microRNA expression patterns across seven cancers are highly correlated and dominated by evolutionarily ancient families

MicroRNAs as Guardians of the Prostate: Those Who Stand before Cancer. What Do We Really Know about the Role of microRNAs in Prostate Biology?

Prostate cancer is the second leading cause of cancer-related deaths of men in the Western world. Despite recent advancement in genomics, transcriptomics and proteomics to understand prostate cancer biology and disease progression, castration resistant metastatic prostate cancer remains a major clinical challenge and often becomes incurable. MicroRNAs (miRNAs), about 22-nucleotide-long non-coding RNAs, are a group of regulatory molecules that mainly work through post-transcriptional gene silencing via translational repression. Expression analysis studies have revealed that miRNAs are aberrantly expressed in cancers and have been recognized as regulators of prostate cancer progression. In this critical review, we provide an analysis of reported miRNA functions and conflicting studies as they relate to expression levels of specific miRNAs and prostate cancer progression; oncogenic and/or tumor suppressor roles; androgen receptor signaling; epithelial plasticity; and the current status of diagnostic and therapeutic applications. This review focuses on select miRNAs, highly expressed in normal and cancer tissue, to emphasize the current obstacles faced in utilizing miRNA data for significant impacts on prostate cancer therapeutics.

Trimester-specific plasma exosome microRNA expression profiles in preeclampsia

Objective: To identify microRNAs (miRNAs) differentially expressed in plasma exosomes collected in women diagnosed with preeclampsia compared with women with uncomplicated pregnancies.Materials and methods: Exosomes were purified from plasma samples obtained at each trimester from four women subsequently diagnosed with preeclampsia and from five matched healthy controls. RNA was purified from the exosomes, and expression of 368 miRNAs was profiled using A-Set TaqMan low density array (TLDA).Results: One-third of the 368 miRNAs profiled are not expressed in exosomes. Further, those that are not expressed tend to be evolutionarily younger and have a significantly different mature sequence signature than do miRNAs that are expressed in exosomes. Among miRNAs that are expressed in exosomes, a total of eight (miR-134, miR-196b, miR-302c, miR-346, miR-376c, miR-486-3p, miR-590-5p, and miR-618) were found to display statistically significant differential expression between women who developed preeclampsia as compared with those who did not. Moreover, half of these miRNAs (miR-134, miR-376c, miR-486-3p, and miR-590-5p) displayed statistically significant differential expression in the first trimester.Conclusions: Not all miRNAs are expressed in exosomes. Those that tend to be evolutionarily older and have a significantly different mature sequence signature than those that are not. A few exosome-expressed miRNAs do display expression patterns in women subsequently diagnosed with preeclampsia that are significantly different than in women having an uncomplicated and, among these, several appear in the first trimester. These miRNAs are potential early markers of preeclampsia risk.

Dysregulation of miR-181c expression influences recurrence of endometrial endometrioid adenocarcinoma by modulating NOTCH2 expression: An NRG Oncology/Gynecologic Oncology Group study

OBJECTIVE

Endometrial cancer can be diagnosed early and cured, yet cases that recur portend a very poor prognosis with over 10,000 women succumbing to the disease every year. In this study we addressed the question of how to recognize cases likely to recur early in the course of therapy using dysregulation of tumor microRNAs (miRNAs) as predictors.

METHODS

Using the tissue collection from Gynecologic Oncology Group Study-210, we selected and analyzed expression of miRNAs in 54 recurrent and non-recurrent cases. The three most common histologic types, endometrioid adenocarcinoma (EEA), serous adenocarcinoma (ESA) and carcinosarcoma (UCS), were analyzed as three independent sets and their miRNA expression profiles compared.

RESULTS

Only one miRNA was statistically different between recurrent and non-recurrent cases, and in only one histologic type: significant down-regulation of miR-181c was observed in EEA recurrence. Using several well-known databases to assess miR-181c targets, one target of particular relevance to cancer, NOTCH2, was well supported. Using The Cancer Genome Atlas and our validation tumor panel from the GOG-210 cohort, we confirmed that NOTCH2 is significantly over-expressed in EEA. In the most relevant endometrial adenocarcinoma cell model, Ishikawa H, altering miR-181c expression produces significant changes in NOTCH2 expression, consistent with direct targeting.

CONCLUSIONS

Our findings suggest that increased NOTCH2 via loss of miR-181c is a significant component of EEA recurrence. This presents an opportunity to develop miR-181c and NOTCH2 as markers for early identification of high risk cases and the use of NOTCH inhibitors in the prevention or treatment of recurrent disease.

A Uniform System for the Annotation of Vertebrate microRNA Genes and the Evolution of the Human microRNAome

Although microRNAs (miRNAs) are among the most intensively studied molecules of the past 20 years, determining what is and what is not a miRNA has not been straightforward. Here, we present a uniform system for the annotation and nomenclature of miRNA genes. We show that less than a third of the 1,881 human miRBase entries, and only approximately 16% of the 7,095 metazoan miRBase entries, are robustly supported as miRNA genes. Furthermore, we show that the human repertoire of miRNAs has been shaped by periods of intense miRNA innovation and that mature gene products show a very different tempo and mode of sequence evolution than star products. We establish a new open access database--MirGeneDB ( http://mirgenedb.org )--to catalog this set of miRNAs, which complements the efforts of miRBase but differs from it by annotating the mature versus star products and by imposing an evolutionary hierarchy upon this curated and consistently named repertoire.