Ratiometric Detection of microRNA Using Hybridization Chain Reaction and Fluorogenic Silver Nanoclusters

miRNA (miR)-155 is a potential biomarker for breast cancers. We aimed at developing a nanosensor for miR-155 detection by integrating hybridization chain reaction (HCR) and silver nanoclusters (AgNCs). HCR serves as an enzyme-free and isothermal amplification method, whereas AgNCs provide a built-in fluorogenic detection probe that could simplify the downstream analysis. The two components were integrated by adding a nucleation sequence of AgNCs to the hairpin of HCR. The working principle was based on the influence of microenvironment towards the hosted AgNCs, whereby unfolding of hairpin upon HCR has manipulated the distance between the hosted AgNCs and cytosine-rich toehold region of hairpin. As such, the dominant emission of AgNCs changed from red to yellow in the absence and presence of miR-155, enabling a ratiometric measurement of miR with high sensitivity. The limit of detection (LOD) of our HCR-AgNCs nanosensor is 1.13 fM in buffered solution. We have also tested the assay in diluted serum samples, with comparable LOD of 1.58 fM obtained. This shows the great promise of our HCR-AgNCs nanosensor for clinical application.     

Induction of senescence in cancer cells by 5′-Aza-2′-deoxycytidine: Bioinformatics and experimental insights to its targets

5′-Aza-2′-deoxycytidine (5-Aza-dC) is a demethylating drug that causes genome-wide hypomethylation resulting in the expression of several tumor suppressor genes causing growth arrest of cancer cells. Cancer is well established as a multifactorial disease and requires multi-module therapeutics. Search for new drugs and their approval by FDA takes a long time. Keeping this in view, research on new functions of FDA-approved anticancer drugs is desired to expand the list of multi-module functioning drugs for cancer therapy. In this study, we conducted an analysis for new functions of 5-Aza-dC by applying bio-chemo-informatics approach. The potential of 5-Aza-dC bioactivity was analyzed by PASS online and Molinspiration. Target proteins were predicted by SuperPred. The protein networks and biological processes were analyzed by Biological Networks using Gene Ontology tool, BINGO, based on BIOGRID database. Interactions between 5-Aza-dC and targeted proteins were examined by Autodoc Vina integrated into pyrx software. Induction of p53 by 5-Aza-dC was tested in vitro using cancer cells. Bioinformatics analyses predicted that 5-Aza-dC functions as a p53 inducer, radiosensitizer, and inhibitor of some enzymes. It was predicted to target proteins including MDM2, POLA1, POLB, and CXCR4 that are involved in the induction of DNA damage response and p53-HDM2-p21 signaling. In this study, we provide experimental evidence showing HDM2 is one of the targets of 5-AZA-dC leading to activation of p53 pathway and growth arrest of cells. Furthermore, we found that the combinatorial treatment of 5-AZA-dC with three other drugs caused drug resistance. We discuss that 5-Aza-dC-induced senescence is a multi-module drug that controls cell proliferation phenotype not only by proteins but also by noncoding miRNAs. Further studies are warranted to dissect these mechanisms and establish 5-Aza-dC as an effective multi-module anticancer reagent.     

The regulation of microRNA in each of cancer stage from two different ethnicities as potential biomarker for breast cancer

miRNA has recently emerged as a potential biomarker for breast cancer. Even though many studies have identified ethnic variation affecting miRNA regulation, the effect of cancer stage within specific ethnicities on miRNA epigenetic remains unclear. The present study is designed to investigate miRNA regulation from two distinct ethnicities in specific cancer stages (non-Hispanic white and non-Hispanic black) using the TCGA dataset. Differentially expressed miRNAs were calculated by using the edgeR package. miRNAs with the highest or lowest log fold Change from each cancer stage were selected as a potential biomarker. miRNA-gene interaction was analyzed by using spearman correlation analysis, CLUEGO, and DIANA-mirpath. The association of biomarker candidates with diagnostic and prognostic performance was assessed using ROC and Kaplan-Meier survival analysis. miRNA-gene interaction analysis revealed the involvement of selected miRNAs in cancer progression. From eleven selected aberrant miRNAs, four of the miRNAs (hsa-mir-495, hsa-mir-592, hsa-mir-6501, and hsa-mir-937) are significantly detrimental to breast cancer diagnosis and prognosis. Hence, our result provides valuable information to explore miRNA’s role in each cancer stage between non-Hispanic white and non-Hispanic black.     

