MicroRNA and cancer--a brief overview. Adv Biol Regul. 2015;57:1-9. [PMID: 25294678 DOI: 10.1016/j.jbior.2014.09.013]

MicroRNA-375 as a biomarker for malignant transformation in oral lesions

OBJECTIVE

Malignant transformation of oral premalignant lesions is the key process in the progression to oral squamous cell carcinoma (OSCC). Previously, we identified miR-7 and miR-21 as candidate oncogenes and miR-375 and miR-494 as candidate tumor suppressors in OSCC. We aim to evaluate these microRNAs as biomarkers of malignant transformation in oral premalignant lesions.

STUDY DESIGN

Formalin-fixed, paraffin-embedded samples from progressive premalignant lesions and paired sequential OSCC tumors at the same site were obtained from same patients (n = 31). Total RNA was extracted and analyzed for microRNA levels using real-time polymerase chain reaction.

RESULTS

MiR-375 expression in progressive lesions was clearly lower than in nonprogressive control lesions (average eightfold difference, P = .0004). Furthermore, the expression of miR-375 decreased significantly after the progression from premalignant lesion to OSCC (P < .0001). Receiver operating characteristic curve analysis revealed that miR-375 was able to differentiate between progressive and nonprogressive premalignant lesions (P < .0001).

CONCLUSIONS

MiR-375 downregulation in oral premalignant lesions is associated with a higher risk of malignant transformation.

MicroRNA-21 promotes proliferation, migration, and invasion of colorectal cancer, and tumor growth associated with down-regulation of sec23a expression

Background

MicroRNA-21 (miR-21) is up-regulated in many cancers, including colorectal cancer (CRC). Nevertheless, the function of miR-21 in CRC and the mechanism underlying that function is still unclear.

Methods

After analyzing the expression of miR-21 and Sec23A in CRC cell lines, we transfected the highest miR-21 expressing cell line, SW-480, with a plasmid containing an miR-21 inhibitor and the lowest miR-21 expressing cell line, DLD-1, with a plasmid containing an miR-21 mimic and measured the effects on the expression of Sec23A and on cell proliferation, migration, and invasion. We also evaluated the effect of knocking down Sec23A on miR-21 expression and its effects on cell proliferation, migration, and invasion. Finally, we assessed the effect of miR-21 in a xenograft tumor model in mice. Tumor tissues from these mice were subjected to immunohistochemical staining to detect the expression of Sec23A.

Results

Genetic deletion of miR-21 suppressed the proliferation, migration, and invasion of SW-480 cells, while over-expression of miR-21 promoted proliferation, migration, and invasion of DLD-1 cells. Inhibition of miR-21 increased the expression of Sec23A protein in SW-480 cells while over-expression of miR-21 significantly suppressed the expression of Sec23A protein and Sec23A mRNA in DLD-1 cells. Knockdown of Sec23A increased the expression of miR-21 in SW480 and DLD-1 cells and their proliferation (DLD-1 only), migration, and invasion. Over-expression of miR-21 promoted tumor growth in BALB/c nude mice and suppressed tumor expression of Sec23A.

Conclusion

These findings provide novel insight into the molecular functions of miR-21 in CRC, which may serve as a potential interesting target.

Colorectal tumor molecular phenotype and miRNA: expression profiles and prognosis

