MicroRNAs in colorectal cancer: translation of molecular biology into clinical application

miR-125a-3p/FUT5-FUT6 axis mediates colorectal cancer cell proliferation, migration, invasion and pathological angiogenesis via PI3K-Akt pathway

The fucosyltransferase (FUT) family produces glycans, a fundamental event in several cancers, including colorectal cancer (CRC). miR-125a-3p is a non-coding RNA that can reduce cell proliferation and migration in cancer. In this study, we explored the levels of miR-125a-3p and FUT expression in human CRC tissues and two human CRC cell lines by qPCR. The results showed that miR-125a-3p, FUT5 and FUT6 are differentially expressed in normal and tumour tissues. On the basis of our previous research, FUT can be regulated by miRNA, which influences the proliferation and invasion of breast and hepatocellular cancer cells. We hypothesised that FUT5 and FUT6 may be regulated by miR-125a-3p. Luciferase reporter analyses were applied to identify potential target genes of miR-125a-3p. A functional study showed that miR-125a-3p overexpression can inhibit the proliferation, migration, invasion and angiogenesis of CRC cells via down-regulating FUT5 and FUT6. In addition, regulating miR-125a-3p, FUT5 or FUT6 expression markedly modulated the activity of the PI3K/Akt signalling pathway, and this effect of FUT5 or FUT6 could be reversed by transfection with miR-125a-3p-mimics. Taken together, our data suggest that both FUT5 and FUT6 can promote the development of CRC via the PI3K/Akt signalling pathway, which is regulated by miR-125a-3p. miR-125a-3p may serve as a predictive biomarker and a potential therapeutic target in CRC treatment.

Involvement of Non-coding RNAs in the Signaling Pathways of Colorectal Cancer

Colorectal cancer (CRC) is one of the most common diagnosed cancers worldwide. The metastasis and development of resistance to anti-cancer treatment are major challenges in the treatment of CRC. Understanding mechanisms underpinning the pathogenesis is therefore critical in developing novel agents for CRC treatments. A large number of evidence has demonstrated that non-coding RNAs (ncRNAs), including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs have functional roles in both the physiological and pathological processes by regulating the expression of their target genes. These molecules are engaged in the pathobiology of neoplastic diseases and are targets for the diagnosis, prognosis and therapy of a variety of cancers, including CRC. In this regard, ncRNAs have emerged as one of the hallmarks of CRC pathogenesis and they also play key roles in metastasis, drug resistance and the stemness of CRC stem cell by regulating various signaling networks. Therefore, a better understanding the ncRNAs involved in the signaling pathways of CRC may lead to the development of novel strategy for diagnosis, prognosis and treatment of CRC. In this chapter, we summarize the latest findings on ncRNAs, with a focus on miRNAs and lncRNAs involving in signaling networks and in the regulation of pathogenic signaling pathways in CRC.

Non-coding RNAs as Biomarkers for Colorectal Cancer Screening and Early Detection

Early detection of colorectal cancer (CRC) is the key for prevention and the ability to impact long-term survival of CRC patients. Current CRC screening modalities are inadequate for global application because of low sensitivity and specificity in case of conventional stool-based screening tests, and high costs and a low participation compliance in colonoscopy. An accurate stool- or blood-based screening test with use of innovative biomarkers is an appealing alternative as it is non-invasive and poses minimal risk to patients. It is easy to perform, can be repeated at shorter intervals, and therefore would likely lead to a much higher compliance rates. Non-coding RNAs (ncRNAs) have recently gained attention because of their involvement in different biological processes, such as proliferation, differentiation, migration, angiogenesis and apoptosis. An increasing number of studies have demonstrated that mutations or abnormal expression of ncRNAs are closely associated with various cancers, including CRC. The discovery that ncRNAs (mainly microRNAs) are stable in stool and in blood plasma and serum presents the opportunity to develop novel strategies taking advantage of circulating ncRNAs as early diagnostic biomarkers of CRC. This chapter is a comprehensive examination of aberrant ncRNAs expression levels in tumor tissue, stool and blood of CRC patients and a summary of the current findings on ncRNAs, including microRNAs, small nucleolar RNAs, small nuclear RNAs, Piwi-interacting RNAs, circular RNAs and long ncRNAs in regards to their potential usage for screening or early detection of CRC.

Nutrient-Gene Interaction in Colon Cancer, from the Membrane to Cellular Physiology

The International Agency for Research on Cancer recently released an assessment classifying red and processed meat as "carcinogenic to humans" on the basis of the positive association between increased consumption and risk for colorectal cancer. Diet, however, can also decrease the risk for colorectal cancer and be used as a chemopreventive strategy. Bioactive dietary molecules, such as n-3 polyunsaturated fatty acids, curcumin, and fermentable fiber, have been proposed to exert chemoprotective effects, and their molecular mechanisms have been the focus of research in the dietary/chemoprevention field. Using these bioactives as examples, this review surveys the proposed mechanisms by which they exert their effects, from the nucleus to the cellular membrane. In addition, we discuss emerging technologies involving the culturing of colonic organoids to study the physiological effects of dietary bioactives. Finally, we address future challenges to the field regarding the identification of additional molecular mechanisms and other bioactive dietary molecules that can be utilized in our fight to reduce the incidence of colorectal cancer.

MicroRNA-552 promotes tumor cell proliferation and migration by directly targeting DACH1 via the Wnt/β-catenin signaling pathway in colorectal cancer

The purpose of the present study was to analyze the crucial role of microRNAs (miRNAs/miRs) involved in the proliferation and migration of colorectal cancer (CRC) and to investigate their underlying mechanisms. The present study discusses the expression and function of miR-552 in CRC. The expression level of miR-552 in CRC cells and tissues was observed, and it was suggested that the high expression of miR-552 accelerated the proliferation and migration of CRC cells in vitro. Notably, a result of the present study was that the cell fate determination factor Dachshund family transcription factor 1 (DACH1) was identified as a direct target of miR-552. Suppressing miR-552 expression in CRC cells increased endogenous DACH1 mRNA and protein levels, which was negatively correlated with miR-552. DACH1 performs an important role in the development of a number of neoplasms, and has the ability to regulate the Wnt/β-catenin signaling pathway as a novel predictive and diagnostic biomarker. Accordingly, it was concluded that miR-552 exerted a tumor-promoting role in CRC development by targeting DACH1, which may contribute to the increase in the rates of CRC proliferation and migration. miR-552 may serve as a potential diagnostic and prognostic biomarker for CRC.

MicroRNA-136 inhibits colon cancer cell proliferation and invasion through targeting liver receptor homolog-1/Wnt signaling

An increasing number of studies have reported that microRNAs (miRNAs) are involved in the malignant behavior of colon cancer cells through directly targeting multiple tumor suppressors or oncogenes. The expression and role of miR-136 has been reported in several types of human cancer. However, the role of miR-136 in colon cancer remains unclear. In this study, we aimed to investigate the expression and function of miR-136 in colon cancer and the potential underlying mechanism. Here, we found that miR-136 was decreased in colon cancer cell lines and tissues. Overexpression of miR-136 inhibited the proliferation and invasion in SW480 and HCT116 cell lines while suppression of miR-136 exhibited the opposite effect. Liver receptor homolog-1 (LRH-1) was identified as a direct target gene of miR-136. Notably, miR-136 overexpression suppressed LRH-1 expression as well as Wnt signaling in SW480 and HCT116 cell lines. The miR-136 expression level inversely correlated with LRH-1 mRNA expression in colon cancer specimens. Moreover, overexpression of LRH-1 partially reversed the miR-136-induced antitumor effect in SW480 and HCT116 cell lines. Taken together, these findings suggest that miR-136 functions as a negative regulator in colon cancer progression by targeting LRH-1 and that miR-136 downregulation contributes to high expression of LRH-1 and aberrant activation of Wnt signaling, leaving open the possibility that miR-136 may serve as a potential therapeutic target for colon cancer.