Fluorescence Signal Amplification Strategies Based on DNA Nanotechnology for miRNA Detection

In this review,the most recent progresses in the field of fluorescence signal amplification strategies based on DNA nanotechnology for miRNA are summarized.The types of signal amplification are given and the principles of amplification strategies are explained,including rolling circle amplification(RCA),catalytic hairpin assembly(CHA),hybridization chain reaction(HCR)and DNA walker.Subsequently,the application of these signal amplification methods in biosensing and bioimaging are covered and described.Finally,the challenges and the outlook of fluorescence signal amplification methods for miRNA detection are briefly commented.     

Trends in microRNA detection

MicroRNAs (miRNAs) are short, ~22 nucleotide length RNAs that perform gene regulation. Recently, miRNA has been shown to be linked with the onset of cancer and other diseases based on miRNA expression levels. It is important, therefore, to understand miRNA function as it pertains to disease onset; however, in order to fully understand miRNA’s role in a disease, it is necessary to detect the expression levels of these small molecules. The most widely used miRNA detection method is Northern blotting, which is considered as the standard of miRNA detection methods. This method, however, is time-consuming and has low sensitivity. This has led to an increase in the amount of detection methods available. These detection methods are either solid phase, occurring on a solid support, or solution phase, occurring in solution. While the solid-phase methods are adaptable to high-throughput screening and possess higher sensitivity than Northern blotting, they lack the ability for in vivo use and are often time-consuming. The solution-phase methods are advantageous in that they can be performed in vivo, are very sensitive, and are rapid; however, they cannot be applied in high-throughput settings. Although there are multiple detection methods available, including microarray technology, luminescence-based assays, electrochemical assays, etc., there is still much work to be done regarding miRNA detection. The current gaps of miRNA detection include the ability to perform multiplex, sensitive detection of miRNA with single-nucleotide specificity along with the standardization of these new methods. Current miRNA detection methods, gaps in these methods, miRNA therapeutic options, and the future outlook of miRNA detection are presented here.     

U6 is unsuitable for normalization of serum miRNA levels in patients with sepsis or liver fibrosis

MicroRNA (miRNA) levels in serum have recently emerged as potential novel biomarkers for various diseases. miRNAs are routinely measured by standard quantitative real-time PCR (qPCR); however, the high sensitivity of qPCR demands appropriate normalization to correct for nonbiological variation. Presently, RNU6B (U6) is used for data normalization of circulating miRNAs in many studies. However, it was suggested that serum levels of U6 themselves might differ between individuals. Therefore, no consensus has been reached on the best normalization strategy in ‘circulating miRNA''. We analyzed U6 levels as well as levels of spiked-in SV40-RNA in sera of 44 healthy volunteers, 203 intensive care unit patients and 64 patients with liver fibrosis. Levels of U6 demonstrated a high variability in sera of healthy donors, patients with critical illness and liver fibrosis. This high variability could also be confirmed in sera of mice after the cecal ligation and puncture procedure. Most importantly, levels of circulating U6 were significantly upregulated in sera of patients with critical illness and sepsis compared with controls and correlated with established markers of inflammation. In patients with liver fibrosis, U6 levels were significantly downregulated. In contrast, levels of spiked-in SV40 displayed a significantly higher stability both in human cohorts (healthy, critical illness, liver fibrosis) and in mice. Thus, we conclude that U6 levels in the serum are dysregulated in a disease-specific manner. Therefore, U6 should not be used for data normalization of circulating miRNAs in inflammatory diseases and previous studies using this approach should be interpreted with caution. Further studies are warranted to identify specific regulatory processes of U6 levels in sepsis and liver fibrosis.