MiRNAs regulate gene expression by post-transcriptionally suppressing mRNA translation or by causing mRNA degradation. It has been proposed that unique miRNAs influence specific tumor molecular phenotype. In this paper, we test the hypotheses that miRNA expression differs by tumor molecular phenotype and that those differences may influence prognosis. Data come from population-based studies of colorectal cancer conducted in Utah and the Northern California Kaiser Permanente Medical Care Program. A total of 1893 carcinoma samples were run on the Agilent Human miRNA Microarray V19.0 containing 2006 miRNAs. We assessed differences in miRNA expression between TP53-mutated and non-mutated, KRAS-mutated and non-mutated, BRAF-mutated and non-mutated, CpG island methylator phenotype (CIMP) high and CIMP low, and microsatellite instability (MSI) and microsatellite stable (MSS) colon and rectal tumors. Using a Cox proportional hazard model we evaluated if those miRNAs differentially expressed by tumor phenotype influenced survival after adjusting for age, sex, and AJCC stage. There were 22 differentially expressed miRNAs for TP53-mutated colon tumors and 5 for TP53-mutated rectal tumors with a fold change of >1.49 (or <0.67). Additionally, 13 miRNAS were differentially expressed for KRAS-mutated rectal tumors, 8 differentially expressed miRNAs for colon CIMP high tumors, and 2 differentially expressed miRNAs for BRAF-mutated colon tumors. The majority of differentially expressed miRNAS were observed between MSI and MSS tumors (94 differentially expressed miRNAs for colon; 41 differentially expressed miRNAs for rectal tumors). Of these miRNAs differentially expressed between MSI and MSS tumors, the majority were downregulated. Ten of the differentially expressed miRNAs were associated with survival; after adjustment for MSI status, five miRNAS, miR-196b-5p, miR-31-5p, miR-99b-5p, miR-636, and miR-192-3p, were significantly associated with survival. In summary, it appears that the majority of miRNAs that are differentially expressed by tumor molecular phenotype are MSI tumors. However, these miRNAs appear to have minimal effect on prognosis.

Pancreatic Cancer Cell Exosome-Mediated Macrophage Reprogramming and the Role of MicroRNAs 155 and 125b2 Transfection using Nanoparticle Delivery Systems

Exosomes are nano-sized endosome-derived small intraluminal vesicles, which are important facilitators of intercellular communication by transporting contents, such as protein, mRNA, and microRNAs, between neighboring cells, such as in the tumor microenvironment. The purpose of this study was to understand the mechanisms of exosomes-mediated cellular communication between human pancreatic cancer (Panc-1) cells and macrophages (J771.A1) using a Transwell co-culture system. Following characterization of exosome-mediated cellular communication and pro-tumoral baseline M2 macrophage polarization, the Panc-1 cells were transfected with microRNA-155 (miR-155) and microRNA-125b-2 (miR-125b2) expressing plasmid DNA using hyaluronic acid-poly(ethylene imine)/hyaluronic acid-poly(ethylene glycol) (HA-PEI/HA-PEG) self-assembling nanoparticle-based non-viral vectors. Our results show that upon successful transfection of Panc-1 cells, the exosome content was altered leading to differential communication and reprogramming of the J774.A1 cells to an M1 phenotype. Based on these results, genetic therapies targeted towards selective manipulation of tumor cell-derived exosome content may be very promising for cancer therapy.

MicroRNA-1 properties in cancer regulatory networks and tumor biology

Short non-coding microRNAs have been identified to orchestrate crucial mechanisms in cancer progression and treatment resistance. MicroRNAs are involved in posttranscriptional modulation of gene expression and therefore represent promising targets for anticancer therapy. As mircoRNA-1 (miR-1) exerted to be predominantly downregulated in the majority of examined tumors, miR-1 is classified to be a tumor suppressor with high potential to diminish tumor development and therapy resistance. Here we review the complex functionality of miR-1 in tumor biology.

Prognostic role of miR-9 expression in various human malignant neoplasms: a meta-analysis

Emerging evidence has shown that aberrant microRNA expression has the potential to be used for predicting survival and treatment response of malignant neoplasms. In recent years, the role of miR-9 had been investigated in various types of cancers, and it was found that the results were inconsistent and inconclusive. Hence, in this study, a meta-analysis was conducted to assess the prognostic value of miR-9 in various types of tumors. Eligible studies were identified through a systematic search in PubMed and EMBASE and then were assessed by further quality evaluation. Pooled hazard ratios (HRs) with 95% confidence intervals for overall survival (OS) were calculated to investigate the association between miR-9 expression and cancer prognosis. The pooled results of eight published studies showed that elevated miR-9 was a predictor of poor survival of various carcinomas, with pooled HR of 3.04 (95% confidence interval: 1.96–4.73) for OS. Subgroup analysis on the basis of tumor type, sample size, and HR estimate also showed that high levels of miR-9 were also significantly correlated with OS. In addition, when the subgroup analyses were grouped by follow-up time, it was found that the elevated expression of miR-9 was associated with a lower long-term survival when the follow-up time was >60 months, but there was no correlation between the outcomes and those patients whose follow-up time was <60 months. Funnel plots and Egger’s tests revealed that there was no obvious publication bias risk in the meta-analysis. In conclusion, our results demonstrated that higher expression level of miR-9 significantly predicted worse OS in various carcinomas and that miR-9 may act as a novel biomarker in the prognosis of malignant neoplasms.

