MicroRNA-21 is overexpressed in human cholangiocarcinoma and regulates programmed cell death 4 and tissue inhibitor of metalloproteinase 3

Plasma miR-21 is a novel diagnostic biomarker for biliary tract cancer

Biliary tract cancer (BTC) has a generally poor prognosis. Furthermore, it is difficult to distinguish BTC from benign biliary disease (BBD) with commonly used modalities. Therefore, a novel biomarker to facilitate cancer detection is highly desirable. Recent studies have reported the use of circulating microRNAs (miRNAs) as biomarkers for cancers. The purpose of this study was to evaluate whether circulating miRNA-21 (miR-21) could be used as a biomarker for BTC. Plasma samples were obtained from 94 BTC patients, 50 healthy volunteers (HVs), and 23 BBD patients. miR-21 levels in the samples were measured by qRT-PCR. Plasma miR-21 levels in patients with BTC were significantly higher than in HVs or in patients with BBD (P < 0.0001 for both). Receiver-operator curve (ROC) curve analysis in differentiating BTC patients from HVs indicated that area under the curve (AUC), optimal sensitivity and specificity was 0.93, 85.1% and 100%, respectively, and those in differentiating BTC patients from BBD patients was 0.83, 72.3%, 91.3%, respectively. Validation of these results indicated that the negative predictive value, positive predictive value, sensitivity, specificity, and accuracy in differentiating BTC patients from HVs was 76.6%, 98.6%, 84.0%, 98.0%, and 88.9%, respectively, and those in differentiating BTC patients from BBD patients was 42.2%, 93.0%, 71.2%, 82.6%, and 72.6%, respectively. These sets of values were improved by combining miR-21 and CA19-9 measurements. Plasma miR-21 is a novel diagnostic biomarker for BTC, and may be useful in distinguishing between BTC and BBD patients.

Small molecule with big role: MicroRNAs in cancer metastatic microenvironments

Cancer metastasis is closely related to tumor cell microenvironments. Cancer cells and stromal cells interact with one another through extracellular matrix (ECM) and jointly participate in establishing the microenvironments. However, many questions remain to be addressed, in particular, a crucial question is which messengers mediate the mutual interaction and regulation between cancer cells and stromal cells. MicroRNAs (miRNAs), as oncogenic and oncosuppressor genes, regulate the expression and function of their related target genes to affect the biological behaviors of cancer cells and stromal cells, which may play an important role in cancer metastasis. Many miRNAs associated with cancer metastasis have been identified. The molecules of miRNAs are small and relatively easy to be secreted into extracellular microenvironments and devoured by nearby cells. As the regulatory messengers between cells, the secreted miRNAs function to regulate cancer cell proliferation, migration, intercellular communication and stromal modification, thereby helping cancer cells to establish their microenvironments for metastasis. In conclusion, miRNAs are small molecules, but they play a powerful role in regulating cancer metastatic ability by construction and modification of microenvironments.

miR-29b, miR-205 and miR-221 enhance chemosensitivity to gemcitabine in HuH28 human cholangiocarcinoma cells

BACKGROUND AND AIMS

Cholangiocarcinoma (CCA) is highly resistant to chemotherapy, including gemcitabine (Gem) treatment. MicroRNAs (miRNAs) are endogenous, non-coding, short RNAs that can regulate multiple genes expression. Some miRNAs play important roles in the chemosensitivity of tumors. Here, we examined the relationship between miRNA expression and the sensitivity of CCA cells to Gem.

METHODS

Microarray analysis was used to determine the miRNA expression profiles of two CCA cell lines, HuH28 and HuCCT1. To determine the effect of candidate miRNAs on Gem sensitivity, expression of each candidate miRNA was modified via either transfection of a miRNA mimic or transfection of an anti-oligonucleotide. Ontology-based programs were used to identify potential target genes of candidate miRNAs that were confirmed to affect the Gem sensitivity of CCA cells.

RESULTS

HuCCT1 cells were more sensitive to Gem than were HuH28 cells, and 18 miRNAs were differentially expressed whose ratios over ± 2log2 between HuH28 and HuCCT1. Among these 18 miRNAs, ectopic overexpression of each of three downregulated miRNAs in HuH28 (miR-29b, miR-205, miR-221) restored Gem sensitivity to HuH28. Suppression of one upregulated miRNA in HuH28, miR-125a-5p, inhibited HuH28 cell proliferation independently to Gem treatment. Selective siRNA-mediated downregulation of either of two software-predicted targets, PIK3R1 (target of miR-29b and miR-221) or MMP-2 (target of miR-29b), also conferred Gem sensitivity to HuH28.

CONCLUSIONS

miRNA expression profiling was used to identify key miRNAs that regulate Gem sensitivity in CCA cells, and software that predicts miRNA targets was used to identify promising target genes for anti-tumor therapies.

Intrahepatic cholangiocarcinoma: pathogenesis and rationale for molecular therapies

Intrahepatic cholangiocarcinoma (ICC) is an aggressive malignancy with very poor prognosis. Genome-wide, high-throughput technologies have made major advances in understanding the molecular basis of this disease, although important mechanisms are still unclear. Recent data have revealed specific genetic mutations (for example, KRAS, IDH1 and IDH2), epigenetic silencing, aberrant signaling pathway activation (for example, interleukin (IL)-6/signal transducer and activator of transcription 3 (STAT3), tyrosine kinase receptor-related pathways) and molecular subclasses with unique alterations (for example, proliferation and inflammation subclasses). In addition, some ICCs share common genomic traits with hepatocellular carcinoma. All this information provides the basis to explore novel targeted therapies. Currently, surgery at early stage is the only effective therapy. At more advanced stages, chemotherapy regimens are emerging (that is, cisplatin plus gemcitabine), along with molecular targeted agents tested in several ongoing clinical trials. Nonetheless, a first-line conclusive treatment remains an unmet need. Similarly, there are no studies assessing tumor response related with genetic alterations. This review explores the recent advancements in the knowledge of the molecular alterations underlying ICC and the future prospects in terms of therapeutic strategies leading towards a more personalized treatment of this neoplasm.

Expression, tissue distribution and function of miR-21 in esophageal squamous cell carcinoma

Objective

MiR-21 is an oncomir expressed by malignant cells and/or tumor microenvironment components. In this study we focused on understanding the effects of stromal miR-21 on esophageal malignant cells.

Design

MiR-21 expression was evaluated in formalin-fixed paraffin-embedded samples from patients with esophageal squamous-cell carcinoma (SCC) by quantitative RT-PCR. MiR-21 tissue distribution was visualized with in situ hybridization. A co-culture system of normal fibroblasts and esophageal cancer cells was used to determine the effects of fibroblasts on miR-21 expression levels, and on SCC cell migration and invasion.

Results

MiR-21 was overexpressed in SCCs, when compared to the adjacent non-tumor tissues (P = 0.0007), and was mainly localized in the cytoplasm of stromal cells adjacent to malignant cells. Accordingly, miR-21 expression was increased in tumors with high versus low stromal content (P = 0.04). When co-cultured with normal fibroblasts, miR-21 expression was elevated in SCC cells (KYSE-30), while its expression was restricted to fibroblasts when co-cultured with adenocarcinoma cells (OE-33 and FLO-1). MiR-21 was detected in conditioned media of cancer cell lines, illustrating the release of this miRNA into the environment. Co-culturing with normal fibroblasts or addition of fibroblast conditioned media caused a significant increase in cell migration and invasion potency of KYSE-30 cells (P<0.0001). In addition, co-culturing cancer cells with fibroblasts and expression of miR-21 induced the expression of the cancer associated fibroblast (CAF) marker S100A4.