Exosome-encapsulated microRNAs as circulating biomarkers for colorectal cancer

Currently available studies have suggested that a number of exosome-encapsulated microRNAs (miRNAs) are recognized as stable biomarkers for cancers. However, little is known about the effect of exosomal miRNAs on colorectal cancer (CRC). The aim of study is to identify specific miRNAs in serum exosomes, which may serve as potential diagnostic and prognostic biomarkers and therapeutic targets for CRC. Microarray analyses of miRNAs in serum exosomes from 3 primary CRC patients and 3 healthy controls were performed. Those differentially expressed exosome-encapsulated miRNAs were verified in exosome-enriched serum samples from 77 CRC patients and 20 healthy controls by quantitative real-time PCR (qRT-PCR). A total of 39 aberrantly expressed miRNAs in serum exosomes were identified by microarray analysis. After confirmation by qRT-PCR, we found that 5 exosome-encapsulated miRNAs (miR-638, miR-5787, miR-8075, miR-6869-5p and miR-548c-5p) were significantly down-regulated, while 2 exosome-encapsulated miRNAs (miR-486-5p and miR-3180-5p) were significantly up-regulated in serum. Decreased levels of miR-638 in serum exosomes were associated with increased risk of liver metastasis and later TNM stage of CRC. Networks analyses revealed that 5 aberrantly expressed miRNAs (miR-638, miR-5787, miR-8075, miR-6869-5p, and miR-548c-5p) might be involved in the process of glucose metabolism in CRC. The present study shows the specific serum profile of exosome-encapsulated miRNAs in CRC. Those specific miRNAs in serum exosomes may serve as disease biomarkers and novel therapeutic targets for CRC.

Identification of potential long non-coding RNA biomarkers associated with the progression of colon cancer

Increasing evidence has suggested that dysregulated lncRNA expression played important roles in the development and progression of human cancers. Although prognostic roles of lncRNAs have been recognized for colon cancer (CC) patients, the search for novel lncRNA biomarkers potentially involved in CC progression is an urgent and still largely unmet medical need. In this study, we evaluated the lncRNA expression changes during the progression of CC by analyzing two cohorts of previously published expression profiles of CC patients and identified hundreds of differentially expressed lncRNAs. Then we identified eight lncRNAs that closely associated with the progression of CC patients from a large number of significantly altered lncRNAs using random forest supervised classification algorithm. Finally, an SVM-based lncRNA risk classifier was developed to discriminate high-risk CC patients from persons with early-stage and validated in both the training dataset and testing dataset by survival analysis and five-fold cross-validation strategy. Our pathway enrichment analysis based on protein-coding genes that are co-expressed with lncRNAs, suggested that variation in expression of eight lncRNAs biomarkers might affect critical pathways involved in CC progression. With further validation, these eight lncRNAs might have significant implications for the clinical management of CC patients with early stage and improve our understanding of cancer progression.

Colorectal Cancer: From the Genetic Model to Posttranscriptional Regulation by Noncoding RNAs

Colorectal cancer is the third most common form of cancer in developed countries and, despite the improvements achieved in its treatment options, remains as one of the main causes of cancer-related death. In this review, we first focus on colorectal carcinogenesis and on the genetic and epigenetic alterations involved. In addition, noncoding RNAs have been shown to be important regulators of gene expression. We present a general overview of what is known about these molecules and their role and dysregulation in cancer, with a special focus on the biogenesis, characteristics, and function of microRNAs. These molecules are important regulators of carcinogenesis, progression, invasion, angiogenesis, and metastases in cancer, including colorectal cancer. For this reason, miRNAs can be used as potential biomarkers for diagnosis, prognosis, and efficacy of chemotherapeutic treatments, or even as therapeutic agents, or as targets by themselves. Thus, this review highlights the importance of miRNAs in the development, progression, diagnosis, and therapy of colorectal cancer and summarizes current therapeutic approaches for the treatment of colorectal cancer.

Association between the expression of microRNAs and the response of patients with locally advanced rectal cancer to preoperative chemoradiotherapy

Preoperative chemoradiotherapy (CRT) followed by mesorectal excision is the standard treatment for patients with locally advanced rectal cancer (LARC). The balance between treatment efficacy and toxicity is a major issue in the clinical management of these patients. There is a requirement for the identification of predictive molecular biomarkers for the response of patients to CRT. The present study aimed to analyze the association between microRNA (miRNA/miR) expression and treatment efficacy in patients with LARC who were treated with preoperative CRT. From previous clinical trials, 55 patients for the test cohort and 130 patients for the validation cohort met the criteria for the present investigation. Through reverse transcription-quantitative polymerase chain reaction analysis, the expression of miR-21, −31, −125b, −145 and −630 in the diagnostic biopsies was analyzed. The primary endpoint of tumor regression was evaluated according to Mandard's Tumor Regression Grade (TRG) system. In the test cohort, a significant association was identified between low miRNA-145 expression and TRG1+2 (P=0.0003). Similarly, this association was identified in the validation cohort, although it did not reach statistical significance. Furthermore, a significant association between high miRNA-21 expression and TRG1+2 (P=0.035) was observed in the validation cohort. The remaining miRNAs analyzed were not associated with TRG. The results of the present study highlight the clinical importance of miRNAs in LARC and underline the necessity for validation studies in this setting.

Genetic Association of Hematopoietic Stem Cell Transplantation Outcome beyond Histocompatibility Genes

The outcome of hematopoietic stem cell transplantation (HSCT) is controlled by genetic factors among which the leukocyte antigen human leukocyte antigen (HLA) matching is most important. In addition, minor histocompatibility antigens and non-HLA gene polymorphisms in genes controlling immune responses are known to contribute to the risks associated with HSCT. Besides single-nucleotide polymorphisms (SNPs) in protein coding genes, SNPs in regulatory elements such as microRNAs (miRNAs) contribute to these genetic risks. However, genetic risks require for their realization the expression of the respective gene or miRNA. Thus, gene and miRNA expression studies may help to identify genes and SNPs that indeed affect the outcome of HSCT. In this review, we summarize gene expression profiling studies that were performed in recent years in both patients and animal models to identify genes regulated during HSCT. We discuss SNP–mRNA–miRNA regulatory networks and their contribution to the risks associated with HSCT in specific examples, including forkheadbox protein 3 and regulatory T cells, the role of the miR-155 and miR-146a regulatory network for graft-versus-host disease, and the function of MICA and its receptor NKG2D for the outcome of HSCT. These examples demonstrate how SNPs affect expression or function of proteins that modulate the alloimmune response and influence the outcome of HSCT. Specific miRNAs targeting these genes and directly affecting expression of mRNAs are identified. It might be valuable in the future to determine SNPs and to analyze miRNA and mRNA expression in parallel in cohorts of HSCT patients to further elucidate genetic risks of HSCT.

Genome-wide two-locus interaction analysis identifies multiple epistatic SNP pairs that confer risk of prostate cancer: A cross-population study

Prostate cancer is one of the most common carcinomas among adult males. Recently, genome-wide association studies (GWAS) have identified several susceptibility genes of prostate cancer. However, these single locus results can only explain a small proportion of the genetic etiology. In order to understand how multiple genetic variants may contribute to the penetrance of prostate cancer, we conducted a genome-wide SNP-SNP interaction study in four populations, involving 5,269 cases and 5,289 controls. We exhaustively evaluated all pairs of SNP-SNP interactions for 661,658 SNPs that were consensus in all four groups, and then performed a meta-analysis to combine the results. We found multiple variants within region 7p21.3 and 18p11.22 significantly interacted with each other and reached genome-wide significance levels. The most significant epistasis was between rs1105255 (intergenic, near RBSG3) and rs651431 (intergenic, near VAPA) (p = 1.4 × 10^-14 ). Notably, VAPA was identified to be the protein-coding transcripts as PTEN competing endogenous RNA in prostate cancer. And PTEN is a critical tumor suppressor gene frequently altered in cancers. In addition, 7p21.3 involves several pseudogenes, whose parental genes are cancer-related. Recently, growing evidence strongly suggests they are of multifaceted involvements in the pathogenesis of cancer. Multiple regulatory elements were found within 7p21.3 and 18p11.22, indicating the variants might regulate the nearby genes and confer risk of disease. Additionally, we also found several other significant epistasis, most of which were near or in cancer-related genes. Drug target enrichment analysis suggested genes in top epistasis significantly overlapped with target genes of FDA-approved drugs for treatment of prostate cancer.

miR-10b Inhibits Apoptosis and Promotes Proliferation and Invasion of Endometrial Cancer Cells via Targeting HOXB3

MicroRNAs are small RNA that are tightly interrelated with the initiation, development, and metastasis of cancers. Studies have shown that miR-10b is increased in various cancers. However, the underlying mechanisms of miR-10b in the occurrence and metastasis of endometrial cancer are poorly understood. To investigate its roles and correlations with Homeobox box 3 (HOXB3) in endometrial cancer, cancer tissues and adjacent normal endometrium tissues from 20 patients with endometrial cancer were studied. miR-10b expression was significantly up-regulated (p < 0.01) in endometrial cancer tissue, whereas HOXB3 was lowly expressed. The silence of miR-10b resulted in significantly enhanced cell apoptosis, and remarkably reduced cell proliferation, migration, and invasion (p < 0.05). Moreover, the protein levels of HOXB3 were increased in KLE cells with silenced miR-10b, and dual-luciferase reporter assay suggested that miR-10b could directly target HOXB3. Furthermore, overexpression of HOXB3 promoted cell apoptosis but inhibited cell proliferation, migration, and invasion (p < 0.01). To conclude, miR-10b might control cell apoptosis, proliferation, migration, and invasion in endometrial cancer via regulation of HOXB3 expression.