miR-199a-5p induces cell invasion by suppressing E-cadherin expression in cutaneous squamous cell carcinoma

A growing quantity of evidence exists to suggest that microRNAs are significant regulators of multiple cellular processes. When expressed aberrantly in different types of cancer, including cutaneous squamous cell carcinoma (cSCC), they play key roles in tumorigenesis and progression. The aberrant expression of miR-199a-5p has been observed to contribute to carcinogenesis in various types of cancer. However, the role of miR-199a-5p in the progression of cSCC metastasis remains largely unknown. In this study, we determined that miR-199a-5p was the upstream regulator of CDH1 (E-cadherin) and that it could suppress the expression of E-cadherin in cSCC cells. In addition, miR-199a-5p mimics significantly induced cell invasion and the activity of matrix metalloproteinase (MMP)2 and MMP9 in cSCC cells. In conclusion, these results are likely to aid in elucidating the molecular mechanisms of cSCC progression. In addition, the findings provide a new theoretical basis to further investigate miR-199a-5p as a potential biomarker and a promising approach in cSCC treatment.

Plasma exosomal miR-21 and miR-181a differentiates follicular from papillary thyroid cancer

Thyroid cancer (TC) is the most common endocrine malignancy and its incidence has increased over the last few decades. As has been revealed by a number of studies, TC tissue's micro-RNA (miRNA) profile may reflect histological features and the clinical behavior of tumor. However, alteration of the miRNA profile of plasma exosomes associated with TC development has to date not been explored. We isolated exosomes from plasma and assayed their characteristics using laser diffraction particle size analysis, atomic force microscopy, and western blotting. Next, we profiled cancer-associated miRNAs in plasma exosomes obtained from papillary TC patients, before and after surgical removal of the tumor. The diagnostic value of selected miRNAs was evaluated in a large cohort of patients displaying different statuses of thyroid nodule disease. MiRNA assessment was performed by RT-qPCR. In total, 60 patients with different types of thyroid nodal pathology were included in the study. Our results revealed that the development of papillary TC is associated with specific changes in exosomal miRNA profiles; this phenomenon can be used for differential diagnostics. MiRNA-31 was found to be over-represented in the plasma exosomes of patients with papillary TC vs. benign tumors, while miRNA-21 helped to distinguish between benign tumors and follicular TC. MiRNA-21 and MiRNA-181a-5p were found to be expressed reciprocally in the exosomes of patients with papillary and follicular TC, and their comparative assessment may help to distinguish between these types of TC with 100 % sensitivity and 77 % specificity.

Chemically induced skin carcinogenesis: Updates in experimental models (Review)

Skin cancer is one of the most common malignancies affecting humans worldwide, and its incidence is rapidly increasing. The study of skin carcinogenesis is of major interest for both scientific research and clinical practice and the use of in vivo systems may facilitate the investigation of early alterations in the skin and of the mechanisms involved, and may also lead to the development of novel therapeutic strategies for skin cancer. This review outlines several aspects regarding the skin toxicity testing domain in mouse models of chemically induced skin carcinogenesis. There are important strain differences in view of the histological type, development and clinical evolution of the skin tumor, differences reported decades ago and confirmed by our hands‑on experience. Using mouse models in preclinical testing is important due to the fact that, at the molecular level, common mechanisms with human cutaneous tumorigenesis are depicted. These animal models resemble human skin cancer development, in that genetic changes caused by carcinogens and pro‑inflammatory cytokines, and simultaneous inflammation sustained by pro‑inflammatory cytokines and chemokines favor tumor progression. Drugs and environmental conditions can be tested using these animal models. keeping in mind the differences between human and rodent skin physiology.