Conclusions

MiR-21 expression is mostly confined to the SCC stroma and its release from fibroblasts influences the migration and invasion capacity of SCC cells. Moreover, miR-21 may be an important factor in “activating” fibroblasts to CAFs. These findings provide new insights into the role of CAFs and the extracellular matrix in tumor microenvironment formation and in tumor cell maintenance, and suggest miR-21 may contribute to cellular crosstalk in the tumor microenvironment.

Negative regulation of lncRNA GAS5 by miR-21

In addition to protein-coding genes, the human genome makes a large amount of noncoding RNAs, including microRNAs and long noncoding RNAs (lncRNAs). Both microRNAs and lncRNAs have been shown to have a critical role in the regulation of cellular processes such as cell growth and apoptosis, as well as cancer progression and metastasis. Although it is well known that microRNAs can target a large number of protein-coding genes, little is known whether microRNAs can also target lncRNAs. In the present study, we determine whether miR-21 can regulate lncRNA expression. Using the lncRNA RT-PCR (reverse transcription-polymerase chain reaction) array carrying 83 human disease-related lncRNAs, we show that miR-21 is capable of suppressing the lncRNA growth arrest-specific 5 (GAS5). This negative correlation between miR-21 and GAS5 is also seen in breast tumor specimens. Of interest, GAS5 can also repress miR-21 expression. Whereas ectopic expression of GAS5 suppresses, GAS5-siRNA increases miR-21 expression. Importantly, there is a putative miR-21-binding site in exon 4 of GAS5; deletion of the miR-21-binding site abolishes this activity. Experiments with in vitro cell culture and xenograft mouse model suggest that GAS5 functions as a tumor suppressor. We further show that the biotin-labeled GAS5-RNA probe is able to pull down the key component (AGO2) of the RNA-induced silencing complex (RISC) and we subsequently identify miR-21 in this GAS5-RISC complex, implying that miR-21 and GAS5 may regulate each other in a way similar to the microRNA-mediated silencing of target mRNAs. Together, these results suggest that miR-21 targets not only tumor-suppressive protein-coding genes but also lncRNA GAS5.

Genetic heterogeneity of breast cancer metastasis may be related to miR-21 regulation of TIMP-3 in translation

Purpose. MicroRNAs are noncoding RNA molecules that posttranscriptionally regulated expression of target gene and implicate the progress of cancer proliferation, differentiation, and apoptosis. The aim of this study is to determine whether microRNA-21 (miR-21), a specific microRNA implicated in multiple aspects of carcinogenesis, promoted breast cancer metastasis by regulating the tissue inhibitor of metalloproteinase 3 (TIMP-3) gene. Methods. miR-21 of serum and tissue from 40 patients (30 patients with breast cancer) were detected by real-time quantitative reverse transcriptase polymerase chain reaction (RT-qPCR). TIMP-3 of tissue from the patient was tested by real-time RT-qPCR. Protein expression of TIMP-3 was evaluated by western blotting. Correlation analysis was performed between miR-21 and TIMP-3. Results. Of the 40 samples from tissue and serum analyzed, the miR-21 expression was significantly higher in high invasion metastasis group (HIMG) that in low invasion metastasis group (LIMG); the latter was higher than that in normal group (NG). Additionally, the TIMP-3 expression was significantly lower in HIMG than in LIMG; the latter was lower than that in NG. There was significantly inverse correlation between miR-21 and TIMP-3 extracted from tissue. Conclusion. Our data suggest that miR-21 could promote metastasis in breast cancer via the regulation of TIMP3 translation, and there was consistency between miR-21 of serum and miR-21 in tissue.

Primary sclerosing cholangitis and cholangiocarcinoma: pathogenesis and modes of diagnostics

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease caused by progressive inflammation of the intra- and extrahepatic bile duct system. PSC patients have an increased risk to develop hepatobiliary as well as extrahepatic malignancies. The goal of a surveillance strategy for hepatobiliary malignancy in these patients is the detection of early cancer which will allow a potentially curative therapy. Here, we focus on a conceptual review of the pathogenesis of cholangiocellular carcinoma and gallbladder cancer and we will discuss a rational approach for the surveillance of these malignancies in PSC patients.

Expression of microRNAs, miR-21, miR-31, miR-122, miR-145, miR-146a, miR-200c, miR-221, miR-222, and miR-223 in patients with hepatocellular carcinoma or intrahepatic cholangiocarcinoma and its prognostic significance

MicroRNAs are a class of non-coding molecules found to regulate a variety of cellular functions in health and disease. Dysregulation of microRNAs is involved in liver disease, especially hepatocarcinogenesis. Since primary hepatic malignancies are typically characterized by late diagnosis, frequent recurrence, and poor response to adjuvant therapy, there is a need for the discovery of novel biomarkers in order to achieve earlier diagnosis, predict tumor aggressiveness and response to adjuvant therapy. The purpose of this study is to evaluate the expression of certain microRNAs (miR-21, -31, -122, -145, -146a, - 200c, -221, -222 and -223) in patients with hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (ICC), as well as to assess their prognostic significance. Micro-RNA expression was assessed by reverse transcription and real-time PCR (RT-PCR). Clinicopathological data and survival rates were retrieved and analyzed. According to our results, miR-21, miR-31, miR-122, miR-221, miR-222 were significantly up-regulated in HCC tissues, whereas miR-145, miR-146a, miR-200c, and miR-223 were found to be down-regulated. Concerning ICC samples, miR-21, miR-31, and miR-223 were found to be over-expressed, whereas miR-122, miR-145, miR-200c, miR-221, and miR-222 were down-regulated. Additionally, expression of miR-21, miR-31, miR-122, and miR-221 in HCC correlated with cirrhosis, while miR-21 and miR-221 associated with tumor stage and poor prognosis. In ICC tissues, miR-21, miR-31, and miR-223 were found to be over-expressed, but no correlation with clinicopathological features was found.

Concomitant dysregulation of microRNAs miR-151-3p and miR-126 correlates with improved survival in resected cholangiocarcinoma

BACKGROUND

MicroRNAs (miRNAs) are small non-coding genes which become dysregulated in cancer and may predict survival. The role of miRNAs in outcomes in cholangiocarcinoma (CC) has not been reported.

METHODS

RNA was extracted from 32 resected CCs along with adjacent uninvolved bile duct epithelium. A total of 43 miRNAs were quantified using NanoString™. Clinicopathologic characteristics and outcomes were captured and compared. Overall survival curves were created using the Kaplan-Meier method; factors, including miRNA expression, were compared by log-rank, chi-squared or Cox regression analyses.

RESULTS

Absolute expression of each miRNA was compared with overall survival after excluding perioperative deaths (n= 3). One upregulated (miR-151-3p; P= 0.003) and one downregulated (miR-126; P= 0.023) miRNA in resected CC relative to adjacent normal bile duct epithelium correlated with survival on univariate analysis. Clinical factors and these miRNAs were compared. Dysregulated miR-151-3p and miR-126, respectively, were the only factors that correlated with improved overall survival [41.5 months vs. 12.3 months (P= 0.002) and 21.9 months vs. 15.1 months (P= 0.02), respectively]. In eight patients, both miRNAs were dysregulated. In the remainder, only one or neither showed dysregulation. Concomitant dysregulation correlated with the best overall survival (58.7 months vs. 15.1 months; P < 0.000; n= 8); clinicopathologic factors in these groups were otherwise similar.

