsa-miR-135b-3p) was identified to be able to distinguish human ovarian cancer tissues from normal tissues with 97% sensitivity and 92% specificity. Two miRNA clusters of miR183-96-183 (miR-96-5p, and miR-182, miR183) and miR200 (miR-141-5p, miR200a, b, c and miR429) are significantly up-regulated in ovarian cancer tissue samples compared to those of normal tissue samples, suggesting theses miRNAs may be involved in ovarian cancer development.