The role of epigenetics and long noncoding RNA MIAT in neuroendocrine prostate cancer

Neuroendocrine prostate cancer (NEPC) is the most lethal prostatic neoplasm. NEPC is thought to originate from the transdifferentiation of AR-positive adenocarcinoma cells. We have previously shown that an epigenetic/noncoding interactome (ENI) orchestrates cancer cells' plasticity, thereby allowing the emergence of metastatic, drug-resistant neoplasms. The primary objective of this manuscript is to discuss evidence indicating that some components of the ENI (Polycomb genes, miRNAs) play a key role in NEPC initiation and progression. Long noncoding RNAs represent vast and largely unexplored component of the ENI. Their role in NEPC has not been investigated. We show preliminary evidence indicating that a lncRNA (MIAT) is selectively upregulated in NEPCs and might interact with Polycomb genes. Our results indicate that long noncoding RNAs can be exploited as new biomarkers and therapeutic targets for NEPC.

BMP-2 Induced Expression of PLCβ1 That is a Positive Regulator of Osteoblast Differentiation

Bone morphogenetic protein 2 (BMP-2) is a critical growth factor that directs osteoblast differentiation and bone formation. Phosphoinositide-phospholipase Cβ 1 (PLCβ1) plays a crucial role in the initiation of the genetic program responsible for muscle differentiation. Differentiation of C2C12 mouse myoblasts in response to insulin stimulation is characterized by a marked increase in nuclear PLCβ1. Here, the function of PLCβ1 in the osteogenic differentiation was investigated. Briefly, in C2C12 cells treated with BMP-2 we assist to a remarkable increase in PLCβ1 protein and mRNA expression. The data regarding the influence on differentiation demonstrated that PLCβ1 promotes osteogenic differentiation by up-regulating alkaline phosphatase (ALP). Moreover, PLCβ1 is present in the nuclear compartment of these cells and overexpression of a cytosolic-PLCβ1mutant (cyt-PLCβ1), which lacks a nuclear localization sequence, prevented the differentiation of C2C12 cells into osteocytes. Recent evidence indicates that miRNAs act as important post transcriptional regulators in a large number of processes, including osteoblast differentiation. Since miR-214 is a regulator of Osterix (Osx) which is an osteoblast-specific transcription factor that is needful for osteoblast differentiation and bone formation, we further investigated whether PLCβ1 could be a potential target of miR-214 in the control of osteogenic differentiation by gain- and loss- of function experiment. The results indicated that inhibition of miR-214 in C2C12 cells significantly enhances the protein level of PLCβ1 and promotes C2C12 BMP-2-induced osteogenesis by targeting PLCβ1.

RNA-binding protein Lin28 in cancer and immunity

The highly conserved RNA-binding protein, Lin28, is involved in many biological processes, including development, reprogramming, pluripotency, and metabolism. Importantly, Lin28 functions as an oncogene, promoting tumor progression and metastasis in various human cancers. Lin28 can regulate gene expression either by directly binding to mRNAs or by blocking microRNA biogenesis, and the underlying mechanisms include Let-7-dependent and Let-7-independent modes of action. Recent evidence shows that Lin28 also plays a fundamental role in immunity. The roles of Lin28 in disease are complex and require characterization of its physiological functions in cancer and immunological contexts. Here we review emerging information on the role of Lin28 in cancer and immunity and the molecular mechanisms it uses. We discuss our present knowledge of the system and highlight remaining mysteries related to the functions of this small RNA-binding protein. This knowledge may lead to Lin28 becoming a diagnostic marker for cancer or immune-related diseases and a possible therapeutic target.

A Repertoire of MicroRNAs Regulates Cancer Cell Starvation by Targeting Phospholipase D in a Feedback Loop That Operates Maximally in Cancer Cells

We report a negative feedback loop between the signaling protein phospholipase D (PLD), phosphatidic acid (PA), and a specific set of microRNAs (miRNAs) during nutrient starvation of breast cancer cells. We show that PLD expression is increased in four breast cancer cell lines and that hypoxia, cell overcrowding, and nutrient starvation for 3 to 6 h increase expression even further. However, after prolonged (>12-h) starvation, PLD levels return to basal or lower levels. The mechanism for this is as follows. First, during initial starvation, an elevated PA (the product of PLD enzymatic activity) activates mTOR and S6K, known to inhibit apoptosis, and enhances cell migration especially in post-epithelial-to-mesenchymal transition (post-EMT) cancer cells. Second, continued PA production in later starvation induces expression of PLD-targeting microRNA 203 (miR-203), miR-887, miR-3619-5p, and miR-182, which reduce PLD translation. We provide direct evidence for a feedback loop, whereby PLD induction upon starvation leads to PA, which induces expression of miRNAs, which in turn inhibits PLD2 translation. The physiological relevance for breast cancer cells is that as PA can activate cell invasion, then, due to the negative feedback, it can deprive mTOR and S6K of their natural activator. It can further prevent inhibition of apoptosis and allow cells to survive nutrient deprivation, which normal cells cannot do.