CONCLUSIONS

In resected CC, the concomitant dysregulation of both miR-151-3p and miR-126 was the factor related to the greatest improvement in overall survival. Further analysis of the targets of these miRNAs may yield potential therapeutic targets or prognostic biomarkers.

miRNA-21 is dysregulated in response to vein grafting in multiple models and genetic ablation in mice attenuates neointima formation

Aims

The long-term failure of autologous saphenous vein bypass grafts due to neointimal thickening is a major clinical burden. Identifying novel strategies to prevent neointimal thickening is important. Thus, this study aimed to identify microRNAs (miRNAs) that are dysregulated during neointimal formation and determine their pathophysiological relevance following miRNA manipulation.

Methods and results

We undertook a microarray approach to identify dysregulated miRNAs following engraftment in an interpositional porcine graft model. These profiling experiments identified a number of miRNAs which were dysregulated following engraftment. miR-21 levels were substantially elevated following engraftment and these results were confirmed by quantitative real-time PCR in mouse, pig, and human models of vein graft neointimal formation. Genetic ablation of miR-21 in mice or grafted veins dramatically reduced neointimal formation in a mouse model of vein grafting. Furthermore, pharmacological knockdown of miR-21 in human veins resulted in target gene de-repression and a significant reduction in neointimal formation.

Conclusion

This is the first report demonstrating that miR-21 plays a pathological role in vein graft failure. Furthermore, we also provided evidence that knockdown of miR-21 has therapeutic potential for the prevention of pathological vein graft remodelling.

Downregulation of microRNA-138 enhances the proliferation, migration and invasion of cholangiocarcinoma cells through the upregulation of RhoC/p-ERK/MMP-2/MMP-9

microRNAs (miRs) play an important role in tumor initiation and progression in many types of cancer, including cholangiocarcinoma (CC). miR-138 dysregulation is frequently observed in a variety of tumors. In the present study, miR-138 was found to be downregulated in CC tissues by quantitative real-time RT-PCR. Furthermore, its potential target molecule, Ras homolog gene family, member C (RhoC) protein, was found to be highly expressed in CC tissues examined by western blot analysis. Luciferase reporter assay further demonstrated that miR-138 directly targeted RhoC. We found that the introduction of miR-138 mimics to RBE and QBC939 CC cells could reduced RhoC mRNA and protein expression, and suppressed the proliferation, G1/S transition, migration and invasion of CC cells. However, transfection with a miR-138 inhibitor induced an inverse effect in CC cells. The expression of phosphorylated extracellular signal-regulated kinase (p-ERK), matrix metalloproteinase (MMP)-2 and MMP-9 decreased following transfection with miR-138, and increased following transfection with miR-138 inhibitor in CC cells. In conclusion, RhoC upregulation induced by miR-138 downregulation promotes the malignant progression of CC cells and the underlying mechanisms of this effect involve the increase in the expression of p-ERK/MMP-2/MMP-9. Consequently, miR-138/RhoC is a potential target for the clinical diagnosis and treatment of CC.

Overexpression of microRNA-21 regulating PDCD4 during tumorigenesis of liver fluke-associated cholangiocarcinoma contributes to tumor growth and metastasis

MicroRNA, an endogenous noncoding RNA modulating gene expression, is a key molecule that by its dysregulation plays roles in inflammatory-driven carcinogenesis. This study aimed to investigate the role of oncomiR miR-21 and its target, the programmed cell death 4 (PDCD4) in tumor growth and metastasis of the liver fluke Opisthorchis viverrini-associated cholangiocarcinoma (CCA). The expression levels of miR-21 and PDCD4 were analyzed using the TaqMan miRNA expression assay and immunohistochemistry in liver tissues of both O. viverrini plus N-nitrosodimethylamine (NDMA)-treated hamsters and human CCA samples (n=23 cases). The functional assay for miR-21 was performed in CCA cell lines by the anti-miR-21 and pre-miR-21 transfection procedures. The peak of miR-21 levels were reached at 2 (hyperplastic lesions) and 6 (CCA) months of the O. viverrini plus NDMA-induced group and had a reverse response with its target PDCD4 proteins. In human CCA, miR-21 was overexpressed in tumor tissues when compared with nontumor tissues (P=0.0034) and had a negative correlation with PDCD4 protein (P=0.026). It was also found that high expression of miR-21 was significantly correlated with shorter survival (P<0.05) and lymph node metastasis (P=0.037) of CCA patients. Transient transfection of pre-miR-21 reduced the PDCD4 level and resulted in an increase of M213 CCA cell growth and wound-induced migration ability. These results indicated that miR-21 plays a role in the carcinogenesis and metastasis of O. viverrini-associated CCA by suppressing the function of PDCD4. Modulation of aberrantly expressed miR-21 may be a useful strategy to inhibit tumor cell phenotypes or improve response to chemotherapy.

miR-370 modulates insulin receptor substrate-1 expression and inhibits the tumor phenotypes of oral carcinoma

BACKGROUND

MicroRNAs play important roles in carcinogenesis. A preliminary screening study suggested that down-regulation of miR-370 occurs in oral squamous cell carcinoma (OSCC) tissue. Insulin receptor substratre-1 (IRS-1) is the substrate of insulin-like growth factor receptor (IGFR), which modulates AKT/mTOR activation in malignancies. The relationship between miR-370 and IRS-1, and their functional roles in OSCC pathogenesis are unclear.

MATERIALS AND METHODS

Primary OSCC specimens were examined for miR-370 expression. Exogenous expression of miR-370 was established using both stable subclones and transient expression, and these were used to gain insights into miR-370's functions in OSCC cells. Knockdown of miR-370 and IRS-1 was also carried out in OSCC cells using a small interference oligonucleotide approach.

RESULTS

Squamous cell carcinoma tissues with perineural invasion had lowered miR-370 expression compared with contrasting OSCC. OSCC cells also exhibited lower miR-370 expression than normal oral keratinocytes, and this can be reversed by treatment with 5-aza-2'-deoxycytidine. Exogenous miR-370 expression decreases the migration and anchorage-independent growth of OSCC cells, which implies a suppressor role for miR-370. The enhancement of anchorage-independent growth of OSCC cells through miR-370 inhibiting can be reduced by knockdown of IRS-1 expression.

CONCLUSION

This study concludes that miR-370 is able to target IRS-1 for oral tumorigenesis.

A microRNA component of the neoplastic microenvironment: microregulators with far-reaching impact

The interplay between tumor cells and their microenvironment plays a pivotal role in tumor development and progression. Although a growing body of evidence has established the importance of the tumor microenvironment, an understanding of the crosstalk between its components and cancer cells remains elusive. The pathways triggered by microenvironmental factors could modulate cancer-related gene transcription, also affecting small noncoding RNAs, microRNAs, which have emerged as key posttranscriptional regulators of gene expression, directly involved in human cancers. Although microRNAs regulate most biological mechanisms, their role in the tumor microenvironment has only recently become the focus of intense research. In this paper, we focus on the intertwined connection between the tumor microenvironment and aberrant expression of microRNAs involved in carcinogenesis. We also discuss the emerging roles of microRNAs in the tumor microenvironment as it relates to cancer progression. We conclude that microRNAs are critical for our understanding of the development of cancer, and that targeting microRNA signaling pathways in the microenvironment as well as in tumor cells opens new therapeutic avenues to the global control of cancer.

MicroRNAs in biliary diseases

Cholangiopathies are a group of diseases primarily or secondarily affecting bile duct cells, and result in cholangiocyte proliferation, regression, and/or transformation. Their etiopathogenesis may be associated with a broad variety of causes of different nature, which includes genetic, neoplastic, immune-associated, infectious, vascular, and drug-induced alterations, or being idiopathic. miRNAs, small non-coding endogenous RNAs that post-transcriptionally regulate gene expression, have been associated with pathophysiological processes in different organs and cell types, and are postulated as potential targets for diagnosis and therapy. In the current manuscript, knowledge regarding the role of miRNAs in the development and/or progression of cholangiopathies has been reviewed and the most relevant findings in this promising field of hepatology have been highlighted.