Effect of evodiamine and berberine on the interaction between DNMTs and target microRNAs during malignant transformation of the colon by TGF-β1

The tissue microenvironment functions as a crucial player in carcinogenesis, and transforming growth factor-β1 (TGF-β1) within the microenvironment stimulates the formation of neoplasms. Using an in vitro model of malignancy induced by TGF-β1, we assessed the effect of evodiamine and berberine on the interaction between DNA methyltransferases (DNMTs) and target microRNAs (miRNAs) in the model. Colon tissues from neonatal rats 7 days of age were cultured and malignancy was induced by TGF-β1 in vitro for 48 h, and then the tissues were respectively treated with evodiamine and berberine for 24 h. Morphological alteration of tissues was observed by an inverted microscope, histological structures were observed using hematoxylin and eosin staining, and the expression levels of DNMTs and targeted miRNAs screened by bioinformatics software combined with Gene chip analysis in our previous study were detected by immunohistochemistry and quantified by real-time PCR. Twenty-four hours after treatment with TGF-β1, expression levels of DNMT1, DNMT3A, DNMT3B and miR-152 (target DNMT1), miR-429 (target DNMT3A) and miR-29a (target DNMT3A/3B) were markedly decreased; however, after 48 h, the expression levels of DNMT1 and DNMT3A were significantly increased, but their target miRNAs were still decreased. After treatment with a DNMT inhibitor (5-Aza-dC), expression levels of the miRNAs were increased to a larger extent, but did not reach normal levels. After treatment with berberine and evodiamine for 24 h, respectively, increased expression of DNMT1, DNMT3A, DNMT3B and miR-152, miR-429, miR-29a was noted. In conclusion, the results of the present study suggest that miRNAs can also be post-transcriptionally regulated by their corresponding DNMTs and that berberine and evodiamine regulate the expression of these genes, which provides early epigenetic evidence for the prevention and therapy of colorectal cancer.

Methyl jasmonate induces the apoptosis of human colorectal cancer cells via downregulation of EZH2 expression by microRNA‑101

Methyl jasmonate is found universally in the plant kingdom and functions to regulate plant growth and development, as well as in stress responses through signal transduction pathways. The present study aimed to investigate the anticancer effect of methyl jasmonate on SW620 human colorectal cancer cells and its potential underlying mechanism. SW620 cells were treated with 0, 0.5, 0.75, 1.5 and 2.0 mM methyl jasmonate for 12, 24 and 48 h. Methyl jasmonate was shown to be able to inhibit cell growth and induce apoptosis of SW620 cells in a concentration and time‑dependent manner, whilst promoting an increase in caspase‑3 protein expression. Compared with control, the anticancer effect of methyl jasmonate inhibited Enhancer of zeste homolog 2 (EZH2) protein expression and activated microRNA (miR)‑101 expression in SW620 cells. However, knockdown of miR‑101 suppresses methyl jasmonate‑induced cell growth inhibition, activation of caspase‑3 expression and inhibition of EZH2 expression in SW620 cells. These results demonstrate that methyl jasmonate induced the apoptosis of human colorectal cancer cells via downregulation of EZH2 expression by miR‑101.

MicroRNA-320a downregulation mediates human liver cancer cell proliferation through the Wnt/β-catenin signaling pathway

MicroRNAs (miRs) have emerged as key epigenetic regulators involved in cancer progression. miR-320a has been demonstrated to be a novel tumor suppressive microRNA in several types of cancers. In the present study, the role of miR-320a in human hepatocellular carcinoma (HCC) was investigated. The expression levels of miR-320a and messenger RNA were determined by reverse transcription-quantitative polymerase chain reaction, while cell cycle and cell apoptosis were analyzed by flow cytometry. The cell proliferative ability was determined by Cell Counting Kit-8 assay and colony formation assay. The downstream target of miR-320a was confirmed by luciferase reporter assay, while the protein levels were measured by western blotting. The results revealed that miR-320a was inversely associated with HCC proliferation in HCC cell lines. Functional studies demonstrated that miR-320a significantly decreased the capability of cell proliferation and induced G₀/G₁ growth arrest in vitro. In addition, β-catenin was identified as one of the direct targets of miR-320a, downregulating the expression level of β-catenin, c-myc, cyclin D1 and dickkopf-1. In conclusion, miR-320a may act as a tumor-suppressive microRNA through targeting β-catenin in HCC.

miR-155 Regulated Inflammation Response by the SOCS1-STAT3-PDCD4 Axis in Atherogenesis

Inflammation response plays a critical role in all phases of atherosclerosis (AS). Increased evidence has demonstrated that miR-155 mediates inflammatory mediators in macrophages to promote plaque formation and rupture. However, the precise mechanism of miR-155 remains unclear in AS. Here, we also found that miR-155 and PDCD4 were elevated in the aortic tissue of atherosclerotic mice and ox-LDL treated RAW264.7 cells. Further studies showed that miR-155 not only directly inhibited SOCS1 expression, but also increased the expression of p-STAT and PDCD4, as well as the production of proinflammation mediators IL-6 and TNF-α. Downregulation of miR-155 and PDCD4 and upregulation of SOCS1 obviously decreased the IL-6 and TNF-α expression. In addition, inhibition of miR-155 levels in atherosclerotic mice could notably reduce the IL-6 and TNF-α level in plasma and aortic tissue, accompanied with increased p-STAT3 and PDCD4 and decreased SOCS1. Thus, miR-155 might mediate the inflammation in AS via the SOCS1-STAT3-PDCD4 axis. These results provide a rationale for intervention of intracellular miR-155 as possible antiatherosclerotic targets.

Molecular mechanisms underlying application of serum procalcitonin and stool miR-637 in prognosis of acute ischemic stroke

We and others have reported that the serum procalcitonin (PCT) level has a demonstrative role in predicting the long-term mortality after acute ischemic stroke (AIS) in Chinese population. Nevertheless, the underlying mechanisms remain ill-defined. In the current study, we further detected a close association of stool microRNA-637 (miR-637) levels with the long-term mortality after AIS in Chinese population. Moreover, the serum PCT and stool miR-637 levels appeared to be inversely correlated. AIS patients with lower levels of stool miR-637 appeared to predict more severe mortality in the long-term. Since PCT has been shown to be mainly produced by the neuroendocrine cells in the intestine, we used an intestine neuroendocrine cell line to study the relationship between miR-637 and PCT. Bioinformatics analyses showed that miR-637 targeted the 3'-UTR of PCT mRNA to inhibit its translation, and thus the levels of PCT protein production and secretion, which was proved by luciferase reporter assay. Together, our data reveal that the molecular mechanisms underlying application of serum PCT and stool miR-637 in prognosis of AIS, in which miR-637 in intestine neuroendocrine cells may be reduced during AIS to allow more PCT to be released into serum to be detected.

The Role of Bioactive Dietary Components in Modulating miRNA Expression in Colorectal Cancer

Colorectal cancer is the third most common cancer in the world and considered to be one of the most diet-related types of cancer. Extensive research has been conducted but still the link between diet and colorectal cancer is complex. Recent studies have highlight microRNAs (miRNAs) as key players in cancer-related pathways in the context of dietary modulation. MicroRNAs are involved in most biological processes related to tumor development and progression; therefore, it is of great interest to understand the underlying mechanisms by which dietary patterns and components influence the expression of these powerful molecules in colorectal cancer. In this review, we discuss relevant dietary patterns in terms of miRNAs modulation in colorectal cancer, as well as bioactive dietary components able to modify gene expression through changes in miRNA expression. Furthermore, we emphasize on protective components such as resveratrol, curcumin, quercetin, α-mangostin, omega-3 fatty acids, vitamin D and dietary fiber, with a focus on the molecular mechanisms in the context of prevention and even treatment. In addition, several bioactive dietary components that have the ability to re-sensitize treatment resistant cells are described.

Induction of the mesenchymal to epithelial transition by demethylation-activated microRNA-125b is involved in the anti-migration/invasion effects of arsenic trioxide on human chondrosarcoma

Background

In addition to treating acute promyelocytic leukemia, arsenic trioxide (ATO) suppresses other solid tumors, including chondrosarcoma. However, the effects of ATO on metastasis in chondrosarcoma cells, and the underlying molecular mechanisms remain unclear.