MicroRNA-378-mediated suppression of Runx1 alleviates the aggressive phenotype of triple-negative MDA-MB-231 human breast cancer cells

The Runx1 transcription factor, known for its essential role in normal hematopoiesis, was reported in limited studies to be mutated or associated with human breast tumor tissues. Runx1 increases concomitantly with disease progression in the MMTV-PyMT transgenic mouse model of breast cancer. Compelling questions relate to mechanisms that regulate Runx1 expression in breast cancer. Here, we tested the hypothesis that dysregulation of Runx1-targeting microRNAs (miRNAs) allows for pathologic increase of Runx1 during breast cancer progression. Microarray profiling of the MMTV-PyMT model revealed significant downregulation of numerous miRNAs predicted to target Runx1. One of these, miR-378, was inversely correlated with Runx1 expression during breast cancer progression in mice and in human breast cancer cell lines MCF7 and triple-negative MDA-MB-231 that represent early- and late-stage diseases, respectively. MiR-378 is nearly absent in MDA-MB-231 cells. Luciferase reporter assays revealed that miR-378 binds the Runx1 3' untranslated region (3'UTR) and inhibits Runx1 expression. Functionally, we demonstrated that ectopic expression of miR-378 in MDA-MB-231 cells inhibited Runx1 and suppressed migration and invasion, while inhibition of miR-378 in MCF7 cells increased Runx1 levels and cell migration. Depletion of Runx1 in late-stage breast cancer cells resulted in increased expression of both the miR-378 host gene PPARGC1B and pre-miR-378, suggesting a feedback loop. Taken together, our study identifies a novel and clinically relevant mechanism for regulation of Runx1 in breast cancer that is mediated by a PPARGC1B-miR-378-Runx1 regulatory pathway. Our results highlight the translational potential of miRNA replacement therapy for inhibiting Runx1 in breast cancer.

MicroRNA profiles in colorectal carcinomas, adenomas and normal colonic mucosa: variations in miRNA expression and disease progression

Roughly 27% of miRNAs are commonly expressed in colonic tissue; of these, over 86% are dysregulated between carcinoma and normal tissue when applying a false discovery rate of 0.05. MiRNA expression from normal to adenoma to carcinoma varied by miRNA and its frequency of expression in the population.

MiRNAs are small, non-protein-coding RNA molecules that regulate gene expression either by post-transcriptionally suppressing mRNA translation or by mRNA degradation. We examine differentially expressed miRNAs in colorectal carcinomas, adenomas and normal colonic mucosa. Data come from population-based studies of colorectal cancer conducted in Utah and the Kaiser Permanente Medical Care Program. A total of 1893 carcinoma/normal-paired samples and 290 adenoma tissue samples were run on the Agilent Human miRNA Microarray V19.0 which contained 2006 miRNAs. We tested for significant differences in miRNA expression between paired carcinoma/adenoma/normal colonic tissue samples. Fewer than 600 miRNAs were expressed in >80% of people for colonic tissue; of these 86.5% were statistically differentially expressed between carcinoma and normal colonic mucosa using a false discovery rate of 0.05. Roughly half of these differentially expressed miRNAs showed a progression in levels of expression from normal to adenoma to carcinoma tissue. Other miRNAs appeared to be altered at the normal to adenoma stage, while others were only altered at the adenoma to carcinoma stage or only at the normal to carcinoma stage. Evaluation of the Agilent platform showed a high degree of repeatability (r = 0.98) and reasonable agreement with the NanoString platform. Our data suggest that miRNAs are highly dysregulated in colorectal tissue among individuals with colorectal cancer; the pattern of disruption varies by miRNA as tissue progresses from normal to adenoma to carcinoma.