MiR-21 regulates biological behavior through the PTEN/PI-3 K/Akt signaling pathway in human colorectal cancer cells

The aim of this study was to determine a role of microRNA-21 (miR-21) in colorectal cancer (CRC) and to elucidate the regulation of phosphatase and tensin homologue (PTEN) gene by miR-21. MiR-21 expression was investigated in 30 CRC samples and five CRC cell lines. In this study, we show that the expression of miR-21 was overexpressed in CRC compared with adenomas and normal tissues. Patients with poor differentiation, lymph node metastasis and advanced TNM stage showed significantly high expression of miR-21. Inhibition of miR-21 in the HCT116 cell line reduced cellular proliferation, migration and invasion, induced apoptosis and inhibited cell cycle progression. The PTEN protein levels in CRC tissues and cells had an inverse correlation with miR-21 expression. Anti-miR-21-transfected cells increased PTEN protein expression without changing the PTEN mRNA level and increased a luciferase-reporter activity. MiR-21 targets PTEN at the post-transcriptional level and regulates cell proliferation and invasion in CRC. It may serve as a novel therapeutic target in CRC.

miRNAs regulate expression and function of extracellular matrix molecules

MicroRNAs (miRNAs) are a family of small non-coding RNA molecules that are made up of 18-25 nucleotides that function in post-transcriptional gene regulation. The expression of miRNAs is highly conserved and essential in regulating many cellular processes including formation, maintenance and the remodelling of the extracellular matrix (ECM). In this review, we examine different ECM molecules and the miRNAs involved in regulating their abundance and how these changes influence cell phenotype. For example, miRNAs and their target messenger RNAs (mRNAs) are involved in cell adhesion, by regulating the synthesis and turnover of key ECM adhesion molecules and their receptors including cadherins, integrins and other non-integrin ECM receptors. Other miRNAs regulate the abundance of cytokines and growth factors which in turn stimulate cells to synthesize and secrete specialized ECMs. For example, miR-125a/b and miR-146a and their downstream target mRNAs influence the production of the epidermal growth factor family which has a significant impact on the nature of the ECM formed. miRNAs affect structural ECM proteins important in the assembly, composition and organization of the ECM. Proteins such as collagen, fibronectin, versican, and nephronectin are targeted by several miRNAs. miRNAs can also control the expression of proteins such as matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs), which are involved in ECM remodelling and are important for tissue development, cell motility and wound healing. It has become clear that many different miRNAs control the balance in ECM composition that determines normal tissue function and alterations in the expression of these miRNAs can lead to pathological consequences.

MicroRNAs in cancer diagnosis and therapy: from bench to bedside

Epigenetic changes, such as DNA methylation and histone modifications, regulate gene expression. It is speculated that investigating the fundamental epigenetic mechanisms and their gene regulation will promote a better understanding of cancer development. The idea of epigenetic modification has been extended to microRNAs (miRs). MiRs are single-stranded RNA molecules, about 19-25 ribonucleotides in length, which regulate gene expression post-transcriptionally and can act as tumor suppressors or oncogenes. We review the most recent findings related to their mechanisms of action, the modification of miR expression, and their relationship to cancer. We also discuss the potential application of miRs in the clinical setting, such as for biomarkers and therapy.

Clinical correlations of miR-21 expression in colorectal cancer patients and effects of its inhibition on DLD1 colon cancer cells

PURPOSE

MicroRNA-21 (miR-21) is one of the miRNAs that are frequently and highly overexpressed in tumor tissue of colorectal cancer (CRC) patients; however, only a little is known about its functional role in CRC.

METHODS

We examined the expression level of miR-21 in 44 paired samples of tumoral and non-tumoral colon tissues diagnosed for CRC using TaqMan real-time PCR method. Furthermore, we used miR-21 inhibitor (anti-miR-21) to transient knockdown of miR-21 in DLD-1 colon cancer cells and examined the effects of miR-21 silencing on viability, apoptosis, chemosensitivity, cell cycle, and migration of DLD1 cells.

RESULTS

The expression levels of miR-21 were significantly increased in CRC tumor tissue (P < 0.0001). Significant differences in miR-21 levels were observed also between CRC tissues of patients with CRC in different clinical stages: I vs. II (P = 0.033) and I vs. IV (P = 0.021). Kaplan-Meier analysis proved that the miR-21 expression levels are correlated to shorter overall survival of CRC patients (P = 0.0341). MiR-21 silencing in DLD1 cell line had no effect on the cell viability; however, when combined with chemotherapeutics (5-FU, L-OHP, and SN38), it contributed to the decrease of cell viability. Suppression of miR-21 decreased cell migration ability of DLD-1 cells by nearly 30 % (P = 0.016).

CONCLUSION

We have confirmed the overexpression of miR-21 in CRC samples and its correlation with advanced disease and shorter overall survival. These findings could be described in part by the fact that CRC cells with increased expression of miR-21 have higher migration ability.

Silencing of miR-370 in human cholangiocarcinoma by allelic loss and interleukin-6 induced maternal to paternal epigenotype switch

Cholangiocarcinoma (CCA) is a highly lethal malignant tumor arising from the biliary tract epithelium. Interleukin-6 (IL-6) is a major mediator of inflammation and contributor to carcinogenesis within the biliary tree. Previous studies suggested that enforced IL-6 contributes to cholangiocarcinogenesis through hypermethylation of several genes implicated in CCA. However, the precise mechanisms of IL-6 effects in CCA remain unclear. We now demonstrate that microRNA (miR)-370 is underexpressed in a large cohort of human CCA vs. normal liver tissues. In addition, we show that IL-6 induces a time-dependent silencing of miR-370. In addition, demethylation of CCA cells results in upregulation of miR-370. Furthermore, we demonstrate that miR-370 is imprinted, and that the Intergenic Differentially Methylated Region (IG-DMR) responsible for imprinting regulation of this genomic locus is hypermethylated in response to IL-6 treatment. In addition, the IG-DMR is hypermethylated in human CCA specimens compared to normal matched controls, in the same location as the IL-6 induced hypermethylation. Finally, miR-370 was found to regulate WNT10B in luciferase as well as western blotting experiments. Our data indicate that the paternal allele of miR-370 is normally silenced through genomic imprinting and that the overexpression of IL-6 in CCA effectively suppresses the expression of miR-370 from the maternal allele, lending support to the theory that miR-370 silencing in human CCA follows a classic two-hit mechanism.

MicroRNA-520e suppresses growth of hepatoma cells by targeting the NF-κB-inducing kinase (NIK)

MicroRNAs (miRNAs) are small, non-coding RNAs that can act as oncogenes or tumor suppressor genes in human cancer. Emerging evidence indicates that deregulation of miRNAs contributes to the hepatocarcinogenesis. In the present study, we demonstrated that the levels of miR-520e were dramatically decreased in examined hepatoma cell lines and clinical hepatocellular carcinoma (HCC) tissues. Moreover, we found that DNA hypermethylation in the upstream region of miR-520e resulted in the downregulation of miR-520e. Next, we demonstrated that introduction of miR-520e dramatically suppressed the growth of hepatoma cells in vitro and in vivo, whereas silencing the expression of miR-520e by anti-miR-520e resulted in a promoted cell proliferation, suggesting that miR-520e may be a novel tumor suppressor. Further studies revealed that NF-κB-inducing kinase (NIK) was one of the direct target genes of miR-520e, as miR-520e directly bound to the 3'untranslated region of NIK, which reduced the expression of NIK at the levels of mRNA and protein. Moreover, silencing of NIK was able to inhibit the growth of hepatoma cells, similar to the effect of miR-520e overexpression on growth of hepatoma cells. Meanwhile, the knockdown of NIK expression reversed the enhanced proliferation mediated by anti-miR-520e. In addition, miR-520e significantly decreased the phosphorylation of ERK1/2 (p-ERK1/2) and depressed the transcriptional activity and nuclear translocation of nuclear factor κB (NF-κB) (p65). These results suggest that miR-520e suppresses the growth of hepatoma cells by targeting NIK involving the NIK/p-ERK1/2/NF-κB signaling pathway. Finally, we showed that the intratumoral injection with miR-520e was able to directly repress the growth of hepatoma cells in the nude mice. Thus, our finding provides new insight into the mechanism of hepatocarcinogenesis, indicating a therapeutic potential of miR-520e in the treatment of HCC.