Methods

The effects of ATO on the migratory and invasive capacities of chondrosarcoma cells were investigated by Wound healing, Transwell and EMT assays. The expression of miR-125b in human chondrosarcoma tissues and cell lines was detected by real-time PCR analysis. Bisulfite sequencing analysis (BSP) was used to detect the effects of ATO on the expression of miR-125b. The gain-of-function and loss-of-function experiments were performed on chondrosarcoma cell lines to investigate the effects of miR-125b on chondrosarcoma invasion, and to determine whether signal transducer and activator of transcription 3(Stat3) mediates these effects. Dual-luciferase reporter assay was used to identify whether Stat3 is a direct target of miR-125b.

Results

MiR-125b was significantly downregulated in human metastatic chondrosarcoma tissues and cell lines but not in non-metastatic chondrosarcoma tissues. ATO up-regulates the expression of miR-125b by the demethylation of DNA. ATO induces MET and attenuates the invasive capacities of chondrosarcoma cells through miR-125b. Stat3 was verified as a direct target of miR-125b, which is involved in ATO regulating EMT-associated traits.

Conclusions

These findings, for the first time, provides evidence that the miR-125b-mediated inhibition of Stat3 is involved in the ATO-induced attenuation of metastasis in chondrosarcoma cells.

Investigating intra-tumor heterogeneity and expression gradients of miR-21, miR-92a and miR-200c and their potential of predicting lymph node metastases in early colorectal cancer

INTRODUCTION

miR-21, miR-92a and miR-200c are regulators of pathways involved in migration, intravasation and metastasis, and their tumor expression levels have been proposed as potential prognostic markers in colorectal cancer (CRC). In two parallel cohorts we examine intra-tumor expression levels in early stage CRC tissue in order to determine intra-tumor heterogeneity, potential systematic intra-tumor expression gradients of the miRNAs and to investigate the association to metastatic disease in early stage CRC.

MATERIAL AND METHODS

Two parallel studies on archived formalin-fixed paraffin-embedded (FFPE) CRC tissue. Intra-tumor and inter-patient variances were analyzed in 9 early metastatic CRCs by measuring expression levels by qRT-PCR on isolated tissue samples from luminal, central and invasive border zones. Associations between miRNA expression levels and early metastasizing tumors was investigated in FFPE tissue from invasive border and central tumor zones from 47 early metastatic CRCs matched with 47 non-metastatic CRCs. Intra-tumor expression gradients were analyzed on both cohorts.

RESULTS

Mean intra-tumor coefficient of variation in the heterogeneity cohort was 38.5% (range: 33.1-49.0%) only slightly less than variation between patients (45.1%, range 37.0-49.5%). We demonstrated systematic expression gradients between tumor zones equal to a 3.23 (p=0.003) and 1.36 (p=0.014) fold lower expression in invasive areas for miR-200c, 1.52 (p<0.001) and 1.27 (p=0.021) fold lower expression in invasive areas for miR-92a. For miR-21 we found a 1.75 (p<0.001) and 1.21 (p=0.064) fold higher expression in invasive areas compared to luminal and central zones, respectively. No significant difference in expression levels between metastatic and non-metastatic tumors was demonstrated, nor a difference in intra-tumor gradients between metastatic and non-metastatic tumors.

CONCLUSION

This study provides evidence for moderate intra-tumor and inter-patient heterogeneities of three well-described potential prognostic markers in CRC. We demonstrate intra-tumor expression gradients indicating a differentiated expression of the target miRNAs between functional tumor zones, but the potential role as markers of early metastatic disease is still not fully clarified.

Androgen receptor (AR) suppresses miRNA-145 to promote renal cell carcinoma (RCC) progression independent of VHL status

Mutational inactivation of the VHL tumor suppressor plays key roles in the development of renal cell carcinoma (RCC), and mutated VHL-mediated VEGF induction has become the main target for the current RCC therapy. Here we identified a signal pathway of VEGF induction by androgen receptor (AR)/miRNA-145 as a new target to suppress RCC progression. Mechanism dissection revealed that AR might function through binding to the androgen receptor element (ARE) located on the promoter region of miRNA-145 to suppress p53's ability to induce expression of miRNA-145 that normally suppresses expression of HIF2α/VEGF/MMP9/CCND1. Suppressing AR with AR-shRNA or introducing exogenous miRNA-145 mimic can attenuate RCC progression independent of VHL status. MiR-145 mimic in preclinical RCC orthotopic xenograft mouse model revealed its efficacy in suppression of RCC progression. These results together identified signals by AR-suppressed miRNA-145 as a key player in the RCC progression via regulating HIF2α/VEGF/MMP9/CCND1 expression levels. Blockade of the newly identified signal by AR inhibition or miRNA-145 mimics has promising therapeutic benefit to suppress RCC progression.

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.

Intratumoral Heterogeneity of MicroRNA Expression in Rectal Cancer

INTRODUCTION

An increasing number of studies have investigated microRNAs (miRNAs) as potential markers of diagnosis, treatment and prognosis. So far, agreement between studies has been minimal, which may in part be explained by intratumoral heterogeneity of miRNA expression. The aim of the present study was to assess the heterogeneity of a panel of selected miRNAs in rectal cancer, using two different technical approaches.

MATERIALS AND METHODS

The expression of the investigated miRNAs was analysed by real-time quantitative polymerase chain reaction (RT-qPCR) and in situ hybridization (ISH) in tumour specimens from 27 patients with T3-4 rectal cancer. From each tumour, tissue from three different luminal localisations was examined. Inter- and intra-patient variability was assessed by calculating intraclass correlation coefficients (ICCs). Correlations between RT-qPCR and ISH were evaluated using Spearman's correlation.

RESULTS

ICCsingle (one sample from each patient) was higher than 50% for miRNA-21 and miRNA-31. For miRNA-125b, miRNA-145, and miRNA-630, ICCsingle was lower than 50%. The ICCmean (mean of three samples from each patient) was higher than 50% for miRNA-21(RT-qPCR and ISH), miRNA-125b (RT-qPCR and ISH), miRNA-145 (ISH), miRNA-630 (RT-qPCR), and miRNA-31 (RT-qPCR). For miRNA-145 (RT-qPCR) and miRNA-630 (ISH), ICCmean was lower than 50%. Spearman correlation coefficients, comparing results obtained by RT-qPCR and ISH, respectively, ranged from 0.084 to 0.325 for the mean value from each patient, and from -0.085 to 0.515 in the section including the deepest part of the tumour.

CONCLUSION

Intratumoral heterogeneity may influence the measurement of miRNA expression and consequently the number of samples needed for representative estimates. Our findings with two different methods suggest that one sample is sufficient for adequate assessment of miRNA-21 and miRNA-31, whereas more samples would improve the assessment of miRNA-125b, miRNA-145, and miRNA-630. Interestingly, we found a poor correlation between the expression estimates obtained by RT-qPCR and ISH, respectively.

The clinical and biological significance of MIR-224 expression in colorectal cancer metastasis

OBJECTIVE

MicroRNA (miRNA) expression profile can be used as prognostic marker for human cancers. We aim to explore the significance of miRNAs in colorectal cancer (CRC) metastasis.

DESIGN

We performed miRNA microarrays using primary CRC tissues from patients with and without metastasis, and validated selected candidates in 85 CRC samples by quantitative real-time PCR (qRT-PCR). We tested metastatic activity of selected miRNAs and identified miRNA targets by prediction algorithms, qRT-PCR, western blot and luciferase assays. Clinical outcomes were analysed in six sets of CRC cases (n=449), including The Cancer Genome Atlas (TCGA) consortium and correlated with miR-224 status. We used the Kaplan-Meier method and log-rank test to assess the difference in survival between patients with low or high levels of miR-224 expression.

RESULTS

MiR-224 expression increases consistently with tumour burden and microsatellite stable status, and miR-224 enhances CRC metastasis in vitro and in vivo. We identified SMAD4 as a miR-224 target and observed negative correlation (Spearman Rs=-0.44, p<0.0001) between SMAD4 and miR-224 expression in clinical samples. Patients with high miR-224 levels display shorter overall survival in multiple CRC cohorts (p=0.0259, 0.0137, 0.0207, 0.0181, 0.0331 and 0.0037, respectively), and shorter metastasis-free survival (HR 6.51, 95% CI 1.97 to 21.51, p=0.0008). In the TCGA set, combined analysis of miR-224 with SMAD4 expression enhanced correlation with survival (HR 4.12, 95% CI 1.1 to 15.41, p=0.0175).

CONCLUSIONS

MiR-224 promotes CRC metastasis, at least in part, through the regulation of SMAD4. MiR-224 expression in primary CRC, alone or combined with its targets, may have prognostic value for survival of patients with CRC.