MicroRNAs as potential diagnostic and prognostic biomarkers in melanoma

Melanoma is a life-threatening malignancy with poor prognosis and a relatively high burden of mortality in advanced stages. The efficacy of current available therapeutic strategies is limited, with a survival rate of less than 10%. Despite rapid advances in biomarker-guided drug development in different tumour types, including melanoma, only a very small number of biomarkers have been identified. Recently, microRNAs (miRNAs) have emerged as a molecular regulator in the development and progression of melanoma. Aberrant activation of some known miRNAs, e.g. let-7a and b, miR-148, miR-155, miR-182, miR-200c, miR-211, miR-214, miR-221 and 222, has been recognised to be linked with melanoma-associated genes such as NRAS, microphthalmia-associated transcription factor, receptor tyrosine kinase c-KIT, AP-2 transcription factor, etc. There is accumulating evidence suggesting the potential impact of circulating miRNAs as diagnostic and therapeutic markers in diseases. In addition, miRNAs have turned out to play important roles in drug-resistance mechanisms; suggesting their modulation as a potential approach to overcome chemoresistance. This review highlights recent preclinical and clinical studies on circulating miRNAs and their potential role as diagnosis, and therapeutic targets in melanoma.

Deep sequencing of small RNA libraries from human prostate epithelial and stromal cells reveal distinct pattern of microRNAs primarily predicted to target growth factors

Complex epithelial and stromal cell interactions are required during the development and progression of prostate cancer. Regulatory small non-coding microRNAs (miRNAs) participate in the spatiotemporal regulation of messenger RNA (mRNA) and regulation of translation affecting a large number of genes involved in prostate carcinogenesis. In this study, through deep-sequencing of size fractionated small RNA libraries we profiled the miRNAs of prostate epithelial (PrEC) and stromal (PrSC) cells. Over 50 million reads were obtained for PrEC in which 860,468 were unique sequences. Similarly, nearly 76 million reads for PrSC were obtained in which over 1 million were unique reads. Expression of many miRNAs of broadly conserved and poorly conserved miRNA families were identified. Sixteen highly expressed miRNAs with significant change in expression in PrSC than PrEC were further analyzed in silico. ConsensusPathDB showed the target genes of these miRNAs were significantly involved in adherence junction, cell adhesion, EGRF, TGF-β and androgen signaling. Let-7 family of tumor-suppressor miRNAs expression was highly pervasive in both, PrEC and PrSC cells. In addition, we have also identified several miRNAs that are unique to PrEC or PrSC cells and their predicted putative targets are a group of transcription factors. This study provides perspective on the miRNA expression in PrEC and PrSC, and reveals a global trend in miRNA interactome. We conclude that the most abundant miRNAs are potential regulators of development and differentiation of the prostate gland by targeting a set of growth factors. Additionally, high level expression of the most members of let-7 family miRNAs suggests their role in the fine tuning of the growth and proliferation of prostate epithelial and stromal cells.

Novel roles of androgen receptor, epidermal growth factor receptor, TP53, regulatory RNAs, NF-kappa-B, chromosomal translocations, neutrophil associated gelatinase, and matrix metalloproteinase-9 in prostate cancer and prostate cancer stem cells

Approximately one in six men will be diagnosed with some form of prostate cancer in their lifetime. Over 250,000 men worldwide die annually due to complications from prostate cancer. While advancements in prostate cancer screening and therapies have helped in lowering this statistic, better tests and more effective therapies are still needed. This review will summarize the novel roles of the androgen receptor (AR), epidermal growth factor receptor (EGFR), the EGFRvIII variant, TP53, long-non-coding RNAs (lncRNAs), microRNAs (miRs), NF-kappa-B, chromosomal translocations, neutrophil associated gelatinase, (NGAL), matrix metalloproteinase-9 (MMP-9), the tumor microenvironment and cancer stem cells (CSC) have on the diagnosis, development and treatment of prostate cancer.