Biliary tract carcinomas: from chemotherapy to targeted therapy

Biliary tract carcinomas (BTC) are a group of tumours arising from the epithelial cells of intra- and extra-hepatic biliaryducts and the gallbladder, characterised by a poor prognosis. Surgery is the only curative procedure, but the risk of recurrence is high and furthermore, the majority of patients present with unresectable disease at the time of diagnosis. Systemic therapy is the mainstay of treatment for patients who present recurrent or metastatic disease. Progress has been made in the last decade to identify the most effective chemotherapy regimens, with the recent recommendation of the combination of gemcitabine-cisplatin as the standard schedule. Comprehension of the molecular basis of cholangiocarcinogenesis and tumour progression has recently led to the experimentation of targeted therapies in patients with BTC, demonstrating promising results. In this review we will discuss the clinical experience with systemic treatment for BTC, focusing on future directions with targeted therapies.

Coordinated effects of microRNA-494 induce G₂/M arrest in human cholangiocarcinoma

MicroRNA (miRs) have emerged as salient regulators in cancer homeostasis and, recently, as putative therapeutics. Cholangiocarcinomas (CCA) are aggressive cancers with survival usually measured in months. mRNA arrays followed by pathway analysis revealed that miR-494 is a major modulator of the cell cycle progression from gap 2 (G₂) to mitosis (M). We performed fluorescence activated cell sorting (FACS) as well as differential interference contrast (DIC) microscopy, and confirmed that miR-494 induces a significant arrest in G₂/M in CCA cells. Furthermore, we verified that miR-494 modulates the protein level of six genes involved in the G₂/M transition: Polo-like Kinase 1 (PLK1), pituitary tumor-transforming gene 1 (PTTG1), Cyclin B1 (CCNB1), cell-division cycle 2 (CDC2), cell-division cycle 20 (CDC20) and topoisomerase II α (TOP2A). Next, we identified direct binding of miR-494 to the open reading frame (ORF) and downregulation of PTTG1 and TOP2A. In summary, our findings suggest that miR-494 has a global regulatory role in cell cycle progression, exerted by concerted effects on multiple proteins involved in gap 1 (G₁) to synthesis (S), as described previously, as well as G₂ to M progression. Therefore, it appears that the simultaneous effects of a single miR species on multiple targets along the same canonical pathway is advantageous for the usage of miRs as therapeutics. In addition, our data suggest that miRs act within a narrow range. miR expression above the upper threshold does not appear to induce further effects, which is reassuring in terms of off-target effects of miR surrounding noncancerous tissue.

MicroRNA-21 inhibits Serpini1, a gene with novel tumour suppressive effects in gastric cancer

BACKGROUND

A thorough understanding of gastric cancer at the molecular level is urgently needed. One prominent oncogenic microRNA, miR-21, was previously reported to be upregulated in gastric cancer.

METHODS

We performed an unbiased search for downstream messenger RNA targets of miR-21, based on miR-21 dysregulation, by using human tissue specimens and the MKN28 human gastric carcinoma cell line. Molecular techniques include microRNA microarrays, cDNA microarrays, qRT-PCR for miR and mRNA expression, transfection of MKN28 with miR-21 inhibitor or Serpini1 followed by Western blotting, cell cycle analysis by flow cytometry and luciferase reporter assay.

RESULTS

This search identified Serpini1 as a putative miR-21 target. Luciferase assays demonstrated direct interaction between miR-21 and Serpini1 3'UTR. miR-21 and Serpini1 expression levels were inversely correlated in a subgroup of gastric cancers, suggesting a regulatory mechanism that included both of these molecules. Furthermore, Serpini1 induced growth retardation of MKN28 and induced vigorous G1/S arrest suggesting its potential tumour-suppressive function in the stomach.

CONCLUSION

Taken together, these data suggest that in a subgroup of gastric cancers, miR-21 is upregulated, inducing downregulation of Serpini1, which in turn releases the G1-S transition checkpoint, with the end result being increased tumour growth.

MicroRNAs in liver disease

MicroRNAs are small noncoding RNA molecules that regulate gene expression posttranscriptionally through complementary base pairing with thousands of messenger RNAs. They regulate diverse physiological, developmental, and pathophysiological processes. Recent studies have uncovered the contribution of microRNAs to the pathogenesis of many human diseases, including liver diseases. Moreover, microRNAs have been identified as biomarkers that can often be detected in the systemic circulation. We review the role of microRNAs in liver physiology and pathophysiology, focusing on viral hepatitis, liver fibrosis, and cancer. We also discuss microRNAs as diagnostic and prognostic markers and microRNA-based therapeutic approaches for liver disease.

MicroRNA in cancer: new hopes for antineoplastic chemotherapy

MicroRNAs (miRNAs) are a class of endogenous non-coding small RNAs that are evolutionarily conserved and widely distributed among species. Their major function is to negatively regulate mRNA target genes, and miRNA expression has been found to be deregulated in all human cancers, where miRNAs play critical roles in tumorigenesis, functioning either as tumor suppressors or as oncogenes. This review provides a current overview of the connection between miRNAs and cancer by covering the recent advances in miRNA involvement in human cancer including initiation, growth, invasion, and metastasis. We will also highlight the literature where application of miRNAs has created the foundation for the development of potential future miRNA therapy.

Genetic profiling of intrahepatic cholangiocarcinoma

PURPOSE OF REVIEW

Intrahepatic cholangiocarcinoma (ICC) is a treatment-refractory disease with a dismal outcome. Limited success in the clinical management and a persistent increase in the incidence world-wide have made ICC one of the most lethal and fastest growing malignancies. However, recent advancements in genome-wide technologies combined with the application of integrative multidimensional analytical approaches have begun to provide both detailed insight into the underlying biological traits of ICC and identified new therapeutic opportunities.

RECENT FINDINGS

In comparison with other cancers, genomic studies of ICC have been limited. We and others have recently procured large cohorts of ICC patients intended for genome-wide analyses. In our study, samples from ICC patients were obtained from three cancer centers and subjected to integrated genetic and genomic analyses. We provided new insights into both pathogenesis and optimal treatment options demonstrating the presence of unique subclasses of patients, based partly on KRAS mutations and increased levels of receptor tyrosine kinase signaling. The group of patients with the worst prognosis was characterized by transcriptional enrichment of genes regulating inflammation and proteasome activities, suggesting a combination of tyrosine kinase inhibitors and anti-inflammatory drugs as a new therapeutic option for these patients.

SUMMARY

We have critically examined the progress in genome-wide studies of ICC including genetic profiling, transcriptomics, and epigenomics. Current limitations in applying these technologies to archival samples and the insufficient access to fresh-frozen material are partly the cause of the delayed implementation of the omics-based investigations of ICC compared to other hepatobiliary diseases. Thus, selected candidate single-gene studies will also be discussed.