MicroRNA-1301-Mediated RanGAP1 Downregulation Induces BCR-ABL Nuclear Entrapment to Enhance Imatinib Efficacy in Chronic Myeloid Leukemia Cells

Chronic myeloid leukemia (CML) is a myeloproliferative disease. Imatinib (IM), the first line treatment for CML, is excessively expensive and induces various side effects in CML patients. Therefore, it is essential to investigate a new strategy for improving CML therapy. Our immunoblot data revealed that RanGTPase activating protein 1 (RanGAP1) protein levels increased by approximately 30-fold in K562 cells compared with those in normal cells. RanGAP1 is one of the important components of RanGTPase system, which regulates the export of nuclear protein. However, whether RanGAP1 level variation influences BCR-ABL nuclear export is still unknown. In this report, using shRNA to downregulate RanGAP1 expression level augmented K562 cell apoptosis by approximately 40% after treatment with 250 nM IM. Immunofluorescence assay also indicated that three-fold of nuclear BCR-ABL was detected. These data suggest that BCR-ABL nuclear entrapment induced by RanGAP1 downregulation can be used to improve IM efficacy. Moreover, our qRT-PCR data indicated a trend of inverse correlation between the RanGAP1 and microRNA (miR)-1301 levels in CML patients. MiR-1301, targeting the RanGAP1 3' untranslated region, decreased by approximately 100-fold in K562 cells compared with that in normal cells. RanGAP1 downregulation by miR-1301 transfection impairs BCR-ABL nuclear export to increase approximately 60% of cell death after treatment of 250 nM IM. This result was almost the same as treatment with 1000 nM IM alone. Furthermore, immunofluorescence assay demonstrated that Tyr-99 of nuclear P73 was phosphorylated accompanied with nuclear entrapment of BCR-ABL after transfection with RanGAP1 shRNA or miR-1301 in IM-treated K562 cells. Altogether, we demonstrated that RanGAP1 downregulation can mediate BCR-ABL nuclear entrapment to activate P73-dependent apoptosis pathway which is a novel strategy for improving current IM treatment for CML.

Development of a deregulating microRNA panel for the detection of early relapse in postoperative colorectal cancer patients

BACKGROUND

Colorectal cancer (CRC) is the third leading cause of cancer mortality worldwide and is associated with high recurrence and mortality, despite recent advancements in therapeutic strategies. MicroRNA (miR) deregulation is associated with CRC development and recurrence; therefore, miRs may be reliable biomarkers for detecting early relapse postoperatively.

METHODS

In this study ten candidates were identified using miR arrays: miR-7, miR-31, miR-93, miR-141, miR-195, miR-375, miR-429, miR-494, miR-650, and let-7b. Substantial differences were observed in their expression levels between early relapsed (recurrences within 12 months after surgery) and non-early relapsed CRC patients. The validation study, including 50 early relapsed and 54 non-early relapsed patients, confirmed miR expression alterations in cancer tissue samples.

RESULTS

Using a miR real-time quantitative polymerase chain reaction (RT-qPCR), we observed that expression levels of miR-93, miR-195, and let-7b were significantly decreased, whereas those of miR-7, miR-141 and miR-494 showed increases that were more significant in the CRC tissue samples from the early relapsed patients than in those from the non-early relapsed patients. Disease-free survival and overall survival were significantly worse in the high miR-7, miR-141, and miR-494 expression subgroups and the low miR-93 and miR-195 expression subgroups (all P < 0.05). A panel of 6 miRs (miR-7, miR-93, miR-195, miR-141, miR-494, and let-7b), at a cut-off value of 2 deregulated miRs, distinguished early relapsed CRC from non-early relapsed CRC, with a sensitivity of 76.6 % and a specificity of 71.4 %. By combining this 6-miRs panel with 6 clinicopathologic factors, at a cut-off value of 4, distinguished early relapsed CRC from non-early relapsed CRC, with a sensitivity of 89.4 % and a specificity of 88.9 %.

CONCLUSIONS

This study showed that the developed miR panel has the potential to improve predicting early relapse in CRC patients.

microRNA and Bone Cancer

MicroRNA molecules have a variety of roles in cellular development and proliferation processes, including normal osteogenesis. These effects are exerted through post-translational inhibition of target genes. Altered miRNA expression has been demonstrated in several cancers, both in the tumor tissue and in the peripheral circulation. This may influence carcinogenesis if the specific miRNA targets are encoded by tumor suppressor genes or oncogenes. To date, most research investigating the role of microRNAs and primary bone tumors has focused on osteosarcoma and Ewing sarcoma. Several microRNAs including the miR-34 family have been implicated in osteosarcoma tumorigenesis via effects on the Notch signaling pathway. Progression, invasion, and metastasis of osteosarcoma tumor cells is also influenced by microRNA expression. In addition, microRNA expression may affect the response to chemotherapy in osteosarcoma and thus hold potential for future use as either a prognostic indicator or a therapeutic target. The EWS-FLI1 fusion protein produced in Ewing sarcoma has been shown to induce changes in miRNA expression. MicroRNA expression profiling may have some potential for prediction of disease progression and survival in Ewing sarcoma. There is limited evidence to support a role for microRNAs in other primary bone tumors, either malignant or benign; however, early work is suggestive of involvement in chondrosarcoma, multiple osteochondromatosis, and giant cell tumors of bone.

Bioinformatic analysis of microRNA networks following the activation of the constitutive androstane receptor (CAR) in mouse liver

The constitutive androstane receptor (CAR; NR1I3) is a member of the nuclear receptor superfamily that functions as a xenosensor, serving to regulate xenobiotic detoxification, lipid homeostasis and energy metabolism. CAR activation is also a key contributor to the development of chemical hepatocarcinogenesis in mice. The underlying pathways affected by CAR in these processes are complex and not fully elucidated. MicroRNAs (miRNAs) have emerged as critical modulators of gene expression and appear to impact many cellular pathways, including those involved in chemical detoxification and liver tumor development. In this study, we used deep sequencing approaches with an Illumina HiSeq platform to differentially profile microRNA expression patterns in livers from wild type C57BL/6J mice following CAR activation with the mouse CAR-specific ligand activator, 1,4-bis-[2-(3,5,-dichloropyridyloxy)] benzene (TCPOBOP). Bioinformatic analyses and pathway evaluations were performed leading to the identification of 51 miRNAs whose expression levels were significantly altered by TCPOBOP treatment, including mmu-miR-802-5p and miR-485-3p. Ingenuity Pathway Analysis of the differentially expressed microRNAs revealed altered effector pathways, including those involved in liver cell growth and proliferation. A functional network among CAR targeted genes and the affected microRNAs was constructed to illustrate how CAR modulation of microRNA expression may potentially mediate its biological role in mouse hepatocyte proliferation. This article is part of a Special Issue entitled: Xenobiotic nuclear receptors: New Tricks for An Old Dog, edited by Dr. Wen Xie.

High blood sugar levels significantly impact the prognosis of colorectal cancer patients through down-regulation of microRNA-16 by targeting Myb and VEGFR2

The high prevalence of type 2 diabetes mellitus in colorectal cancer patients is a crucial public health issue worldwide. The deregulation of microRNAs has been shown to be associated with the progression of CRC; however, the effects of high blood sugar levels on miR deregulation and, in turn, CRC remain unexplored. In this study, 520 CRC patients were classified into two groups according to their blood sugar levels (≧110 or <110 mg/dL). Clinicopathologic features, clinical outcomes, and serum miR-16 levels of the two groups were then analyzed, while cell cycles, cell proliferation, migration, and cellular miR-16 expression were investigated via D-(+)-glucose administration. Additionally, the target genes of miR-16 were identified. Through multivariate analysis, both the disease-free survival and overall survival of the CRC patients were found to be associated with the UICC stage, perineural invasion, and blood glucose levels (P < 0.05). Serum miR-16 levels were significantly lower in the high blood glucose patients than in the normal blood glucose patients (P = 0.0329). With D-(+)-glucose administration, the proliferation and migration of CRC cells in vitro increased remarkably (P < 0.05), while their accumulation in the G1 phase decreased significantly. Cellular miR-16 expression was suppressed by D-(+)-glucose administration. The expression levels of two target genes, Myb and VEGFR2, were affected significantly by miR-16, while glucose administration inhibited miR-16 expression and enhanced tumor cell proliferation and migration. Hyperglycemia can impact the clinical outcomes of CRC patients, likely by inhibiting miR-16 expression and the expression of its downstream genes Myb and VEGFR2.

MicroRNAs: exploring new horizons in osteoarthritis

INTRODUCTION

Osteoarthritis (OA) is a common disease worldwide leading to significant morbidity. The underlying disease process is multifactorial however there is increasing focus on molecular mechanisms. MicroRNAs are small non-coding segments of RNA that have important regulatory functions at a cellular level. These molecules are readily detectable in human tissues and circulation. They are increasingly recognised as having a major role in many disease processes - including malignancy and inflammatory processes.