MiR-199a/b-3p suppresses migration and invasion of breast cancer cells by downregulating PAK4/MEK/ERK signaling pathway

MicroRNA-199a/b-3p is downregulated in several types of aggressive cancer, and its decrement significantly correlates with poor survival. Here, we aim to investigate the biological function of miR-199a/b-3p and its regulation of target genes in breast cancer cells with highly metastatic potential. In addition, we found that miR-199a/b-3p expression was much lower in MDA-MB-231, CAL120, and HCC1395 breast cancer cells with highly metastatic potential. Functional assays showed that restored miR-199a/b-3p expression inhibited MDA-MB-231 cell growth, cell-cycle progression, migration, and invasion. In addition, we experimentally demonstrated that PAK4 was the direct target of miR-199a/b-3p, hypo-expression of PAK4 suppressed proliferation, migration and invasion of MDA-MB-231 cells, and overexpression of PAK4 significantly rescued the inhibitory effect of miR-199a/b-3p on MDA-MB-231 cell growth, migration, and invasion. Further, we also observed that miR-199a/b-3p could inactivate the PAK4/MEK/ERK signaling pathway. Thus, miR-199a/b-3p functions as a tumor suppressor and has an important role in breast cancer metastasis through PAK4/MEK/ERK signaling pathway.

RBMMMDA: predicting multiple types of disease-microRNA associations

Accumulating evidences have shown that plenty of miRNAs play fundamental and important roles in various biological processes and the deregulations of miRNAs are associated with a broad range of human diseases. However, the mechanisms underlying the dysregulations of miRNAs still have not been fully understood yet. All the previous computational approaches can only predict binary associations between diseases and miRNAs. Predicting multiple types of disease-miRNA associations can further broaden our understanding about the molecular basis of diseases in the level of miRNAs. In this study, the model of Restricted Boltzmann machine for multiple types of miRNA-disease association prediction (RBMMMDA) was developed to predict four different types of miRNA-disease associations. Based on this model, we could obtain not only new miRNA-disease associations, but also corresponding association types. To our knowledge, RBMMMDA is the first model which could computationally infer association types of miRNA-disease pairs. Leave-one-out cross validation was implemented for RBMMMDA and the AUC of 0.8606 demonstrated the reliable and effective performance of RBMMMDA. In the case studies about lung cancer, breast cancer, and global prediction for all the diseases simultaneously, 50, 42, and 45 out of top 100 predicted miRNA-disease association types were confirmed by recent biological experimental literatures, respectively.

Physicochemical and biological characterization of chitosan-microRNA nanocomplexes for gene delivery to MCF-7 breast cancer cells

Cancer gene therapy requires the design of non-viral vectors that carry genetic material and selectively deliver it with minimal toxicity. Non-viral vectors based on cationic natural polymers can form electrostatic complexes with negatively-charged polynucleotides such as microRNAs (miRNAs). Here we investigated the physicochemical/biophysical properties of chitosan-hsa-miRNA-145 (CS-miRNA) nanocomplexes and the biological responses of MCF-7 breast cancer cells cultured in vitro. Self-assembled CS-miRNA nanocomplexes were produced with a range of (+/-) charge ratios (from 0.6 to 8) using chitosans with various degrees of acetylation and molecular weight. The Z-average particle diameter of the complexes was <200 nm. The surface charge increased with increasing amount of chitosan. We observed that chitosan induces the base-stacking of miRNA in a concentration dependent manner. Surface plasmon resonance spectroscopy shows that complexes formed by low degree of acetylation chitosans are highly stable, regardless of the molecular weight. We found no evidence that these complexes were cytotoxic towards MCF-7 cells. Furthermore, CS-miRNA nanocomplexes with degree of acetylation 12% and 29% were biologically active, showing successful downregulation of target mRNA expression in MCF-7 cells. Our data, therefore, shows that CS-miRNA complexes offer a promising non-viral platform for breast cancer gene therapy.

Experimental procedures to identify and validate specific mRNA targets of miRNAs

Functionally matured microRNAs (miRNAs) are small single-stranded non-coding RNA molecules which are emerging as important post-transcriptional regulators of gene expression and consequently are central players in many physiological and pathological processes. Since the biological roles of individual miRNAs will be dictated by the mRNAs that they regulate, the identification and validation of miRNA/mRNA target interactions is critical for our understanding of the regulatory networks governing biological processes. We promulgate the combined use of prediction algorithms, the examination of curated databases of experimentally supported miRNA/mRNA interactions, manual sequence inspection of cataloged miRNA binding sites in specific target mRNAs, and review of the published literature as a reliable practice for identifying and prioritizing biologically important miRNA/mRNA target pairs. Once a preferred miRNA/mRNA target pair has been selected, we propose that the authenticity of a functional miRNA/mRNA target pair be validated by fulfilling four well-defined experimental criteria. This review summarizes our current knowledge of miRNA biology, miRNA/mRNA target prediction algorithms, validated miRNA/mRNA target data bases, and outlines several experimental methods by which miRNA/mRNA targets can be authenticated. In addition, a case study of human endoglin is presented as an example of the utilization of these methodologies.