MicroRNA dysregulation during chemical carcinogenesis

MicroRNAs, potent negative modulators of gene expression, are involved in the regulation of fundamental cellular processes, including cell differentiation, metabolic regulation, signal transduction, cell proliferation and apoptosis. Aberrant levels of miRNAs have been documented in all major human cancers, leading to the suggestion that deregulation of miRNA expression might be significant in tumorigenesis. This review presents the current evidence that demonstrates the involvement of miRNA deregulation in the early stages of lung, liver and breast carcinogenesis induced by chemical carcinogens, suggesting their major role as contributors to the pathogenesis of cancer.

Comprehensive review of the diagnosis and treatment of biliary tract cancer 2012. Part I: diagnosis-clinical staging and pathology

Biliary tract cancers (gallbladder cancer, intra- and extra-hepatic cholangiocarcinoma, and selected periampullary cancers) accounted for 12,760 new cases of cancer in the USA in 2010. These tumors have a dismal prognosis with most patients presenting with advanced disease. Early, accurate diagnosis is essential, both for potential cure where possible and for optimal palliative therapy in all others. This review examines the currently available and emerging technologies for diagnosis and treatment of this group of diseases.

miR-25 targets TNF-related apoptosis inducing ligand (TRAIL) death receptor-4 and promotes apoptosis resistance in cholangiocarcinoma

It has been established that microRNA expression and function contribute to phenotypic features of malignant cells, including resistance to apoptosis. Although targets and functional roles for a number of microRNAs have been described in cholangiocarcinoma, many additional microRNAs dysregulated in this tumor have not been assigned functional roles. In this study, we identify elevated miR-25 expression in malignant cholangiocarcinoma cell lines as well as patient samples. In cultured cells, treatment with the Smoothened inhibitor, cyclopamine, reduced miR-25 expression, suggesting Hedgehog signaling stimulates miR-25 production. Functionally, miR-25 was shown to protect cells against TNF-related apoptosis-inducing ligand (TRAIL)-induced apoptosis. Correspondingly, antagonism of miR-25 in culture sensitized cells to apoptotic death. Computational analysis identified the TRAIL Death Receptor-4 (DR4) as a potential novel miR-25 target, and this prediction was confirmed by immunoblot, cell staining, and reporter assays.

CONCLUSION

These data implicate elevated miR-25 levels in the control of tumor cell apoptosis in cholangiocarcinoma. The identification of the novel miR-25 target DR4 provides a mechanism by which miR-25 contributes to evasion of TRAIL-induced cholangiocarcinoma apoptosis.

Electrochemical determination of microRNA-21 based on graphene, LNA integrated molecular beacon, AuNPs and biotin multifunctional bio bar codes and enzymatic assay system

MicroRNAs (miRNAs), a kind of small, endogenous, noncoding RNAs (∼22 nucleotides), might play a crucial role in early cancer diagnose due to its abnormal expression in many solid tumors. As a result, label-free and PCR-amplification-free assay for miRNAs is of great significance. In this work, a highly sensitive biosensor for sequence specific miRNA-21 detection without miRNA-21 labeling and enrichment was constructed based on the substrate electrode of dendritic gold nanostructure (DenAu) and graphene nanosheets modified glassy carbon electrode. Sulfydryl functionalized locked nucleic acid (LNA) integrated hairpin molecule beacon (MB) probe was used as miRNA-21 capture probe. After hybridized with miRNA-21 and reported DNA loading in gold nanoparticles (AuNPs) and biotin multi-functionalized bio bar codes, streptavidin-HRP was brought to the electrode through the specific interaction with biotin to catalyze the chemical oxidation of hydroquinone by H(2)O(2) to form benzoquinone. The electrochemical reduction signal of benzoquinone was utilized to monitor the miRNA-21 hybridization event. The effect of experimental variables on the amperometric response was investigated and optimized. Based on the specific confirmation of probe and signal amplification, the biosensor showed excellent selectivity and high sensitivity with low detection limit of 0.06 pM. Successful attempts are made in miRNA-21 expression analysis of human hepatocarcinoma BEL-7402 cells and normal human hepatic L02 cells.

Association of microRNA-21 expression with its targets, PDCD4 and TIMP3, in pancreatic ductal adenocarcinoma

Since the discovery of small non-coding RNAs, the analyses of microRNA (miRNA) expression patterns in human cancer have provided new insights into cancer biology. miRNA-21 has been suggested to be one of the miRNAs that have an important role in the development or biological behavior of a variety of malignancies, including pancreatic cancer. This study was conducted to evaluate the relationship between the expression of miRNA-21 and that of its molecular targets, programmed cell death 4 (PDCD4) and tissue inhibitor of metalloproteinase (TIMP3), in pancreatic ductal adenocarcinoma. The study included 65 pancreatic ductal adenocarcinomas and 5 normal pancreatic tissue specimens for comparison. The miRNA expression profiling of five selected pancreatic ductal adenocarcinomas and five normal pancreatic specimens was performed using a microarray platform, and was evaluated by a hierarchical clustering analysis. The miRNA most highly expressed in pancreatic ductal adenocarcinomas (ie, miRNA-21) was further assessed by quantitative real-time reverse transcription PCR (RT-PCR) assays in the 65 pancreatic ductal adenocarcinoma cases. The expression pattern of its molecular targets (eg, PDCD4 and TIMP3) in pancreatic ductal adenocarcinoma was examined immunohistochemically. In the microarray analyses, 28 miRNAs were upregulated in pancreatic ductal adenocarcinoma compared with normal pancreatic tissue, whereas 48 miRNAs were downregulated. miRNA-21 was the most significantly overexpressed miRNA in the pancreatic ductal adenocarcinomas analyzed, and was also highly expressed in 75% of the 65 pancreatic ductal adenocarcinomas examined by real-time RT-PCR. High miRNA-21 expression was correlated with a worse prognosis in the pancreatic ductal adenocarcinoma patients (P=0.045). The immunohistochemical expression patterns of PDCD4 (reduced nuclear staining pattern) and TIMP3 (downregulated expression) were significantly associated with both the upregulated miR-21 expression (P<0.05) and the poor survival of the patients (P<0.001 and P=0.001, respectively). Our data suggest that an overexpression of miRNA-21 is, therefore, associated with the biological behavior of pancreatic ductal adenocarcinoma via the downregulation of the expression of tumor suppressors, PDCD4 and TIMP3, thus resulting in tumor progression and the adverse clinical course of pancreatic ductal adenocarcinoma.

Circulating microRNA-21 as a novel biomarker for hepatocellular carcinoma

BACKGROUND & AIMS

Several groups have reported the significance of circulating microRNA as a biochemical marker of cancer. To our knowledge, however, there are no reports on the significance of circulating microRNA in hepatocellular carcinoma. The aim of this study was to evaluate the significance of plasma microRNA-21 level as a biochemical marker for hepatocellular carcinoma.

METHODS

Plasma microRNA-21 level was measured by qRT-PCR in 10 patients before and after curative resection of hepatocellular carcinoma. Plasma microRNA-21 was also compared in other groups of: 126 patients with hepatocellular carcinoma, 30 patients with chronic hepatitis, and 50 healthy volunteers. The power of microRNA-21 in differentiating hepatocellular carcinoma from chronic hepatitis or from healthy volunteers was compared to that of α-fetoprotein.

RESULTS

In the 10-patient group, plasma microRNA-21 levels significantly diminished after surgery compared with the pre-operative values (p=0.0125). Plasma microRNA-21 level in the 126 patients with hepatocellular carcinoma was significantly higher than in patients with chronic hepatitis and healthy volunteers (p<0.0001, p<0.0001, respectively). ROC analysis of plasma microRNA-21 yielded an AUC of 0.773 with 61.1% sensitivity and 83.3% specificity when differentiating hepatocellular carcinoma from chronic hepatitis, and an AUC of 0.953 with 87.3% sensitivity and 92.0% specificity when differentiating hepatocellular carcinoma from healthy volunteers. Both sets of values were superior to α-fetoprotein and improved for the combination of microRNA-21 and α-fetoprotein.

