MicroRNAs (miRNAs) are a class of posttranscriptional regulators that have recently introduced an additional level of intricacy to our understanding of gene regulation. There are currently over 10,000 miRNAs that have been identified in a range of species including metazoa, mycetozoa, viridiplantae, and viruses, of which 940, to date, are found in humans. It is estimated that more than 60% of human protein-coding genes harbor miRNA target sites in their 3′ untranslated region and, thus, are potentially regulated by these molecules in health and disease. This review will first briefly describe the discovery, structure, and mode of function of miRNAs in mammalian cells, before elaborating on their roles and significance during development and pathogenesis in the various mammalian organs, while attempting to reconcile their functions with our existing knowledge of their targets. Finally, we will summarize some of the advances made in utilizing miRNAs in therapeutics.

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MicroRNAs in development and disease.

https://uknowledge.uky.edu/cgi/viewcontent.cgi?article=1019&context=pathology_facpub

The miR-15/107 group of microRNA genes: evolutionary biology, cellular functions, and roles in human diseases.

MiR-210 – micromanager of the hypoxia pathway

Inadequate oxygen availability or hypoxia induces a complex and still incompletely understood set of adaptations that influence cellular survival and function. Many of these adaptations are directly controlled by a master transcription factor, hypoxia inducible factor-alpha (HIF-α). In response to hypoxia, HIF-α levels increase and directly induce the transcription of >100 genes, influencing functions ranging from metabolism, survival, proliferation, migration, to angiogenesis, among others. Recently, it has been demonstrated that a specific set of microRNA molecules are upregulated by hypoxia, which we denote here as “hypoxamirs.” In particular, the HIF-responsive hypoxamir microRNA-210 (miR-210) is a unique microRNA that is evolutionarily conserved and ubiquitously expressed in hypoxic cell and tissue types. A number of direct targets of miR-210 have been identified by in silico, transcriptional and biochemical methods, a subset of which have been extensively validated. As a result, miR-210 has been mechanistically linked to the control of a wide range of cellular responses known to influence normal developmental physiology as well as a number of hypoxia-dependent disease states, including tissue ischemia, inflammation and tumorigenesis. Thus, reflecting the pleiotropic actions of HIF-α, miR-210 appears to function as a “master microRNA” relevant for the control of diverse functions in the hypoxic state.

MicroRNA-210: A unique and pleiotropic hypoxamir

MicroRNAs (miRs) are small non-coding RNAs implicated mainly in post-transcriptional gene silencing by interacting with the unstranslated region of the transcript. miR-210 represents a major hypoxia-inducible miRs, also known as hypoxamirs, which is ubiquitously expressed in a wide range of cells, serving versatile functions. This review article summarizes the current progress on biogenesis of miR-210 and its physiological roles including arrest of cell proliferation, repression of mitochondrial respiration, arrest of DNA repair, vascular biology, and angiogenesis. Given the fact that miR-210 is aberrantly expressed in a number of diseases such as tumor progression, myocardial infarction and cutaneous ischemic wounds, miR-210 could serve as an excellent candidate for prognostic purposes and therapeutic intervention. With the advancement of computational prediction, high-throughput target validation methodology, sequencing, proteomic analysis and microarray, it is anticipated that more down-stream targets of miR-210 and its-associated biological consequences under hypoxia will be unveiled establishing miR-210 as a major hub in the biology of hypoxia-response.

/pdf/mir-210-the-master-hypoxamir-5dxxeedlup.pdf

miR-210: the master hypoxamir.

MicroRNAs (miRNAs) are small noncoding RNAs ( approximately 22 bp) that posttranscriptionally regulate gene expression. MiRNAs possess oncogenic or tumor suppressor activity in various tumors but little is known about miRNA expression pattern in malignant melanoma. We determined the expression level of 16 potentially relevant miRNAs (miR-15a, miR-15b, miR-16, miR-34a, miR-210, let-7I, miR-23a, miR-23b, miR-24, miR-27a, miR-27b, miR-100, miR-137, miR-222, miR-373-1, miR-373*) by real-time PCR in 6 preparations of normal melanocytes vs. 10 melanoma cell lines and in formalin fixed paraffin embedded tissue of 11 melanocytic nevi versus 16 melanomas. MiR-15b and miR-210 were significantly upregulated, miR-34a was significantly downregulated in melanomas compared with melanocytic nevi. These 3 miRNAs were analyzed in a total of 128 primary melanomas from patients with detailed clinical follow-up information. High expression of miR-15b (but not miR-210 upregulation and miR-34a downregulation) was significantly associated with poor recurrence free survival and overall survival by univariate Kaplan-Meier and multivariate Cox analyses. Downregulation of miR-15b in two melanoma cell lines with high miR-15b expression by transfection with anti-miR-15b siRNA was associated with reduced tumor cell proliferation, whereas apoptosis was increased. In summary, miRNA expression levels show distinct differences comparing benign and malignant melanocytic cell proliferations and can provide independent prognostic informations. MiR-15b appears to represent a particular important miRNA in melanoma that is associated with poor prognosis and tumorigenesis.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/ijc.24960

Bernward Voelker

Papers

MicroRNA‐15b represents an independent prognostic parameter and is correlated with tumor cell proliferation and apoptosis in malignant melanoma