MicroRNAs (miRNAs) are short non-coding RNAs that fine-tune gene expression. The aberrant expression of miRNAs is associated with many diseases and they have both therapeutic and biomarker potential. However, our understanding of their usefulness is dependent on the tools we have to study them. Previous studies have identified the need to optimise and standardise RNA extraction methods in order to avoid biased results. Herein, we extracted RNA from murine lung, liver and brain tissues using five commercially available total RNA extraction methods. These included either: phenol: chloroform extraction followed by alcohol precipitation (TRIzol), phenol:chloroform followed by solid-phase extraction (column-based; miRVana and miRNeasy) and solid-phase separation with/without affinity resin (Norgen total and Isolate II). We then evaluated each extraction method for the quality and quantity of RNA recovered, and the expression of miRNAs and target genes. We identified differences between each of the RNA extraction methods in the quantity and quality of RNA samples, and in the analysis of miRNA and target gene expression. For the purposes of consistency in quantity, quality and high recovery of miRNAs from tissues, we identified that Phenol:chloroform phase separation combined with silica column-based solid extraction method was preferable (miRVana microRNA isolation). We also identified a method that is not appropriate for miRNA analysis from tissue samples (Bioline Isolate II). For target gene expression any of the kits could be used to analyse mRNA, but if interested in analysing mRNA and miRNA from the same RNA samples some methods should be avoided. Different methods used to isolate miRNAs will yield different results and therefore a robust RNA isolation method is required for reproducibility. Researchers should optimise these methods for their specific application and keep in mind that “total RNA” extraction methods do not isolate all types of RNA equally.

MicroRNAs (miRNAs) are a family of short, non-coding RNA molecules that drive a complex network of post-transcriptional gene regulation by enhancing target mRNA decay and/or inhibiting protein synthesis from mRNA transcripts. They regulate genes involved in key aspects of normal cell growth, development and the maintenance of body homeostasis and have been closely linked to the development and progression of human disease, in particular cancer. Over recent years there has been much interest regarding their potential as biomarkers and as therapeutic agents or targets. microRNA-7 (miR-7) is a 23 nucleotide (nt) miRNA known primarily to act as a tumour suppressor. miR-7 directly inhibits a number of oncogenic targets and impedes various aspects of cancer progression in vitro and in vivo, however, some studies have also implicated miR-7 in oncogenic roles. This review summarises the role of miR-7 in cancer, its potential in miRNA-based replacement therapy and its capacity as both a diagnostic and prognostic biomarker.

The ETS1 transcription factor is overexpressed in human prostate cancers in comparison to nonmalignant prostate and exhibits nuclear, in addition to aberrant cytoplasmic localisation. A previous report has identified direct interaction between ETS1 and the androgen receptor (AR) in the prostate cancer cell line, LNCaP and we have demonstrated that this ligand-dependent interaction is mediated via the ETS (DNA binding) domain of ETS1 and the ligand-binding domain of the AR. In a cohort of 44 prostate cancer cases, mRNA for the full-length ETS1 isoform, p54ETS1 was detected in all prostate tumour and adjacent nonmalignant prostate tissues, while expression of the internally truncated p42^ETS1 isoform was very low or undetectable. In protein lysates extracted from the same cases, p54^ETS1 was detected in all samples, with expression of a lower molecular weight ETS1 corresponding in size to the dominant negative p27^ETS1 isoform also observed. Increased expression of one or both of the ETS1 isoforms was identified in 38 (86%) cases, supporting the elevated expression of ETS1 in human prostate tumours. Both ETS1 and the AR upregulate expression of the prostatic tumour suppressor, NKX3.1 via sequences located in the 5′ promoter and 3′ untranslated region (3′UTR), respectively. Although unresponsive to androgens, the proximal ∼2kb of the NKX3.1 promoter, and in particular a 76bp sequence surrounding the ETS binding site (EBS) become androgen responsive following ETS1 overexpression. In addition, in LNCaP cells that stably overexpress p54^ETS1, the biphasic proliferative responses to androgens, where low (≤10⁻¹⁰M) DHT concentrations stimulate proliferation and higher (>10⁻¹⁰M) DHT levels inhibit proliferation, were altered and DHT concentrations as low as 10⁻¹²M inhibited proliferation. The findings indicate that the increased expression of ETS1 commonly observed in human prostate tumours may modify the androgen responsiveness of the cancer cells, augmenting AR-mediated regulation of androgen target genes and potentially sensitising prostate cancer cells to the very low androgen levels in men treated with androgen ablation therapies.