CONCLUSIONS

Plasma microRNA-21 level is a promising biochemical marker for hepatocellular carcinoma.

miRNAs in breast cancer tumorigenesis (Review)

miRNAs are small, endogenous, non-coding RNAs that negatively regulate protein-coding mRNAs at the post-transcriptional level. It is estimated that in humans thousands of miRNAs are expressed and more than 700 miRNAs have been described to date. About 50% of annotated human miRNAs are detected in regions of fragile sites, which are associated with cancer. The available evidence has shown that miRNAs widely participate in the development or progression of many types of cancers, including breast cancer. The role of miRNAs in breast cancer has been widely investigated; here, we will focus on what is known about the working mechanism of miRNAs in different stages of breast cancer development.

MicroRNA down-regulated in human cholangiocarcinoma control cell cycle through multiple targets involved in the G1/S checkpoint

MicroRNAs (miRs) recently emerged as prominent regulators of cancer processes. In the current study we aimed at elucidating regulatory pathways and mechanisms through which miR-494, one of the miR species found to be down-regulated in cholangiocarcinoma (CCA), participates in cancer homeostasis. miR-494 was identified as down-regulated in CCA based on miR arrays. Its expression was verified with quantitative real-time reverse-transcription polymerase chain reaction (qRT-PCR). To enforce miR expression, we employed both transfection methods, as well as a retroviral construct to stably overexpress miR-494. Up-regulation of miR-494 in cancer cells decreased growth, consistent with a functional role. mRNA arrays of cells treated with miR-494, followed by pathway analysis, suggested that miR-494 impacts cell cycle regulation. Cell cycle analyses demonstrated that miR-494 induces a significant G1/S checkpoint reinforcement. Further analyses demonstrated that miR-494 down-regulates multiple molecules involved in this transition checkpoint. Luciferase reporter assays demonstrated a direct interaction between miR-494 and the 3'-untranslated region of cyclin-dependent kinase 6 (CDK6). Last, xenograft experiments demonstrated that miR-494 induces a significant cancer growth retardation in vivo.

CONCLUSION

Our findings demonstrate that miR-494 is down-regulated in CCA and that its up-regulation induces cancer cell growth retardation through multiple targets involved in the G1-S transition. These findings support the paradigm that miRs are salient cellular signaling pathway modulators, and thus represent attractive therapeutic targets. miR-494 emerges as an important regulator of CCA growth and its further study may lead to the development of novel therapeutics.

MicroRNA-21 suppression impedes medulloblastoma cell migration

Medulloblastoma (MB), the most common malignant brain tumour in children, is characterised by a high risk of leptomeningeal dissemination. But little is known about the molecular mechanisms that promote cancer cell migration in MB. Aberrant expression of miR-21 is recognised to be causatively linked to metastasis in a variety of human neoplasms including brain tumours; however its function in MB is still unknown. In this study we investigated the expression level and the role of miR-21 in MB cell migration. miR-21 was found to be up-regulated, compared to normal cerebellum, in 29/29 MB primary samples and 6/6 MB-derived cell lines. Inverse correlation was observed between miR-21 expression and the metastasis suppressor PDCD4, while miR-21 repression increased the release of PDCD4 protein, suggesting negative regulation of PDCD4 by miR-21 in MB cells. Anti-miR-21 decreased protein expression of the tumour cell invasion mediators MAP4K1 and JNK, which are also known to be negatively regulated by PDCD4, and down-regulated integrin protein that is essential for MB leptomeningeal dissemination. Moreover miR-21 knockdown in MB cells increased the expression of two eminent negative modulators of cancer cell migration, E-Cadherin and TIMP2 proteins that are known to be positively regulated by PDCD4. Finally and importantly, suppression of miR-21 decreased the motility of MB cells and reduced their migration across basement membranes in vitro. Together, these compelling data propose miR-21 pathway as a novel mechanism impacting MB cell dissemination and raises the possibility that curability of selected MB may be improved by pharmaceutical strategies directed towards microRNA-21.

MicroRNA-mediated breast cancer metastasis: from primary site to distant organs

The recent upsurge of interest in microRNA (miRNA) is partly attributed to the discovery of the novel roles of miRNAs in many physiological and pathological processes, including tumor development. Research on breast cancer metastasis has also focused on the concept of miRNA, which can act either as promoters or as suppressors of metastases. This review will focus on a series of recent studies that demonstrate the involvement of miRNAs in breast cancer metastasis and will briefly describe various pathways of miRNA-regulated metastasis. Finally, future prospects will be discussed for the potential role of miRNAs as predictive markers and therapeutic agents for patients with breast cancer metastases.

Downregulation of Pdcd4 by mir-21 facilitates glioblastoma proliferation in vivo

MicroRNAs (miRNAs) are small, noncoding RNAs that play a critical role in developmental and physiological processes and are implicated in the pathogenesis of several human diseases, including cancer. They function by regulating target gene expression post-transcriptionally. In this study, we examined the role of oncogenic mir-21 in the pathogenesis of glioblastoma, the most aggressive form of primary brain tumor. We have previously reported that mir-21 is expressed at higher levels in primary glioblastoma-tissue and glioblastoma-derived cell lines than in normal brain tissue. We demonstrate that downregulation of mir-21 in glioblastoma-derived cell lines results in increased expression of its target, programmed cell death 4 (Pdcd4), a known tumor-suppressor gene. In addition, our data indicate that either downregulation of mir-21 or overexpression of its target, Pdcd4, in glioblastoma-derived cell lines leads to decreased proliferation, increased apoptosis, and decreased colony formation in soft agar. Using a glioblastoma xenograft model in immune-deficient nude mice, we observe that glioblastoma-derived cell lines in which mir-21 levels are downregulated or Pdcd4 is over-expressed exhibit decreased tumor formation and growth. Significantly, tumors grow when the glioblastoma-derived cell lines are transfected with anti-mir-21 and siRNA to Pdcd4, confirming that the tumor growth is specifically regulated by Pdcd4. These critical in vivo findings demonstrate an important functional linkage between mir-21 and Pdcd4 and further elucidate the molecular mechanisms by which the known high level of mir-21 expression in glioblastoma can attribute to tumorigenesis--namely, inhibition of Pdcd4 and its tumor-suppressive functions.

Real-time PCR-based analysis of the human bile microRNAome identifies miR-9 as a potential diagnostic biomarker for biliary tract cancer

Biliary tract cancer (BTC) is often difficult to diagnose definitively, even through histological examination. MicroRNAs (miRNAs) regulate a variety of physiological processes. In recent years, it has been suggested that profiles for circulating miRNAs, as well as those for tissue miRNAs, have the potential to be used as diagnostic biomarkers for cancer. The aim of this study was to confirm the existence of miRNAs in human bile and to assess their potential as clinical biomarkers for BTC. We sampled bile from patients who underwent biliary drainage for biliary diseases such as BTC and choledocholithiasis. PCR-based miRNA detection and miRNA cloning were performed to identify bile miRNAs. Using high-throughput real-time PCR-based miRNA microarrays, the expression profiles of 667 miRNAs were compared in patients with malignant disease (n = 9) and age-matched patients with the benign disease choledocholithiasis (n = 9). We subsequently characterized bile miRNAs in terms of stability and localization. Through cloning and using PCR methods, we confirmed that miRNAs exist in bile. Differential analysis of bile miRNAs demonstrated that 10 of the 667 miRNAs were significantly more highly expressed in the malignant group than in the benign group at P<0.0005. Setting the specificity threshold to 100% showed that some miRNAs (miR-9, miR-302c*, miR-199a-3p and miR-222*) had a sensitivity level of 88.9%, and receiver-operating characteristic analysis demonstrated that miR-9 and miR-145* could be useful diagnostic markers for BTC. Moreover, we verified the long-term stability of miRNAs in bile, a characteristic that makes them suitable for diagnostic use in clinical settings. We also confirmed that bile miRNAs are localized to the malignant/benign biliary epithelia. These findings suggest that bile miRNAs could be informative biomarkers for hepatobiliary disease and that some miRNAs, particularly miR-9, may be helpful in the diagnosis and clinical management of BTC.