miR-155 is involved in Alzheimer's disease by regulating T lymphocyte function

Alzheimer’s disease (AD) is considered the most common cause of sporadic dementia. In AD, adaptive and innate immune responses play a crucial role in clearance of amyloid beta and maintenance of cognitive functions. In addition to other changes in the immune system, AD alters the T-cell responses that affect activation of glial cells, neuronal cells, macrophages, and secretion of pro-inflammatory cytokines. These changes in the immune system influence AD pathogenesis. Micro-RNA (miRNA)-155 is a multifunctional miRNA with a distinct expression profile. It is involved in diverse physiological and pathological mechanisms, such as immunity and inflammation. Recent studies indicate that miR-155 regulates T-cell functions during inflammation. In this article, we summarize recent studies describing the therapeutic potential of miR-155 via regulation of T cells in AD. Further, we propose that regulation of miR-155 might be a new protective approach against AD pathogenesis.

MicroRNAs and oncolytic viruses

MicroRNAs regulate gene expression in mammalian cells and often exhibit tissue-specific expression patterns. Incorporation of microRNA target sequences can be used to control exogenous gene expression and viral tropism in specific tissues to enhance the therapeutic indices of oncolytic viruses expressing therapeutic transgenes. Continued development of this targeting strategy has resulted in the generation of unattenuated oncolytic viruses with enhanced potency, broad species-tropisms and reduced off-target toxicities in multiple-tissues simultaneously. Furthermore, oncolytic viruses have been used to enhance the delivery, duration and therapeutic efficacy of microRNA-based therapeutics designed to either restore or inhibit the function of dysregulated microRNAs in cancer cells. Recent efforts focused on combining oncolytic virotherapy and microRNA regulation have generated increasingly potent and safe cancer therapeutics.

Epigenetic mechanisms and therapeutic targets of chemotherapy resistance in epithelial ovarian cancer

Epithelial ovarian cancer is the most lethal gynaecological cancer with the majority of patients succumbing to chemotherapy-resistant disease. Unravelling the mechanisms of drug resistance and how it can be prevented or reversed is a pivotal challenge in the treatment of cancer. Epigenetic mechanisms appear to play a crucial role in the development of inherent and acquired resistance in ovarian cancer. Aberrant epigenetic states can be reversed by drug therapy, and thus maintenance of epigenetic change is a potential target to halt or reverse chemotherapy resistance. This review explores the evidence that demonstrates that DNA methylation, histone modification, and microRNAs are associated with inherent and acquired chemotherapy resistance in ovarian cancer and the current challenges associated with this. We also explore current epigenetic therapies used in patients with drug-resistant ovarian cancer and future potential targets.

Role of host microRNAs in Kaposi's sarcoma-associated herpesvirus pathogenesis

MicroRNAs (miRNAs) are small non-coding RNA species that can bind to both untranslated and coding regions of target mRNAs, causing their degradation or post-transcriptional modification. Currently, over 2500 miRNAs have been identified in the human genome. Burgeoning evidence suggests that dysregulation of human miRNAs can play a role in the pathogenesis of a variety of diseases, including cancer. In contrast, only a small subset of human miRNAs has been functionally validated in the pathogenesis of oncogenic viruses, in particular, Kaposi’s sarcoma-associated herpesvirus (KSHV). KSHV is the etiologic agent of several human cancers, such as primary effusion lymphoma (PEL) and Kaposi’s sarcoma (KS), which are mostly seen in acquired immune deficiency syndrome (AIDS) patients or other immuno-suppressed subpopulation. This review summarizes recent literature outlining mechanisms for KSHV/viral proteins regulation of cellular miRNAs contributing to viral pathogenesis, as well as recent findings about the unique signature of miRNAs induced by KSHV infection or KSHV-related malignancies.