OBJECTIVE

This review paper aims to provide a comprehensive update on the evidence for miRNA roles in OA.

DESIGN

A comprehensive literature search was performed using key medical subject headings (MeSH) terms 'microRNA' and 'osteoarthritis'.

RESULTS

Several miRNAs have been identified as having aberrant expression levels in OA. Some of these include miR-9, miR-27, miR-34a, miR-140, miR-146a, miR-558 and miR-602. Many of the dysregulated miRNAs have been shown to regulate expression of inflammatory pathways such as interleukin-mediated or matrix metalloproteinase-13 (MMP-13)-mediated degradation of the articular cartilage extracellular matrix (ECM). MiRNAs may also play a role in pain pathways and hence expression of clinical symptoms.

CONCLUSIONS

Recent evidence has shown that miRNAs in the circulation may reflect underlying disease states and hence serve as potential markers for disease activity. These findings may represent possible future therapeutic applications in the management of OA.

Screening miRNAs for early diagnosis of colorectal cancer by small RNA deep sequencing and evaluation in a Chinese patient population

PURPOSE

This study aims to screen microRNAs (miRNAs), for an early diagnosis of colorectal cancer, by deep sequencing and evaluation of total miRNAs using clinical samples from a Chinese patient population.

METHODS

Total small RNAs from normal colonic mucosa, colonic adenomas, and colorectal cancer tissues were prepared for miRNA analysis by deep sequencing. The sequencing data were then analyzed by bioinformatics for candidate diagnostic miRNAs, which were further validated for their up- or downregulation status.

RESULTS

Comparison of cancer tissues with normal mucosa identified 99 upregulated and 90 downregulated miRNAs. Comparison of adenomas and normal mucosa found 114 upregulated and 107 downregulated miRNAs. Comparison of cancer and adenoma tissues found 70 upregulated and 27 downregulated miRNAs. Selected up- and downregulated miRNAs were validated for their expressions in 12 cases of patients with cancer and polyps. Specifically, for the upregulated miRNAs, miR-18a-5p and miR-21-3p were significantly upregulated in adenomas and cancer tissues, compared with the normal mucosa; miR-135b-5p, miR-17-5p, miR-182-5p, miR-200a-5p, and miR-200c-3p were significantly upregulated in cancer tissues compared to the normal mucosa, but their differential expression was not significant in adenoma tissues when compared with the normal mucosa. miR-183-5p and miR-96-5p were significantly upregulated in adenoma tissues when compared with normal mucosa, but these differences were not significant in cancer tissues when compared to normal mucosa. For the downregulated miRNAs, miR-133a-3p was significantly downregulated in both adenoma and cancer tissues when compared to normal mucosa; miR-204-5p, miR-125b-5p, miR-139-5p, miR-100-5p, and miR-30a-5p were significantly downregulated in cancer tissues compared to the normal mucosa, but their differential expression was not significant in adenoma tissue compared to normal mucosa.

CONCLUSION

The findings of this study show that a number of miRNAs might be important in the diagnosis and prognosis of colorectal cancer in Chinese patients using the method of small RNA deep sequencing. Upregulation of miR-18a-5p and miR-21-3p or downregulation of miR-133a-3p in adenoma and cancer tissues may serve as an index for early screening of colorectal cancer. Other miRNAs, such as miR-135b-5p, miR-17-5p, miR-182-5p, miR-200a-5p, miR-200c-3p, miR-183-5p, and miR-96-5p, which were either up- or downregulated, in cancer tissues, but not in adenoma tissues, have limited significance in early diagnosis. Further study is needed to determine a screening index with diagnostic value.

MicroRNA Expression Profiling to Identify and Validate Reference Genes for the Relative Quantification of microRNA in Rectal Cancer

Introduction

MicroRNAs (miRNAs) play important roles in regulating biological processes at the post-transcriptional level. Deregulation of miRNAs has been observed in cancer, and miRNAs are being investigated as potential biomarkers regarding diagnosis, prognosis and prediction in cancer management. Real-time quantitative polymerase chain reaction (RT-qPCR) is commonly used, when measuring miRNA expression. Appropriate normalisation of RT-qPCR data is important to ensure reliable results. The aim of the present study was to identify stably expressed miRNAs applicable as normaliser candidates in future studies of miRNA expression in rectal cancer.

Materials and Methods

We performed high-throughput miRNA profiling (OpenArray®) on ten pairs of laser micro-dissected rectal cancer tissue and adjacent stroma. A global mean expression normalisation strategy was applied to identify the most stably expressed miRNAs for subsequent validation. In the first validation experiment, a panel of miRNAs were analysed on 25 pairs of micro dissected rectal cancer tissue and adjacent stroma. Subsequently, the same miRNAs were analysed in 28 pairs of rectal cancer tissue and normal rectal mucosa.

Results

From the miRNA profiling experiment, miR-645, miR-193a-5p, miR-27a and let-7g were identified as stably expressed, both in malignant and stromal tissue. In addition, NormFinder confirmed high expression stability for the four miRNAs. In the RT-qPCR based validation experiments, no significant difference between tumour and stroma/normal rectal mucosa was detected for the mean of the normaliser candidates miR-27a, miR-193a-5p and let-7g (first validation P = 0.801, second validation P = 0.321). MiR-645 was excluded from the data analysis, because it was undetected in 35 of 50 samples (first validation) and in 24 of 56 samples (second validation), respectively. Significant difference in expression level of RNU6B was observed between tumour and adjacent stromal (first validation), and between tumour and normal rectal mucosa (second validation).

Conclusion

We recommend the mean expression of miR-27a, miR-193a-5p and let-7g as normalisation factor, when performing miRNA expression analyses by RT-qPCR on rectal cancer tissue.

Epigenetic regulation of gene expression and M2 macrophage polarization as new potential omega-3 polyunsaturated fatty acid targets in colon inflammation and cancer

INTRODUCTION

It has become increasingly clear that dietary habits may affect the risk/progression of chronic diseases with a pathogenic inflammatory component, such as colorectal cancer. Considerable attention has been directed toward the ability of nutritional agents to target key molecular pathways involved in these inflammatory-related diseases.

AREAS COVERED

ω-3 Polyunsaturated fatty acids (PUFA) and their oxidative metabolites have attracted considerable interest as possible anti-inflammatory and anti-cancer agents, especially in areas such as the large bowel, where the influence of orally introduced substances is high and tumors show deranged PUFA patterns. On this basis, we have analyzed pre-clinical findings that have recently revealed new insight into the molecular pathways targeted by ω-3 PUFA.

EXPERT OPINION

The findings analyzed herein demonstrate that ω-3 PUFA may exert beneficial effects by targeting the epigenetic regulation of gene expression and altering M2 macrophage polarization during the inflammatory response. These mechanisms need to be better explored in the large bowel, and further studies could better clarify their role and the potential of dietary interventions with ω-3 PUFA in the large bowel. The epigenomic mechanism is discussed in view of the potential of ω-3 PUFA to enhance the efficacy of other agents used in the therapy of colorectal cancer.

Contribution of in vitro comparison of colorectal carcinoma cells from primary and metastatic lesions to elucidation of mechanisms of tumor progression and response to anticancer therapy

Colorectal cancer has been a leading cause of cancer-related morbidity and mortality. For the research and individualization of therapy, primary cell lines of the colorectal cancer appear to be still an invaluable tool. We evaluated the differences in metastatic potential between four isolated primary colon cancer cells and cells derived from their lymph node metastasis. These results were compared with correspond immortalized cells-SW480 and SW620, respectively. The ability to migrate was tested using real-time measurement in xCELLigence system. Expressions of molecules involved in adhesion and invasion processes were examined using RT-PCR and western blot analysis. Furthermore, impact of cytotoxic effect of selected chemotherapeutics (irinotecan, oxaliplatin) and biological therapy (bevacizumab, cetuximab, panitumumab) was assessed by the WST assay. As expected, cell lines derived from lymph node migrated more aggressively and higher expression of adhesion molecules ICAM-1, EpCAM, and N-cadherin was detected. The expression of MMP-2 and -9 was elevated, on the other hand, in cell lines derived from primary tumor cancer cells as well as the expression of miR-21, miR-29a, and miR-200a. The most pronounced cytotoxic effect has been recorded with oxaliplatin and irinotecan (IC50 = 48.23 resp. 0.11 μg/ml), especially in cells originating from lymph node metastases. In total, comparison of isolated cell lines and immortalized cell lines has shown many similarities, as well as several differences. Adhesion/invasion molecules and several miRNAs, which play an important role in tumor development and the invasive and migratory behavior, could be a useful therapeutic target in malignant colorectal cancer.