Banking on the future: biobanking for "omics" approaches to biomarker discovery for Opisthorchis-induced cholangiocarcinoma in Thailand

Cholangiocarcinoma (CCA)--bile duct cancer--is associated with late presentation, poses challenges for diagnosis, and has high mortality. These features t highlight the desperate need for biomarkers than can be measured early and in accessible body fluids such as plasma of people at risk for developing this lethal cancer. In this manuscript, we address previous limitations in the discovery stage of biomarker(s) for CCA and indicate how new generation of "omics" technologies could be used for biomarker discovery in Thailand. A key factor in the success of this biomarker program for CCA is the combination of cutting edge technology with strategic sample acquisition by a biorepositories.

Epigenetics: principles and practice

Epigenetics is defined as heritable changes in gene expression that are, unlike mutations, not attributable to alterations in the sequence of DNA. The predominant epigenetic mechanisms are DNA methylation, modifications to chromatin, loss of imprinting and non-coding RNA. Epigenetic regulation of gene expression appears to have long-term effects and wide-ranging effects on health. Diet and environmental exposures may potentially alter the level and scope of epigenetic regulation, thus interesting developments in the study of epigenetics might explain correlations that researchers have found between lifestyle and risk of disease. Aberrant epigenetic patterns have been linked to a number of digestive diseases including Barrett's esophagus, cirrhosis, inflammatory bowel disease, and numerous gastrointestinal malignancies. In fact, many exciting discoveries about epigenetics in general have been made by studying diseases of the gastrointestinal tract and hepatobiliary tree. Epigenetic modifications of DNA in cancer and precancerous lesions offer hope and the promise of novel biomarkers for early cancer detection, prediction, prognosis, and response to treatment. Furthermore, reversal of epigenetic changes represents a potential target of novel therapeutic strategies and medication design. In the future, it is anticipated that innovative diagnostic tests, treatment regimens, and even lifestyle modifications will be based on epigenetic mechanisms and be incorporated into the practice of medicine.

Epigenetic regulation of matrix metalloproteinases and their collagen substrates in cancer

Our review covers the recent epigenetic data that are focused on matrix metalloproteinases (MMPs), their inhibitors (tissue inhibitors of MMPs; TIMPs) and collagen substrates. Twenty-four MMPs, four TIMPs and at least 28 collagen types are known in humans. The MMP activity regulates the functionality of multiple extracellular matrix proteins, cytokines, growth factors and cell signaling and adhesion receptors. Aberrantly enhanced MMP proteolysis affects multiple cell functions, including proliferation, migration and invasion. This aberrant MMP proteolysis is frequently recorded in cancer. Recent evidence, however, indicates that several MMPs function as tumor suppressors in cancer. Their inhibition could have pro-tumorigenic effects (making them anti-targets), counterbalancing the benefits of target inhibition and leading to adverse effects in cancer patients. The current epigenetic data suggest that there are distinct multi-layered epigenetic mechanisms that regulate MMPs, TIMPs and collagens. We show that in certain cancer types, epigenetic signatures of selected MMPs exhibit stem cell-like characteristics. Epigenetic mechanisms appear to play an especially important role in glioblastoma multiforme. Glioblastomas/gliomas synthesize de novo and then deposit collagens into the brain parenchyma. The collagen deposition, combined with an enhanced MMP activity in glioblastomas/gliomas, facilitates rapid invasion of tumor cells through the brain. It is tempting to hypothesize that the epigenetic mechanisms which control MMPs, TIMPs and collagens and, consequently, tumor cell invasion, represent promising drug targets and that in the near future these targets will be challenged pharmacologically.

Deregulation of microRNA expression occurs early and accumulates in early stages of HBV-associated multistep hepatocarcinogenesis

BACKGROUND & AIMS

Deregulation of microRNAs (miRNAs) plays an important role in human carcinogenesis. However, miRNA deregulation in the pre-malignant lesions and expression changes during multistep hepatocarcinogenesis remain elusive.

METHODS

In this study, we investigated the expression changes of seven cancer-related miRNAs during the early stages of HBV related hepatocarcinogenesis. miRNA was extracted from formalin fixed paraffin embedded (FFPE) dysplastic nodules (DN), small HCCs, and their corresponding non-tumorous livers. Expression changes of miRNAs were examined by real-time RT-qPCR.

RESULTS

We found that down-regulation of miR-145 and miR-199b and up-regulation of miR-224 were frequently observed in pre-malignant DNs and these changes persisted throughout HCC development. Restoration of miR-145 in both HepG2 and Hep3B HCC cells significantly inhibited cell proliferation and reduced cell migration and cell invasion. Furthermore, these inhibitory functions of miR-145 could be substantially reduced by an anti-miR-145 inhibitor.

CONCLUSIONS

Our results showed that miRNA deregulation was an early event and accumulated throughout the various steps of HBV-associated hepatocarcinogenesis. Our findings also suggest that miR-145 is a candidate tumor suppressive miRNA and may play an important role in HCC development.

The Role of miRNAs as Key Regulators in the Neoplastic Microenvironment

The neoplastic microenvironment has been recognized to play a critical role in the development of cancer. Although a large body of evidence has established the importance of the cancer microenvironment, the manners of crosstalk between it and the cancer cells still remains unclear. Emerging mechanisms of communication include microRNAs (miRNAs). miRNAs are small noncoding RNA molecules that are involved in the posttranscriptional regulation of mRNA. Both intracellular and circulating miRNAs are differentially expressed in cancer and some of these alterations have been correlated with clinical patient outcomes. The role of miRNAs in the tumor microenvironment has only recently become a focus of research, however. In this paper, we discuss the influence of miRNAs on the tumor microenvironment as it relates to cancer progression. We conclude that miRNAs are a critical component in understanding invasion and metastasis of cancer cells.

MiR-21 plays an important role in radiation induced carcinogenesis in BALB/c mice by directly targeting the tumor suppressor gene Big-h3

Dysregulation of certain microRNAs (miRNAs) in cancer can promote tumorigenesis, metastasis and invasion. However, the functions and targets of only a few mammalian miRNAs are known. In particular, the miRNAs that participates in radiation induced carcinogenesis and the miRNAs that target the tumor suppressor gene Big-h3 remain undefined. Here in this study, using a radiation induced thymic lymphoma model in BALB/c mice, we found that the tumor suppressor gene Big-h3 is down-regulated and miR-21 is up-regulated in radiation induced thymic lymphoma tissue samples. We also found inverse correlations between Big-h3 protein and miR-21 expression level among different tissue samples. Furthermore, our data indicated that miR-21 could directly target Big-h3 in a 3′UTR dependent manner. Finally, we found that miR-21 could be induced by TGFβ, and miR-21 has both positive and negative effects in regulating TGFβ signaling. We conclude that miR-21 participates in radiation induced carcinogenesis and it regulates TGFβ signaling.