Stratifying risk of recurrence in stage II colorectal cancer using deregulated stromal and epithelial microRNAs

MicroRNAs (miRNAs) enable colonic epithelial cells to acquire malignant characteristics and metastatic capabilities. Recently, cancer relevant miRNAs deregulated during disease progression have also been identified in tumor-associated stroma.By combining laser-microdissection (LMD) with high-throughput screening and high-sensitivity quantitation techniques, miRNA expression in colorectal cancer (CRC) specimens and paired normal colonic tissue was independently characterized in stromal and epithelial tissue compartments. Notably, deregulation of the key oncogene miR-21 was identified exclusively as a stromal phenomenon and miR-106a, an epithelial phenomenon in the malignant state.MiRNAs identified in this study successfully distinguished CRC from normal tissue and metastatic from non-metastatic tumor specimens. Furthermore, in a separate cohort of 50 consecutive patients with CRC, stromal miR-21 and miR-556 and epithelial miR-106a expression predicted short disease free survival (DFS) and overall survival (OS) in stage II disease: miR-21 (DFS: HR = 2.68, p = 0.015; OS: HR = 2.47, p = 0.029); miR-556 (DFS: HR = 2.60, p = 0.018); miR-106a (DFS: HR = 2.91, p = 0.008; OS: HR = 2.25, p = 0.049); combined (All High vs. All Low. DFS: HR = 5.83, p = 0.002; OS: HR = 4.13, p = 0.007).These data support the notion that stromal as well as epithelial miRNAs play important roles during disease progression, and that mapping patterns of deregulated gene expression to the appropriate tumor strata may be a valuable aid to therapeutic decision making in CRC.

Circulating cell-free microRNAs as biomarkers for colorectal cancer

MicroRNAs (miRNAs) are a class of small, endogenous, non-coding, single-stranded RNAs that act as post-transcriptional regulators. Their discovery has provided new avenues for the diagnosis and treatment of cancer. The expression of both oncogenic and tumor suppressor miRNAs can be aberrantly either up- or down-regulated in cancer cells. These miRNAs target mRNAs of genes that either promote or inhibit tumor growth, and are one of several epigenetic factors that control the initiation and progression of colorectal cancer (CRC) and other cancers. Investigations of miRNAs as CRC biomarkers have employed the expression profiling of traditional tissue samples and, more recently, non-invasive samples, such as feces and body fluids, have been analyzed. MiRNAs may also be able to predict responses to chemo- and radiotherapy, and may be manipulated to modify CRC characteristics. We herein discuss the use of circulating miRNAs as possible non-invasive biomarkers of early CRC onset, relapse, or response to treatment. We also discuss the obstacles that currently limit the routine use of epigenetic biomarkers in clinical settings.

Rotavirus-induced miR-142-5p elicits proviral milieu by targeting non-canonical transforming growth factor beta signalling and apoptosis in cells

MicroRNA (miRNA) expression is significantly influenced by viral infection, because of either host antiviral defences or proviral factors resulting in the modulation of viral propagation. This study was undertaken to identify and analyse the significance of cellular miRNAs during rotavirus (SA11 or KU) infection. Sixteen differentially regulated miRNAs were identified during rotavirus infection of which hsa-miR-142-5p was up-regulated and validated by quantitative polymerase chain reaction. Exogenous expression of miR-142-5p inhibitor resulted in a significant reduction of viral titer indicating proviral role of miR-142-5p. Functional studies of hsa-miR-142-5p identified its role in transforming growth factor beta (TGFβ) signalling as TGFβ receptor 2 and SMAD3 were degraded during both hsa-miR-142-5p overexpression and rotavirus infection. TGFβ is induced during rotavirus infection, which may promote apoptosis by activation of non-canonical pathways in HT29 cells. However, up-regulated miR-142-5p resulted in the inhibition of TGFβ-induced apoptosis suggesting its anti-apoptotic function. Rotavirus NSP5 was identified as a regulator of miR-142-5p expression. Concurrently, NSP5-HT29 cells showed inhibition of TGFβ-induced apoptosis and epithelial to mesenchymal transition by blocking non-canonical pathways. Overall, the study identified proviral function of hsa-miR-142-5p during rotavirus infection. In addition, modulation of TGFβ-induced non-canonical signalling in microsatellite stable colon cancer cells can be exploited for cancer therapeutics.

Microbial Disruption of Autophagy Alters Expression of the RISC Component AGO2, a Critical Regulator of the miRNA Silencing Pathway

BACKGROUND

Autophagy is implicated in Crohn's disease (CD) pathogenesis. Recent evidence suggests autophagy regulates the microRNA (miRNA)-induced silencing complex (miRISC). Therefore, autophagy may play a novel role in CD by regulating expression of miRISC, thereby altering miRNA silencing. As microbes associated with CD can alter autophagy, we hypothesized that microbial disruption of autophagy affects the critical miRISC component AGO2.

METHODS

AGO2 expression was assessed in epithelial and immune cells, and intestinal organoids with disrupted autophagy. Microarray technology was used to determine the expression of downstream miRNAs in cells with defective autophagy.

RESULTS

Increased AGO2 was detected in autophagy-deficient ATG5-/- and ATG16-/- mouse embryonic fibroblast cells (MEFs) in comparison with wild-type MEFs. Chemical agents and VacA toxin, which disrupt autophagy, increased AGO2 expression in MEFs, epithelial cells lines, and human monocytes, respectively. Increased AGO2 was also detected in ATG7-/- intestinal organoids, in comparison with wild-type organoids. Five miRNAs were differentially expressed in autophagy-deficient MEFs. Pathway enrichment analysis of the differentially expressed miRNAs implicated signaling pathways previously associated with CD.

CONCLUSIONS

Taken together, our results suggest that autophagy is involved in the regulation of the critical miRISC component AGO2 in epithelial and immune cells and primary intestinal epithelial cells. We propose a mechanism by which autophagy alters miRNA expression, which likely impacts the regulation of CD-associated pathways. Furthermore, as enteric microbial products can manipulate autophagy and AGO2, our findings suggest a novel mechanism by which enteric microbes could influence miRNA to promote disease.

The Effects of miR-20a on p21: Two Mechanisms Blocking Growth Arrest in TGF-β-Responsive Colon Carcinoma

Loss of response to TGF-β is a central event in the genesis of colorectal cancer (CRC), a disease that, in the majority cases, is refractory to growth inhibition induced by this cytokine. However, inactivating mutations at receptors and transducers from the TGF-β cascade occur only in approximately half of CRCs, suggesting the involvement of additional mechanisms altering the response to the cytokine. We have recently described the amplification of the 13q31 locus, where the miR-17-92 cluster maps, associated with overexpression of its members. In this study, we address the potential role of miR-20a, from the miR-17-92 cluster, in the suppression of TGF-β cytostatic response in CRC. Using the poorly tumorigenic and TGF-β-sensitive FET cell line that expresses low miR-20a levels, we first confirmed that miR-20a downmodulated CDKN1A expression, both at mRNA and protein level, through direct binding to its 3'-UTR. We demonstrated that miR-20a significantly diminished cell response to TGF-β by preventing its delay of G1/S transition and promoting progression into cell cycle. Moreover, besides modulating CDKN1A, miR-20a blocked TGF-β-induced transactivation of its promoter without affecting the post-receptor activation of Smad3/4 effectors directly. Finally, miR-20a abrogated the TGF-β-mediated c-Myc repression, a direct inhibitor of the CDKN1A promoter activation, most likely by reducing the expression of specific MYC-regulating genes from the Smad/E2F-based core repressor complex. Our experiments indicate that miR-20a interferes with the colonic epithelium homeostasis by disrupting the regulation of Myc/p21 by TGF-β, which is essential for its malignant transformation.

microRNAs: An Emerging Paradigm in Lung Cancer Chemoresistance

Lung cancer is considered the most deadly of all cancers, with limited therapeutic options. Although advanced drugs have been tried in clinic, the therapeutic success has largely been hampered due to rapid development of drug-resistance mechanisms. Recently, microRNAs (miRNAs), a class of small non-coding RNAs, have occupied center stage in cancer biology. miRNAs negatively regulate gene expression either by promoting degradation or by interfering with translation of messenger RNA targets. Several lines of evidence have confirmed the crucial role of miRNAs in carcinogenesis, and, importantly, in the acquisition of resistance to chemotherapeutics. Modulation of miRNA expression levels has been proven to increase the efficacy of genotoxic drugs in various preclinical cancer studies. Therefore, comprehensive understanding of the role(s) of these key players in drug resistance may provide novel opportunities to design effective combinatorial therapeutic strategies for cancer treatment. In this review, we highlight recent findings on miRNAs acting as oncomiRs and tumor suppressor genes in lung cancer. Moreover, we discuss the involvement of miRNAs in different mechanisms of drug resistance in this deadly disease.

Epigenetic regulation of the intestinal epithelium

The intestinal epithelium is an ideal model system for the study of normal and pathological differentiation processes. The mammalian intestinal epithelium is a single cell layer comprising proliferative crypts and differentiated villi. The crypts contain both proliferating and quiescent stem cell populations that self-renew and produce all the differentiated cell types, which are replaced every 3-5 days. The genetics of intestinal development, homeostasis, and disease are well defined, but less is known about the contribution of epigenetics in modulating these processes. Epigenetics refers to heritable phenotypic traits, including gene expression, which are independent of mutations in the DNA sequence. We have known for several decades that human colorectal cancers contain hypomethylated DNA, but the causes and consequences of this phenomenon are not fully understood. In contrast, tumor suppressor gene promoters are often hypermethylated in colorectal cancer, resulting in decreased expression of the associated gene. In this review, we describe the role that epigenetics plays in intestinal homeostasis and disease, with an emphasis on results from mouse models. We highlight the importance of producing and analyzing next-generation sequencing data detailing the epigenome from intestinal stem cell to differentiated intestinal villus cell.

microRNA-17 Is the Most Up-Regulated Member of the miR-17-92 Cluster during Early Colon Cancer Evolution

Deregulated microRNAs play a role in the development and progression of colon cancer, but little is known about their tissue and cell distribution in the continuum of normal mucosa through the premalignant adenoma to invasive adenocarcinoma. The aim of this study was to examine the expression pattern of the miR-17-92 cluster (miR-17, miR-18, miR-19, miR-20 and miR-92) as well as miR-21, miR-31, miR-135b, and miR-145 in early clinically diagnosed colon cancer. MicroRNAs were analysed by chromogenic in situ hybridisation in the normal-adenoma-adenocarcinoma sequence of nine adenocarcinomas developed in mucosal colon polyps. Subsequently, the expression of selected microRNAs was validated in 24 mucosal colon cancer polyps. Expression of miR-17 was confined to the epithelial cells, and the expression levels increased in the transitional zone from normal to adenomatous tissue. The miR-17-92 cluster members, miR-19b, miR-20a, and miR-92a, followed the same expression pattern, but miR-17 was the most predominant. An increased expression of miR-21 was found in the tumour-associated stroma with the most dramatic increase from adenoma to adenocarcinoma, while the number of positive miR-145 fibroblast-like cells in the normal lamina propria (stroma) decreased in a stepwise manner throughout the normal-adenoma-adenocarcinoma sequence. It is concluded that the expression of miR-17, miR-21, and miR-145 changes at early stages of the normal-adenoma-adenocarcinoma sequence. Thus, these microRNAs may play a role in the development of colon cancer.

Epigenetic Alterations in Colorectal Cancer: Emerging Biomarkers

Colorectal cancer (CRC) is a leading cause of cancer deaths worldwide. One of the fundamental processes driving the initiation and progression of CRC is the accumulation of a variety of genetic and epigenetic changes in colonic epithelial cells. Over the past decade, major advances have been made in our understanding of cancer epigenetics, particularly regarding aberrant DNA methylation, microRNA (miRNA) and noncoding RNA deregulation, and alterations in histone modification states. Assessment of the colon cancer "epigenome" has revealed that virtually all CRCs have aberrantly methylated genes and altered miRNA expression. The average CRC methylome has hundreds to thousands of abnormally methylated genes and dozens of altered miRNAs. As with gene mutations in the cancer genome, a subset of these epigenetic alterations, called driver events, are presumed to have a functional role in CRC. In addition, the advances in our understanding of epigenetic alterations in CRC have led to these alterations being developed as clinical biomarkers for diagnostic, prognostic, and therapeutic applications. Progress in this field suggests that these epigenetic alterations will be commonly used in the near future to direct the prevention and treatment of CRC.

Carcinogenic activity of PbS quantum dots screened using exosomal biomarkers secreted from HEK293 cells

Lead sulfide (PbS) quantum dots (QDs) have been applied in the biomedical area because they offer an excellent platform for theragnostic applications. In order to comprehensively evaluate the biocompatibility of PbS QDs in human cells, we analyzed the exosomes secreted from cells because exosomes are released during cellular stress to convey signals to other cells and serve as a reservoir of enriched biomarkers. PbS QDs were synthesized and coated with 3-mercaptopropionic acid (MPA) to allow the particles to disperse in water. Exosomes were isolated from HEK293 cells treated with PbS-MPA at concentrations of 0 µg/mL, 5 µg/mL, and 50 µg/mL, and the exosomal expression levels of miRNAs and proteins were analyzed. As a result, five miRNAs and two proteins were proposed as specific exosomal biomarkers for the exposure of HEK293 cells to PbS-MPA. Based on the pathway analysis, the molecular signature of the exosomes suggested that PbS-MPA QDs had carcinogenic activity. The comet assay and expression of molecular markers, such as p53, interleukin (IL)-8, and C-X-C motif chemokine 5, indicated that DNA damage occurred in HEK293 cells following PbS-MPA exposure, which supported the carcinogenic activity of the particles. In addition, there was obvious intensification of miRNA expression signals in the exosomes compared with that of the parent cells, which suggested that exosomal biomarkers could be detected more sensitively than those of whole cellular extracts.

Identifying miRNA/mRNA negative regulation pairs in colorectal cancer

Although considerable progress has been made in the molecular biology of Colorectal cancer (CRC), novel approaches are still required to uncover the detailed molecular mechanism of CRC. We aim to explore the potential negatively regulated miRNA-mRNA pairs and investigate their regulatory roles so as to elaborate the potential roles of the critical proteins in the signaling pathways enriched by the differential target genes of negatively regulated miRNA in CRC. Firstly, the differential miRNA-mRNA pairs were selected, followed by pairs of miRNA and their target genes. The obtained relationships were subjected to do functional enrichment analysis and those enriched in CRC pathways were chose to further construct a protein interaction network. Finally, we analyzed the regulatory roles of these relationships and constructed a regulatory network of negatively regulated miRNA and mRNA relationships. A total of 372 pairs of miRNA-mRNA were found and 108 target genes of miRNA were obtained. Three miRNAs including hsa-mir-23b, hsa-mir-365-1 and hsa-mir-365-2 showed significant influence on prognosis of CRC patients. To conclude, the miRNA/mRNA deregulations pairs identified in this study have high potentials to be further applied in diagnosis and treatment of CRC.

Molecular biomarkers in colorectal carcinoma

Colorectal cancer is a tumor with increasing incidence which represents one of the first leading causes of death worldwide. Gene alterations described for colorectal cancer include genome instability (microsatellite and chromosomal instability), CpG islands methylator phenotype, microRNA, histone modification, protein biomarkers, gene mutations (RAS, BRAF, PI3K, TP53, PTEN) and polymorphisms (APC, CTNNB1, DCC). In this article, biomarkers with prognostic value commonly found in colorectal cancer will be reviewed.

An evaluation and replication of miRNAs with disease stage and colorectal cancer-specific mortality

MicroRNAs (miRNAs) have been implicated in colorectal cancer (CRC) development and associated with prognostic indicators such as disease stage and survival. Prognostic associations are often based on few individuals and imprecise. In this study, we utilize population-based data from 1,141 CRC cases to replicate previously reported associations between 121 miRNAs and disease stage and survival. The Agilent Human miRNA Microarray V19.0 was used to generate miRNA data following a stringent quality control protocol. Assessment of survival was done using Cox Proportional Hazard models adjusting for age, disease stage and tumor molecular phenotype. Five miRNAs were associated with more advanced disease stage; hsa-miR-145-5p and hsa-miR-31-5p showed increased expression with more advanced tumor stage, while hsa-miR-200b-3p, hsa-miR-215 and hsa-miR-451a had decreased expression with more advanced tumors. Thirteen miRNAs were associated with CRC mortality among individuals diagnosed with colon cancer while 14 were associated with CRC mortality after a diagnosis with rectal cancer. Strongest associations were observed for those miRNAs that were expressed in a small subset of tumors. Most notable associations were for hsa-miR-145-3p [hazard ratio (HR) 2.94, 95% confidence interval (CI) 1.54, 5.61], and hsa-miR-9-3p (HR 10.28, 95% CI 1.31, 80.84) with colon cancer and hsa-miR-335-5p (HR 0.17, 95% CI 0.05, 0.54) for rectal cancer. hsa-miR-374a-5p, hsa-miR-570-3p and hsa-miR-18a-5p significantly reduced the hazard of dying for all cases, regardless of tumor site. Our findings illustrate the need for a large sample to evaluate the association of miRNAs with survival and disease stage in order to determine associations by tumor site.